Effect of GTAW on the Tensile Strength and Hardness of Mild Steel

Abstract

Gas tungsten metal arc welding (GTAW) is used to study the effect of the base metal thickness, welding current and welding speed on the tensile strength and hardness of mild steel welding. The analysis found that base metal thickness had the highest effect and highest means of tensile strength and hardness of the welding. Taguchi’s design (TD) suggested using higher base metal thickness, lower welding current and higher welding speed when welding mild steel in order to obtain maximum tensile strength and hardness. The welding that has higher tensile strength showed higher hardness. However, the hardness increased proportionally with the increased internal stresses of the welding. The welding showed wider heat affected zone (HAZ) with the increase in internal stresses of the welding.

Study the Influence of Welding Parameters by Taguchi’s Design on the Mechanical Properties of Welded Mild Steel (S235jr)

“…The internal stresses have been reported to cause decreased hardness [34]. The decreased hardness was reported to result in lower transverse tensile strength [19,20,21]. This because the decreased hardness promotes ductility and thus decreased welding tensile strength.…”

“…The relationship between tensile strength and hardness was reported before [19,20,21]. Calderón et al (2021) concluded that the tensile strength and hardness of FZ and HAZ were also studied because they affect the mechanical properties of welding due to the different properties of the welding and adjacent regions [22].…”

“…In comparison on the transverse tensile strength between the mild steel welding and the base metal. The welding was found to have lower tensile strength, although it has higher hardness [19,20,21]. Other studies reported that the welded joint has higher tensile strength than base metal but lower toughness [18,25].…”

“…Researchers have studied the effect of welding parameters according to Taguchi's design on the mild steel welding tensile strength and hardness [14,15,16,17,18,19,20,21]. For instance, in the study on welding penetration depth, Ogbonna et al (2023) found that welding voltage has the highest influence on the tensile strength of AISI 1008 mild steel heterogeneous welding over welding current and gas flow rate [14]; Om Prakash et al (2019) found that welding WFS had a higher effect on the tensile strength of AISI 11040 steel welding over the welding voltage and welding speed [15]; and Assefa et al…”

“…Another study by Khan et al (2020) found that welding current has a higher influence on EN8 mild steel with dissimilar welding hardness [17]; Khamari et al (2019) stated that a higher current contributed to a higher welding tensile strength [18]. Previous similar studies concluded that tensile strength increased with decreasing welding voltage, welding current, and WFS [19,20,21]. The groove shape was also reported to affect the mechanical properties of welding, where V-shaped welding obtained higher tensile strength and hardness than double V-shaped welding [20].…”