【摘要】 研究了临界淬火热处理(QLT)工艺对LNG工程用9Ni低温钢力学性能及精细组织的影响。与常规调质(QT)工艺的对比研究显示,QLT工艺在略微降低强度水平的情况下,显著提高9Ni钢的低温韧性水平及工艺稳定性,屈强比降低。随着两相区淬火温度的提高,9Ni钢的抗拉强度基本不变,屈服强度逐渐升高,低温冲击功在640~680℃范围达到最高值,为200 J以上。QLT工艺处理9Ni钢良好的低温韧性水平与层片化的细化马氏体组织及一定数量的稳定逆转变奥氏体直接相关。实验钢在640~680℃的两相区淬火,可获得10%以上含量的逆转变奥氏体,有利于低温韧性的改善。更多还原

【Abstract】 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.更多还原