Underwater Welding Research Articles

Corrosion resistance of welded joints made by underwater wet welding

One of the reasons of coming out of order of metal structures, operating in water environment, including sea conditions, is the corrosion. Thus, for example, the corrosion wear of metal of the ship hull underwater part can reach from 0.3 up to 0.5 mm/year. The corrosion of welds is the ever more critical situation. The rate of their fracture exceeds the rate of the base metal corrosion and in some cases it may reach 1-3 mm/year [1, 2]. The great selective corrosion in the form of fissures along the welds (on both sides) was observed in heat-affected zone (HAZ) metal of slot, butt welds and welds for welding-on to the basic workpiece, i.e. up to 1 mm/year, in some cases a through corrosion fracture of the fusion line (formation of blowholes) was observed [1]. In the opinion of the work authors [2] the welds are subjected to fracture due to the occurrence of thermal electromotive force between the parts welded under conditions of high electric conductivity of the sea water (Seebeck effect).
 To repair the corroded welded joints of metal structures, operated under the water, a wet underwater welding is used. At the E.O.Paton Electric Welding Institute the specialized flux-cored wires have been developed, which are designed for welding low-carbon and low-alloyed steels, including those of a higher strength. In the latter case the electrode materials of an austenite type are used to provide resistance against cold crack formation in the HAZ [3]. The work was aimed at study of corrosion resistance of welded joints with ferrite and austenite deposited metal, made by the underwater wet welding, under the conditions, which simulate the service conditions in sea water.

Influence of External Electromagnetic Fields on the Structure of Joints in the Course of Underwater Welding

Influence of External Electromagnetic Fields on the Structure of Joints in the Course of Underwater Welding

Post Underwater Wet Welding Heat Treatment by Underwater Wet Induction Heating

Wet welding procedures of Class A structural ship steels frequently fail to comply with the American Welding Society (AWS) D3.6M, Underwater Welding Code, in the maximum hardness criterion for the heat-affected zone (HAZ). The maximum hardness accepted in a welded joint is 325 HV for higher-strength steel (yield strength > 350 MPa). In multi-pass welds, this problem occurs frequently and is restricted to the HAZ of the capping passes. The HAZ of the root and filling passes are softened by the reheating promoted by their respective subsequent passes. This paper presents the results of exploratory research into postweld underwater electromagnetic induction heating. The objective of the research was to evaluate the ability of induction heating to soften the specific high-hardness HAZs in underwater conditions. The results showed that this technique could reduce the maximum HAZ hardness of low-carbon structural ship steel welds to values below 325 HV, which is the maximum accepted by AWS for Class A welds. The induction-heated zone reached a maximum depth of about 10 mm, which is considered adequate to treat the HAZ of cap-ping passes in underwater wet welds.

Analysis of underwater welding in Indonesian warship using low hydrogen electrodes

As a security unit for the territorial waters of the Republic of Indonesia, the Indonesian Navy is required for combat readiness to carry out security operations quickly and precisely. It is very important to the readiness of the Indonesian Navy's ABK Soldiers and the Republic of Indonesia's defense equipment for warships in carrying out security activities in the territorial waters of the Republic of Indonesia. This study discusses underwater wet welding in anticipating an emergency if the ship's hull is hit by a collision so that the hull has cracks or holes. This research method uses AH36 steel plate metal. Then, underwater wet welding was carried out on the AH36 plate using a low hydrogen type electrode. Before welding, the electrodes were subjected to a drying process to a temperature of 900C. Wet welding underwater is carried out at a depth of 5 meters in seawater. The results of underwater wet welding are NDT testing; penetrant test, radiography test, then also DT test; hardness test, tensile test, and test according to ASTM standard. Analysis of underwater wet welding results compared to atmospheric welding results as quality control, so that the percentage difference in mechanical properties can be known. The interesting thing from welding AH36 steel plate with underwater wet welding and applying low hydrogen electrodes is the minimal level of weld porosity defects in the welding results. So that the low hydrogen electrode can be used in welding AH36 steel plate in underwater welding applications.

