调质无缝钢管的热扩工艺探讨

Discussion on Hot Expanding Process for Quenched and Tempered Seamless Steel Pipe

选取具有抗低温(-100 ℃)冲击性能的含Ni低碳钢,分析该钢种热轧成钢管后直接热扩、热轧后调质、热轧后调质再热扩、热轧后热扩再调质4种处理方式的无缝钢管的力学性能变化规律及其金相组织。分析认为:相比其他几种工艺,热轧后直接热扩的产品拉伸性能偏低,-100 ℃冲击功几乎为0;对于变径量大的热扩管,虽然热扩原料管调质后的性能好,但热扩后无缝钢管机械性能下降幅度大,特别是低温冲击性能;低碳锰钢及微合金钢原料管调质后,在变径量不大时,可直接热扩成大直径薄壁无缝钢管。

A low carbon steel (with Ni addition) with low temperature (-100℃) impact resistance is selected to analyze how 4 kinds of treament processes affect the mechanical properties and metallographic structure of the seamless steel pipe made by it, i.e. hot rolling + hot expanding, hot rolling + quenching & tempering, hot rolling + quenching & tempering + hot expanding, and hot rolling + hot expanding + quenching & tempering. The analysis leads to the following conclusions. Comparing to other processes, the hot-rolled and hot-expanded product has lower tensile strength and its -100℃ impact energy is almost 0. For hot-expanded pipe with a big diameter change, although the mother pipe before expanding has good properties after quenching & tempering, the properties of the expanded seamless steel pipe are decreased, especially its low temperature impact toughness. And when diameter change is not big, the low carbon manganese steel/low alloy steel mother pipes, after quenching & tempering, can be directly hot-expanded to big diameter thin wall seamless steel pipes.