X65Q管线钢管强度超标的热处理改善措施研究

Study on Countermeasures to Improve Heat Treatment Process as Causing Standard-exceeding Strength of X65Q Steel Linepipe

介绍管线钢HOP在线热配分处理技术,通过该技术可获得贝氏体+马氏体/奥氏体复相组织。某公司采用HOP技术生产X65Q管线钢管,但淬火+回火态交货产品的强度超出API标准要求。分析造成X65Q管线钢管强度超标的原因,对管体进行系列回火热处理工艺研究,并分析回火温度对其组织性能的影响。分析认为:X65Q管线钢管强度超标疑是回火温度偏低或保温时间不足所致;采用650～680℃回火后保温60 min、400℃后出炉空冷的工艺,可使X65管线钢管的强度满足API标准要求,有效改善强度超标缺欠。

Described in the article is the heat on-line partitioning technology (HOP technology)for the linepipe steel which makes it possible to get the bainite+martensite/austenite complex structure.Though the X65Q steel linepipe is produced by a certain domestic company with the HOP technology,but under the as-tempered &quenched furnishing condition its strength exceeds the specific API vaIue.The reason for the excessive strength is investigated,serial studies on the heat treatment processes as applied to the pipe body are conducted,and the effect by the tempering temperature on the pipe body microstructure property is analyzed.The analysis result reveals that the excessive strength of the X65Q steel linepipe is caused by the rather low tempering temperature or the insufficient soaking time.Therefore it is possible to get the X65 steel lincpipe having the strength up to relevant API requirement by means of adopting the process that involves 650-680℃ tempering temperature,60min.soaking time,and air-cooling of the pipe after running out of the furnace at 400℃.As a result,the problem of defective excessive strength is fixed.