Study of pores produced in underwater wet welding

This paper deals with the effect of water depth in the range of 10 m to 80 m upon the formation of pores produced during underwater wet welding. The results show that it is easy for the inner pores to occur owing to the particularity of the molten metal solidification that the outer pores begin to appear when the water depth increases to about 60 m, that the porosity increases and pore grows up as the water depth increases, and that pores are all hydrogen-containing ones through the examination of the variation of number of pores with the residual hydrogen and oxygen content in the weld metal.

Effects of process parameters on the depth-to-width ratio of flux-cored wire underwater wet welding

The effects of process parameters on the depth-to-width ratio （D/W） of flux-cored wire underwater wet welding with a certain type of homemade .flux-cored wire are studied. It is found that the welding .speed, wire feeding speed and torch oscillating amplitude hare significant effects on the dopth-to-width ratio （D/W） of welds. The D/W ratio of welds increases significantly with the increase of welding speed without the oscillating of welding torch. It increased （from 0. 14 to 0. 26 ） with the increase of wire feeding speed while the torch oscillating. And it decreased linearly with the increase of torch oscillating amplitude. However, the influelwe of oscillating speed, wire extension and welding voltage on the D/W ratio of welds was not obvious.

Development of underwater wet welding experimental and divers training system

Compared to traditional welding methods, the underwater wet welding is special with many different characteristics due to the unique aqueous environment. It is conducted completely under water by divers and unique welding technology is required in the special operation environment. The operating levels of the divers are the key factor to acquire high quality welded joints. In this paper, an underwater wet welding experimental and divers training system is developed to serve divers training and conducting welding experiments. The system consists of life support system, signals real-time monitoring system and communicating system, etc. An underwater butt welding experiment based on welding electrodes is conducted, and the system works well. It proves that the system can guarantee divers welding safely and successfully and high quality weld seam is expected to be acquired.

Analysis of the electrical conductivity of plasma during underwater wet welding

The electrical conductivity is indispensable for the underwater wet welding arc simulation. In order to get this parameter, the composition of the underwater arc is analyzed, and the electron content is obtained. Then the current formation mechanism in the arc and the effective collision cross-sectional area between the electron and ions is discussed. The calculation methods and results analysis are presented in this paper.

Finite element analysis of the angular distortion and residual stress in underwater wet welding

In underwater environment, the shape, voltage, and energy density of the welding arc vary because of the high pressure and there are notable changes in workpiece cooling conditions due to the strong cooling effect of water. As a result, there are clear differences between the residual stress and thermal distortion in underwater wet welding and those in conventional welding （in air）. Considering these process features, a thermo-mechanical finite element model of underwater wet bead-on-plate welding was established. The influences of the water compressing action to the arc and the enhanced heat losses caused by the surrounding water on the residual stress and the angular distortion of the workpiece were analyzed. Results show that the angular distortion gets smaller in deeper water, and that the longitudinal residual stress gets smaller as water flows faster.

Underwater Wet Welding for HSLA Steels: Chemical Composition, Defects, Microstructures, and Mechanical Properties

The effect of water depth on underwater wet welds was investigated by underwater wet shielded metal-arc welding technique. The microstructures, chemical composition, welding defects, and mechanical properties were studied. The contents of alloying elements decrease, while the oxygen content increases with water depth. Within 55 m depth, the carbon monoxide reaction is controlling the oxygen content which will further control the contents of alloying elements. The columnar microstructures in weld metal obtained at shallow water consist of grain boundary ferrite, side-plate ferrite, and acicular ferrite, while those at depth greater than 11 m exhibit more proeutectoid ferrite due to the loss of alloying elements. Mechanical properties are a strong function of depth owing to the increase in oxidation of alloying elements and porosity. Welds obtained within 11 m show preferable strength, ductility, and toughness. The mechanical properties significantly drop from 11 to 25 m because of the increased porosity and oxidation of alloying elements.

Research on porosity of underwater wet FCAW duplex stainless steel

To study the influence laws of welding parameters on weld porosity, underwater wet flux-cored arc welding （ FCAW） duplex stainless steel S32101 was carried out in a hyperbaric chamber, and the second-order multiple regression equation was established. The interactive effects of welding parameters on the porosity were analyzed by the three dimensional response surfaces and the contour plots. The results present that the interaction effect between water depth and voltage on the porosity is the most significant. Theoretically, a non-pores weld bead can be gained by reasonably matching these parameters with water depth less than 10 m. Always, the weld porosity reaches its peak value with a 7 mm/s welding speed.