Research Papers

Fiber Laser Welding of Direct-Quenched Ultrahigh Strength Steels: Evaluation of Hardness, Tensile Strength, and Toughness Properties at Subzero Temperatures

[+] Author and Article Information
Farhang Farrokhi

Department of Mechanical and
Manufacturing Engineering,
Aalborg University,
Aalborg East DK-9220, Denmark
e-mail: ffk@m-tech.aau.dk

Jukka Siltanen

SSAB Europe Oy.,
Hämeenlinna FI-13300, Finland
e-mail: jukka.siltanen@ruukki.com

Antti Salminen

Department of Mechanical Engineering,
Lappeenranta University of Technology,
Lappeenranta FI-53851, Finland
e-mail: antti.salminen@lut.fi

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received November 16, 2014; final manuscript received March 19, 2015; published online September 9, 2015. Assoc. Editor: Hongqiang Chen.

J. Manuf. Sci. Eng 137(6), 061012 (Sep 09, 2015) (10 pages) Paper No: MANU-14-1603; doi: 10.1115/1.4030177 History: Received November 16, 2014

The recently developed direct-quenched ultrahigh strength steels (UHSS) possess an appropriate combination of high tensile strength and toughness properties at subzero temperatures down to −80 °C, while simultaneously having low carbon contents, which is beneficial for weldability. In this study, butt joints of Optim 960 QC direct-quenched UHSS with a thickness of 8 mm were welded with a 10 kW fiber laser to evaluate the characteristics of the joints within the range of low to high heat inputs possible for this welding process. The mechanical properties of the joints were studied by subjecting the specimens to a number of destructive tests, namely, hardness and tensile testing, as well as impact toughness testing at temperatures of −40 °C and −60 °C. It was found that high quality butt joints with superior tensile strength and good impact toughness properties at −40 °C could be obtained. However, having a high level of all these properties in the joint narrows the process parameters’ window, and the heat input needs to be strictly controlled.

