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Stamping die material selection and heat treatment requirements
Dec 08, 2017

Stamping die material selection and heat treatment requirements

A blanking die material selection and heat treatment requirements

Selection of blanking die material should consider the production of the workpiece batch, if the batch is not large, there is no need to choose a high life mold material; should also be considered the workpiece material, different materials for different mold materials are also different. For the blanking die, wear resistance is an important factor in determining the life of the die, the wear resistance of steel depends on the hard carbide phase carbide situation and the hardness of the matrix, the higher the hardness of both, the greater the number of carbides , The better wear resistance. Commonly used stamping die steel inferior inferior resistance followed by carbon tool steel - alloy tool steel - the base of steel - high-carbon high-chromium steel - HSS - Steel Carbide - Carbide.

In addition you must also consider the workpiece thickness, shape, size, precision requirements and other factors on the choice of mold material.

1. Traditional mold steel

For a long time, the domestic plate blanking die steel T10A, CrWMn, 9Mn2V, Cr12 and Cr12MoV and so on.

One T10A carbon tool steel, a certain strength and toughness. But the wear resistance is not high, easily deformed and cracking quenching, hardenability is poor, only for the workpiece shape is simple, small size, small number of blanking die.

T10A carbon tool steel heat treatment process: 760 ~ 810 ℃ water or oil quenching, tempering 160 ~ 180 ℃, hardness 59 ~ 62HRC.

CrWMn, 9Mn2V is a kind of high-carbon and low-alloy steel, easy to quench, hardenability better than carbon tool steel, easy to control the deformation. But the wear resistance and toughness is still low, used in medium-volume, more complex shape of the workpiece blanking die. CrWMn steel heat treatment process: quenching temperature 820 ~ 840 ℃ oil cooling, tempering temperature 200 ℃, hardness 60 ~ 62HRC. 9Mn2V steel heat treatment process: quenching temperature 780 ~ 820 ℃ oil cooling, tempering temperature 150 ~ 200 ℃, air cooling, hardness 60 ~ 62HRC. Note tempering temperature in the range of 200 ~ 300 ℃ temper brittleness and significant volume expansion, should be avoided.

Cr12 and Cr12MoV high-carbon high-chromium steel, high wear resistance, small deformation during quenching, good hardenability, can be used for mass production of molds, such as silicon steel blanking die. However, the existence of such steel carbide heterogeneity, easy to produce carbide segregation, blanking prone to chipping or fracture. Among them, Cr12 higher carbon content, uneven distribution of carbides Cr12MoV more serious, more brittle.

Cr12 steel heat treatment process selection depends on the use of mold requirements, when the mold requires a smaller deformation and a certain toughness, low temperature quenching, tempering (Cr12 950 ~ 980 ℃ quenching, tempering 150 ~ 200 ℃; Cr12MoV 1020 ~ 1050 ℃ quenching, tempering 180 ~ 200 ℃). To improve the use of mold temperature and improve its hardenability and red hardness, high temperature quenching, tempering (Cr12 is 1000 ~ 1100 ℃ quenching, 480 ~ 500 ℃ tempering; Cr12MoV 1110 ~ 1140 ℃ quenching, 520 ℃ tempering).

High chromium steel temper brittleness in the 275 ~ 375 ℃ area, should be avoided.

  2. Common mold new steel

In order to make up for the lack of performance of traditional mold steel, the domestic development or introduction of the following properties better stamping die steel:

(1) Cr12Mo1V1 (code D2) steel for the United States ASTM standard D2 steel imported steel, Cr12 steel. Due to the increase of Mo and V content in D2 steel, the grains are refined and the distribution of carbides is improved. Therefore, the toughness (impact toughness, flexural strength, deflection) of D2 steel is higher than that of Cr12MoV steel, Sexual and anti-tempering stability is also higher than Cr12MoV. Cryogenic treatment can be used to increase hardness and improve dimensional stability. Die made of D2 steel stamping die life is higher than the Cr12MoV steel mold.

D2 steel forging performance and thermoformability slightly worse than the Cr12MoV steel, machining performance and heat treatment process similar to the Cr12 steel.

(2) Cr6WV steel is a high-wear high-carbon medium-chrome steel with high wear-resistance. The content of carbon and chromium is lower than that of Cr12 steel. The distribution of carbide is more uniform than that of Cr12MoV and has good hardenability. Heat treatment of small deformation, machining performance is better. Flexural strength, impact toughness better than Cr12MoV, but wear resistance slightly lower than Cr12 steel. Used to withstand greater impact of high hardness, high wear-resistant sheet blanking die, the effect is better than Cr12 steel.

