4Cr5MoSiV is a Chinese national standard grade, equivalent to AISI H11 in the United States. Compared with 4Cr5MoSiV1(AISI H13/DIN 1.2343), the vanadium content in the composition of 4Cr5MoSiV is lower. 4Cr5MoSiV1 generally has higher hot strength and hardness, and is more widely used, but 4Cr5MoSiV is still favored for high-speed hammer forging dies due to its excellent thermal fatigue resistance.

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

C	Si	Mn	Kr	Mo	V	P	S
0.33 – 0.43%	0.80 – 1.20%	0.20 – 0.50%	4.75 – 5.50%	1.10 – 1.60%	0.30 – 0.60%	≤0,030%	≤0,030%

2. Physical Properties of 4Cr5MoSiV

2.1 Temperatury krytyczne

Punkt krytyczny	Ac₁	Ac₃	Ar₁	Ar₃	SM	Mf
Temperatura (w przybliżeniu) / °C	853	912	720	773	310	103

2.2 Współczynnik rozszerzalności liniowej

Temperatura / °C	20 ~ 100	20 ~ 200	20 ~ 300	20 ~ 400	20 ~ 500	20 ~ 600	20 ~ 700
Coeff. of Linear Expansion α / 10⁻⁶ °C⁻¹	10.0	10.9	11.4	12.2	12.8	13.3	13.6

2.3 Przewodność cieplna

Temperatura / °C	100	200	300	400	500	600	700
Przewodność cieplna λ / [W/(m·K)]	25.9	27.6	28.4	28.0	27.6	26.7	25.9

2.4 Moduł sprężystości

Temperatura / °C	20	100	200	300	400	500
Modulus of Elasticity E / MPa	227,000	221,000	216,000	208,000	200,000	192,000

2.5 Density and Specific Heat Capacity

Gęstość / (g/cm³)	Ciepło właściwe cₚ (20°C) / [J/(kg·K)]
7.69	459.8

3. Gorąco Forging Process Specification for 4Cr5MoSiV Steel

Przedmiot	Temperatura ogrzewania / °C	Temperatura początkowego kucia / °C	Temperatura końcowego kucia / °C	Metoda chłodzenia
Sztabka stali	1140 ~ 1180	1100 ~ 1150	≥900	Sand cooling or pit cooling
Kęsy stalowe	1120 ~ 1150	1070 ~ 1100	850 ~ 900	Sand cooling or pit cooling

4. Heat Treatment of 4Cr5MoSiV

4.1 Podgrzewanie wstępne

Wstępny plan obróbki cieplnej	Parametry procesu
Wyżarzanie po kuciu	Heating temperature 860 ~ 890°C, hold for 2 ~ 4h; furnace cool to below 500°C then air cool. Hardness after annealing ≤229HBW.
Wyżarzanie odprężające	Heating temperature 730 ~ 760°C, hold for 3 ~ 4h, furnace cool or air cool.

4.2 Hartowanie

① Zalecana specyfikacja procesu hartowania

Quenching Temperature / °C	Medium hartujące	Quenching Medium Temperature / °C	Subsequent Step	Twardość HRC
1000 ~ 1030	Olej lub powietrze	20 ~ 60	Cool to oil temperature	53 ~ 55

② Relationship between Quenching Temperature and Hardness

Quenching Temperature / °C	950	975	1000	1025	1050	1075	1100
Twardość HRC	51	53	54.5	56	58	58.5	57.5

4.3 Hartowanie

① Zalecana specyfikacja procesu hartowania

Cel hartowania	Temperatura / °C	Sprzęt	Chłodzenie	Liczba temperamentów	Twardość HRC
Eliminate stress and reduce hardness	530 ~ 580	Molten salt bath furnace or air furnace	Chłodzenie powietrzem	2	47 ~ 49

Note: The second tempering temperature is usually 20 ~ 30°C lower than the first.

② Mechanical Properties after Tempering at Different Temperatures

Temperatura odpuszczania / °C	500	550	600	650
Twardość HRC	57	54.5	46.5	37
aᴋ / (J/cm²)	20	45	60	66

Note: 1000°C air cool, 580°C temper.

