How is Gray Cast Iron Heat Treated?

As a Grey Iron Casting Company, share it with everyone. After the heat treatment of gray cast iron, it can only change the matrix structure, not the shape of graphite, so it is impossible to significantly improve the mechanical properties of gray cast iron.

As a sandpaper sponge, share it with everyone. After the heat treatment of gray cast iron, it can only change the matrix structure, not the shape of graphite, so it is impossible to significantly improve the mechanical properties of gray cast iron. The heat treatment of gray cast iron is mainly used to eliminate the internal stress and white structure of the casting, stabilize the size, improve the cutting performance, and increase the surface hardness and wear resistance.

Grey Cast Iron Casting

Relieve internal stress annealing

It is used to eliminate the casting stress caused by uneven cooling of the casting during the solidification process, and prevent the casting from deformation and cracks. The process is to heat the casting to 500-600°C, and then slowly cool it with the furnace to below 150-200°C after holding it for a period of time, and then air cooling. Sometimes the casting is placed in a natural environment for a long period of time to relax the internal stress of the casting. This method is called "natural aging", and large gray iron castings can use this method to eliminate casting stress.

Graphitization annealing

In order to eliminate the white mouth structure, reduce the hardness, and improve the cutting performance. The method is to heat the casting to 850～900℃, keep it for 2～5 hours, then slowly cool it to 400～500℃ with the furnace, and then air-cool it out of the furnace to decompose the cementite to form graphite during the heat preservation and slow cooling process.

Surface hardening

Improve surface hardness and extend service life. For example, the working surface of gray cast iron parts such as the surface of the machine tool guide rail and the inner wall of the cylinder liner of the internal combustion engine needs to have higher hardness and wear resistance, and the surface quenching method can be used. Commonly used methods are high (medium) frequency induction heating surface quenching and contact resistance heating surface quenching.

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