CR3 ve Kaplamalı TBF Çelik Sacların Mikro Yapısı ve Mekanik Özellikleri Üzerine Elektrik Direnç Punta Kaynağının Etkileri

Abstract

Bu çalışma, CR3 ve kaplamalı TBF çelik sacların elektrik direnç nokta kaynağı ile birleştirilmesini sunmaktadır. Kaynak parametrelerinin, kaynak bölgesinin makro/mikroyapısı, çekirdek çapı, çökme miktarı ve yük taşıma kapasitesi üzerindeki etkileri, kaynak akımı ve süresi değiştirilerek incelenmiştir. Belirgin bir makro kusur gözlenmemiş, ancak ergime bölgelerinde sınırlı bir karışım görülmüştür. Daha yüksek ısı girdisi karışımı iyileştirmiş ve TBF tarafındaki ısıdan etkilenen bölgeyi (HAZ) genişletmiştir, ancak kaplamadan kaynaklanan sıvı metal gevrekleşmesi (LME) ile ilişkili mikroçatlak riskini de artırmıştır. CR3 tarafında, ergime bölgesine yakın kısımlarda sadece tane irileşmesi gözlemlenmiştir. Isı girdisi arttıkça çekirdek çapı ve çökme miktarı artmış, ancak kaynak dayanımı düşük kalmıştır. Çekme testleri, kırılmaların CR3 tarafındaki HAZ bölgesinde yırtılma şeklinde gerçekleştiğini göstermiştir. TBF tarafında mikroçatlaklar oluşmasına rağmen, daha ince olan CR3 çeliği birleşme dayanımını belirlemiştir.

Keywords

• Direnç punta kaynağı
• Otomotiv çelik sacları
• Sıvı metal kırılganlığı

The Effects of Electric Resistance Spot Welding on the Microstructure and Mechanical Properties of CR3 and Coated TBF Steel Sheets

Abstract

This study investigates the resistance spot welding behavior of dissimilar low-carbon CR3 steel and coated transformation-induced plasticity-aided bainitic ferrite (TBF) steel sheets widely used in automotive body applications. The effects of welding current (6-7-8-9 kA) and welding time (240–400 ms) on weld microstructure, nugget size, indentation depth, and mechanical performance were systematically examined. Metallographic analysis revealed no macroscopic weld defects; however, limited mixing was observed in the fusion zone, particularly at lower heat inputs. Increasing heat input enhanced material mixing and widened the heat-affected zone (HAZ), especially on the TBF side, but also promoted liquid metal embrittlement (LME)-induced surface microcracks associated with Zn-coating penetration along grain boundaries. The maximum nugget size reached 8.34 mm at 9 kA–400 ms, while the indentation depth remained within automotive acceptance limits, with a maximum value of 21.65%. Tensile-shear tests showed that all fractures occurred in the HAZ of the thinner CR3 sheet in a tearing mode, with a maximum failure load of 4.25 kN at 7 kA–240 ms. Despite the presence of microcracks in the TBF HAZ, the joint strength was governed by the lower-strength CR3 sheet. The results highlight the importance of optimized welding parameters to balance sufficient nugget growth and minimize LME susceptibility in dissimilar advanced high-strength steel (AHSS)–mild steel combinations.

Keywords

• Resistance spot welding
• Automotive steel sheets
• Dissimilar welding
• TRIP-aided bainitic ferrite (TBF) steel
• Mild steel (CR3)
• Liquid metal embrittlement (LME)
• Tensile-shear strength

References

1. American Welding Society. (2012). Test methods for evaluating the resistance spot welding behavior of automotive sheet steel materials (AWS D8.9M:2012). American Welding Society. https://pubs.aws.org/p/1067/d89m2012
2. American Welding Society. (2013). Specification for automotive weld quality resistance spot welding of steel (AWS D8.1M:2013). American Welding Society. https://pubs.aws.org/p/1225/d81m2013
3. Aydın, H., Tutar, M., Davut, K., & Bayram, A. (2020). Effect of welding current on microstructure and mechanical properties of 15% deformed TWIP steel joined with electrical resistance spot welding. Journal of the Faculty of Engineering and Architecture of Gazi University, 35(2), 803–818. https://doi.org/10.17341/gazimmfd.530292
4. Aydın, H., Yılmaz, İ. Ö., & Bilici, A. Y. (2022). Investigation of microstructure and mechanical properties of dissimilar electrical resistance spot welded TBF/DP600 steel sheets. Journal of the Faculty of Engineering and Architecture of Gazi University, 37(2), 609–624. https://doi.org/10.17341/gazimmfd.808950
5. Bhattacharya, D. (2022). Influence of selected alloying elements and starting microstructure on Zn-assisted liquid metal embrittlement susceptibility of advanced high strength steels (Publication No. 29068161) [Doctoral dissertation, Colorado School of Mines]. ProQuest Dissertations & Theses Global.
6. Bouaziz, O., Zurob, H., & Huang, M. (2013). Driving force and logic of development of advanced high strength steels for automotive applications. Steel Research International, 84(10), 937–947. https://doi.org/10.1002/srin.201200288
7. British Standards Institution. (2006). Cold rolled low carbon steel flat products for cold forming—technical delivery conditions (EN 10130:2006). British Standards Institution. https://www.en-standard.eu/bs-en-10130-2006
8. Chabok, A., van der Aa, E., & Pei, Y. (2020). A study on the effect of chemical composition on the microstructural characteristics and mechanical performance of DP1000 resistance spot welds. Materials Science and Engineering: A, 788, Article 139501. https://doi.org/10.1016/j.msea.2020.139501

