Cold-rolled Silicon Steel Research Articles

Effect of Preheating on the Mechanical Workability Improvement of High-Strength Electrical Steels during Tandem Cold Rolling

Cold-rolled silicon steel strip products are widely used as the main soft magnetic components in cores of electrical motors, generators, and transformers. In the case of rotating electrical machines, the so-called non-oriented electro-technical steels are normally applied. They are characterized by a similar behaviour to the induced magnetic field found in all sheet plane directions. The kind of soft magnetic alloys that defined herein not only possess an isotropy of electromagnetic properties, but also high mechanical strength; such alloys are called high-strength electro-technical (HSET) steels. These commercially produced HSET steels contain a high silicon content in the range of 3–4 wt.%. However, if the silicon content exceeds 3%, the machinability of Fe–Si alloys is dramatically reduced and they become much more brittle as a consequence. According to this, regular hot band brittle damage occurs during cold deformation at a high-speed tandem rolling mill. In accordance with these reasons, the production of thin high-strength silicon steel grades using the traditional methods of cold rolling deformation is extremely problematic and it is characterised by a high degree of steel sheet mechanical damage. In this scientific work, the effect of preheating hot-rolled strips on their mechanical workability improvement during tandem cold rolling was investigated. The results of this study indicate that the cold rolling of hot bands at elevated temperatures increases their resistance to brittle failure and mechanical plasticity. Moreover, the mathematical simulation clearly demonstrates that residual stress is distributed relatively homogeneously across the thickness of samples, which were cold rolled at 100 °C in contrast to the same ones deformed at room temperature.

Investigation of the main factors affecting the magnetic properties of silicon steel sheets by comparing three kinds of silicon steel

As an important magnetic material, silicon steel is widespread used in various motors, generators, relays and transformers. It is of great significance to explore the factors affecting the magnetic properties of non-oriented silicon steel. This paper introduces the production process of 50W800, 50W600 and 35W550 non-oriented silicon steel, and compares their magnetic properties, observes the microstructure of silicon steel sheet under hot rolling, cold rolling and annealing three technological states, analyzes the influence of sheet thickness, composition, microstructure and impurity on the magnetic properties of non-oriented silicon steel. The results can be summarized as follows: (1) The magnetic properties of the silicon steel sheet can be improved to a certain extent by reducing the thickness of the silicon steel sheet.(2) Increasing silicon content in a certain range can reduce core loss of silicon steel. (3) After annealing, the grain size of cold rolled silicon steel sheet becomes larger, the defect of grain decreases, the loss of iron core decreases, and the finished silicon steel sheet with good magnetic properties is obtained.

Edge drop control of cold rolled silicon steel strip based on model predictive control

The closed-loop edge drop control system of cold rolled silicon steel strip is a typical time-delay control system, and the measurement time-delay has a great influence on the stability of the control system. In order to improve the stability and control accuracy of the closed-loop edge drop control system, an edge drop control model based on model predictive control for cold rolled silicon steel strip is proposed in this paper. In order to improve the accuracy of control system model parameters, the priori efficiency coefficients of work roll shifting (WRS) for edge drop control are determined by rolling experiments, and the online optimization of priori efficiency coefficients is realized by process data. On this basis, the time delay analysis of control system is completed by equal flow method, and a closed-loop control strategy for edge drop control is developed by introducing predictive aging value into model predictive control. Finally, trajectory smoothing is used to complete the smooth output of predicted control, and then improve the dynamic characteristics of the closed-loop edge drop control system. Theoretical analysis, simulation experiments and application show that the model prediction-based edge drop control method has higher accuracy and faster response characteristics compared with conventional control method, and can realize high-precision edge drop control process of cold rolled silicon steel strip.

Computer aided design of amorphous alloy permanent magnet motor

Amorphous alloy is a kind of double green soft magnetic material with high saturation magnetic induction, low coerce, low loss, high stability and other excellent properties. Instead of cold rolled silicon steel sheet, it can reduce the loss and improve the efficiency of the motor to a great extent. Combined with the characteristics of amorphous alloy and based on the design theory of permanent magnet motor, this paper uses the MATLAB software to write the electromagnetic design program of amorphous alloy permanent magnet synchronous motor, which has the characteristics of visual parameter input, rapid electromagnetic calculation, and convenient man-machine interaction. An example is given to verify the reliability of the program.

