The quality of cold work moulds will directly affect the quality of their products. The life of the mould determines the production cost and economic benefits of the parts. There are many factors that affect the cold work mould. Therefore, the failure modes of cold work die are also various. According to actual production experience, effective preventive measures are proposed for several basic failure modes of cold work moulds.
For early failure moulds, there are mainly three types of failure:
1. Fracture failure: including plastic fracture failure, fatigue fracture failure, creep fracture failure, low stress brittle failure, etc.;
2. Deformation failure: including excessive elasticity and Plastic deformation failure;
3. Surface damage failure: including wear failure, corrosion failure, surface fatigue (pitting or peeling) failure, etc.
The harsh working conditions make the service life of cold work moulds much shorter than other moulds. Therefore, in order to prolong the service life of cold work moulds, reduce costs, and improve economic benefits, it is necessary to find out the root cause of mould failure and take effective measures to solve them.
1. Fracture: This is a common form of damage to cold work moulds*, mainly caused by the load exceeding the strength limit of the mould material or the stress concentration of the mould. For example: the punch is broken, the die and the fastening ring are cracked, the ejector rod is broken, and the insert is fatigued and cracked.
2. Deformation: Due to the large load on the working mould that acts during cold forming, the working mould that directly bears the pressure will produce certain elastic or plastic deformation, making the mould unusable and scrapped. For example: the elastic expansion of the concave mould cavity, the upsetting and bending of the punch, the upsetting of the ejector rod, the collapse of the center of the cushion and other deformations.
3. Wear: Due to the lubrication of the blank, the softening treatment, and the heat treatment strength of the mould, the cold work mould is the same as other moulds, and the early wear and tear of the cavity surface often fails. Such as metal adhesion, pitting, spalling or sharp changes in size on the surface of the ligament working surface.
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.