Preparating The Fe-Al Surfacing Layer On The Steel Substrateby By Twin Wire Welding With The AISi-steel Wire

In this thesis,Preparating the Fe-Al surfacing layer on the steel substrateby by twin wire welding with the AlSi+steel wire.Analysis and research about AISi wire-the ratio of the steel wire, welding specifications, preheat and post-weld heat treatment after a lot of welding process test. When the Φ1.2mm ER50S-6wire is applied to the master engine with the voltage of31.4,current of308A,without involving pulse,and Φ1.2mm ER4043aluminum wire to the slave engine.with voltage of19.8V,current of144A,involving pulse, and the welding speed is85cm/min,we can get the best Surfacing Layer without cracks and other defects by heated to550-600℃and then cooling with the furnace. With this parameter we success to surface more30weld seams.Also,mechanical properties tests are conducted to the surfacing layer of iron and aluminum intermetallic. The experimental results show that:microhardness of surfacing layer reach350-450HV. Shear strength reach280MPa. SEM show that fracture mechanism is brittle fracture. We can see the resistance of the weld is better than the Q235after the abrasion resistance test. Metallurgical microstructure analysis shows that the weld seam interface is composed of the columnar grain structure. And there are lots of precipitated phases in the columnar grain structure. With the iron, aluminum welding wire feed at the speeds of8m/min and4.5m/min the surfacing layer by ED AX spectroscopy detection display in the weld seam interface content of Fe is about71%t-77%and the content of aluminum reaches about24%-27%(at) and also the content of Silicon is about2%to4%. But in the vicinity of the fusion zone interface there are81%-86%of Fe and13%-17%of aluminum and1%-2%(at) of Silicon.The XRD analysis showed that Fe3Al exists in the surfacing Layer.