7 Causes and treatment of defects in die heat treatment(2)

//7 Causes and treatment of defects in die heat treatment(2)

7 Causes and treatment of defects in die heat treatment(2)


When mold manufacturing, you may know some about die heat treatment as followings:

Fourth, decarbonization

Decarbonization is result of that the steel in the heating or insulation, due to the role of the surrounding atmosphere, the part of the surface layer of carbon all or part of the loss of the phenomenon and reaction. Decarburization of steel will not only result in insufficient hardness, quenching crack and heat treatment deformation and chemical heat treatment defects, but also on fatigue strength, wear resistance and mold performance also has a great impact.

Fifth, the electrical discharge caused by the crack

In the mold manufacturing, the use of EDM (electric pulse and wire cutting) is more and more commonly used in processing methods, while with the extensive application of EDM, the defects caused by a corresponding is increasing.

Since the electric discharge machining is a processing method of melting the mold surface by the high temperature generated by the discharge, a white EDM layer is formed on the machined surface thereof and a tensile stress of about 800 MPa is generated. Thus, during the electrical machining process of the die often appear defects such as deformation or cracks.

Sixth, lack of toughness

The reason for the lack of toughness may be quenching temperature is too high, and the holding time is too long cause grain coarsening caused, or because there is no to avoid tempering brittle area tempering.

Seven, grinding cracks

When the workpiece has a large number of retained austenite, the role of heat in the grinding, the occurrence of tempering transformation, resulting in tissue stress, resulting in workpiece cracking. The preventive measures are: quenching after repeated cryogenic treatment or repeated tempering (mold tempering is generally 2-3 times, even cold work with low-alloy tool steel, as well), to minimize the amount of residual austenite.