1, the application of low alloy cold die steel
Simple mould can be used for high carbon steel such as T10A, but the high carbon steel hardenability and quenching distortion and low wear resistance, strong toughness and tempering stability are poor, and therefore can not be used to make complex shape, high precision mould, large bearing capacity.
High carbon low alloy steel developed in order to apply the performance of mould is in carbon tool steel based on adding alloy elements such as chromium, nickel, manganese, molybdenum, titanium, tungsten, vanadium, silicon and other elements of smelting and commonly used by CrWMn, 9SiCr, 9Mn2V, GCr15 and other alloy elements with the increase of the hardenability of steel, cold oil replace water reducing tendency of mold deformation and cracking, martensite is not easily decomposed in tempering, decomposition of the carbide precipitation and not easy to grow up, after low temperature tempering has high toughness and wear resistance, mold service life can be greatly improved.
In recent years, China has developed some new low alloy cold die steel, the main characteristics of this steel alloy is low, the amount of good hardenability and the quenching temperature is low, heat treatment distortion and strong wear resistance and good toughness, as appropriate, such as GD (6CrMnNiMoVSi) steel, CH steel, DS (7CrSiMnMoV) (6CrMnNiMoVWSi) and CrNiWMoV steel etc.. Adding a small amount of Ni and Si in GD steel which can strengthen the matrix and improve the low temperature tempering resistance, adding Mo and V can be used in the manufacture of high quality grain refinement, die edge and easy to fracture, high service life. DS steel is a kind of anti impact cold working die steel, tool steel with its toughness is significantly better than the commonly used high toughness blade. The composition of the CH steel and SX105V steel, is a kind of flame hardening die steel, commonly used in the manufacture of automobile production line with the mold parts, flame quenching, heating the die cutting edge cutting surface, the hardened layer has a high tenacity base do liner, in order to get a higher service life.
2, high toughness and high wear resistance of die steel
Many applications in our country is on the traditional Cr12 type series, such as Cr12, Cr12MoV steel, they are ledeburite steel, the organization has a lot of eutectic carbide, quenching has large residual austenite, small, high abrasion resistance, large bearing capacity, long in the domestic large and medium-sized cold is widely used in mold the deformation after heat treatment.
Although Cr12, Cr12MoV steel has good abrasion resistance, but its toughness is poor, and often due to segregation of carbide caused by heat treatment after fracture. In order to overcome these shortcomings, both at home and abroad have done a lot of work, on the one hand, the effort in improving the quality of the steel, such as the use of electric furnace + ladle furnace and electroslag remelting to increase steel purity, density, etc. to uniform and reduce segregation; on the other hand, and constantly study new steel, has developed a variety of high toughness and high wear resistance of die steel, such as LD (7Cr7Mo2V2Si) GM (9Cr6W3Mo2V2) steel, steel, steel ER5 (Cr8WMoV3Si). Compared with Cr12 die steel, the new developed steel appropriate to reduce the content of C and Cr to improve the carbide segregation, also increased the content of W, Mo and V, in order to increase two times hardening ability and improve its wear resistance. The new die steel has high strength and toughness, and good abrasion resistance, with its manufacture of die service life increased.
3, the application of high speed steel and steel matrix
High speed steel has high hardness, compressive strength and wear resistance, so more and more requirements for the manufacture of heavy load life of cold working die steel, commonly used are: W18Cr4V, W6Mo5Cr4V2, W12Mo3Cr4V3N, W9Mo3Cr4V, in order to improve the toughness and carbon reduction developed reduced vanadium high speed steel 6W6Mo5Cr4V, the steel in the manufacture of heavy load cold die gained good effect.
In order to improve the matrix steel high-speed steel carbide uneven distribution and poor toughness developed. Matrix steel generally refers to its composition and microstructure of high speed steel quenched in the same chemical composition of steel. In recent years, China's development of some matrix steel such as 65Nb steel (6Cr4W3Mo2VNb), CG-2 (6Cr4Mo3Ni2WV) 012Al (5CrMo3SiMnVAl) steel, steel, steel, LM1 (6W8Cr4VTi) LM2 (6Cr5Mo3W2VNb) RM2 (5Cr4W5Mo2V) steel, steel, steel and other 5Cr4Mo2W2VS. The main features of the matrix steel is carbon content of the carbon content is slightly higher than that of high-speed steel, with an increase in carbides and improve wear resistance.Some steel also added a small amount of strong carbide forming elements Nb and Ti, to form a relatively stable carbides, prevent quenching grain growth and improve the process performance of steel. Eutectic carbide matrix steel quantity is small and small and uniform distribution, improve the toughness, flexural strength, fatigue resistance is also improved. Matrix steel mainly for high strength and sufficient toughness cold extrusion, cold heading mould, some matrix steel can also be used for hot working die.
4, no magnetic high strength die steel
The development of electronic industry, the demand for non magnetic die steel is greatly increased, the traditional non-magnetic die steel 7Mn15Cr2A13V2WMo is a kind of high strength austenitic nonmagnetic steel, its permeability is low, and has the strength and good wear resistance, but due to the cold hardening, cutting work difficult. The scientists developed some new non-magnetic die, A18 steel (18Mn12Cr18NiN), WCG (8Mn15Cr18) 50Mn (50Mn18Cr4WN) steel, steel, and stainless steel. These steel low magnetic permeability, high strength, and has good cutting performance.
5, the application of steel bonded carbide
Mould for manufacturing hard alloy, without impact toughness requirements is not high, the performance is better than steel, life is very long, but the cost is higher, it is more difficult due to manufacturing constraints, it is difficult to mold manufacturing complex shape.
In 1960s our country has begun to study the steel bonded hard alloy, Kunshan cold die steel It is a new type of material between alloy steel and hard alloy, has excellent abrasion resistance. Compared with the hard alloy and steel bonded carbide cutting, forging, welding, heat treatment, and has good comprehensive mechanical properties, toughness, low cost. The development of China's steel bonded hard alloy with TiC as hard phase GT35, R5, DT, Ti and WC as hard phase GW50, TLMW50, GJW50.