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Compared with carbon tool steel and high carbon alloy steel, the service life of cemented carbide die used in screw thread fastener production is improved by several times to ten times.Therefore, it is widely used in cold heading production such as screws under M5.But compared with foreign cemented carbide mould, domestic mould has obvious gap.For example: semi-round head screw or countersunk head cross groove screw with carbide die, the life of the Japanese mold can reach 7 to 9 million pieces, domestic mold life for 2 to 3 million pieces, and the quality is not stable.Detection comparison, found that there are many differences.

Structure shape and size, the main reason for the low service life of domestic mold is not the size proportion. The internal hole and the outer circle of the mold core designed by domestic manufacturers are cylindrical, and the bottom of the mold core and the bottom of the inner hole of the mold sleeve are flat. This structure is simple and easy to process.When using cold insert, because there is no guide Angle, easy to deflect the pressure, squeezing the surface of the inner hole of the die sleeve, and even the core of the die will produce micro-cracks, crack, making the quality of pressing insert difficult to be stable.

The contact part between the inner hole and the core of the die cover made by Japanese manufacturer adopts the matching structure of double taper and double convex surface.However, there is a guiding Angle, is conducive to ensure the quality of the press insert.Japanese mold core