تاثیر فرآیند ترمومکانیکی بر روی فولادهای بینیتی نانوساختار کربن متوسط

کلاهی, علیرضا; پورشادلو, میثم; پالیزدار, یحیی

doi:10.22076/me.2019.98253.1219

تاثیر فرآیند ترمومکانیکی بر روی فولادهای بینیتی نانوساختار کربن متوسط

نوع مقاله : مقاله پژوهشی

نویسندگان

¹ پژوهشکده فناوری نانو و مواد پیشرفته، پژوهشگاه مواد و انرژی، کرج، ایران

² پژوهشکده نانو، پژوهشگاه مواد و انرژی، مشکین دشت، ایران

10.22076/me.2019.98253.1219

چکیده

در سال‌های اخیر تلاش‌های زیادی برای توسعه‌ی نسل جدیدی از فولادها تحت عنوان فولادهای نانوساختار بینیتی انجام شده است. اندازه دانه آستنیت اولیه از پارامترهای موثر در تشکیل ریزساختار بینیتی می‌باشد. فرآیند مارتنزیت از جمله فرآیندهای ترمومکانیکی پیشرفته است که مشتمل بر نورد سرد ریزساختار مارتنزیتی و آنیل متعاقب آن می‌باشد. در این پژوهش سعی شده است تا تاثیر تلفیق فرآیند مارتنزیت و فرآیند آستمپرینگ بر روی ریزساختار و خواص مکانیکی فولادهای نانوساختار بینیتی بررسی شود. فولا مورد استفاده در این پژوهش از نوع کربن متوسط و آلومینیوم بالا بوده که طراحی و سپس ریخته‌گری شده و در نهایت نورد داغ شده است. این فولاد در دمای °C 1030 به مدت 20 دقیقه آستنیته شده و سپس در آب کوئنچ گردید تا ساختار مارتنزیت حاصل گردد. نمونه‌ها به میزان 20 درصد توسط نورد سرد کاهش مقطع داده شده و سپس در دمای °C 600 به مدت 20 دقیقه آنیل شدند. نمونه‌ها مجددا در دما و زمان مشابه آستنیته شده و در دمای °C 340 تحت عملیات آستمپرینگ قرار گرفتند. بررسی‌های ریزساختاری با استفاده از پراش پرتو ایکس، میکروسکوپ‌های نوری و الکترونی روبشی انجام گرفت و به منظور ارزیابی خواص مکانیکی از آزمون کشش استفاده شد. به دلیل تشدید نرخ استحاله بینیتی و تغییرات کم اندازه دانه آستنیت اولیه تفاوت زیادی در خواص مشاهده نشد. استحکام کشش نهایی برای نمونه‌ها با اندازه دانه بزرگ (47 میکرومتر) 1279مگاپاسکال با ازدیاد طول 23 درصد و برای نمونه‌ها با اندازه دانه ریزتر (33 میکرومتر) 1231 مگاپاسکال با ازیاد طول 19 درصد به دست آمد.

کلیدواژه‌ها

عنوان مقاله [English]

The effect of thermomechanical process on the nanobainitic medium carbon steels

نویسندگان [English]

alireza kolahi ¹
Meysam Pourshadloo ²
yahya palizdar ¹

¹ Department of Nanotechnology and Advanced Materials, Materials and Energy Research Center (MERC), Karaj, Iran.

² insitute of materials and energy (MERC), meshkin-dasht, iran

چکیده [English]

The austenite grain size has a significant influence on phase transformation and mechanical properties of bainitic steels. The martensite treatment including cold rolling and subsequent annealing of microstructures with high percentage of martensite is one of the most effective thermo-mechanical methods for the grain refinement in steels. The present study aims to investigate the effects of thermomechanical and austempering processes on the microstructure and mechanical properties of the medium carbon high aluminium nanobainitic steel. In this regard, nanostructured bainitic steels with lower carbon content (0.45 wt%) than conventional supper bainitic steel were cast and hot rolled. To obtain the bainitic structure the specimens were austenitized at 1030 °C for 20 min and quenched in water. The specimens were subjected to 20% reduction in thickness by cold rolling and subsequent annealing at 600 °C for 20 min. The specimens were austenitized and transformed isothermally at 340 °C and finally were quenched in water. The microstructure was characterized by X-ray diffraction (XRD), optical (OM) and field emission scanning electron microscopy (FESEM) as well as tensile test for mechanical properties. The results showed that no significant changes were obtained in properties due to the increase in the rate of bainitic transformation and low changes in the austenite grain size. For specimens with a coarse austenite grain size (47 µm) the strength of 1279 MPa and elongation of 23% and for specimens with a fine austenite size (33 µm) the strength of 1231 MPa with a elongation of 19%, were obtained.

