Ivan Petryshynets

Effect of VC Nano-Inhibitors and Dynamic Continuous Annealing on the Magnetic Properties of GO Steels

We report on novel approach for the abnormal growth of Goss grains that employs the system of VC nano-precipitates in combination with a phenomenon of the deformation induced grain growth. The laboratory slab of grain oriented steel was subjected to hot rolling with reduction of the thickness of sheet to 2.2 mm. The influence of coiling temperature on the distribution of VC particles was analyzed by TEM. The obtained results have confirmed the presence of VC nanoparticles with a typical size of 5-15 nm located preferentially in the vicinity of grain boundaries. Subsequently, the hot rolled strips were subjected to the cold rolling with the reduction ε ~ 84%, followed by primary recrystallization, temper rolling and final annealing in dynamic conditions at 1050 °C. This procedure led to evolution of the sufficiently strong {110} 〈001〉 Goss texture, which follows in the soft magnetic behavior comparable to that obtained in the longtime heat treated industrial GO steels. Thus, the proposed approach allows reach the equal materials quality at significantly shortened manufacturing time and lower energy consumption as compared to the conventional process of GO steel fabrication.

Magnetic Properties of Temper Rolled NO FeSi Steels With Enhanced Rotation Texture

In the present work, we have used an adjusted temper rolling process for development of particular textures {100} <; (0vw) in nonoriented (NO) FeSi steels. The main idea behind the improvement of soft magnetic properties relies on deformation induced grain growth and heat transport phenomena promoting the preferable formation of columnar grains with desired orientation. The vacuum degassed NO steels with silicon content 1% wt. taken from industrial line after final annealing were chosen as an experimental material. A columnar grained microstructure with pronounced intensity of rotating cube and Goss texture components was achieved during a dynamic final annealing. The obtained microstructural and textural state of sample leads to a significant reduction of coercivity. The coercivity values measured in DC and AC (50 Hz) magnetic field decreased from 70 A/m to 16 A/m and from 179 A/m to 65.4 A/m, respectively.

Effect of Microsecond Pulse Laser Modification on Electromagnetic Properties of Grain Oriented Silicon Steel

A microsecond pulsed laser beam was used to local magnetic domain modification of electrical grain oriented silicon steel. It was carried out using three different laser pulse regimes: a single pulse laser regime, a multipulse laser regime and a multipulse laser regime with modulation of laser pulses. The laser processing variables were pulse energy and and number of pulses. The samples were tested for nanohardness and coercivity before and after laser treatment. Light optical microscopy, scanning electron microscopy and magnetic force microscopy were used to observe the cross-sectional profile, surface of the samples, and magnetic domain visualization, respectively. The local laser treatment of grain oriented silicon steel surface has been studied in terms of its influence on the magnetic domains and coercivity. It was found that laser-modified samples showed coercivity improvement in comparison to the non-treated samples. The most significant improvement in coercivity was obtained in the modulated multipulse regime and negligible improvement in the single pulse laser regime. Three main effects responsible for the observed improvement were identified, namely: magnetic domain refinement, influence of number of laser pulses and shape of laser HAZ profile. The present work highlights on differences in the magnetic domain structure, microstructure of the laser modified material and basic electromagnetic and mechanical properties. In present study, the pulse laser surface processing was presented as a useful energy efficient alternative to other techniques e.g. mechanical scribing, electrical discharge scribing, plasma jet scribing, etc. The refined magnetic domains in electrosteels are responsible for the observed low coercivity, which indicates perspective application of the investigated laser modified steels in the power transformer cores with lower core losses.

Study of Microstructure and Texture Evolution in Grain-Oriented Steels Via Coercivity Measurements

The relationship between microstructure, phase transformation, and texture in grain-oriented (GO) steels on the one side and the magnetization processes on the other side is very complex. To contribute to a better understanding of this dependence, the magnetic measurements were carried out on the steels in combination with a microstructure, texture, and phase analysis. It was shown that the coercivity measurement technique can be successfully applied to reflecting of main microstructure and texture changes of GO steels. The mentioned changes taking place during application of particular thermomechanical treatments. Moreover, this measurement method also can be applied to detect phase transformations in the materials containing sufficient carbon content. Within this paper, it is shown that the measurement of coercivity is a powerful tool that can be successfully used to reflect such important phenomena as microstructure and texture development in the GO steels.

