Study On Microstructures And Mechanical Properties Of BS600MCJ4 Low Alloy And High Strength Steel Welding Joint

With the rapid development of the modern industry,mechanical equipment update increasingly.As the modern industrial production of essential transport machinery,crane has become more and more large-scale,high parameter and lightweight.In recent years,domestic and foreign research units and factory pay attention to use modern mechanical design theory and advanced production technology means.The arm?turntable?leg and other important structure of crane were made of low content and high strength steel.So the weight of crane is decreasing and its lifting performance is enhancing.The crane is more effective and reliable.In this paper,the weldability,mechanical properties,microstructure and structural characteristics of BS600MCJ4 low alloy high strength steel are studied.In order to determine the influence of different t_8/5time on the structure and mechanical properties of welded joints,we have carried out the tests of crack resistance,tensile,impact,bending and other mechanical properties of welded joints,the physical and chemical tests of metallographic structure analysis,and the welding thermal simulation tests of welded joints.Based on the above test results,we can conclude that ER70-G solid core welding wire is suitable to be used as the welding material of BS600MCJ4 low alloy high strength steel,and the structure,physical and chemical mechanical properties of the welding joint meet the requirements of production and construction.The microstructure of the weld metal of BS600MCJ4 low alloy high strength steel was analyzed.The microstructure of the weld metal was stable and the grain size was suitable.Through the Vickers hardness test of the welded joint,the hardness values of each area of the weld metal meet the requirements of relevant standards,and there is no softening phenomenon in the heat affected zone of the welding.Through the welding thermal simulation test,the results show that t_8/5has little effect on the microstructure and physical-chemical mechanical properties of the HAZ.During the welding of BS600MCJ4 low alloy high strength steel,the key to ensure the welding quality is to avoid the generation of cold cracks.Therefore,proper preheating temperature before welding,strict control of interlayer temperature and better welding heat input during welding are all important means to avoid the generation of cold cracks.After welding,it shall be cooled slowly to ensure that the welded joint has good toughness and strength.