Doc #89 — NZ Steel Glenbrook: Operational Continuity Without Imports

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RECOMMENDED ACTIONS

First week (Phase 1)

1. Verify graphite electrode inventory at Glenbrook — exact tonnage, grade, condition. This is a top-5 national strategic information priority. (Doc #1)
2. Verify refractory inventory — types, quantities, condition. Include both NZ Steel stocks and NZ distributor stocks (e.g., Calderys, Vesuvius/Foseco, RHI Magnesita agents in NZ).
3. Classify NZ Steel operational workforce as essential personnel. Prevent redeployment. Ensure families are supported to maintain workforce retention.
4. Secure the Glenbrook site — prevent unauthorised removal of any materials, particularly electrodes and refractories.
5. Verify Waikato North Head mining operation status and ensure continuity of ironsand supply.
6. Contact Waikato coal mines — verify supply continuity and plan allocation of coal to Glenbrook.
7. Check Tiwai Point smelter status — determine aluminium availability for coating operations.

First month (Phase 1)

8. Implement reduced production rate at Glenbrook, informed by electrode and refractory inventory data. Target 30–50% of nominal capacity as starting point, adjustable based on demand assessment and consumable stocks.
9. Begin engineering assessment of wire rod production capability — can the existing hot strip mill be adapted, or is a separate rod mill needed? What equipment modifications are required?
10. Inventory all graphite electrode stocks in NZ — including small stocks held by foundries, other EAF operators, and industrial suppliers.
11. Begin assessment of Soderberg electrode feasibility — NZ coal chemistry, tar production potential, electrode paste formulation.
12. Begin knowledge capture from NZ Steel process specialists — document the operational knowledge specific to Glenbrook’s ironsand process, particularly furnace operation, kiln management, and metallurgical control.
13. Assess EAF transformer condition — commission condition monitoring (dissolved gas analysis, thermal imaging) to estimate remaining service life.
14. Establish a steel allocation framework — prioritise steel distribution to essential recovery uses (agricultural equipment repair, water infrastructure, structural repair, gasifier construction).

First 3 months (Phase 1)

15. Initiate Soderberg electrode development program if assessment is positive — this is the highest-priority industrial development project for steelmaking continuity.
16. Initiate seawater magnesia feasibility study — identify suitable NZ coastal site, assess energy and lime requirements, design pilot plant.
17. Begin fireclay and dolomite refractory production development — identify NZ clay deposits suitable for basic refractories, establish small-scale production for lower-duty applications.
18. Complete wire rod adaptation engineering and begin implementation if feasible.
19. Establish steel product stockpiling program — build reserves of standard plate, coil, and (if available) rod in regional depots.
20. Cross-train additional personnel in critical Glenbrook roles — particularly EAF operation, kiln management, and metallurgical quality control. Aim for at least 2x redundancy in every critical role.

First year (Phase 1, entering Phase 2)

21. Achieve pilot-scale Soderberg electrode production if raw materials are available — even small-scale production extends EAF life.
22. Achieve pilot-scale NZ refractory production from domestic materials.
23. Wire rod production operational if adaptation is feasible.
24. Develop and test NZ-produced basic corrosion protection coatings (linseed oil-based paint, bitumen coatings) for bare steel roofing and structural applications.
25. Establish formal training program for Glenbrook operations — recruit and begin training the next generation of steelworkers specifically in Glenbrook’s unique process.
26. Coordinate with scrap recycling program (Doc #90) — integrate Glenbrook’s primary steel production with distributed scrap recycling to optimise NZ’s total steel supply.

Ongoing (Phase 2+)

27. Continue reduced-rate campaign production at Glenbrook, paced by consumable availability.
28. Scale up NZ refractory and electrode substitute production based on pilot experience.
29. Develop alternative melting technologies (induction furnace feasibility for medium-scale steel production) as a hedge against EAF consumable depletion.
30. If trade with Australia develops, prioritise import of graphite electrodes, refractories, rolling mill rolls, and heavy bearings — these are the items with highest value per tonne for NZ’s industrial recovery.
31. Long-term: Investigate titanium recovery from EAF slag — Glenbrook’s slag is rich in titanium dioxide, which is a potentially valuable material for pigment and (much more speculatively) metal production.

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Economic Justification

Person-years of workforce committed

Maintaining Glenbrook operations requires approximately 800–1,200 core operational workers on a continuous basis, plus the Waikato North Head mining crew — call it 1,000–1,300 people in total across both operations. At a productive career of 30–40 years, retaining this workforce preserves 30,000–52,000 person-years of future steelmaking capacity — capacity that cannot be rebuilt from scratch because the skills are specific to this plant and this process. That figure does not include the contractors, engineers, logistics staff, and downstream fabricators whose livelihoods and skills depend on the plant remaining viable.

The workforce composition spans high-specialisation roles: metallurgists who understand the specific behaviour of ironsand in Glenbrook’s kilns; EAF operators who know this furnace’s arc characteristics; rolling mill operators with feel for this particular mill’s dynamics; instrument technicians familiar with this plant’s control systems. These skills are not interchangeable with general manufacturing experience and cannot be rebuilt quickly. A metallurgist trained on conventional blast furnace ironmaking does not automatically know how to run Glenbrook’s unique titanomagnetite process. NZ Steel’s operating knowledge base represents decades of specialised learning that exists nowhere else in the world.

Protecting and retaining this workforce is therefore not only a matter of keeping a factory running. It is a matter of preserving a form of industrial knowledge that, once dispersed, will take a generation to reconstitute — if it can be reconstituted at all without the plant itself operating.

Cost of losing Glenbrook entirely

Glenbrook is NZ’s only primary steelmaking facility. There is no equivalent installation elsewhere in the country. If Glenbrook ceases production — whether through electrode depletion, workforce dispersal, or equipment failure — NZ loses:

• All domestic primary steel production. Scrap recycling (Doc #90) can supplement supply but cannot replace it. Scrap is finite, heterogeneous in chemistry, and progressively contaminated by tramp elements with each recycling cycle. Scrap steel is not a substitute for primary steel in applications requiring controlled chemistry.
• The ironsand processing capability. The rotary kilns, EAFs, and Kaldo converter are purpose-built for NZ’s unique titanomagnetite ore and cannot be replicated cheaply or quickly. Restarting a mothballed steelworks — or rebuilding one — is a multi-year, multi-billion-dollar industrial programme under favourable conditions. Under recovery conditions it may be impossible — the project requires heavy fabrication capability, specialised engineering, and years of commissioning, all of which assume a functioning industrial base that may no longer exist.
• The downstream fabrication base. Glenbrook’s flat products feed an entire fabrication economy: pipe and tube mills, roofing manufacturers, structural fabricators, engineering workshops. Without domestic steel coil and plate, these operations must import or cease. Under isolation, they cease.

The practical cost is that NZ’s ability to fabricate large infrastructure — water tanks, bridge girders, gasifier bodies (Doc #56), ship hull plate (Doc #138), agricultural equipment — becomes entirely dependent on scavenging existing steel stock from the built environment. The stock is substantial but finite. Once exhausted, there is no domestic replacement pathway.

Breakeven analysis

The arithmetic of keeping Glenbrook running favours operation even at reduced and expensive production rates. Consider the comparison:

Running Glenbrook at one-third capacity (approximately 200,000 tonnes/year):

• Electrode consumption: approximately 300–600 tonnes/year — manageable from existing stocks extended by conservation measures, with Soderberg development as a medium-term pathway
• Coal consumption: approximately 250,000–300,000 tonnes/year — entirely within domestic Waikato coalfield capacity
• Electricity: approximately 150–200 GWh/year — under 0.5% of national generation
• Workforce commitment: 1,000–1,300 workers as essential personnel
• Output: approximately 200,000 tonnes/year of flat-rolled steel — covering the lower end of estimated essential domestic needs (200,000–400,000 tonnes/year), with the balance supplied by scrap recycling (Doc #90) and existing steel stocks in the economy

Not running Glenbrook:

• Workforce disperses within months to other survival activities; operational knowledge begins to erode within the first year
• No domestic primary steel production of any kind
• Fabrication economy becomes entirely scrap-dependent; long products (wire rod, rebar) unavailable from any domestic source
• Recovery of agricultural fencing, irrigation infrastructure, building construction, and transport repair all become materially harder within 2–5 years as scrap stocks thin

The comparison is not close. The resource cost of running Glenbrook at reduced rate is modest — a manageable allocation of electricity, coal, and a protected workforce. The cost of losing it is the loss of NZ’s entire primary steel production capacity, likely permanently, because the conditions required to rebuild it (stable trade, large capital investment, multi-year lead time) may not recur for decades.

Opportunity cost of specialised workers

The 1,000–1,300 workers required to keep Glenbrook operational are not generalists. Their skills — kiln operation, EAF metallurgy, continuous casting, rolling mill operation — are among the most industrially specific in NZ. Redirecting them to farming, road repair, or other recovery activities loses not only their labour in those tasks (which other workers can provide) but their steel production capability (which no other workers can provide).

Put differently: NZ has many people who can dig drains. It has very few who can operate the Kaldo converter or manage a Soderberg electrode development programme. The opportunity cost of reassigning a steelworker to general labour is not one labourer equivalent — it is one steelworker, irreplaceable at short notice, whose absence closes a furnace bay that no one else can reopen.

