加热温度及时间对Q690qD奥氏体晶粒尺寸的影响

Effect of Heating Temperature and Time on Grain Size of Q690qD Austenite

利用热模拟试验机及金相显微镜等仪器和方法,研究加热温度及时间对Q690qD原始奥氏体晶粒尺寸的影响。分析结果表明:当加热保温时间均为300 s时,Q690qD奥氏体晶粒尺寸随加热温度上升逐渐长大,并在加热温度达到1250℃时,原始奥氏体开始出现较粗大的混晶组织;当增加保温时间至10min及20 min后,Q690qD奥氏体晶粒尺寸随保温时间延长逐渐长大,并在加热温度达到1150℃、保温时间为20 min时原始奥氏体晶粒就开始明显粗化;经测算Q690qD钢中的Nb在1158℃左右时可全部固溶。结合试验得出工业化生产中铸坯加热温度不宜超过1200℃。

The effects of heating temperature and time on the original austenite grain size of Q690qD were studied by using thermal simulation testing machine, metallographic microscope and other instruments and methods. The results show that: when the heat preservation time were 300 s, Q690qD austenitic grain size increased with heating temperature, and when heating temperature reached 1250 ℃, the original austenite showed relatively coarse mixed grain structure;when the holding time was increased to 10 min and 20 min, the austenite grain size of Q690qD gradually grew with the extension of holding time, and the original austenite grain got coarse obviously when the heating temperature reached 1150 ℃ and the holding time was 20 min;It is estimated that the Nb in Q690QD steel can be completely dissolved at about 1158 ℃, combined with the test, it is concluded that the slab heating temperature should not exceed 1200 ℃.