punching mold material classification
A. Carbon tool steel
Carbon tool steel T8A and T10A are widely used in moulds, which have the advantages of good machining performance and low price.But the hardenability and red hardness difference, heat treatment deformation, bearing capacity is low.
B. Low alloy tool steel
Low alloy tool steels are based on carbon tool steels with an appropriate amount of alloying elements.Compared with carbon tool steel, the quenching deformation and cracking tendency are reduced, the hardenability and wear resistance of the steel are improved.Low-alloy steels used for mold manufacturing include CrWMn, 9Mn2V, 7CrSiMnMoV(code ch-1), 6CrNiSiMnMoV(code GD), etc.
C. High carbon and high chromium tool steel
Commonly used high carbon and high chromium tool steels are Cr12 and Cr12MoV, Cr12Mo1V1 (code D2), SKD11, which have good hardenability, hardenability and abrasion resistance. The heat treatment deformation is very small. They are high wear resistance and micro-deformation mold steels, and their bearing capacity is second only to high-speed steel.However, due to severe segregation of carbides, it is necessary to carry out repeated upsetting (axial upsetting, radial drawing) to improve the service performance and reduce the inhomogeneity of carbides.
D. High carbon medium chromium tool steel
The high carbon and medium chromium tool steels used for mold are Cr4W2MoV, Cr6WV, Cr5MoV, etc., which have low chromium content, few eutectic carbides, uniform distribution of carbides, small heat treatment deformation, good hardenability and dimensional stability.Compared with the high carbon and high chromium steels with severe carbide segregation, the properties of the steels are improved.
E. high speed steel
High speed steel has the highest hardness, abrasion resistance and compressive strength of mold steel.Commonly used in molds are W18Cr4V (code 8-4-1), W6Mo5 Cr4V2 (code 6-5-4-2, American brand M2) with less tungsten content, and carbon and vanadium reduction high-speed steel 6W6Mo5 Cr4V (code 6W6 or low carbon M2) developed for improving toughness.HSS also needs to be modified to improve its carbide distribution.
F. the matrix steel
In order to improve the properties of high speed steel, a small amount of other elements are added to the basic composition, and the carbon content is increased or decreased appropriately.Such steels are collectively referred to as matrix steels.They not only have the characteristics of high speed steel, with a certain wear resistance and hardness, and fatigue strength and toughness are better than high speed steel, cold die steel for high strength toughness, material cost is lower than high speed steel.The common matrix steels in the mold are 6Cr4W3Mo2VNb (code name 65Nb), 7Cr7Mo2V2Si (code name LD), 5Cr4Mo3SiMnVAL (code name 012AL), etc.
G. Cemented carbides and steel-bonded cemented carbides
The hardness and wear resistance of cemented carbide are higher than that of any other type of die steel, but the bending strength and toughness are poor.The cemented carbide used as the mold is tungsten cobalt, which requires less impact and higher wear resistance.For high impact moulds, cemented carbide with high cobalt content can be used.
Steel-bonded cemented carbide is sintered by powder metallurgy with titanium carbide or tungsten carbide as hard phase with iron powder added with a small amount of alloying element powder (such as chromium, molybdenum, tungsten, vanadium, etc.) as binder.The matrix of steel-bonded cemented carbide is steel, which can be machined, welded, forged and heat-treated.Steel-bonded cemented carbides contain a large amount of carbides. Although their hardness and wear resistance are lower than that of cemented carbides, they are still higher than other steel grades. After quenching and tempering, their hardness can reach up to 68 ~ 73HRC.
H. new materials
The material used in stamping die belongs to cold working die steel, which is the most widely used type of die steel with large application amount.The main performance requirements are strength, toughness and wear resistance.The development trend of cold working die steel is that based on the performance of high alloy steel D2 (equivalent to Cr12MoV in China), it is divided into two branches: one is to reduce the carbon content and the amount of alloy elements, improve the uniformity of carbide distribution in steel, and highlight the toughness of the mold.Such as the United States vanadium alloy steel company’s 8CrMo2V2Si, Japan datong special steel company’s DC53(Cr8Mo2SiV) and so on.Another kind of powder high speed steel is developed to improve wear resistance for high speed, automatic and mass production.Such as Germany’s 320CrVMo13, etc.
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