This makes Glenbrook’s workforce one of the highest-priority protection categories in the national essential worker framework (Doc #8), comparable to hydro station engineers, coal miners, and telecommunications specialists.

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1. WHAT GLENBROOK IS

1.1 Location and ownership

NZ Steel’s Glenbrook mill is located at Mission Bush Road, Glenbrook, approximately 60 km south of Auckland and 10 km inland from the Manukau Harbour. The site covers approximately 160 hectares.² The plant has been operating since 1968, when the first iron was produced from ironsand using an experimental process.³

NZ Steel is a wholly owned subsidiary of BlueScope Steel Limited, an Australian-listed steelmaker. BlueScope acquired NZ Steel in 2002 as part of the BHP Steel demerger.⁴ Under recovery conditions, the practical significance of Australian ownership is limited — the plant, its equipment, and its workforce are all physically in NZ. The legal and financial relationship with BlueScope becomes moot; what matters is whether the plant can operate.

1.2 Workforce

NZ Steel employs approximately 1,500 people directly at Glenbrook and the Waikato North Head mining operation, with additional contractors involved in maintenance, logistics, and services.⁵ This workforce includes metallurgists, process engineers, kiln operators, furnace operators, rolling mill operators, electricians, instrument technicians, mechanical fitters, and laboratory staff. The collective knowledge held by this workforce — particularly the operators who understand the specific behaviour of Glenbrook’s unique ironsand-based process — is irreplaceable. No other steelworks in the world operates exactly this process, so the expertise cannot be sourced from overseas even under normal conditions.

Estimate: The core operational workforce — the people who must be present for the plant to run — is probably 800–1,200 of the total, with the remainder in administrative, commercial, and support roles that are less critical under emergency conditions. This estimate requires verification from NZ Steel’s operational management.

1.3 Current products

Glenbrook produces flat-rolled steel products:⁶

• Hot-rolled coil and plate: Structural steel for construction, pipe and tube making, general fabrication. This is the base product.
• Cold-rolled coil: Thinner, smoother finish, used for appliances, automotive panels, and further coating.
• ZINCALUME: Steel coated with a zinc-aluminium alloy (55% aluminium, 43.5% zinc, 1.5% silicon by weight), providing corrosion resistance. Requires imported zinc and aluminium.
• COLORSTEEL: ZINCALUME with a baked-on paint coating. NZ’s dominant roofing and cladding product. Requires ZINCALUME base plus imported paint.
• Galvanised steel: Zinc-coated steel for various applications. Requires imported zinc.
• Steel pipe and tube: Made from coil at downstream facilities.

What Glenbrook does NOT produce: Long products — structural sections (I-beams, channels, angles), reinforcing bar (rebar), wire rod, rail. NZ imports these products, primarily from Australia and Asia.⁷ This is a significant limitation for recovery: NZ’s most urgent steel needs (fencing wire, nails, rebar for concrete construction, structural shapes for building) are categories that Glenbrook does not currently make. Whether the rolling mill can be adapted is discussed in Section 7.

1.4 Capacity

Glenbrook’s nominal capacity is approximately 650,000 tonnes per year of steel slab.⁸ Actual production has typically been lower, varying with market conditions — roughly 500,000–620,000 tonnes in recent years.⁹ NZ’s total steel consumption is approximately 800,000–900,000 tonnes per year, with the balance imported.¹⁰

Under recovery conditions, NZ’s steel consumption will drop dramatically — construction slows, manufacturing contracts, export markets disappear. But certain categories of steel demand become more urgent: repair and maintenance of existing infrastructure, agricultural equipment, water systems, and eventually new construction adapted to changed conditions. Estimating post-event steel demand is highly uncertain, but a figure of 200,000–400,000 tonnes per year for essential domestic needs is a rough working estimate.¹¹ The lower bound assumes minimal new construction and a focus on repair; the upper bound assumes active infrastructure rebuilding and agricultural equipment fabrication. The actual figure depends heavily on the severity of the event and the pace of recovery. If Glenbrook can operate at even half its nominal capacity, it likely meets domestic demand. The constraint is not capacity but consumables.

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2. THE RAW MATERIAL: IRONSAND

2.1 What ironsand is

New Zealand’s ironsand is titanomagnetite — a black, magnetic, iron-titanium oxide mineral (Fe₃O₄ with Ti substitution) found in beach and dune sand deposits along the western coast of the North Island.¹² The iron content of NZ ironsand concentrate is approximately 57–60% iron by weight, with 7–8% titanium dioxide (TiO₂) and smaller amounts of vanadium, manganese, and other elements.¹³ The titanium content is both a feature and a constraint: it makes the ore unsuitable for conventional blast furnace processing (the titanium causes viscous slag problems) and is the reason Glenbrook uses its unique direct-reduction process.

2.2 Mining at Waikato North Head

NZ Steel mines ironsand at its Waikato North Head operation, located on the west coast approximately 30 km south of Port Waikato. The mine has been operating since the 1960s and extracts ironsand from coastal dune deposits using hydraulic mining (high-pressure water jets to slurry the sand) and magnetic separation to concentrate the titanomagnetite.¹⁴

The concentrated ironsand is transported to Glenbrook via an 18 km slurry pipeline — a suspension of iron sand in water, pumped to the plant.¹⁵ At Glenbrook, the slurry is dewatered and the concentrate is dried before entering the reduction process.

Key fact for recovery: The ironsand supply is entirely domestic. The mineral deposit at Waikato North Head is substantial — estimates of total ironsand resources along the NZ west coast range from hundreds of millions to billions of tonnes.¹⁶ The Waikato North Head deposit alone has decades of remaining reserves at current extraction rates. NZ Steel also holds mining rights at other North Island west coast sites. Ironsand availability is not a constraint on Glenbrook’s operation.

2.3 Mining dependencies

The mining operation itself has dependencies:

• Electricity: Hydraulic monitors (water cannons) and pumping systems are electrically powered. Consistent with baseline grid availability.
• Water: Large volumes of water are used for hydraulic mining and slurry transport. The operation draws from local freshwater sources. Under nuclear winter conditions, rainfall on the west coast is likely to remain adequate, though this is an uncertainty.
• Pipeline maintenance: The slurry pipeline is subject to abrasion (ironsand is highly abrasive) and requires periodic pipe replacement. The pipeline is steel-lined — replacement pipe could be produced by Glenbrook itself, creating a closed loop. Gaskets, pump seals, and valves are more problematic, as some are imported specialty items.
• Magnetic separation equipment: Uses permanent magnets and drum separators. Robust equipment with long life, but repair parts (particularly bearings and drive components) are imported.
• Diesel fuel: Some mobile equipment at the mine (bulldozers, loaders) uses diesel. Can potentially be converted to electric or wood gas (Doc #56) over time.

Assessment: The mining operation can continue under recovery conditions with the primary risk being pump and pipeline maintenance. Degraded capacity is probable as seals and wearing parts deplete, but total cessation is unlikely given the simplicity of the core operation (washing sand with water and separating with magnets).

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3. THE STEELMAKING PROCESS

3.1 Overview

Glenbrook’s process is unique and different from both conventional blast furnace steelmaking (used at most large steelworks worldwide) and conventional mini-mill electric arc furnace steelmaking (which uses scrap steel). Glenbrook’s process reduces ironsand directly, without a blast furnace, then melts the reduced iron in an EAF and refines it in an oxygen converter. The sequence:¹⁷

1. Ironsand preparation: Drying and sizing of ironsand concentrate
2. Reduction: Rotary kilns and multi-hearth furnaces reduce iron oxides to metallic iron using coal as the reductant
3. Melting: Electric arc furnaces melt the reduced iron
4. Refining: Basic oxygen steelmaking (Kaldo converter) refines the molten steel
5. Casting: Continuous slab caster produces steel slabs
6. Rolling: Hot strip mill and cold rolling mill produce finished products
7. Coating: Galvanizing and painting lines (ZINCALUME, COLORSTEEL)

3.2 Reduction: Rotary kilns and multi-hearth furnaces

The ironsand is fed into four rotary kilns — large, slightly inclined rotating cylinders approximately 65 m long and 4 m in diameter.¹⁸ Inside the kilns, coal (sub-bituminous coal, sourced from NZ mines — primarily the Huntly coalfield in the Waikato) is mixed with the ironsand, and as the kiln rotates at temperatures of approximately 1,000–1,100°C, the coal reduces the iron oxides in the ironsand to metallic iron. The product — called “direct reduced iron” or DRI — exits the kilns as a hot, partially metallised material containing approximately 75–85% metallic iron, with the remainder being unreduced oxides, titanium-bearing slag, and residual coal.¹⁹

The reduced material then passes through multi-hearth furnaces for further processing before being transferred hot to the electric arc furnaces.

Dependencies for reduction:

• Coal: NZ has domestic coal production, primarily from the Waikato coalfield (Huntly area) and West Coast (South Island). NZ Steel uses approximately 700,000–800,000 tonnes of coal per year, primarily sub-bituminous coal from the Waikato.²⁰ NZ’s total coal production was approximately 2.5–3 million tonnes per year as of recent years, so NZ Steel is a major consumer. Assumption: Domestic coal supply continues under recovery conditions. The Huntly coalfield is close to Glenbrook and transport is by road and rail — both assumed operational under baseline conditions. Coal is not an import dependency, though NZ Steel has historically supplemented with some imported coal.
• Kiln refractories: The kilns are lined with refractory brick and cement to withstand operating temperatures. Kiln refractories are a mix of domestic and imported materials (see Section 5).
• Kiln shell maintenance: The steel shells of the kilns are subject to high-temperature creep and fatigue. Repair welding and replacement sections can be fabricated from Glenbrook’s own steel, but monitoring and alignment require specialist knowledge and some imported instrumentation.

