Underwater Welding Technology Research Articles

Investigation of Microstructure, Oxides, Cracks, and Mechanical Properties of Ti-4Al-2V Joints Prepared Using Underwater Wet Laser Welding.

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys.

Performance Evaluation of Underwater (UW) Welding System with Friction Stir Welding (FSW) Method on 316L Stainless Steel Exposed to Sea Water

Friction Stir Welding (FSW) is a solid-state welding technique that can produce high-quality joints without defects that commonly occur in liquid welding. However, FSW has limitations in underwater applications due to the friction between the tool and the material that causes a decrease in heat efficiency and shear force. To overcome this problem, this study proposes an underwater welding (UW) system with the FSW method on 316L stainless steel exposed to seawater. This UW-FSW system uses a high-speed rotating tool surrounded by an inert gas shroud to prevent direct contact between the tool and seawater. The aim of this study is to evaluate the performance of this UW-FSW system in terms of mechanical properties, microstructure, and corrosion resistance of 316L stainless steel joints. The results of this study show that the UW-FSW system can produce joints with better tensile strength, hardness, and corrosion resistance than conventional FSW. This is due to the rapid cooling, reduction of oxidation, and formation of a thicker passive layer on the joint surface. This study provides a contribution to the development of environmentally friendly and efficient underwater welding technology.

Organic adhesive assisted underwater submerged-arc welding

Abstract Underwater welding technology has become indispensable to the construction, maintenance, and repair of many offshore structures in oceanographic engineering industry. However, the existing disadvantages of current underwater welding technologies make them be unpopular and limited. An innovative organic adhesive assisted underwater submerge-arc welding was proposed to avoid the water disturbances to the maximum extent in wet condition. The mixture composed of bisphenol-A epoxy resin (EP) and welding flux in a weight ratio of 4:6 was placed on the metal surface before welding. Welding arc totally submerged in the mixture and maintained stable burning between the wire and base metal. The coverage effectively isolated the serious direct disturbances from surrounding water and greatly reduced the cooling rate of the welded joints to 19.57 °C/s. High-performance and defect-free welded joints were achieved with fine microstructures. The average tensile strength and maximum bending angle of the welded joints obtained by underwater submerged arc welding reached 463 MPA and 180°, respectively. Especially, low temperature impact toughness still keep 63 J/cm2 in 0 °C, which means far better mechanical properties compared with underwater wet welding. For the wet condition, this provides a possibility to acquire high-quality underwater welded joints comparable to that in air.

Current Status and Prospects of Underwater Welding Technology for Key Sensitive Equipment in Nuclear Power Plants

This paper analyzes the application status of underwater welding technology in nuclear power plant welding repair. Take the local dry-method underwater welding 304 austenitic stainless steel butt weld as an example. It points out the gap between the mechanical properties and corrosion resistance of underwater welded joints and the welded joints in the air. In order to adapt to the underwater welding environment with high radioactivity and high risk environment in the future, the development of local dry underwater welding automation system will be the key to underwater welding repair of key sensitive components of nuclear power plants in the future.

A novel underwater submerged-arc welding acquires sound quality joints for high strength marine steel

The serious interferences from the surrounding water severely limit the process stability and joint quality of the current underwater welding technologies. To effectively isolate the welding area, a mixture of epoxy resin and submerged-arc flux was innovatively prepositioned in the welding area during underwater welding process. Butt welding experiments of a typical high strength marine steel were conducted to verify the advantages of this technique. Compared with the traditional underwater wet welding, underwater submerged-arc welding significantly optimized the arc burning environment due to the covering and isolation, which effectively improved the stability of welding process. Defectless joints with microstructure that full of fine acicular ferrite and high-quality mechanical properties, especially, outstanding performance of ultimate strength and plasticity were obtained. The results are expected to positively widen the practical application of underwater welding in many water related industries.

Study on Remote Control Underwater Welding Technology Applied in Nuclear Power Station

At present, the work of welding repair for nuclear power station is carried out by the driving welder and the quality is difficult to be ensure. The technology of remote control underwater local dry welding is the development current. So, a suit of remote control underwater local dry automatic welding system for metal inert-gas welding has been developed. It‘s key component is a pressure vessel, which can simulate the 30 meter water depth environment. There are three cameras in the welding cabin which can monitor the run state of equipment and welding process. The results of 15 meter water depth welding experiment for 304 and 321 stainless steel show that, the system can satisfy requirements of local dry welding test. These research productions have the vital significance for the development of nuclear power station underwater welding repair technology.

水中溶接における冷却過程の評価

Underwater welding technologies are of growing importance with increasing of waterfront projects. Underwater welding technique also provides effective means for repairing many kinds of offshore structures. It should be pointed out, however, that such important properties as the cooling cycle and the joint strength in the underwater welding are not fully understood. In the previous studies, cooling cycle of underwater welding conducted in the water at rest was investigated. From a site welding point of view, it is necessary to elucidate how a tidal current and a wave affect the welding operations and the strength of welded joint.In this paper, underwater welding is performed in the running water, and the effects of water flow velocity on the cooling process are studied. The experiments are conducted in a water tank especially designed for this purpose, where the flow velocity is varied up to 30cm/sec. Accordingly, significant characteristics of the cooling curves and cooling rates are estimated.

水中溶接技術の現状

水中溶接技術の現状

水中溶接の現状

水中溶接の現状