微观组织对管线钢落锤性能的影响研究

为了提高输送管道安全性，保证管体开裂后材料具有一定的止裂能力，采用大能量摆锤冲击试验机研究了壁厚对X80管线钢 DWTT 剪切面积和能量密度的影响，并利用金相显微镜和透射电镜分析了带状组织、位错、组织均匀性等对 DWTT 性能的影响。结果显示，随着钢板厚度的增加，管线钢的韧脆转变温度升高，韧脆转变区的能量密度降低；高硬度粗大的M/A组织带会严重恶化DWTT 性能；而细小均匀的贝氏体组织使管线钢具有较高的 DWTT 性能。研究表明，优化连铸工艺减轻中心偏析，优化控轧控冷工艺以及消除钢板心部带状组织，提高钢板壁厚方向组织均匀性对改善厚壁管线钢低温落锤性能有显著作用。

The Influence of Microstructure on DWTT Performance for Pipeline Steel

In order to improve the safety of the pipeline and ensure that the material has a certain crack arresting ability after the cracking of the pipe body， the thickness effects of X80 pipeline steel in DWTT sheared area and energy density was investigated using large energy pendulum impact testing machine. And the effect of banded structure， dislocation，microstructure homogeneity on DWTT property was analyzed by means of metallographic microstructure analysis and transmission electron microscopic microstructure analysis. The results showed that with the increase of the thickness of the steel plate， the ductile-brittle transition temperature of pipeline steel increased， and the energy density of the ductile brittle transition zone reduced. Serious M/A hard belt would deteriorate the DWTT performance. The high hardness of the M/A belt will seriously deteriorate the DWTT performance； while the fine and uniform bainite structure will make the pipeline steel have higher DWTT performance. By optimizing the process of continuous casting to reduce the center segregation of the steel plate， optimizing the process of controlled rolling and cooling to eliminate the band structure of the steel core， and improving the uniformity of the microstructure in thickness direction of the steel plate has a significant effect on improving the low temperature drop hammer performance of the thick wall pipeline steel.