بررسی ریزساختار، خواص مکانیکی و انبساط حفره فولاد پیشرفته استحکام بالا با رویکرد کاربرد در بدنه‌ی خودرو

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد، گروه مهندسی مواد، دانشگاه تربیت مدرس، تهران، ایران

2 استاد، گروه مهندسی مواد، دانشگاه تربیت مدرس، تهران، ایران

10.22034/ijme.2023.392262.1770

چکیده

در سال­‌های اخیر با افزایش رقابت بین شرکت­‌های خودروسازی و وضع قوانین دولتی مبنی بر کاهش بیشتر مصرف سوخت و به‌تبع آن الزام کاهش وزن خودرو، نسل سوم فولادهای پیشرفته استحکام بالا به دلیل استحکام کششی و شکل‌پذیری بهتر نسبت به نسل اول و هزینه کم­تر نسبت به نسل دوم، بسیار مورد توجه صنعت خودرو قرار گرفته‌اند. در این پژوهش، نماینده­‌ی جدیدی از نسل سوم فولادهای استحکام بالای پیشرفته، تحت عنوان 112HR طراحی، تولید و معرفی ‌شده و خواص مکانیکی آن مورد بررسی قرارگرفته و با فولاد SAPH440 که در حال حاضر در صنعت خودرو داخلی و در قسمت کابین خودرو استفاده می‌­شود، مقایسه گردیده است. آزمون کشش تک ‌محوره در سه جهت نورد، عمود بر نورد و زاویه 45 درجه نسبت به نورد انجام شد. فولاد 112HR با استحکام کششی 1190 مگاپاسکال و ازدیاد طول 5/54 درصد و شاخص شکل­‌پذیری بیش از 60 گیگا پاسکال درصد، خواص بهتری نسبت به  فولاد SAPH440 با استحکام کشش 450 مگا پاسکال و ازدیاد طول 43 درصد از خود نشان داده است. اما در آزمون کشش نمونه­‌ی شیاردار و انبساط حفره که تنش سه‌ بعدی است، فولاد 112HR عملکرد بدتری داشته است به ‌گونه‌ای که میزان انبساط حفره فولاد SAPH440 نسبت به فولاد 112HR، حدود 76/3 برابر بیشتر بوده است. علت این اختلاف خواص استحاله‌­ی آستنیت به مارتنزیت حین تغییر شکل در فولاد 112HR و کم بودن مقاومت برشی مارتنزیت است. تبدیل آستنیت به مارتنزیت توسط پراش اشعه ایکس و بررسی­‌های میکروسکوپی نوری و الکترونی در فولاد 112HR تائید شد.

کلیدواژه‌ها


عنوان مقاله [English]

Investigating the microstructure, mechanical properties and hole expansion of advanced high strength steel with the approach of application in the car body

نویسندگان [English]

  • Fateme Ahmadi 1
  • Mohammad Zabihi Gargari 1
  • Hamidreza Shahverdi 2
1 MSc Student, Department of Metallurgical Engineering, Tarbiat Modares University, Tehran, Iran
2 Professor, Department of Metallurgical Engineering, Tarbiat Modares University, Tehran, Iran
چکیده [English]

In recent years, with the increase in competition between automobile companies and the establishment of government laws to further reduce fuel consumption and, as a result, the requirement to reduce vehicle weight, the third generation of advanced strength steels have received much attention in the automotive industry due to their better tensile strength and ductility than the first generation and lower cost than the second generation. In this research, a new candidate of the third generation of advanced high-strength steels, with the name of 112HR, was design, production, and introduced and its mechanical properties were investigated and compared with SAPH440 steel, which is currently used in the domestic car industry and in the car cabin. Uniaxial tensile test was performed in three directions of rolling, perpendicular to rolling and 45-degree angle to rolling. 112HR steel with a tensile strength of 1190 MPa and an increase in length of 54.5% and a ductility index of more than 60 GPa% has shown better properties than SAPH440 steel with a tensile strength of 450 MPa and elongation of 43%. But in the tensile test of grooved sample and hole expansion, which is a three-dimensional stress, 112HR steel performed worse, so that the cavity expansion rate of SAPH440 steel was about 3.76 times higher than that of 112HR steel. The reason for this difference is the transformation properties of austenite to martensite during deformation in 112HR steel and the low shear strength of martensite. The transformation of austenite to martensite was confirmed by X-ray diffraction and optical and electron microscopic investigations in 112HR steel.

کلیدواژه‌ها [English]

  • Advanced High Strength Steel (AHSS)
  • Hole Expansion
  • Transformation of Austenite to Martensite
  • Deformation index
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