1, the large section of the mold, steel hardenability is poor, such as the selection of a large mold of low hardenability steel.
2. In the original microstructure of die steel, the segregation of carbide is serious or the structure is thick.
3, the die forging process is not correct, after the forging did not stop very good spheroidizing annealing, so that the mold steel ball bad organization.
4, the surface of the mold is not removed in addition to the net annealing or quenching of the carbon layer.
5, the mold quenching temperature is too high, after quenching residual austenite amount is too much; or quenching temperature is too low, lack of heat preservation time, so that the die steel phase change is not complete.
6, die quenching heating after cooling speed through the slow, classification and isothermal temperature is too high or too long time, quenching cooling medium choice.
7, alkali bath water is too little, or quenching cooling medium containing impurities too much, or quenching cooling medium aging.
8, after quenching quenching of the cooling medium, the temperature is too high.
9, tempering and tempering temperature is not too high.