As a high-quality carbon structural steel, C40 is defined as a non-alloy steel with an average carbon content of about 0.4% as per European standards.
C40 steel has high strength and good machinability, medium cold deformation plasticity, but poor in weldability and hardenability.
C40 steel is used in normalized or quenched and tempered condition.It is often used to manufacture small cross-section quenched and tempered parts with large load, large normalized parts with small stress, and surface hardened parts with low requirements on core strength and wear-resistant surface.
C40 STEEL CHEMICAL COMPOSITION
| Standard | Grade | C | Si | Mn | P | S | Cr | Mo | Ni |
| EN10083 | C40/1.0511 | 0.37-0.44 | ≤0.4 | 0.50-0.80 | ≤0.045 | ≤0.045 | ≤ 0.4 | ≤ 0.1 | ≤ 0.4 |
| EN10250 | |||||||||
| DIN 17200 | CK40/1.1186 | 0.37-0.44 | ≤0.4 | 0.50-0.80 | ≤0.035 | ≤0.03 | - | - | - |
C40 STEEL RELATED STANDARD & EQUIVALENT GRADE
China | GB 3077:40
USA | ASTM A29:1040
Japan | JIS G4051:S40C
UK |BS970:080M40
France | NFA 33-101:AF60-C40
C40 STEEL FORGING
- Initial Forging Temperature：1200℃
- Final Forging Temperature：850℃
- Forging Ratio：above 4:1
- Post-Forging Treatment:C40 steel should be slowly cooling after forged.
C40 STEEL HEAT TREATMENT
Critical Temperature for Heat Treatment of C40 Steel
- Ac1:724℃
- Ac3:790℃
- Ar1:680℃
- Ar3:760℃
Temperature Selection for Conventional Heat treatment for C40 Steel
- Annealing:840 – 870°C,Cooling in furnace,hardness below 187 HBW
- Normalizing:840-890°C,Cooling in air,hardness about 207HBW
Annealing Diagram for C40 Steel
Normalizing Diagram for C40 Steel
- Quenching:830-870°C,Medium:Water,Oil
- Tempering:550-660°C
C40 Steel Mechanical Property with Quenched and Tempered Condition
| Tensile Strength Mpa | Yield Strength Mpa | Elongation % | Reduction of Area % | Impact Charpy-V J |
| ≥570 | ≥335 | ≥19 | ≥45 | ≥47 |
C40 Steel Tempering Temperature Vs Hardness
| Grade | Quenching | Tempering Temperature,ºC | ||||||||
| Temperature,ºC | Hardness,HRC | 150ºC | 200ºC | 300ºC | 400ºC | 500ºC | 550ºC | 600ºC | 650ºC | |
| C40 | 840ºC | 54-55 | 55 | 53 | 48 | 42 | 34 | 28 | 23 | 20 |
Jominy Quenching Test Curve For C40E Steel
Quenching at 870°C
X:Distance from quenched end,in mm
Y:Hardness,HRC
3: H level
| HRC-mm | Type | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 13 | 15 |
| MIN | +H | 60 | 60 | 59 | 57 | 53 | 47 | 39 | 34 | 31 | 30 | 29 | 28 | 27 |
| MAX | 51 | 46 | 35 | 27 | 25 | 24 | 23 | 22 | 21 | 20 | - | - | - |
Guideline value Curve for C40 Steel Mechanical Property
X:Tempering temperature,oC
Y:Tensile and Yield Strength,Mpa
Z:Elongation and Reduction in area,%
WHAT WE SUPPLY FOR C40 STEEL
Hot Forged Round bar:Φ80-Φ1000mm
Hot Rolled Round bar:Φ16-Φ350mm
Hot Forged Square bar: Max Thickness:500mm
Flat bar/Blcoks:Thickness :120-800mm ,Width:120-1500mm
| 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 |
