Chinese workers' machinery - measures to improve the durability of stamping dies

Stamping die is an important process equipment in stamping production, and it is an effective means to improve product quality, save raw materials and reflect the technical and economic efficiency of molded products. For the durability of the punch and die after working for a period of time, due to the frequent wear and lost work size, can no longer meet the parts of the technical conditions, according to the total number of parts according to die die punching decision. A pair of die from design, machining, assembly, adjustment to the installation, operation, long cycle, high processing cost, therefore, to die in addition to the requirements of high production efficiency, out of the parts completely meets the quality requirements and technical conditions, the durability of the die itself is also very important.
Die and die durability is the failure phenomenon closely linked, is the failure of die die in the process of using the properties of the material structure, size and shape of stamping die parts changed and lost the original design performance. The die may be deemed to have lapsed when the structure is seriously defective and cannot continue to use or may be able to work but has not been able to complete the specified function. The later the failure occurs, the higher the durability of the die.
The durability of die is very important in production. The higher the durability of the die, the longer the die life, the lower the cost of the parts.
I. failure forms of dies
Die failures are quite frequent in actual production, and the consumption of dies is large. Therefore, the failure reason of the die is analyzed, and various effective measures are adopted to prevent the early failure of the die and improve the durability of the die.
1, wear failure
The working parts of the die should have higher wear resistance. Wear and tear is the die in the use of the process, parts or between the die and workpiece relative movement, by friction, vibration or high temperature fatigue cracking, peeling and wear, and even damage. The early part of the rough surface is quickly rubbed off, so wear quickly; normal wear stage, the wear of the parts tend to be gentle, then die in the best state of technology, the production efficiency showed the best level, the quality of the products the guarantee; after normal wear parts wear period exceeds a certain limit, normal wear the destruction of the deterioration of the situation, contact, wear faster, die work performance decreased rapidly, if not timely repair or replacement of wear parts, die will have accidents, loss of function, so that the scrap.
2, deformation failure
Deformation failure includes excessive elastic deformation or plastic deformation, high temperature creep and so on. During the use of the die, the rigidity and toughness of the die is not enough because of the influence of various loads and alternating temperatures, and the change of the property of the material itself, resulting in the failure of the die.
3 brittle fracture failure
Die of the bad working conditions, subjected to various loads, because of cracks and peeling caused by sudden breaks, but failure due to fatigue failure and stress corrosion cracking and so on, so the die often require higher toughness. Some die in the repeated heating and cooling in the working process, the surface tension and compression by the action of alternating stress, caused by surface crack and spalling, increase friction resistance, the plastic deformation of the workpiece that hinder, die failure. This brittle fracture due to thermal fatigue is one of the main forms of die failure.
Two, affecting the durability of the die
1, the irrational impact of structural design
The die structure is the key for durability, unreasonable structure caused by poor rigidity and uneven thickness distribution, and surface defects (such as surface oxidation, decarburization, cracks, scarring) will affect the performance of materials, resulting in early failure of die.
2, the choice of die material
The choice of suitable die material prevents early failure of the die. Inclusions cause cracks in the die and cause brittle fracture. In further heat treatment and use, the crack further expands and causes the die to crack. When the steel is hot processed and annealed, the decarburization layer is still left sometimes after machining. Because of the different structure of the inner and outer layers, the cooling rate of the heat treatment is not the same, resulting in cracks and cracking of the die. Carbon and alloy elements containing high, eutectic compounds have more, often leads to the quenching crack along the zonal distribution of carbides, die in the process of using the further propagation of cracks, resulting in die cracking.
3, the impact of die machining
Part of the cavity die fillet part or punch, in machining often feed too deep and leave marks, resulting in stress concentration, quenching crack of corresponding parts for further expansion, resulting in die cracking. When machining, the die is heated to a high temperature, which makes the microstructure change. That is to say, the abnormal layer of electric machining is subjected to alternating stress. The micro crack becomes a big crack, which causes the die to crack and die. Grinding will lead to overheating of the surface, or cause surface softening, hardness reduction, so that the use of dies in the use of serious wear or thermal stress due to grinding cracks, and eventually lead to early failure of the die.
4. Influence of heat treatment criterion of die
After machining, the die should be treated by quenching, tempering and other heat treatment. Heating temperature, time, cooling speed, protective atmosphere and other improper selection of process parameters will affect the durability of the die. Die steel contains more carbon and more alloy elements, heat conductivity is poor, heating speed can not be too fast.
When the oxidation occurs, the surface of the die is easy to be scratched and the size becomes smaller, and the early fatigue crack is easy to be generated. When the decarburization occurs, the surface hardness of the die is reduced