کلیدواژه‌ها [English]

Bainitic steel
Nano structure
Martensite process
Medium carbon high aluminum steel

مراجع

Bhadeshia HK. Nanostructured bainite. InProceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 2010 Jan 8 (Vol. 466, No. 2113, pp. 3-18). The Royal Society.
Caballero FG, Bhadeshia HK, Mawella KJ, Jones DG, Brown P. Very strong low temperature bainite. Materials science and technology. 2002 Mar 1;18(3):279-84.
Bhadeshia HK. Bainite in steels 2nd ed. The Institute of Materials, London. 2001.
Podder AS. Tempering of a mixture of bainite and retained austenite (Doctoral dissertation, University of Cambridge).
Garcia-Mateo C, FG C, HKDH B. Acceleration of low-temperature bainite. ISIJ international. 2003 Nov 15;43(11):1821-5.
Song R, Ponge D, Raabe D, Speer JG, Matlock DK. Overview of processing, microstructure and mechanical properties of ultrafine grained bcc steels. Materials Science and Engineering: A. 2006 Dec 15;441(1-2):1-7.
Murty SN, Torizuka S, Nagai K, Kitai T, Kogo Y. Dynamic recrystallization of ferrite during warm deformation of ultrafine grained ultra-low carbon steel. Scripta materialia. 2005 Sep 1;53(6):763-8.
Tsuji N, Ueji R, Minamino Y, Saito Y. A new and simple process to obtain nano-structured bulk low-carbon steel with superior mechanical property. Scripta Materialia. 2002 Feb 28;46(4):305-10.
Tianfu J, Yuwei G, Guiying Q, Qun L, Tiansheng W, Wei W, Furen X, Dayong C, Xinyu S, Xin Z. Nanocrystalline steel processed by severe rolling of lath martensite. Materials Science and Engineering: A. 2006 Sep 25;432(1-2):216-20.
Furuhara T, Kikumoto K, Saito H, Sekine T, Ogawa T, Morito S, Maki T. Phase transformation from fine-grained austenite. ISIJ international. 2008 Aug 15;48(8):1038-45.
Wang TS, Zhang FC, Zhang M, Lv B. A novel process to obtain ultrafine-grained low carbon steel with bimodal grain size distribution for potentially improving ductility. Materials Science and Engineering: A. 2008 Jun 25;485(1-2):456-60.
Mazaheri Y, Kermanpur A, Najafizadeh A, Saeidi N. Effects of initial microstructure and thermomechanical processing parameters on microstructures and mechanical properties of ultrafine grained dual phase steels. Materials Science and Engineering: A. 2014 Aug 26;612:54-62.
Rezaee A, Kermanpur A, Najafizadeh A, Moallemi M. Production of nano/ultrafine grained AISI 201L stainless steel through advanced thermo-mechanical treatment. Materials Science and Engineering: A. 2011 Jun 15;528(15):5025-9.
Ghassemali E, Kermanpur A, Najafizadeh A. Microstructural evolution in a low carbon steel during cold rolling and subsequent annealing. Journal of nanoscience and nanotechnology. 2010 Sep 1;10(9):6177-81.
Garcia-Junceda A, Capdevila C, Caballero FG, de Andres CG. Dependence of martensite start temperature on fine austenite grain size. Scripta Materialia. 2008 Jan 1;58(2):134-7.
Wang XL, Wu KM, Hu F, Yu L, Wan XL. Multi-step isothermal bainitic transformation in medium-carbon steel. Scripta Materialia. 2014 Mar 1;74:56-9.
Pereloma E, Edmonds DV, editors. Phase transformations in steels: Diffusionless transformations, high strength steels, modelling and advanced analytical techniques. Elsevier; 2012 May 11.
Rees GI, Bhadeshia HK. Bainite transformation kinetics part 1 modified model. Materials Science and Technology. 1992 Nov 1;8(11):985-93.
