Effect of inter-critical quenching process on mechanical property and microstructure of 9Ni cryogenic steel
Effect of inter-critical quenching process (QLT) on mechanical properties and microstructure of 9Ni cryogenic steel was investigated.The results show that compared with conventional quench-temper (QT) process,QLT process can markedly increase cryogenic toughness level and improve process stability as well as reduce yield ratio at the expense of slight strength reduction.With increasing inter-critical quench temperatures,yield strength can increase gradually with ultimate tensile strength basically unchanged,and cryogenic impact energy of the steel quenched at 640-680 ℃ can reach peak value as high as above 200 J.Excellent toughness level of QLT-treated 9Ni steel is directly connected to lamellarized and refined martensitic microstructure and reversed austenite with certain volume fraction.The steel treated by QLT at 640-680 ℃ contains thermally stable reversed austenite of above 10％,contributing to cryogenic toughness improvement.
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万方数据
维普
