Çinko Kaplı Düşük Karbonlu Çeliklerin Nokta Kaynak Bağlantılarının Yorulma Özellikleri

Öz

EN 10346:2015 DX52D+Z, düşük mukavemetine rağmen üstün şekillendirilebilirliği nedeniyle otomotiv endüstrisinde yaygın olarak kullanılan, düşük karbonlu, soğuk şekillendirmeye uygun çinko kaplı bir çeliktir. Farklı ebat ve formlarda üretilen saclar, soğuk haddeleme sonrası sürekli galvanizleme hattından geçirilerek tavlanmaktadır. Bu çalışmada düşük kaynak akımı ve yüksek kaynak çevrimi ile nokta kaynağı ile birleştirilen bu çeliklerin yorulma özellikleri ölçülerek hasar karakterizasyonları da yapılmıştır. Farklı parametrelere sahip bir dizi bindirmeli bağlantı kullanılarak çekme testi yapılmış ve kaynak bölgesindeki sertlik değişimi de incelenmiştir. Yorulma testi sırasında çatlak başlangıcı ve ilerlemesi deneysel olarak belirlenmiştir. Ana metalden kaynak çekirdeğine kadar sertlikte önemli bir artış gözlenmiş ve kaynak işlemi, birleştirmeden gelen ısı etkisinden dolayı ana malzemenin mukavemetinde %38'lik bir azalmaya neden olmuştur. Mikrosertlik testinde en yüksek sertlik değeri kaynak çekirdeğinin ısıdan etkilenen bölgesinde (228.4 HV) ölçülmüştür ve ana metalin sertliği 169.4 HV olmuştur. Kaynaklı bağlantıların maksimum çekme yükünün yaklaşık %20'sinin altında sonsuz ömre sahip olduğu belirlenmiştir.

Anahtar Kelimeler

• Düşük karbonlu çelik
• Nokta kaynağı
• Düşük kaynak akımı
• Yüksek kaynak döngüleri
• Yorulma limiti

Fatigue Properties of Zinc Coated Low Carbon Steel Sheet Joints by the Means of Spot Welding

Öz

EN 10346:2015 DX52D+Z steel is a low-carbon, zinc-coated steel suitable for cold forming, widely used in the automotive industry due to its superior formability despite its low strength. Sheets produced in different sizes and forms are annealed by passing through the continuous galvanizing line after cold rolling. In this study, fatigue properties of these steels which were joined by spot welding with low welding current and high welding cycles, were measured and failure characterization was made, too. Tensile testing was made using a number of lap joints with different parameters and the variation of hardness within the weld area was also investigated. During the fatigue testing, crack initiation and propagation have been experimentally determined. A significant increase in hardness was observed from the base metal to the weld nugget, and the welding process caused a 38% reduction in the strength of the base material due to the heat affect from the joint. In the microhardness test, the highest hardness value was measured in the weld nugget heat affected zone (228.4 HV), and the hardness of the base metal was 169.4 HV. It has been determined that welded joints have infinite life below approximately 20% of the maximum tensile load.

Anahtar Kelimeler

• Low carbon steel
• Spot welding
• Low welding current
• High welding cycles
• Fatigue limit

Kaynakça

1. Li, M., Tao, W., Zhang, J., Wang, Y., Yang, S. 2022. Hybrid resistance-laser spot welding of aluminium to steel dissimilar materials: Microstructure and mechanical properties, Materials & Design, Volume 221, 111022, ISSN 0264-1275.
2. Mallick, P.K. 2021. Chapter 8 - Joining for lightweight vehicles, In Woodhead Publishing in Materials, Materials, Design and Manufacturing for Lightweight Vehicles (Second Edition), Woodhead Publishing, Pages 321-371, ISBN 9780128187128, https://doi.org/10.1016/B978-0-12-818712-8.00008-2.
3. Raut, M., Achwal, V. 2014, Optimization of Spot Welding Process Parameters for Maximum Tensile Strength, Int. J. Mech. Eng. & Rob. Res., 506-517.
4. Holdren, R.L. 1993. What Are the Causes of and Solutions to Weld Quality Control, Welding Journal Vol. 72, No. 8.
5. Hirsch, R.B. 1993. Tip Force Control Equals Spot Weld Quality, Welding Journal, vol. 72, No. 3.
6. Cullison, A. 1993. Resistance Weld Controller Delivers the Heat Where It's Needed, Welding Journal, Vol. 72, No. 6.
7. James, P.S. Chandler, H.W., Evans, J.T., Wen J, Browne, D.J., Newton, C.J. 1997. The Effect of Mechanical Loading on The Contact Resistance of Coated Aluminium, Materials Science and Engineering: A, Volume 230, Issues 1–2, Pages 194-201.
8. Papkala, H. 1990. A New Method of Projection Welding of Galvanised Steel Sheet, Welding International, Volume 4, Issue 5 Pages 341-346.

