42CrMo steel belongs to plastic mold steel in terms of material classification, with good mechanical properties and machinability. It is widely used, mainly in two types of materials: plates and round bars. Plates are used for mold processing and production, while round bars are used for direct mechanical processing of parts, and have been recognized by the industry.
42CrMo steel is a type of ultra-high-strength steel with high strength and toughness, good hardenability, no obvious temper brittleness, and after tempering treatment, it has a high fatigue limit and resistance to multiple impacts, as well as good low-temperature impact toughness. 42CrMo steel is suitable for manufacturing large and medium-sized plastic molds that require certain strength and toughness. Composition: Carbon C: 0.38-0.45%, Silicon Si: 0.17-0.37%, Manganese Mn: 0.50-0.80%, Sulfur S: residual content ≤0.035%, Phosphorus P: residual content ≤0.035%, Chromium Cr: 0.90-1.20%, Nickel Ni: residual content ≤0.30%, Copper Cu: residual content ≤0.30%, Molybdenum Mo: 0.15-0.25%.
Hardness: Annealed, 255-207HB, indentation diameter 3.8-4.2mm; quenched, ≥60HRC. Cr12MoV plate has better hardenability, hardness, strength, and toughness after quenching and tempering compared to CR12. For workpieces with a diameter below 300-400mm, complete hardening can be achieved, with minimal deformation during quenching, but poor high-temperature plasticity. Cr12MoV plates are mainly used to manufacture complex-shaped molds and tools with large cross-sections and heavy workloads.
Specifications in different countries include: Russia ГOCT 38XM, USA AISI 4140/4142, UK BS 708M40/708A42/709M40, France NF 40CD4/42CD4, Germany DIN 41CrMo4/42CrMo4, Japan JIS SCM4, International ISO 683/1 3 hot working specifications.
Heating temperature: 1150-1200°C, starting temperature: 1130-1180°C, ending temperature >850°C. For diameters >50mm, slow cooling is recommended.
Normalizing specifications:
Normalizing temperature: 850-900°C, air cooling after furnace.
High-temperature tempering specifications:
Tempering temperature: 680-700°C, air cooling after furnace.
Quenching and tempering specifications:
Preheating temperature: 680-700°C, quenching temperature: 840-880°C, oil quenching, tempering temperature: 580°C, water or oil cooling, hardness ≤217HBW.
Subcritical quenching and toughening treatment specifications:
Quenching temperature: 900°C, tempering temperature: 560°C, hardness (37±1) HRC.
Induction quenching and tempering specifications:
Quenching temperature: 900°C, tempering temperature: 150-180°C, hardness: 54-60HRC.
