Spongy titanium is the main raw material of titanium alloy. Spongy titanium is the base of titanium industry. It is the raw material of titanium, titanium powder and other titanium components.

Change ilmenite into titanium tetrachloride and put it in a sealed stainless steel tank filled with argon. The porous "spongy titanium" cannot be used directly and must be melted into liquid in an electric furnace before it can be cast into titanium ingots.

The alloying element titanium has two kinds of homogeneous and dissimilar crystals: titanium with dense hexagonal structure below 882℃ and titanium with body centered cube above 882℃. Alloying elements can be divided into three types according to their effects on phase transition temperature: (1) elements that stabilize phase transition and increase phase transition temperature are stable elements, including aluminum, carbon, oxygen and nitrogen. Aluminum is the main alloying element of titanium alloy, which has obvious effects on increasing the strength at room temperature and high temperature, reducing specific gravity and increasing the elastic modulus of the alloy. The elements stabilizing the phase transition and decreasing the phase transition temperature are stable stable elements, which can be divided into two types: isomorphic and eutectoid. The former has molybdenum, niobium, vanadium, etc. The latter has chromium, manganese, copper, iron, silicon and so on. The elements that have little effect on phase transition temperature are neutral elements, such as zirconium and tin.

Oxygen, nitrogen, carbon and hydrogen are the main impurities in titanium alloys. The solubility of oxygen and nitrogen in the phase was higher than that in the phase, which strengthened the titanium alloy, but reduced the plasticity. Generally, the content of oxygen and nitrogen in titanium is less than 0.15 ~ 0.2% and 0.04 ~ 0.05% respectively. Hydrogen has little solubility in the solid phase, and too much hydrogen dissolved in titanium alloys produces hydrides that make the alloy brittle. Usually the hydrogen content in titanium alloy is controlled below 0.015%. The dissolution of hydrogen in titanium is reversible and can be removed by vacuum annealing.