Alloy structural steel: 4340 (40crni2moa)

　　U.S. brand numbers: SAE4340, AISI4340

　　Implementation standard: ASTM A29/A29M-04

　　Chemical composition:

　　Carbon C: 0.38-0.43

　　Si: 0.15-0.35

　　Mn: 0.60-0.90

　　Sulfur S: Allowable Residual Content ≤ 0.040

　　Phosphorus p: allowable residual content ≤ 0.035

　　Cr: 0.60-0.90

　　Ni: 1.65 ~ 2.00

　　Cu: Allowable Residual Content ≤ 0.025

　　Mo: 0.20-0.30

　　Mechanical properties:

　　Tensile strength σ b (MPa): ≥ 980 (100)

　　Yield strength σ s (MPa): ≥ 835 (85)

　　Elongation Δ 5 (%): ≥ 12

　　Section shrinkage Ψ (%): ≥ 55

　　Akv (j) of impact power: ≥ 78

　　Impact toughness value α kv (j/cm2): ≥ 98 (10)

　　Hardness: ≤ 269hb

　　Sample size: the sample blank size is 25 mm.

　　Heat Treatment Specification and Metallographic Structure;

　　Heat treatment specification: quenching 850℃, oil cooling; Tempering 600℃, water cooling, oil cooling.

　　Delivery status: delivery in heat treatment (normalizing, high temperature tempering) or annealing status