Analysis of underwater welding in Indonesian warship using low hydrogen electrodes

Analysis of underwater welding in Indonesian warship using low hydrogen electrodes

Control of the Properties of Welded Joints in Wet Underwater Welding

The aquatic environment will negatively affect the processes that occur during the formation of a welded joint and leads to a deterioration in its properties. The welding conditions do not allow the use of traditional methods to improve the quality of the weld metal - preheating or subsequent heat treatment. One of the possible effective ways to solve this problem when welding with flux-cored wire is the use of external electromagnetic exposure. Generation of axial alternating control magnetic fields in the welding zone allows controlling the hydrodynamics of the molten weld pool. Because of the interaction of an external electromagnetic field with an electric field of the arc, ponderomotive forces appear in the weld pool, which leads to mixing of the liquid metal. Changing the direction of electromagnetic induction with a given frequency and interval, you can periodically change the direction of flow in the weld pool. Intensive reverse mixing of the melt occurs, during which the hydrogen accumulated in front of the crystallization front as a result of concentration compaction is removed from it, the melt temperature in the central and peripheral areas of the pool is averaged, which slightly reduces the crystallization rate of the weld pool, thereby increasing its degassing time. As a result, it was possible to significantly reduce the porosity of the weld metal (more than 8 times) and reduce the hydrogen content (more than 2.5 times). Metallographic studies showed a significant refinement of the structure both weld metal and the heat-affected zone (2 and 1.3 times, respectively), its homogenization and a decrease in the degree of defectiveness. Thus, the investigations showed that the external electromagnetic effect on the liquid metal pool in the process of wet welding underwater is a useful tool that allows you to control the processes that occur during the crystallization stage of the weld pool and significantly increase the ductility of the weld metal (more than 1.5 times).

An investigation on physical phenomena of water-jet assisted underwater wet laser welding technique under continuous and pulsed mode operation

This work presents the development and demonstration of a novel underwater wet laser welding technique, where unlike the conventional underwater wet laser welding, a water-jet parallel to the weld pool surface was introduced inside the water environment. The water flow was found to enhance the removal of water vapour formed at the laser-water-workpiece interface without creating hindrance to the molten weld bead, resulting in lower energy loss due to absorption and scattering, thus enhancing the laser energy coupling efficiency to the material. The process was studied for bead-on-plate welding on 4 mm stainless steel (SS) sheets using a 2 kW Yb-Fiber laser (wavelength 1.07 µm), with water column height of 5–15 mm, and a parallel water jet of speed 2–3 m/s, under continuous (CW) and pulsed mode (modulated power) laser operation. The major objective of the work was to study the effect of water flow and mode of laser operation on the formation and growth of vapour layer at the processing zone and investigate its effect on laser energy coupling efficiency. Further, their effect on weld bead geometry and microstructure was investigated. Welding operation with modulated laser power was found to produce higher weld depth compared to CW mode with same average laser power due to lower scattering loss and better energy coupling under pulsed mode operation. The micro-structural investigation has showed the formation of finer grains and oxide or carbide precipitation in case of underwater welding, indicating the enhanced cooling phenomena in this technique.

The State of the Art of Underwater Wet Welding Practice: Part 2

Developments in underwater wet welding (UWW) over the past four decades are reviewed, with an emphasis on the re-search that has been conducted in the last ten years. Shielded metal arc welding with rutile-based coated electrodes was established as the most applied process in the practice of wet welding of structural steels in shallow water. The advancements achieved in previous decades had already led to control of the chemical composition and microstructure of weld metals. Research and development in consumables formulation have led to control of the amount of hydrogen content and the level of weld porosity in the weld metal. The main focus of research and development in the last decade was on weldability of naval and offshore structural steels and acceptance of welding procedures for Class A weld classification according to American Welding Society D3.6, Underwater Welding Code. Applications of strictly controlled welding techniques, including new postweld heat treatment procedures, allowed for the welding of steels with carbon equivalent values greater than 0.40. Classification societies are meticulously scrutinizing wet welding procedures and wet weld properties in structural steels at depths smaller than 30 m prior to qualifying them as Class A capable. Alternate wet welding processes that have been tested in previous decades — such as friction stir welding, dry local habitat, and gas metal arc welding — have not achieved great success as originally claimed. Almost all of the new UWW process developments in the last decade have focused on the flux cored arc welding (FCAW) process. Part 1 of this paper covered developments in microstructural optimization and weld metal porosity control for UWW. Part 2 discusses the hydrogen pickup mechanism, weld cooling rate control, design, and qualification of consumables. It ends with a description of the advancements in FCAW applications for UWW.