3.3 Melting: Electric arc furnaces

The hot, reduced ironsand is charged into electric arc furnaces (EAFs) — the heart of the steelmaking process. Glenbrook operates two EAFs.²¹ In these furnaces, powerful electric arcs between graphite electrodes and the metallic charge generate temperatures exceeding 1,600°C, melting the reduced iron into liquid metal. Slag — primarily titanium oxides — floats on top and is tapped off separately.

The EAF is Glenbrook’s most energy-intensive and consumable-dependent process step:

• Electricity: Each EAF draws approximately 30–50 MW during operation.²² Glenbrook’s total electricity consumption is approximately 400–500 GWh per year, making it one of NZ’s largest single electricity consumers — roughly 1% of national generation.²³ Under baseline grid conditions, this electricity is available from NZ’s renewable generation. The question is whether NZ’s grid operators would allocate this much generation to steelmaking under emergency conditions. The answer is almost certainly yes — steel production is a recovery priority — but the decision involves balancing demand across all essential loads.
• Graphite electrodes: This is the critical consumable. See Section 4.
• Refractory linings: The EAF is lined with magnesite (magnesia-carbon) refractory brick that is consumed during steelmaking — chemically and physically eroded by molten steel, slag, and the arc itself. Lining life is typically measured in hundreds of heats before relining is required. These refractories are primarily imported. See Section 5.

3.4 Refining: Basic oxygen steelmaking

After EAF melting, the liquid steel is transferred to a Kaldo-type basic oxygen converter (a rotary oxygen steelmaking vessel), where oxygen is blown through the melt to reduce carbon, phosphorus, and sulfur to specified levels.²⁴ This process refines the steel to the desired chemistry.

Dependencies:

• Oxygen: Produced on-site by an air separation unit (ASU) that liquefies and distils air to produce oxygen and nitrogen. The ASU is electrically powered and requires maintenance of compressors, heat exchangers, and instrumentation. The ASU itself is imported equipment, but the “raw material” is air. Spare parts and maintenance are the constraint.
• Fluxes: Lime (calcium oxide) and dolomite are used as fluxes to form slag that absorbs impurities. NZ has domestic limestone and dolomite — lime is produced at several NZ kilns, including in the Waikato.²⁵ This is not an import dependency.
• Alloying elements: Steel chemistry is adjusted by adding alloys — manganese, silicon, sometimes chromium, nickel, or other elements. NZ has limited domestic sources for these. Manganese ore exists in small deposits but is not commercially mined.²⁶ Silicon can potentially be produced from quartz sand using electric arc reduction (a major project in itself). Most alloying additions are imported. Without them, Glenbrook produces a basic carbon steel — functional for most structural and general purposes but not speciality grades.

3.5 Casting and rolling

Liquid steel from the refining converter is continuously cast into slabs approximately 200 mm thick and up to 1,550 mm wide using a continuous slab caster.²⁷ The slabs are then rolled:

• Hot strip mill: Reheats slabs to approximately 1,200°C and rolls them through a series of roughing and finishing stands to produce hot-rolled coil and plate in thicknesses from approximately 1.5 mm to 12 mm. The hot strip mill is a complex piece of equipment with many rolls, bearings, hydraulic systems, and instrumentation.
• Cold rolling mill: Further reduces hot-rolled coil to thinner gauges (down to approximately 0.3 mm) and improves surface finish. Used for products requiring a smoother surface (tin plate base, appliance panels).

Dependencies for casting and rolling:

• Rolls: The work rolls in the rolling mills are high-performance items made from special alloy steels or cast iron. They wear with use and must be periodically reground and eventually replaced. Rolls are imported — NZ has no roll manufacturing capability. Roll stocks and regrinding capacity are significant constraints on long-term rolling mill operation.
• Bearings and hydraulics: Rolling mills use heavy-duty bearings and hydraulic systems that require periodic maintenance and replacement. Bearings are imported (Doc #91). Hydraulic fluids are petroleum-based and imported, though some NZ-based alternatives may be feasible for lower-performance applications.
• Mould powder (continuous casting): Specialised flux powders are used in the continuous caster to lubricate the mould, absorb inclusions, and control heat transfer. These are imported formulated products. Substitution with locally available flux materials (limestone-based) is theoretically possible but would require significant metallurgical development and would likely produce inferior surface quality — increased surface defects, higher inclusion counts, and potentially higher rejection rates. For structural and general fabrication uses, this degradation is tolerable; for applications requiring clean surface finish (e.g., roofing sheet), it may require additional surface grinding or acceptance of cosmetic defects.

3.6 Coating (ZINCALUME, COLORSTEEL)

The coating lines apply metallic and paint coatings to cold-rolled coil:

• Galvanising/ZINCALUME: Coil passes through a bath of molten zinc-aluminium alloy. NZ has no domestic zinc production, and its only aluminium production (Tiwai Point smelter) depends on imported alumina — see Section 6.²⁸ When zinc and aluminium stocks are exhausted, the coating lines stop. This is discussed in Section 6.
• COLORSTEEL: ZINCALUME-coated coil is painted with baked-on polyester or other coatings. The paints are imported formulated products.

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4. CRITICAL CONSUMABLE #1: GRAPHITE ELECTRODES

4.1 What they are and why they matter

Electric arc furnaces operate by passing enormous electrical current through graphite electrodes — cylindrical rods typically 400–700 mm in diameter and several metres long — to create an electric arc between the electrode tips and the metallic charge. The arc temperature exceeds 3,000°C, melting the steel.²⁹

Graphite electrodes are consumed during steelmaking. They are oxidised by the furnace atmosphere, eroded by the arc, and mechanically broken by thermal shock and contact with the charge. A typical EAF consumes approximately 1.5–3.0 kg of graphite electrode per tonne of steel produced, though this varies with furnace design, operating practice, and electrode quality.³⁰ For ultra-high-power (UHP) electrodes used in modern EAFs, consumption can be at the lower end of this range; for regular-power electrodes, it tends toward the higher end.

At Glenbrook’s capacity of ~650,000 tonnes/year, annual electrode consumption is approximately 1,000–2,000 tonnes of graphite electrodes. This is a substantial quantity of a product that NZ does not produce and has no raw materials to produce.

4.2 Where electrodes come from

Graphite electrodes are manufactured from petroleum coke (a residue of oil refining) or needle coke (a specialised high-quality coke), mixed with coal tar pitch binder, extruded, baked at approximately 800–1,000°C, and then graphitised at approximately 2,500–3,000°C in electric resistance furnaces (Acheson furnaces).³¹ The graphitisation process converts amorphous carbon to crystalline graphite, giving the electrode the electrical conductivity and thermal properties required for arc furnace operation.

Major manufacturers include Graftech (USA), Showa Denko (Japan), SGL Carbon (Germany), and several Chinese producers. No graphite electrode manufacturing exists in NZ or Australia. The nearest production would be in East Asia.³²

4.3 NZ electrode stocks

NZ Steel maintains an inventory of graphite electrodes at Glenbrook. The size of this inventory is commercially sensitive and not publicly available, but steelworks typically hold weeks to a few months of consumption as buffer stock.³³

Estimate: If Glenbrook holds 2–4 months of electrode stock at normal production rates, that represents approximately 170–670 tonnes of electrodes. This estimate has wide uncertainty and must be verified directly with NZ Steel management. The actual figure is one of the most important numbers in NZ’s industrial recovery planning.

4.4 Extending electrode life

Several strategies can extend the available electrode supply:

• Reduced production rate: Operating the EAF at lower throughput reduces electrode consumption roughly proportionally. If Glenbrook produces 200,000 tonnes per year instead of 650,000, electrode consumption drops to approximately 300–600 tonnes per year, extending the same stock by roughly 2.5–3x (the relationship is not strictly linear because some electrode oxidation occurs during idle periods and handling).
• Improved electrode management: Careful handling reduces breakage (a significant source of electrode loss). Controlling furnace atmosphere to minimise oxidation extends electrode tip life. Operating at lower power settings reduces thermal stress but also reduces melt rate.
• Electrode recycling: Broken electrode stubs can be rejoined using electrode paste or threaded nipple connections — this is standard practice but recovering more of each electrode before discarding it extends the supply.
• Soderberg (self-baking) electrodes: An alternative to pre-baked graphite electrodes. Soderberg electrodes are columns of steel casing filled with electrode paste (a mix of carbon materials and binder), which bakes in place as it descends into the furnace. Soderberg electrodes were historically used in submerged-arc furnaces and older EAF designs. They use less-refined carbon materials than graphite electrodes and could potentially be manufactured in NZ if suitable carbon sources (petroleum coke, anthracite coal, coal tar pitch) are available.³⁴ NZ has limited petroleum refining (Marsden Point was NZ’s only refinery; it ceased refining operations in 2022 and converted to an import terminal)³⁵, so petroleum coke availability is uncertain — residual stocks from the refining era may exist but have not been inventoried for this purpose. Coal tar could potentially be produced from NZ coal through pyrolysis (heating coal in the absence of air to drive off volatile compounds), but this requires building pyrolysis retorts, collecting and processing the tar, and formulating it into electrode paste — a multi-step development programme requiring chemistry, mechanical engineering, and months of trial-and-error testing. NZ has no current coal tar production infrastructure. This is a potential pathway but requires significant development — it is not an existing capability, and the timeline from first research to usable electrode paste is realistically 6–18 months under favourable conditions.

