Mechanical and Microstructural Properties of Submerged Arc Weldments with High Heat Input

Abstract

The objective of the current work is to present a study of the mechanical and microstructural properties of welded joints of carbon steel obtained from automatic submerged arc welding process with high welding energy, in order to improve productivity on the fabrication of pipes for mooring equipment. Joints of 25mm-thick ASTM A-572 Gr.50 steel were welded by a single pass of submerged arc welding process, with heat input varying from 7.8 to 14.0kJ/mm. The welded joints were evaluated through Charpy-V impact test performed at 0°C temperature, hardness test with 1 kgf load and metallographic examination, performed on samples removed from weld metal and heat affected zone (HAZ). The results showed that the welded joints presented impact toughness higher than the minimum requirements for the welding of low-alloy C-Mn steel with impact toughness requirement of 34 Joules at 0°C. A significant increase on productivity was observed, without prejudice to the mechanical properties, allowing the fabrication of pipes for oil equipment with significant reduction of production time.

Keywords:  Mechanical properties; Microstructure; Heat input