Study On Plasma Arc Welding Process Of Pure Nickel Thin Plate

According to the major scientific and technological projects in 2010 of Jinchuan,nickel-based alloy plate welding is a technology problem,the subject studying pure nickel thin plate plasma arc welding process.Plasma arc welding is the most widely used in high energy beam welding technology,it has a high arc temperature,high energy density and flame speed,current strong penetrating ability,fast welding speed,small heat affected zone,the deformation of the workpiece is small,small current welding arc stability,high welding quality,easy operation and so on.Straight polarity direct current plasma arc welding can be used for welding pure nickel,stainless steel,heat-resistant alloy steel,Monel alloy,titanium alloy,gold,copper and other materials.Alternating current plasma arc welding mainly used for welding aluminium and its alloys,magnesium and its alloys,beryllium bronze,aluminum bronze.This subject adopts DC Positive penetrating plasma arc welding technology,welding pure nickel thin plate,and carrying plasma arc welding process research for the pure nickel plate.Based on the pure nickel N6 welding and the actual production situation of the Jinchuan company workshop,made the research scheme.By adjusting the main welding parameters,the welding current,welding speed,plasma gas flow to obtain the welding parameters to made the weld formation good.To further improve the microstructure and properties of welded joints,forming good welded joints were cold rolling and hot rolling test.Testing the test specimen using X-ray inspection and coloring method.Optical microscopy and scanning electron microscopy to study the organization of the welded joints.Through micro-hardness,tensile,bending,impact and other mechanical properties,to the mechanical properties of the base metal,welded,after welding,cold rolling and hot rolling specimens testing.By scanning electron microscopy observation and analysis the impact fracture.Through the research of welding process parameters,obtained a set of welding parameters to made the weld forming good:the welding speed is 120mm/min,the welding current is 140A～145A,the plasma gas flow rate of 2.8L/min,the protective gas flow rate is 25L/min,the arc voltage is 23V.After welding on forming good welded joints were cold rolling and hot rolling,the joint surface smooth and appearance beautiful.Testing of welded specimens by X ray inspection and coloring method,specimen no crack,fusion and incomplete welding defects,meet the relevant requirements and sample qualified.Optical and scanning electron microscope analysis the micro structure of the welded joints,welding,after welding cold rolling and hot rolling specimen welding joint has no obvious change on microstructure,the fusion zone is narrow,the weld microstructure was growth along the molten pool wall coarse columnar and part of equiaxed crystal,heat affected zone grain grow significantly.Through the specimen hardness test,untreated welded joints hardness value is slightly lower than base metal,after post weld heat rolling and cold rolling welding joint microhardness increased.From the tensile test results know that welding,after cold rolling and hot rolling welding joint tensile strength values are up to the parent metal more than 80%,to meet the technique requirements of the Jinchuan companies proposed.Bending tests were performed on specimens,the results showed that there were no obvious defects,face bend and back bent qualified reached d=4a,180 ° intact,welded joint has a good cold bending performance.Known by the impact test results,welding,after cold rolling and hot rolled specimen impact toughness of welded joint compared with the parent material have declined,after post weld heat rolled specimen impact absorbing energy on average is slightly higher than weldment and post-weld cold rolling specimen.But either untreated or after post-weld cold rolling and hot rolling welding joint impact absorbing energy reached the parent metal more than 80%,to meet the relevant requirements.Through the analysis and observation to impact fracture morphology,relatively speaking,fracture morphology of the parent material is elongated and deep tearing dimples,toughness is best;Welding and post weld heat rolling weld fracture morphology is small and shallow dimples,toughness is better;Cold rolling after welding the weld fracture morphology is small dimples,tear ridges and serpentine pattern coexistence,toughness is poor.Through the results of this study,know that using the current plasma arc welding process can obtained the welded joints which made the performance meet the requirements.Post weld heat rolling technology can not only make joint performance improved,and the device is simple,low cost,and can be widely used in the actual production.After welding,cold rolling to the welding joints properties effect very little,so no need to adopt.