40Mn2, alloy structural steel. Standard: GB / T 3077-1999 

 [Main features] This is a quenched and tempered carbon manganese steel, the strength of steel, plastic and wear resistance are high, cutting and heat treatment process can be also good performance in the critical oil quenching diameter of 8.5 ~ 23mm, critical in the water quenching diameter 20 ~ 42mm; but there temper brittleness and thermal sensitivity, and easy to crack when quenched. Sensitivity of this steel with white spots, cold plastic deformation is not high, poor welding, you need to 100 ~ 425 ℃ preheating before welding. 
 [Application examples] is generally used in the quenched state, can be used to manufacture heavy-duty work under conditions of parts such as shafts, crankshafts, axle, rod, worm, lever, connecting rod, a load of bolts, screws, reinforcement rings, quenched and tempered springs and other parts. Generally used for small cross-section diameter less than 50mm of the important parts, the steel static strength and fatigue properties of 40Cr steel and are very, it can be used for the generation of 40Cr steel. 
 Chemical composition 
 [Chemical composition] (wt) (%) Carbon C: 0.35 ~ 0.45 Si Si: 0.20 ~ 0.40 Manganese Mn: 1.60 ~ 1.80 P P: "0.030 (residual content) sulfur S:" 0.030 (residual content) chromium Cr: ≤ 0.309 (residual content) Ni-Ni: ≤ 0.30 (residual content) copper Cu: ≤ 0.25 (residual content) 
 40Mn2 
 Mechanical Properties 
 [Mechanical Properties] sample blank size (mm): 25 Heat treatment: first quenching temperature (℃): 840; coolant: water, oil the second quenching temperature (℃): - tempering heating temperature (℃) : 540; coolant: water, tensile strength (σb / MPa): ≧ 885 Yield point (σs / MPa): ≧ 735 Elongation (δ5 /%): ≧ 12 section shrinkage (ψ /%): ≧ 45 impact absorbed energy (Aku2 / J): ≧ 55 Brinell hardness (HBS100/3000) (annealing or tempering state): ≦ 217 
 40Mn2 
 Delivery status: to heat treatment (normalizing, annealing, or tempering) or heat treatment delivery, delivery status should be indicated in the contract.