Cold and heat treatment deformation of steel materials

Abstract: with the development of industry, mechanical processing, production on cold mould parts manufacturing, use more more and more kinds of cold deformation mould. Cold forging (volume of cold upsetting, cold extrusion, pressing seals, etc.), Sheet metal stamping (such as drawing, blanking, trimming, punching, etc.), Rolling rolling rolling material (wheel molding, etc.). Although many types of mould cold deformation, working conditions, performance requirements are different, but the basic work in close: namely cold condition that causes the metal deformation, working under great pressure, the shear strength, bending strength, impact and friction.

Along with the development of industry, mechanical processing, production on cold mould parts manufacturing, use more more and more kinds of cold deformation mould. Cold forging (volume of cold upsetting, cold extrusion, pressing seals, etc.), Sheet metal stamping (such as drawing, blanking, trimming, punching, etc.), Rolling rolling rolling material (wheel molding, etc.). Although many types of mould cold deformation, working conditions, performance requirements are different, but the basic work in close: namely cold condition that causes the metal deformation, working under great pressure, the shear strength, bending strength, impact and friction. For this kind of steel should have the following basic properties:

1) high hardness and high strength, to ensure the high stress in susceptible to trace plastic deformation or destroyed. 2) high wear-resisting performance, high abrasion conditions can ensure the precision mould, tensile modulus and to cold stamping mould appear more important. 3) the toughness, in order to enough impact load and dynamic load, do not work of flake or collapse toughness. 4) heat treatment deformation, because most of the mold cavity with complex and precise accuracy, heat treatment deformation is hard to eliminate grinding machining, besides some cold die also should have enough deformation resistance performance. How to reasonably select material and the mold cooling deformation of appropriate treatment method, in order to improve the service life of die is most concerned problems in production as cold deformation of the mold, the normal failure should wear, trace of plastic deformation and fatigue failure. But in actual production, in addition to the failure, and broken, cracking toughening collapse in advance, common failure. As is known to all, affect the service life of cold deformation mold is a comprehensive factors, The selection of raw materials, the rationality of the internal metallurgical quality raw materials, design and manufacture technology of rationality, use condition and operation of technical level etc. Workers But one of the mould material selection and the corresponding treatment process should be important factors, this paper will from raw material and heat treatment process, to explain briefly the function call up.

1, the cold steel selection problem. Deformation

The selection of cold deformation mould should consider the following factors:

1) mold working conditions, including equipment types, processing of the frequency, qualitative, lubrication and environment; etc.

2) mold the complexity of the form and processing procedure,

3) production batch and technical requirements,

4) die material sources of difficulty and processing conditions, large mould material costs often accounts for 50% of the mould cost, to form complex, high precision mould, appropriate chooses quench distortion of steel.

According to the practical use, common cold deformation of steel, low alloy has its quench-hardening ability of low deformation and deformation of steel, steel, high strength steel, high toughness and impact resistant steel alloy cold deformation (such as shown in table 1).

Table 1

2 and all kinds of cold deformation characteristics of steel and the corresponding process

Low alloy cold deformation 2.1 its quench-hardening ability in this kind of steel, carbon tool with high carbon steel GCr15 collaterals and 9Cr2Mo etc GCr15 bearing steel, which 9Cr2Mo and various molding production and make cold rolled steel roll, GCr15 represented with good resistance to wear, but its quench-hardening ability is poor, quenching deformation, as small cold roll (φ acuities blast-caused/m) can use whole heating or whole high-temperature 900-950 degrees c fast heating and cooling with brine, quenching oil, control the workpiece cooling time in brine by 200-220 degrees tempering, roller surface hardness control in Rc60-62, can obtain higher longevity, such as hardness Rc acuity 62 from above the surface in surface spalling, while rolling with GCr15 made of various molding rolling wheel usable alkali bath with two isothermal quenching or nitrate nitrate solution, and three in the control of quenching cooling time, remove the air cold or oil cold rolling wheels can obtain surface deformation of tall hardness.

Along with the development of manufacturing industry, the development of industrial restructuring of material, the corresponding various high-speed roll with more than HeDeGuo 9Cr2Mo steel rolling steel 86CrMoV7 necessary in the industry

To have a new breakthrough in the tough on processing, adopt new roll in steel also has the new breakthrough. Currently in high-speed work roller drive roller adopts D2 is what Cr12MOv (Cr12Movco; 5H12) and (5Cr5MovSi), etc. The author thinks according to the contact fatigue stress extrusion and friction and wear to choose the material, and work roll with crack accident ability to bring the material chosen transmission roller.

2.2 low deformation deformation steel 1) Mn - Cr - W department, this is all the general representative of excellent performance, represented by CrMn cr-mn stainless steel. This steel heat treatment deformation is small, wear-resisting performance characteristics of high and high toughness and its quench-hardening ability. CrWMn steel making use of the mould, such as the use of reasonable heat treatment process, control and adjustment, quenching caused when the thermal stress and deformation and stress, reduce organization can completely replace the factory Cr12 commonly made of mould. 2), is China 9Mn2V Mn CrWMn 9CrSi, such as the substitution of steel, can be used in the manufacture of cold stamping, mould, scissors, bending mode. SiMnMo 3) of graphite, the characteristic is including steel, high quantity in strong Si Si of graphitization elements, under the action of carbon is graphitization state, steel, the higher the embellish anti-bite, good cutting and wear resistance, heat treatment deformation of small size stability. SiMnMo steel, used to make the surface quality of the strict bend, stretching and plastic die can significantly improve the quality of the piece.