9. Papkala, H. 1992, Technological Problems in Spot Welding of Galvanized Car Body Sheet, Journal Welding International, Volume 6, Issue 5.
10. Komizo, Y.I. 1987. Crack Susceptibility of Steel Plates Produced by The Thermo-Mechanical Control Process, Welding International, v.1, p.126-32.
11. Patel, S. Reddy, P., Kumar, A. 2021. A Methodology to Integrate Melt Pool Convection With Rapid Solidification And Undercooling Kinetics In Laser Spot Welding, International Journal of Heat and Mass Transfer, Volume 164.
12. Graham, S.L., Holzer, R.A., Gerbic, J.F. 2007. System and Method for Reducing Weld Spatter, US 20070284350 A1.
13. Parshuramkar, N.T., Rambhad, K.S., Chandran, R. 2017. Welding Spatter Reduction and Time Study: A Review. International Journal of Analytical, Experimental and Finite Element Analysis (IJAEFEA). 4. 10.26706/IJAEFEA.4.4.20171025.
14. Lum, I., Biro, E., Zhou, Y., Fukumoto, S., Boomer, D. 2004. Electrode Pitting in Resistance Spot Welding of Aluminum Alloy 5182. Metallurgical and Materials Transactions A. 35. 217-226. 10.1007/s11661-004-0122-8.
15. Ma, N., Murakawa, H. 2010, Numerical and experimental study on nugget formation in resistance spot welding for three pieces of high strength steel sheets. Journal of Materials Processing Technology - J Mater Process Technol. 210. 2045-2052. 10.1016/j.jmatprotec.2010.07.025.
16. Wang, B., Lou, M., Shen, Q., Li, Y., Zhang, H. 2013. Shunting effect in resistance spot welding steels - Part 1: Experimental study. 92. 182S-189S.
17. Müftüoğlu, F., Keskinel, T. 2007. Effect of Coating Thickness on Electrode Life in the Spot Welding of Galvanized Steels, Turkish J. Eng. Env. Sci. 31, p,183 – 187.
18. Tomoyuki, F., Keiichiro, T., Yukinori, S., Takahiro, Y., Yoshinobu, S. 2016. Fatigue strength and fatigue fracture mechanism of three-sheet spot weld-bonded joints under tensile–shear loading, International Journal of Fatigue, Volume 87, Pages 424-434, ISSN 0142-1123, https://doi.org/10.1016/j.ijfatigue.2016.02.023.
19. Chen, Z., Zhou, Y., Scotchmer, N. 2006. Coatings on Resistance Welding Electrodes to Extend Life. SAE Transactions,115, 106-110., http://www.jstor.org/stable/44722317.
20. Zou, J., Zhao, Q., Chen, Z. 2009. Surface modified long-life electrode for resistance spot welding of Zn-coated steel, Journal of Materials Processing Technology, Volume 209, Issue 8, Pages 4141-4146, ISSN 0924-0136, https://doi.org/10.1016/j.jmatprotec.2008.10.005.
21. Long, X., Khanna, Z.K. 2007. Fatigue properties and failure characterization of spot-welded high strength steel sheet Int J Fatigue, 29, pp. 879-886.
22. Wang, B., Duan, Q.Q., Yao, G., Pang, J.C., Li, X.W., Wang, L. 2014. Investigation on fatigue fracture behaviours of spot welded Q&P980 steel Int J Fatigue, 66, pp. 20-28.
23. Vural, M., Akkuş, A., Eryürek, B. 2006. Effect of welding nugget diameter on the fatigue strength of the resistance spot welded joints of different steel sheets, Journal of Materials Processing Technology, Volume 176, Issues 1–3, Pages 127-132, ISSN 0924-0136, https://doi.org/10.1016/j.jmatprotec.2006.02.026.
24. Pan, N., Sheppard, S. 2002. Spot welds fatigue life prediction with cyclic strain range, Int J Fatigue, 24, pp. 519-528.
25. Hassanifard, S., Zehsaz, M., Tohgo, K., Ohguma, T. 2009. The prediction of fatigue crack initiation life in spot welds Strain, 45, pp. 489-497.
26. Tanegashima, R., Akebono, H., Sugeta, A. 2017. Fatigue life estimation based on fracture mechanics of single spot-welded joints under different loading modes, Engineering Fracture Mechanics, Volume 175, Pages 115-126, ISSN 0013-7944, https://doi.org/10.1016/j.engfracmech.2017.01.031
27. Nakayama, E., Miyahara, M., Okamura, K., Fujimoto, H., 2004. Fukui, K. Prediction of fatigue strength of spot-welded joints based on local material strength properties measured by small specimen, J Soc Mater Sci, Jpn, 53 (12), pp. 1136-1142.
