Mould invalidation forms

Basic forms: wear and fracture, plastic deformation. The actual working status of the mould is complicated, a variety of damage in the form of interaction, wear promoted the plastic deformation and fracture, statue deformation increased wear and fracture rate. 1 the wear between mold and billet processed rub against each other, cause the loss of the mold surface material, make the mold geometry change and not continue to serve, is the wear failure. Wear failure of blade passivation, surface edges, surface subsidence, it become the trench, peeling, sticky mould, etc. Influence factors: mould material and processed chemical composition and mechanical properties of the blank; The surface state of the mould material and blank ( Oxide film, surface treatment) ; The stamping process of pressure, temperature, speed, lubrication. Hardness of mould wear resistance depends on the mould material, especially the carbide nature, size and distribution of hardening phase and quantity. According to the wear mechanism can be divided into the abrasive wear, adhesive wear and fatigue wear, cavitation and erosion wear, corrosion and wear. 2 main fracture fracture is brittle fracture and fatigue fracture, fracture toughness, creep fracture, stress corrosion cracking. The main factors influencing the fracture: the surface of the mold shape ( Mutation grooves, easy to produce stress concentration in areas such as the sharp corners, forming cracks) , the material performance ( The metallurgical quality, fracture toughness of material) 。 3 plastic deformation when the mold under load more than mold steel yield strength, mould can produce plastic deformation, change mould geometric shapes and sizes, not for plastic deformation failure repair service again. The main failure forms cavity type hole swell, collapse, bending, upsetting. Mould of plastic deformation is mould yield process of metal materials: local stress is greater than the yield strength of mould. 3. Five factors affecting die life cause mould failure life ends for many reasons: unreasonable mold design, mold material quality is poor, mechanical processing, heat treatment system is not suitable, improper surface strengthening, the operation method is not correct, etc.