Selection Of Steel For Cold Work Die Steel

- Jul 19, 2017 -

Usually, the selection of steel grades can be divided into the following four cases according to the cold working conditions of the mould:

(1) cold working die with small size, simple shape and light load. For example, small punch, cut steel plate, scissors and so on, can choose T7A, T8A, T10A, T12A and other carbon tool steel manufacturing. The advantage of this kind of steel is good processability, cheap price and easy source. But its shortcomings are: low hardenability, poor wear resistance, large quenching deformation. Therefore, the utility model is only suitable for making small size, simple shape and light load tools, and the cold image mold which requires the hardening layer not to be deep and to maintain high toughness.

(2) cold working die with large size, complex shape and light load. The steel used has 9SiCr, CrWMn, GCr15 and 9Mn2V low alloy steel. The hardenability of these steels in oil can generally be above 40mm. Among them, 9Mn2V steel is a kind of cold working die steel without Cr in our country in recent years. It can replace or partially replace steel containing Cr.

9Mn2V carbide of steel and hardened steel CrWMn cracking tendency than small, decarburization tendency than 9SiCr steel, and hardenability than carbon tool steel. Its price is only about 30% higher than the latter so it is worth to promote the use of steel.

But there are some shortcomings such as 9Mn2V steel, the impact toughness is not high, found in the production and use of fragmentation phenomenon. In addition the tempering stability is poor, the tempering temperature is not more than 180 DEG C flexural strength at 200 DEG C when the tempering and toughness of low value began to appear.

Quenching quenching medium 9Mn2V steel in nitrate, moderate cooling capacity in hot oil. For some moulds which require strict deformation and low hardness requirements, austenitic austempering can be used.

(3) cold working die with large size, complex shape and heavy load. To be used in the alloy or high alloy steel. Such as Cr12Mo, Crl2MoV, Cr6WV, Cr4W2MoV etc., there is also a selection of high speed steel.

In recent years, the tendency of using high speed steel as cold working die has been increasing, but it should be pointed out that it is no longer the advantage of high speed steel, but it has high hardenability and high wear resistance. For this reason, the heat treatment process should also be distinguished.

When using high speed steel as cold mould, low temperature quenching should be adopted to improve toughness. For example, W18Cr4V steel cutting tool used when the quenching temperature is 1280-1290 DEG C. When cold working dies are used, 1190 degrees low temperature quenching should be adopted. Another example is W6Mo5Cr4V2 steel, which can greatly improve the service life after low temperature quenching, especially the reduction rate.

(4) cold working die with impact load and thin blade. As mentioned before. Three kinds of performance requirements of steel with high wear resistance are the main to adopt high carbon eutectoid steel's steel cold die. To some cold die jiaqie side buildings, blanking die. The use of thin counterparts. When the impact load should be based on the impact toughness of high. In order to solve this problem. You can take the following measures. To reduce the carbon content. The sub eutectoid steel. In order to avoid the one and two times of carbide and induced the decrease of the toughness of steel; the accession to the Si., Cr and other alloy elements. In order to improve the stability of tempering and tempering temperature (240 270 C steel tempering) this is conducive to fully eliminate the quenching stress to improve sharawadgi. But will not reduce the hardness; II joined W refractory carbide forming elements to refine grains and improve the toughness. Commonly used high toughness cold working die steel, such as 6SiCr, 4CrW2Si, 5CrW2Si and so on.

3., give full play to the potential of cold working die steel performance

When using Cr12 steel or high speed steel as cold working dies, one of the outstanding problems is that the steel is brittle and easy to crack in use. For this reason, it is necessary to refine carbides with full forging. In addition, new steels should be developed. The focus of developing new steels should be to reduce the carbon content of steel and the number of elements formed by carbides. In recent years, several new steels have been developed and popularized in China, as shown in table 4.11.

Cr4W2MoV has the advantages of high hard steel giant, high wear resistance and good hardenability. Tempering and has good stability and mechanical properties. For manufacture of silicon die. Can live longer than Cr12MoV steel increased 1 ~ 3 times but this narrow range of temperature of steel forging, forging river county cracking. Forging temperature should be strictly controlled and operating regulations recognize Cr2Mn2SiWMoV steel quenching deformation hardening, low temperature and high hardenability. Free quenched micro deformation of die steel 7W7Cr4MoV steel and Cr12MoV steel. W18Cr4V is characterized by carbide of steel and toughness are greatly improved.

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