18CrMo4 is a low carbon case hardening steel which has at least 0.9Cr%,0.15%Mo as strengthening elements as per EN10084 standard.It has good process performance ,and has high strength when temperature at 500-550 °C.The oxidation resistance is deteriorated and the creep strength is remarkably lowered when temperature exceeds 550°C.The weldability of 18CrMo4 steel is also very good, with excellent machining or cutting properties.
1.Supply Form & Size & Tolerance
Hot rolled bar:Φ6-Φ130mm,Length:3000-10000mm
Hot Forged round bar:Φ130-Φ1000mm,Length:3000-10000mm
Flat bar/Blcoks:Thickness :120-800mm xWidth:120-1500mm,Length:2000-6000mm
Surface Finish | Black-Forged | Black-Rolled | Turned | Grinding | Polished | Peeled | Cold Drawn |
Tolerance | (0,+5mm) | (0,+1mm) | (0,+3mm) | Best h9 | Best h11 | Best H11 | Best H11 |
2.Chemical Composition
Grade | C | Si | Mn | Cr | Mo | P | S |
18CrMo4/1.7243 | 0.15-0.21 | ≤ 0.4 | 0.6-0.9 | 0.9-1.2 | 0.15-0.25 | ≤ 0.025 | ≤ 0.035 |
18CrMoS4/1.7244 | 0.15-0.21 | ≤ 0.4 | 0.6-0.9 | 0.9-1.2 | 0.15-0.25 | ≤ 0.025 | 0.02-0.04 |
3.Relevant Standards
USA | UK | Japan | France |
4118 | 708M20 | SCM420 | 18CD4 |
4. Mechanical Property
Diameter d mm | ≤ 16 | 16-40 | 40-100 |
Yield Strength Mpa | ≥835 | ≥685 | ≥590 |
Tensile Strength Mpa | 1080-1370 | 930-1300 | 800-1150 |
Elongation, % | ≥9 | ≥9 | ≥10 |
Reduction of area ,% | ≥35 | ≥35 | ≥40 |
impact,J | ≥25 | ≥31 | ≥31 |
5.Forging
18CrMo4 forging temperature:950 – 1100°C,cooled as slowly as possible in the air or in sand after forged.
6.Heat Treatment
- Normalizing: 870 – 900°C,Cooling in air
- Soft Annealing:680 – 700°C,Cooling in furnace
- Carburizing:880-980°C
- Core-hardening:860-900°C,oil-polymer salt bath
- Case-hardening:780-820°C,oil-polymer salt bath
- Carbonitriding:860-950°C
- Tempering:150-200°C
7.Surface Hardness
- Soft annealed(+A):Max 207HB
- Treated to hardness range(+TH):156-207HB
- Treated to ferrite-pearlite structure and hardness range(+FP):140-187HB
Type | Distance mm | 1.5 | 3 | 5 | 7 | 9 | 11 | 13 | 15 | 20 | 25 | 30 | 35 | 40 |
+H | HRC Min | 39 | 37 | 34 | 30 | 27 | 24 | 22 | 21 | - | - | - | - | - |
HRC Max | 47 | 46 | 45 | 42 | 39 | 37 | 35 | 34 | 31 | 29 | 28 | 27 | 26 | |
+HH | HRC Min | 42 | 40 | 38 | 34 | 31 | 28 | 26 | 25 | 22 | 20 | - | - | - |
HRC Max | 47 | 46 | 45 | 42 | 39 | 37 | 35 | 34 | 31 | 29 | 28 | 27 | 26 | |
+HL | HRC Min | 39 | 37 | 34 | 30 | 27 | 24 | 22 | 21 | - | - | - | - | - |
HRC Max | 44 | 43 | 41 | 38 | 35 | 33 | 31 | 30 | 27 | 25 | 24 | 23 | 22 |
8.Application
18CrMo4 case hardening steel is widely in gear components of all kind and cog wheels. Open die steel forgings for general engineering purposes.High and medium pressure steam pipes, headers and superheaters.