There are several reasons why the mold bursts:

1. The mold material is not easy to be broken in subsequent processing.

2. Heat treatment: improper quenching and tempering process produces deformation

3. The mold is not flat enough to produce flexural deformation.

3. Design process: the mold strength is not enough, the knife edge spacing is too close, the mold structure is not reasonable, the number of template blocks is not enough, no padding feet

4. Wire cutting is improperly handled: the wire is cut, the gap is wrong, and the angle is not cleared.

5. Selection of punching equipment: punching tonnage, insufficient punching force, too deep adjustment

6. Disposal is not smooth: no demagnetization treatment before production, no material tip; in the production there are broken needles and other springs

7. Unsatisfactory blanking: no leakage when assembling the mold, or rolling blockage, blockage

8. Production awareness: lamination stamping, positioning is not in place, no blowing tools are used, and the template has cracks and continues to produce.

Die failure form

The failure modes of the die are mainly wear failure, deformation failure, fracture failure and flaw failure. However, due to different stamping procedures and different working conditions, the factors affecting the life of the die are various. The following is a comprehensive analysis of the factors affecting the life of the die in terms of the design, manufacture and use of the die, and the corresponding improvement measures are captured.

1 stamping equipment

The accuracy of stamping equipment (such as presses) and the impact of rigid on die life are extremely important. The precision of the stamping equipment is high, the rigidity is good, and the die life is greatly improved. For example, the complex silicon steel sheet die material is Crl2MoV, which is used on ordinary open presses, and the average regrind life is 1-3 million times. On the new precision press, the re-grinding life of the die can reach 6~120,000 times. Especially for small gap or gapless die, carbide die and precision die, it is necessary to select a press with high precision and good rigidity. Otherwise, the die life will be reduced, and the chess piece will be damaged in severe cases.

2 mold design

(1) Precision of the guiding mechanism of the mold. Accurate and reliable guiding, to reduce the wear of the working parts of the mold, to avoid the impact of convex and concave molds, especially the gapless and small gap blanking die, composite die and multi-station progressive die are more effective. In order to improve the life of the mold, it is necessary to correctly select the guiding form and determine the accuracy of the guiding mechanism according to the requirements of the nature of the process and the accuracy of the parts. In general, the accuracy of the guiding mechanism should be higher than that of the convex and concave molds.

(2) Geometric parameters of the die (convex, concave die). The shape of the convex and concave molds, the fit clearance and the fillet radius not only have a great influence on the forming of the stamping part, but also have a great influence on the wear and life of the mold. For example, the matching clearance of the mold directly affects the quality of the blank and the life of the mold. For higher precision requirements, a smaller gap value should be selected; otherwise, the gap can be appropriately increased to improve the life of the mold.

3 stamping process

(1) Raw materials for stamped parts.

In actual production, due to the excessive thickness tolerance of raw materials for external pressure parts, fluctuations in material properties, poor surface quality (such as rust) or unclean (such as oil stains), the wear of the working parts of the mold is intensified, and it is easy to collapse. as a result of. To this end, it should be noted that: 1 as far as possible using stamping process good raw materials to reduce the stamping deformation force; 2 should strictly check the raw material's grade, thickness and surface quality before stamping, and wipe the raw materials, if necessary, the surface should be removed Oxide and rust; 3 According to the stamping process and the type of raw materials, softening treatment and surface treatment may be arranged as necessary, and a suitable lubricant and lubrication process may be selected.

(2) Layout and edging.

Unreasonable reciprocating feed patterning and too small edge values often cause sharp wear of the mold or bruises on the convex and concave molds. Therefore, in consideration of improving the use of materials, it is necessary to reasonably select the layout method and the edge value according to the processing batch size, quality requirements and mold matching gap of the parts to improve the life of the mold.

4 mold materials

The influence of mold materials on the life of the mold is a comprehensive reflection of the material type, chemical composition, microstructure, hardness and metallurgical quality. Die life of different materials often varies. To this end, there are two basic requirements for the die working part materials: 1 the material should have high hardness (58~64HRC) and high strength, high wear resistance and sufficient toughness, small heat treatment deformation, certain The hardness is 2; the process performance is good. The processing and manufacturing process of die working parts is generally complicated. Therefore, it must have adaptability to various processing techniques, such as forgeability, machinability, hardenability, hardenability, quench crack sensitivity and grinding processability. Generally, according to the material characteristics of the stamping parts, the production batch, the precision requirements, etc., the mold materials with excellent performance are selected, taking into consideration the processability and economy.

5 hot processing technology

Practice has proved that the hot processing quality of the mold has a great influence on the performance and service life of the mold. From the analysis and statistics of the causes of mold failure, it is known that the "accident" of mold failure caused by improper heat treatment accounts for more than 40%. The quenching deformation and cracking of the working parts of the mold, and the early fracture of the working process are all related to the hot working process of the tool.

(1) Forging process, which is an important part in the manufacturing process of mold working parts. For molds of high alloy tool steels, technical requirements are often imposed on metallographic structures such as material carbide distribution. In addition, the forging temperature range should be strictly controlled, the correct heating specification should be established, the correct forging force method should be used, and the post-forging slow cooling or timely annealing should be carried out.

(2) Preparatory heat treatment. Pre-heat treatment processes such as annealing, normalizing or quenching and tempering should be used depending on the materials and requirements of the mold working parts to improve the structure, eliminate the structural defects of the forged blank, and improve the processing technology. The high-carbon alloy die steel can eliminate the reticulated secondary cementite or chain carbide after appropriate preliminary heat treatment, so that the carbide is spheroidized and refined, and the uniformity of carbide distribution is promoted. This is beneficial to ensure the quality of quenching and tempering and improve the life of the mold.

(3) Quenching and tempering. This is the key link in the heat treatment of the mold. If the superheat occurs during quenching, not only will the workpiece cause greater brittleness, but also cause deformation and cracking during cooling, which seriously affects the life of the mold. Special care should be taken to prevent oxidation and decarburization during die quenching. The heat treatment process specification should be strictly controlled. Vacuum vacuum heat treatment can be used if conditions permit. After quenching, it should be tempered in time, and different tempering processes should be adopted according to technical requirements.

(4) Stress relief annealing. The working parts of the mold shall be subjected to stress relief annealing after roughing, with the purpose of eliminating internal stress caused by roughing, so as to avoid excessive deformation and cracking caused by quenching. For molds with high precision requirements, it needs to be subjected to stress-relieving and tempering after grinding or electric machining, which is beneficial to stabilize mold precision and improve service life.

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