20CrMnSi 20CrMnSi, the Chinese national standard [1] of an alloy structural steel grades. Uniform digital code: A24202. 
 20CrMnSi alloy steel 
 Standard: GB / T 3077-1988 Chemical Composition: C: 0.17 ~ 0.23 Si Si: 0.90 ~ 1.20 Manganese Mn: 0.80 ~ 1.10 S S: to allow the residual phosphorus content ≤ 0.035 P: ≤ 0.035 to allow the residual content of chromium Cr: 0.80 ~ 1.10 Ni: to allow the residual content ≤ 0.030 Copper Cu: allow the residual content ≤ 0.030 ● Mechanical Properties: Tensile σb (MPa): ≥ 785 (80) yield strength σs (MPa): ≥ 635 (65) Elongation δ5 (%): ≥ 12 Reduction of area ψ (%): ≥ 45 Impact energy Akv (J): ≥ 55 impact toughness αkv (J/cm2): ≥ 69 (7) Brinell hardness (HBS100/3000) (annealing or high-temperature tempered condition): ≦ 207 Sample size: Sample size of 25mm rough microstructure and heat treatment specifications: Heat treatment specifications: quenching 880 ℃, oil-cooling; tempering 480 ℃, water-cooled, oil-cooling. Microstructure: Tempered sorbite + acicular ferrite. Delivery status: to heat treatment (normalizing, annealing, or tempering) or heat treatment delivery, delivery status should be indicated in the contract. Main features high strength and toughness, high cold plastic deformation processing, stamping better performance, suitable for cold drawing, cold rolling and other cold process. Better welding performance, low hardenability, tempering brittle, generally not used for carburizing or heat treatment. Necessary, can also be used after quenching and tempering [2]. 
 Application examples 
 Used in the manufacture of welded high strength, good toughness by the tension of the parts, and less than 16mm thick piece of sheet metal, cold-drawn parts, cold red parts, such as large mining equipment in the cross-section of the chain, chain link , bolts, etc.