Factors affecting the mold

The use of a wide range of molds, different working conditions and stress conditions, mold structure, mold materials, mold manufacturing, mold working conditions (including assembly and operation) are the main factors affecting mold failure. The failure of a mold may be caused by a variety of factors.

1. Effect of mold structure
Mold structure includes mold geometry such as fillet radius, geometry angle (face shape of punch, variation of die taper and cross section), structure form (integral structure, combined structure, prestressed insert structure), mold clearance, structure Stiffness and so on.

The rationality of the mold structure has a great influence on the bearing capacity of the mold. Reasonable mold structure can make the mold work evenly, it is not easy to eccentric load, the stress concentration is small, it is not easy to produce early failure; Unreasonable mold structure may cause serious stress concentration or high working temperature, thus deteriorating the working conditions of the mold , leading to early failure of the mold.

2. Influence of mold material
1) Mechanical properties of mold materials. Mold materials should generally meet the requirements of the mold for plastic deformation resistance, fracture resistance, fatigue resistance, hardness, wear resistance, cold and heat fatigue resistance and other performance requirements. If it fails to meet the requirements, an early mold failure can occur. For example, under cyclic load, if the fatigue resistance of the mold material is low, after a certain stress cycle, fatigue cracks may be initiated, and gradually expand until the mold fracture failure.

2) Metallurgical quality of die steel. The metallurgical quality of die steel has a great influence on the failure mode of the die. Non-metallic inclusions in steel, segregation, central porosity, white spots and other defects, can reduce the toughness, fatigue and cold and heat fatigue resistance of steel, causing early failure of the mold, such as cracking, splitting, breaking, and the face of the Depression and so on.

3. Influence of mold manufacturing process
Mold manufacturing process includes forging, machining, heat treatment and so on. Some mold processing requires all of the above processes. The processing quality of each process will affect the damage process and failure modes of the mold in varying degrees.

If the forging process is unreasonable, it can not reach the goal of breaking the grains, improving the directionality, increasing the density of the steel, etc., or even causing defects such as forging cracks; if the sharp angle or high surface roughness value occurs during machining, machining is left. Knife marks will easily cause fatigue cracks in these areas. Improper grinding, easy to burn the mold surface or grinding cracks; if not properly heat treatment, it may lead to heat treatment defects, such as quenching temperature is too high, it will cause the steel to overheat, and even burn, the mold is prone to chipping or early fracture, The quenching temperature is too low, it is difficult to ensure that there are enough alloy elements dissolved in the matrix, the mold is easy to produce early deformation, collapse or thermal fatigue cracks. Quenching cooling rate is too fast, it is prone to quenching cracks, easy to produce early fracture in the use of the mold.

4. Influence of the working conditions of the mold
The working conditions of the mold are related to the following factors: the characteristics of the equipment, the material, shape, accuracy, and temperature of the material to be processed, the cooling and lubrication conditions of the mold, the preheating of the mold, and the elimination of the working stress. All of these factors have an effect on the failure mode of the mold.