Application and influence of titanium in steel
Titanium (Ti), as a high-quality alloying element, is widely used to improve the comprehensive performance of steel, especially in the fields of aviation, marine engineering and construction. The application of titanium in steel is mainly focused on improving strength, corrosion resistance and ductility, and can effectively reduce the brittleness and weight of the material.
1. The effect of titanium on the microstructure and heat treatment of steel
Titanium has a strong affinity with elements such as nitrogen, oxygen, and carbon. It is an excellent deoxidizer and an effective element for fixing nitrogen and carbon. In steel, the compound (TiC) formed by titanium and carbon has a strong binding force and high stability. It will only slowly dissolve into the solid solution of iron at high temperatures (above 1000°C). These TiC particles can prevent the growth and coarsening of steel grains and have an important influence on the microstructure of steel. In addition, titanium is one of the strong ferrite-forming elements, which will reduce the austenite phase area. Solid solution titanium can improve the hardenability of steel, while the presence of TiC particles will reduce the hardenability of steel. When the titanium content reaches a certain value, precipitation hardening will occur due to the dispersion and precipitation of TiFe2.
2. The influence of titanium on the mechanical properties of steel
The influence of titanium on the mechanical properties of steel depends on its existence form, the content ratio of titanium and carbon, and the heat treatment method. When titanium exists in ferrite in a solid solution state, its strengthening effect is higher than that of elements such as aluminum, manganese, nickel, and molybdenum, and is second only to elements such as beryllium, phosphorus, copper, and silicon. In the range of 0.03% to .1% mass fraction of titanium, titanium can increase the yield strength of steel. However, when the content ratio of titanium to carbon exceeds 4, the strength and toughness of steel will drop sharply. In addition, titanium can also improve the long-term strength and creep resistance of steel, and improve the toughness of steel, especially the low-temperature impact toughness.
3. The influence of titanium on the physical, chemical and process properties of steel
Titanium can improve the stability of steel in high temperature, high pressure, and hydrogen environments, and enhance the corrosion resistance of stainless acid-resistant steel, especially the resistance to intergranular corrosion. In low-carbon steel, when the ratio of titanium to carbon reaches 4.5 or more, the steel has excellent resistance to stress corrosion and alkali embrittlement. In addition, titanium can improve the oxidation resistance of steel at high temperatures and promote the formation of nitriding layer, so as to obtain the required surface hardness more quickly. Titanium-containing steel is called "fast nitriding steel" and can be used to manufacture high-precision screws. At the same time, titanium can also improve the weldability of low-carbon manganese steel and high-alloy stainless steel.
4. Summary
In general, titanium is widely used in steel. When its mass fraction exceeds 0.025%, it can be considered as an alloying element. Titanium is widely used in ordinary low-alloy steel, alloy structural steel, alloy tool steel, high-speed tool steel, stainless acid-resistant steel, heat-resistant non-scaling steel, permanent magnet alloy and cast steel. In addition, titanium has become an important component of various advanced materials and an important strategic material. In the aerospace industry, the use of titanium accounts for more than half, and it is widely used in aerospace vehicles, power machinery and other fields.
