Mechanical performance and microstructural characteristic of gas metal arc welded A606 weathering steel joints

Abstract

This investigation aims to make clear the relationships among geometric features, macrostructures, microstructures, and mechanical performances of the weld bead in the gas metal arc welding (GMAW) process for ASTM A606 type IV weathering steel. The results indicate that with the increase of welding heat input, the geometry of the top reinforcement and penetration increases proportionally until reaching the peak value, and then declines with the further increase of welding heat input; while the values of bottom reinforcement increase continuously with the increase of welding heat input. The average ultimate tensile strength (F), maximum displacement (L), and failure energy (E) of the welded joint produced by the moderate welding heat input are 10.27 kN, 1.88 mm, and 13.55 J, respectively, which are obviously larger than those obtained by the insufficient welding heat input (F: 8.33 kN, L: 1.20 mm, and E: 7.10 J). Although the mechanical properties of the welds achieved by the overlarge welding heat inputs present comparable levels (F: 9.73 kN, L: 1.86 mm, and E: 13.51 J), their standard deviation is much higher. Acicular ferrite, grain boundary ferrite, side plate ferrite, Widmanstätten ferrite, and pearlite are noticed in the fusion zone (FZ), while the coarse grain heat-affected zone (CGHAZ) is composed of upper and lower bainite, grain boundary ferrite, Widmanstӓtten ferrite, polygonal ferrite, and pearlite. As the welding heat input increases, the pre-austenite grain width in the FZ and CGHAZ decreases. The descending order of the microhardness distributed in the welded joints is fusion line, CGHAZ, FZ, fine grain heat-affected zone (FGHAZ), and base metal. In addition, the microhardness values of FZ and CGHAZ decline with the rise of the welding heat input. Nonetheless, no apparent links are found between the microhardness levels of the FGHAZ and welding heat input.

Correlating Electrode Degradation with Weldability of Galvanized BH 220 Steel during Electrode Failure Process of Resistance Spot Welding

“…Figure 4 indicates that the CGHAZ is packed with coarse martensite, grain-boundary ferrite, and Widmanstatten ferrite. The maximum temperature of CGHAZ is within the limit of Ac3 (866 °C) [28] and the melting point of the BM (about 1500 °C). Therefore, complete austenitizing occurs.…”

Evolutions of Microstructure and Impact Toughness of Submerged Arc Weld Metal via Introducing Varied Si for Weathering Bridge Steel

“…In particular, the SAW with high cladding efficiency is preferred in the welding of medium and thick plates [4][5][6]. It is widely required in engineering that the corrosion resistance and strength of the WMs should match with the base metal, and alloying elements, such as Cu, Cr, and Ni, are also commonly added to the weld [7,8]. However, abundant alloying elements cause a poor weld ability of weathering steel, and gas holes and a large number of inclusions are often found in welds, and contain a high proportion of granular bainitic ferrite (GBF) and coarse hard-phase martensite/austenite (M/A) constituents, which cause serious damage to the metallurgical quality and impact performance of WMs [9][10][11].…”