Chemical composition and mechanical properties of ASTM4140 seamless pipe

Hit：332025-12-17 10:48:47　

The chemical composition and mechanical properties of 4140 seamless pipe are mainly based on standard specifications such as American standard ASTM A519. ‌
Chemical composition
The typical chemical composition (mass fraction) of 4140 seamless pipe is: carbon (C) 0.38%~0.43%, silicon (Si) 0.15%~0.35%, manganese (Mn) 0.75%~1.00%, phosphorus (P) ≤ 0.040%, sulfur (S) ≤ 0.040%, chromium (Cr) 0.80%~1.10%, molybdenum (Mo) 0.15%~0.25%. ‌
Nickel (Ni) and copper (Cu), as residual elements, typically have a content of ≤ 0.030%. ‌
These elements work together, with carbon and manganese improving strength and hardenability, while chromium and molybdenum enhancing corrosion resistance, high-temperature strength, and tempering stability. ‌
Mechanical performance
After quenching and tempering heat treatment (oil cooling after quenching at 850 ℃, water cooling or oil cooling after tempering at 560 ℃), the mechanical properties of 4140 seamless tube include: tensile strength σ b ≥ 1080 MPa (about 110 ksi), yield strength σ s ≥ 930 MPa (about 95 ksi), elongation δ 5 ≥ 12%, cross-sectional shrinkage rate ψ ≥ 45%, impact energy Akv ≥ 63 J, impact toughness α kv ≥ 78 J/cm ² (about 8 J/cm ²), and hardness ≤ 217 HB
Different heat treatment states (such as normalizing, annealing) or delivery states may cause performance fluctuations, such as yield strength at 80 ksi (approximately 552 MPa), which is also common in specific applications