Titanium Sponge — Kroll Process, GB/T 2524 Grade 0 / 1 / 2
Titanium sponge is the primary metallic feedstock for all wrought and cast titanium products. Produced via the Kroll process, it enters the supply chain as irregular porous lumps before being consolidated into ingot or powder. SEMITECH sources from major Chinese producers with direct mill relationships and consistent CoA documentation.
| Grade 0 | Grade 1 | Grade 2 |
|---|---|---|
| ≥99.7% Ti | ≥99.6% Ti | ≥99.5% Ti |
What Is Titanium Sponge: Kroll Process Chemistry
Titanium sponge is manufactured by the Kroll process: titanium tetrachloride (TiCl₄) is reduced with magnesium metal in a sealed reactor at 800–850°C, yielding a porous titanium matrix (Ti sponge) and magnesium chloride (MgCl₂) as by-product.
Reaction: TiCl₄ + 2 Mg → Ti + 2 MgCl₂
The MgCl₂ is tapped off and electrolyzed to recycle magnesium and chlorine back into the process — a closed-loop design that makes the Kroll route the dominant commercial pathway, accounting for >95% of global primary titanium production. The resulting sponge is crushed, blended, and vacuum-arc remelted (VAR) to produce ingot, or atomized into powder for additive manufacturing and powder metallurgy.
Grades and Specifications: GB/T 2524
Chinese titanium sponge is classified under GB/T 2524. Impurity limits are tighter at higher grades; Grade 0 is preferred for aerospace alloys where interstitials directly affect fracture toughness.
| Property | Grade 0 | Grade 1 | Grade 2 |
|---|---|---|---|
| Ti (min, %) | 99.7 | 99.6 | 99.5 |
| Fe (max, %) | 0.06 | 0.10 | 0.15 |
| O (max, %) | 0.06 | 0.08 | 0.10 |
| N (max, %) | 0.012 | 0.015 | 0.020 |
| C (max, %) | 0.015 | 0.020 | 0.025 |
| Si (max, %) | 0.010 | 0.012 | 0.015 |
| Cl (max, %) | 0.08 | 0.10 | 0.12 |
| Hardness (HB, max) | 100 | 110 | 120 |
Particle sizing: standard lump 10–50 mm; fine sponge (2–10 mm) available for cold-hearth melting and plasma atomization. Custom blending of Grade 0 and Grade 1 to hit intermediate interstitial targets is common for aerospace procurement.
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Applications
Aerospace titanium alloys — Grade 0 sponge is the primary feedstock for Ti-6Al-4V (6-4), the most widely used structural titanium alloy. A single widebody aircraft frame contains 15–40 MT of titanium mill product, all traceable to sponge through VAR ingot certification. Boeing and Airbus both maintain multi-tier supply chain audits back to sponge origin.
Medical implants and surgical instruments — Commercially pure (CP) titanium Grades 1–4 and Ti-6Al-4V ELI (extra-low interstitial) are melted from Grade 0 sponge blended with master alloy additions. Biocompatibility requires Fe <0.10% and O <0.08%.
Marine and desalination — Ti Grade 2 and Grade 12 tubing for heat exchangers, saltwater piping, and offshore structures tolerates seawater corrosion without cathodic protection. Less stringent interstitial specs allow Grade 1–2 sponge in the melt blend.
Chemical processing — Titanium reactors, heat exchangers, and electrodes in chlor-alkali, sulfuric acid, and pharmaceutical plants. CP titanium Grades 2–7 dominate; sponge Grade 1–2 is typical feedstock.
Additive manufacturing / powder — Plasma atomized Ti-6Al-4V and CP-Ti powder for laser powder bed fusion (LPBF) and directed energy deposition (DED) originates from Grade 0 sponge to meet Hall flowability and oxygen specifications.
China Market Context
China produces 200,000+ MT/year of titanium sponge, accounting for roughly 60% of global output. The three dominant producers are:
- Panzhihua Steel (攀钢钛业, PANGANG) — Sichuan, integrated upstream with Panzhihua ilmenite; largest single-site sponge producer in China.
- Zunyi Titanium (遵义钛业) — Guizhou; grade range covers 0 through 2; primary supplier to domestic aerospace forges.
- Baoji Titanium (宝鸡钛业) — Shaanxi; historically strong on Grade 0 for aerospace; also produces titanium ingot and mill product in-house.
Spot sponge pricing Q2 2026: Grade 0 CNY 52,000–58,000/MT; Grade 1–2 CNY 44,000–50,000/MT. Prices are sensitive to aerospace build rates and Chinese domestic mill restocking cycles.
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FAQ
+What is the difference between titanium sponge Grade 0 and Grade 2?
Grade 0 has tighter interstitial limits: Fe ≤0.06%, O ≤0.06%, N ≤0.012%. Grade 2 allows Fe ≤0.15%, O ≤0.10%. For aerospace fracture-critical parts (fan blades, airframe forgings), Grade 0 is mandatory. Grade 2 is acceptable for chemical-process equipment and marine hardware where ductility margins are wider.
+What is the Kroll process and why is it dominant?
The Kroll process reduces TiCl₄ with magnesium at 800–850°C. It is batch-operated, energy-intensive (~35–40 kWh/kg Ti), but produces consistently low oxygen and nitrogen levels that are difficult to achieve via the alternative Hunter process (sodium reduction) or electrolytic routes. The closed-loop Mg/Cl₂ recycle improves economics at scale.
+What lot sizes and packaging does SEMITECH offer?
Standard commercial quantities: 1–5 MT per shipment in steel drums or big bags. Trial lots from 100 kg available. CoA with chemical analysis and hardness per GB/T 2524 provided for each batch. Moisture content <0.1% guaranteed at time of packing.
+How is titanium sponge converted into usable alloy?
Sponge is blended with master alloy (Al-V hardener for Ti-6Al-4V), compacted into electrodes, and vacuum-arc remelted (VAR) two or three times to achieve chemical homogeneity. The resulting ingot is then forged, rolled, or extruded into mill products (bar, sheet, plate, tube, wire).
+Can titanium sponge be used directly in powder metallurgy?
Kroll sponge must first be plasma-atomized to produce spherical powder suitable for LPBF or MIM. Crushed sponge fines (<2 mm) are sometimes used in press-and-sinter PM where morphology is less critical, but flow and packing density are inferior to atomized powder.