Microhardness and Microstructure of Fiber Laser Welded S960 and S700 Steels

Year 2019, Volume: 3 Issue: 1, 15 - 21, 26.08.2019

Zülküf Balalan , Ömer Ekinci

Abstract

In this study, keyhole laser bead
on plate welding of 6 mm thick high strength low alloy (HSLA) of S960 steels
and keyhole laser butt welding of 13 mm thick (HSLA) of S700 steels were performed
by using 16 kW fiber laser. For different welding parameters of S960 and S700
steels, microhardness and microstructure on the fusion zone, heat affected zone
and base material were determined. Furthermore, X-Ray Diffraction (XRD)
patterns of the welded zone was revealed. In laser bead on plate welding joints
of S960 steels, microhardness of fusion zone (FZ) is approximately 60 HV higher
than base material for all the welding specimens while in laser butt welded
joints of S700 steel, microhardness of FZ is approximately 30 HV. On the other
hand, microstructures of FZ consists of martensite phases, whereas both base
material S960 and S700 consist of tempered martensite and strip-like
martensite.

Keywords

laser welding, microhardness, microstructure, S960

References

• Esfahani MRN, Coupland J, Marimuthu S, 2015. Numerical simulation of alloy composition in dissimilar laser welding, J. Mater. Process. Technol. 224, 135–142.
• Guo W, Crowther D, Francis JA, Thompson A, Liu Z, Li L, 2015. Microstructure and mechanical properties of laser welded S960 high strength steel, Materials and Design 85, 534–548. Ghosh M, Kumar K, Mishra RS, 2010. Analysis of microstructural evolution during friction stir welding of ultrahigh-strength steel, Scr. Mater. 63, 851–854. Hao K, Li G, Gao M, Zeng X, 2015. Weld formation mechanism of fiber laser oscillating welding of austenitic stainless steel, J. Mater. Process. Technol. 225, 77–83. Lan L, Qiu C, Zhao D, Gao X, Du L, 2012. Analysis of microstructural variation and mechanical behaviors in submerged arc welded joint of high strength low carbon bainitic steel, Mater. Sci. Eng. A 558, 592–601.
• Lee BS, Kim MC, Yoon JH, Hong JH, 2010. Characterization of high strength and high toughness Ni–Mo–Cr low alloy steels for nuclear application, Int. J. Press. Vessel. Pip. 87, 74–80.
• Oñoro J, Ranninger C, 1997. Fatigue behaviour of laser welds of high-strength low-alloy steels, J. Mater. Process. Technol. 68, 68–70.
• Poorhaydari K, Patchett BM, Ivey DG, 2005. Estimation of cooling rate in the welding of plates with intermediate thickness, Weld. J. 84, 149–155. Shi Y, Han Z, 2008. Effect of weld thermal cycle on microstructure and fracture toughness of simulated heat-affected zone for a 800 MPa grade high strength low alloy steel, Journal of Materials Processing Technology.207:30-9.
• Takasawa K, Ikeda R, Ishikawa N, Ishigaki R, 2012. Effects of grain size and dislocation density on the susceptibility to high-pressure hydrogen environment embrittlement of high-strength low-alloy steels, International Journal of Hydrogen Energy.37:2669-75.
• Tash MM, Gadelmola KM, 2016. Effect of welding speed on the micro-hardness and corrosion resistance of similar laser welded (304 304) stainless steels and dissimilar (304 A36) stainless and carbon steels, Advanced Materials and Structural Engineering, ISBN 978-1, 138-02786-2. Viano DM, Ahmed NU, Schumann GO, 2000. Influence of heat input and travel speed on microstructure and mechanical properties of double tandem submerged arc high strength low alloy steel weldments, Sci. Technol. Weld. Join. 5, 26–34.
• Yan W, Zhu L, Sha W, Shan Y, Yang K, 2009. Change of tensile behavior of a high-strength low-alloy steel with tempering temperature, Mater. Sci. Eng. A 517, 369–374.
• Zhang C, Lu P, Hu X, Song X, 2012. Effect of buffer layer and notch location on fatigue behavior in welded high-strength low-alloy, J. Mater. Process. Technol. 212, 2091–2101.