An Investigation of the Formability, Mechanical Properties and Microstructure of Niobium and Niobium-Titanium Microalloyed Steels

Yıl 2020, Cilt: 6 Sayı: 2, 102 - 107, 31.07.2020

Ali Sancaktar Sebahattin Kırtay , Aliye Arabacı

Öz

Microalloyed steels are widely used in the automotive sector due to their formability and strength. One example application is rim manufacturing where the cost of wheel is expected to be low.

In this study, formability, microstructure and mechanical properties of low carbon steels containing Niobium and Niobium-Titanium as microalloying elements were investigated.

The measurements showed that the tensile strength of non-alloyed steel was 433.5 MPa, the yield strength was 292.6 MPa, the tensile strength of Nb alloyed steel was 489 MPa and the yield strength was 385.4 MPa. These values indicate that the tensile strength increase of about 12 % and the yield strength increase of 24 % were obtained. Also for Nb-Ti added steel, the tensile strength was 591.3 MPa and the yield strength was 462.6 MPa. These correspond to 27 % increase in the tensile strength and 37 % increase in the yield strength. Furthermore, elongation values were measured as 27.6 % in non-alloyed steel, 32 % in Nb-added steel, and 28 % in Nb-Ti added steel. In the microstructure analysis, the grain size of Nb and Nb-Ti added alloys were found to be approximately 50 % smaller than the grain size of unalloyed steel.

These results indicated that we achieved high elongation values and improved mechanical properties for Nb and Nb-Ti added steel. Furthermore, we managed to hold the elongation value at 27.7 % while achieving higher yield and tensile strengths and formability by adding a small amount of Nb-Ti to the steel.

Anahtar Kelimeler

Formability, Microalloys, Steel

Kaynakça

• [1] C. J. Van Tyne, D. K. Matlock, and J. G. Speer, “Microallyed Forging Steels” International Forging Congress, (2008) 189-197.
• [2] M. Hajisafari, S. Nategh, H. Yoozbashizadeh, A. Ekrami, “Improvement in Mechanical Properties of Microalloyed Steel 30MSV6 by a Precipitation Hardening Process” J. of Iron and Steel Research. (2013)66-73, DOI: 10.1016/S1006-706X(13)60100-4
• [3] Xiao-Huai Xue, Yi-Yin Shan, and Song-Nian Lou, “Microstructure Characteristic of Low Carbon Microalloyed Steels Produced by Thermo-Mechanical Controlled Process” Materials Science &Engineering A. 438-440 (2006) 285-287, DOI: 10.1016/j.msea.2006.02.064
• [4] M. Niikura, M. Fujioka, Y. Adachi, A. Matsukura, T. Yokota, Y. Shirota, and Y. Hagiwara, “New Concepts for Ultra Refinement of Grain Size in Super Metal Project” J. Mater. Process. Technol. 117 (2001) 341-346, DOI: 10.1016/S0924-0136(01)00800-7
• [5] E. Esenera , E. Sönmeza , M. Özsoyb and M. Firatb,∗ “Determining Springback Behavior of High-Strength Steels via Channel Forming Process” Acta Physica Polonica A. 132 (2017)1010-1012, DOI: 10.12693/APhysPolA.132.1010
• [6] V. Onar, S. Aslanlar and N. Akkaş, “Effect of Welding Current on Tensile–Peel Loading of Welding Joints in TRIP 800 and Micro-Alloyed Steels in Resistance Spot Welding” Acta Physica Polonica A 132(2017) 822-824, DOI: 10.12693/APhysPolA.132.822
• [7] H. Xie, L-X. Du, J. Hu and R.D.K. Misra, “Microstructure and mechanical properties of a novel 1000 MPa grade TMCP low carbon microalloyed steel with combination of high strength and excellent toughness” Mater. Sci. Eng. (2014) A612 123-130, DOI: 10.1016/j.msea.2014.06.033
• [8] E. Paul DeGarmo, J T. Black Ronald, A. Kohser, Materials and Process in Manufacturing, Ninth Edition, 2003 John Wiley & Sons, Inc.
• [9] European Committee for Standardization, “Metallic materials - Tensile testing - Part 1: Method of test at room temperature” (ISO 6892-1), 2016.
• [10] Danijela A. Skobir, “High-Strength Low-Alloy (HSLA) Steels” Materials and Technology. 45 (2011) 4 295-301.
• [11] H. Najafi, , R. Jafar, S. Asgari, “As-cast mechanical properties of vanadium/niobium microalloyed steels” Materials Science and Engineering. (2008) A 408 1-7, DOI: 10.1016/j.msea.2007.08.057
• [12] Hoda S. El-Faramawy, Saeed N. Ghali, Mamdouh M. Eissa, “Effect of Titanium Addition on Behavior of Medium Carbon Steel” Journal of Minerals and Materials Characterization and Engineering. (2012) 11 1108-1112, DOI: 10.4236/jmmce.2012.1111118
• [13] C. L. Davis, M. J. Balart, M. Strangwood, “Fracture Behaviour In Medium-Carbon Ti–V–N And V–N Microalloyed Ferritic-Pearlitic And Bainitic Forging Steels With Enhanced Machinability” Materials Science and Engineering A. 328 48-57, DOI: 10.1016/s0921-5093(01)01679-3