How to extend the processing life of cold heading molds

Beginning in 1992, the three-station mold with a very low life of the cold heading machine was ground and polished and then coated with titanium nitride. The mold life can reach up to (50,000 ~ 290,000) of cold heading rollers. Bearing tapered roller cold heading molds are generally made of Crl2MoV alloy tool steel and used directly after quenching and grinding. Since the hardness after quenching is about HRC (58S～62), the roughness of the inner hole of the workpiece after grinding can only reach. Ra(1.6～0.8)μm, in the process of use, there will be adhesive wear and strain on the surface of the formed roller, resulting in the average life of a mold can only upset about 3000 grains, which becomes the first in production. Big problem.

Process features: Grinding and polishing the working cavity of the mold, reducing the roughness of the working surface, and reducing the possibility of the roller bonding to the mold in the cold heading; using PVD coating titanium nitride, the process temperature is about 350°C , Does not change the hardness and metallographic structure of the substrate; titanium nitride has low affinity with metal and high anti-bonding temperature, which increases the surface hardness of the mold from HV850 to HVl950, which is equivalent to increasing HRC20, which greatly improves the wear resistance of the mold; nitrogen The friction coefficient of titanium and iron is small, which is 1/5 of the friction coefficient of iron and iron, which can greatly reduce the stickiness (Guide: China's CNC machine tools urgently need to be alert to seize the mold equipment market)

Knot and strain; since the coating thickness is only (3～4)μm, it has little effect on the accuracy of the mold and can be performed after finishing.

In order to improve the service life of the mold, the working cavity of the mold is ground and polished, and then a layer of titanium nitride is applied by the PVD process method to improve the surface hardness, wear resistance and adhesion resistance of the mold to improve The service life of the mold. Later, in the large batch of cold heading bearing rollers, all the molds coated with titanium nitride were used for grinding and polishing, and the life of the mold was increased from (2~3) thousand grains to more than 10,000 grains. This can save a lot of time for mold replacement and mold manufacturing costs, and ensure normal production.

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