Research On Special High Efficiency Wire Of CO₂Gas Shielding Arc Welding For Construction Machinery

The use of CO₂gas shielded welding occupies approximately70%inproducing steel structure of construction machinery,with equipments popularizationand mature manufacturing technology,welding productivity of steel structure is thekey factor of the development of enterprises and improving productcompetitiveness.According to the domestic situation of constructionmachinery,ER50-6is the most widely used welding wire,so develop a new wirewith same strength standard、 higher weld efficiency、 less spatter and betterformation of weld by adding trace alloy and chemical composition optimization hasgood practice value in engineering.Exploring reasonable chemical composition of new wire by the method ofwelding in the area where adds mixed trace alloy powder,then ascertain thecomposition area of this new wire rod.Test the physico-chemical performance byusing direct-reading spectrometer,optical microscope,micro-hardness tester,universal material testing machine. After husking、 drawing and copperelectroplating processes rod is made into wire,do welding procedure test andanalyze the mechanism of trace alloy elements on welding spatter、 weldingpenetration and welding arc etc.The results show that:（1）It can effectively increasethe welding penetration depth of more than50%by adds mixed trace alloy powderinto welding area.（2）With the adding of alloy elements the drawing performance ofwire rod didn’t be deteriorated and there are not cracks、dents、sharp edges or theother defects on it’s surface;the microstructure is fine and uniform in hot rolling orannealing condition.（3）Compared with normal ER50-6welding wire, weldingtechnological properties is better by using new wire in the same weldingparameters,welding spatter loss coefficient is low,welding gap is more beautifuland the penetration is deeper.（4）Ti Al and the other trace alloy elements canmoderately reduce the activity of Oxygen in welding process which has an effect onsurface tension of molten pool and welding arc so that it can decrease spatter losscoefficient and increase depth-to-width ratio.Through the welding procedure test can find that:when weld heat input increase from18KJ/cm to25.5KJ/cm,the mechanical property especially averagelow temperature impact toughness of deposited metal decrease by a large marginfrom81.0J to35.3J.The main reason is that there is grain coarsening in somedegree along with the increase of weld heat input though observing themicrostructure of deposited metal and fusion zone.But when welding in high heatinput（25.5KJ/cm）,the mechanical property of deposited metal also can meet thespecification in GB/T8110with using the new wire of CO₂gas shielding arcwelding.