Investigation of Continuous Cooling Transformations and Microstructures in a Low Carbon Ti-Nb Bearing Microallyed Steel by Means of Dilatometry and Metallography

Document Type : Original Articles

Authors

• asiye sadat mousavi mahvelati
• seyed sadegh ghasemi banadkouki
• mahdi kalantar

Yazd University, Yazd, Iran

10.22067/ma.v28i1.32846

Abstract

In this investigation, continuous cooling transformations and microstructures have been studied in detail in a low carbon Ti-Nb bearing microalloyed steel by means of dilatometry, metallography and hardness measurements. The results indicate that when the cooling rate is greater than 1˚C/s, the dilatation curve is associated with a major dilatation at relatively low transformation temperatures, which is consistent with the martensitic phase transformation. For a cooling rate between 0.2-0.8˚C/s, the dilatation curve is also characterized with a uniform single transformation over the martensitic and bainitic phase transformation temperature range. However, as the cooling rate is reduced to less than 0.2˚C/s, the dilation curve is characterized with a quite variable double stage transformation which is associated with the ferrite and bainite transformation products. These results suggest that the bainitic and martensitic phase transformations are developed with a similar displacive mechanism, while ferrite is formed by a diffusional mechanism.

Keywords

• Low Carbon Low Alloy Steel
• Continuous Cooling
• Dilatometry
• Metallography
• Ferrite
• Bainite
• martensite

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