How To Prevent Mold Cracking

- Aug 18, 2018-

4. Mold material


The material should have high hardness (58~64HRC) and high strength, high wear resistance and sufficient toughness, small heat treatment deformation, certain thermal hardness and good process performance.


5. The hot processing quality of the hot working process has a great influence on the performance and service life of the mold.


(1) Forging process. This is an important part of the manufacturing process of mold work parts. The forging temperature range should be strictly controlled, the correct heating specification should be established, the correct forging force method should be used, and the post-forging slow cooling or timely annealing should be carried out.


(2) Preparatory heat treatment. Pre-heat treatment processes such as annealing, normalizing or quenching and tempering should be used depending on the materials and requirements of the mold working parts to improve the structure, eliminate the structural defects of the forged blank, and improve the processing technology.


(3) Quenching and tempering. This is the key link in the heat treatment of the mold. Special care should be taken to prevent oxidation and decarburization during die quenching. The heat treatment process specification should be strictly controlled. Vacuum vacuum heat treatment can be used if conditions permit. After quenching, it should be tempered in time, and different tempering processes should be adopted according to technical requirements.


(4) Stress relief annealing. For molds with high precision requirements, it needs to be subjected to stress relief and tempering after grinding or electric machining, which is beneficial to stabilize mold precision and improve service life.


6. Control of wire cutting metamorphic layer


The die edge is mostly processed by wire cutting. Due to the thermal effect and electrolysis of the wire cutting process, a certain thickness of the metamorphic layer is produced on the surface of the die, resulting in a decrease in surface hardness and microcracking, which causes the die of the wire cutting process to be prone to early wear and directly affect the punching clearance of the die. Keep and the edge is easy to chip and shorten the life of the mold. Therefore, a reasonable electrical standard should be selected in the online cutting process to minimize the depth of the metamorphic layer.