中文摘要：

在热模拟试验机上采用变截面试样进行高温拉伸试验，评价了304奥氏体不锈钢铸坯的裂纹敏感性。结果表明：该不锈钢产生裂纹最敏感的温度区间为1000-1150℃，这与采用常规的应变-断裂（STF）方法测定的焊缝裂纹最敏感的温度区间相同，只是测定的产生裂纹的临界应变量较小。同时，利用这种方法测量产生裂纹的临界应力，当变形温度低于1000℃左右时临界应力随温度的下降而快速上升，在较高温度区间其随温度的升高而缓慢下降。分析认为，在奥氏体不锈钢铸坯的热变形过程中，流变应力是产生裂纹的重要因素，当流变应力超过临界应力时，将出现裂纹。

英文摘要：

The susceptibility of ductility-dip cracking （DDC） in as-cast 304 austenitic stainless steel was studied by hot deformation test. The results show that the most sensitive temperature range is the same with that of welded joint obtained by previous STF, which is between 1000℃ and 1150℃. But the threshold strain of the test is smaller than that obtained from the welded joint. Meanwhile, the threshold stress can be calculated. While below 1000 ℃ or so, the stress increases rapidly with the decrease of temperature, but it slows down above 1000 ℃ with the increase of temperature. The analysis suggests that the flow stress is the key factor to cause the cracking during hot deformation processing. If the flow stress is bigger than threshold stress, the cracks occur.