Effect of precipitates on grain growth in non-oriented silicon steel
- PDF / 676,558 Bytes
- 8 Pages / 584.957 x 782.986 pts Page_size
- 116 Downloads / 179 Views
Hefei Huang Shanghai Institute of Applied Physics, Chinese Academy of Sciences (CAS), Shanghai 201800, China
Shaobo Zheng and Jinglin You State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy & School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China (Received 30 September 2016; accepted 13 March 2017)
Precipitates and grain sizes in non-oriented silicon steel samples, which were hot-rolled (HR), continuously annealed (CA), and stress-relief-annealed (SA), were characterized using scanning electron microscopy (SEM) equipped with electron back-scattered diffraction. The average grain sizes of the HR, CA, and SA samples were 28, 46, and 46 lm, respectively. SEM observations revealed that the precipitates were mainly dispersed inside grains in the HR and the CA samples, but mainly at grain boundaries in the SA sample. The density of precipitates was highest in the SA sample and lowest in the HR sample. Precipitates at the grain boundaries, which were identified as manganese sulfides, were nearly spherical, their diameter ranging from 0.3 to 0.7 lm. We calculated the pining force exerted by grain-boundary precipitates and found that it outweighed the driving force of the grain growth that was controlled by boundary curvature. I. INTRODUCTION
Non-oriented silicon steel sheets are manufactured to provide specific magnetic properties and can be produced from Fe–Si or Fe–Si–Al alloys.1 The most desired magnetic properties are high permeability and low magnetic core loss, both of which depend on microstructure parameters, e.g., grain size, texture intensity, and precipitate density.2–5 It is well known that increasing grain size lowers the core loss since it reduces the area of grain boundaries which can restrain the movement and rotation of magnetic domains during magnetization.6 It is a classical method to control the grain size of electrical steels through governing the precipitation of fine particles.7–10 The nano-sized precipitates are harmful to magnetic properties of non-oriented silicon steel. It has been known that the fine sulfides can prevent the grain growth and increase the core loss of the non-oriented silicon steel sheet.11 The formation mechanisms of the sulfide produced in casting,12,13 oxide metallurgy,14,15 and steel semi-products16 had been investigated in the last twenty years. The grain growth inhibition by particles was first quantified by Zener, 17 who developed a simple model which described the pinning of grain boundaries by
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.115
immobile particles. Afterward, other models on the inhibition of recrystallization by precipitates formed from micro-alloying elements were presented.18,19 The hypotheses behind all these models are based on the concept that the grain growth will stop when the driving force is smaller than or equal to the pinning force.19–22 Particle pinning on grain growth has been exten
Data Loading...
