Study On Weldability Of Underwater Wet Welding

Underwater wet welding is the most economical and practical technology inunderwater welding. But few papers covered the weldability of underwater wetwelding. This investigation mainly concentrates on the following aspects.The root causes of high diffusible hydrogen in underwater wet welding werediscussed in this paper firstly. The result indicated that the water of coating,waterproof materials and water of oxides on base metal are the main sources of highdiffusible hydrogen in underwater wet welding. And the impact of water around thewelding area on the amount of diffusible hydrogen is quite small.The paper investigated the the weldabilities of TS202A, TS206, TS208andBroco. The findings illuminated that all of them could strike the arc successfully andthe welding processes were stable and without any splashing. The appearance ofwelds of TS202A and TS206were good-looking and the welding slag could easilybeen removed, but protectional ability of slag was insufficient. The formation ofwelds of TS208and Broco were inferior and welding slag were difficult to remove,but slag can protect the welds well. The welding penertrations of Broco were deepestamong the four electrodes and the welding width of TS206is wider than that of otherthree electrodes. With the increase of current, the welding penertrations, weldingwidths and reinforcements of the four electrodes experienced upward trends. Whenthe welding speed was between2mm/s to4mm/s, the welding penetrations of TS202A,TS206and Broco rose along with the increase of welding speed, but the counterpartof TS208showed an opposite trend. The widths and reinforcements of the fourelectrodes decreased as the welding speeding went up.The exploration was made on welding processes of welding8.8mm X65plateswith TS208. And welding procedure qualification was conducted on the welded platessubsequently. The results of reduced-section tension test and charpy impact test metthe requirements of AWS D3.6:1999in B level, but bend tests results were unsatisfiedwith requirements. Whereas, the results indicated that the toughness of welds isinferior.Crosswise steam and lengthwise steam exert small influence on weldingstabilities of four electrodes. But all the welds leaned to one side of welding directionwhen they came across the crosswise steam and half area of the every weld was bareand without any slag. The welding width of the four electrodes decreased when they encountered the lengthwise steam.The quality of underwater welds which formed in0℃and15℃were comparedThe results showed that the welding penetration of TS202A, TS206and Broco in0℃is deeper than that in15℃, but the welding penetration of TS208is quite similarbetween in0℃and15℃. With the water temperature going lower, the welding widthbecame narrower and reinforcement decrease correspondingly. The microstructure ofwelds of TS206in0℃is inferior to that in15℃and the hardness of joints is alsohigher than that in15℃. However, the microstructure and hardness of welds of TS208and Broco did not show much difference between in0℃and in15℃.