4.5 Electrode depletion timeline

Honest assessment: This is one of the most critical uncertainties for Glenbrook’s continued operation. If the existing electrode stock provides 2–4 months at full capacity, it provides 6–12 months at one-third capacity, and possibly 12–24 months with aggressive conservation measures and reduced production. After that, without a new electrode source (Soderberg development, trade with Australia or Asia, or some other solution), the electric arc furnaces cannot operate.

If the EAFs cannot operate, Glenbrook cannot make steel from ironsand. The only remaining domestic steelmaking pathway would be scrap steel recycling in small electric arc furnaces using available electrode stocks (Doc #90), or — far more speculatively — developing alternative melting technologies (induction furnaces, which do not use graphite electrodes but have their own limitations at the scale needed).

This is the single most important constraint on NZ’s steel production continuity. The electrode stockpile at Glenbrook should be treated as a strategic national resource from Day 1.

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5. CRITICAL CONSUMABLE #2: REFRACTORIES

5.1 What refractories are

Refractories are heat-resistant materials that line the inside of furnaces, ladles, converters, and other equipment in contact with molten metal and slag. They protect the steel shell from temperatures exceeding 1,600°C and from chemical attack by molten steel and slag. Refractories are consumed during operation — chemically dissolved, thermally spalled, and mechanically eroded — and must be periodically replaced (relined).³⁶

5.2 Refractory types used at Glenbrook

Different parts of the process use different refractories:

• Rotary kilns: Alumina-silica brick, chrome-magnesite, or high-alumina castables. Operating temperature ~1,100°C. Kiln lining life is typically 1–3 years depending on the zone.³⁷
• Electric arc furnaces: Magnesia-carbon (MgO-C) brick in the walls and bank, and rammed magnesia or dolomite in the hearth. EAF linings are heavily consumed and relined frequently — wall lining life may be only 200–600 heats (a few months of operation).³⁸
• Ladles and converters: Magnesia-carbon, dolomite, or high-alumina linings. Ladle linings last hundreds of heats before relining.
• Continuous caster tundish: Alumina-based or magnesia-based spray linings and dams. Consumed every few operating sequences.

5.3 NZ refractory materials

NZ has some domestic refractory raw materials, but not the full range:

• Fireclay and silica sand: NZ has deposits of fireclay (e.g., in the Waikato and Bay of Plenty regions) and silica sand suitable for basic refractory applications.³⁹ These can be used for lower-temperature applications (below ~1,500°C) — adequate for kiln linings but not for the most severe EAF duties, where temperatures exceed 1,600°C and chemical attack from molten steel and titanium-rich slag requires magnesia-based refractories. Fireclay refractories in these high-duty positions would fail in hours to days rather than the weeks to months achieved by imported MgO-C brick.
• Dolomite: NZ has dolomite deposits. Calcined dolomite can serve as a basic refractory for some converter and ladle applications. It is less durable than magnesite-carbon refractories but is functional.⁴⁰
• Magnesite (magnesia): The primary raw material for high-performance basic refractories. NZ has limited known magnesite deposits. Some magnesium-bearing minerals exist (olivine, serpentine) from which magnesia could potentially be extracted, but this is not current practice.⁴¹ Magnesia could also be extracted from seawater (NZ has abundant seawater) via precipitation with lime — this is a known industrial process used elsewhere but not currently practised in NZ.
• Graphite (for MgO-C bricks): MgO-C refractories contain 10–25% graphite flake. NZ has no known commercial graphite deposits.⁴²
• Chrome ore: Used in chrome-magnesite refractories. Not available in NZ.

5.4 Refractory substitution strategy

Without imported refractories, Glenbrook would need to adopt a tiered approach:

1. Existing stocks first: NZ Steel will hold refractory inventory at the plant. Extend this through careful furnace management — lower operating temperatures where possible, reduced campaign lengths rather than running linings to failure, and recycling of used refractory material (crushed used brick can be incorporated into new mixes as aggregate).
2. NZ-produced basic refractories: Develop production of calcined dolomite and silica-based refractories for lower-duty applications (kiln linings, ladle backup linings, tundish linings). These materials exist in NZ and the processing (calcining, crushing, pressing, firing) is within NZ’s industrial capability, though it would need to be established.
3. Seawater magnesia: Develop magnesia-from-seawater production to substitute for imported magnesite. This is a well-understood industrial process but requires significant lime and energy inputs. A facility would take months to years to establish.⁴³
4. Accept lower lining life: NZ-produced refractories will likely have shorter service life than imported high-performance products — perhaps 30–60% of the campaign life achieved by imported MgO-C brick, meaning relining every 100–200 heats instead of 200–600 heats. This means more frequent relining, which consumes more refractory material and reduces furnace availability (each reline takes days of downtime). This is a manageable degradation, not a show-stopper, as long as the refractory supply keeps pace with the higher consumption rate.

Assessment: Refractories are a serious constraint but not an absolute barrier. NZ has domestic materials for basic refractories and a plausible pathway (seawater magnesia) to produce higher-grade materials. The development timeline is months to years, not decades. Refractory depletion is less immediately critical than electrode depletion because lining stocks tend to be larger relative to consumption and because NZ-based substitution pathways exist.

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6. CRITICAL CONSUMABLE #3: COATING MATERIALS

6.1 Zinc

NZ has no zinc mining or smelting. All zinc used in NZ is imported — primarily from Australia (where Nyrstar and others operate zinc smelters).⁴⁴ NZ Steel’s galvanising and ZINCALUME coating operations consume an estimated 3,000–5,000 tonnes of zinc per year.⁴⁵

When zinc stocks are exhausted — which, depending on existing inventory at Glenbrook and NZ zinc distributors, could be weeks to months after trade cessation — all galvanised and ZINCALUME-coated steel production stops.

6.2 Aluminium

NZ had aluminium production at the Tiwai Point smelter (NZAS) near Bluff, operated by Rio Tinto. However, the smelter’s long-term future has been uncertain, and regardless of its status, it produces aluminium from imported alumina (refined from Australian bauxite), not from NZ raw materials.⁴⁶ If Tiwai Point is operating at the time of the event and has alumina stocks, it can produce aluminium for some period. If not, NZ has no aluminium production.

6.3 Paint

COLORSTEEL paints are imported formulated products. NZ has some paint manufacturing capability (Resene, Dulux NZ) but the specific coil-coating paints are specialised formulations. Substitution with NZ-manufactured paints is plausible for some applications but requires reformulation and testing.

6.4 Implications: The end of coated steel

Fact: Without imports, Glenbrook cannot produce ZINCALUME or COLORSTEEL. This is NZ’s dominant roofing and cladding material — most NZ buildings constructed in the last 40 years use COLORSTEEL roofing.⁴⁷

Consequence: New construction and repair will need to use bare (uncoated) steel, which corrodes in NZ’s maritime and humid climate. Alternative corrosion protection strategies:

• Paint from NZ production: NZ paint manufacturers (Resene, Dulux NZ) can produce basic protective paints from NZ-available materials (linseed oil-based paints, for example), though these require reapplication every 3–7 years compared to 15–25+ years for factory-applied coil coatings, and provide less consistent coverage than the controlled factory process.
• Bitumen/tar coatings: NZ has bitumen from petroleum stocks and could potentially produce coal tar. These provide basic corrosion protection.
• Accept shorter service life: Bare or poorly coated steel in NZ conditions might last 5–15 years before requiring replacement (depending on thickness, exposure zone, and whether basic paint is applied), versus 20–50+ years for COLORSTEEL.⁴⁸ This is a significant but manageable degradation — it means more frequent replacement, not immediate failure. The maintenance burden roughly triples compared to modern coated products.
• Alternative roofing materials: Timber (abundant in NZ), concrete tile, clay tile (NZ has clay). Steel roofing is convenient but not the only option.

This is a quality-of-life and maintenance burden issue, not a survival issue. NZ built with timber, tile, and corrugated iron (an older galvanised product) for over a century before COLORSTEEL existed.

