Characterization of precipitates in strip-cast 2.7%Si steel under different heat treatment conditions

State Key Laboratory of Rolling and Automation, Northeastern University, 110819 Shenyang, China

^a Corresponding author: e-mail: yunbo_xu@126.com

Abstract

A 1.5mm thickness as-cast Fe-2.7%Si strip was produced by twin-roll strip casting and the precipitates under different isothermal holding time (0.5 min–30 min) and cooling rates (1^∘/s–20 ^∘C/s) were investigated by thermal simulation experiment technology and electron probe micro-analyzer. The main precipitates in all specimens are AlN-MnS complex with a structure of core-edge. During isothermal holding, the number density of relatively large precipitates (≥ 0.3 μm) decrease with increase in time and the mean size of the small precipitates (≤150 nm) increases gradually. It can be attributed to the complicated interactions of dissolve, precipitation and coarsening behavior. For precipitates in strips cooling from 1380 ^∘C to 20 ^∘C, the mean size decreases continuously with increase in cooling rate because the corresponding growth rate and time of precipitates decrease. These results indicate that isothermal holding time and cooling rate have an important influence on size of precipitates in strip, which will be of great importance in optimizing properties of silicon steel.