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通过高温拉伸试验研究了厚规格X80管线钢的高温力学性能,分析了不同温度的高温拉伸试样的组织,确定了卷取“热头”温度控制范围。结果表明:X80管线钢的高温屈服强度受温度影响明显,当温度由550℃升高到700℃时,屈服强度由488 MPa降低到240 MPa;组织由原始轧态的针状铁素体变为粒状贝氏体,同时析出相长大,位错密度降低。对于厚规格高级别管线钢而言,卷取时“热头”温度应控制在600~650℃。
The high temperature mechanical properties of X80 pipeline steel with thick gauge were studied by high temperature tensile test. The microstructure of high temperature tensile specimens with different temperature was analyzed, and the temperature control range of “hot head” was determined. The results show that the high temperature yield strength of X80 pipeline steel is significantly affected by temperature. When the temperature rises from 550 ℃ to 700 ℃, the yield strength decreases from 488 MPa to 240 MPa. The microstructure changes from as-rolled acicular ferrite to Granular bainite, at the same time, the precipitates grow up and the dislocation density decreases. For thick high-grade pipeline steel, coiling “hot head ” temperature should be controlled at 600 ~ 650 ℃.