Effect of Water Flow on Underwater Wet Welded A36 Steel

Underwater wet welding (UWW) combined with the shielded metal arc welding (SMAW) method has proven to be an effective way of permanently joining metals that can be performed in water. This research was conducted to determine the effect of water flow rate on the physical and mechanical properties (tensile, hardness, toughness, and bending effect) of underwater welded bead on A36 steel plate. The control variables used were a welding speed of 4 mm/s, a current of 120 A, electrode E7018 with a diameter of 4 mm, and freshwater. The results show that variations in water flow affected defects, microstructure, and mechanical properties of underwater welds. These defects include spatter, porosity, and undercut, which occur in all underwater welding results. The presence of flow and an increased flow rate causes differences in the microstructure, increased porosity on the weld metal, and undercut on the UWW specimen. An increase in water flow rate causes the acicular ferrite microstructure to appear greater, and the heat-affected zone (HAZ) will form finer grains. The best mechanical properties are achieved by welding with the highest flow rate, with a tensile strength of 534.1 MPa, 3.6% elongation, a Vickers microhardness in the HAZ area of 424 HV, and an impact strength of 1.47 J/mm2.

Underwater Laser Welding of Pure Ti: Oxidation and Hardening Behaviors

The local dry underwater laser welding of cp-Ti, with air as an assisting gas, and in a simulated underwater facility was researched, aiming to find a viable and economical method for repairing titanium alloy underwater vehicles in situ in the future. Macro-morphology, microstructure, and microhardness of the cp-Ti laser welds, as a function of welding parameters, were experimentally characterized. The oxidation and hardening behaviors of the welds were also studied in detail. It was found that local dry underwater laser welding with air assisted blowing is feasible for obtaining a complete and glossy weld. Compared with a weld in atmosphere, the cross-section morphology of the weld was almost unaffected by the special underwater welding environment. The weld presented a three-layer structure. High temperature and high pressure water vapor and local blowing are the direct causes of weld oxidation, and porosity defects further aggravate the oxidation behavior. The oxygen-enriched areas were mostly concentrated in the top area of the weld center and near the fusion zone, because of the higher number of grain boundaries and phase boundaries. In addition, the partial oxidation caused by local blowing and water vapor atmosphere, and also the higher strength acicular martensite caused by the rapid cooling effect of water, will lead to weld hardening. However, adjusting the welding process parameters, such as increasing the welding speed, can effectively reduce the microhardness of the weld. Our findings can provide an understanding of the influence of water environment on underwater laser welding, and verify the feasibility of a more economical method for the in situ repair of large underwater facilities.

Influence of water environment on wet underwater manual self-propagating high-temperature synthesis welding

Manual SHS welding is a kind of quick welding technique for emergency maintenance. In this paper, influence of water environment on the welding quality and performance has been studied. Results showed that water had significant influence on the welding. The visibility for welding was significantly reduced, which increased the difficulty of welding operation. The brightness of weld pool in wet welding were darker than that in land welding and the shape of combusting arc was compressed significantly. The highest temperature of weld pool in underwater welding was obviously lower than that in land welding, and the cooling rate of HAZ was faster. The welding quality was worsen remarkably by water. The weld seam was irregular and discontinuous, and a lot of gas pores and inclusions existed in the weld metal. And the amount of deposited metal was obviously reduced. Microstructure analysis showed that the matrix of weld metal was α-Cu solid solution, with Fe-rich second phase distributing orderly on it, which was same as that of land welding. But water caused many apparent inclusions and pores in the weld metal. The tensile strength of weld joints for underwater welding was obviously lower than that of weld joints for land welding.

The State of the Art of Underwater Wet Welding Practice: Part 1

Developments in underwater wet welding (UWW) over the past four decades are reviewed, with an emphasis on the research that has been conducted in the last ten years. Shielded metal arc welding with rutile-based coated electrodes was established as the most applied process in the practice of wet welding of structural steels in shallow water. The advancements achieved in previous decades had already led to control of the chemical com-position and microstructure of weld metals. Research and development in consumables formulation have led to control of the amount of hydrogen content and the level of weld porosity in the weld metal. The main focus of research and development in the last decade was on weldability of naval and offshore structural steels and acceptance of welding procedures for Class A weld classification according to American Welding Society D3.6, Under-water Welding Code. Applications of strictly controlled welding techniques, including new postweld heat treatment procedures, allowed for the welding of steels with carbon equivalent values greater than 0.40. Classification societies are meticulously scrutinizing wet welding procedures and wet weld properties in structural steels at depths smaller than 30 m prior to qualifying them as Class A capable. Alternate wet welding processes that have been tested in previous decades — such as friction stir welding, dry local habitat, and gas metal arc welding —have not achieved great success as originally claimed. Al-most all of the new UWW process developments in the last decade have focused on the flux cored arc welding (FCAW) process. Part 1 of this paper covers developments in microstructural optimization and weld metal porosity control for UWW. Part 2 discusses the hydrogen pickup mechanism, weld cooling rate control, design, and qualification of consumables. It ends with a description of the advancements in FCAW applications for UWW.

