Study of aluminum nitride precipitation in Fe- 3%Si steel

Abstract

For good performance of electrical steels it is necessary a high magnetic induction and a low power loss when submitted to cyclic magnetization. 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.

Quantitative and Qualitative Evaluation of Non-Metallic Inclusions in High-Silicon Steel after Hot Rolling

“…On the aluminum nitride formation, Al + N = AlN, the stoichiometry relation between nitrogen (N) and aluminum (Al) contents on the precipitate formation is given by: 26.98 Al N 14.01  [14] comparing the amount of oxides in each sample in relation to the oxygen content and also the Al/N ratio, it can be observed that the heat with the highest Al/N ratio also had the highest amount of oxide inclusions, while the heat with the Al/N ratio most similar to the stoichiometrically had the lowest amount of oxides (Fig. 20).…”

“…inclusions having a size close to the wall thickness of the magnetic domains (100-200 nm) have the greatest impact on coercivity and hysteresis losses, they have the greatest ability to pin to the walls of the magnetic domains [11][12][13]. in the production of electrical steels, precipitates such as alN, Mns or cus play a special role and are used as grain growth inhibitors [14]. The strong affinity of aluminum for oxygen and nitrogen in the Fe-Al-O and Fe-Al-N system in the steel favors the formation of high-melting Al 2 O 3 and AlN inclusions.…”

Texture Intensity in Grain-Oriented Steel in the Main Stages of the Production Cycle

“…The sulfides precipitate during the hot rolling process. The aluminum nitride particles are formed during hot rolling and annealing process [17]. As is generally known, the grain size, the texture, precipitations and the internal stresses, and their distribution across the sheet thickness determine the magnetic properties of the FeSi materials, i.e., the magnetization behavior and the magnetic losses.…”

Effect of hot band annealing on inclusions, texture, and magnetic properties of 2.97%Si-0.59% Al non-oriented silicon steel

“…To meet these, there is an urgent need to develop the non-oriented silicon steel with low losses at high frequencies and low deterioration of the magnetic induction. The core loss and magnetic induction depend on the ferrite grain size, crystallographic texture, and precipitates in steels [1][2][3][4][5]. In order to reduce core losses at high frequencies, reducing eddy current loss by reducing the thickness and increasing the resistivity is the most effective method [6,7].…”