A pathway to produce strong and tough martensitic stainless steels resistance spot welds

Abstract

Martensitic stainless steel (MSS) resistance spot welds are prone to quasi-cleavage interfacial failure with very low energy absorption capability due to formation of hard and brittle carbon and chromium rich martensite in the fusion zone (FZ). In this work, a new pathway is proposed to enhance strength/toughness of the MSS resistance spot welds based on modification of the FZ composition/microstructure via introducing a nickel interlayer. This altered the FZ microstructure from dual phase microstructure of martensite and δ-ferrite to austenitic microstructure with finely dispersed ultra-fine chromium rich carbides. Formation of a tough predominately austenitic microstructure in the FZ enabled achieving a pullout failure with an unprecedented level of energy absorption.

Influences of Quenching Temperature on the Microstructure Evolution and Strength−Toughness of a Novel Medium‐Carbon Ti−Mo‐Bearing Martensite Steel

“…[24,28,29] However, the maximum impact energy of other reported high-strength steels was much smaller than the cryogenic impact energy of the as-developed martensite steel. In addition, it is noticeable that most traditional high-strength steels manifest excellent mechanical properties; however, they consume a lot of costly alloys such as Ni, Co, Cr, etc.. [14,15,19,22,23] The increased alloying element content in high-strength steels results in an inevitable production cost. Moreover, the smelting process becomes more complicated and changeable in these high-strength steels, which is disadvantageous to their large-scale production and applications.…”

“…[8][9][10][11][12][13][14] Especially, martensite steels are found to be promising due to their very high strength; however, the unsatisfactory toughness limits their commercial applications. [15,16] To improve the properties of martensite steels, secondary-hardening martensite steel, maraging steel, medium-carbon low-alloy martensite steel, and bainite/martensite duplex-phase high-strength steels have been successively proposed. [17][18][19][20][21][22][23][24] Kown et al [17] prepared a new type of secondary-hardening martensite steel (0.24CÀ3.13WÀ3.07CrÀ14.18CoÀ9.83Ni) with a hardness of 55 HRC and room-temperature impact energy of <30 J. Mooney et al [18] and Casalino et al [19] both developed maraging steels with different Ti additions.…”

Prediction of the Shear Tension Strength of Resistance Spot Welded Thin Steel Sheets from High- to Ultrahigh Strength Range

“…For example, Fig. 1 STS values of RSWed high-to ultra-high strength steels in similar [18, and dissimilar [12,23,25,36,38,43,50,78,79,82,87,96,98,100,101,115,119,125, joint configurations for the welding of a R m = 1500 MPa steel the same STS is required for the joint as for a R m = 1200 MPa steel grade (see also in Figs. 2 and 3).…”

Effects of Cover Sheets on the Nugget Growth and Fracture Behavior of Resistance Spot Welded Q&P980 Steel Joints

“…The third one is to modify the microstructure of the nugget by introducing an interlayer. Aghajani and Pouranvari [13] introduced a nickel interlayer to weld martensitic stainless steel, the interlayer altered the nugget microstructure from dual phase microstructure of martensite and δ-ferrite to austenitic microstructure, which helped the joints achieve pull-out fracture mode and higher energy absorption. The last one is to introduce a cover sheet between the electrode and the sheet to be welded, the method was frequently applied to weld nonferrous metals such as Mg [14], or dissimilar RSW such as Al/steel [15], but was hardly reported in the RSW of steels.…”