In China’s GB standards, 9Cr18 and 95Cr18 actually refer to the same type of steel. 95Cr18 is the new designation for 9Cr18 steel.
The old designation 9Cr18 originates from the GB/T 1220-1992 standard. It is primarily based on carbon and chromium content, with “9” representing a carbon content of approximately 0.9% and “18” representing a chromium content of approximately 18%.
The new grade 95Cr18 is named according to the latest GB/T 1220-2007 standard. The new naming convention is more standardized, with “95” representing a carbon content of approximately 0.95%, which more accurately indicates the carbon content compared to the old grade.
95Cr18 steel is a high-carbon, high-chromium martensitic stainless steel. It has high hardness, wear resistance, and corrosion resistance. This steel also exhibits good hot plasticity and low heat treatment deformation tendencies.
1. Chemical Composition(GB/T 1220—2007)
C
Si
Mn
Cr
S
P
0.90% to 1.00%
≤0.80%
≤0.80%
17.00% ~ 19.00%
≤0.030%
≤0.040%
For the improved version, “9Cr18Mo” (also known as AISI440C), the composition includes Molybdenum (Mo) typically in the range of 0.40% to 0.70%.
2. Physical Properties of 95Cr18(9Cr18)
Critical Point Temperature
Critical Point
Temperature (approximate) / °C
Ac₁
830
Ar₁
810
Linear Expansion Coefficient
Temperature / °C
Linear Expansion Coefficient α / (10⁻⁶ °C⁻¹)
20 ~ 100
10.5
20 ~ 200
11
20 ~ 300
11
20 ~ 400
11.5
20 ~ 500
12
Other Physical Properties
Property
Value
Density / (g/cm³)
7.7
Modulus of Elasticity E(20°C) / MPa
203,890
Specific Heat Capacity cₚ(20°C) / [J/(kg·K)]
459.8
Thermal Conductivity λ(20°C) / [W/(m·K)]
29.3
Electrical Resistivity ρ(20°C) / (10⁻⁶ Ω·m)
0.6
95Cr18 Stainless Steel
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3. Forging Process of 95Cr18(9Cr18)
Furnace Charging Temperature
Initial Forging Temperature / °C
Final Forging Temperature / °C
Cooling
Cold charging temp. ≤600°C, Hot charging temp. unlimited
1050 ~ 1100
≥850
Furnace cooling
Note: The heating speed of the hot working process should not be too fast. The stop forging (rolling) temperature should be controlled at a higher level, and slow cooling conditions must be strictly followed.
4. Heat Treatment of 95Cr18(9Cr18)
4.1 Preliminary Heat Treatment Specification of 95Cr18 Steel
Preliminary Heat Treatment Plan
Heating Temperature / °C
Cooling Method
Hardness HBW
Softening Annealing
800 ~ 840
Furnace cool to 500°C, then air cool
≤255¹
Full Annealing
840 ~ 860
Furnace cooling
≤255¹
Note: ① The annealed structure is pearlite.
4.2 Quenching and Tempering
4.2.1 Quenching and Tempering Process Specification of 95Cr18 Steel
Quenching Temp. / °C
Cooling Method
Hardness HRC (Quenching)
Tempering Temp. / °C
Hardness HRC (Tempering)
1030 ~ 1070
Oil cooling
≥55
200 ~ 300
56
4.2.2 Hardness, Retained Austenite Content, and Impact Toughness
Quenching Temp. / °C
Hardness HRC
Retained Austenite (vol. fraction, %)
aₖ / (J/cm²)
800
35
—
31
900
48
—
17
950
52
1.7
14
1000
57
5.2
11
1050
60
29.2
10
1100
53
93.9
15
1150
42
97
22
1200
35
99
26
4.2.3 Effect of Different Tempering Temperatures on Hardness and Impact Toughness
Hardness HRC after cooling to -75°C and holding for 1h
Hardness HRC after Tempering (Tempering Temperature)
100°C
150°C
200°C
1000
58
—
58
57
55
1000
59
59.5
59.5
59
57
1050
60
61.5
61
61
59
1100
60.5
62
62
62
60.5
5. Corrosion Resistance of 95Cr18 (9Cr18) Steel
Medium
Mass Fraction (%)
Temperature/℃
Corrosion Rate /mm⋅a-1
Nitric acid
5 – 20
20
< 0.1
5
60 ~ Boiling
< 1.0
20
60
< 0.1
20
80
< 1.0
20
Boiling
2.0 ~ 3.0
40
60 ~ 80
< 1.0
40
Boiling
3.0 ~ 10.0
50
20
< 0.1
50
80
< 1.0
60
20
< 0.1
60
60 ~ 80
< 1.0
60
Boiling
1.0 ~ 3.0
90
20
< 1.0
90
Boiling
3.0 ~ 10.0
Acetic acid
5
20
< 1.0
5
50 ~ 75
3.0 ~ 10.0
5
Boiling
> 10.0
25
50 ~ 75
3.0 ~ 10.0
25
Boiling
> 10.0
50
20
< 0.1
50
50
3.0 ~ 10.0
50
75
> 10.0
Phosphoric acid
1
20
< 0.1
10
20
< 3.0
15
20
3.0 ~ 10.0
Sulfuric acid
5
20
> 10.0
5
50
> 10.0
5
80
> 10.0
Hydrochloric acid
0.5
20
< 1.0
0.5
50
< 3.0
0.5
Boiling
> 10.0
1
20
< 3.0
1
50
3.0 ~ 10.0
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