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7. PRODUCT ADAPTATION: WHAT NZ ACTUALLY NEEDS

7.1 Recovery steel demand

Under recovery conditions, NZ’s steel priorities shift dramatically from the pre-war product mix. The current Glenbrook product range (flat-rolled coil and plate for construction and manufacturing) partially aligns with recovery needs, but significant gaps exist:

Products Glenbrook CAN produce (flat products):

• Plate for fabrication: tanks, gasifier bodies (Doc #56), ship repairs, structural platforms
• Coil for cold-forming: pipe, tube, profiles (formed from flat strip using bending and welding)
• Sheet for roofing: Bare or painted flat sheet as a COLORSTEEL substitute
• Slit coil for light structural applications

Products Glenbrook CANNOT currently produce (long products):

• Wire rod — needed for wire drawing (Doc #105), nails, fencing wire, springs, rope
• Reinforcing bar (rebar) — needed for concrete construction
• Structural sections (I-beams, channels, angles) — needed for building and bridge construction
• Rail — needed if railway maintenance requires new rail sections

7.2 Can Glenbrook adapt?

Converting from flat to long product production is a major undertaking:

Wire rod and rebar: These are typically produced on a rod/bar mill — a different type of rolling mill that rolls round or deformed bar from billets (square-section cast steel, not slabs). Glenbrook’s continuous caster produces slabs. To make wire rod or rebar, Glenbrook would need either:

• A new billet caster (significant engineering project, but within NZ’s fabrication capability given sufficient time and skilled labour)
• Reheating slabs and rolling them through a roughing mill to produce blooms/billets, then further rolling to rod/bar. The existing hot strip mill is designed for flat rolling and would require modification or supplementation.

Estimate: Adapting Glenbrook to produce even basic wire rod or rebar would be a major engineering project taking 6–18 months with significant workforce effort.⁴⁹ The lower end assumes a billet-from-slab approach using modified existing equipment; the upper end assumes new billet caster construction. It is feasible but not trivial. Alternative approaches include small-scale wire rod production from scrap in independent facilities (Doc #106).

Structural sections: Require a section mill (also called a structural mill) with shaped rolls. Not convertible from flat rolling equipment without new roll sets and significant mill modification. More realistically, structural shapes in recovery NZ would be fabricated from plate — welded I-beams, built-up columns, plate girders. This is less efficient than rolled sections but entirely functional and within NZ’s existing fabrication capability. Fabricated structural members are already used for large and custom structures in normal practice.

7.3 Prioritised product strategy

A realistic product strategy for Glenbrook under recovery conditions:

1. Continue flat product production — hot-rolled coil and plate. This serves the broadest range of fabrication needs and is what the plant is set up to do.
2. Prioritise plate over thin coil — heavy fabrication (tanks, gasifier bodies, structural platforms, ship hull plate) is more immediately useful than thin sheet for appliance panels.
3. Produce roofing sheet — bare or NZ-painted flat sheet to substitute for COLORSTEEL in repair and new construction.
4. Develop wire rod capability — this is the most valuable product adaptation because wire (for fencing, nails, reinforcing tie wire, and dozens of other uses) is one of NZ’s most critical recovery needs. This should be a Phase 1 engineering priority.
5. Defer structural section rolling — fabricate structural shapes from plate using existing workshop and welding capability (Doc #91, Doc #94).

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8. ENERGY REQUIREMENTS

8.1 Electricity

Glenbrook consumes approximately 400–500 GWh of electricity per year at normal production rates.⁵⁰ NZ’s total electricity generation is approximately 42,000–44,000 GWh per year.⁵¹ Glenbrook therefore represents roughly 1–1.2% of national generation.

Under recovery conditions with reduced production (say 200,000–300,000 tonnes/year), electricity consumption would drop roughly proportionally to perhaps 150–250 GWh/year — under 0.7% of national generation. This is a significant load but well within the capacity of NZ’s grid, particularly as many other industrial loads will have ceased.

Assessment: Electricity is not a constraint on Glenbrook’s operation. NZ’s renewable grid can supply it. The grid allocation decision is a policy matter, not a technical one — and steel production will be near the top of any rational priority list.

8.2 Coal

Glenbrook uses approximately 700,000–800,000 tonnes of coal per year, primarily for the reduction process in the rotary kilns.⁵² This is NZ’s largest single coal consumer.

NZ produces approximately 2.5–3 million tonnes of coal per year from the Waikato (sub-bituminous) and West Coast (bituminous and sub-bituminous) coalfields.⁵³ At reduced Glenbrook production rates, coal consumption might drop to 250,000–400,000 tonnes per year.

Coal supply chain: The Waikato coalfield (Huntly area, operated primarily by Bathurst Resources and others) is approximately 80 km from Glenbrook by road and rail. West Coast coal would need to be transported by rail and ferry or coastal shipping. Under recovery conditions, Waikato coal is the preferred supply due to proximity.

Assessment: Domestic coal supply is adequate for reduced-rate Glenbrook operation. The constraint is not coal volume but mining continuity — coal mines require their own labour, equipment maintenance, and consumables. Mining equipment spare parts, tires (Doc #33), and explosives for blasting are all imported consumables with finite stocks. Coal mining continuity must be managed in parallel with Glenbrook’s other dependencies.

8.3 Natural gas

Glenbrook uses natural gas for some heating applications (slab reheating furnace, annealing). NZ has domestic natural gas production from the Taranaki Basin (Pohokura, Maui, Mangahewa, and other fields).⁵⁴ Gas supply to Glenbrook is via the North Island gas pipeline network. Natural gas availability depends on the continued operation of Taranaki gas fields and the pipeline network — both assumed operational under baseline conditions but subject to gradual degradation of wellhead equipment and compressor stations.

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9. SPARE PARTS AND EQUIPMENT MAINTENANCE

9.1 The maintenance challenge

Glenbrook is a complex industrial plant with thousands of individual pieces of equipment — motors, gearboxes, hydraulic systems, instrumentation, conveyors, cranes, cooling systems, pollution control equipment. Under normal conditions, spare parts are ordered from global suppliers, typically with lead times of weeks to months. Under recovery conditions, this supply chain ceases entirely.

9.2 What Glenbrook can maintain itself

NZ Steel has an on-site maintenance workshop with significant machining, welding, and fabrication capability.⁵⁵ Additionally, NZ’s broader engineering workshop network (Doc #91) can support Glenbrook maintenance. Parts that can be produced or repaired domestically:

• Structural steel components: Platforms, chutes, brackets, guards — fabricated from Glenbrook’s own steel
• Shaft repairs: Worn shafts can be built up by welding and re-machined (Doc #91)
• Bearing housings and simple castings: Can be produced by NZ foundries (Doc #93) and machined
• Pipe and fittings: Can be fabricated from Glenbrook steel
• Electrical rewinding: NZ has motor rewinding capability for standard electric motors

9.3 What Glenbrook cannot maintain

• Rolling mill rolls: High-alloy or cast-iron rolls with specific metallurgical properties. NZ may be able to produce basic rolls through its foundry capability (Doc #93), but roll quality directly affects product quality and mill performance. This is a significant long-term constraint.
• Precision bearings for critical applications: Heavy-duty bearings in rolling mill housings, furnace rolls, and caster equipment are precision-manufactured items. NZ cannot produce them (Doc #91). Existing bearing stocks must be managed carefully.
• Instrumentation and control systems: Glenbrook uses modern process control systems (PLCs, SCADA, sensors) for furnace control, rolling mill automation, and quality monitoring. These are imported electronics with finite life. As controllers fail, operations must progressively revert to manual control — which is possible (steel was made before PLCs existed) but requires re-learning manual operating practices and results in less consistent product quality.
• Transformer and electrical switchgear: High-voltage equipment for the EAF power supply is specialised and largely irreplaceable. Failure of the EAF transformer would shut down that furnace until repair or replacement is achieved.
• Oxygen plant (ASU) components: Compressors, cold box heat exchangers, and control systems for the air separation unit are specialised imported equipment. The ASU is essential for the oxygen steelmaking step.

9.4 Equipment failure timeline

Estimate: With careful maintenance and reduced production rates, most major Glenbrook equipment has an expected remaining service life of years to decades. The items most likely to cause forced shutdowns are:

• Graphite electrode depletion (months — see Section 4)
• EAF transformer failure (unpredictable — could be years or decades)
• ASU compressor failure (years, with careful operation)
• Rolling mill bearing or roll failure (years, dependent on stock management)
• Process control system degradation (progressive over years)

The strategy must be to extend the life of all equipment through reduced production rates, meticulous maintenance, and strategic allocation of spare parts from the national inventory (Doc #1).

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10. COMPARISON WITH ALTERNATIVES

10.1 Scrap steel recycling (Doc #90)

NZ has a large accumulated stock of scrap steel — in buildings, vehicles, industrial equipment, farm machinery, and dedicated scrap yards. Recycling scrap in smaller electric arc furnaces is a well-established global practice and could supplement or eventually replace Glenbrook’s ironsand-based production as Glenbrook’s consumables deplete.

Advantages of scrap recycling:

• Scrap steel is already reduced metal — no kilns or coal needed
• Smaller EAFs consume fewer graphite electrodes per tonne (scrap melts more easily than DRI)
• Can be distributed across multiple smaller facilities, reducing single-point-of-failure risk
• Energy consumption per tonne is lower than ironsand-based production

Disadvantages:

• Still requires graphite electrodes (unless induction furnaces are used — see Doc #106)
• Scrap supply is finite and of variable quality
• Scrap contains contaminants (copper, tin, zinc from coated products) that accumulate and degrade steel quality over repeated recycling — the “tramp element” problem⁵⁶
• Product range from scrap mini-mills is typically limited to long products (rebar, rod, sections) unless combined with continuous casting and rolling

Assessment: Scrap recycling is complementary to Glenbrook, not a replacement. Glenbrook produces clean, primary steel from virgin ore — essential for applications requiring controlled chemistry. Scrap recycling produces lower-grade steel suitable for construction and general fabrication. NZ needs both.

