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Reason Analysis of Metal Stamping Press Mold Crack

As the stamping process is different from different working conditions such as suspended aluminum ceiling tile perforation molds, resulting in mold burst for many reasons. The following die design, manufacture and use of comprehensive analysis of the causes of mold crack, and make the appropriate improvement measures.
1. Die material is not good, easy to break in the subsequent processing
Die life of different materials are often different. To this end, working parts for the die material, put forward two basic requirements:
(1) the use of materials should have a high hardness (58-64HRC) and high strength, and has a high wear resistance and sufficient toughness, heat treatment deformation is small, there is a certain degree of thermal hardness; (2) process performance. Die manufacturing parts of the general process is more complex, and therefore must have a variety of processing technology adaptability, such as malleability, machinability, hardenability, hardenability, quenching crack susceptibility and grinding processability, etc. .
2. Heat treatment: quenching and tempering process improper deformation
Practice has proved that the quality of the hot mold processing and service life of the mold a great impact. Die from the analysis of the reasons for failure statistics show that due to improper heat treatment caused mold failure "accident" accounts for about 40%.
(1) forging process This is the work of mold parts manufacturing process is an important part. For high-alloy tool steel mold, the material is usually carbide distribution and other microstructure technical requirements.

(2) pre-heat treatment Die parts should be depending on the materials and requirements of the different annealing, normalizing or quenching and other preheating heat treatment process to improve the organization to eliminate the rough forging defects in the organization to improve the processing technology. High-carbon alloy die steel after appropriate pre-heat treatment, to eliminate reticulate secondary cementite or chain carbide, the carbide ball, refinement, and promote the uniform distribution of carbide, which is conducive to ensuring quenching, tempering Quality, improve die life.

(3) quenching and tempering This is the key to mold heat treatment. If the quenching heat generated overheating, not only will cause greater brittleness of the workpiece, but also in the cooling easily lead to deformation and cracking, seriously affecting the life of the mold. Die quenching heating should pay special attention to prevent oxidation and decarburization, should strictly control the heat treatment process specifications, conditions permitting, can be vacuum heat treatment. Quenching should be promptly tempered, and in accordance with technical requirements using different tempering process.

(4) the elimination of stress Annealing Die parts in the rough, the stress should be carried out annealing treatment, the purpose is to eliminate the roughing caused by internal stress, so as to avoid excessive deformation and crack when quenching. For the high precision molds, after grinding or machining need to go through stress-relieving tempering treatment is conducive to stabilize the mold accuracy and improve service life.

3. Mold grinding flatness is not enough, resulting in flexural deformation
The surface quality of mold parts is closely related to mold wear resistance, fracture resistance and anti-adhesion ability, which directly affect the service life of the mold, especially the surface roughness value has a great influence on the die life. If the surface roughness value is too large, in the work will produce stress concentration phenomenon, and in its peak, valley prone to crack, affecting the durability of die, but also affect the corrosion resistance of the workpiece surface, a direct impact on die life And accuracy, it should be noted that the following:

(1) During the working process of the mold, the surface phenomenon of the burned parts must be prevented, and the grinding process conditions and process methods (such as wheel hardness, grain size, coolant and feedrate) should be strictly controlled;

(2) During the processing, the surface of the work part of the mold should be prevented from leaving the macroscopic defects such as knife mark, interlayer, crack and impact scar. The existence of these defects will cause the stress concentration and become the root of the fracture, resulting in early failure of the mold.

(3) the use of grinding, grinding and polishing and other finishing and fine processing, to obtain a smaller surface roughness values, improve the service life of the mold.

4. Design process
Mold strength is not enough, blade spacing too close, the mold structure is unreasonable, the number of templates is not enough, no pad pad feet, mold-oriented are not allowed, the gap is unreasonable.
(1) nesting and take the edge of unreasonable reciprocating feed layout method, and too small take the side value, often cause rapid wear mold or convex, die bite injury. Reasonable choice of layout methods and take the edge value, in order to improve die life.

(2) the accuracy of the guide mechanism of the mold accurate and reliable guidance for the reduction of mold parts of the wear and tear, to avoid the convex and concave bite severely affected, in particular, no gap and small clearance punching mode, multi-mode and multi- Progressive mode is more effective. In order to improve the mold life, must according to the process nature and the part precision and so on request, correctly selects the guide form and determines the guide mechanism precision.

(3) mold (convex, concave die) edge geometric parameters.

5. Wire cutting process
Artificially pull line cutting, line cutting gap is not handled, not clear angle and line cut the impact of metamorphic layer.
Die cutting edge to use more wire-cutting processing. As the thermal effects of wire cutting and electrolysis, the mold surface to produce a certain thickness of the metamorphic layer, resulting in reduced surface hardness, resulting in micro-cracks, resulting in wire cutting die prone to early wear and tear, a direct impact on the mold blanking gap Maintain and edge easy chipping, shorten the service life of mold. Therefore, the line cutting process, should choose a reasonable electrical standards, to minimize the depth of metamorphic layers.

6. Punching equipment selection
Punch tonnage, punching force is not enough, transfer mode too deep.
Stamping equipment (such as press) the accuracy and rigidity of the die life is extremely important. Stamping equipment, high precision, good rigidity, die life greatly improved. For example: complex silicon steel die material is Crl2MoV, open press on the use of the average, the average re-life of 1-3 million times; the use of new precision presses, die re-life of up to 6-12 million times.

7. Stamping process
Stamping parts of the raw material thickness tolerance tolerance, material properties, surface quality is poor (such as rust) or not clean (such as oil), etc., will cause mold parts wear increased, easy chipping and other adverse consequences. To this end, it should be noted:
(1) as far as possible with good stamping process of raw materials to reduce the stamping deformation force;

(2) before stamping, should strictly check the raw material grades, thickness and surface quality, and raw materials wipe clean, if necessary, should remove the surface oxide and rust;

(3) according to the stamping process and the type of raw materials, if necessary, can be arranged softening and surface treatment, and select the appropriate lubricant and lubrication process.
8. The correct use of production operations and reasonable maintenance.
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