Study On Process Performance Of CMT For Dissimilar Metal Of Aluminum - Immersion Aluminum Plate

Al-steel dissimilar materials joining was widely used by CMT(cold metal transfer) for itsstable process, non splash and low heat input. However, the creation of the Al-Fe inter metallicbetween the Al and steel easily lead to the crack of the joint. For resolving this problem，the1mm SA1C dip aluminum steel plate was chosen to join the1mm6061aluminum plate usingCMT method. The effect of the welding process parameters on the weld appearance, porositydistribution, joint structure and mechanical properties were studied. The formation mechanismof the interfacial layer between aluminum and steel metal were analyzed.When using smaller welding speed，the available welding current should be in a largerange. With the increase of welding speed, the available effective welding current range wasreduced gradually in a small range. The best optimal parameters was concluded that: thewelding speed0.75m/min, the welding current is85A, wire feeding speed is5m/min, thewelding voltage12.6V.The dissimilar joint consists of the Al fusion zone, weld metal zone, inter layer zone andthe heat affected zone on the steel side. The Al fusion zone belong to the typical combinedsolidification and the growing direction is parallel to the welding temperature field and growinto the weld metal. The joining performance is excellent and no obvious defects were observed.The weld metal was composed of α-Al primary phase and Al-Si eutectic phase. The porositycould be controlled by adjusting the welding current and welding speed. The inter layer was Fe-Al-Si intermetallic.The intermetallic phase on the layer between the Al and the steel was focused studied.When the heat input was too low, the effective joining could not be obtained. When the heatinput was too large, the original inter layer was fully damaged and the new creation of theintermetallic was observed which lead to the crack of the joint. As long as the heat input wasoptimal, the original interlayer was not fully damaged and was leaved on the resultant weldmetal, the inter layer’s thickness is4-5μm.