4Cr3Mo3SiV is the designation under China’s GB/T standard, and its equivalent steels are ASTM/AISI H10 in the United States, JIS SKD7 in Japan, DIN 1.2365 in Germany, and 32CrMoV12-28. 4Cr3Mo3SiV is a medium-alloy hot work tool steel. It is designed with a good balance of strength, toughness, and wear resistance at elevated temperatures. Compared to 4Cr5MoSiV1 (H13) steel, it has higher thermal strength but slightly lower impact toughness. Its thermal stability surpasses both H13 and 3Cr2W8V (H21) steels.

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

C	Si	Mn	Cr	Mo	V	P	S
0.35 – 0.45	0.80 – 1.20	0.25 – 0.70	3.00 – 3.75	2.00 – 3.00	0.25 – 0.75	≤0.030	≤0.030

2. Critical Point Temperatures of 4Cr3Mo3SiV

Critical Point	Ac₁	Ac₃	Ms
Temperature (approximate value)/°C	820	900	310

3. 4Cr3Mo3SiV Steel Forging Process Specification

Item	Heating Temperature/°C	Initial Forging Temperature/°C	Final Forging Temperature/°C	Cooling Method
Steel Ingot	1160 ~ 1180	1040 ~ 1170	≥900	Slow Cooling
Steel Billet	1150 ~ 1170	1120 ~ 1140	≥850	Slow Cooling

4. Heat Treatment of 4Cr3Mo3SiV

4.1 Preheating

Material	Heating Temperature/°C	Holding Time	Isothermal Time	Cooling Method
Bar Stock	860 ~ 880	2h + 1min/mm	—	Furnace cool to below 500°C, then air cool
Forgings	860 ~ 880	1h + 1min/mm	730°C × 2h + 1min/mm	Air cool from furnace

4.2 Quenching

First Preheating	Second Preheating	Austenitizing Temperature/°C	Cooling Medium	Hardness HRC
550°C uniform heating	880°C uniform heating	1030 ± 10	Oil	55 ~ 56

4.3 Tempering

First Tempering	Second Tempering	Hardness HRC
610°C × 2h	615°C × 2h	47.0 ~ 49.0

5. Mechanical Properties of 4Cr3Mo3SiV

4Cr3Mo3SiV contains many carbide-forming elements such as Cr, Mo, and V. It has good toughness and exhibits high hardness, thermal strength, and wear resistance at operating temperatures of 500~600 °C. This steel has good hardenability, resistance to tempering, and thermal stability, resulting in very high toughness, high impact toughness, and fracture toughness, as well as good oxidation resistance.

5.1 Room Temperature Mechanical Properties

Specimen Hardness HRC	Rm/MPa	ReL/MPa	A (%)	Z (%)	KU/J	KIc/MPa·1/2
47 ~ 49	1559	1356	10.1	34.1	16.9	41.2

5.2 High-Temperature Mechanical Properties

Temperature/°C	Rm/MPa	ReL/MPa	A (%)	Z (%)	KU/J	Vickers Hardness HV
300	1349	1218	10.4	29.3	20.5	471.5
600	888	779	20.3	69.8	25.2	409.0
650	651	596	19.5	60.7	20.9	360.5
700	298	261	31.2	81.6	23.2	278.5

5.3 Thermal Stability

Tempering Temperature (°C)	Holding Time (h)	Hardness (HRC)
620	0	47.5
	2	44.1
	4	43.8
	6	42.2
	8	41.3
	11.5	38.6
	14.5	37.6
	17.5	35.4
	21	33.8
660	0	46.9
	1	40.3
	2	34.9
	3	33.8
	5	31.5
	7	29.8
	9	29.5
	12	26.8
700	0	46.6
	0.5	33.5
	1	29
	1.5	28.3
	2	25.8
	3	—

5.4 Fatigue Performance

Test Condition	20°C ↔ 650°C (1000 cycles)	20°C ↔ 700°C (1000 cycles)
47 ~ 49HRC	Grade 7.6	Grade 15.6

6. Applications of 4Cr3Mo3SiV

4Cr3Mo3SiV steel is widely used for various hot work tooling and components:

• Hot Extrusion Dies: Especially for core rods, liners, and mandrels.
• Hot Forging Dies: For thermal forging, precision forging, roll forging, and hammer forging dies.
• Hot Punching Dies: Used for hot punches and hot pressing dies.
• Die-Casting Molds: Suitable for aluminum, magnesium, and copper alloy die-casting molds.
• Other Applications: Hot cutting tools, pressure tools, and components requiring good impact resistance and hardness at elevated temperatures. It can replace 3Cr2W8V in many applications.