DWTT in Thicker Gauge Hot Rolled Coils for Line Pipe Application
Ductile failure in DWTT(Drop Weight Tear Test)at subzero temperatures is one of the key requirements for line pipe steels.As the temperature drops or thickness increases,the ductile failure mode is difficult to achieve in DWTT testing.JSW Steel has successfully developed new generation Nb-microalloyed line pipe steels for heavy gauges(up to 20mm)for grades up to API X-80 grade for the first time in India through hot strip mill.It has been observed that prior austenite grain boundaries act as major crack arresters due to the high angle of misorientation at the grain boundaries.In order to achieve ductile DWTT failure,the crack propagation by brittle Griffith cracks needs to be arrested by high angle boundaries with their interspacing lesser than that of the critical Griffith crack length.Hence refinement of prior austenite grain size which requires optimization of multiple dynamic and static recrystallisation phenomena coupled with reduced grain growth at rolling temperatures,leads to improved DWTT performance.This paper describes the various aspects of steel chemistry design and the hot rolling process optimization to achieve subzero temperature DWTT in thicker gauge line pipe steels.Multiple online trials have been conducted at JSW Steel,Vijayanagar works for achieving the same,such that the effects of chemistry and process variables on final microstructures and mechanical properties have been established.Further,a correlation table has been prepared for predicting DWTT transition temperature based on the largest prior austenite grain size in the transfer bar microstructure before entering into the finishing mill.This table has proven to be very useful in alloy design and in optimizing hot rolling process window to achieve superior DWTT performance for different end thicknesses in line pipe steels.
DWTT (drop weight tear test) dynamic recrystallisation static recrystallisation prior austenite grain size
Pradeep Agarwal Gunna Venkata Ramana Devasish Mishra Ashish Chandra Gajraj Singh Rathore
JSW Steel Ltd.,Vijayanagar Works. Toranagallu,Karnataka,India
国内会议
上海
英文
1-7
2015-10-21（万方平台首次上网日期，不代表论文的发表时间）