The titanium smelting process is the extract of titanium from titanium-containing minerals like ilmenite and rutile, mainly including the preparation of titanium-rich materials, chlorination to produce titanium tetrachloride (TiCl₄), magnesium thermal reduction (Kroll process) or sodium thermal reduction (Hunter process), and the refining of sponge titanium, etc.
This guide will provide you with an interpretation of the main methods and how to solve the difficulties in the smelting titanium process.
Titanium Ores
Titanium ore is mainly of two categories: primary ore (rock ore) and secondary ore (placer ore). Rock ore (primary ore): Mainly distributed in China, Canada, Norway and Russia, suitable for large-scale mining but with high costs. Placer (secondary ore): Mainly distributed in Australia, South Africa, the United States and Brazil, it’s easy to mine and high grade, but the resources are relatively scattered.
Evolution of Titanium Smelting
The history of titanium smelting started in the early 20th century, through a long process from laboratory to industrial production. Below are the key stages and milestones development of titanium smelting：
- Early exploration (before the 1910s)
In 1791, the British minister William Gregor discovered titanium in ilmenite, but the extraction of titanium wasn’t achieved.
- The birth of the magnesium thermal reduction method(1930s-1940s).
In 1932, Luxembourg scientist William Kroll attempted to reduce titanium tetrachloride (TiCl₄) with calcium and achieved initial success.
In 1940, Kroll improved the process and used magnesium instead of calcium to reduce TiCl₄, laying the foundation for the modern Kroll process.
In 1948, DuPont of the United States first achieved industrial production using the Kroll process, marking the beginning of manufacturing sponge titanium.
- Industrialization development and technological progress(1950s-1980s)
In 1950, the United States, Japan and other countries had built titanium smelting industry.
1960s-1970s, China had built the titanium industry, and Baoji Nonferrous Metals Processing Plant became an important production base.
- Modern titanium smelting process (Since the 1990s)
In the 21st century, China has become the world’s largest producer of titanium, and Baoji has formed the “China Titanium Valley”, with its titanium material output accounting for 33% of the global total.
Step of Titanium Smelting Process
Titanium ore enrichment (increasing TiO₂ content)
Raw materials: Ilmenite (FeTiO₃) or Rutile ( TiO₂)
Method:
Chemical enrichment:
Sulfuric acid method: Ilmenite reacts with sulfuric acid to titanyl sulfate, which is calcined to obtain artificial rutile (TiO₂≥90%).
Chlorination method: Direct chlorination of titanite generates TiCl₄.
Titanium tetrachloride is produced by chlorination（TiCl₄）
Reaction: Titanium-rich material (TiO₂) reacts with coke and chlorine gas at 900-1000℃
Purification: Distillation used to remove impurities such as FeCl₃ and SiCl₄ to obtain high-purity TiCl₄ (liquid).
Preparation of sponge titanium by reduction
Reaction: TiCl₄ reacts with molten magnesium at 800-900 °C
Product: Porous sponge titanium
Cast into titanium ingots
Vacuum consumable arc melting（VAR）：
Sponge titanium pressed into electrodes and then arc melted in a vacuum or argon to cast into titanium ingots.
Processing and forming (forging/rolling, etc.)
Forging: Titanium ingots heated and then formed through the forging press. (Such as titanium bars)
Rolling: To produce titanium plates, titanium pipes, etc.
Some Methods of the Titanium Smelting Process
Kroll Process
Principle: Magnesium thermal reduction titanium tetrachloride
Features
The main industrial method (accounting for 90% of global output)
The production time is long (5-7 days).
High energy consumption (about 20,000 kilowatt-hours of electricity is consumed per ton of titanium)
The product is sponge titanium (purity over 99.6%).
Hunter Process
Features
The reaction temperature is relatively low (500-600℃)
Sodium has high activity and high dangerous
The by-product NaCl is difficult to recover
It has been basically replaced by the Kroll process
FFC Cambridge Process
Principle: Electrolytic reduction of titanium dioxide
Features
Directly use TiO₂ raw materials
The energy consumption reduced by 50%
It is still at the laboratory stage
PRP Process
Principle: Hydrogenation-dehydrogenation (HDH) to produce titanium powder
Features:
Suitable for powder metallurgy
Products are titanium powder
Used in emerging fields such as 3D printing
Molten Salt Electrolysis Method
Principle: Electrolyze titanium compounds in molten salt
Features:
High-purity titanium can be produced
Low energy consumption
The process control is very difficult
Armstrong Process
Principle: Gas-phase reduction of titanium chloride
Features
Nano titanium powder can be produced
Suitable for special applications
The output is limited.