Copyright © 2015 by ASME
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Horii, Y. , Ohkita, S. , Shinada, K. , and Koyama, K. , 1995, “Development of High-Performance Welding Technology for Steel Plates and Pipe for Structural Purposes,” Nippon Steel, Report No. 65.
Hemmilä, M. , Hirvi, A. , Kömi, J. , Laitinen, M. , Mikkonen, P. , Porter, D. , Savola, J. , and Tihinen, S. , 2010, Technological Properties of Direct-Quenched Structural Steels With Yield Strength 900-960 MPa as Cut Length and Hollow Sections, Rautaruukki Corporation, Helsinki, Finland.
Quentino, L. , Costa, A. , Miranda, R. , Yapp, D. , Kumar, V. , and Kong, C. J. , 2007, “Welding With High Power Fiber Lasers: A Preliminary Study,” Mater. Des., 28(4), pp. 1231–1237. [CrossRef]
Ion, J. , 2005, Laser Processing of Engineering Materials: Principles, Procedure and Industrial Application, Elsevier Butterworth-Heinemann, Burlington, MA.
Canning, J. , 2006, “Fibre Lasers and Related Technologies,” Opt. Lasers Eng., 44(7), pp. 647–676. [CrossRef]
Salminen, A. , Lehtinen, J. , and Harkko, P. , 2008, “The Effect of Welding Parameters on Keyhole and Melt Pool Behavior During Laser Welding With High Power Fiber Laser,” 27th International Conference on Applications of Lasers and Electro Optics ICALEO2008, Temecula, CA, pp. 354–363.
Shi, S. , and Westgate, S. , 2008, “Laser Welding of Ultra High Strength Steels for Automotive Applications,” PICALO 2008, Beijing.
Kaplan, A. F. H. , Westin, E. M. , Wiklund, G. , and Norman, P. , 2008, “Imaging in Cooperation With Modeling of Selected Defect Mechanisms During Fiber Laser Welding of Stainless Steel,” ICALEO, Temecula, CA, pp. 789–798.
Kawahito, Y. , Kinoshita, K. , Matsumoto, N. , Mizutani, M. , and Katayama, S. , 2008, “Effect of Weakly Ionised Plasma on Penetration of Stainless Steel Weld Produced With Ultra High Power Density Fiber Laser,” Sci. Technol. Weld. Joining, 13(8), pp. 749–753. [CrossRef]
Duley, W. W. , 1999, Laser Welding, Wiley, New York.
Yilbas, B. S. , and Akhtar, S. , 2013, “Laser Welding of AISI 316 Steel: Microstructural and Stress Analysis,” ASME J. Manuf. Sci. Eng., 135(3), p. 031018. [CrossRef]
Losz, J. , and Challenger, K. , 1999, “HAZ Microstructures in HSLA Steel Weldments,” First United States-Japan Symposium on Advances in Welding Metallurgy, Yokohama, Japan, pp. 207–225.
Zeman, M. , 2009, “Assessment of Weldability of WELDOX 1100 High-Strength Quenched and Tempered Steel,” Weld. Int., 23(2), pp. 73–82. [CrossRef]
Xia, M. , Biro, E. , Tian, Z. , and Zhou, Y. , 2008, “Effect of Heat Input and Martensite on HAZ Softening in Laser Welding of Dual Phase Steels,” ISIJ Int. J., 48(6), pp. 809–814. [CrossRef]
Mohandas, T. , Madhusudan Reddy, G. , and Satish Kumar, B. , 1999, “Heat Affected Zone Softening in High Strength Low Alloy Steels,” J. Mater. Process. Technol., 88(1), pp. 284–294. [CrossRef]
Farabi, N. , Chen, D. , and Zhou, Y. , 2011, “Microstructure and Mechanical Properties of Laser Welded Dissimilar DP600/DP980 Dual-Phase Steel Joints,” J. Alloys Compd., 509(3), pp. 982–989. [CrossRef]
Xia, M. , Sreenivasan, N. , Lawson, S. , Zhou, Y. , and Tian, Z. , 2007, “A Comparative Study of Formability of Diode Laser Welded in DP980 and HSLA Steels,” ASME J. Eng. Mater. Technol., 129(3), pp. 446–452. [CrossRef]
Farabi, N. , Chen, D. , and Zhou, Y. , 2010, “Fatigue Properties of Laser Welded Dual-Phase Steel Joints,” Procedia Eng., 2(1), pp. 835–843. [CrossRef]
Biro, E. , McDermid, J. , Embury, J. , and Zhou, Y. , 2010, “Softening Kinetics in the Subcritical Heat-Affected Zone of Dual-Phase Steel Welds,” Metall. Mater. Trans. A, 41(9), pp. 2348–2356. [CrossRef]
Baltazar Hernandez, V. , Nayak, S. , and Zhou, Y. , 2011, “Tempering of Martensite in Dual Phase Steels and Its Effects on Softening Behavior,” Metall. Mater. Trans. A, 42(10), pp. 3115–3129. [CrossRef]
Xu, W. , Westerbaan, D. , Nayak, S. , Chen, D. , Goodwin, F. , and Zhou, Y. , 2012, “Tensile and Fatigue Properties of Fiber Laser Welded High Strength Low Alloy and DP980 Dual-Phase Steel Joints,” Mater. Des., 43, pp. 373–383. [CrossRef]
Xu, W. , Westerbaan, D. , Nayak, S. , Chen, D. , Goodwin, F. , Biro, E. , and Zhou, Y. , 2012, “Microstructure and Fatigue Performance of Single and Multiple Linear Fiber Laser Welded DP980 Dual-Phase Steel,” Mater. Sci. Eng. A, 553, pp. 51–58. [CrossRef]
Kim, C.-H. , Choi, J.-K. , Kang, M.-J. , and Park, Y.-D. , 2010, “A Study on the CO2 Laser Welding Characteristics of High Strength Steel up to 1500 MPa for Automotive Application,” J. Achiev. Mater. Manuf. Eng., 39(1), pp. 79–86.
