The process of forging processing technology is usually composed of the following steps, namely blanking, heating, forming, cooling after forging, pickling and heat treatment after forging. In the casting process, if the technology is not correct, a series of forging defects will be produced. The heating technology includes furnace loading temperature, heating temperature, heating speed, holding time, furnace gas composition, etc. If the heating is not appropriate, for example, the heating temperature is too high and the heating time is too long, it will lead to defects such as decarburization, overheating, and overburning. For billets with large cross-sectional dimensions, poor thermal conductivity and low plasticity, if the heating rate is too fast and the holding time is too short, the temperature distribution is usually uneven, resulting in thermal stress and cracking of the billet. Forgings for pressure vessels describe the casting forming technology, including the deformation method, deformation degree, deformation temperature, deformation speed, stress condition, love brother of the tool and smooth conditions, etc. Average, various cracks, folds. Cold wave, eddy current, as-cast tissue residue, etc. In the cooling process after forging, if the technology is not appropriate, it can lead to cooling cracks, white spots, reticulated carbides, etc. The cooling process of wheel forgings mainly includes cooling method and cooling time. Commonly used cooling media are water, oil and air. The cooling capacity and characteristics of these media greatly influence the cooling process. Among the three cooling mediums, water, oil and air, water has strong cooling capacity. The circulation and agitation of water further improve the cooling capacity, and the cooling capacity of water spray is more intense.
Forgings for pressure vessels say that the water temperature rises, which reduces the cooling capacity in the high temperature stage and does not change much in the low temperature stage, so the water temperature of the chilled forgings cannot be increased. Impurities in the water will greatly change the cooling capacity of water, and the cooling capacity of water varies from place to place. The cooling capacity of brine is greater than that of water. The cooling capacity of oil is less than that of water (especially in the low temperature stage), and the difference is 28 times larger. In most cases, fast cooling is required at high temperatures to ensure hardenability, and slow cooling at low temperatures is required to reduce structural stress. The method of using water quenching and oil cooling in production is to use the feature that the cooling ability of water is strong at high temperature, and the cooling ability of oil is weak at low temperature, and the above goal is achieved. Changes in temperature have little effect on the cooling capacity of the oil, so the oil can still be used at elevated temperatures. Forgings for pressure vessels describe that the oil temperature in general production is between 20°C and 80°C. When the oil temperature is low, the viscosity is large, and the disadvantage of uneven cooling is easy to occur. The circulation of the oil also has little effect on its cooling capacity. The main purpose of circulating the oil or moving the workpiece up and down in production is to cool the workpiece evenly and prevent the local oil temperature from rising too high. The cooling capacity of air is very low (especially at low temperatures). The cooling capacity of moving air and still air is very different. The cooling capacity of water, oil and air has a certain range of limitations, which cannot fully meet the requirements of forgings for different cooling rates, so spray cooling is being widely developed and adopted.