Jacques PJ. Experimental investigation of the influence of the austenite grain size on the mechanism and kinetics of the bainite transformation in steels. InJournal de Physique IV (Proceedings) 2003 Oct 1 (Vol. 112, pp. 297-300). EDP sciences.
Hu F, Hodgson PD, Wu KM. Acceleration of the super bainite transformation through a coarse austenite grain size. Materials letters. 2014 May 1;122:240-3.
Xu G, Liu F, Wang L, Hu H. A new approach to quantitative analysis of bainitic transformation in a superbainite steel. Scripta Materialia. 2013 Jun 1;68(11):833-6.
Lan LY, Qiu CL, Zhao DW, Gao XH, Du LX. Effect of austenite grain size on isothermal bainite transformation in low carbon microalloyed steel. Materials Science and Technology. 2011 Nov 1;27(11):1657-63.
Jiang T, Liu H, Sun J, Guo S, Liu Y. Effect of austenite grain size on transformation of nanobainite and its mechanical properties. Materials Science and Engineering: A. 2016 Jun 1;666:207-13.
Garcia-Mateo C, FG C, HKDH B. Acceleration of low-temperature bainite. ISIJ international. 2003 Nov 15;43(11):1821-5.
Matsuzaki A, Bhadeshia HK. Effect of austenite grain size and bainite morphology on overall kinetics of bainite transformation in steels. Materials Science and Technology. 1999 May 1;15(5):518-22.
Garcia-Mateo C, Caballero FG, Bhadeshia HK. Mechanical properties of low-temperature bainite. InMaterials Science Forum 2005 (Vol. 500, pp. 495-502). Trans Tech Publications.
Kvackaj T, Mamuzic I. A quantitative characterization of austenite microstructure after deformation in nonrecrystallization region and its influence on ferrite microstructure after transformation. ISIJ international. 1998 Nov 15;38(11):1270-6.
Pereloma E, Edmonds DV, editors. Phase transformations in steels: Diffusionless transformations, high strength steels, modelling and advanced analytical techniques. Elsevier; 2012 May 11.
Amel-Farzad H, Faridi HR, Rajabpour F, Abolhasani A, Kazemi S, Khaledzadeh Y. Developing very hard nanostructured bainitic steel. Materials Science and Engineering: A. 2013 Jan 1;559:68-73.
Singh SB, Bhadeshia HK. Estimation of bainite plate-thickness in low-alloy steels. Materials Science and Engineering: A. 1998 Apr 30;245(1):72-9.
Garcia-Mateo C, Caballero FG, Sourmail T, Kuntz M, Cornide J, Smanio V, Elvira R. Tensile behaviour of a nanocrystalline bainitic steel containing 3 wt% silicon. Materials Science and Engineering: A. 2012 Jul 15;549:185-92.
Singh K, Kumar A, Singh A. Effect of Prior Austenite Grain Size on the Morphology of Nano-Bainitic Steels. Metallurgical and Materials Transactions A. 2018 Apr 1;49(4):1348-54.
Lan HF, Du LX, Li Q, Qiu CL, Li JP, Misra RD. Improvement of strength-toughness combination in austempered low carbon bainitic steel: The key role of refining prior austenite grain size. Journal of Alloys and Compounds. 2017 Jul 5;710:702-10.
Kumar A, Singh A. Toughness dependence of nano-bainite on phase fraction and morphology. Materials Science and Engineering: A. 2018 May 29.
Hajiannia I, Shamanian M, Atapour M, Ghassemali E, Saeidi N. Development of Ultrahigh Strength TRIP Steel Containing High Volume Fraction of Martensite and Study of the Microstructure and Tensile Behavior. Transactions of the Indian Institute of Metals. 2018 Jun 1:1-8.
Lee SJ, Park JS, Lee YK. Effect of austenite grain size on the transformation kinetics of upper and lower bainite in a low-alloy steel. Scripta Materialia. 2008 Jul 1;59(1):87-90.