To material selection of cold punching die Introduction
How to choose good cold punching die material
"Mold is the mother of industry", the mold performance is good or bad, life level, directly affects the quality of products and economic benefits.
Mold manufacturing is the most important issue of die material. Manufacturing tooling and parts of the material there are many, such as steel, cast iron and non iron alloy and alloy, high temperature alloy, hard alloy, organic polymer materials, inorganic non metallic materials, natural or artificial diamond. But the steel is used the most, the most widely used materials.
First, the principle of material selection
Material selection is often a complex and difficult judgment, optimization process. There is no doubt, the selected materials should meet the need of use of the product, durable, easy processing, high economic benefit. And material shall be, in general, follow three basic principles: the use of performance, process performance and economic performance, and they are a dialectical unity. In most cases, performance is material the primary principle and basis, and consider the technical performance and economic performance, obtains the optimization results.
1, the use of the principle of selection of performance
Performance is to meet the use needs necessary performance of materials, it is to ensure the realization of the design of the function of the part and the necessary conditions for safe and durable, is the main principle of material. Firstly, we analyze parts of the working conditions, determine its performance; second failure analysis, determine the main performance; then parts performance requirements into requirements on material performance indexes and the actual value.
2, the principle of selection of process performance
The process performance of the material can be defined as the ability of the material economy to adapt to various processing techniques to obtain the required performance and appearance.
Technological properties of metallic materials generally include: casting properties, pressure processing performance, welding performance, mechanical properties, heat treatment process performance; process performance of the main technology of polymer materials for the processing molding and process performance is good, the tool as a forming die.
3, the economic performance of the principle of selection
Mainly refers to the choice of cheap, low cost of processing materials, material cost is the core of economic material selection principles.
Two, mold materials and properties
1, mold materials overview
Mold is the core manufacturing technology, industrial development, we must first develop the mold industry. Mold as the basic industry of the national economy, involving machinery, automobile, light industry, electronic, chemical industry, metallurgy, building materials and other industries, a large quantity of wide, wide variety. The main performance index of the mold material: strength, hardness, plasticity, toughness and fatigue resistance. And mold the main failure form is fracture, excessive deformation, surface damage and thermal fatigue, affect the life of the mold also many factors.
2, the failure mode of cold work die parts
(1) cold work die working conditions are: the working conditions of the working conditions of a cold punching blanking die working conditions B cold bending mode of working conditions C cold deep drawing die d cold upsetting die e cold extrusion die working conditions.
(2) the main failure forms of cold work die include: a fracture failure B deformation failure C wear failure D occlusal failure e bite injury failure.
(3) all kinds of cold working die failure characteristics: a cold punching die, mainly B cold deep drawing die wear, mainly occlusal failure C cold upsetting die, mainly cracking, broken D cold extruding die, punch is broken, fatigue fracture, plastic deformation and wear; concave die is mainly spalling and wear.
3, the performance requirements of cold work die materials. The main performance indexes include: wear resistance, deformation resistance, fracture resistance, occlusal resistance, heat softening resistance.
Three, cold work as a mold material
Cold work die steel is the most widely used cold work die materials. According to the chemical composition, process performance and bearing capacity of the cold can be classified as die steel:
Low quench cold work die steel: T7A, T8A, T10A, T12A, 8MnSi, Cr2,9Cr2, Cr06, GCr15, CrW5.,
Low deformation cold work die steel: 9Mn2V, CrWMn, 9SiCr, 9CrWMn, 9Mn2, MnCrWV, SiMnMo.
High wear resistant micro deformation cold working die steel: Cr12, Cr12Mo1V1 (D2), Cr12MoV, Cr5Mo1V, Cr4W2MoV, Cr12Mn2SiWMoV, Cr6WV, Cr6W3Mo2.5V2.5.,, and so on.
High strength, high wear resistance and cold working die steel: W18Cr4V, W6Mo5Cr4V2, W12Mo3Cr4V3N.
