Groove configurations of a flux-cored arc welding process used in critical structures of precision mechanical presses—mechanical and metallurgical studies

Abstract

This paper utilized a flux-cored arc welding (FCAW) technique and investigated various groove configurations as well as multi-pass welding sequences to create welding specifications in the precision mechanical press industry. Experimental investigations were conducted to examine the influence of three different groove configurations of 40-mm-thick JIS SS400 structural steel welded joints on mechanical and metallurgical properties. Mechanical properties of the welded joints were evaluated by uniaxial tensile testing and Charpy V-notch (CVN) impact testing at room temperature. Simultaneously after a multi-pass welding sequence, various degrees of thermal treatments such as tempering or normalization inevitably occur in the heat-affected zone (HAZ). The unfavorable microstructures in the HAZ and reheated zones can be intentionally modified via the above procedure such that the toughness and microhardness of the HAZ improve. The experimental results revealed that of the three types of groove configurations (C1, C, and F), groove type C1 possessed the maximum yield strength (YS) and ultimate tensile strength (UTS) while groove type F possessed the highest CVN values tested at room temperature. The fundamental reason may be attributed to heat dissipation characteristics of each groove configuration and associated exertion of the multi-pass welding sequence. Microstructural and morphological features as revealed through an optical microscope also indicate a significant influential factor of these joints among the different groove configurations. Therefore, grain refinement of varying degrees can be obtained due to the variation of thermal characteristics of heat input/dissipation; thus, various mechanical and CVN impact properties can be obtained.