插销法研究自保护焊U75V钢轨的冷裂敏感性

采用插销试验法研究了JDHS-38#自保护药芯焊丝焊接U75V钢轨的冷裂敏感性,评估了预热温度、线能量、焊道数3个因素对U75V钢轨临界断裂应力的影响.结果表明,现场对钢轨施焊时,采取250℃的预热温度,14 kJ/cm左右的线能量,双层焊等措施可以使钢轨接头热影响区少产生甚至不产生焊接冷裂纹,使其临界断裂应力达646 MPa,与抗拉强度相当.若采用其他工艺参数,临界断裂应力较低,且当拘束拉伸应力高于抗拉强度时,于热影响区发生氢致断裂.焊接接头过热区组织主要为马氏体、贝氏体,断口显微形貌主要为河流花样、泥状花样及爪状花样.

Study of cold cracking sensibility of self-shielded flux cored arc welded U75V rail using implant test

lmplant tests were carried out to study the cold cracking sensibility of U75V steel welded by JDHS-38_#self-shielded flux cored wire. The influence of preheat temperature,heat input and number of weld passeson the critical press of U75V rail was studied. Results indicate that different methods should be taken to protectthe HAZ from the influence of welding cold cracking,such as preheating the rail t0 250 0C ,keeping heat inputaround 14 kj/cm, using multi-layer welding method. Therefore, the critical fracture stress could reach646 MPa,which is equivalent to its tensile stress. If adopting other processing parameters,the critical fracturestresses are much lower,and when the restraint stress is higher than tensile strength,the expiration break wouldhappen in HAZ. The breaking nature is typical hydrogen-induced crack. The microstructures of superheat sec-tion are martensite and bainite,while the fracture appearances are mainly river pattern,pulpy pattern and ungu-lar pattern