How to carry out the heat treatment of white cast iron ?

How to carry out the heat treatment of white cast iron ?

Iron castings manufacturers generally need to heat treat the castings during production. As a basic process of processing, heat treatment is also an important process of material forming in casting production. Compared with other cast irons, white cast iron has high hardness and brittleness, and can not be directly cut, so it needs annealing treatment to be put into use. 

So, what are the ways of heat treatment of white cast iron ?

1.  When the gray cast iron is quenched by the foundry, the surface of the gray cast iron needs to be treated first, and then the gray cast iron is heated to 900 °C for heat preservation, and then the cast iron is put into the 280 ~ 300 °C nitrate solution. After 90 minutes of isothermal preservation, it is taken out and cooled at normal temperature. This heat treatment method is called isothermal quenching, which is suitable for iron castings with high requirements for wear resistance and impact resistance. The comprehensive mechanical properties of iron castings are guaranteed by quenching.

2. Because the structure of white cast iron is relatively stable, the casting internal stress is large. If the residual internal stress is not eliminated in time during the processing, it is likely to crack during the vibration process. Therefore, in order to effectively remove the internal stress of the casting, the temperature should be appropriately increased during annealing. Generally, the temperature should be kept at 800 ~ 900 °C, and the temperature in the furnace should be reduced to 100 ~ 150 °C after the heat preservation. 

3. For some hardenability alloy white cast iron, there are a lot of martensite in cast iron, but the cementite is less, the hardness is very high, the parts made of this kind of material need to be machined, the softening annealing process must be used to make the martensite into pearlite, so that the hardness of cast iron can be reduced to the degree of processing.