28. Tohgo, K., Ohguma, T., Shimamura, Y., Ojima, Y, 2009. Influence of strength level of steels on fatigue strength and fracture morphology of spot-welded joints, J. Soc. Mater. Sci, Jpn., 59 (7), pp. 627-634
29. Bae, D.H., Sohn, I.S., Hong, J.K. 2003. Assessing the effects of residual stresses on the fatigue strength of spot welds, Weld. J., pp. 18s-23s.
30. Lin, S.H., Pan, J., Wung, P., Chiang, J. 2006. A fatigue crack growth model for spot welds under cyclic loading conditions, Int J Fatigue, 28 (7), pp. 792-803.
31. Ertaş, A.H., Yılmaz, Y., Baykara, 2008, C. An investigation of the effect of the gap values between the overlap portions of the spot-welded pieces on fatigue life, Proc. Inst. Mech. Eng., Part C: J. Mech. Eng. Sci., 222 (6), pp. 881-890.
32. Dancette, S., Fabregue, D., Estevez, R. 2012. A finite element model for the prediction of advanced high strength steel spot welds fracture, Eng. Fract. Mech., 87, pp. 48-61.
33. Nguyen, T.N., Wahab, M.A. 1998. The effect of weld geometry and residual stresses on the fatigue of welded joints under combined loading, J. Mater. Process. Technol., 77 (1–3), pp. 201-208.
34. Kumar, A., Panda, S., Ghosh, G.K., Patel, R.K. 2020. Numerical simulation of weld nugget in resistance spot welding process, Materials Today: Proceedings, Volume 27, Part 3, pp 2958-2963, ISSN 2214-7853, https://doi.org/10.1016/j.matpr.2020.04.901.
35. Eisazadeh, H., Hamedi, M., Halvaee, A. 2010. New parametric study of nugget size in resistance spot welding process using the finite element method, Mater. Des., 31, pp. 149-157, 10.1016/j.matdes.2009.06.042
36. Ünlükal, E. 2007. Otomotiv Sanayinde Kullanılan Direnç Nokta Kaynak Kalitesinin Artırılması, Master Thesis, Bursa.
37. Akyol, M. 2001. Otomotiv Sanayiinde Kullanılan Direnç Nokta Kaynak Uygulamaları ve Karşılaşılan Sorunlar, İ.T.Ü. Fen Bilimleri Enstitüsü, Master Thesis, İstanbul.
38. Saleem, J., Majid, A., Bertilsson, K., Carlberg, T., Islam, N. 2012. Nugget Formation during Resistance Spot Welding using Finite Element Model, International Journal of Mechanical and Mechatronics Engineering, World Academy of Science, Engineering and Technology, vol. 67(7). 1228 – 1233.
39. Rathbun, R.W., Matlock, D., Speer, J.G. 2003. Fatigue Behavior of Spot Welded High-Strength Sheet Steels. Welding Journal (Miami, Fla). 82. 207/S-218/S.
40. Guennec, B., Akira, U., Tatsuo, S., Masahiro, T., Yu, I. 2013.s Effect of Loading Frequency in Fatigue Properties and Micro-Plasticity Behaviour of JIS S15C Low Carbon Steel, 13th International Conference on Fracture, 16–21 June, Beijing, China.
41. Mirzaei, F., Ghorbani, H., Kolahan, 2017. F. Numerical modeling and optimization of joint strength in resistance spot welding of galvanized steel sheets. Int. J. Adv. Manuf. Technol. 92, 3489–3501.
42. Pouranvari, M., Abedi, A.,Marashi, P., Goodarzi, M. 2008. Effect of expulsion on peak load and energy absorption of low carbon resitance spot welds. Science and Technology of Welding & Joining. 13. 39-43. 10.1179/174329307X249342.
43. Kocabekir, B., Kaçar, R., Gündüz, S., Hayat, F. 2008. An effect of heat input, weld atmosphere and weld cooling conditions on the resistance spot weldability of 316L austenitic stainless steel. Journal of Materials Processing Technology. 195. 327-335. 10.1016/j.jmatprotec.2007.05.026.
44. Shen, J., Zhang, Y., Wang, P.C. 2011. Nugget shifting in resistance spot welding of multi-stackup sheets. Quarterly Journal Of The Japan Welding Society. 29. 133s-137s. 10.2207/qjjws.29.133s.
45. Khodabakhshi, F., Kazeminezhad, M., Kokabi, A. H. 2011. Mechanical properties and microstructure of resistance spot welded severely deformed low carbon steel. Materials Science and Engineering A-structural Materials Properties Microstructure and Processing - Mater Sci Eng A-Struct Mater. 529. 237-245. 10.1016/j.msea.2011.09.023.