What is the heat treatment of cast steel we often talk […]
What is the heat treatment of cast steel we often talk about?
Heat treatment is a method of processing steel castings often used in casting production. There are casting defects such as porosity, cracks, and uneven assembly in the steel castings in the as-cast state. The strength and toughness of the steel castings are greatly reduced. Heat treatment can improve the mechanical properties of the steel castings, so as to meet the conditions of use and extend the service life.
The heat treatment method is simple, convenient, and effective, and the required equipment is not complicated, so it has high use value and is widely used.
1. Annealing and normalizing: the common point is to heat steel to a certain temperature, such as 45 steel heating temperature to 820 ℃. But the cooling method is different. Annealing adopts slow cooling, such as burying in sand or ash or gradually cooling with furnace temperature, to eliminate internal stress. Normalizing is to expose the workpiece to air to cool. In contrast, normalizing has a faster cooling rate, in order to obtain a refined structure. The hardness and strength of the workpiece are higher than that of annealing. 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, when 45 steel is heated to about 830°C, it is quickly put into water, oil or salt solution to cool, so that the temperature of the workpiece can be quickly cooled to obtain higher hardness and strength, which is a common and important heat treatment method. The level of carbon content in steel determines the hardness of the workpiece after quenching. The higher the carbon content, the greater the hardness after quenching. But if the quenching temperature is too high, it will cause cracks in the workpiece
3. Tempering: Eliminate internal stress generated during