What are the differences between cold forging quality and hardness at home and abroad?

Under the same other conditions, the preload of cold forging die with small (large) interference coefficient is smaller (larger). The die produced by domestic cold forging manufacturers will show the failure of the die core out of the die sleeve, which may be related to the small interference coefficient or the non guarantee of processing scale. Japanese manufacturers choose the cold pressing cooperation of conical surface, and the interference coefficient is 0.85%. Compared with 1.3% ~ 1.5% selected by Russia, the data used by Japanese manufacturers are low.

Cold forging die hardness

Domestic cold forging manufacturers choose YG20C, Cr12MoV and Cr12, while Japanese cold forging manufacturers choose YG15 and DC53. The former has slightly higher strength and lower hardness, while the latter has the opposite. Because of high hardness and good wear resistance, this is another reason for the high die life in Japan. The hardness of high carbon alloy steel is 60 ~ 62Hrc, while the hardness of die sleeve is not more than 42hrc.

Surface processing quality

The grinding and polishing quality of the external surface of the die core of domestic cold forging manufacturers is poor, while the grinding and polishing quality of the external surface of the die core of Japanese cold forging manufacturers is good, and the overall surface roughness is Ra0.32 ~ ra0.16 μ m. Ra0.08 μ m。 The external surface roughness of the mold core has an impact on the service life of the mold. The poor surface roughness, especially the presence of depressions, holes or cracks on the surface, will be the origin point of pressure concentration and cracking, which will lead to premature cracking and failure of the mold core. The surface roughness of the inner hole of the mold core has a greater impact on the service life.