10.2 Small-scale electric arc furnaces (Doc #106)

Doc #106 addresses the possibility of smaller-scale EAF installations — potentially using induction furnaces rather than arc furnaces — for distributed steelmaking from scrap. Induction furnaces do not use graphite electrodes (they use water-cooled copper coils and electromagnetic induction to heat the charge), which removes the electrode constraint. However, induction furnaces at steelmaking scale require substantial electrical infrastructure, large copper coils (copper is limited in NZ), and sophisticated power electronics (imported, finite).

10.3 Imported steel via trade

If maritime trade with Australia is established (Doc #138), Australian steel could supplement or replace NZ production. Australia has major steelworks (BlueScope Port Kembla, Liberty Primary Steel Whyalla) and, if these survive and Australia’s coal and iron ore supply remains functional, could be a trade partner. However, this document does not assume trade will materialise on any specific timeline — it plans for NZ self-sufficiency as the base case.

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11. REDUCED-CAPACITY OPERATING STRATEGY

11.1 The case for producing less

Under recovery conditions, Glenbrook should operate at reduced capacity — perhaps 150,000–300,000 tonnes per year rather than its nominal 650,000.⁵⁷ The reasons:

• Consumable conservation: Lower production extends graphite electrode, refractory, and spare parts stocks roughly proportionally. If electrode stock provides 6 months at full rate, it provides roughly 15–20 months at one-third rate (not a strict 3x because some electrode consumption — oxidation, breakage during handling — occurs independent of production rate). This buys time for developing alternatives (Soderberg electrodes, seawater magnesia, trade).
• Demand is lower: NZ’s post-event steel demand is likely 200,000–400,000 tonnes per year (a rough estimate), much of which can be met by existing steel stocks in the economy and scrap recycling.
• Workforce concentration: Running at lower throughput allows the workforce to focus on maintenance, adaptation (wire rod development), and training — transferring knowledge of this unique process to a new generation.
• Equipment longevity: Lower production means less wear on irreplaceable equipment (rolls, bearings, refractories).

11.2 Operating schedule

Rather than continuous operation at low rate, Glenbrook might operate in campaigns — running the EAF and rolling mill for defined periods, then shutting down for maintenance, training, and preparation. Campaign operation reduces the total number of EAF heats (and therefore electrode consumption) while allowing concentrated production runs that are operationally efficient.

Example schedule: Two months of production (producing ~25,000–50,000 tonnes), one month of maintenance and preparation. This produces 200,000–400,000 tonnes per year while giving structured time for maintenance, training, and adaptation work.

11.3 Stockpiling strategy

During production campaigns, steel should be stockpiled in standardised forms that serve the broadest range of recovery needs:

• Heavy plate (6–12 mm) for fabrication
• Medium plate (3–6 mm) for general use
• Light coil (1.5–3 mm) for roofing and forming
• If wire rod capability is developed: wire rod for drawing into wire (Doc #105)

Steel slab can also be stockpiled as an intermediate product and rolled later as specific needs arise. Slab is stable in storage (surface rust is superficial and does not affect usability) and can be stored outdoors.

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12. URGENCY CALIBRATION

12.1 Why this matters immediately

Glenbrook is operating now. The steelmaking process is running, the workforce is in place, the knowledge is embodied in living people and functioning systems. The urgent task is not to build something new but to preserve what exists.

What is actually time-sensitive:

• Electrode inventory verification: The government must know, within the first week, how many graphite electrodes are at Glenbrook and in NZ distributor stocks (there may be small quantities held by foundries and other EAF users). This number determines how long primary steelmaking can continue.
• Workforce classification: NZ Steel’s operational workforce — particularly kiln operators, furnace operators, rolling mill operators, and process metallurgists — must be classified as essential workers and protected from redeployment to other tasks. This knowledge cannot be replaced.
• Production rate decision: A conscious decision about reduced production rate should be made within the first month, informed by electrode and refractory inventory data.

What can wait weeks to months:

• Wire rod capability development (important but a multi-month project regardless)
• Seawater magnesia development (longer-term refractory substitution)
• Soderberg electrode research (important but requires months of development)

What can wait months to years:

• Billet caster construction
• Alternative melting technology assessment (induction furnaces)
• Full product range diversification

12.2 Cost of delay

Every day of full-rate production before the decision to reduce output consumes approximately 3–6 tonnes of irreplaceable graphite electrodes. Over a month, that is 90–180 tonnes — potentially 10–15% of the total stockpile. The cost of a one-month delay in implementing reduced production is measurable in months of lost future steelmaking capacity.

This is one of the few areas in the Recovery Library where the urgency rhetoric is justified by the arithmetic.

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CRITICAL UNCERTAINTIES

Uncertainty	Impact if Wrong	Resolution Method
Graphite electrode inventory at Glenbrook	Determines months/years of EAF operation. If less than estimated, steelmaking window is shorter.	Direct verification with NZ Steel management — first week priority
Refractory inventory at Glenbrook	Determines furnace relining capability. If less than estimated, production stops sooner.	Direct verification with NZ Steel management
Feasibility of Soderberg electrode production in NZ	If feasible, extends EAF life indefinitely. If not, electrode depletion is an absolute constraint.	Engineering assessment using NZ coal and coke resources — first 3 months
Seawater magnesia production viability	If viable, solves the refractory supply problem. If not, refractory depletion limits furnace availability.	Process development — 6–12 months
Rolling mill adaptability for wire rod	If achievable, fills NZ’s most critical steel product gap. If not, wire rod must come from alternative sources.	Engineering assessment by NZ Steel and external engineers — first 3 months
EAF transformer remaining life	Failure shuts down the furnace. No NZ repair capability for this scale of transformer.	Condition assessment — first month
Coal mine continuity	If Waikato coal supply is interrupted, the reduction process stops.	Verify mining operation continuity and supply chain — first month
Post-event NZ steel demand	If higher than estimated, Glenbrook must produce more (consuming consumables faster). If lower, conservation is easier.	Demand assessment based on census of construction, infrastructure, and manufacturing needs
NZ Steel workforce retention	If key personnel leave (to farms, to family elsewhere), operational knowledge is lost.	Essential worker classification — first week
Tiwai Point aluminium smelter status	If operating with alumina stocks, some aluminium is available for ZINCALUME. If not, coating production ends sooner.	Verify smelter status — first week

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CROSS-REFERENCES

• Doc #1 — National Emergency Stockpile Strategy (electrode and refractory requisition, steel allocation)
• Doc #8 — National Skills and Asset Census (NZ Steel workforce as critical category)
• Doc #33 — Tires (coal mining equipment maintenance)
• Doc #56 — Wood Gasification (gasifier bodies fabricated from Glenbrook plate)
• Doc #65 — Hydroelectric Station Maintenance (steel for hydro component repair)
• Doc #74 — Pastoral Farming (fencing wire needs — wire rod production priority)
• Doc #90 — Scrap Steel Recycling (complementary steel source)
• Doc #91 — Machine Shop Operations (maintenance support for Glenbrook; bar stock needs)
• Doc #93 — Foundry Operations (refractory production, roll casting potential)
• Doc #94 — Welding Electrode Fabrication (welding consumables for fabrication)
• Doc #97 — Cement Production (refractory cement potential)
• Doc #105 — Wire Drawing (downstream consumer of wire rod)
• Doc #106 — Small-Scale Electric Arc Furnaces (distributed steelmaking alternative)
• Doc #113 — Sulfuric Acid (industrial chemistry for some refractory processing)
• Doc #138 — Sailing Vessel Design (ship plate supply; trade route for electrode imports)
• Doc #157 — Trade Training Priorities (steelworker training pipeline)

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1. NZ Steel / BlueScope Steel NZ, company information and production data. NZ Steel’s Glenbrook works has a nominal steelmaking capacity of approximately 650,000 tonnes per year of steel slab. Actual annual production varies with market conditions. See BlueScope Steel Annual Reports and NZ Steel company publications. https://www.bluescopenzstel.co.nz/ — Note: exact figures are subject to commercial reporting and may vary by year.↩︎

2. NZ Steel site information. The Glenbrook plant is located at Mission Bush Road, Glenbrook, Franklin District, south of Auckland. Site area and general layout information from NZ Steel public documents and regulatory filings with the Waikato Regional Council and Auckland Council (the plant straddles council boundaries).↩︎

3. The Glenbrook steel mill commenced operations in 1968 under NZ Steel Ltd, a company originally established by the NZ government in 1965. The early process used an electric reduction furnace (submerged arc furnace) rather than the current rotary kiln process, which was adopted in the 1970s and progressively expanded. See: Ministry for Culture and Heritage, “NZ Steel,” NZ History. https://nzhistory.govt.nz/↩︎

4. BlueScope Steel acquired NZ Steel as part of the demerger of BHP Steel from BHP Billiton in 2002. BHP had previously acquired NZ Steel from the NZ government, which privatised the company in 1987. See BlueScope Steel corporate history.↩︎

5. NZ Steel employment figures are approximate and vary by year. The figure of approximately 1,500 direct employees and contractors is based on company reports and media coverage. Exact current staffing should be verified directly with NZ Steel. See: NZ Steel company reports; New Zealand Herald business reporting on NZ Steel.↩︎

