50Mn2, alloy structural steel. Standard: GB / T 3077-1999 
 [Main features] This is a high strength quenched and tempered carbon manganese steel, it has high strength, elasticity and abrasion resistance, and hardenability is high, the critical quenching in oil, diameter 10 ~ 28mm, the critical water quenching diameter 24 ~ 49mm, can still be cutting. This steel is obtained after quenching the higher mechanical properties, but when heat-sensitive and heat treatment temper brittleness, water quenching, also have a tendency to crack, and the dialogue point sensitive welding, poor, cold plastic deformation is low. 
 [Application examples] This steel is usually tempered with, for the manufacture of high stress and work under conditions of wear and tear of parts, manufacturing parts below 80mm diameter steel and 45Cr similar performance; can also be returned in normalizing and high-temperature After the fire used for the manufacture of medium load, cross-sectional size larger parts. For example: heavy machinery used in the spindle bearing, gear shaft and large; car on the drive spline shaft and shock loading of the mandrel; general machinery for gear, worm gear shaft, crankshaft, connecting rod, etc. In addition, this can also be used to produce steel plate spring and the flat coil springs and so on. Chemical composition 
 [Chemical composition] (wt) (%) Carbon C: 0.47 ~ 0.55 Si Si: 0.17 ~ 0.37 Manganese Mn: 1.40 ~ 1.80 Phosphorus P: ≤ 0.025 (residual content) of sulfur S: ≤ 0.025 (residual content) chromium Cr: ≤ 0.30 (residual content) Ni-Ni: ≤ 0.30 (residual content) copper Cu: ≤ 0.25 (residual content) 
 50Mn2 
 Mechanical Properties 
 [Mechanical Properties] sample blank size (mm): 25 Heat treatment: first quenching temperature (℃): 820; Coolant: Oil second quenching temperature (℃): - tempering heating temperature (℃): 550 ; coolant: water, oil and tensile strength (σb / MPa): ≧ 930 Yield point (σs / MPa): ≧ 785 Elongation (δ5 /%): ≧ 9 section shrinkage (ψ /%): ≧ 40 Impact absorbed energy (Aku2 / J): ≧ 39 Brinell hardness (HBS100/3000) (annealing or tempering state): ≦ 22 
 50Mn2