Microstructure Evolution and Mechanical Properties of Underwater Dry Welded Metal of High Strength Steel Q690E Under Different Water Depths

Abstract

Q690E high strength low alloy (HSLA) steel has been intensively applied in maritime engineering. Also, the underwater dry welding (UDW) technique has been widely used to repair important offshore facilities. In this paper, joints of Q690E steel were fabricated through single-pass underwater dry welding at three pressures (0, 0.2, and 0.4 MPa). To study the effect of the pressure on the microstructure and mechanical properties of the UDW joint, an optical microscope (OM) and scanning electron microscope (SEM) were used to observe the microstructure and fracture morphology of the welded joints. The electron backscattered diffraction (EBSD) technique was used to analyse the crystallographic features and the crystallographic grain size of the ferrites. The proportion of acicular ferrite (AF) in the UDW joints and the density of low-angle boundaries increase dramatically with the increasing depth of water. The weld metal of UDW-40 shows higher strength because more fine ferrites and low-angle boundaries within UDW-40 impede the dislocation movement.

Weldability of Underwater Wet-Welded HSLA Steel: Effects of Electrode Hydrophobic Coatings

“…There are three different methods of underwater welding. The first is dry welding, in which the welder and the process area are isolated from the surrounding water by special chambers [7,8]. The second method is local cavity welding, whereby the welding area and welding arc are located in a small chamber without water, however the welder-diver is located in the aqueous environment [9].…”

Bead-on-Plate Underwater Wet Welding on S700MC Steel

“…Three main groups of underwater welding methods are distinguished: dry welding, local cavity welding and wet welding. Dry welding is carried out in special chambers, which isolate welder and all welding area from environment [9]. The cost of designing and making such chambers is very high, but the quality of the joints is similar to those made in air environment.…”

Investigation of Process Stability and Weld Quality of Underwater Wet Flux-Cored Arc Welding of Low-Alloy High-Strength Steel with Oxy-Rutile Wire

“…It was recognised that underwater dry welding required a hyperbaric chamber with large support equipment. The estimated cost and time for dry welded repairs are twice those for wet welded repairs [36,37]. Therefore, the underwater wet welding process in the present study is more versatile and cost-effective than that of underwater dry welding.…”