Resistance Spot Welding of Additively Manufactured Maraging Steels—Part I: Nugget Formation

Abstract

Application of additively manufactured steels is unavoidably involved in the resistance spot welding with conventionally manufactured steels. However, the microstructural evolution of an additive manufactured steel at high temperatures is still unknown, especially for the rapid solidification process. This paper investigated the microstructural evolution of a selective laser melted maraging steel during the rapid solidification process via resistance spot welding. Asymmetrical fusion zone with boat shape was found in the spot weld due to the rougher surface and larger electrical resistance of maraging steel via selective laser melting process. The rapid expansion of fusion zone at end of welding process was caused by the carbide formation at the heat-affected zone of maraging steel via selective laser melting process. Besides, printing orientation affected the surface roughness of a selective laser melted maraging steel and subsequently significantly influence the early stage of formation of fusion zone of additively manufactured maraging steel. We expect that our findings will pave the way to the future application of additively manufactured steels in the industries.

Fatigue properties of resistance spot‐welded maraging steel produced by selective laser melting

“…The welding parameters were selected based on prior research conducted by the authors on the welding process for MS1-to-MS1 and MS1-to-DP600 spot welds. 11 A consistent set of welding parameters (as shown in Table 4) was employed for all six test sets detailed in Table 3. During the spot-welding procedure, direct water cooling was implemented on the electrodes with a cooling water intake temperature of 20 C and a cooling water flow rate of 4 L/min.…”

“…CuCrZr alloy electrode caps with a face diameter of 8 mm and dimensions specified in ISO5821 were utilized in the process. The welding parameters were selected based on prior research conducted by the authors on the welding process for MS1‐to‐MS1 and MS1‐to‐DP600 spot welds 11 . A consistent set of welding parameters (as shown in Table 4) was employed for all six test sets detailed in Table 3.…”

“…It is a good candidate for tooling and manufacturing of prototype parts as selective laser melting is applicable to this material. The utilization of SLMed MS1 parts in the automotive industry as a potential replacement for advanced high‐strength steels has been widely explored due to the benefits it offers in terms of strength and weldability 11 . Dual‐phase steels have been utilized extensively in the automotive and truck construction sector since the early 1990s due to their high mechanical strength levels ranging from 600 to 1200 MPa and exceptional shaping and stamping qualities 12 .…”

“…Therefore, it is crucial to investigate the effects of printing orientation on the microstructure and mechanical properties of spot welds for SLMed MS1 parts, particularly when welded to conventionally produced steel to form dissimilar spot welds, such as the MS1 to DP600 spot weld. In our previous work, 11,18 we studied the weld nugget formation mechanism in MS1 RSWs with sheets of varying printing orientation, which revealed that the different material properties of maraging steels affect the fracture displacement in the tensile force-displacement curve of spot welds. Furthermore, the effect of printing orientation on the fracture mode and strength of MS1 RSWs were investigated, and results demonstrated that the printing orientation has no significant impact on the fracture mode and strength of spot welds.…”

“…The utilization of SLMed MS1 parts in the automotive industry as a potential replacement for advanced high-strength steels has been widely explored due to the benefits it offers in terms of strength and weldability. 11 Dual-phase steels have been utilized extensively in the automotive and truck construction sector since the early 1990s due to their high mechanical strength levels ranging from 600 to 1200 MPa and exceptional shaping and stamping qualities. 12 Resistance spot welding (RSW) has been adopted widely in automotive body applications to join similar 13 and dissimilar metals 14 without incurring additional capital costs.…”