3Cr2W8V is a grade under the Chinese GB/T standard, and its equivalent grade is ASTM/AISI H21 in the United States. 3Cr2W8V is a high thermal strength hot work tool steel, commonly used for dies that operate under high temperature and stress. It is a ledeburitic steel, meaning it has a microstructure with large primary carbides, which contributes to its high wear resistance at elevated temperatures.

1. Chemical Composition

C	Si	Mn	Cr	W	V	P	S
0.30 – 0.40%	≤0.40%	≤0.40%	2.20 – 2.70%	7.50 – 9.00%	0.20 – 0.50%	≤0.030%	≤0.030%

2. Physical Properties of 3Cr2W8V Steel

2.1 Critical Points of 3Cr2W8V Steel

Critical Point	Ac₁	Ac₃	Ar₁	Ar₃	Ms	Mf
Temperature/°C	850	930	773	835	350	160

2.2 Linear Expansion Coefficient

Temperature/°C	100	200	300	400	500	600	700	800	900	1000
Linear Expansion Coefficient α/ × 10⁻⁶ °C⁻¹	12.0	12.3	12.7	13.1	13.5	13.9	14.5	14.5	12.8	13.3

2.3 Specific Heat Capacity

Temperature/°C	100	200	300	500	800	900
Specific Heat Capacity cₚ/ [J/(kg·K)]	468.2	473	478	685.5	1262.4	660.4

2.4 Thermal Conductivity

Temperature/°C	100	200	700	900
Thermal Conductivity λ/[W/(m·K)]	20.1	22.2	24.3	23.0

2.5 Electrical Resistivity

Temperature/°C	20	200	500	700	900
Electrical Resistivity ρ/ × 10⁻⁶ Ω·m	0.50	0.60	0.80	1.0	1.19

2.6 Other Physical Properties

Density/(g/cm³)	Modulus of Elasticity E/MPa	Shear Modulus G/MPa
7.74	214 000	73 000

3. Hot Forging Process Specification for 3Cr2W8V Steel

Item	Heating Temperature/°C	Initial Forging Temperature/°C	Final Forging Temperature/°C	Cooling Method ①
Steel Ingot	1150 ~ 1200	1100 ~ 1150	850 ~ 900	Air cooling first, then pit or sand cooling
Steel Billet	1130 ~ 1160	1080 ~ 1120	850 ~ 900	Air cooling first, then pit or sand cooling

① After forging, it should be cooled relatively quickly in the air to below Ac₁ (about 700°C), followed by slow cooling (pit cooling, sand cooling, or furnace cooling), or high-temperature annealing can be carried out. If conditions permit, direct red-hot annealing can be performed.

4. Heat Treatment of 3Cr2W8V Steel

4.1 Preheating

① Preliminary Heat Treatment Process Specification

Preliminary Heat Treatment Plan	Process Parameters
Annealing after forging	Heating temperature 800 ~ 820°C, holding for 2 ~ 4h, furnace cooling at < 30 ~ 40°C/h to below 600°C, then air cooling. Hardness after annealing is 207 ~ 255HBW, microstructure is pearlite + carbide.
Isothermal annealing	Heating temperature 800 ~ 820°C, holding for 2 ~ 4h, furnace cooling at < 30 ~ 40°C/h to below 600°C, then air cooling. Hardness after annealing is 207~255HBW, microstructure is pearlite + carbide.

② Hardness and Microstructure after Annealing

Hardness HBW	Microstructure
	Unannealed	After Annealing
207 ~ 255	Troostite + Martensite	Pearlite + Carbide

4.2 Quenching

① Recommended Quenching Process

Quenching Temperature/°C	Quenching Cooling Medium	Quenching Cooling Medium Temperature/°C	Isothermal Holding Temperature/°C	Final Cooling to 20°C	Hardness HRC
1050 ~ 1100	Oil	20 ~ 40	150 ~ 180	Air Cooling	49 ~ 52

Notes:

1. For large dies, use the upper limit of the heating temperature. For small dies, use the lower limit.
2. Large dies should be preheated to 600-650°C for 1-2 hours before continuing to heat.
3. For flame furnace heating, hold for 40 ~ 50 minutes for every 25mm of die thickness. For electric furnace heating, increase the heating time by 40% over the time required for flame furnace heating.

② Common Quenching Processes for 3Cr2W8V Steel

Quenching Plan	Process Parameters
Isothermal Quenching ¹	Heating temperature is 1150°C, followed by oil cooling after holding at 350~450 °C. The microstructure is lower bainite + martensite, with hardness reaching over 47HRC. After isothermal quenching, low-temperature tempering is recommended at a temperature of 340~380 °C.
High-Temperature Quenching ²	Heating temperature is 1150°C, followed by oil cooling after holding at 350~450 °C. The microstructure consists of lower bainite and martensite, with a hardness of over 47HRC. After isothermal quenching, low-temperature tempering is recommended at a temperature of 340~380 °C.