Influence of profile indicators of hot-rolled strip on transverse thickness difference of cold-rolled silicon steel

In order to evaluate the transverse thickness difference of cold-rolled strips according to the information of hot-rolled strips and scientifically guide the setting of the indicators of the hot-rolled silicon strip, the influence model about the relation of the transverse thickness difference of cold-rolled strip to the profile indicators of hot-rolled strip is established in this paper based on simulation results. The transverse thickness difference of cold-rolled strip predicted based on the influence model have strong correspondences to the measured data. Based on the influence model and the statistical analysis of the measured data, the control criterion of the profile indicators of hot-rolled silicon steel according to the requirements for the transverse thickness difference of cold-rolled strip are finally recommended. The simulation results show that the transverse thickness difference of cold-rolled strip is quadratic nonlinearly related to the wedge and crown of hot-rolled strip. The influence model and statistical data analysis indicate that reducing the edge-drop of hot-rolled strip is beneficial to restrain the transverse thickness difference of cold-rolled strip.

Research on the Formation Mechanism of Emulsion Spots on the Cold-Rolled Silicon Steel Surface

For the cold-rolled silicon steel strip lubricated with emulsion, the typical oil spot defects always can be found on the surface of rolled strip. The oil spot are parallel to the rolling direction. In the present study the micro-structure of oil spot defects was investigated by several surface analysis techniques, including LEXT ols4000 laser scanning confocal microscope, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS). The chemical compositions of the oil spot defects were analyzed by EDS. The results showed that the surface quality of the rolled non-oriented silicon steel was affected strongly by emulsion stability. The emulsion stability decreased with the increasing content of CL-. When the particle size of emulsion was larger, the lubricity of the emulsion deteriorated. Furthermore, there were some emulsions which contain miscella on the strip steel surface. The emulsions existed in the confined areas where the plate shape defects formed. The majority of its water was evaporated with the increasing of temperature and time. The oxides and residual emulsions could be found on the surface strip steel, which originated from the oxidation reaction between vapors and silicon steel surface. Eventually, the reaction produced some oxides (Fe3O4, FeO, Fe2O3, SiO2, CoCr2O4, NiCr2O4, Fe-Cr) and other by-products. In addition, the emulsion spots area were easier to suffer corrosion than the normal area under the same conditions.

Investigation on the Corrosion Behavior of Emulsion on the Cold-Rolled Silicon Steel Surface

The silicon steel was cold rolled by using an oil-in-water emulsion for lubricating its surfaces. Oil in water (O/W) emulsion is a lubricant composed of oil in the form of droplets suspended in water. This paper mainly researched on the new emulsion which was prepared by changing the compound proportion between antioxidant 2, 6-Di-tert-butyl-p-cresol (T501) and antirust agent petroleum sodium sulfonate (T702). The corrosion behavior of the emulsion was investigated by weight loss and electrochemical methods. The mechanisms for inhibition of corrosion synergism between T501 and T702 in base oil were studied. The results show that the antirust agent (T702) can effectively forming a layer of adsorption film on the rolled strip surface and this adsorption film can segregate strip surface from air and water. The antioxidant (T501) can capture oxygenic free radical (•OH, RO•, ROO•) and carbon free radical and reduces the trend which emulsion occur oxidation reaction under high temperature and high pressure. The antioxidant plays a minor role in inhibition of corrosion synergism. The results show that the best compound proportion content is 4% antioxidant (T501) and 8% antirust agent (T702), which can effectively increase the anticorrosion effect of emulsion. Meanwhile, the self-corrosion potential and self-corrosion current of the sample is minimal and the self-corrosion current is 1.0226×10-7A/cm2.

Analysis of white-stripe defects of non-oriented silicon steel rolled surface with emulsion

For non-oriented cold-rolled silicon steel lubricated with oil-in-water (O/W) emulsion, the typical white-stripe defects can always be found on the rolled strip surface. The white-stripe defects are parallel to the rolling direction. In this paper, an experimental investigation and mechanical analysis were carried out to study the white-stripe defect formation during cold strip rolling using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The emulsion lubricating properties and surface topography of wear scars are discussed. It is considered that the poor lubricating properties of the emulsion are a key factor for surface defect formation on the rolled strip surface. The surface roughness R a of the white-stripe area is 31.2% larger than that of the normal area. The results show that when the tribological properties of commercial emulsion are poor; it will lead to generate surface defects on the rolled non-oriented silicon steel surface. Furthermore, emulsions were embedded into the surface defects of the rolled strip. When the emulsion residue agglomerates together, white-stripe defects appear on the rolled strip surface.

