Hardening and tempering of steel
Hardening and tempering of steel, generally refers to the carbon content of 0.3-0.6% of carbon steel. Parts made of this type of steel are generally required to have good overall mechanical properties, that is, to maintain high strength at the same time have good ductility and toughness, people tend to use continuous hardening and tempering furnace to achieve this purpose, so people are accustomed to call this kind of steel as hardened and tempered steel. A large number of structural parts on various machines is using hardened and tempered steel, which is the steel most widely used in the structure steel.
Hardened and tempered steel refers to the steel which is tempered within the range of 500-650 degrees. After hardening and tempering heat treatment, the strength, ductility and toughness of the steel are well matched.
The composition of hardened and tempered steel is carbon containing 0.25% ~ 0.5% carbon steel or low alloy steel and medium alloy steel. The hardened and tempered metallurgical structure is tempered sorbite. A large number of structural parts on various machinesis using hardened and tempered steel. The most widely used hardened and tempered steel is chromium hardened and tempered steel (such as 40Cr, 40CrSi), chrome-manganese hardened and tempered steel (such as 40CrMn), chrome-nickel hardened and tempered steel (such as 40CrNiMo, 37CrNi3A), boron hardened and tempered steel .
Carbon content of 0.3 to 0.5%, and contains one or more alloying elements, with a lower or medium degree of alloying. The role of alloying elements in steel is to improve the hardenability of the steel and to ensure to get expected overall performance of the part after tempering at elevated temperatures.
Heat treatment process: The steel will change into martensite after quenching when heating the temperature above the critical point, and tempering at 500 ℃ ~ 650 ℃. Metallography after heat treatment is tempered sorbite. This organization has good match of strength, plasticity and toughness.
Most hardened and tempered steel is carbon alloy structure, yield strength is 490 ~ 1200Mpa. The hardened and tempered steel, which is characterized by its excellent weldability, is low-carbon alloy structural steel. Its yield strength is generally 490 ~ 800Mpa, which has high plasticity and toughness. A small number of precipitation hardening hardened and tempered steel, the yield strength can be 1400Mpa above, is a high strength and ultra-high strength hardened and tempered steel.
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Post time: 12-26-2017