42crmo Seamless Steel Pipe

The chemical composition of 42CrMo seamless steel pipe conforms to GB/T 3077-2015 "Alloy Structural Steel" standard (GB/T 8162 for seamless steel pipes for structural use also refers to this composition requirement). The following are the legally permissible content ranges (mass fraction, %) for smelting analysis:

Core properties are as follows

1. Excellent mechanical properties in quenched and tempered state: After quenching and high-temperature tempering heat treatment, the tensile strength of the conventional cross-section pipe is ≥1080MPa, yield strength is ≥930MPa, elongation after fracture is ≥12%, and room temperature impact energy is ≥63J. Its strength and load-bearing capacity are more than 1.8 times that of 45# seamless pipe, far exceeding that of 40Cr alloy steel pipe, while maintaining good plasticity and toughness, achieving a balanced match between high strength and impact resistance.

2. Strong adaptability to heat treatment and outstanding hardenability: Chromium and molybdenum synergistically enhance hardenability, allowing for oil quenching to penetrate large wall thickness sections without significant temper brittleness. It supports various heat treatment processes such as tempering, high-frequency surface hardening, and gas nitriding. After high-frequency quenching, the surface hardness can reach HRC55~60, and after nitriding, the surface hardness is even higher, achieving a gradient performance of "high wear resistance on the surface and high toughness in the core."

3. Stable high-temperature creep and fatigue resistance: Molybdenum effectively inhibits high-temperature grain boundary slip, maintaining stable strength and creep resistance below 500℃ without the risk of a sudden drop in strength at high temperatures. The grains are refined and uniform, resulting in excellent fatigue strength under alternating loads, outstanding impact resistance and overload resistance, making it suitable for heavy-load conditions with long-term high-frequency stress.

4. Controllable Machining Performance: The pipes delivered in the annealed/normalized state have excellent machinability. After tempering, the hardness is stable in the range of HB280~320, making them less prone to sticking and chipping, and resulting in high machining accuracy. Welding requires preheating to 250~350℃ and slow cooling after welding to achieve reliable weld strength.