6. NZ Steel product range: Hot-rolled coil, cold-rolled coil, ZINCALUME, COLORSTEEL, galvanised coil, and pipe/tube products. Product specifications and ranges are detailed in NZ Steel product catalogues and BlueScope technical data sheets. https://www.bluescopenzstel.co.nz/↩︎

7. NZ’s long-product steel imports (structural sections, rebar, wire rod) come primarily from Australia, China, and other Asian producers. NZ has no domestic long-product rolling capability. See: NZ Customs import data, Statistics NZ trade data, Steel & Tube Holdings Ltd annual reports (as a major NZ steel distributor).↩︎

8. NZ Steel / BlueScope Steel NZ, company information and production data. NZ Steel’s Glenbrook works has a nominal steelmaking capacity of approximately 650,000 tonnes per year of steel slab. Actual annual production varies with market conditions. See BlueScope Steel Annual Reports and NZ Steel company publications. https://www.bluescopenzstel.co.nz/ — Note: exact figures are subject to commercial reporting and may vary by year.↩︎

9. NZ Steel production volumes vary annually. Figures of 500,000–620,000 tonnes in recent years are estimates based on BlueScope annual report disclosures for the NZ Steel segment and industry commentary. Exact annual figures are commercially reported by BlueScope.↩︎

10. NZ total steel consumption estimated from industry data. The Metals NZ (formerly NZ Steel Fabricators) and HERA (Heavy Engineering Research Association) provide industry consumption data. https://www.hera.org.nz/ — Total apparent steel consumption of approximately 800,000–900,000 tonnes per year includes both NZ Steel production and imports.↩︎

11. Post-event steel demand estimate: This is a rough working estimate, not derived from a formal demand model. NZ’s pre-event steel consumption of approximately 800,000–900,000 tonnes/year includes construction, manufacturing, and export-oriented fabrication — most of which ceases under recovery conditions. The 200,000–400,000 tonne range is an order-of-magnitude estimate based on the assumption that essential infrastructure repair, agricultural equipment, and basic construction represent 25–50% of pre-event consumption. A more rigorous estimate would require a sector-by-sector assessment of post-event steel needs, which is itself dependent on event severity and recovery trajectory. This figure requires validation through the skills and asset census process (Doc #8).↩︎

12. NZ ironsand composition and geology: Titanomagnetite (Fe₂TiO₄ / Fe₃O₄ solid solution) is the primary iron-bearing mineral in NZ west coast black sands. Geological origin is volcanic — eroded from andesitic volcanoes of the Taranaki and central North Island volcanic zones. See: GNS Science publications; Nicholson, K.N., “The ironsand deposits of New Zealand,” various NZ geological publications. https://www.gns.cri.nz/↩︎

13. Ironsand concentrate composition: approximately 57–60% total iron, 7–8% TiO₂, plus minor vanadium (V₂O₅ ~0.3–0.5%), manganese, and other trace elements. Specific composition varies by deposit and concentration process. Based on NZ Steel technical publications and NZ geological survey data.↩︎

14. Waikato North Head ironsand mining operation: Hydraulic mining of coastal dune deposits using high-pressure water monitors, followed by wet magnetic separation. The operation has been mining since the 1960s under various regulatory consents. See: Waikato Regional Council resource consent documentation for NZ Steel Mining Ltd.↩︎

15. The ironsand slurry pipeline transports concentrated ironsand from Waikato North Head to Glenbrook — a distance of approximately 18 km. The pipeline is a steel pipe carrying a water-ironsand slurry. Pipeline length and basic design from NZ Steel operational descriptions and resource consent documentation.↩︎

16. NZ ironsand resource estimates: Total NZ west coast ironsand resources are estimated in the hundreds of millions to billions of tonnes across multiple deposits from Kaipara to Taranaki. The Waikato North Head deposit is one of several major concentrations. See: Crown Minerals NZ mineral resource assessments; GNS Science; NZ Steel Mining Ltd resource statements.↩︎

17. NZ Steel Glenbrook process description: The unique ironsand-to-steel process involves coal-based direct reduction in rotary kilns, followed by electric arc furnace melting, Kaldo converter refining, continuous slab casting, and hot/cold rolling. This process was developed specifically for NZ’s titanomagnetite ironsand and is not used at any other steelworks worldwide. See: NZ Steel technical publications; HERA (Heavy Engineering Research Association) NZ steel industry documentation; Cartwright, C.A., “The Development of the New Zealand Steel Industry,” various NZ engineering publications.↩︎

18. Glenbrook’s four rotary kilns are approximately 65 m long and 4 m in diameter — among the largest rotary kilns used in direct reduction globally. These dimensions are from NZ Steel operational descriptions and engineering literature on the Glenbrook process. Exact current dimensions should be verified as kilns may have been modified during the plant’s operational history.↩︎

19. Direct reduced iron (DRI) metallisation at Glenbrook: The ironsand is partially reduced in the kilns to approximately 75–85% metallisation (proportion of iron in metallic form). This is lower than typical gas-based DRI processes (which achieve 90%+) because of the titanomagnetite ore chemistry. The remaining reduction occurs in the EAF. Based on NZ Steel technical publications and general DRI metallurgy literature.↩︎

20. NZ Steel coal consumption: approximately 700,000–800,000 tonnes per year, primarily sub-bituminous coal from the Waikato coalfield. NZ Steel is the largest single coal consumer in NZ. See: MBIE (Ministry of Business, Innovation and Employment) NZ Energy Quarterly; NZ Steel environmental reporting.↩︎

21. Glenbrook operates two electric arc furnaces for melting the reduced ironsand. EAF capacity and configuration from NZ Steel operational documentation.↩︎

22. EAF electrical power draw: Modern EAFs typically draw 30–80 MW during the melt cycle. Glenbrook’s EAFs, handling DRI rather than scrap, may operate at the lower to middle end of this range due to different charge characteristics. Power draw figures are estimated from general EAF engineering literature and NZ Steel’s reported electricity consumption.↩︎

23. NZ Steel total electricity consumption: approximately 400–500 GWh per year. This makes it one of NZ’s largest individual electricity consumers (excluding Tiwai Point aluminium smelter). Based on MBIE energy data and BlueScope reporting. See: MBIE, “NZ Energy Data Tables.” https://www.mbie.govt.nz/building-and-energy/energy-and-n...↩︎

24. The Kaldo converter (a rotary oxygen steelmaking vessel) at Glenbrook is a distinctive feature of the plant’s process. Named after the Kaldo process developed in Sweden, it rotates during the oxygen blow to improve mixing. This is unusual — most modern steelworks use stationary BOF (basic oxygen furnace) converters. The Kaldo was selected for Glenbrook because of its suitability for the high-titanium slag produced from ironsand. See: NZ Steel technical publications; general steelmaking engineering literature (e.g., Ghosh, A. and Chatterjee, A., “Ironmaking and Steelmaking: Theory and Practice,” PHI Learning).↩︎

25. Lime (calcium oxide) production in NZ: Several lime kilns operate in NZ, including in the Waikato (e.g., Graymont/McDonald’s Lime at Otorohanga) and elsewhere. Limestone and dolomite deposits are widespread in NZ. See: NZ Minerals Industry Association; Crown Minerals. https://www.nzpam.govt.nz/↩︎

26. NZ manganese deposits: Small manganese deposits are known in NZ (e.g., in Northland and the East Cape region) but have not been commercially mined at significant scale. NZ relies on imported manganese for steel alloying. See: GNS Science mineral occurrence databases; Crown Minerals records.↩︎

27. Glenbrook continuous slab caster: Produces slabs of approximately 200 mm thickness and up to approximately 1,550 mm width. Slab dimensions from NZ Steel product specifications and operational documentation.↩︎

28. NZ zinc and aluminium: NZ has no zinc mining or smelting. Zinc is imported, primarily from Australia. Aluminium is produced at Tiwai Point but from imported alumina. NZ has no domestic bauxite. See: Stats NZ trade data; Rio Tinto NZAS information. https://www.riotinto.com/↩︎

29. Graphite electrode technology: General descriptions of EAF graphite electrode function, dimensions, and consumption are available in standard steelmaking engineering texts. See: Fruehan, R.J. (ed.), “The Making, Shaping and Treating of Steel — Steelmaking and Refining Volume,” AISE, 1998. Typical electrode diameters for medium-to-large EAFs are 400–700 mm.↩︎

30. Graphite electrode consumption rates: Industry-standard consumption is approximately 1.5–3.0 kg per tonne of steel for pre-baked graphite electrodes. UHP (ultra-high power) electrodes in modern EAFs achieve the lower end. Higher rates apply to older furnaces, lower-quality electrodes, and operations with DRI charge (like Glenbrook, where the partially reduced charge requires more energy and arc time than scrap). See: Graftech International technical literature; SGL Carbon product information; general EAF engineering references.↩︎

31. Graphite electrode manufacturing process: Petroleum needle coke or regular petroleum coke, mixed with coal tar pitch binder, is formed (typically by extrusion), baked at ~800–1,000°C, then graphitised at ~2,500–3,000°C in Acheson-type electric resistance furnaces. The graphitisation process takes days to weeks per batch. See: Graftech International; SGL Carbon; general carbon and graphite engineering literature.↩︎

