Microstructural Characterization of Submerged-arc and Gas-Metal-arc Weldments in HY-130 Steel

Abstract

The microstructure of two HY-130 steel weldments prepared by submerged-arc welding (SAW) and gas-metal-arc welding (GMAW) processes using identical filler wires were investigated. Light and electron microscopy along with microhardness traverses were used to characterize and compare the microconstituents present in the base metal, weld metal, and heat affected zone (HAZ) of both weldments. The base metal consisted of a bainite-martensite microstructure and was uniform through the plate thickness. The weld metal and HAZ structures consisted of a mixture of lath and twinned martensite, bainite, autotempered martensite, and retained austenite. The GMAW weld metal exhibited a finer lath martensite with more interlath retained austenite and transformation microtwins. The SAW weld metal structure was more bainitic and contained higher inclusion densities as a result of the flux used to make the joint. Microhardness traverses exhibited higher hardness values in the GMAW weld metal compared to the SAW. The HAZ microhardness followed a similar trend for both weldments and showed a maximum value in the fine-grained region near the base metal. © 1995, The Iron and Steel Institute of Japan. All rights reserved.