Chemical composition:
Chemical Composition
C Si Mn P S Ni Cr Cu
≤
50 0.47 to 0.55 0.17 to 0.37 0.50 to 0.80 0.30 0.25 0.25 0.035 0.035
55 0.52 to 0.60 0.17 to 0.37 0.50 to 0.80 0.30 0.25 0.25 0.035 0.035

Mechanical properties:
Grades blank sample
Size
/ mm heat treatment process of the mechanical properties of the steel hardness delivery status
/ HBS
Normalizing quenching and tempering σb / MPa σs / MPa δ5 (%) ψ (%) Ak / J ≤
≥ No heat annealed steel
50 25 8,308,306,006,303,751,440 31 241 207
55 25 820 820 6,006,453,801,335,255,217

Characteristics and Uses:
50: for the manufacture of high wear resistance, dynamic load and impact of little parts, such as casting gear, rod, roll, etc.; manufacture relatively minor springs digging on Plowshare agricultural, heavy-duty spindles and shaft, and manufacture castings.
55: for the manufacture of connecting rods, rollers, gears, flat springs, wheels, rims, etc., but also for casting.