9. Chebolu, A. (2020). Automotive lightweighting: A brief outline. In A. Singh, N. Sharma, R. Agarwal, & A. Agarwal (Eds.), Advanced combustion techniques and engine technologies for the automotive sector (pp. 247–256). Springer. https://doi.org/10.1007/978-981-15-0368-9_12
10. DiGiovanni, C., Kalashami, A. G., Goodwin, F., Biro, E., & Zhou, N. Y. (2021). Occurrence of sub-critical heat affected zone liquid metal embrittlement in joining of advanced high strength steel. Journal of Materials Processing Technology, 288, Article 116917. https://doi.org/10.1016/j.jmatprotec.2020.116917
11. Hayat, F. (2024). Motorlu araç ağırlığının azaltılması yaklaşımı. Retrieved October 1, 2024, from https://indexive.com/uploads/papers/pap_indexive15944160932147483647.pdf
12. Hilditch, T. B., de Souza, T., & Hodgson, P. D. (2015). 2- Properties and automotive applications of advanced high-strength steels (AHSS). In M. Shome & M. Tumuluru (Eds.), Welding and joining of advanced high strength steels (AHSS) (pp. 9–28). Woodhead Publishing. https://doi.org/10.1016/B978-0-85709-436-0.00002-3
13. Hulka, I., Radu, B., Ungureanu, V., & Sîrbu, N. A. (2024). Microstructural investigation and mechanical properties of resistance spot welding joints of mild steel sheets. Key Engineering Materials, 989, 57–63. https://doi.org/10.4028/p-cTs0Ol
14. Hussein, K. M., Akbari, H., Noorossana, R., Yadegari, R., & Ashiri, R. (2024). Microhardness and microstructure correlations to the mechanical performance for dissimilar third generation AHSS resistance spot welding. Journal of Materials Research and Technology, 30, 7938–7945. https://doi.org/10.1016/j.jmrt.2024.05.177
15. Ikeda, Y. (2024). Early stages of liquid-metal embrittlement in a 3rd generation advanced high strength steel [Doctoral dissertation, Technische Universität Berlin]. https://doi.org/10.14279/depositonce-21382
16. Jin, W., Lalachan, A., Murugan, S. P., Ji, C., & Park, Y.-D. (2022). Effect of process parameters and nugget growth rate on liquid metal embrittlement (LME) cracking in the resistance spot welding of zinc-coated steels. Journal of Welding and Joining, 40(6), 464–477. https://doi.org/10.5781/JWJ.2022.40.6.2
17. Kulkarni, S., Edwards, D. J., Parn, E. A., Chapman, C., Aigbavboa, C. O., & Cornish, R. (2018). Evaluation of vehicle lightweighting to reduce greenhouse gas emissions with focus on magnesium substitution. Journal of Engineering, Design and Technology, 16(6), 869–888. https://doi.org/10.1108/JEDT-03-2018-0042
18. Li, Y., Tang, H., & Lai, R. (2021). Microstructure and mechanical performance of resistance spot welded martensitic advanced high strength steel. Processes, 9(6), Article 1021. https://doi.org/10.3390/pr9061021
19. Ling, Z., Wang, M., Kong, L., & Chen, K. (2020). Towards an explanation of liquid metal embrittlement cracking in resistance spot welding of dissimilar steels. Materials & Design, 195, Article 109055. https://doi.org/10.1016/j.matdes.2020.109055
20. Murugan, S. P., Vijayan, V., Ji, C., & Park, Y.-D. (2020). Four types of LME cracks in RSW of Zn-coated AHSS. Welding Journal, 99(3), 75–92. https://doi.org/10.29391/2020.99.008
21. Nadimi, N., Kabirmohammadi, M., & Pouranvari, M. (2024). Failure of dissimilar QP980/DP600 advanced high strength steels resistance spot welds. Journal of Materials Research and Technology, 30, 9601–9611. https://doi.org/10.1016/j.jmrt.2024.06.052
22. Ozturk Yilmaz, I., Bilici, A. Y., & Aydin, H. (2019). Microstructure and mechanical properties of dissimilar resistance spot welded DP1000–QP1180 steel sheets. Journal of Central South University, 26(1), 25–42. https://doi.org/10.1007/s11771-019-3980-3
23. Paveebunvipak, K., & Uthaisangsuk, V. (2018). Microstructure based modeling of deformation and failure of spot-welded advanced high strength steels sheets. Materials & Design, 160, 731–751. https://doi.org/10.1016/j.matdes.2018.09.052
