Study On Mechanical Properties And Corrosion Resistance Of E36 - RCW Corrosion Resistant Steel Welded Joints

The mechanical properties and corrosion resistance of the weld joints of the anti-corrosion E36-RCW steels welded with different welding methods were studied in this paper. Now several welding materials for the E36-RCW steel had been used, they included the electrode, flux cored wire, submerged arc welding wire, sintered flux etc. E36-RCW steels were welded with the manual arc welding, flux cored wire CO2 gas shielded welding and submerged arc welding to weld, and the mechanical properties of the welding joints were tested. Results showed that the mechanical properties of the three groups of welded joints met the requirements of IMO.In order to meet the needs of oil tanker efficient production, welding process of large heat input of the submerged arc welding was further researched. The anti-corrosion E36-RCW steels was welded with submerged arc welding (SAW) in three different heat inputs of 50,100 and 160KJ/cm, and mechanical properties of three kinds of weld metals were compared. The results showed that when the welding heat input added, the impact toughness of weld metals reduced but still can satisfy the performance index, and there were large engineering allowances. The microstructure of weld metals and the morphology of inclusions were analyzed. Further study found that acicular ferrite can increase the crack resistance of weld metal; when the welding heat input, the proportion of acicular ferrite in weld metal gradually reduced, the impact toughness of weld metal also decreased.Corrosion experiments of the three joints were conducted in the simulated environment of cargo oil tanks the deck and the lower base plate, Discuss the selected welding processes on the feasibility of the corrosion resistant steels, through analyzing corrosion morphology, microstructure, and inclusions of the weld joints. The results showed that the welded joints that were welded by the welding rod arc welding, flux cored wire CO2 gas shielded welding and submerged arc welding showed the good corrosion resistance in the simulated environment of cargo oil tanks. Further analysis found that, the structure of rust layer of the weld joints on the upper deck was the double-layer, The inner rust layer were relatively dense, outer rust layer were relatively loose. The corrosion resistance of weld metal welded by submerged arc welding was best in the simulated environment of cargo oil tanks the lower base plate. High welding heat input decreased the content of acicular ferrite of weld metal, and acicular ferrite could increase the corrosion rate of weld metal, So the corrosion resistance of weld metal welded by submerged arc welding was the best.