بررسی ریزساختار میلگردهای فولادی S400 جوش شده به روش جوشکاری مقاومتی سربهسر به همراه شبیهسازی عددی
محورهای موضوعی : فصلنامه علمی - پژوهشی مواد نوین
هدی میرسیفی
1
,
حامد قوهانی عرب
2
,
محمود شریفی تبار
3
1 - دانشجوی دکتری، گروه مهندسی عمران، دانشکده مهندسی شهید نیکبخت، دانشگاه سیستان و بلوچستان، زاهدان، ایران
2 - دانشیار، گروه مهندسی عمران، دانشکده مهندسی شهید نیکبخت، دانشگاه سیستان و بلوچستان، زاهدان، ایران
3 - گروه مهندسی مواد، دانشکده شهید نیکبخت، دانشگاه سیستان و بلوچستان
کلید واژه: جوشکاری مقاومتی سر به سر, میلگرد فولادی, شبیهسازی عددی, رفتار حرارتی, سرعت سرد شدن,
چکیده مقاله :
مقدمه: فناوریهای جوشکاری بهدلیل صرفهجویی اقتصادی و ایجاد اتصالات مقاوم، در صنعت ساختوساز کاربرد گستردهای دارند و جوشکاری مقاومتی سر به سر یکی از روشهای مهم برای اتصال میلگردهای فولادی است. با وجود کاربرد گسترده این روش در سازههای بتنآرمه، رفتار ریزساختاری و مکانیکی میلگردهای S400 جوش دادهشده هنوز بهطور کامل بررسی نشده است.
روش: در این پژوهش، ریزساختار و استحکام مکانیکی میلگردهای فولادی S400 که به روش جوشکاری مقاومتی سربهسر متصل شدهاند، بررسی شده است. فرآیند جوشکاری بهصورت تجربی و با استفاده از شبیهسازی عددی توسط روش اجزا محدود انجام شده است. نمونهها با قطرهای۱۲، ۱۴ و ۱۸ میلیمتر تحت شرایط متنوع جوشکاری قرار گرفتند و تغییرات دما، توزیع کرنش پلاستیک، و ریزساختار آنها با نرمافزار JMat Pro و مدل جانسون-کوک تحلیل شد.
یافته ها: از آنجا که ریزساختار در ناحیه جوش در طول فرآیند خنکسازی ایجاد میشود، سرعت خنکسازی بهطور قابلتوجهی بر روی تبدیل فاز و ریزساختار نهایی تأثیر میگذارد. سرعت سرد شدن ناحیه جوش در محدوده دمایی ˚C800 تا ˚C500 تقریباً ˚C/s 10 برآورد شد. نتایج نشان داد که به دلیل دمای بالای سطح مشترک (یعنی ˚C1470) و متعاقب آن سرعت سرد شدن متوسط آن، فریت سوزنی شکل در این ناحیه تشکیل میشود. همچنین ریزساختار ناحیه جوش شامل فریت مرزدانه، فریت ویدمن اشتاتن، و فریت بینیتی است و با افزایش شدت جریان، میزان کرنش پلاستیک نیز افزایش مییابد.
نتیجه گیری: این یافتهها به بهینهسازی پارامترهای جوشکاری و پیشبینی عملکرد اتصال در کاربردهای سازهای کمک میکنند.
Introduction: Welding technologies are widely used in construction for their cost-efficiency and ability to create strong joints, with resistance upset butt welding being a notable method for joining steel rebars. Although RUBW is commonly applied in reinforced concrete structures, the microstructural and mechanical behavior of S400 welded rebars remains underexplored.
Methods: In this study, the microstructure and mechanical strength of S400 steel rebars joined by resistance butt welding were investigated. The welding process was carried out experimentally and numerically using the finite element method. Specimens with different diameters of 12, 14, and 18 mm were subjected to various welding conditions, and their temperature variations, plastic strain distribution, and microstructure were analyzed using JMat Pro software and the Johnson-Cook model.
Findings: Since the microstructure in the weld zone develops during the cooling process, the cooling rate significantly influences phase transformation and the final microstructure. The cooling rate in the weld zone within the temperature range of 800°C to 500°C was estimated to be approximately 10°C/s. The results revealed that due to the high interface temperature (i.e., 1470°C) and subsequent moderate cooling rate, acicular ferrite forms in this region. Additionally, the weld zone microstructure consists of grain boundary ferrite, Widmanstätten ferrite, and bainitic ferrite, with plastic strain increasing as the current intensity rises.
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