Microstructure Changes related Mechanical Properties of Welded HSLA Steel Plates

Abstract

Strength and toughness of steel are the most desirable mechanical properties required in several engineering applications such as marine and oil industries. In this work, the influence of submerged arc welding (SAW) process on the evolution of microstructure and mechanical properties of locally produced low carbon steel plates that is used by Marine Industry and Maintenance Company (Misurata) as an alternative to the imported marine steel plates is investigated. Microstructure investigation, tensile tests, impact toughness, and hardness tests for both steels are conducted. Results show that microstructure is affected by the heat input of SAW leading to more uniform structure of ferritic-bainitic and finer grain sizes. Inherently, affecting the mechanical properties since a decrease in toughness in the heat affected zone HAZ and weld metal zone WM compared to the parent metal is observed. It is shown that the imported steel has higher toughness than local steel for pre-welded and welded plates, with imported steel offering significant reduction in toughness when subject to welding. The effect of welding can be related to the microstructural changes of the weld metal and HAZ attained by adapting proper consumable electrode and welding process strategies.