The role of alloying elements(Tungsten(W), Vanadium(V), Titanium(Ti))
In this article, let's take a look at what is the role of tungsten, vanadium and titanium in steel.
(1)Tungsten(W)
In addition to form carbides in the steel, tungsten is partially dissolved in iron to form a solid solution. Its effect is similar to that of molybdenum. But the general effect is not as significant as molybdenum by a mass fraction. Tungsten mainly increases tempering stability, red hardness, heat strength and increased wear resistance due to the formation of carbides in steel. Therefore, it is mainly used for tool steel, such as high-speed steel, steel for hot forging die, and the like.
Tungsten forms refractory carbides in high-quality spring steel. When tempering at a higher temperature, it can alleviate the aggregation process of carbides and maintain high-temperature strength. Tungsten also reduces the heat sensitivity of steel, increases hardenability and increases hardness. 65SiMnWA spring steel has high hardness after air-cooling and the spring steel with 50mm2 section can be hardened in oil, which can be used as an important spring to withstand heavy load, heat resistance (not more than 350 °C) and an impact. 30W4Cr2VA high-strength heat-resistant high-quality spring steel with large hardenability, quenching at 1050～1100°C, tensile strength after tempering at 550～650°C reaches 1470～1666Pa. It is mainly used to manufacture springs that are used at high temperatures (not more than 500°C). The addition of tungsten can significantly improve the wear resistance and machinability of steel. Therefore, tungsten is the main element of alloy tool steel.
(2)Vanadium(V)
Vanadium has a strong affinity with carbon, ammonia and oxygen to form a corresponding stable compound. Vanadium is mainly present in the form of carbides in steel. Its main function is to refine the structure and grain of steel and improve the strength and the toughness of steel. When the solid solution is dissolved at a high temperature, the hardenability is increased. Conversely, if present in the form of carbides, the hardenability is reduced. Vanadium increases the tempering stability of hardened steel and produces a secondary hardening effect. The vanadium content in steel is generally not more than 0.5% except for high-speed tool steel.
Vanadium can refine grains in ordinary low carbon alloy steel, improve the strength and yield ratio and low temperature characteristics after normalizing, and improve the welding performance of steel. Vanadium in alloy structural steels will reduce hardenability under general heat treatment conditions. Therefore, it is often used in combination with elements such as manganese, chromium, molybdenum and tungsten in structural steel. In the quenched and tempered steel, vanadium mainly improves the strength and yield ratio of the steel, refines the grains, and reduces the sensitivity to overheating. In the carburized steel, because of the grain can be refined, the steel can be directly quenched after carburizing without secondary quenching.
Vanadium improves strength and yield ratio in spring steel and bearing steel. In particular, the proportional limit and the elastic limit are increased, and the decarburization sensitivity during heat treatment is lowered, thereby improving the surface quality. The five-chrome vanadium-containing bearing steel has high carbonization dispersion and good performance. Vanadium refines grai, reduces overheat sensitivity, increases tempering stability and wear resistance in tool steel,and extends tool life.
(3)Titanium(Ti)
Titanium has a strong affinity with nitrogen, oxygen and carbon, and has a stronger affinity for sulfur than iron. Therefore, it is a good deoxidizing deaerator and an effective element for fixing nitrogen and carbon. Although titanium is a strong carbide forming element, it does not combine with other elements to form a composite compound. Titanium carbide has strong bonding strength, is stable, and is not easy to decompose. It can be slowly dissolved into a solid solution in steel only when heated to above 1000 °C. The titanium carbide particles have an effect of preventing grain growth before they are dissolved. Titanium is commonly used in stainless steel to fix carbon to eliminate the depletion of chromium at the grain boundaries, thereby eliminating or reducing intergranular corrosion of the steel.