| Method | Material | Reducing agent | Temperature(℃) | Product modality | Maturity |
| Kroll | TiCl₄ | Mg | 800-900 | Titanium sponge | Industrialization |
| Hunter | TiCl₄ | Na | 500-600 | Titanium sponge | Elimination |
| FFC | TiO₂ | Electrolysis | 800-1000 | Titanium Alloy | Experiment |
| PRP | Titanium sponge | H₂ | 400-600 | Titanium Powder | small-scale |
Problems Encountered
There are multiple technical difficulties points in the titanium smelting process, such as material properties, process control and cost efficiency.
High activity and pollution control
Difficult points:
Titanium is prone to react with elements such as O, N, H, and C at high temperatures, forming brittle compounds (such as TiO₂ and TiN), leads to the decline in material properties.
During smelting, it is necessary to avoid reactions with refractory materials.
Solution
Inert/vacuum environment: Argon gas protection or vacuum smelting (such as VAR furnace) is adopted.
Cold furnace bed technology: Electron beam or plasma melting (EBM/PAM).
Kroll process limitations
Difficult points:
Batch production: The reduction of TiCl₄ by magnesium requires batch operation, which is inefficient (a single cycle needs 5-7 days).
High energy consumption: Each ton of titanium smelting consumes 20,000 kilowatt-hours of electricity, and the lead time cost of magnesium/chlorine is high.
Impurities in sponge titanium: Residual Mg and MgCl₂ need to be removed by vacuum distillation.
solution:
Continuous improvement: such as the semi-continuous Kroll process.
New reducing agents: Exploring alternatives to magnesium such as Ca and Na-K alloys.
Uniformity of alloy composition
Difficult point:
Titanium alloys (such as Gr5) require precise control of the distribution elements like Al and V, but high-melting-point elements (such as Mo and W) are prone to segregation.
Ingots are prone to local enrichment or surface hardened layers.
Solution
Multiple VAR melting: Three titanium melting processes can reduce the component deviation to less than ±0.5%.
Powder metallurgy: Mechanical alloying (MA) or PREP powder preparation + hot isostatic pressing (HIP).
Difficult to Recycle Waste Materials
Difficult points
Titanium waste is prone to impurities such as Fe and Ni, and direct remelting will reduce performance.
The oxide layer (TiO₂) needs to treated by hydrogenation and dehydrogenation (HDH), and high cost.
Solution
Electron beam cooling bed furnace (EBCHM): It can smelt waste materials containing impurities.
Sorting technology: Automatic classification by laser-induced breakdown spectroscopy (LIBS).
Latest Trends in Research and Development
In recent years, titanium smelting and forging technologies have resulted in shorter smelting processes, lower costs, and integration to reduce energy consumption. The latest trends in titanium smelting research and development focus on green and low-carbon, short-process high efficiency and intelligence, breaking through the high energy consumption bottleneck of the traditional Kroll process. Sulfur-chlorine coupling technology achieves zero waste discharge, powder metallurgy short process and FFC electrolysis method reduces costs and improves efficiency, intelligent VAR smelting and 3D printing enhance the performance of high-end titanium alloys. The “Titanium Valley” model in China has accelerated the integration of the entire industrial chain, and Baoji City has formed an industrial cluster. In the future, as hydrogen metallurgy and other technologies mature, titanium smelting will develop towards lower energy consumption and higher performance, supporting aerospace, new energy and other fields.
Conclusion
Titanium smelting process has evolved from the early Hunter process to Kroll process, undergoing an evolution from laboratory to industrial production. At present, the main of titanium smelting process is confronted with problems such as high activity pollution, high energy consumption and difficulty in waste recycling etc., the latest research and development trends focus on green and low-carbo, short smelting processes, intelligence, and high-end applications. In the future titanium smelting technologies will break through reducing consumption by about 50% and costs by about 30%, promoting the wider application of titanium in fields such as aerospace and new energy.
FAQ
Q: Why is titanium so hard to refine?
A: Because titanium readily reacts with elements such as oxygen, nitrogen and carbon at high temperatures, stable compounds, traditional smelting must be carried out in a vacuum or inert gas environment, and multiple complex processes (such as the Kroll process) are required to purity titanium.
Q: Is titanium hard to melt?
A: Yes. Click here to check our blog.
Q: What is the refining process of titanium?
A: Titanium ore → Kroll process → Titanium sponge
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