The cooling modes of large forgings mainly include water cooling (including water spray cooling), oil cooling, air cooling (natural air cooling and air blast cooling), gap cooling (water air, water oil, oil air) and spray cooling. The commonly used quenching media for large forgings are water, oil and air.
Water cooling: due to the strong cooling capacity of water, the cooling speed of the surface and center of the forging is very different, resulting in a large temperature on the forging section. For example, the section of ordinary carbon steel and low alloy steel shall not be greater than 200mm, and some plants require that the water cooling method shall not be greater than 300 or 400mm.
Oil cooling: It is a widely used method, and the cooling capacity of oil is smaller than that of water.
Air cooling: Although air cooling is relatively safe, in order to achieve the required mechanical properties, it is often necessary to improve the hardenability of steel, so it is necessary to use alloy steel with more alloy elements, which will greatly increase the cost.
Gap cooling: the cooling capacity of water cooling, oil cooling and air cooling is limited within a certain range, so it can not fully meet the cooling requirements of large forgings with various diameters and different steel grades. Combining several cooling methods is an effective way to solve this problem. 1. Water space gap cooling: complex operation, difficult to control; 2. Water oil gap cooling: this cooling method is widely used for small forgings made of medium carbon steel and medium carbon alloy steel; 3. Oil space gap cooling: it can be used for some important alloy steel large forgings. The first oil cooling time must ensure spray cooling: spray cooling is to use compressed air to blow to the water column at a certain angle to change the direction of the water and make it fog, and then use atomized water and wind to cool the slowly rotating shaft parts. The water pressure and wind pressure can be adjusted according to requirements. Some factories also set water spray cooling devices on the spray device, In this way, the cooling speed of large forgings can be adjusted in a wide range from water cooling to natural air cooling.