Influence of Microstructure on DWTT Performance of Thin-wall X65M Pipeline Steel

Abstract

 The paper addresses the issue of fluctuating low-temperature drop-weight tear test （DWTT） performance in 6-8 mm thin-wall pipeline steel， the influencing factors of the control process of low-temperature DWTT of X65 thin-wall pipeline steel have been explored. With microstructure analysis and numerical deconstruction study of different low-temperature DWTT results， ， it reveal that the size of polygonal ferrite grains and the distribution of M/A constituents in the central part of the steel plate significantly affect low-temperature DWTT performance. When the average area of grains with an area ≥200 μm2 is greater than 260 μm2， and the proportion of M/A constituents is greater than 6%， DWTT performance shall deteriorate significantly. By optimizing the composition and continuous casting and rolling processes， control of grain size and M/A constituents can effectively improve the low-temperature DWTT performance of thin-specification pipeline steel. The related product has achieved stable production of more than 80，000 tons， meeting the requirement of -30 ℃ low-temperature DWTT， it is of great significance for the development and production of thin-wall pipeline steel products.

Keywords

• thin-wall pipe line steel； dwtt； grain size； m/a microstructure； x65m