Underwater Welding Research Articles

Fatigue crack growth rate in underwater wet welds: out of water evaluation

The characteristics of fatigue crack propagation in welds produced in conventional conditions (welds made out of water) and in underwater repair welding conditions (underwater wet welding) were evaluated out of water. The fatigue crack growth rates da/dN showed considerable dependence on pore density and distribution, factors that vary significantly with the welding process and the environment. Variations in the fatigue crack propagation rate were correlated with analysis of the fracture surface in the zone of stable crack propagation. The results of this study show that the underwater wet welding procedure produces weld metal resistant to fatigue, which is suitable for use at low applied stresses in offshore structures.

A hybrid impedance control scheme for underwater welding robots with a passive foundation in the controller domain

A hybrid impedance control scheme for the force and position control of an end-effector is presented in this paper. The interaction of the end-effector is controlled using a passive foundation with compensation gain. For obtaining the steady state, a proportional–integral–derivative controller is tuned with an impedance controller. The hybrid impedance controller is implemented on a terrestrial (ground) single-arm robot manipulator. The modeling is done by creating a bond graph model and efficacy is substantiated through simulation results. Further, the hybrid impedance control scheme is applied on a two-link flexible arm underwater robot manipulator for welding applications. Underwater conditions, such as hydrodynamic forces, buoyancy forces, and other disturbances, are considered in the modeling. During interaction, the minimum distance from the virtual wall is maintained. A simulation study is carried out, which reveals some effective stability of the system.

Numerical study on the temperature field of underwater flux-cored wire arc cutting process

The fast development of ocean engineering makes the underwater cutting more and more important. In present study, a special underwater wet cutting method, namely the underwater flux-cored wire arc cutting (FCAC) was introduced. The underwater cutting experiment was conducted using flux-cored wire cutting method, and experimental as well as numerical analysis was carried out to investigate the temperature field during underwater FCAC process. According to the mechanism of the underwater FCAC, double ellipsoid heat source model considering arc heat as well as chemical heat was introduced, and the boundary condition of pool boiling heat transfer was selected. The calculated thermal cycles during underwater FCAC process match well with those acquired by the experiment, which proves the model and boundary condition in this study to be applicable for underwater FCAC. It is found that the calculated t8/5 value is shorter than 0.5 s, which is much shorter than the one of air-arc cutting process and the one of underwater welding process. In addition, the heat affected zone (HAZ) near the cut cavity is determined, which is expected to facilitate the further research on the cutting mechanism, as well as the optimization of cutting parameters.

A Review on Under Water Welding Process

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 classification of underwater welding is made, the principals involved and the advantages and disadvantages of the various types of underwater welding are described. Further discussion is made over the present conventional and some advanced techniques used. Finally, the scope of further research has been recommended. 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. INTRODUCTION The fact that electric arc could operate was known for over a 100 years. The first ever underwater welding was carried out by British Admiralty – Dockyard for sealing leaking ship rivets below the water line. Underwater welding is an important tool for underwater fabrication works. In 1946, special waterproof electrodes were developed in Holland by ‘Van der Willingen’. In recent years the number of offshore structures including oil drilling rigs, pipelines, platforms are being installed significantly. Some of these structures will experience failures of its elements during normal usage and during unpredicted occurrences like storms, collisions. Any repair method will require the use of underwater welding. CLASSIFICATION: Underwater welding can be classified as 1) Wet Welding 2) Dry Welding In wet welding the welding is performed underwater, directly exposed to the wet environment. In dry welding, a dry chamber is created near the area to be welded and the welder does the job by staying inside the chamber. WET WELDING: Wet Welding indicates that welding is performed underwater, directly exposed to the wet environment. A special electrode is used and welding is carried out manually just as one does in open air welding. The increased freedom of movement makes wet welding the most effective, efficient and economical method. Welding power supply is located on the surface with connection to the diver/welder via cables and hoses POWER SUPPLY USED : DC POLARITY : -VE POLARITY IJRDO-Journal Of Mechanical And Civil Engineering ISSN: 2456-1479 Volume-1 | Issue-12 | December,2015 | Paper-4 29

Effect of Underwater Welding in Marine Environment and Surface Welding to Mechanical Properties of Steel Weld Joint

The offshore structure gradually will get damage. A number of offshore structure maintenance method require underwater working. Because of that, underwater welding become an importance thing. Through this research,will be assessed on changes in mechanical properties of steel weld joint in marine environmental. With same weld parameter, welding process also do in freshwater and on land for comparisonvariable. Welding process do in 0.2m depth with SMAW wet welding method on 1G position using AWS E6013 electrode coated with wax. After doing research, it is found that the tensile strength of welds in the marine environment is a little larger than the tensile strength in freshwater and on land, ie 49.44 kgf/mm2> 49.41 kgf/mm2 > 48.99 kgf/mm2. Hardness index value of welded steel in the marine environment is also higher than the value of the weld hardness results in freshwater and on land, in the amount of 195.37Hv10>181.13Hv10>153.6Hv10. The value of tensile strength and hardness values in the marine environment welds slightly larger than in freshwater due to the amount of grain mertensit phase. Ductility properties of the weld results in the marine environmentis smaller than the weld results in freshwater and land, it is characterized by a decline inelongation and reduction of area in underwater welding. From the observation of metallographic microstructure underwater welding it appears that phase grains coarser than the microstructure of welding on land. This can happen because the weld metal suffered liquefaction then freezes so quickly that opportunity grain experiencing severe grain growth during thawing did not get transformed into finer grains, so that the material is harder but brittle.