24. Safanama, D. S., Marashi, S. P. H., & Pouranvari, M. (2012). Similar and dissimilar resistance spot welding of martensitic advanced high strength steel and low carbon steel: Metallurgical characteristics and failure mode transition. Science and Technology of Welding and Joining, 17(4), 288–294. https://doi.org/10.1179/1362171812Y.0000000006
25. Shiri, S. (2025). Resistance spot welding of dual-phase high-ductility steels: Liquid metal embrittlement investigation, short-pulse welding, and microstructural–mechanical–electrical correlations [Doctoral dissertation, The University of Alabama]. https://ir.ua.edu/handle/123456789/17092
26. Siar, O., Dancette, S., Dupuy, T., & Fabrègue, D. (2021). Impact of liquid metal embrittlement inner cracks on the mechanical behavior of 3rd generation advanced high strength steel spot welds. Journal of Materials Research and Technology, 15, 6678–6689. https://doi.org/10.1016/j.jmrt.2021.11.100
27. Sobhani, S., & Pouranvari, M. (2019). Duplex stainless steel/martensitic steel dissimilar resistance spot welding: Microstructure-properties relationships. Welding Journal, 98(9), 263–272. https://doi.org/10.29391/2019.98.023
28. Spena, P. R., De Maddis, M., Lombardi, F., & Rossini, M. (2016). Dissimilar resistance spot welding of Q&P and TWIP steel sheets. Materials and Manufacturing Processes, 31(3), 291–299. https://doi.org/10.1080/10426914.2015.1048476
29. Stotts, M. (2018). Liquid metal embrittlement in resistance spot dissimilar welds on advanced high strength steels: Microstructure and fracture characteristic [Undergraduate Thesis, The Ohio State University]. http://hdl.handle.net/1811/86881
30. Sugimoto, K.-i. (2021). Recent progress of low and medium-carbon advanced martensitic steels. Metals, 11(4), Article 652. https://doi.org/10.3390/met11040652
31. Sugimoto, K.-i., Hojo, T., & Kobayashi, J. (2017). Critical assessment 29: TRIP-aided bainitic ferrite steels. Materials Science and Technology, 33(17), 2005–2009. https://doi.org/10.1080/02670836.2017.1356014
32. Sugimoto, K.-i., & Srivastava, A. K. (2015). Microstructure and mechanical properties of a TRIP-aided martensitic steel. Metallography, Microstructure, and Analysis, 4, 344–354. https://doi.org/10.1007/s13632-015-0221-5
33. Wang, B., Qiu, F., Chen, L., Zhou, Q., Dong, B., Yang, H., Yang, J., Feng, Z., Tyrer, N., Barber, G. C., & Hu, M. (2022). Microstructure and shearing strength of stainless steel/low carbon steel joints produced by resistance spot welding. Journal of Materials Research and Technology, 20, 2668–2679. https://doi.org/10.1016/j.jmrt.2022.08.041
34. Wei, F., Zhu, Y., Tian, Y., Liu, H., Zhou, Y., & Zhu, Z. (2022). Resistance spot-welding of dissimilar metals, medium manganese TRIP steel and DP590. Metals, 12(10), Article 1596. https://doi.org/10.3390/met12101596
35. Wei, S., Li, Y., & Lu, S. (2022). Similar and dissimilar resistance spot weldability of Q&P980 and TWIP1180 steels. Science and Technology of Welding and Joining, 27(2), 77–83. https://doi.org/10.1080/13621718.2021.1953941
36. Wei, S. T., Lv, D., Liu, R. D., & Lin, L. (2017). Similar and dissimilar resistance spot weldability of galvanised DP1000 and TWIP980 steels. Science and Technology of Welding and Joining, 22(4), 278–286. https://doi.org/10.1080/13621718.2016.1226569
37. Xie, Z.-J., Shang, C.-J., Wang, X.-L., Wang, X.-M., Han, G., & Misra, R. D. K. (2020). Recent progress in third-generation low alloy steels developed under M3 microstructure control. International Journal of Minerals, Metallurgy and Materials, 27, 1–9. https://doi.org/10.1007/s12613-019-1939-x
38. Xue, J., Peng, P., Guo, W., Xia, M., Tan, C., Wan, Z., Zhang, H., & Li, Y. (2021). HAZ characterization and mechanical properties of QP980-DP980 laser welded joints. Chinese Journal of Mechanical Engineering, 34(1), Article 80. https://doi.org/10.1186/s10033-021-00596-x