Numerical Simulation on the Effect of Gas Pressure on the Formation of Local Dry Underwater Welds

Numerical Simulation on the Effect of Gas Pressure on the Formation of Local Dry Underwater Welds

Influence of external electromagnetic field on parameters and defects of crystal lattice of metal of welded joints during underwater welding

The Paton Welding Journal, 2021, №01. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Вплив зовнішнього електромагнітного поля на параметри та дефекти кристалічної гратки металу зварних з’єднань при зварюванні під водою

Вплив зовнішнього електромагнітного поля на параметри та дефекти кристалічної гратки металу зварних з’єднань при зварюванні під водою

Study of weld form and weld bead in bottom position at semi-automatic underwater wet welding

Some features of underwater mechanized and automatic wet welding with pulse feed of the electrode wire are considered. The conditions for experimental research to identify the parameters of forming of the weld metal at different parameters of pulse feed of the electrode wire are described. Regression equations describing the dependences of the size of the roll on the parameters of pulse feed and contour plots and response surfaces of the marked dependences are presented.

DEVELOPMENT OF ELEMENTS OF THE TECHNOLOGY OF CREATION OF THE BIONIC STRUCTURE OF PROTECTIVE CLOTHING MATERIAL AGAINST THE THERMAL EFFECTS OF UNDERWATER WELDING

The article is devoted to research and development of technology elements for designing and manufacturing a new polymer material based on heat-resistant silicone with a special surface structure in the form of an ordered relief matrix that simulates a bionic surface (“shark skin”), created on the basis of digital processing of bionic models, providing a barrier against thermally dangerous particles of underwater welding. In order to determine the stability of the developed material to the thermal effects of a short-term open flame, experimental tests were carried out, which made it possible to determine that the damage to the surface of the new silicone material is insignificant. It does not lead to the destruction of the overall thickness of the protective material and further risks for the internal foam heat-protective layer of wetsuits – damage to the surface of the protrusions of the relief matrix (no more than 40 % of the initial parameters). The developed material allows one to increase the protection of the main surface of the clothing material.

Effects of PTFE on operational characteristics and diffusible H and O contents of weld metal in underwater wet welding

For this paper, oxidizing rutile type tubular wires were developed by using polytetrafluoroethylene (PFTE) as a flux ingredient in concentrations up to 21 %. The welds were carried out in a flat position at a depth of 0.5m by using both negative (DCEN) and positive electrodes (DCEP). Welding electrical signals were acquired and processed to determine process characteristics voltages, and quantify the occurrence of short-circuit and arc extinction. The influence of flux composition on weld bead shape and its hydrogen and oxygen contents were also evaluated. For both polarities, welding current increased with the addition of PTFE to the flux probably because it required more energy to melt and dissociate. The additions of PTFE also increased bead penetration and reinforcement and reduced the width as well as the H and O contents in the weld metal. These results were more pronounced with DCEN. Weld porosity was not observed for all formulations. Therefore, tubular wires with PTFE additions to the flux may have potential operational advantages for underwater welding including the reduction of weld metal oxygen and diffusible hydrogen contents particularly when used with DCEN.

Recent Trends in Friction Stir Welding

Welding technology has brought a milestone change in metal joining processes and its applications and almost eradicated some other metal joining processes (riveting etc.). Friction stir welding is a solid state welding technique comparatively recent than others. This study intends to elucidate the current scenario in the field of friction stir welding with special focus on dissimilar metal friction stir welding, underwater friction stir welding and hybrid friction stir welding. Further, future challenges in the friction stir welding have been described.

The Effect of Polarity and Hydrostatic Pressure on Operational Characteristics of Rutile Electrode in Underwater Welding.

In order to provide a better understanding of the phenomena that define the weld bead penetration and melting rate of consumables in underwater welding, welds were developed with a rutile electrode in air welding conditions and at the simulated depths of 5 and 10 m with the use of a hyperbaric chamber and a gravity feeding system. In this way, voltage and current signals were acquired. Data processing involved the welding voltage, determination of the sum of the anodic and cathodic drops, calculation of the short-circuit factor, and determination of the melting rate. Cross-sectional samples were also taken from the weld bead to assess bead geometry. As a result, the collected data show that the generation of energy in the arc–electrode connection in direct polarity (direct current electrode negative-DCEN) is affected by the hydrostatic pressure, causing a loss of fusion efficiency, a drop of operating voltage, decreased arc length, and increased number of short-circuit events. The combination of these characteristics kept the weld bead geometry unchanged, compared to dry weld conditions. With the positive electrode (direct current electrode positive-DCEP), radial losses were derived from greater arc lengths resulting from increasing hydrostatic pressure, which led to a decrease in weld penetration.