Study On Equipment And Process Of Hybrid Heat Source Friction Stir Welding For Armored Steel

As a solid phase welding method, FSW has many advantages over traditional melting welding. In the welding applications of the low melting point alloy such as aluminum alloy, it has been widely promoted. But for the friction stir welding of high melting point, high strength alloy, it is still in the research stage. In this dissertation, according to the material properties of armored steel, the mixing tool and hybrid welding system has been designed, and the preheating temperature field of hybrid heat source friction stir welding and the welding process were studied.616 armor steel belongs to ultra-strength steel, the tensile strength is greater than 1300MPa, the microstructure is ferrite and pearlite. Since welding crack is easy to appear, Filler wire welding and shielded metal arc welding of austenitic stainless steel are usually used. In general, it’s a kind of dissimilar material welding. There are high residual stresses after welding, and stress corrosion cracks and fatigue cracks can be generated easily. Using the 616 armor steel as the research object, through simulation and experiments, the hybrid heat source friction stir welding of 616 armor steel has been realized through simulation and experiment.In this dissertation, based on SYSWELD welding simulation software, the preheating temperature field distribution is simulated and the effects of the preheating parameters for the temperature distribution of the preheating temperature field is studied. the changing rule of the characteristic parameters of the peak temperature, the second peak temperature, temperature change inflection point has also been studied. The process window of the hybrid heat source friction stirring welding is initially identified.In this dissertation, based on arc, back heating pad hybrid friction stir welding system welding process, the stirring head is made by sintering silicon nitride powder. Suitable welding parameters are:the preheating arc current of 30-40A, mixing head speed 1000-1200r/min, the welding speed is 30-45mm/min. Within this range, the molding has good surface and internal welds, the holes, burrs, surface oxidation and other defects are effectively avoided. And weld heat affected zone of welded joints and the nugget zone are ferrite and pearlite-based, there is a certain amount of martensite, homogenizing weld microstructure, the grain size of each region is much smaller than that under melting weld conditions.The tensile strength of welding joints reaches 815MPa, which is roughly equivalent to that under the use of traditional austenitic stainless steel MIG. The tensile fracture is mainly composed of dimple accumulation area. The microhardness value of base metal and weld nugget zone is similar, the maximum hardness value is up to 400HV. The properties of welding joints have reached a higher level, and basically there is no deformation after welding...