Composition of grade 20Cr steel, properties, equivalent material

20Cr steel grade

20Cr steel is a type of Chinese GB standard alloy steel. It has good comprehensive mechanical properties after quenching and low-temperature tempering: good low-temperature impact resistance and brittleness in tempering are not obvious. During carburizing, the steel grain has a tendency to grow, therefore secondary quenching is necessary to improve the toughness of the core and is not suitable for cooling and quenching. When the hardness after normalization 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 thicker than 15mm need to be preheated to 100-150°C before welding, and quenching heat treatment cannot be carried out after welding.

Compared with 15Cr steel, 20Cr has greater strength and hardenability. The oil hardenable critical diameter is 4 to 22 mm, and the water hardenable critical diameter is 11 to 40 mm, but the toughness is low. Machinability is good under high temperature normalizing or quenching and tempering conditions, but is poor after annealing.

Chemical composition

Mechanical properties

• Tensile strength: ≥835 N/mm2
• Yield resistance: ≥540 N/mm2
• Elongation after rupture: ≥10%
• Area reduction rate: ≥40%
• Impact absorption energy: ≥47 J
• Brinell hardness of material: ≤179 (annealing or high temperature quenching 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)
• Quenching heating temperature: 200°C (Cooling: water, air)

Forms

Machine gearbox gears, gear shafts, cams, worms, piston pins, dog clutches, etc.

Equivalent Notes

20Cr steel equivalent to US ASTM AISI, European Germany DIN EN, British BS EN, France NF EN, Japanese JIS and ISO standard.