Heating defects of precision stamping parts and preventive measures

The defects that are easily generated when the precision stamping blanks are heated and their prevention methods are as follows.　　(1) Oxidation. At high temperatures, the surface metal of the blank and the oxidizing gases in the furnace gas (oxygen, carbon dioxide, water vapor, sulfur dioxide, etc.) chemically react to form oxide scale, causing metal burnout. This phenomenon is called oxidation. The measure to reduce oxidation is to use rapid heating as much as possible on the premise of ensuring the heating quality and avoid the metal staying for too long at high temperature.　　 (2) Decarburization. During the heating process, the carbon on the surface of the metal reacts chemically with carbon dioxide, water vapor, oxygen, etc. in the furnace gas, and the phenomenon that causes the carbon content of the surface to decrease is called decarburization.　　(3) Overheating. When the heating temperature of the billet is too high or the holding time at high temperature is too long, the internal grains will grow up quickly and become coarse grains. This phenomenon is called overheating. Overheated blanks are prone to cracks during forging, and the mechanical properties are deteriorated. (4) Overburning. The heating temperature exceeds the initial forging temperature and is too close to the melting temperature of the metal. The grain boundary oxidizes and melts, so that the bonding force between the grains is lost. Once forged, it will break. Overburning. When carbon steel is overburned, dazzling incandescent sparks will be emitted due to the oxidation of the grain boundaries. Overburning defects cannot be saved, so overburning is not allowed during heating.　　(5) Crack. Metal expands in volume after being heated, and the higher the temperature, the greater the expansion. If the heating speed is too fast, the temperature difference between the inside and outside of the blank is large, the expansion is inconsistent, and cracks may occur. In order to prevent cracks, strictly formulate and observe the correct heating rate.