Numerical and experimental study on the effects of welding environment and input heat on properties of FSSWed TRIP steel

In this paper, the effect of input heat and welding environment on microstructure and mechanical properties of friction stir spot welded TRIP steel sheets were investigated. Six types of joints produced in both air and water environments and under rotational speeds of 900, 1350, and 1800 rpm. Then, the microstructure and mechanical properties of them were studied. The thermal histories, strain, and strain rate distributions of cases obtained by finite element modeling. According to the temperature and strain distribution and microstructural observations, four different zones determined in welding region: stir zone, thermomechanically affected zone, and high and low temperature heat-affected zones. It is obtained at in-air welds by increasing the rotational speed, the strength of joints increase to a maximum value because of higher strain rate and more recrystallization of prior austenite grains. The strength then decreases due to high amount of heat input and growth of recrystallized grains. Thermal history of underwater welds showed lower peak temperature and rapid cooling rate. Also, by increasing rotational speed in underwater joints, the strength and hardness increased because of microstructure refinement. The fracture surfaces of joints showed a dimple pattern ductile fracture in all cases except 1800 rpm in-air joint that the fracture was less ductile which agrees with lower tensile elongation of it.

Fiber Laser Welding of Thin Nickel Sheets in Air and Water Medium

In the present research, fiber laser beam welding (FLBW) of thin nickel sheets in two different mediums, i.e., air and water, has been investigated. In air medium, the fiber laser welding operations are performed at different laser powers (60, 80 and 100 W) and scanning speeds (40, 60 and 80 mm/min). Underwater welding operations have also been investigated at three different laser powers (330, 350 and 370 W) and two different scanning speeds (20 and 40 mm/min). The results show that welding of Ni sheet with higher laser power results in prominent heat-affected zone, increase in both microhardness and wt% of oxide formation in the weldment in both air and water medium. It is found that the increase in microhardness of weldment leads to the reduction in grain size. The heat-affected zone is reduced when scanning speed is increased. The wt% of oxygen increases with an increase in power during FLBW operation at constant scanning speed, and the oxide formation can be controlled by varying the laser power and scanning speed. The welding medium has significant influences on the properties of the weldments.

Aging kinetics of friction stir welded Al-Cu-Li-Mg-Ag and Al-Cu-Li-Mg alloys

Friction stir welding under ambient cooling conditions, using tool rotation rate of 800rpm and welding speed of 200mm per minute was carried out on 2195 and 2199 Al-Li alloys. Underwater welding was also performed on both the alloys using a pool on the top of workpiece. Post weld heat treatment for various durations was conducted to study the effect of alloy chemistry on aging kinetics in various metallurgical zones developed during welding. Vickers microhardness, differential scanning calorimetry, and transmission electron microscopy results showed that low dislocation density after recrystallization in weld nugget results in delayed aging kinetics for both the alloys. Ag containing alloy 2195 showed faster aging response compared to Ag-free alloy 2199. Coarse precipitates at grain boundary and in the grain interior were found responsible for loss of non-recoverable strength in heat affected zone for both the alloys.

Heat input and metal transfer influences on the weld geometry and microstructure during underwater wet FCAW

FCAW experiments were conducted under water and in the air. Influences of surrounding water on the weld geometry and weld metal microstructure were investigated through analyzing the heat input and metal transfer. The underwater welds have a lower proportion of acicular ferrite and pro-eutectoid ferrite. Two metal transfer modes in wet FCAW were observed, i.e. repelled globular transfer and surface tension based quasi-short-circuit transfer. The former one is the main cause of asymmetric and less uniform weld appearance.

Thermo-mechanic and Microstructural Analysis of an Underwater Welding Joint

Abstract The aim of this research is to present a comparative analysis between theoretical and experimental thermal fields as well as a microstructural behaviour and residual stresses applying multiple weld beads in the joint of two API 5L X52 pipe sections. The thermal field, microstructural and residual stresses were numerically modelled through the finite element method (FEM) and compared to experimentally. The simulation conditions used in the FEM analysis were similar considerations to the underwater welding conditions. The finite element analysis was carried out, first by a non-linear transient thermal analysis for obtaining the global temperature history generated during the underwater welding process. Subsequently, a microstructural behaviour was determined using the temperatures distribution obtained in the pipe material by calculating the structural transformations of the material during the welding process, and finally a stress analysis was developed using the temperatures obtained from the thermal analysis. It was found that this simulation method can be used efficiently to determinate with accuracy the optimum welding parameters of this kind of weld applications.

