Many different types of steel, usually divided by the number of elements in low alloy steel (content <5%), in alloy steel (content of 5% to 10%), high alloy steel (> 10%); according to quality into high-quality alloy steel, alloy characteristics ● implementation of standards
China: GB / T 3203-1982
Japan: JIS G4053-2003
U.S. ASTM A534-2004
(Cementite) bearing steel: SNCM420
● Features and application: It is a commonly used alloy, carburization treatment has a high surface hardness, wear resistance and contact fatigue strength, while the Department has retained a good heart toughness that can withstand high impact loads. Mainly for railway bearings impact resistant, wear parts. ● Chemical Composition:
Carbon C: 0.17 ~ 0.23 (tolerance: ± 0.02)
Si Si: 0.15 ~ 0.40 (tolerance: ± 0.03)
Manganese Mn: 0.40 ~ 0.70 (tolerance: ± 0.04)
Sulfur S: ≤ 0.030 (tolerance: 0.005)
Phosphorus P: ≤ 0.030 (tolerance: 0.005)
Chromium Cr: 0.35 ~ 0.65 (tolerance: ± 0.15)
Ni-Ni: 1.60 ~ 2.00 (tolerance: ± 0.05)
Copper Cu: ≤ 0.30 (Tolerance: +0.05)
Mo Mo: 0.20 ~ 0.30 (tolerance: ± 0.02)
● Mechanical Properties:
Tensile strength σb (MPa): ≥ 980 (100)
Elongation δ5 (%): ≥ 13
Reduction of area ψ (%): ≥ 45
Impact toughness αkv (J/cm2): ≥ 78 (8)
Sample Size: Sample size is 25mm
● Heat treatment and microstructure specifications:
Standard heat treatment: quenching, the first 880 ± 20 ℃, the second 800 ± 20 ℃, oil cooling; tempering, 150 ~ 200 ℃, air-cooled.
Microstructure: carburized layer of high carbon martensite. Department for low-carbon martensite heart.
● Delivery status: hot-rolled or forged steel with hot-rolled (forged) state or annealed state delivery. Cold-drawn steel in the annealed condition delivered.