Horizontal Narrow Gap MAG Welding Of 10CRNI5MOV Steel With 40MM Thickness

Heavy plate welding is widely used in the process of Submarine Pressure Hull welding. However horizontal narrow gap GMAW can satisfy the requirement of heat input and productivity of the heavy plate welding work station. During the process of horizontal welding, the melting metal is caused to flow down by the gravity. When it is serious, hemline infusion and other flaws will appear. At the same time, mismatch welding parameters will cause a series of flaws. Rotation arc welding can eliminate upon flaws, so it is widely used in large and thick plate and narrow-gap horizontal welding. This thesis makes an improvement of rotation electrical arc welding torch, which researches rotation electrical arc narrow-gap horizontal welding on large and thick plate Q235 and 10Ni5CrMoV steel to eliminate all kinds of flaws of narrow-gap horizontal welding and get a perfect welded joint.It is used high-speed camera and current and voltage acquisition system to make a research of rotation electrical arc droplet transfer in narrow gap and droplet forming mechanism. The result shows that because of the specific weld pool behaviors and arc motion in rotation electrical arc narrow-gap welding trajectory, it is caused periodic change of welding current and formed the periodic change of droplet transfer and the force to molten pool. Just this periodic change conquers the flow down of melting metal, incomplete fusion and undercut and so on in horizontal welding.After the best scope of welding process parameters is defined, it gets a welded joint that is in good shape and no flaws inside. It is researched the influence rules of all kinds of welding parameters to weld pool behaviors in rotation electrical arc narrow-gap horizontal welding and welding flaws when it is the mismatched welding parameters.It makes a research of the scope of the best process parameters of 40mm narrow-gap 10Ni5CrMoV steel multilayer and single channel welding and the organization structure and capability of its welded joint. The joint can be divided into three zones: base material zone, heat affected zone and welding zone. HAZ could be divided into three parts: coarse-grained HAZ,fine-grained HAZ,incomplete normalized zone and tempering zone.The capability can satisfy the requirements of the scene. The mechanical properties of the rotating arc horizontal narrow gap welds are studied. The TSE of both integral and local joints is equal to 100%. All the joints are fractured in the BM. It indicates that the tensile properties of WZ and HAZ are larger than that of BM. This can be improved by the result of the Vickers hardness distribution of the joints. The impact toughness in WZ, HAZ and BM at -50℃is equal to 75J, 201J and 220J respectively. At the same time it prospects the actual application of the heavy steel rotation electrical arc narrow-gap MAG welding and comes up with the corresponding improvement methods.