Application of Thermo Mechanical Controlled Process on HSLA Steels for Line Pipe

摘要

Line pipe steels, which transport oil and gas, should have high strength, good low temperature toughness, excellent corrosion resistance and superior weldability. Combined effect of micro alloying elements in steel and thermo-mechanical controlled processing during hot rolling provides excellent properties which are required for higher grades line pipes. Thermo Mechanical Controlled Processing (TMCP) is a technique comprising of both controlled rolling and accelerated cooling which produces favoured microstructures. A low carbon micro alloyed steel when treated through thermo-mechanically controlled process from no recrystallized austenite, produces bainitic ferrite fine grained microstructure offering excellent properties for line pipes. Also, a low carbon chemistry and Nb/V/Ti micro alloyed combined with boron addition shows sufficient HAZ cold cracking resistance and limit softening in the seam weld HAZ.