Weldability of S460ML High Strength Low Alloy Steel in Underwater Conditions

The paper presents experimental evaluation of susceptibility of the high strength S460ML steel to cold cracking in the conditions of wet welding with the use of covered electrodes. From the results of Tekken tests it was found out that the investigated steel was characterised, in the conditions of the carried out experiments (underwater wet welding and air welding with rutile electrodes), of high susceptibility to cold cracking. Maximum hardness of HAZ in most cases do not fulfill criterion of PN-EN ISO 15614-1 standard: exceeds 380HV10.

The Effect of Wet Underwater Welding on Cold Cracking Susceptibility of Duplex Stainless Steel

Abstract The present work was conducted to assess the weldability of duplex stainless steel in underwater conditions. Metal manual arc welding (MMA) with the use of coated electrodes was used in the investigations. Tekken weldability tests were performed underwater at 0.5 m depth and in the air. Nondestructive tests, metallographic examinations of welds, ferrite content assessment in microstructure and hardness test were performed. The good weldability at underwater conditions of duplex stainless with the use of MMA method was confirmed, however difficulties in stable arc burning were revealed.

Influence of Aqueous Media on the Gas Saturation of Weld Metal in the Course of Underwater Welding of 12KH18N10T Steel

We estimate the potentials of hydrogenation and oxidation of aqueous media, the degree of gas saturation of the weld metal, and the mechanical properties of a welded joint obtained as a result of wet underwater welding with an experimental self-shielding wire. We study the influence of aqueous media on the physicochemical and metallurgical processes in the course of underwater arc welding. We also develop a complex of metallurgical and technological measures aimed at guaranteeing the high quality of joints formed by this kind of welding of 12Kh18N10T corrosion-resistant austenitic steel.

Microstructure and mechanical properties of underwater friction taper plug weld on X65 steel with carbon and stainless steel plugs

Underwater friction taper plug welding for X65 pipeline steel was performed using Q345 structural steel and 316L stainless steel plugs. Weld microstructures, defects formation and mechanical properties were investigated. Using Q345 plugs can produce defect free and overmatching welded joints whose impact toughness was also favourable. Lower bainite and lath martensite in the weld zone resulted in high hardness with maximum value up to 418 HV10. Using 316L plugs can significantly reduce weld zone hardness due to austenite dominated microstructure. Microcracks can easily emerge at and may propagate along γ–δ phase boundaries to form macrocracks. Intermittent cracks were found along the bonding interface of all the 316L plug welds, which should be caused by the relief of the residual stress.

Scrutinize Research on Underwater Welding Process: A Review

Scrutinize Research on Underwater Welding Process: A Review

Effect of Water Velocity on Underwater In-Service Welding

In-service welding of the pipeline steel is performed under the environment where the delivery of the high pressure pipeline doesn’t stop. When welding under the water, there are high-pressure gas flowing in the pipeline and water flowing outside, causing a difficult and possibly risky of the welding operation. The process of in-service welding with SYSWELD was adopted to establish a geometric model of pipeline repair that the pipeline steel using finite element numerical modeling of the underwater in-service welding was carried out. Furthermore, this study focused on the effect of water velocity on the temperature field and stress field when repairing the in-service pipeline by welding. The results indicated that the water velocity of the pipe has a great influence on the temperature field and the residual stress field.

An analytical solution to the thermal problems with varying boundary conditions around a moving source

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.

Influence of weld geometry and process parameters on the quality of underwater wet friction taper plug welding

In the present study, a number of joints were fabricated successfully on DH36 marine steel sheet in underwater wet based on friction taper plug welding (FTPW). The influences of the plug and hole geometry parameters combination on the quality of welded joint forming were first investigated. It was found that tapered holes and plugs were the preferred choice and a suitable cone angle range was obtained. Using the preferred hole and plug designed further expand the range of welding parameters to explore process parameters influence on the welding quality. Bonding mechanism and microstructural evolution to FTP welds were investigated with multiple observations. Mechanical properties of the obtained joints were also evaluated with tensile and Charpy impact tests by reference to AWS D3.6 Underwater Welding Code. The best result is found as the joint welded with 7500 rpm and 40 kN which has 535.6 MPa ultimate tensile strength, 22.5 % elongation, and 42.5 J impact energy at bonding line.

Skłonność do tworzenia pęknięć zimnych złączy ze stali ferrytyczno-austenitycznej typu dupleks 2205 przy spawaniu pod wodą metodą mokrą

Skłonność do tworzenia pęknięć zimnych złączy ze stali ferrytyczno-austenitycznej typu dupleks 2205 przy spawaniu pod wodą metodą mokrą

State of the art and trends in development of underwater welding

State of the art and trends in development of underwater welding