Underwater Welding Research Articles

水中スタッド溶接の研究

The authors have developed a stud welding as one of the underwater welding methods, the stud welding set for surface use as it is can be applied for underwater use, but the gun must be modified to watertight and an air shroud must be added to gun in which air is fed and expells water and in addition fine porous material was set around the slots of the shroud, preventing water pushed back in the welds.Fundamental study was conducted at 0.3m and 50m deep. Welded strength obtained underwater, even though 50 m deep underwater, was no weaker than that made on the surface. Application study was conducted in an 8 m long × 4 m wide × 2 m deep pool, where a welder in a diving suit carried out stud welding with successful result.

GENERALIZED SUMMARY OF THE STATE—OF—THE—ART OF UNDERWATER WELDING

ABSTRACTThe principle aims of this paper are: a) to generate additional interest within the Naval Engineering profession regarding the benefits and general potential of Underwater Welding, b) to eliminate somewhat the aura of mystery that seems to surround Underwater Welding, and c) to cite some of the private industry potential for assisting the Naval Engineering profession in this increasingly important field. The contents of the paper are primarily intended for the benefit of Naval Engineering personnel having an interest and concern in Underwater Welding and its potential.

On the solution of the heat equation with time dependent coefficient

This article devises an analytical solution to the practical industrial applications, in which the thermal boundary conditions are varying in both time and space around a cooling or heating source moving along a finite domain. Among the various applications of such a solution, the jet impingement cooling and underwater welding and cutting would be of great importance. Afterwards, a numerical example regarding the temperature field caused by an underwater solid state welding process is provided by using the developed analytical solution. Finally, in order to evaluate the accuracy of the presented analytical model, the analytically obtained results are compared with the results attained by FEM-Comsol commercial software.

フラックス入りワイヤによる水カーテン式水中炭酸ガスアーク溶接(第2報)

Authors have proposed an underwater welding pocess called water curtain type underwater CO2 arc welding method. It was already reported that may succeeded in single layer butt welding at 120 cm/min high speed as underwater welding by using flux cored wires in this process. Now, all deposited metal are made and thick plates are welded with multiple pass by using the said wires.The conclusions that may be drawn from this study are:1) Hardness of welds becomes lower under use of mixed shielding gas of O2 with Ar and CO2.2) In tensile tests of all deposited specimens executed by underwater welding, the elongation was 9-13%.3) After heat treatment of these specimens at 350°C for 1 hr, the elongation became 14-24%.4) Welds executed by two layer butt welding of 6mm thick plates and six layer butt welding of 20mm thick plates turned out satifactory in tensile test and bending test.

フラックス入りワイヤによる水カーテン式水中炭酸ガスアーク溶接について(第1報)

We have proposed the water curtain type underwater CO2 arc welding as a method of underwater welding. With this method we could make nozzle-to-work distance longer than 2-3 times compared with that for conventional underwater CO2 arc welding because of good shielding effects.But, in case of welding with solid wires, welding speed was limited up to 30 cm/min. For the purpose of solution to this trouble, we tried single pass butt welding on mild steel at 0.3 m underwater by using flux cored wires.Results obtained are as follows:1) At high speed welding 120 cm/min as underwater welding, we succeeded to get good welds without blowholes and cracks.2) The welds obtained from this method have excellent mechanical properties at bending test and tensile test.3) Maximum hardness in welds was Hv 300.4) This method had a weak point of poor visibility in the cause of melting of flux and slag into the water.

水中溶接法の現状

水中溶接法の現状

UNDERWATER TIE-IN OF 24 INCH OFFSHORE PIPELINE

A 47 mile 24 inch underwater pipeline was required to link the Esso/BHP Halibut field to onshore production facilities. To hasten the completion of this line. Esso elected to use two pipe laying barges: one starting from the shore and one from the platform, and to make an underwater tie-in where the two lay barges met. To complete the tie-in, Esso engaged Ocean Systems Australasia Pty Ltd to make a sea floor welded connection in their underwater welding habitat, using the TIG (Tungsten Inert Gas) hyperbaric welding process and the saturation diving technique. The support vessel for this work was the semi-submersible derrick barge Choctaw. The tie-in was 38 miles offshore in the open waters of the Bass Strait in 218 feet of water. The pipe wall thickness at the tie-in was three-quarter inch.The Halibut 24 inch pipeline underwater tie-in was successfully completed in a total elapsed time of 383 hours (15 days 23 hours) compared with the estimated total time of 348 hours. Three major factors contributed to the success of the operation; these were:The ability of the semi-submersible derrick barge Choctaw to stay on location during the bad weather when swells of up to 20 feet were experienced.The efficient organisation and implementation of the work by Ocean Systems.The close alignment of the two sections of the pipeline on the seabed by the pipelaying contractor, Ingram Contractors Australia Pty Ltd.

