Production specification: Outer diameter of steel pipe 20-426 Steel pipe wall thickness of 20-426 Steel pipe standard: According to standard GB/T 3077-2008: chemical composition (mass fraction, %) C 0.37~0.44, Si 0.17~0.37, Mn 0.50~0.80, Cr0.80~1.10, Ni≤0.30. 【 Mechanical properties 】 Sample blank size (mm) : 25 Heat treatment: First quenching heating temperature (℃) : 850; Coolant: Oil Second quenching heating temperature (℃) : - Tempering heating temperature (℃) : 520; Coolant: water, oil Tensile strength (σb/MPa) : ≧980 Yield point (σs/MPa) : ≧785 Elongation after breaking (δ5/%) : ≧9 Reduction rate of cross-section (ψ/%) : ≧45 Impact absorption work (Aku2/J) : ≧47 Brinell hardness (HBS100/3000) (annealing or high-temperature tempering condition) : ≦207