230 high wear-resisting micro deformation cold steel with Cr12Mov type deformation represented at home and abroad, it is the most widely used high alloy cold deformation. Cr12Mov improvement is Cr12 steel, carbon content high, cause serious big block carbide uneven faults. Cr12Mov steel is characteristic of high wear resistance and its quench-hardening ability, is the deformation cold punch die, the main material of cold upsetting mold factory is now widely used in general Cr12 steel, high hardness, materials, high wear resistance, especially after heat treatment deformation of its quench-hardening ability, tiny when filing, good performance for cutting, tensile modulus etc widely used in mould. But Cr12 seriously uneven carbide materials have formed a huge block carbide, become mould in use, craze, causing collapse premature failure to break. According to the author's practical experience, as some blanking die use bainite and add the hybrid organization paralympic carbide, life will have improved significantly. As shown in table 2 Cr12 materials for blanking modulus by lower bainite isothermal quenching process of dealing with ordinary times comparison.

Table 2

High strength steel 2.4 deformation are usually cold W18Cr4 HSS W6Mo5Cr4v2 and composed. Used for cold extrusion dies and heavy load of cold upsetting punching, medium thickness steel (10-25m/m) hole punch diameter less than 5 - and the small punch 6m/m. Such as chain and the small punch pieces with punching, adopts the high temperature heat quenching heat treatment process. W18Cr4V (1,250 degrees c - 2,532 heating quenching), with W6Mo5Cr4V2 (11.7 degrees c) by 11.9 - quenching process of mould temperature heating of plastic deformation have high strength, high hardness and resistance, The blade is enough, proved the punch and the temperature quenching can significantly improve life, greatly reduce the punch broke accident.

High-strength steel ductile deformation 2.5 some cold cold and cold heading to withstand high modulus of strength and high impact toughness, and ordinary HSS and high carbon chromium just to brittle fracture or broken parts, mould requiring high toughness, concrete are divided into two types:

1) carbon HSS: W or reduce the Mo for 0.5 - high carbon steel, after processing 0.6 toughness. If 6W6Mo5Cr4V2, specific heat treatment process to quench heating temperature and cooling 1180-160 degrees after 550-57 degrees Celsius, hardness is three times tempering Rc60-63, used for cold extrusion punches or cold upsetting punch can increase exponentially life-span.

2) substrate steel substrate steel is improving, high toughness of another way, and compared the steel, high excess carbide substrate, the tiny little carbide grain distribution, impact toughness, and so were the fatigue strength in HSS, and maintain good abrasion resistance. China has successfully developed and popularized matrix steel. If 65Nb, CG - 2, 012Al (table 3).

Table 3,

Three kinds of steel substrate for more complex shape, toughness and impact load of high cold deformation mould. There are other special steel, such as cutting LengMo steel 8Cr2S (8Cr2MnMovS), except in plastic mould.

3) GaoJiangRen wear-resisting of new steel 7CrMo2V2Si, referred to as LD.

LD is based on the United States patent and adjust the steel alloy elements

And a strong abrasion resistant steel. This excess of carbon steel, and small quantity, and the size of the body's high degree of alloying, LD via 1,100 degrees after the heat, quenching of alloy and Cr12Mov 10.5 degrees by the heat of the body, quenching and close alloying, solid solution strengthening and strengthening effect significantly,. For mould should bear impact load and the requirement of high tenacity of the mould, can greatly improve longevity. The bicycle chains in the internal and external slice blanking mode, use longer than Cr12 LD mold can raise 1-3 times of economic effect made gratifying. As shown in table 4 for LD, P18 (HSS) Cr12Mov mechanical performance comparison.

Table 4.

LD materials not only for blanking rushed in mold or punch resistance and resistance to collapse in toughening craze, antiflex all satisfied with sex, is worth popularizing.

2.6 impact resistant alloy cold deformation

Mainly CrW2Si department and 60Si2Mn steel, impact resistance and toughness for mould with scissors, knives (give priority to) this kind of steel is characteristic of the surplus, organization structure carbon. Because contain multielement alloy, solid solution strengthening and after tempering dispersion is good, strengthen carbide, high strength and high toughness, high impact fatigue resistance. For pneumatic tools, tools and shear modulus and rushed upsetting. Defect is compressive capacity, low thermal stability, quenching deformation control. Hard For CrWzSi fasten steel, scissors, such as 5CrW2Si) should try to use high-temperature heating quenching, to make changes, martensite form that is big, strong toughness in the practical work, this author has very good effect.

Mainly used for making 60Si2Mn inside hexagonal bolt forming of cold upsetting punch and the small hole punch. If the spokes hole punch facile bike. As shown in table 5 for common mould steel impact.

5

3 and closing

Cold deformation of steel production in people life is one of the most concern, and many advanced successful experience. This paper cold mould selection and heat treatment deformation, according to some material and personal practice, and puts forward some opinions on the author only rent