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Mn lowers the lower critical point of steel, increases the degree of supercooling when austenite cools, refines the pearlite structure to improve its mechanical properties, and is an important alloying element of low-alloy steel, which can significantly increase the hardenability of steel, but Increased tendency to grain coarsening and temper brittleness
Mo improves the hardenability of the steel. When the content is 0.5%, the temper brittleness can be reduced and secondary hardening can occur. Improves thermal strength and creep strength, and increases corrosion resistance to organic acids and reducing media when the content is 2% to 3%
N has unobvious effect of solid solution strengthening and hardenability, improves creep strength, combines with other elements in steel, has precipitation hardening effect, surface nitriding, improves hardness and wear resistance, and increases corrosion resistance. Residual nitrogen in low carbon steel can lead to aging brittleness
The solid solution strengthening effect of Nb is obvious. It improves the hardenability of the steel (when dissolved in austenite), increases the tempering stability, has a secondary hardening effect, and improves the strength and impact toughness of the steel. When the content is high (larger than carbon 8 times the content, which makes the steel has good hydrogen resistance and improves the high temperature performance of the hot strength steel (creep strength, etc.)
Ni improves the plasticity and toughness, improves the low-temperature toughness, improves the corrosion resistance, and is used together with chromium and molybdenum to increase the thermal strength. It is one of the main alloying elements of hot-strength steel and stainless acid-resistant steel.
P Solid solution strengthening and cold work hardening works well. Combined with copper, it improves the atmospheric corrosion resistance of low-alloy high-strength steels, but reduces its cold stamping performance. It is used in combination with sulfur and manganese to improve machinability and increase tempering. Brittleness and cold brittleness sensitivity
Pb Improves Machinability
RE includes lanthanoid elements and 17 elements such as yttrium and lanthanum. It has degassing, desulfurization, and elimination of other harmful impurities, improving the as-cast microstructure of the steel. The content of 0.2% can improve the oxidation resistance, high temperature strength and creep. Strength, increase corrosion resistance
S Improves machinability. Produces hot brittleness, deteriorates the quality of steel, has high sulfur content, and has a bad influence on weldability
Si's commonly used deoxidizers have solid-solution strengthening effect, increase resistivity, reduce hysteresis loss, improve magnetic permeability, improve hardenability, and resist tempering, are beneficial to improve comprehensive mechanical properties, increase elastic limit, and increase natural conditions The corrosion resistance. When the content is high, the weldability is reduced, and cold brittleness is easily caused. Medium-carbon and high-carbon steels tend to be graphitized during tempering
Ti has a strong solid-solution strengthening effect, but lowers the toughness of the solid solution, and solid solution in the austenite improves the hardenability of the steel, but the combined titanium reduces the hardenability of the steel. Improve the tempering stability, and have secondary hardening, improve the oxidation resistance and heat strength of heat-resistant steel, such as creep and durability, and improve the weldability of steel
The solid solution of V in austenite can increase the hardenability of steel, but the presence of vanadium in the combined state will reduce the hardenability of the steel, increase the tempering stability of the steel, and have a strong secondary hardening effect. Soluble in ferrite has a strong solid-solution strengthening effect. Refine grain to improve low-temperature impact toughness. Vanadium carbide is the best hardened metal carbide. It significantly improves the service life of the tool steel and improves the creep and durability of the steel. When the vanadium and carbon content ratio exceeds 5.7, Can greatly improve the ability of steel to resist high temperature and high pressure hydrogen corrosion, but it will slightly reduce the high temperature oxidation resistance
W has a secondary hardening effect, so that the steel has a red hardness, improve wear resistance, the effect of steel on hardenability, tempering stability, mechanical properties and thermal strength are similar to molybdenum, slightly reduce the oxidation resistance of steel
Zr zirconium acts similarly to niobium, titanium and vanadium in the steel. When the content is small, it can deoxidize, purify and refine the grain, increase the low-temperature toughness of the steel, eliminate the aging phenomenon, and improve the stamping performance of the steel Note: The content of each component All refer to quality scores.
The effect of alloying elements on the properties of steel
When the content is low, the effect is similar to that of nickel. When the content is high, it is unfavorable for hot deformation processing. If the content is more than 0.30%, high-temperature copper brittleness occurs during hot deformation processing. When the content is higher than 0.75%, the solid content is high. Dissolution and aging can produce aging strengthening. In low-carbon alloy steels, especially with phosphorus, it can improve the atmospheric corrosion resistance of steel. 2% to 3% of copper can improve the corrosion resistance and stress corrosion of sulfuric acid, phosphoric acid and hydrochloric acid in stainless steel. Stability