Stamping die common used materials and material selection principles
Introduction
Materials for manufacturing Stamping Dies are steel, cemented carbide, steel-bonded cemented carbide, zinc-based alloy, low-melting alloy, aluminum bronze, polymer materials, and so on. Most of the materials used to make stamping molds are steel. The types of commonly used mold working parts are: carbon tool steel, low alloy tool steel, high carbon high chromium or medium chromium tool steel, medium carbon alloy steel, and high speed steel. , Base steel and cemented carbide, steel cemented carbide and so on.
Basic classification
a. Carbon tool steel
The carbon tool steels used more in the mold are T8A, T10A, etc. The advantages are good processability and low price. However, the hardenability and red hardness are poor, the heat treatment deformation is large, and the bearing capacity is low.
b. Low alloy tool steel
Low alloy tool steel is based on carbon tool steel with an appropriate amount of alloying elements. Compared with carbon tool steel, it reduces the tendency of quenching deformation and cracking, improves the hardenability of the steel, and has better wear resistance. The low-alloy steels used for manufacturing molds include CrWMn, 9Mn2V, 7CrSiMnMoV (code CH-1), 6CrNiSiMnMoV (code GD), and the like.
c. High carbon high chromium tool steel
Commonly used high-carbon and high-chrome tool steels are Cr12 and Cr12MoV, Cr12Mo1V1 (code D2), and SKD11. They have good hardenability, hardenability, and wear resistance, and have little heat treatment deformation. , The load capacity is second only to high-speed steel. However, the segregation of the carbide is serious, and repeated upsetting (axial upsetting, radial drawing) must be performed to change the forging to reduce the unevenness of the carbide and improve the performance.
d. High carbon medium chromium tool steel
High carbon medium chromium tool steels for molds include Cr4W2MoV, Cr6WV, Cr5MoV, etc., which have low chromium content, low eutectic carbides, uniform carbide distribution, small heat treatment deformation, good hardenability and dimensional stability. Sex. Compared with high-carbon high-chromium steel with relatively severe segregation of carbides, the performance is improved.
e. High-speed steel
High-speed steel has the highest hardness, abrasion resistance and compressive strength among mold steels, and has a high bearing capacity. Commonly used in molds are W18Cr4V (code 8-4-1) and W6Mo5 Cr4V2 (code 6-5-4-2, U.S. brand M2) with low tungsten content, and carbon and vanadium-reducing high-speed steels developed to improve toughness 6W6Mo5 Cr4V (code 6W6 or low carbon M2). High speed steel also needs to be forged to improve its carbide distribution.
f. Base steel
Add a small amount of other elements to the basic composition of high-speed steel, and appropriately increase or decrease the carbon content to improve the performance of the steel. Such steel types are collectively referred to as base steel. They not only have the characteristics of high-speed steel, they have certain wear resistance and hardness, but also have better fatigue strength and toughness than high-speed steel. The base steel commonly used in molds is 6Cr4W3Mo2VNb (code 65Nb), 7Cr7Mo2V2Si (code LD), 5Cr4Mo3SiMnVAL (code 012AL), etc.
g. Carbide and steel cemented carbide
Cemented carbide has higher hardness and wear resistance than any other type of mold steel, but has poor bending strength and toughness. The cemented carbide used as the mold is tungsten-cobalt. For the mold with low impact resistance and high wear resistance, the cemented carbide with low cobalt content can be selected. For high-impact molds, cemented carbide with higher cobalt content can be selected.
Steel-bonded cemented carbide is made of iron powder with a small amount of alloying element powder (such as chromium, molybdenum, tungsten, vanadium, etc.) as a binder, and titanium carbide or tungsten carbide as the hard phase, which is sintered by powder metallurgy. The matrix of steel-bonded cemented carbide is steel, which overcomes the disadvantages of poor toughness and difficult machining of cemented carbide, and can be cut, welded, forged and heat-treated. Steel-bonded cemented carbides contain a large amount of carbides. Although the hardness and wear resistance are lower than cemented carbides, they are still higher than other steel types. After quenching and tempering, the hardness can reach 68 ~ 73HRC.
h. New materials
The materials used for stamping dies are cold-working die steels, which are the die steels with a large amount of application, a wide range of use, and the largest variety. The main performance requirements are strength, toughness and wear resistance. The development trend of cold work die steel is based on the performance of high-alloy steel D2 (equivalent to China's Cr12MoV), which is divided into two major branches: one is to reduce the carbon content and the amount of alloy elements, and improve the uniformity of carbide distribution in steel Prominently improve the toughness of the mold. Such as 8CrMo2V2Si of American vanadium alloy steel company, DC53 (Cr8Mo2SiV) of Japan Datong Special Steel Company. The other is a powder high-speed steel developed with the main purpose of improving wear resistance to adapt to high-speed, automation, and mass production. Such as 320CrVMo13 in Germany, and so on.
Selection principle
In stamping dies, various metal materials and non-metal materials are used, mainly carbon steel, alloy steel, cast iron, cast steel, hard alloy, low melting alloy, zinc-based alloy, aluminum bronze, synthetic resin, polyurethane Rubber, plastic, laminated birch boards, etc.
The materials used to make the molds are required to have properties such as high hardness, high strength, high wear resistance, appropriate toughness, high hardenability, no deformation (or less deformation) during heat treatment, and no cracking during quenching.
Reasonable selection of mold materials and implementation of the correct heat treatment process are the keys to ensuring the life of the mold. For molds with different purposes, comprehensive consideration should be given to factors such as their working conditions, stress conditions, the properties of the material being processed, production batches and productivity, and a focus on the performance of the above requirements. Corresponding choice of process.
When the production volume of stamping parts is very large, the material of the convex part and the concave part of the working parts of the mold should be selected from the mold steel with high quality and good wear resistance. For the other process structure parts and auxiliary structure parts of the mold, the material of the parts should be improved accordingly. When the batch size is not large, the requirements for material properties should be appropriately relaxed to reduce costs.
When the material being stamped is harder or the deformation resistance is greater, the convex and concave dies of the punch should be selected from materials with good wear resistance and high strength. When drawing stainless steel, aluminum bronze die can be used because it has better anti-adhesion. The guide post and guide sleeve require wear resistance and better toughness, so the surface carburizing and quenching of low carbon steel are mostly used. For another example, the main deficiency of carbon tool steel is poor hardenability. When the die section size is large, its central hardness is still low after quenching. However, when working on a press with a large number of strokes, due to its resistance Good impact has become an advantage. For fixed plate and discharge plate parts, not only must have sufficient strength, but also require small deformation during work. In addition, you can also use cold and cryogenic treatment, vacuum treatment and surface strengthening methods to improve the performance of mold parts. For cold extrusion dies with poor working conditions for convex and concave dies, mold steels with sufficient comprehensive mechanical properties such as sufficient hardness, strength, toughness, wear resistance, etc. should be selected, and they should have certain red hardness and thermal fatigue strength. .
Consideration should be given to the hot and cold workability of the material and existing plant conditions.
Note the use of micro-deformed die steel to reduce machining costs.
For molds with special requirements, mold steel with special properties should be developed and applied
The choice of mold materials should be determined according to the conditions of use of the mold parts, so that on the premise that the main conditions are met, low-cost materials are selected to reduce costs.
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