20Cr Steel Grade
20Cr steel is a kind of Chinese GB standard alloy steel. It has good comprehensive mechanical properties after quenching and low temperature tempering: good low temperature impact toughness and temper brittleness is not obvious. When carburizing, the grain of steel has a tendency to grow, so secondary quenching is required to improve the toughness of the core, and it is not suitable for cooling and quenching. When the hardness after normalizing is 170-217 HB, the relative machinability is about 65%. 20Cr steel has good weldability, and generally does not require heat treatment after welding, but parts with a thickness greater than 15mm need to be preheated to 100-150 °C before welding, and tempering heat treatment may not be performed after welding.
Compared with 15Cr steel, 20Cr has higher strength and hardenability. The critical hardenable diameter in oil is 4-22mm, and the critical hardenable diameter in water is 11-40mm, but the toughness is poor. The machinability is good under high temperature normalizing or quenching and tempering conditions, but it is poor after annealing.
Chemical Composition
| Chemical Composition (%) | |||||||||
| Grade | C | Si | Mn | Cr | P ≤ | S ≤ | Cu ≤ | Ni ≤ | Mo ≤ |
| 20Cr | 0.18 – 0.24 | 0.17 – 0.37 | 0.50- 0.80 | 0.70 – 1.00 | 0.030 | 0.030 | 0.030 | 0.030 | 0.030 |
Mechanical Properties
- Tensile strength: ≥835 N/mm2
- Yield strength: ≥540 N/mm2
- Elongation after break: ≥10%
- Rate of reduction in area: ≥40%
- Impact absorbing energy: ≥47 J
- Material Brinell hardness: ≤179 (annealing or high temperature tempering state)
- Test sample size: 15mm
Heat treatment specification
- First quenching heating temperature: 880 °C (Cooling: oil, water)
- Second quenching heating temperature: 780-820 °C (Cooling: oil, water)
- Tempering heating temperature: 200 °C (Cooling: water, air)
Applications
Machine gearbox gears, gear shafts, cams, worms, piston pins, dog clutches, etc.
Equivalent Grades
20Cr steel equivalent to US ASTM AISI, European Germany DIN EN, British BS EN, France NF EN, Japanese JIS and ISO standard.
| 20Cr Equivalent | |||||||||||||
| China | USA | Germany | Japanese | France | UK | ISO | |||||||
| Standard | Grade | Standard | Grade | Standard | Grade | Standard | Grade | Standard | Grade | Standard | Grade | Standard | Grade |
| GB/T 3077 | 20Cr | AISI SAE 5120; ASTM A29/A29M |
5120 | JIS G4503 | SCr420 | ISO 683-17 | 20Cr3 | ||||||
