When the above-mentioned defects occur in the mould par […]
When the above-mentioned defects occur in the mould parts, qualified fastener products cannot be formed, which will inevitably affect the production plan of the enterprise.
In order to prevent early failure of the mould and effectively extend the service life of the mould, corresponding preventive measures are mainly taken from the following aspects.
1. Mould material
Since the cold-worked mould bears a large unit extrusion force, high-performance mould materials with high strength, good toughness and good wear resistance should be selected; because the working conditions of the convex mould are more susceptible to eccentric force than the concave mould, the convex The wear resistance of the mould material should be higher than that of the concave mould material.
2. Heat treatment
mould heat treatment includes: timely tempering of cold-worked die blank after forging to refine crystal grains, tempering after rough machining to eliminate stress, and stress-relieving low-temperature tempering after electric spark and wire cutting. Experience has shown that moulds with a diameter of ≤80mm should be directly machined with bar stock, without forging, because improper forging can cause defects such as over-sintering, coarse crystals, and segregation.
If the quenching cooling rate is too fast and the swimming temperature is too low, the mould is prone to quenching cracks. If the tempering temperature is too low and insufficient, the residual stress in the quenching process will not be eliminated, the toughness of the mould will be reduced, and early fracture will easily occur.
3. Mould design
The structure of the cold work mould must have sufficient strength, rigidity, reliability and good guidance, but the unreasonable structure of the mould will directly affect the service life of the mould. The working part of the mould should be designed with a large enough fillet radius to avoid stress concentration caused by sharp corner transition. The width of the ligament should be designed reasonably according to the metal flow condition to minimize the friction force, generally between 1.5-3.5.
4. Mould processing
In the die cutting process, the following measures should be taken; improve the surface roughness, the micro-crack marks formed by grinding, the transition part should be smooth, and the knife marks and small defects cannot be processed organically to prevent stress concentration during use and cause cracks.