The development process of Japanese hot forging die steels

As originally used hot work tool steels are forged tool steel. In 1944 (Showa 19 years) in the temporary regulations from the Japanese standard is the first to fourth forging die steel. In 1947 (Showa 22 years) provided the first in Japan to metal standard JES sixth (SKF1 ~ 6) for the forging die steel. The average chemical composition shown in Table 1.
Table 1 JES forging die steel (1947) standard chemical composition (mass fraction) /%

Steel grade	C	Si	Mn	Ni	Cr	Mo	V
SKF1	0.70	0.25	＜0.80	-	-	-	-
SKF2	0.52	0.25	0.60	-	1.55	-	-
SKF3	0.52	0.25	1.00	-	1.00	-	-
SKF4	0.52	0.25	0.70	-	1.00	-	0.25
SKF5	0.80	0.25	0.75	2.00	1.00	0.20	-
SKF6	0.55	0.25	0.75	2.00	1.00	0.20	-
Remarks	HC-Japanese hot forging die steels-01。

1956 revision of the JIS standard forging die steel as SKT1 ~ 6 six, but the content changes significantly. JES is only for the remaining standards in the SKF3 SKT2, but no other new regulations, increasing the chemical composition of tiny changes. 1956, JIS standard forging die steel standard components are shown in Table 2.
Table 2 1956, JIS standard forging die steel standard chemical composition (mass fraction) /%

Steel grade	C	Si	Mn	Ni	Cr	Mo	V
SKT1	0.55	＜0.35	1.00	-	-	-	-
SKT2	0.55	＜0.35	1.00	-	1.00	-	-
SKT3	0.55	＜0.35	0.80	0.42	1.05	0.40	-
SKT4	0.55	＜0.35	0.80	1.65	0.85	0.35	-
SKT5	0.55	＜0.35	0.80	-	1.25	0.30	0.20
SKT6	0.75	＜0.35	0.80	2.75	0.95	0.40	-
Remarks	HC-Japanese hot forging die steels-02。

In the forging die steel, according to the size of the mold or die moment changes with the depth of hardness. Large, deep conditions to reduce hardness and improve toughness. And the use of steel has good hardenability with high nickel steel. There are 1972 standard revision SKT1 steel with almost no use of performance reasons was abolished. These steels are typically used is SKT4 steel (Japan Datong steel die steel is quite GF4, Japan, Daido Steel's GF78 is an 3Cr-1Mo-V Series hot die forged steel type), made of high-end hot forging die steel GR is also a good choice of steel, HongChao(DongGuan)Mould & Technology Co., Ltd. particular recommendation.
Hardenability, toughness, superior wear resistance with appropriate and therefore not only forging dies, cutting tools, such as the mechanical shearing knife, upsetting die, hot trimming die, die embossing tools such as impact resistance or hot extrusion of the press cylinder , cylinder liner, the pressure head is also used. Speculate about the origin of SKT4 steel in Germany 55NiCrMoV6 steel.
With forging die steel for die situation, the majority of the quenched and tempered state supply. Therefore, hardness 300 ~ 400HB state cutting, so asked to be cut is good, but also for the durability of the mold. The 1960s compared with the imported mold steel production in Japan is cutting mold steel. Japan was the result of cutting tool steel is poor. The reason is that Japan's low sulfur material (S <0.02%), imports of material sulfur content (0.02% ~ 0.03% S). In addition, the Department also made of aluminum inclusions or microstructure of the problem.
Future environmental problems due to noise or forging gradually weakened, to press forging alternative, mold has shifted to a more heat-resistant hot work tool steel.Such as: Japan Daido Steel DH31-S, DH31-EX, DRM1, DRM2 and Sweden UDDEHOLM tool steel series DIEVAR, QRO 90 SUPREME, HOTVAR and so on.

More information
Please direct HongChao(DongGuan)Mould & Technology Co., Ltd. service contact (hotline 86 0769 -82621066 / 82621088, the National Service Hotline :400-699-1286) for more on Japanese forging die steel developments and high-quality mould steel (Japan Daido steel, Assab tool steel, Germany Groditz mould steel, Japan Fuji high-speed steel, Japan's Hitachi mould steel, etc.) the selection, application, heat treatment and inventory and other related information.
Source: HongChao(DongGuan)Mould & Technology Co., Ltd. Technology Center
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