Heat treatment is a method of treating steel castings that is often used in casting production. There are casting defects such as pores, cracks, and uneven assembly inside the cast steel parts in the cast state, which greatly reduce the strength and toughness of the cast steel parts. Heat treatment can improve the mechanical properties of the cast steel parts, meet the use conditions, and extend the service life.
The heat treatment method is simple, convenient, and effective, and the required equipment is not complicated, so it has a high use value and is widely used.
1. Annealing and normalizing: The common point is that the steel is heated to a certain temperature, such as 45 steel heating temperature to 820℃. But the cooling method is different. Annealing is to use slow cooling, such as burying in sand, ash or gradually cooling with the furnace temperature to eliminate internal stress. Normalizing is to expose the workpiece to air for cooling. In contrast, the cooling speed of normalizing is faster, the purpose is to obtain a refined organizational structure, the hardness and strength of the workpiece are higher than annealing treatment, and normalizing is generally suitable for improving the hardness of low-carbon steel.
2. Quenching: The purpose is to improve the hardness and strength of the material, which can only be applied to medium-carbon steel or high-carbon steel workpieces. For example, 45 steel is heated to about 830℃, and then quickly cooled in water, oil or salt solution to make the temperature of the workpiece cool quickly and obtain higher hardness and strength. This is a commonly used and important heat treatment method. The carbon content in the steel determines the hardness of the workpiece after quenching. The higher the carbon content, the greater the hardness after quenching. However, if the quenching temperature is too high, the workpiece will crack.
3. Tempering: Eliminate the internal stress generated during quenching.
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