对焊成形大口径弯管技术研究

针对大口径弯管在弯制过程中容易导致外管壁出现裂纹,内管壁起皱,横截面畸变等问题。在预弯热处理后应用对焊技术来实现大口径弯管成形,即首先根据使用要求进行板材弯曲成形,在热处理去除内部应力后,选择合适的焊接工艺及焊接参数进行对焊成形。进一步对大口径弯管的焊接接头性能进行拉伸试验、断口扫描试验、裂纹尖端张开位移试验研究。结果表明:焊接接头的断口位置大多位于母材区,且抗拉强度值均符合标准;母材的断口处形貌主要是由少量的小而浅韧窝集聚而成,断裂时冲击吸收功低于焊缝;在零下20℃焊缝处的CTOD均值为1.39,母材断口处的CTOD均值为0.82。

Study on big diamter bent pipes formed by welding technique

For the cracks appearing on outer pipe wall, wrinkling on inner pipe wall, distortions on cross-section and so on in the bending process of big diameter bent pipe, the welding process wilt be carried on by means of pre-bending heat treatment to relieve the internal stress, adopting manual electrode welding as base welding and submerged arc welding as full welding to form the joint. Furthermore, the joint of pipe had been tested by tension, fracture scanning and crack-tip Opening displacement. The test results show that the broken position of welding joint mainly located in the area of base metal and the tensile strength values met the standards. The fracture appearance of base metal is mainly formed by the gathering of tiny and flat dimples. Its impact toughness is lower than the welding lines while cracking. The average CTOD value of welding line at - 20~ is 1.39, while the average CTOD value of base metal is 0. 82.