Dissimilar DP780/DP980 Resistance Spot Welded joints: Microstructure, Mechanical Properties and Critical Diameter
محورهای موضوعی : Welding
Bahman Valizadeh
1
,
Mehdi Mansouri
2
1 - Advanced Materials Research Center, Department of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran.
2 - Advanced Materials Research Center, Department of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran.
کلید واژه: Mechanical Behavior, Dissimilar resistance spot welding, DP780 Dual Phase steel, DP980 Dual Phase steel, critical weld nugget diameter,
چکیده مقاله :
In this research, microstructure and mechanical performance of dissimilar resistance spot welded DP780/DP980 dual-phase steels were studied utilizing optical microscope, microhardness, and tensile shear tests. Resistance spot welding (RSW) was performed in the current range of 7 to 12 kA, with 0.5 kA steps. At welding currents lower than 7 kA low amount of melting led to the very low strength of the joints due to small weld nugget diameter. The results showed that an increase in welding current from 7 kA up to 11 kA, result in an increase in weld nugget diameter. Further increase of welding current (higher than 11 kA), however decreased the weld nugget diameter due to severe melt expulsion. Microstructural studies showed that weld nugget was primarily comprised of martensite, and the heat-affected zone (HAZ) of both sides of the joint was comprised of three different microstructural zones; upper-critical HAZ (UCHAZ), inter-critical HAZ (ICHAZ), and sub-critical HAZ(SCHAZ). Microhardness test showed that at both sides, softening occurred at SCHAZ. The results of the tensile shear test showed that both peak load and fracture energy of the joints followed approximately the same trend as weld diameter with welding current. Two different fracture modes of interfacial failure (IF) and pullout failure (PF) were observed in the tensile-shear test. At welding currents lower than 10 kA, the failure occurred in IF mode, while at higher welding currents, PF was dominant. Weld nugget diameter at welding current of 10 kA; i.e., critical weld nugget diameter, was ~8.5 mm.
[1] Pouranvari M, Marashi SPH (2013) Critical review of automotive steels spot welding: process, structure and properties. Sci Technol Weld Join 18:361–403. https://doi.org/10.1179/1362171813Y.0000000120
[2] Pouranvari M, Marashi SPH (2012) Weld nugget formation and mechanical properties of three-sheet resistance spot welded low carbon steel. Can Metall Q 51:105–109. https://doi.org/10.1179/1879139511Y.0000000028
[3] Pouranvari M, Mousavizadeh SM, Marashi SPH, et al (2011) Influence of fusion zone size and failure mode on mechanical performance of dissimilar resistance spot welds of AISI 1008 low carbon steel and DP600 advanced high strength steel. Mater Des 32:1390–1398
[4] Pouranvari M, Marashi SPH (2012) On failure mode of resistance spot welded DP980 advanced high strength steel. Can Metall Q 51:447–455. https://doi.org/10.1179/1879139512Y.0000000034
[5] Gould JE, Khurana SP, Li T (2006) Predictions of microstructures when welding automotive advanced high-strength steels. Weld J (Miami, Fla) 85:
[6] Hernandez BVH, Kuntz ML, Khan MI, Zhou Y (2008) Influence of microstructure and weld size on the mechanical behaviour of dissimilar AHSS resistance spot welds. Sci Technol Weld Join 13:769–776. https://doi.org/10.1179/136217108X325470
[7] Ghaemifar S, Mirzadeh H (2017) Enhanced mechanical properties of dual-phase steel by repetitive intercritical annealing. Can Metall Q 56:459–463. https://doi.org/10.1080/00084433.2017.1361223
[8] Shukla N, Roy H, Show BK (2016) Effect of prior austempering heat treatment on the microstructure, mechanical properties and high-stress abrasive wear behaviour of a 0.33% C dual-phase steel. Can Metall Q 55:13–22. https://doi.org/10.1080/00084433.2015.1113671
[9] Zhang H, Qiu X, Bai Y, et al (2014) Resistance spot welding macro characteristics of the dissimilar thickness dual phase steels. Mater Des 63:151–158. https://doi.org/10.1016/J.MATDES.2014.05.060