Abrasive wear resistance of modified X37CrMoV5-1 hot work tool steel after conventional and laser heat treatment

Abstract The effects of two conventional heat treatments and one innovative processing by laser surface remelting of modified X37CrMoV5-1 tool steel on its abrasion wear resistance were investigated. Conventional heat treatments consisted of quenching from 990 °C, individually followed by two different tempering treatments to achieve secondary hardness either at 520 °C or 560 °C. Laser surface remelting was performed using optimized parameters of continuous laser beam scanning mode. The results showed that the highest wear resistance was obtained for almost carbide-free, surface remelted microstructure with the highest hardness due to microstructural refinement and martensitic transformation hardening. The observed differences in wear resistance among individual material states are discussed in relation to their microstructures, hardness, and wear mechanisms characteristics.

Magnetic losses reduction in grain oriented silicon steel by pulse and continuous fiber laser processing

The present paper shows the impact of different laser scribing conditions on possible reduction of magnetic losses in grain oriented electrical steel sheets. The experimental Fe-3%Si steel was taken from industrial line after final box annealing. The surface of investigated steel was subjected to fiber laser processing using both pulse and continuous scribing regimes in order to generate residual thermal stresses inducing the magnetic domains structure refinement. The magnetic losses of experimental samples before and after individual laser scribing regimes were tested in AC magnetic field with 50Hz frequency and induction of 1.5T. The most significant magnetic losses reduction of 38% was obtained at optimized conditions of continuous laser scribing regime. A semi quantitative relationship has been found between the domain patterns and the used fiber laser processing.

Microstructure Modification of Tool Steel X38CrMoV5-1 by Fibre Laser

In the present work, we investigate the influence of laser radiation on the evolution of microstructure and wear resistance of X38CrMoV5-1 tool steel in hardened and tempered condition. The microstructure of the laser surface hardened zone consists of fine and coarse grained carbides (M23C6, M7C3, MC or M2C) which are dispersed within martensite matrix. On the other hand, the laser melted microstructure is characterized by martensite, retained austenite and fine carbides precipitated in the inter-dendritic zone. The laser surface affected zone microstructure exhibits the enhanced hardness in the range from 857 to 775 HV in comparison with quenched and tempered conditions (720-655 HV) and decreases from the surface to the soft zone with a typical hardness of 530 HV. The wear resistance of the laser treated samples is investigated by “ball on disc” method, which shows a significant improvement as compared to that in quenched and tempered condition.

Columnar Grain Growth with Enhanced Rotation Texture in Temper Rolled NO Silicon Steels

The present work investigates texture evolution stages in vacuum-degassed non-oriented electrical steels. The main idea behind the improvement of soft magnetic properties relies on deformation induced grain growth phenomena and heat transport phenomena promoting the preferable formation of columnar grains with so called cube crystallographic orientation {100}<0vw>. In order to achieve the desired orientation with appropriate microstructure state from magnetic properties point of view, we have used an adjusted temper rolling process at elevated temperature and subsequent dynamical annealing in laboratory conditions.

Nanoindentation Measurements in Non-Oriented Silicon Steel at Elevated Temperatures

The present work deals about nanoindentation measurements between particular grains with various orientation at room and at elevated temperatures ( 100°C, 200°C, 250°C). Nanohardness measurements were carried out in non-oriented silicon steel with columnar microstructure, in order to evaluate local variation of work hardening as function of crystallographic orientation. The dependence of texture on the applied condition was studied by EBSD (Electron Backscatter Diffraction) analysis. Hardness was shown to decrease with increasing temperature in each of individual grains. The differences of hardness values were observed also between particular grain orientations.

Differential Scanning Calorimetry and Metallographic Analysis of Fe-Si Electrical Steel

The microstructure development in cold rolled electrical steel under dynamic heat treatments was subjected to investigation. Significantly distinguish types of microstructures were obtained in the investigated steels confirming the different character of grain boundary motion. Application of annealing temperature within two phase region (austenite+ferrite) leads to abnormal grain growth in silicon steels. Moreover, in the optimum temperature range, there was a particular temperature leading to the most optimal microstructure and texture[1]. The effect of Si content on the phase transition temperature of the electrical steel (0.6, 1, 2.5, 2.9 % Si) was studied by using differential scanning calorimetry (DSC) analysis. The result indicated that DSC analysis could be used to detect the shift temperature of phase transformation in the electrical steel with different Si addition. DSC have been used in thermochemical studies and as complementary to the study of phase transformation. It can be used as a compliment to optical and electron microscopy.