Performance characteristics of high carbon steel
1. High hardness (HRC60-65) and better wear resistance can be obtained after heat treatment.
2. The hardness is moderate under the annealed state, and it has good machinability.
3. Raw materials are easily available and production costs are low.
The disadvantages are:
1. Poor heat rigidity. When the working temperature of the tool is higher than 200 ℃, its hardness and wear resistance will decrease sharply.
2. Low hardenability. The diameter of complete hardening when water quenching is generally only 15-18mm; the maximum diameter or thickness (95% martensite) of complete hardening when oil quenching is only about 6mm, and it is easy to deform and crack. The hardness and strength of high carbon steel mainly depend on the amount of solid solution carbon in the steel, and increase with the increase of the amount of solid solution carbon. When the solid carbon content exceeds 0.6%, the hardness after quenching no longer increases, but the amount of excess carbides increases, the wear resistance of the steel slightly increases, and the plasticity, toughness and elasticity decrease. For this reason, different steel grades are often selected according to the use conditions and the strength and toughness of the steel. For example, for making springs or spring-loaded parts that are less stressed, a lower carbon 65 steel can be selected. Generally high carbon steel can be produced by electric furnace, open hearth furnace, oxygen converter. When high quality or special quality is required, electric furnace smelting plus vacuum self-consumption or electroslag remelting can be used. During smelting, the chemical composition is strictly controlled, especially the content of sulfur and phosphorus. In order to reduce segregation and improve isotropic properties, the ingot can be subjected to high-temperature diffusion annealing (especially important for tool steels). During hot working, the temperature for stopping forging (rolling) of hypereutectoid steel is low (about 800 ℃). After the forging and rolling, the precipitation of coarse network carbides should be avoided. Slow cooling should be taken below 700 ℃ to prevent thermal stress Causes cracks. Prevent surface decarburization during heat treatment or hot working (especially important for spring steel). There must be sufficient compression ratio during hot working to ensure the quality and serviceability of steel.