¹ The bainitic structure obtained after isothermal quenching has high strength and toughness. Its tempering resistance is also much better than conventional heat treatment. It has high resistance to thermal shock and low die deformation, which can extend the service life of the die.

² Increasing the quenching heating temperature of 3Cr2W8V steel increases the alloying degree of martensite, resulting in excellent hot strength but slightly lower toughness. It is generally used for manufacturing dies that are not subjected to significant impact forces but require high hot strength, such as extrusion dies, die-casting dies, and press forming dies for copper and aluminum alloys.

③ Relationship between Quenching Temperature and Hardness of 3Cr2W8V Steel

Quenching Temperature /°C	950	1050	1100	1150	1200	1250
Hardness HRC	44	49	52	55	56	57

4.3 Solution Refining and Ultra-Fine Processing

Forged blanks are solution treated at 1200–1250°C to dissolve carbides into austenite, then quenched in hot oil or boiling water, followed immediately by high-temperature tempering or short-term isothermal spheroidizing treatment. High-temperature tempering is conducted at 720–850°C (the upper limit for blank processing and the lower limit for finished dies). Final heat treatment may employ conventional processes, such as oil quenching at 1100°C.

4.4 Termpering

① Recommended Tempering Process Specifications

Tempering Purpose	Heating Temperature/°C	Heating Equipment	Cooling	Hardness HRC
Stress relief, stabilize structure and dimensions	600 ~ 620	Electric furnace	Air cooling	40.2 ~ 47.4

Notes:

1. Large molds should be tempered immediately after quenching. Generally, tempering is required twice (at 620°C and 600°C, for 2-3 hours each time). For large molds with complex shapes, three tempering cycles can be used.
2. When tempering the mold, first place it in the furnace at 350 ~ 400°C for 1-3 hours, then raise the temperature to the final tempering temperature.
3. The tempering holding time should be calculated as 40-45 minutes for every 25mm of thickness.

② Relationship between Tempering Temperature and Hardness

Quenching Condition	Hardness HRC at different Tempering Temperatures (°C)	Untempered	500(°C)	550(°C)	600(°C)	650(°C)	670(°C)	700(°C)
1050°C Oil Quenching	Hardness HRC	49	46	47	43	35	32	27
1075°C Oil Quenching	Hardness HRC	50	47	48	44	36	33	30
1100°C Oil Quenching	Hardness HRC	52	48	49	45	40	36	32
1150°C Oil Quenching	Hardness HRC	55	49	53	50	45	40	34

4.5 Surface Treatment

Nitriding Process Specification

Process	Temperature/°C	Time/h	Medium	Nitrided layer
				Depth/mm	Hardness HV
Gas Nitriding	530	3 ~ 6	NH₃ decomposition rate 30% ~ 60%	0.07 ~ 0.12	1000 ~ 1160

5. Mechanical Properties

3Cr2W8V steel is a typical high-heat-strength hot-work tool steel. Its high content of W and Cr elements promotes carbide formation, resulting in superior high-temperature strength and thermal hardness, along with excellent high-temperature mechanical properties. However, its toughness and plasticity are relatively poor. This steel exhibits a high phase transformation temperature and demonstrates good resistance to thermal fatigue from alternating hot and cold cycles. It exhibits good hardenability, being fully hardenable in sections up to 80 mm in diameter, and possesses relatively high temper resistance.

5.1 Mechanical Properties of 3Cr2W8V Steel at Different Tempering Temperatures

Tempering Temperature/°C	Rm/MPa	Rp0.2/MPa	Z (%)	A (%)
400	1800	1400	36	18
450	4800	1420	35.5	14
500	1800	1450	35	13
550	1760	1500	35.5	12
600	1620	1410	38	8
650	1270	–	36	12

Note: 1100°C oil quenching.

5.2 3Cr2W8V Steel High-Temperature Hardness

Temperatures (°C)	300	450	600	650	700	750
Original Sample Hardness (HRC)	High-Temperature Hardness (HV) at various temperatures (°C)
48.8 ~ 49.1	479.5	448.5	414.5	398.5	354.5	208.5
42.0 ~ 43.0	390	386.5	332	304	268	203.5

5.3 Fatigue Performance Comparison Between 3Cr2W8V Steel and 4Cr5MoSiV1

Steel Grade	Number of Fatigue Cracks	Crack Length / mm
		Total Length	Average Length
3Cr2W8V (H21)	125	2.81	0.023
4Cr5MoSiV1 (H13)	11	0.46	0.041

6. Applications

3Cr2W8V steel is a high-heat-strength hot-work tool steel suitable for manufacturing hot-work dies and dies that endure high stresses at elevated temperatures with minimal impact loads. Examples include dies, core pins, and ejector pins for hot extrusion dies; punches, dies, and inserts for flat forging machines; copper alloy extrusion dies, die-casting molds, or counter-extrusion dies subjected to significant compressive, bending, and tensile stresses simultaneously. It is also used for high-temperature cutting tools in hot metal applications.