[10] Abadi MMH, Pouranvari M (2014) Failure-mode transition in resistance spot welded DP780 advanced high-strength steel: Effect of loading conditions. Mater Tehnol 48:67–71
[11] Khan MI, Kuntz ML, Zhou Y (2008) Effects of weld microstructure on static and impact performance of resistance spot welded joints in advanced high strength steels. Sci Technol Weld Join 13:294–304. https://doi.org/10.1179/174329308X271733
[12] Pouranvari M (2011) Influence of welding parameters on peak load and energy absorption of dissimilar resistance spot welds of DP600 and AISI 1008 steels. Can Metall Q 50:381–388. https://doi.org/10.1179/1879139511Y.0000000008
[13] Zhang H, Wei A, Qiu X, Chen J (2014) Microstructure and mechanical properties of resistance spot welded dissimilar thickness DP780/DP600 dual-phase steel joints. Mater Des 54:443–449. https://doi.org/10.1016/J.MATDES.2013.08.027
[14] Liang J, Zhang H, Qiu X, Shi Y (2015) Characteristics of the Resistance Spot Welding Joints in Dissimilar Thickness Dual-phase Steels. ISIJ Int 55:2002–2007. https://doi.org/10.2355/isijinternational.ISIJINT-2015-151
[15] Di H, Sun Q, Wang X, et al (2017) Microstructure and properties in dissimilar/similar weld joints between DP780 and DP980 steels processed by fiber laser welding. J Mater Sci Technol 33:1561–1571. https://doi.org/10.1016/j.jmst.2017.09.001
[16] Pouranvari M, Marashi SPH, Mousavizadeh SM (2010) Failure mode transition and mechanical properties of similar and dissimilar resistance spot welds of DP600 and low carbon steels. Sci Technol Weld Join 15:625–631. https://doi.org/10.1179/136217110X12813393169534
[17] Gao S, Li Y, Yang L, Qiu W (2018) Microstructure and mechanical properties of laser-welded dissimilar DP780 and DP980 high-strength steel joints. Mater Sci Eng A 720:117–129. https://doi.org/10.1016/J.MSEA.2018.02.057
[18] Wei ST, Lv D, Liu RD, et al (2014) Similar and dissimilar resistance spot welding of advanced high strength steels: welding and heat treatment procedures, structure and mechanical properties. Sci Technol Weld Join 19:427–435. https://doi.org/10.1179/1362171814Y.0000000211
[19] Pouranvari M, Marashi SPH (2010) Key factors influencing mechanical performance of dual phase steel resistance spot welds. Sci Technol Weld Join 15:149–155. https://doi.org/10.1179/136217109X12590746472535
[20] Liu C, Zheng X, He H, et al (2016) Effect of work hardening on mechanical behavior of resistance spot welding joint during tension shear test. Mater Des 100:188–197. https://doi.org/10.1016/J.MATDES.2016.03.120
[21] Zhang H, Senkara J (2012) Resistance welding : fundamentals and applications. CRC Press, Boca Raton
[22] Wei ST, Liu RD, Lv D, et al (2016) Effect of joint configuration on resistance spot weldability of galvanised DP780 steel sheets. Sci Technol Weld Join 21:178–185. https://doi.org/10.1179/1362171815Y.0000000081
[23] Pouranvari M, Marashi SPH (2011) Failure mode transition in AHSS resistance spot welds. Part I. Controlling factors. Mater Sci Eng A 528:8337–8343. https://doi.org/10.1016/J.MSEA.2011.08.017
[24] American Welding Society. Joint Committee on Automotive Welding., American Welding Society. Technical Activities Committee., American National Standards Institute. Test methods for evaluating the resistance spot welding behavior of automotive sheet steel materials
[25] (2017) JIS Z 3144 : Routine test of resistance spot and projection welds, 13th ed. Japanese Standards Association (JSA)
[26] Y. J. Chao (2003) Failure mode of spot welds: interfacial versus pullout. Sci Technol Weld Join 8:133–137
[27] Sun X, Stephens E, Khaleel M (2006) Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds. SAE Trans. 115:509–516
[28] Pouranvari M, Marashi SPH, Safanama DS (2011) Failure mode transition in AHSS resistance spot welds. Part II: Experimental investigation and model validation. Mater Sci Eng A 528:8344–8352. https://doi.org/10.1016/J.MSEA.2011.08.016
