Abstract: In the present work, the nano-sized carbide precipitates in three high-strength low-alloy (HSLA) steels with different rolling thicknesses (12 and 25 mm) and chemical composition (Ti and Nb-Ti steels) were obtained by using nondestructive electrolysis extraction technology and their precipitation behaviors were discussed. The results show that a large number of M3C precipitates, which are needle- and flat-shaped, and MC precipitates, which are quadrilateral, exist in the HSLA steel. The average sizes of M3C precipitates are smaller than those of MC precipitates. The average size of M3C and MC precipitates rises with the increase of rolling thickness, while their mass fractions remain stable. Besides, the average sizes of M3C and MC precipitates in the surface decrease by 25% as compared to those in the center. Furthermore, after adding a small amount of Nb element, a (Ti, Nb)C complex carbide is formed, which substantially increases the mass fraction and average size of MC precipitates.
Authors: Kaiping Du, Yueguang Yu, Shuting Zhang, and Ji Shi
Keywords: High-Strength Low-Alloy Steel, Nano-Sized Carbide Precipitates, Rolling Thickness, Nb Element