In many occasions, people use more alloy steel instead of carbon steel. The reasons are mainly as follows.
(1) Poor hardenability of carbon steel
After carbon steel is quenched with water, its critical quenching diameter is 15-20mm. For parts with a diameter larger than 20mm, it is impossible to quench through water quenching, and the comprehensive mechanical properties of the whole cross section can not be guaranteed. Therefore, for demanding large parts, carbon steel is certainly not applicable. The alloy steel with high hardenability, can be used for the manufacture of large cross-section, the shape of complex parts.
(2) Low temperature strength of carbon steel, red hardness is poor
Carbon steel at temperatures above 200 ℃, the intensity and hardness will soon be reduced. The alloy steel after tempering good stability. Red hard, can work at higher temperatures.
(3) Carbon steel can not achieve good overall performance
For example, when tempering treatment is attempted to obtain good overall performance, the toughness is lower if higher strength is to be ensured and the strength is lower if better toughness is to be ensured. This is due to the poor stability of carbon steel tempering. Therefore, the overall performance of carbon steel obtained alloy steel is far worse, that is, alloy steel has good toughness.
(4) Carbon steel does not have special properties
For example, the requirements of high temperature hardness or tension, oxidation resistance, corrosion resistance, special electricity, magnetic properties, can not be obtained with carbon steel, steel can only be selected to meet the above requirements.
