N80级石油套管在线形变热处理工艺

On-line Thermomechanical Treatment Process for N-80 Grade Oil Casing

利用连轧管后的中间冷却、再加热及定减径过程,实现钢管生产的在线形变热处理,这种工艺既能提高钢管的性能,又能降低生产成本.结果表明:40Mn2V钢经在线形变热处理后,奥氏体晶粒度较直接定径工艺提高2.5～3级,生产无缝钢管的纵向冲击功Ak≥22J,σ0.5≥555MPa,σb≥819MPa,延伸率δ5≥23％,满足API标准对N80石油套管的性能要求.中间冷却过程中,奥氏体的完全分解程度以及合理的再加热温度是改善N80石油套管力学性能的关键.

The study focuses on fulfilling the on-line thermomechanical treatment(OLTM) process by intermediate cooling, reheating and reduction rolling of rough tubes after mandrel rolling. The process is beneficial to high qualities and lower costing for seamless tubes. It is found that the austentic grain grade by OLTM is smaller 2.5-3 ASTM than that by direct sizing, the properties of 40Mn2V steel by OLTM are the longitudinal toughness Ak≥23J,σ0.5≥555Mpa, σb≥820Mpa, elongation δ5≥23%, matching the property demands ofAPI Standard about N80 grade oil casing. The vital factors of improving impact toughness are the degree of austenite decomposition during intermediate cooling and the proper reheating temperature.