After forgings are forged in a medium frequency induction heating furnace, how should the cooling specifications be determined?

After the forging is forged and formed in the medium frequency induction heating furnace, the key to determining the cooling specification is to select the appropriate cooling rate. Usually, the appropriate cooling rate can be determined by referring to relevant information based on the chemical composition, structural characteristics, original state, cross-sectional size and other factors of the billet.

Generally, forgings made of steel have a greater cooling rate after forging than forgings made of steel ingots. Forgings with small cross-sections have a cooling rate after forging that is faster than forgings with large cross-sections.

(1) Cooling specifications for small and medium-sized carbon steel and low alloy steel forgings: Generally speaking, the simpler the chemical composition of the billet, the faster the cooling rate after forging; vice versa. Therefore, air cooling is used for small and medium-sized carbon steel and low alloy steel forgings after forging.

(2) Cooling specifications for alloy steel forgings: For alloy steel forgings with complex alloy compositions, pit cooling or furnace cooling should be used after forging.

(3) Cooling specifications for tool steel and bearing steel: For steel with higher carbon content (such as carbon tool steel, alloy tool steel and bearing steel, etc.), in order to prevent the precipitation of network carbides at the grain boundaries, after forging First use air cooling, blast or spray to quickly cool to 700°C, and then put the forgings into a pit or furnace to cool slowly.。

(4) Cooling specifications for non-phase change steel: For non-phase change steel (such as austenitic steel, ferrosite steel, etc.), since there is no phase change during the cooling process of forgings, rapid cooling can be used. At the same time, after medium-frequency heating furnace forging, rapid cooling is also required in order to obtain a single-phase structure and prevent the ferrite from becoming brittle at around 475°C. Therefore, forgings are usually air-cooled after forging.

(5) Cooling specifications for air-cooled self-quenching steel: For this kind of steel, in order to prevent white spots from being produced during the cooling process, furnace cooling should be carried out according to certain cooling specifications.

Forgings should not only be cooled according to specifications after final forging, but sometimes also need to be cooled during the forging process using an intermediate frequency heating furnace, which is called intermediate cooling. Intermediate cooling is used for forgings that are not completely forged after heating (such as multi-fire forging of large crankshafts), forgings that require local heating, and forgings that require rough flaw detection or cleaning of defects during the forging process. The determination of the intermediate cooling specifications for forgings is the same as the final cooling specifications.