32. Graphite electrode manufacturers: Major producers include Graftech International (USA), Showa Denko (Japan, now Resonac), SGL Carbon (Germany), Tokai Carbon (Japan), and several Chinese manufacturers (Fangda Carbon, Kaifeng Carbon). There is no graphite electrode production in NZ, Australia, or the Southern Hemisphere. The nearest likely production is in China, Japan, or India.↩︎

33. Steelworks electrode inventory: Typical steelworks maintain buffer stocks of electrodes measured in weeks to a few months of consumption. The exact inventory level varies with procurement strategy, supplier reliability, and commercial considerations. NZ Steel’s specific inventory is commercially sensitive and not publicly available.↩︎

34. Soderberg electrodes: Named after the Norwegian inventor Carl Wilhelm Soderberg (1916), these self-baking electrodes use a steel casing filled with electrode paste that bakes in situ from the heat of the furnace. Historically used in submerged-arc furnaces for ferroalloy production and in some older aluminium smelters. The paste is a mix of calcined anthracite or petroleum coke with coal tar pitch binder. See: Soderberg electrode technology in metallurgical engineering literature; Mujumdar, A.S. (ed.), “Handbook of Industrial Drying.”↩︎

35. Marsden Point oil refinery (Refining NZ, now Channel Infrastructure): NZ’s only oil refinery, located near Whangārei. It ceased refining operations in 2022 and converted to an import-only fuel terminal. Without refining, NZ cannot produce petroleum coke domestically (though some petroleum coke may exist in residual stocks from the refining era). See: Channel Infrastructure NZ. https://www.channelnz.com/↩︎

36. Refractory technology: General descriptions of refractory types, applications, and consumption in steelmaking are available in standard metallurgical engineering texts. See: Schacht, C.A. (ed.), “Refractories Handbook,” CRC Press; Carniglia, S.C. and Barna, G.L., “Handbook of Industrial Refractories Technology.”↩︎

37. Rotary kiln refractory lining life: 1–3 years depending on the zone within the kiln (the firing zone experiences the most severe conditions). Based on general rotary kiln refractory practice in the cement and minerals processing industries; NZ Steel’s specific experience may differ.↩︎

38. EAF refractory lining life: Modern EAFs using MgO-C linings typically achieve 200–1,000+ heats per campaign, depending on furnace size, operating practice, and refractory quality. Glenbrook’s specific lining life depends on its unique operating conditions (DRI charge, titanium-rich slag). See: EAF refractory practice literature; Fruehan (note 27).↩︎

39. NZ fireclay and silica deposits: Waikato and Bay of Plenty regions contain fireclay deposits suitable for refractory applications. Silica sand deposits exist in several NZ locations. These materials are suitable for lower-temperature refractory applications (below ~1,500°C). See: GNS Science; Crown Minerals mineral occurrence data.↩︎

40. NZ dolomite deposits: Dolomite (calcium-magnesium carbonate) occurs in several NZ locations. Calcined dolomite can serve as a basic refractory material. It is less durable than magnesite refractories in severe steelmaking conditions but is functional for some applications (converter and ladle linings). See: Crown Minerals; GNS Science.↩︎

41. NZ magnesite and magnesia-bearing minerals: NZ has limited known magnesite (MgCO₃) deposits. Some olivine and serpentine (magnesium silicate minerals) are found in the Nelson-Marlborough and Southland ultramafic rock belts, from which magnesia could theoretically be extracted. Commercial extraction has not been practised. See: GNS Science geological databases.↩︎

42. NZ graphite deposits: NZ has no known commercially significant natural graphite deposits. Small graphite occurrences have been noted in metamorphic rocks in the South Island, but none have been developed for production. See: Crown Minerals; GNS Science.↩︎

43. Seawater magnesia production: Magnesia (MgO) can be precipitated from seawater by adding lime (CaO) or dolime (calcined dolomite), which raises the pH and precipitates magnesium hydroxide (Mg(OH)₂), which is then calcined to MgO. This is a well-established industrial process — the Dow process, used commercially since the 1940s. It produces magnesia suitable for refractory applications. See: Kramer, D.A., “Magnesium, Its Alloys and Compounds,” USGS; general industrial chemistry references.↩︎

44. NZ zinc imports: All zinc consumed in NZ is imported. Major sources include Australia (Nyrstar’s Port Pirie and Hobart smelters), South Korea, and China. See: Stats NZ trade data; NZ Customs import statistics.↩︎

45. NZ Steel zinc consumption estimate: Based on approximate ZINCALUME and galvanised coil production volumes and typical zinc-aluminium bath consumption rates (approximately 15–25 kg of coating metals per tonne of coated product). The estimate of 3,000–5,000 tonnes/year covers both galvanising and ZINCALUME coating operations. Exact figures are commercially held by NZ Steel/BlueScope and should be verified directly.↩︎

46. New Zealand Aluminium Smelters (NZAS), Tiwai Point: Operated by Rio Tinto, the smelter produces aluminium from imported alumina (primarily from Queensland Alumina Ltd in Australia). The smelter’s future has been subject to commercial negotiations regarding electricity pricing with Meridian Energy. Regardless of operational status, it depends entirely on imported alumina. See: Rio Tinto NZAS; Meridian Energy. https://www.riotinto.com/↩︎

47. COLORSTEEL market dominance: COLORSTEEL (and its predecessor products) has been the dominant roofing and cladding material in NZ new construction for several decades. Exact market share figures are held by NZ Steel/BlueScope but the product’s dominance is evident from visual inspection of NZ’s built environment. See: BlueScope Steel NZ COLORSTEEL product information.↩︎

48. Service life of coated vs. bare steel: COLORSTEEL/ZINCALUME in NZ conditions (depending on exposure zone — coastal, industrial, rural) has an expected service life of 20–50+ years. Bare (uncoated) mild steel in NZ’s humid, maritime climate corrodes significantly faster — service life without any protection might be only 5–15 years depending on exposure and thickness. With basic paint protection, 10–25 years is plausible. Corrosion rate data for NZ conditions is published by BRANZ (Building Research Association of NZ). https://www.branz.co.nz/↩︎

49. Wire rod adaptation timeline estimate: Based on general engineering judgement for the scope of modifications required — billet caster construction or modification of existing casting and rolling equipment. No directly comparable project has been undertaken at Glenbrook. The estimate assumes NZ’s existing heavy engineering capability (Doc #91) can support the fabrication and installation work. Under recovery conditions, competing demands on engineering labour could extend the timeline further.↩︎

50. NZ Steel total electricity consumption: approximately 400–500 GWh per year. This makes it one of NZ’s largest individual electricity consumers (excluding Tiwai Point aluminium smelter). Based on MBIE energy data and BlueScope reporting. See: MBIE, “NZ Energy Data Tables.” https://www.mbie.govt.nz/building-and-energy/energy-and-n...↩︎

51. NZ electricity generation: Total annual generation approximately 42,000–44,000 GWh as of recent years, with approximately 80–85% from renewable sources (hydro, geothermal, wind). See: MBIE, “NZ Energy Data Tables”; Electricity Authority market data. https://www.ea.govt.nz/↩︎

52. NZ Steel coal consumption: approximately 700,000–800,000 tonnes per year, primarily sub-bituminous coal from the Waikato coalfield. NZ Steel is the largest single coal consumer in NZ. See: MBIE (Ministry of Business, Innovation and Employment) NZ Energy Quarterly; NZ Steel environmental reporting.↩︎

53. NZ coal production: Approximately 2.5–3 million tonnes per year in recent years, from the Waikato (Huntly coalfield — sub-bituminous) and West Coast, South Island (bituminous and sub-bituminous). NZ coal production has declined from a peak of ~5 million tonnes as domestic demand has fallen. See: MBIE, “NZ Energy Data Tables”; NZ Petroleum and Minerals.↩︎

54. NZ natural gas: Produced from the Taranaki Basin, with major fields including Pohokura, Maui, Mangahewa, Turangi, and others. Total NZ gas production has been declining as some fields deplete. Gas is transported via the North Island pipeline network operated by First Gas. See: MBIE energy statistics; First Gas. https://www.firstgas.co.nz/↩︎

55. NZ Steel on-site maintenance capability: Major industrial plants like Glenbrook maintain dedicated workshops with machining, welding, electrical, and instrument maintenance capability. NZ Steel’s maintenance operation is one of the largest industrial maintenance workshops in NZ. Description based on general knowledge of integrated steelworks maintenance operations; specific details should be verified with NZ Steel.↩︎

56. Tramp elements in scrap recycling: Copper, tin, and other elements that enter the scrap stream (from copper wire in motors, tin plating on cans, zinc from galvanised products) accumulate with each recycling cycle because they cannot be economically removed by steelmaking processes. Over multiple recycling generations, these elements degrade steel quality — particularly causing hot shortness (cracking during hot working) from copper contamination. See: Savov, L. et al., “Problems of recycling in steelmaking,” Journal of the University of Chemical Technology and Metallurgy; general steelmaking metallurgy references.↩︎

57. Reduced production rate target: This range is an engineering estimate balancing consumable conservation against maintaining operational continuity and meeting essential demand. The lower bound (150,000 tonnes/year) represents the approximate minimum throughput at which Glenbrook’s process remains operationally viable — below this level, furnace heat losses and process inefficiencies increase disproportionately. The upper bound (300,000 tonnes/year) represents approximately half of nominal capacity, chosen to roughly double consumable stock life relative to full production.↩︎