Aluminium Nitride Precipitation in Fe-3%Si Steel

Abstract

A fine dispersion of precipitates is a key requirement in the manufacturing process of Fe-3%Si grain oriented electrical steel. In the production of high permeability grain oriented steel precipitate particles of copper and manganese sulphides and aluminium nitride delay normal grain growth during primary recrystallization, causing preferential growth of grains with Goss orientation during secondary recrystallization. The sulphides precipitate during the hot rolling process. The aluminium nitride particles are formed during hot rolling and the hot band annealing process. In this work AlN precipitation during hot deformation of a high permeability grain oriented 3%Si steel is examined. In the study, transfer bar samples were submitted to controlled heating, compression and cooling treatments in order to simulate a reversible hot rolling finishing. The samples were analyzed using the transmission electron microscope (TEM) in order to identify the precipitates and characterize size distribution. Precipitate extraction by dissolution method and analyses by inductively coupled plasma optical emission spectrometry (ICP-OES) were used to quantify the precipitation. The results allowed to describe the precipitation kinetics by a precipitation-time-temperature (PTT) diagram for AlN formation during hot rolling.

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

“…The precipitation behavior of second phase particles, like AlN or MnS, has significant effects on grain size and magnetic properties of silicon steels by inhibiting grain growth and affecting the domain wall motion [1,2]. The common precipitates in conventional production process of electrical steel have been studied by Jenkins [3] and Alcantara [4] et al In recent years, many researchers are interested in the fabrication of silicon steel by strip casting technology because of its near-net-shape casting and technical advantage. Liu [5] studied the microstructure and texture of as-cast silicon steel strip and the relative factors.…”