Titanium is also one of the strong ferrite forming elements, which strongly increases the temperature of steel A1 and A3. Titanium improves plasticity and toughness in ordinary low alloy steels. Since titanium fixes nitrogen and sulfur and forms titanium carbide, the strength of the steel is increased. After normalizing to refine the grain, the carbide formed by precipitation can significantly improve the plasticity and impact toughness of the steel. Titanium-containing alloy structural steel with good mechanical properties and process properties. But the main disadvantage is that the hardenability is slightly worse. In high chromium stainless steel, it is usually necessary to add about 5 times the carbon content of titanium. It not only improves the corrosion resistance and toughness of steel, but also organizes the grain growth tendency of steel at high temperatures and improves the weldability of steel.
(1)Tungsten(W)
In addition to form carbides in the steel, tungsten is partially dissolved in iron to form a solid solution. Its effect is similar to that of molybdenum. But the general effect is not as significant as molybdenum by a mass fraction. Tungsten mainly increases tempering stability, red hardness, heat strength and increased wear resistance due to the formation of carbides in steel. Therefore, it is mainly used for tool steel, such as high-speed steel, steel for hot forging die, and the like.
Tungsten forms refractory carbides in high-quality spring steel. When tempering at a higher temperature, it can alleviate the aggregation process of carbides and maintain high-temperature strength. Tungsten also reduces the heat sensitivity of steel, increases hardenability and increases hardness. 65SiMnWA spring steel has high hardness after air-cooling and the spring steel with 50mm2 section can be hardened in oil, which can be used as an important spring to withstand heavy load, heat resistance (not more than 350 °C) and an impact. 30W4Cr2VA high-strength heat-resistant high-quality spring steel with large hardenability, quenching at 1050～1100°C, tensile strength after tempering at 550～650°C reaches 1470～1666Pa. It is mainly used to manufacture springs that are used at high temperatures (not more than 500°C). The addition of tungsten can significantly improve the wear resistance and machinability of steel. Therefore, tungsten is the main element of alloy tool steel.
(2)Vanadium(V)
Vanadium has a strong affinity with carbon, ammonia and oxygen to form a corresponding stable compound. Vanadium is mainly present in the form of carbides in steel. Its main function is to refine the structure and grain of steel and improve the strength and the toughness of steel. When the solid solution is dissolved at a high temperature, the hardenability is increased. Conversely, if present in the form of carbides, the hardenability is reduced. Vanadium increases the tempering stability of hardened steel and produces a secondary hardening effect. The vanadium content in steel is generally not more than 0.5% except for high-speed tool steel.
Vanadium improves strength and yield ratio in spring steel and bearing steel. In particular, the proportional limit and the elastic limit are increased, and the decarburization sensitivity during heat treatment is lowered, thereby improving the surface quality. The five-chrome vanadium-containing bearing steel has high carbonization dispersion and good performance. Vanadium refines grai, reduces overheat sensitivity, increases tempering stability and wear resistance in tool steel,and extends tool life.
(3)Titanium(Ti)
Titanium has a strong affinity with nitrogen, oxygen and carbon, and has a stronger affinity for sulfur than iron. Therefore, it is a good deoxidizing deaerator and an effective element for fixing nitrogen and carbon. Although titanium is a strong carbide forming element, it does not combine with other elements to form a composite compound. Titanium carbide has strong bonding strength, is stable, and is not easy to decompose. It can be slowly dissolved into a solid solution in steel only when heated to above 1000 °C. The titanium carbide particles have an effect of preventing grain growth before they are dissolved. Titanium is commonly used in stainless steel to fix carbon to eliminate the depletion of chromium at the grain boundaries, thereby eliminating or reducing intergranular corrosion of the steel.
Titanium is also one of the strong ferrite forming elements, which strongly increases the temperature of steel A1 and A3. Titanium improves plasticity and toughness in ordinary low alloy steels. Since titanium fixes nitrogen and sulfur and forms titanium carbide, the strength of the steel is increased. After normalizing to refine the grain, the carbide formed by precipitation can significantly improve the plasticity and impact toughness of the steel. Titanium-containing alloy structural steel with good mechanical properties and process properties. But the main disadvantage is that the hardenability is slightly worse. In high chromium stainless steel, it is usually necessary to add about 5 times the carbon content of titanium. It not only improves the corrosion resistance and toughness of steel, but also organizes the grain growth tendency of steel at high temperatures and improves the weldability of steel.
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