Non-preheat welding technology of 690MPa high strength steel for coal mine machinery
Q690 is a kind of high-performance steel to meet the development of high-strength and large-scale coal mine machinery.In order to prevent the welding cold crack,increase the efficiency and lower the cost,Baosteel developed Q690HP designing with ultra-low carbon and low carbon equivalent.Q690HP is expected to perform welding without preheating.In this paper,the cold crack sensitivity and feasibility of non-preheated welding process under specific temperature environment were evaluated through Y-groove cracking test firstly.The mechanical properties were systematically tested for non-preheated welding joints.Simultaneously,the welding parameters matching the non-preheated welding technology of Q690HP were obtained.The result shows that there is no crack on the weld metal of the Y-groove cracking test sample without preheating and at the ambient temperatures of 5 ℃,indicating the excellent crack resistance sensitivity.There are two non-preheated welded joints obtained the good combined mechanical properties under the lower welding heat input of 7-12 kJ/cm,lower interpass temperature of 100-150 ℃,the properties of the welded joint meet the standard requirements.
steel for coal mine machineryQ690HPcold cracknon-preheated welding technology
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