INVESTIGATION OF THE EFFECT OF SMAW PARAMETERS ON PROPERTIES OF AH36 JOINTS AND THE CHEMICAL COMPOSITION OF SEAWATER

Abstract

Underwater wet welding (UWW) is a critical technique for repairing offshore structures, underwater pipelines, water transport infrastructure, docks, and harbor equipment. In this study, the mechanical and microstructural properties of AH36 low-carbon steel weldments were investigated using metal arc welding (SMAW), an underwater wet welding method, at various welding current strengths and seawater temperatures. The relationship between changes in seawater temperature and welding current parameters and their impact on seasonal variations in welding conditions and seawater composition was examined. In the first stage, the yield strength of AH36 was statistically modeled using a central composite design with input parameters of seawater temperature (ranging from 9.7 °C to 25.3 °C) and weld current value (ranging from 49A to 90A). Optimal conditions were determined, resulting in a yield strength of 270MPa, achieved at a seawater temperature of 17.5 °C and a weld current value of 69.5 A. In the second stage, data from optimization studies were utilized to develop elemental exchange equations for Cr (R2=87.3), Ni (R2=64.45), and Mn (R2=65.74) ions in seawater. The findings reveal that weld current intensity primarily influences changes in Cr content in seawater, seawater temperature is correlated with Ni content, and both current intensity and seawater temperature affect the Mn content. The analytical techniques employed include Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for seawater ion analysis, Energy Dispersive Spectroscopy (EDS) point analysis to determine the chemical composition of AH36, and Scanning Electron Microscopy (SEM) for microstructural analysis.