High strength and Toughness Cold Work Die Steel: 6W6Mo5Cr4V, 65Cr4W3Mo2VNb (65Nb), 7Cr7Mo2V2Si (LD), 7CrSiMnMoV (CH-1), 5Cr4Mo3SiMnVAl (012Al), 6CrNiSiMnMoV (), (GD), 8Cr2MnWMoVS. ().
High abrasion resistance and high strength and Toughness Cold Working Die Steel: 9Cr6W3Mo2V2 (GM), Cr8MoWV3Si (ER5).
Cold work die steel for special purpose: 9Cr18, Cr18MoV, Cr14Mo, Cr14Mo4,1Cr18Ni9Ti, 5Cr21Mn9Ni4W, 7Mn15Cr2Al3V2WMo.
Four, several common cold die materials
(1) carbon tool steel
T7a toughness of high carbon tool steel, the strength and toughness are higher, suitable for making brittle small mold or bear larger impact load of the mold; T10A is the most commonly used steel, the performance is a good representative of carbon tool steel, the wear resistance is high, after proper heat treatment high strength and toughness can be obtained, suitable for production of high wear resistance requirements under impact load is smaller die.T8A quenching permeability, toughness were excellent wear resistance is higher, suitable for making small tensile, extrusion die.
(two) low alloy tool steel
Low alloy tool steel, add the right amount of alloy elements on the basis of carbon tool steel. It can reduce the quenching cooling rate, reduce the thermal stress and organizational stress, reduce the quenching deformation and cracking tendency, the hardenability of the steel permeability increased significantly. For mold in the manufacture of low alloy steel CrWMn,.CrWMn 9mn2v, 9SiCr and 9crwmn, 9Mn2,7CrSiMnMoV, type 6crnimnsimov etc. steel has better quenching permeability, small deformation hardening, but its wear resistance, strong toughness, deformation requirements still can not meet the needs of complex shape of cold working die.
(three) high carbon and high chromium cold work die steel
High carbon high chromium cold work die steel including Cr12, Cr12MoV, Cr12Mo1V1 with high hardness, high strength, high wear resistance, easy hardenability, high stability, the advantages of small deformation and high compressive strength and high carbon high chromium steel after quenching. The blank of high hardness and internal stress after forging large, must be annealed. Carbon high chromium steel during tempering, will appear martensite decomposition, transformation of carbides and residual austenite aggregation. In industrial production, often using 2 ~ 3 tempering to improve previous tempering residual austenite into primary martensite ductile steel, so as to improve the toughness of.Cr12 steel strength and high wear resistance, but the carbide is more serious, the use of brittle fracture tendency, low toughness. The comprehensive mechanical performance requirements of mould more commonly used instead of steel, high-speed steel.
(four) high speed steel
High speed steel has high hardness, compressive strength and wear resistance, low temperature quenching, rapid heating process measures, can effectively improve the toughness of high speed steel. Therefore, more and more applied in the requirements of heavy load, high die life of cold. High speed steel alloy element content is high, the price is expensive, poor process performance, brittle, its application was limited. W-Mo high-speed steel, because of the carbide distribution is uniform, fine particles, the toughness of W6Mo5Cr4V2 steel is better than that of W18Cr4V, so it is widely used. High strength and toughness of high speed steel 6W6Mo5Cr4V reduced carbon reduction of vanadium, the appropriate reduction of content of carbon and vanadium, and the plastic bending strength, impact toughness and hardness are significantly improved, and two hardening ability are kept.
(five) matrix steel
Mold used steel substrate have 6Cr4W3Mo2VNb, 7Cr7Mo2V2Si 5Cr4Mo3SiMnVAL. Steel substrate was widely application in the manufacture of cold extrusion, cold plate drawing and cold heading and mold, and is particularly suitable for difficult to deformation materials with large, complex mold manufacturing and the, also can be used as a black metal hot extrusion die, a kind of hot and cold dual-purpose mould steel. With the widespread use of high-speed automatic multi station cold heading machine and broad application of steel with high strength and high toughness stainless steel stampings, cold die service conditions even worse, by electroslag remelting and composite reinforcement 012AL steel cold punching die, can significantly improve the service life.