Daniel Ruiz

Magnetic properties of high Si steel with variable ordering obtained through thermomechanical processing

Alloys with a Si content of 4.2 and 5.4 wt % Si were produced to investigate the effect of increasing the Si on the materials processing and properties and to understand the effect of the order–disorder phenomenon on its magnetic properties. Different cooling rates after hot rolling were applied: Slow cooling from 780 °C to room temperature in 26 h, air cooling and water quench, followed by cold rolling until 0.5 to 0.7 mm thickness. Magnetic properties were measured after pickling and annealing at 950 °C for 2 h. 57 Fe Mossbauer spectroscopy was used to study the effect of thermomechanical cycles on the ordering phenomena. It was noticed that the quenched samples have the highest values for the magnetic polarization, while slowly cooled samples have the lowest, for the power losses higher values are obtained for the quenched materials. The highest values for the polarization in the quenched samples were explained as a result of a higher B2 ordering.

Plane strain compression of high silicon steel

Abstract A series of plane strain compression tests were conducted at room temperature on a high silicon steel to study the behaviour of this material owing to the similarity of this test with rolling. The tests were performed in a specially designed machine able to control the strain rate profile and the amount of deformation. The material was cast and hot rolled to a thickness of 4 mm from which the experimental samples were machined. Plane strain compression tests were carried out at three constant rates of strain (0·01, 0·1 and 1 s−1) up to four levels of equivalent strain (0·15, 0·30, 0·45 and 0·60). 57Fe Mössbauer spectroscopy analyses indicate that the degree of order of the material decreases with the amount of deformation until a strain of 0·45 is achieved; a further increase in strain augments the order of the material. It is found that the strain rate sensitivity close to yielding is negative, but converts to positive once a stain of ∼0·04 is surpassed. Microstructural analyses of deformed samples show that deformation is by twinning and shear. Electron backscattered diffraction analyses indicate that twinning occurs only at an early stage of deformation within grains with {111} planes parallel to the plane of deformation. Deformation twinning takes place in all grains at later stages of deformation.

Influence of Ordering Phenomena on the Thermomechanical Processing of High‐Si Electrical Steel Studied by Mössbauer Spectroscopy

Fe‐Si alloys with Si‐contents up to 14 at.%Si (7.6 wt.%Si ) were produced by conventional casting and hot/cold rolled with different conditions of temperatures, pass reductions and cooling rates. The obtained thickness of the final sheet was between 0.5 and 0.7 mm for Si‐steel up to 10 at.%Si (5.5 wt.%). Mossbauer spectroscopy was used to characterize the order evolution with the Si‐content and the thermomechanical processing of the material. A new fitting program was developed for this purpose due to the known complexity of the Fe‐alloys spectra. Results show that there is never complete disorder, i.e. binomial distribution of the atoms, whatever the Si‐concentration is. Moreover, a clear tendency towards D03 ordering is observed. The obtained long‐range order parameters prove a patent increase of the D03 order above 7 at.%Si (3.6 wt.%) which can be associated to the observed brittleness beyond this Si‐amount. Concerning the relationship between order and thermomechanical processing, no big effect was fo...

Effect of atomic order on the electrical and magnetic properties of Fe/sub 100-x/Si/sub x/ (6</spl times/<14) alloys

The influence of order phenomena on the electrical and magnetic properties of a series of Fe-Si alloys is analyzed. Electrical resistivity and hysteresis loop measurements are performed on alloys after different thermal treatments, including annealing and quenching from several temperatures. Mo/spl uml/ssbauer spectroscopy and differential scanning calorimetry were used to characterize both the type of order existing in the alloys and the order-disorder transition temperature. For the highest quenching temperature, the highest magnetic losses are measured due to internal stresses and disordering induced during quenching. High electrical resistivity is obtained by high-temperature quench only when the Si content was over 10.6 at.%. This occurred due to an order-disorder transition, which reduces the B2 degree of order present in the alloy. On the other hand, disordering appears to be detrimental for the excess losses due to the creation of antiphase domain boundaries.

Influence of ordering phenomena on the magnetostriction of high Si alloys for electrical applications

The present work attempts to assess the influence of order phenomena on the magnetostriction of high Fe–Si alloys for electrical applications. The magnetostriction of high silicon electrical steels in the range of 4to6wt.% Si was studied regarding the effect of processing and thermal treatment. In addition, power losses and saturation magnetization measurements were performed and Fe57 Mossbauer spectroscopy was used to evaluate and quantify the degree of order.

Effect of atomic order on the electrical and magnetic properties of Fe/sub 100-x/Si/sub x/ (6 < x < 14) alloys

The influence of the degree of atomic order on the electrical and magnetic properties of Fe-Si alloys with different Si-contents was determined. Five different Fe-Si alloys with Si-contents ranging from 6-14 at%Si were annealed from 500 to 1100/spl deg/C for 2 h and then quenched in water in order to develop different degrees of order. /sup 57/Fe Mossbauer spectra were obtained in order to determine the type and degree of order. Differential scanning calorimetry was performed to detect the disorder/order transition. The disordering in the samples greatly increase the electrical resistivity. Moreover, losses increase with annealing temperature due to the generation of internal stresses and/or creation of disordering.

Order in high silicon electrical steel characterized by Mossbauer spectroscopy

Summary form only given. High silicon steel containing up to 6.5 wt.% Si is known as an excellent soft magnetic material, but it is difficult to process by a conventional thermomechanical (TM) route because of its extreme brittleness, which is usually associated to order/disorder phenomena. Recent research has shown that a properly adapted TM-route can be followed to produce steel sheet provided the ordering reaction can be avoided. Mossbauer spectroscopy has been used to determine the degree of ordering present at different levels of these TM-processing routes.