Sreenivasan, N. , Xia, M. , Lawson, S. , and Zhou, Y. , 2008, “Effect of Laser Welding on Formability of DP980 Steel,” ASME J. Eng. Mater. Technol., 130(4), p. 041004. [CrossRef]
Leiviskä, P. , Fellman, A. , Laitinen, R. , and Vänskä, M. , 2007, “Strength Properties of Laser and Laser Hybrid Welds of Low Alloyed High Strength Steels,” 11th Conference Nordic Laser Materials Processing, Lappeenranta, Finland, pp. 173–184.
Laitinen, R. , Kömi, J. , Keskitalo, M. , and Mäkikangas, J. , 2007, “Improvement of the Strength of Welded Joints in Ultra High Strength Optim 960 QC Using Autogenous Yb:YAG Laser Welding,” Nordic Laser Materials Processing, NOLAMP 11, Lappeenranta, Finland, pp. 204–215.
Siltanen, J. , and Tihinen, S. , 2012, “Position Welding of 960 MPa Ultra-High-Strength-Steel,” ICALEO, Anaheim, CA, pp. 464–473.
Zeman, M. , 2009, “Properties of Welded Joints Made of Weldox 1100 Steel,” Weld. Int., 23(2), pp. 83–90. [CrossRef]
Juan, W. , Li, Y. , and Liu, P. , 2003, “Effect of Weld Heat Input on Toughness and Structure of HAZ of a New Super-High Strength Steel,” Bull. Mater. Sci., 26(3), pp. 301–305. [CrossRef]
Shi, Y. , and 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,” J. Mater. Process. Technol., 207(1), pp. 30–39. [CrossRef]
EN ISO 15614-11, 2002, Specification and Qualification of Welding Procedures for Metallic Materials-Welding Procedure Test-Part 11: Electron and Laser Beam Welding , Finnish Standard Association SFS, Helsinki, Finland, Report No. SFS-EN ISO 15614-11.
Farrokhi, F. , 2014, “Autogenous High Power Fiber Laser Welding of Optim 960 QC Ultra High Strength Steel,” Masters thesis, Lappeenranta University of Technology, Lappeenranta, Finland.
EN ISO 13919-1, 1996, Welding: Electrons and Laser Beam Welded Joints. Guidance on Quality Levels for Imperfections. Part 1: Steel , Finnish Standard Association SFS, Helsinki, Finland, Report No. SFS-EN ISO 13919-1.
ISO 22826, 2005, Destructive Tests on Welds in Metallic Materials-Hardness Testing of Narrow Joints Welded by Laser and Electron Beam (Vickers and Knoop Hardness Tests) .
ISO 15614-1:2004/Amd, 2012, Specification and Qualification of Welding Procedures for Metallic Materials-Welding Procedure Test-Part 1: Arc and Gas Welding of Steels and Arc Welding of Nickel and Nickel Alloys-Amendment 2 , Finnish Standard Association SFS, Helsinki, Finland, SFS-EN ISO 15614-1/A2.
CEN ISO/TR 15608, 2013, Welding: Guidelines for a Metallic Materials Grouping System , Finnish Standard Association SFS, Helsinki, Finland, CEN ISO/TR 15608.
Ruukki Metals Oy., 2013, Welding General: Hot-Rolled Steel Sheets: Plates and Coils, Rautaruukki Corporation, Helsinki, Finland.
Hemmilä, M. , Laitinen, R. , Liimatainen, T. , and Porter, D. , 2005, Mechanical and Technological Properties of Ultra High Strength Optim Steels, Rautaruukki Corporation, Helsinki, Finland.
EN ISO 4136, 2012, Destructive Tests on Welds in Metallic Materials. Transverse Tensile Test , Finnish Standard Association SFS, Helsinki, Finland, SFS-EN ISO 4136.
EN ISO 148-1, 2009, Metallic Materials-Charpy Pendulum Impact Test-Part 1: Test Method , Finnish Standard Association SFS, Helsinki, Finland, SFS-EN ISO 148-1.
Degenkolbe, J. , Uwer, D. , and Wegmann, H. , 1984, “Characterisation of Welding Thermal Cycles With Regard to Their Effect on the Mechanical Properties of Welded Joints by Cooling Times t8/5 and Its Determination,” IIW Document, International Institute of Welding, London.
Sokolov, M. , Salminen, A. , Somonov, V. , and Kaplan, A. F. , 2012, “Laser Welding of Structural Steels: Influence of the Edge Roughness Level,” Opt. Laser Technol., 44(7), pp. 2064–2071. [CrossRef]
Kawahito, Y. , Matsumoto, N. , Abe, Y. , and Katayama, S. , 2013, “Laser Absorption Characteristics in High-Power Fiber Laser Welding of Stainless Steel,” Weld. Int., 27(2), pp. 129–135. [CrossRef]
Panda, S. , Sreenivasan, N. , Kuntz, M. , and Zhou, Y. , 2008, “Numerical Simulations and Experimental Results of Tensile Test Behavior of Laser Butt Welded DP980 Steels,” ASME J. Eng. Mater. Technol., 130(4), p. 041003. [CrossRef]
Marimuthu, S. , Eghlio, R. M. , Pinkerton, A. J. , and Li, L. , 2013, “Coupled Computational Fluid Dynamic and Finite Element Multiphase Modeling of Laser Weld Bead Geometry Formation and Joint Strengths,” ASME J. Manuf. Sci. Eng., 135(1), p. 011004. [CrossRef]


