高钛微合金热轧板低温冲击功不合格的原因分析

Cause analysis on low temperature impact energy disqualification of high titanium micro-alloyed hot-rolled plate

试验针对高钛(wTi>0.05%)热轧平板微合金钢开发过程中,出现的低温冲击韧性差的现象进行了系统分析,包括冲击断口形貌、断口附近组织及钛的固溶、析出量等,初步判断冲击韧性差主要与组织脆性有关。在此基础上,将冲击功不合格试样利用热模拟试验机,模拟900~1 200℃不同加热温度下,轧制过程中的温度变化。结果表明:加热温度不大于1 050℃时,试样的―20℃冲击功由原来的不足10 J提高到240 J左右;然而,当加热温度超过1 100℃时,试样的冲击功仍然与原始热轧态一样。结合对钛析出量、析出相的尺寸分布以及组织、晶粒度等的对比分析发现:钛的固溶量、钛析出相的尺寸以及晶粒度大小是影响高钛热轧板低温冲击功的主要原因。

This paper systematically analyzed low temperature impact poor toughness,which occurred in the development process of high Ti(wTi>0.05%)micro-alloyed hot rolled plate,including the impact fracture morphology,microstructure around the fracture,solid solution and precipitation percentage of Ti. It was deduced that poor impact toughness was mainly attributed to the brittleness of the microstructure. Based on this,thermal simulation test was performed with the samples of poor impact energy according to the temperature change during the rolling process with different reheating temperature from 900 ℃ to 1 200 ℃. The results showed that at ―20 ℃ impact energy increased from less than 10 J to more than 240 J if the re-heating temperature is equal to or lower than 1 050 ℃. However,when the temperature exceeded 1 100 ℃,the impact energy stayed as low as the original hot-rolled state. Based on the analysis including the amount of precipitated titanium,size and distribution of the precipitates,microstructure and grain size,and it can be concluded that the main factors affecting the low temperature impact energy was composted with the amount of Ti solid solution,size of Ti precipitates and the grain size.