加热温度对X70大变形管线钢热煨弯管组织的影响

Effects of Heatig Temperature on Microstructure of Induction Bends Form X70 Pipeline Steel with Excellent Deformation

采用热模拟方法,对两种不同的X70大变形管线钢进行热煨弯管工艺过程模拟,研究了不同加热温度对其组织的影响规律。结果表明,当加热温度为750～850℃时,组织发生不完全相变,硬度下降;当加热温度为1000～1050℃时,组织为粒状贝氏体和板条状贝氏体铁素体。两种钢的化学成分、轧制工艺和原始组织不同,导致加热后显微组织、晶粒尺寸和硬度的变化趋势不同,二次热加工性存在差异。合理选择母管并将加热温度控制在1000～1050℃时,采用X70大变形管线钢制作热煨弯管可获得具有良好强韧性的显微组织,但其塑形和抗大应变性能难以达到原始母材的水平。

The influence of heating temperature on the microstructure of X70 pipeline steel was studied by simulating heat bending using thermal modeling method. The results indicate that the microstructure shows incomplete phase change and the hardness reduces, when the heating temperature is 750℃～850℃; the micr0structure shows granular bainite and lath bainite ferrite at 1000℃～ 1050℃. The differences of the two models of steel in chemical composition, rolling technology and original microstructure produce different changes in the mierostructure, grain size and rigidity after heating, which indicates that they are different in secondary heat processability. Under proper initial pipe and heating temperature of 1000 ℃～1050℃, the induction bent pipe with robust microstructure can be obtained from X70 pipeline steel with excellent deformation. However, the plasticity and large deformation resistance of the bent pipe is not equivalent to the initial pipe.