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Fig. 1

Shielding gas and lower cross jet tubes arrangement used in order to protect the weld bead and push the laser induced metal vapor plume away from the laser beam

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Fig. 2

Summary of joint configuration and the prepared edges’ properties. Size of specimens was chosen according to laser welding procedure test EN ISO 15614-11.

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Fig. 3

Top and root concavity (d1 and d2) and average width of weld (wf) measured for each specimen

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Fig. 4

Schematic preview of rows of indentation for hardness measurement according to hardness testing of laser welded joints ISO 22826. BM: base metal.

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Fig. 5

Measurement of the average base metal hardness (hb), average FZ hardness (hf), average minimum hardness in HAZ (hm), and the average width of the soft zone of both sides (w1 and w2) from a schematic average hardness profile

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Fig. 6

Energy absorption at different roughness levels [42]. The vertical dashed line denotes the average edge surface roughness for the current study.

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Fig. 7

The width of weld (wf) increased as the energy input increased

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Fig. 8

Visual comparison of top side (half-length) and cross section of the welds welded with highest and lowest welding speeds

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Fig. 9

Measured concavity in the top and root sides of the macrospecimen of welds. Apart from weld #806, all values were below the specified critical limit for quality level B according to EN ISO 13919-1.

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Fig. 10

Comparison of root sides of the stable fast welds with the unstable slow welds (half-length images)

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Fig. 11

Hardness profile of top side (upper) and root side (lower) of the welds with lowest and highest line energy

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Fig. 12

Soft zone width (ws) and the degree of softening (hb − hm) decreased as the welding speed increased

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Fig. 13

Average hardness in the FZ (hf) with a standard deviation varying between 5 and 10 HV

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Fig. 14

Laser cut softened area overlapping with the narrowest weld (1) and the widest weld (2). Width of laser cut softened area was narrower than the welds.

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Fig. 15

Tensile test results. Linear trend line of the average values predicts the maximum line energy and cooling time before the loss of strength occurs in the joints.

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Fig. 16

Absorbed impact energy at −40 °C of each joint and their corresponding standard deviation (vertical lines). The horizontal dashed line depicts the minimum toughness requirement of 22 J. CL: weld centerline and FL: fusion line.

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Fig. 17

Absorbed impact energy at −60 °C of each joint and their corresponding standard deviation (vertical lines). The horizontal dashed line depicts the minimum toughness requirement of 22 J. CL: weld centerline and FL: fusion line.

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Fig. 18

Width of CGHAZ in the vicinity of the welds was about 0.3 mm at its maximum in the case of the widest weld

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Fig. 19

Summary of the study, showing the experiments within the acceptable thresholds of cooling times (t8/5) for tensile strength and impact toughness properties. Quality threshold was estimated approximately.



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