24 July 2021 Ball Bearing Steel Bar
SNCM420 Ball Bearing Steel Bar
SNCM420 is a commonly used steel for making bearings. After carburizing, the surface of the steel has high hardness, wear resistance and contact fatigue strength. At the same time, the core retains good toughness and can withstand high impact loads. SNCM420 is mainly used for railway bearings, drive shafts, gears, screws, cutting tools and other products which need impact resistance and wear resistance.
Equivalent to ASTM 4320 , SNCM420 is a kind of alloy carburizing steel as SNCM220. The mechanical properties between SNCM420 and SNCM220 are almost the same. The surface of SNCM420 is high hardness and has good performance in abrasion resistance and contact fatigue strength. Its core which has high toughness can withstand high impaction. There are two differences between SNCM420 and SNCM220 which are the standard and the amount of Ni content. The Ni content of SNCM420 is more than the one of SNCM220.
Chemical composition:
| C(％) | Si(％) | Mn(％) | P(％) | S(％) | Cr(％) | Ni(％) | Mo(％) | Cu(%) |
|---|---|---|---|---|---|---|---|---|
| 0.17-0.23 | 0.15-0.35 | 0.40-0.70 | 0.030 | 0.030 | 0.40-0.65 | 1.60-2.00 | 0.15-0.30 | 0.30 |
Mechanical properties:
| Yield Rp0.2 (MPa) | Tensile Rm (MPa) | Impact KV/Ku (J) | Elongation A (%) | Reduction in cross section on fracture Z (%) | As-Heat-Treated Condition | Brinell hardness (HBW) |
|---|---|---|---|---|---|---|
| 549 (≥) | 132 (≥) | 11 | 11 | 32 | Solution and Aging, Annealing, Ausaging, Q+T,etc | 443 |
| Temperature (°C) | Modulus of elasticity (GPa) | Mean coefficient of thermal expansion 10-6/(°C) between 20(°C) and | Thermal conductivity (W/m·°C) | Specific thermal capacity (J/kg·°C) | Specific electrical resistivity (Ω mm²/m) | Density (kg/dm³) | Poisson’s coefficient, ν |
|---|---|---|---|---|---|---|---|
| 43 | - | - | 0.21 | - | |||
| 547 | 937 | - | 44.3 | 443 | - | ||
| 467 | - | 21 | 31.2 | 423 | 441 |
Heat treatment specifications and microstructure:
Heat treatment specifications: quenching, the first 880 ± 20 ℃, the second 800 ± 20 ℃, oil cold; tempering, 150 ~ 200 ℃, air-cooled.
Metallographic organization: carburizing layer of high-carbon martensite.