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Defects and preventive measures in die manufacturing process

ABIS Mold Technology Co.,Ltd Updated: Oct 17, 2018

               Defects and preventive measures in die manufacturing process

2.1 forging

   High carbon and high alloy steels, such as Cr12MoV and W18Cr4V, are widely used in the manufacture of moulds.However, the defects such as composition segregation, large and uneven carbide and uneven structure exist in different degrees of this kind of steel.To choose high carbon and high alloy steel to make the mold, the blank of the module must be formed by reasonable forging process. On the one hand, the steel can reach the size and specification of the blank of the module; on the other hand, the structure and performance of the steel can be improved.In addition, high carbon and high alloy die steel has poor thermal conductivity, and the heating speed cannot be too fast, and the heating should be uniform. In the range of forging temperature, reasonable forging ratio should be adopted.

2.2 machining

   The cutting process of the die shall strictly guarantee the radius of the rounded corners at the dimensional transition and smooth the contact between the circular arc and the straight line.If the cutting quality of the mold is poor, the mold may be damaged in the following three aspects: 1) due to improper cutting, the sharp Angle or radius of rounded Angle is too small, which will lead to serious stress concentration when the mold is working.2) if the surface after cutting is too rough, there may be defects such as knife marks, cracks and incisions, which are not only the stress concentration point, but also the place where cracks, fatigue cracks or thermal fatigue cracks are formed.3) if the decarburization layer produced by die wool during rolling or forging is not completely and uniformly removed by cutting, non-uniform hardening layer may be produced during die heat treatment, resulting in decreased wear resistance.

23 grinding

   After quenching and tempering, the mold is generally ground to reduce surface roughness.Due to too much grinding speed, grinding wheel fairly granular or poor cooling conditions were factors, mold surface caused by local overheat, cause local microstructure changes, or cause to soften the surface, the hardness is reduced, or produce the phenomenon such as high residual tensile stress, will reduce the service life of mold grinding process parameters to reduce local fever, select the appropriate grinding in May to deal with the stress condition, can effectively prevent the formation of grinding crack.There are many measures to prevent overheating and cracks in grinding, such as adopting coarse particle grinding wheel with strong cutting force or grinding wheel with poor adhesion, so as to reduce the feed amount of grinding of the mold;Select suitable coolant;250 - a - 300 ℃ tempering after grinding to eliminate stress, etc.

2.4 edm

   Application of edm technology processing die, current density of discharge area is very big, have a lot of heat, the temperature of the mold by processing area up to 10000 ℃, due to high temperature, the microstructure of heat affected zone will change and mould surface due to high temperature melting, and then quenching, fast solidification, the formation of solidified layer again.Under the microscope, the resolidification layer is bright and white with many microcracks inside.In order to extend the service life of mould can adopt the following measures: adjust edm parameters by electrolysis or mechanical grinding after the edm surface grinding method, eliminate abnormal white layer in the layer, especially to remove the microcrack. Arrange for a low temperature tempering after edm, make the abnormal layer stabilization, prevent microscopic crack propagation.

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