4.4 Recommended Surface Strengthening Treatment Process Specification

Proces	Temperatura / °C	Time / h	Średni	Layer Thickness / mm	Surface Hardness HV
Azotowanie	560	2	KNO₃ 50% + NaNO₃ 50% (Mass Fraction)	0.04	640 ~ 690
Azotowanie	580	8	Gaz ziemny + amoniak	0.25 ~ 0.30	830 ~ 860
Azotowanie	540	12 ~ 20	Ammonia decomposition rate 30% ~ 60%	0.15 ~ 0.20	550 ~ 750

5. Właściwości mechaniczne

4Cr5MoSiV (H11) steel is an air-cooling hardening type hot-work tool steel. It has good toughness, and after heat treatment strengthening, its strength can reach over 2070 MPa. Because it can be hardened in air, quenching deformation and residual stress are small, and the tendency for surface oxidation is also small. It can produce a secondary hardening phenomenon and can achieve optimal performance when tempered above 510°C. After high-temperature tempering, most of the internal stress can be eliminated. It has good thermal stability and can resist the erosion of molten aluminum alloy. Below 650°C, it has high ductility, impact toughness, oxidation resistance, thermal fatigue resistance, as well as high creep strength and tensile strength.

5.1 High-Temperature Mechanical Properties

Test Temperature / °C	Rₘ / MPa	Rₑₗ / MPa	A (%)	Z (%)
300	1504	1311	12.0	39.1
600	895	794	21.9	72.9
650	471	402	33.1	85.5
700	226	179	55.0	94.5

5.2 High-Temperature Hardness

Test Temperature / °C	300	450	600	650	700	750
Twardość HV	491.5	448.5	384.0	302.5	227.5	178.5

Note: Original hardness of the specimen 49~50HRC.

5.3 High-Temperature Impact Toughness

Test Temperature / °C	300	600	650	700
Impact Absorption Energy K / J	28.8	31.0	36.5	70.0

5.4 Thermal Fatigue Performance

	Stopień
20 ~ 650°C repeated 1000 times	8.2
20 ~ 750°C repeated 1000 times	14.6

5.5 Thermal Wear Resistance

4Cr5MoSiV Steel Thermal Wear Resistance (I)

Rotations/times	300	600	900	1200	1500	2500
Weight Loss / mg	0.67	0.80	1.4	1.63	1.97	2.62

Note: Test temperature 800 ~ 850°C, pressure 784 ~ 882N, specimen hardness 49 ~ 50HRC.

Table 5-89 4Cr5MoSiV Steel Thermal Wear Resistance (II)

Rotations/times	100	200	300	400	500	600	700	1000
Weight Loss / mg	0.77	1.67	2.50	3.47	4.33	4.90	5.60	7.40

Note: Test temperature 910 ~ 950°C, pressure 1784 ~ 1813N, specimen hardness 49 ~ 50HRC.

5.6 Tempering Resistance

Temperatura / °C	500 (Secondary Hardening Peak Temperature)	560	615	600	653
Twardość HRC	55.0 (Highest Secondary Hardening Hardness)	49.0	42.0	36.0	35.0

Note: Specimen quenched in oil at 1020°C, hardness 59~60HRC.

5.7 Thermal Corrosion Resistance

Test Temperature and Time	620°C × 4h	680°C × 4h
Weight Loss / (g/dm²)	4.4188	16.4

5.8) Fatigue Limit

Test Temperature / °C	Room Temp	300	400	450	500
σ-1 / MPa	880	680	640	630	610
σ-1k / MPa	570	440	430	—	420

5.9 Thermal Stability of 4Cr5MoSiV Steel at 620°C

Holding Time / h	2	4	6	8	11.5	14.5	17.5	21
Twardość HRC	39.4	38.4	36.9	35.1	34.4	33.2	32.6	32.3

Note: Original hardness of the specimen was 49.9 HRC.

6. Zastosowania

4Cr5MoSiV (H11) steel is commonly used for manufacturing die-casting molds for aluminum castings, hot extrusion dies, tools and core rods for piercing, press forging dies, plastic molds, etc. Additionally, due to its good medium-temperature strength, it is also used for manufacturing structural components for aircraft, rockets, and parts for steam turbines and gas turbines.