S20C 
 S20C 
 Executive Standard: JIS G4051-2005 
 ● Features and Scope: S20C steel strength higher than 15, very little quenching, no temper brittleness. Cold plastic deformation is high, generally for bending, rolling, curved edges and hammer arch and other processing, and exposure to welding arc welding performance is good, when welding a small thickness, shape, or form a complex demanding parts prone to crack on. Machinability than cold-drawn or annealed state a good state of normalizing, S20C discontinuity generally used in the manufacture of large parts requiring high toughness. 
 (1) characteristics of cold extrusion, carburized hardened steel. The low-carbon steel is carbon steel, the steel low intensity, toughness, ductility and weldability are good. Yield strength ≥ 245MPa, tensile strength ≥ 245MPa, elongation ≥ 28%. Normalizing can promote organizational goals, thinning large block-eutectoid ferrite and improve the cutting performance of less than 160HBS rough. 
 (2) delivery status is not heat-treated state. 
 (3) chemical composition (mass fraction,%) C 0.18-023, Si 0.15-0.35, Mn 0.30-0.60, P ≤ 0.030, S ≤ 0.035. (4) refer to the corresponding steel in China GB / JB standard steel No. 20, China's Taiwan CNS standard steel S20C, the German DIN standard material number 1.0402, DIN steel CK22/C22, the British BS standard steel IC22, France AFNOR standard steel CC20, the French NF standards steel C22, the Italian UNI standard steel C20/C21, Belgium NBN standard steel No. C25-1, the Swedish standard steel SS 1450, Spain UNE standard steel F.112, USA AISI / SAE 1020 steel standard, JIS standard steel S20C/S22C. (5) phase transition temperature (approximate) Ac1 = 720-845 ℃, Ar1 = 815-730 ℃ 
 (6) cold rough handling practices softening temperature of 700-720 ℃, holding time 8-15h, to 50-100 ℃ / h of cooling rate, lower the temperature ≤ 550-600 ℃, baked cooled. Treatment before the hardness ≤ 143HBS, treatment hardness ≤ 131HBS. 
 (7) normalizing standard temperature 870-920 ℃, baked cooled. 
 (8) standard annealing temperature of about 860 ℃, baked cooled. (9) quenching regulate temperature 910 ℃ ± 10 ℃, 10% NaCl brine cooling. Performance and application intensity slightly higher than the S15C steel, welding, and no temper brittleness, can improve the machinability by water quenching. Uses: used in the manufacture are not subjected to great stress and high toughness requirements of various mechanical parts. In the general machinery and automobiles, agricultural machinery for the manufacture of high surface hardness of heart is not required by the Ministry carburizing and carbonitriding parts.