Abstract
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.
Highlights
Indonesia is a maritime country with water territory that has a lot of potential in the industrial sector, food production, mineral mining, pharmaceuticals, maritime service development, and tourism [1]
The material used in this experiment is ASTM A36 low-carbon steel with dimensions of 300 mm × 400 mm × 4 mm, which was cleaned on the surface using grit 150 sandpaper before welding
The deepest penetration is in underwater welding with non-uniform flow without baffle, with an average of 2.28 mm
Summary
Indonesia is a maritime country with water territory that has a lot of potential in the industrial sector, food production, mineral mining, pharmaceuticals, maritime service development, and tourism [1]. This potential arises from the fact that Indonesia has territorial waters with an area of 284,210.90 km and waters of the Exclusive Economic Zone (ZEE) with an area of 2,981,211.00 km and is supported by abundant marine resources [2]. Underwater welding technology allows repairs to be carried out directly without moving the water construction onto land, which is less time consuming and more cost efficient [4,5]. The wet welding process that is conducted directly in the water would affect the welding arc, the weld’s droplet transition, and the heating and cooling cycle due to the water environment, such as water flow rate and water pressure
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