9CrWMn is a widely used low-alloy cold work tool steel, designated under China’s national standard (GB/T 1299). Developed from CrWMn steel, its composition has been adjusted to enhance toughness and reduce heat treatment distortion. Its equivalent grades include American AISI/ASTM O1, German DIN 1.2510, and Japanese JIS SKS3.

1. Chemical Composition(GB / T 1299—2000)

C	Si	Mn	Cr	W	P	S
0.85 ~ 0.95	≤0.40	0.90 ~ 1.20	0.50 ~ 0.80	0.50 ~ 0.80	≤0.030	≤0.030

2. Critical Point Temperature of 9CrWMn Steel

Critical Point	Ac₁	Acₑₘ	Ar₁	Ms
Temperature/℃	750	900	700	205

3. Hot Forging Process Specification for 9CrWMn Steel

Item	Heating Temperature/℃	Initial Forging Temperature/℃	Final Forging Temperature/℃	Cooling Method
Steel Ingot	1150 ~ 1200	1100 ~ 1150	≥850	Slow Cooling
Steel Billet	1100 ~ 1150	1050 ~ 1100	≥850	Slow Cooling

4. Heat Treatment for 9CrWMn Steel

4.1 Isothermal Annealing Process of 9CrWMn Steel After Forging

Process	Heating Temperature/℃	Holding Time/h	Isothermal Temperature/℃	Isothermal Holding Time/h	Cooling Method	Hardness HBW
Isothermal Annealing after forging	780 ~ 800	2 ~ 3	670 ~ 720	2 ~ 3	Furnace cool to below 550℃, then air cool	197 ~ 241

4.2 Quenching

① Recommended Quenching Specification for 9CrWMn Steel

Preheat Temperature/℃	Heating Temperature/℃	Cooling Medium	Medium Temperature/℃	Cool to	Hardness HRC
650	820 ~ 840	Oil	20 ~ 60	Oil temperature	64 ~ 66

② Isothermal Quenching Process for 9CrWMn Steel

Heating Temperature/℃	Isothermal Temperature/℃	Isothermal Time/h	Quenching Microstructure
800 ~ 840	260 ~ 300	≤1	The matrix is martensite + retained austenite + residual carbides, with a suitable amount of lower bainite distributed on the high-strength martensite matrix.

4.3 Super-fining Treatment Process for 9CrWMn Steel

The purpose of ultra-fine processing is to obtain ultra-fine carbides and refined grains, hence it is also known as the dual-refining process. This process has been widely adopted in the mold manufacturing industry, significantly extending mold service life.

Process Stage	Solution Quenching	Final Treatment
Process Parameters	The temperature is 1050°C, oil cooling or isothermal treatment at about 300°C, and the tempering temperature is 700~720 °C.	Quenching temperature is 800 ~ 820°C (should be 20 ~ 40°C lower than the conventional quenching temperature).

4.4 Tempering

① Recommended Tempering Specification for 9CrWMn Steel

Heating Temperature/℃	Heating Medium	Cooling Medium	Hardness HRC
160 ~ 180	Oil	Air	61
170 ~ 230	Oil	Air	60 ~ 62
230 ~ 275	Oil or alkaline water	Air	56 ~ 60

② Relationship between Tempering Temperature and Hardness of 9CrWMn Steel

Tempering Temperature/℃	100	200	300	400	500	550	600	650
Hardness HRC	62	60	56	52	47	43	39	35

Note: Quenched in oil at 830°C, then tempered for 2 hours.

5. Mechanical Properties

9CrWMn steel is a low-alloy cold-work tool steel with high hardenability. The carbides formed by the W element constitute the hardening phase in the steel, resulting in high hardness and wear resistance after quenching and low-temperature tempering, while maintaining good toughness. This steel exhibits maximum bending strength and toughness when quenched at 800°C. Impact toughness reaches its lowest value when tempered around 300°C; therefore, tempering at this temperature should be avoided. The steel is sensitive to the formation of network carbide. Thus, appropriate forging should be performed during machining, and carbide refinement treatment is recommended.

6. Applications

9CrWMn steel exhibits minimal distortion during quenching, particularly after undergoing carbide refinement treatment, and possesses high comprehensive mechanical properties. It is primarily used for manufacturing various gauges, measuring tools, and mold components such as punching dies with large cross-sectional dimensions, complex shapes, and stringent requirements for minimal quenching distortion—applications where carbon tool steel cannot meet the specifications.