How to prevent mold burst?


1. Stamping equipment The accuracy and rigidity of stam […]

1. Stamping equipment
The accuracy and rigidity of stamping equipment (such as presses) are extremely important to the life of the die. The stamping equipment has high precision and good rigidity, and the life of the die is greatly improved. In particular, small-gap or no-gap dies, carbide dies and precision dies must be selected with high precision and rigidity presses, otherwise, the life of the die will be reduced, and the chess set will be damaged in severe cases.
2. Mold design
(1) The precision of the guide mechanism of the mold. 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 process nature and the accuracy of the parts.
(2) The geometric parameters of the cutting edge of the die (convex and concave die). The shape, fit clearance and fillet radius of the convex and concave dies not only have a great influence on the forming of stamping parts, but also have a great influence on the wear and life of the die. 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 stamping parts.
① Use raw materials with good stamping technology as much as possible to reduce stamping deformation force;
②Before stamping, the grade, thickness and surface quality of the raw materials should be strictly checked, and the raw materials should be wiped clean, and surface oxides and rust should be removed if necessary;
③According to the stamping process and the type of raw materials, softening treatment and surface treatment can be arranged if necessary, and appropriate lubricants and lubricating processes can be selected.
(2) Layout and edge.
Unreasonable reciprocating feeding and nesting methods and too small overlap value often cause sharp wear of the mold or gnawing of convex and concave molds. The layout method and edge value must be reasonably selected according to the processing batch, quality requirements and mold matching clearance of the parts to improve the life of the mold.
4. Mold material
①The performance of the material should have high hardness (58~64HRC) and high strength, high wear resistance and sufficient toughness, small heat treatment deformation, and certain hot hardness;
②Good process performance.
5. Thermal processing technology
The quality of thermal processing has a great influence on the performance and service life of the mold.
(1) Forging process. This is an important link in the manufacturing process of mold working parts. The forging temperature range should be strictly controlled, the correct heating specification should be formulated, the correct forging force method should be adopted, and the forging should be cooled slowly or annealed in time.
(2) Preparatory heat treatment. Preliminary heat treatment processes such as annealing, normalizing or quenching, and tempering should be used depending on the material and requirements of the working parts of the mold to improve the structure, eliminate the structural defects of the forging blank, and improve the processing technology.
(3) Quenching and tempering. This is the key link in the heat treatment of the mold. When the die is quenched and heated, special attention should be paid to preventing oxidation and decarburization, and the heat treatment process specification should be strictly controlled. When conditions permit, vacuum heat treatment can be used. After quenching, it should be tempered in time, and different tempering processes should be adopted according to technical requirements.
(4) Stress relief annealing. For molds with high precision requirements, stress relief tempering is required after grinding or electrical machining, which is conducive to stabilizing mold accuracy and improving service life.
6. Surface quality
①During the processing of working parts of the mold, it is necessary to prevent the phenomenon of grinding and burning the surface of the parts, and the grinding process conditions and process methods (such as grinding wheel hardness, particle size, coolant, feed and other parameters) should be strictly controlled;
②During the machining process, tool marks should be avoided on the surface of the working parts of the mold. Macroscopic defects such as interlayers, cracks, and impact scars. The existence of these defects will cause stress concentration and become the root cause of fracture, resulting in early failure of the mold;
③Using fine machining and fine machining such as grinding, grinding and polishing to obtain a smaller surface roughness value and improve the service life of the mold.
7. Surface strengthening treatment
In order to improve the performance and service life of the mold, the surface strengthening treatment of the working parts of the mold is more and more widely used. Commonly used surface strengthening treatments are: liquid carbonitriding, ion nitriding, boronizing, vanadium infiltrating and electric spark strengthening, as well as chemical vapor deposition (CVD), physical vapor deposition (PVD) and in salt baths. Dip carbide method (TD), etc. on the surface of the workpiece.
8. Control of wire cutting metamorphic layer
The cutting edge of the die is mostly processed by wire cutting. Due to the thermal effect and electrolysis of the wire cutting process, a metamorphic layer of a certain thickness is formed on the surface of the mold, resulting in a decrease in surface hardness and microcracks, etc., which makes the wire cutting die prone to early wear, which directly affects the die blanking gap. The holding and the cutting edge are easy to chip and shorten the service life of the mold. Therefore, a reasonable electrical gauge should be selected in the wire cutting process to minimize the depth of the metamorphic layer.
9. Correct use and reasonable maintenance
In order to protect normal production, improve the quality of stamping parts, reduce costs, and extend the life of the die, it is necessary to use and maintain the die properly, strictly implement the die "three inspections" system (inspect before use, inspection during use and inspection after use), and do Good die and maintenance work.