水カーテン式水中炭酸ガスアーク溶接法の研究

CO2 arc welding which is employed in the wet underwater welding has the following advantages.(1) The process is simple to operate.(2) In the safety aspects, the lower open voltage characteristics of arc welder is particulary helpful to avoid electric shock.(3) Welds can be made in all positions.But, in conventional wet underwater CO2 arc welding, nozzle-base metal distance was not more than 4 mm, therefore the welding operation was very difficult.We studied the following system that was called curtain water type underwater CO2 arc welding aimed to improve this problem. In the dual flow system which we used, curtain water was introduced from the outer nozzle. By this system we could take nozzle-base metal distance about two times longer than that for conventional shielding system. As the results of radiographic examination, no difficulty was found to obtain the welds without blowholes. At the first step to develop this process, we report experimental results of down hand position butt welding for mild steel.

水中溶接に関する研究(第2報)

The reason why most of the coated electrodes can give a sound weld metal.even under water but low hydrogen type electrode and semi-automatic CO2 welding are apt to produce blowholes in an underwater weld metal is investigated in this report by oscillograms, chemical analysis of gases in blowhole and the configuration, the microstructure and the hardness of deposited bead made under water as compared with those in air.Results are as follows;1) Arc of ilmenite, high titania, lime titania, high iron oxide-iron powder and high cellulose type electrodes is stable and their droplet transfer in arc is spray type, while underwater arc of low hydrogen type electrode and semi-automatic CO2 welding has a considerably long arc-disappearing time on oscillogram and it seems difficult to reignite arc.2) Main component of blowhole gas in an underwater deposit is hydrogen, which is very different from the case of usual welding in air.3) Microstructure of the heat affected zone of an underwater weld of mild steel is bainitic-martensitic and its hardness is very high.4) The cause of blowhole formation by low hydrogen electrode and CO2 welding is probably attributed to their insufficient reignition of arc on a cold base metal under water, which makes solidification rate of weld metal so extraordinarily fast that a large amount of hydrogen produced by arc under water can not escape from molten metal.

水中溶接に関する研究(第1報)

Underwater welding was experimentally carried out in a water box by coated electrodes and semiautomatic CO2 welding. And It was investigated the occurrence of blowhole was affected by various welding parameters.The following results were obtained:1) Sound deposited metal and welded joints were obtained under flat, horizontal and vertical positions from every coated electrode except the low hydrogen type one. Kinds of power sources and water proofing coatings of electrodes had no special effect on appearance and soundness of bead.2) Welded joints by coated electrodes were superior in tensile strength but inferior in ductility to the mild steel base metal.3) It was difficult to get a sound weld metal by low hydrogen type electrode under water. Blowholes in weld metal were remarkable in all welding current and arc voltage ranges.4) It was also considerably difficult to obtain a weld metal quite free from blowholes by underwater semiautomatic CO2 welding.

水中におけるプラズマ溶接

Since plasma arc has been considered to be a suitable heat source for wet welding owing to the following factors, the feasibility of underwater welding by it is studied.(1) Plasma arc co-operating with plasma jet can be generated easily and kept in stable state in water, and is less sensitive to variations in torch-to-work spacing.(2) As energy transferred from plasma arc to work is highly concentrated, fusion efficiency of work is high.(3) Plasma arc is constricted by torch nozzle, so its directional property is excellent.(4) Plasma jet, kept operating all the diving time, acts as illuminating light source and makes it easy for the welder to work in water.As the first step to develop the process, preliminary experiments on some of the above-mentioned factors are made in simple welding environment, such as in city water and at water depth of 20 cm. And then butt welding and fillet lap welding under the conditions adopted according to information obtained in the preliminary experiments are done by using steel as base metal for a welded structure of 6 mm in thickness. Results of experiments show that underwater welding by plasma are (semi-transferred type plasma jet, i.e., plasma jet co-operates with plasma arc) can be done easily and stably and the weld has excellent properties in both tensile strength and notch toughness, though the weld metal includes blowholes to some extent. In conclusion, it is ascertained that this process can be put to practical use.

水中溶接の現状

水中溶接の現状

Underwater Welding - Present Status and Future Scope

Welding in offshore and marine application is an area of research and understanding where, many problems are still unsolved. In the present paper, a brief description of the different commercial underwater techniques has been made. The problems in underwater welding have also been discussed in context to the existing welding techniques. Detailed description of a few advanced welding techniques has also been made. Finally, the scope of further research has been recommended. Key words: Under water welding, TIG, MIG, SAW, laser, frictionDOI: 10.3329/jname.v3i1.927Journal of Naval Architecture and Marine Engineering 3(2006) 39-48