Common steel heat treatment process: Quenching temperature 9701 ~ 000 ℃, the general classification of hot oil or nitrate quenching and cooling, small size of the components can be air-cooled. Tempering immediately after quenching, tempering temperature 160210 ~ ℃, hardness 58 ~ 62HRC.

(3) Cr4W2MoV steel is also high wear-resistant micro-deformation of high-carbon medium-chromium steel, Cr12 steel instead of the development of steel species, carbide uniformity, wear resistance higher than Cr12MoV, suitable for the production of complex shapes, high dimensional accuracy Stamping die, can be used for silicon steel blanking die.

Cr4W2MoV steel heat treatment process: the required strength, high toughness, the use of low temperature quenching, low temperature tempering process: quenching temperature 960 ~ 980 ℃, tempering temperature 280 ~ 320 ℃, hardness 60 ~ 62HRC. Requirements of high heat resistance and wear resistance, the use of high temperature quenching, high temperature tempering process: quenching temperature 1020 ~ 1040 ℃, tempering temperature 50 ~ 540 ℃, hardness 60 ~ 62HRC.

(4) 7CrSiMnMoV (code CH-1) steel is empty quenching micro-deformation of low alloy steel, flame hardened steel, the flame can be used for local hardening, hardened mold edge part. Quenching temperature (800 ~ 1000 ℃), with good hardenability and hardenability (up to 60 HRC above), higher strength and toughness, after the collapse of the edge welding. Can replace the CrWMn, Cr12MoV steel, the production of complex shapes blanking die. The recommended heat treatment process for CH-1 steel: quenching temperature 900 ~ 920 ℃, oil cooling, tempering 190 ~ 200 ℃ for 1 ~ 3 hours, hardness 58 ~ 62 HRC.

(5) 6CrNiSiMnMoV (code GD) steel high toughness low alloy steel, good hardenability, air quenching deformation of small, high wear resistance. Its toughness is significantly higher than CrWMn and Cr12MoV steel, not easy to chipping or fracture. Especially for slender, flake punch and large, complex shape, thin-walled punch.

GD steel recommended heat treatment process: quenching temperature 870 ~ 930 ℃ (900 ℃ best), salt bath furnace heating (45s / mm), oil or air cooling, air cooling, tempering 175 ~ 230 ℃ 2 hours, hardness 58 ~ 62 HRC. As the air-cooled hardened, flame quenching can also be used.

(6) 9Cr6W3Mo2V2 (Code GM) steel is high wear-resistant and high-toughness alloy steel, the process performance is good, the wear resistance, toughness, processing performance are better than Cr12 steel, can be used for high-speed press Station-level progressive die precision molds, is the ideal wear-resistant, precision stamping die steel.

GM steel heat treatment process: quenching temperature 1080 ~ 1120 ℃, hardness 64 ~ 66HRC. Tempering temperature 540 ~ 560 ℃, tempering twice.

(7) Cr8MoWV3Si (code ER5) steel is a high wear-resistant and high-toughness alloy steel with good EDM performance. Its strength, toughness and wear resistance are superior to those of Cr12 steel. It is suitable for large-scale precision stamping dies. For silicon steel blanking die, a grinding life of 21 million times, the total life expectancy of up to 3.6 million times, is the current high-life alloy steel die punching silicon steel.

ER5 steel recommended heat treatment process: For high wear resistance, high strength and toughness of the mold, using 1150 ℃ quenching, tempering 520 ~ 530 ℃ 3 times; under heavy service conditions of the mold, using 1120 ~ 1130 ℃ quenching, 550 ℃ Tempering 3 times.

  3. Carbide and steel cemented carbide

When the workpiece is very large batch, you can consider the choice of hardness and wear resistance than all kinds of mold steel higher carbide or steel bonded carbide. Carbide used as a mold material is tungsten and cobalt, with the increase of cobalt content, the toughness and flexural strength increase while the hardness decreases. For the impact of smaller molds, you can choose the lower YG10X cobalt content; to withstand the impact of medium or large mold, you can choose a higher amount of YG15 or YG20 cobalt. Carbide has the disadvantage of poor toughness, difficult to process, as a working part of the mold can be designed as mosaic structure. Steel hardened cemented carbide is between cemented carbide and high-speed steel, machined and heat-treated, and can be used to make complex high-life dies. Used as blanking die steel with DT, GT35, TLMW50, GW50 and so on.

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