First, the analysis of the cause of the mold burst 1. The mold material is not easy to be broken in the subsequent processing 2. Heat treatment: improper quenching and tempering process deformation 3. Mold grinding flatness is not enough, resulting in flexural deformation 4. Design process: 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 without padding foot 5. Wire cutting is improperly handled: the wire is cut, the gap is not right, no clear angle is used. 6. Punching equipment selection: punch tonnage, punching force Not enough, the mold is too deep 7. The material is not smooth: no demagnetization treatment before production, no material tip; in the production, there are broken needles and other springs. 8. The material is not smooth: there is no leakage when assembling the mold. or roll blocking feces, feces blocking feet 9. awareness of production: lamination stamping, positioning is not in place, do not use blow gun, templates cracks continued production <br> <br>
Second, the failure mode <br> <br>
die die The failure modes are mainly wear failure, deformation failure, fracture failure and flaw failure. However, due to the different stamping processes and different working conditions, the factors affecting the die life 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.
Third, the impact <br> <br>
stamping equipment stamping equipment (such as press) the accuracy and rigidity of the die life is 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 6-12 thousand 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.
Fourth, the mold design 1. The guiding mechanism precision 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. Die (convex, concave mold) edge geometry parameters. 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.
Five, stamping process
1. In the actual production of raw materials for stamped parts, the wear tolerance of the working parts of the mold is intensified due to the tolerance of the raw material thickness of the external pressure parts, the fluctuation of material properties, the poor surface quality (such as rust) or the uncleanness (such as oil stain). , and easy to collapse and other adverse consequences. 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. Unreasonable reciprocating feeding and arranging method for arranging and lapping, and too small edging value will often cause sharp wear of the mold or bruises of 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.
VI Effect of
mold material <br> <br> mold material to the mold life is the type of material, the chemical composition, microstructure, hardness and other metallurgical quality comprehensive reflection of various Gangsuo. 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, and has high wear resistance and sufficient toughness, heat treatment deformation is small, there is a certain Hot hardness; 2 good process performance. The processing and manufacturing process of die working parts is generally more complicated. Therefore, it is necessary to have adaptability to various processing processes 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.
Seven, thermal processing <br> <br> proved. 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. Prepare 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 mold steel can eliminate the reticulated secondary cementite or chain carbide after proper 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 and heating, 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 should be subjected to stress relief annealing after roughing, with the purpose of eliminating the 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 relief and tempering after grinding or electric machining, which is beneficial to stabilize mold precision and improve service life.
Eight, processing surface quality
The working parts of the mold plus the surface quality have a very close relationship with the wear resistance, fracture resistance and anti-adhesive ability of the mold, which directly affects the service life of the mold. In particular, the surface roughness value has a great influence on the life of the mold. If the surface roughness value is too large, stress concentration will occur during operation, and cracks will easily occur between peaks and valleys, which will affect the durability of the die and affect the durability. The corrosion resistance of the surface of the workpiece directly affects the service life and accuracy of the die. To this end, the following matters should be noted: 1 The surface of the burned parts must be prevented during the machining process of the mold working parts, and the grinding process conditions and process methods should be strictly controlled. (such as grinding wheel hardness, particle size, coolant, feed and other parameters); 2 in the process of processing should prevent the surface of the mold work parts with knife marks. Macroscopic defects such as interlayers, cracks, and impact flaws. The existence of these defects can cause stress concentration, which becomes the root of the fracture, causing early failure of the mold. 3 Finishing and fine processing such as grinding, grinding and polishing can obtain smaller surface roughness values ​​and improve the service life of the mold.
Nine, surface strengthening treatment
In order to improve the performance and service life of the mold, the surface strengthening treatment of the mold working parts is becoming more and more widely used. Commonly used and enhanced treatment methods are: liquid carbonitriding, ion nitriding, boronizing, vanadium and spark strengthening, as well as chemical vapor deposition (CVD), physical vapor deposition (PVD) and in salt baths. The surface of the workpiece is immersed in a carbide method (TD) or the like. In addition, high-frequency quenching, surface strengthening treatment such as hydraulic pressure and shot peening are used to generate compressive stress on the surface of the working part of the mold, and the fatigue strength is improved, which is beneficial to the improvement of the life of the mold.
X. Control of the metamorphic layer
The die edge is mostly processed by wire cutting. Due to the thermal effect and electrolysis of the wire cutting process, a certain thickness of the metamorphic layer is produced on the surface of the die, resulting in a decrease in surface hardness and microcracking, which causes the die of the wire cutting process to be prone to early wear and directly affect the punching clearance of the die. Keep and the edge is easy to chip and shorten the life of the mold. Therefore, a reasonable electrical standard should be selected in the online cutting process to minimize the depth of the metamorphic layer.
　 XI, use and reasonable maintenance
In order to protect normal production, improve the quality of stamping parts, reduce the cost, and extend the life of the die, the mold must be properly used and properly maintained, and the “three-check†system of the die (check before use, check during use and check after use) and do Good die and maintenance work. The main work includes the correct installation and debugging of the mold; strictly control the depth of the punch into the die; control the bottom end of the upper die of the process of correcting bending, cold extrusion, shaping, etc.; timely re-grinding, polishing the edge of the chess Pay attention to keeping the chess piece clean and reasonably lubricated. The correct use and reasonable maintenance of the mold is of great importance to improve the life of the mold.
In short, in the whole process of mold design, manufacturing, use and maintenance, the application of advanced manufacturing technology and the implementation of total quality management is an effective guarantee to improve the life of the mold, and is committed to the development of specialized production, strengthen the standardization of the mold, in addition to parts standardization There are also standardization of design parameters, standardization of combination forms, standardization of processing methods, etc., and continuously improve the mold design and manufacturing level, which is conducive to improving the life of the mold.
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