中文摘要：

研究了X70级管线钢在不同加热温度和不同保温时间下的奥氏体晶粒长大规律。结果表明，当奥氏体化温度低于950℃时，试验钢有较小的晶粒尺寸；奥氏体化温度超过1100℃，晶粒平均截距开始明显增大，一旦奥氏体化温度上升到1300℃时，奥氏体晶粒已显著粗化。分析表明，试验钢奥氏体晶粒平均截距历和奥氏体化温度T成指数关系。当奥氏体化温度为950℃和1100℃时，奥氏体晶粒平均截距瓦和保温时间t均成正比关系。研究结果对于X70级管线钢弯管和三通等管件制造的热加工过程有着重要参考价值。

英文摘要：

The grain growth behavior of a X70 grade pipeline steel in fitting-manufacture thermal process was studied. The results show that when heating temperature is lower than 950℃, the experimental steel has a smaller grain dimension;when heating temperature is above 1100℃ ,the anstenite grains grow rapidly. When heating within the range from 900-1300℃, the relationship between the average anstenitc grain size and heating temperature is exponential function;and when the experimental steel is heated at 950℃ and 1100℃ ,the relationship between the average austenite grain size and heating time is direct proportion. The results are important for the fitting-manufacture process of X70 grade pipeline steel at high temperature.