热成形温度对高强钢方管组织及性能的影响

为了克服传统辊弯工艺和设备对室温下高强钢的影响，提出弯角局部感应加热辊压成形工艺制备高强钢方管，并通过单向拉伸试验、断口形貌观察、微观组织扫描电镜观察和X射线衍射分析研究热辊压成形温度对高强钢方管弯角处组织及力学性能的影响。结果表明，随着温度的升高，弯角力学性能得到明显的改善，断口形貌由室温下解理断裂逐渐过渡为韧性断裂，弯角处微观组织由板条状贝氏体向粒状贝氏体发展且多边形铁素体晶粒开始长大，方管外表面周向和纵向残余应力都明显降低且分布更加合理。综合实验分析，高强钢方管热辊压成形工艺的最佳温度为650益。

Effect of hot forming temperature on the microstructure and mechanical properties of high strength square tubes

To overcome the challenge of traditional roll forming process and equipment on high strength square tubes at room temperature, hot roll forming process using local induction heating was proposed to produce high strength square tubes. A series of tests including tensile testing, fracture morphology, scanning electron microscopy ( SEM) and X-ray diffraction were performed to investigate the effect of hot forming temperature on the microstructure and mechanical properties of high strength square tubes. Experi-mental results show that as the temperature rises, the mechanical properties of the corners improve significantly. The fracture morphol-ogy gradually changes from cleavage fracture at room temperature to ductile fracture. The microstructures at the corners are developed from lath bainite to granular bainite and the polygonal ferrite begins to grow. Moreover, the circumferential and longitudinal residual stresses on the outside surface of the square tubes are reduced and reasonably redistributed. Based on the analyses of experimental results, the optimum forming temperature for high strength square tubes is 650℃.