Simulation Study on Core Material of Weak DC Current Sensor

ZnMn ferrite, cold-rolled silicon steel, permalloy and nanocrystalline alloy can be used as magnetic cores of current sensors. And based on these four materials’ inherent characters of electromagnetic, this paper presents closed loop simulation model of them using Ansoft which is a finite element analysis software. In simulation, the measuring currents are set to DC currents ranging from 0 to 1mA. And different amplitudes of variation of currents are set for each material. The simulation of each material produces 280 sets of data and with these data a series of curves of magnetic field changing with currents can be plotted using Matlab. The simulation results show that permalloy and nanocrystalline alloy have good characters of electromagnetic and they are suitable for detecting weak DC currents. When these two materials are used as magnetic cores of sensors, the theoretical detecting accuracy can be up to 0.001mA, meanwhile, detecting accuracy of ZnMn ferrite is about 0.1mA to 0.01 mA.

Effect of Cold-Rolled Thickness Reduction Degree on Characteristics of Hydrogen Diffusion in Silicon Steel

The characteristic of hydrogen uptake and diffusion in the cold-rolled silicon steel was investigated by electrochemical hydrogen permeation technique performed under different cathodic charging current density and cold-rolled thickness reduction degree. The results indicated that anodic permeation current density increased with increasing cathodic charging current for the specimens. Moreover, the anodic steady state permeation current density and the solubility increased with an increase in the cold-rolled thickness reduction degrees. The breakthrough time of hydrogen in the specimens was shortened with increasing thickness reduction degrees, and the value of the hydrogen diffusivity decreased gradually with increasing thickness reduction degrees.

Study on the Application of Shear Modified GTN Model to Small Punch Test

As an important non-standard test technology, the testing result of small punch test(SPT) is largely influenced by the experiment condition. In the research of SPT, an appropriate mechanical constitutive model of material is much needed. The shear modified GTN model proposed by NAHSHON is implemented into ABAQUS via user defined material subroutine VUMAT to study the material fracture behavior at various stress triaxialities. The undamaged elastic-plastic mechanical properties of the cold rolled silicon steel are obtained by the tensile test. The damage evolution parameters of void nucleation are determined by experiment data of tensile test combined with a large number of simulations. The shear modified parameter that characterizes the contribution of void distortion to damage evolution is identified by the comparison of the results of pure shear test simulations and the experiment data. The shear modified GTN model is used to simulate the small punch test. The results show that, as the void distortion is taken into account in damage evolution, the prediction results of the shear modified GTN model is much more consistent with experiment data than the original GTN model. It comes to the conclusion that the shear modified GTN model can reveal the failure mechanism of material better in intrinsic, and is a better choice to apply in the study of small punch test.

Microstructure Evolution and Grain Boundary Characteristics of Oriented Silicon Steel during Primary Recrystallization in a Pulsed Magnetic Field

The effects of a 2 T pulsed magnetic field primary annealing process on microstructure evolution and grain boundary characteristics in two-stage cold-rolled silicon steel were examined. Pulsed magnetic annealing increased grain size through the application of relatively smaller intensity of magnetic fields (2 T), compared to steady magnetic annealing. The effect of increasing grain size may be attributed to the magnetic acceleration effect of boundary motion under magnetic pulse conditions. Pulsed magnetic annealing may serve to enhance the relative intensity of the {111} component and decrease the frequency of low-angle misorientations. Repeated magnetostriction induced by pulsed magnetic field applications may accelerate overall dislocation motion. These findings suggest that pulsed magnetic fields require relatively lower intensities than steady magnetic fields to achieve superior results, providing a potentially viable alternative for industrial annealing processes for electrical steels.

Effect of pulsed magnetic field annealing on the microstructure and texture of grain-oriented silicon steel

The effect of pulsed magnetic primary annealing on the microstructure and texture of two-stage cold-rolled silicon steel is investigated. Specimens are annealed at 700°C for 1h under a 1T pulsed magnetic field along different directions with respect to the sample coordinate system. Crystallographic orientation and grain size are identified by analyzing electron backscattered diffraction pattern. The effects of magnetic field treatment are related to the magnetic field direction. Based on the anisotropy energy of ferromagnetic material during magnetic annealing, a hypothesis is proposed. All of the experimental results in this work support the proposed model.

Through-Thickness Shear Strain in Silicon Steel under Asymmetric Rolling

Through-thickness shear strain variation with speed/radius/friction ratio in cold rolled silicon steel under different asymmetric rolling modes was analyzed by finite element method (FEM). Cold rolling textures were also investigated quantitatively to correlate with the calculated shear strain. With increasing speed/radius/friction ratio, shear strain distribution under differential-speed and differential-radius rolling exhibits similar characteristic in contrast to differential-friction rolling. Unidirectional shear strain develops through sheet thickness when asymmetric speed and radius ratio exceeds 1.125, whereas it does not appear even at friction ratio of 1.5. Shear strain distribution dependent on asymmetric rolling modes can be well understood by forward and backward slip zones as well as roll pressure as a function of speed/radius/friction ratio.

Effect of Hot-Rolled Microstructure on the Recrystallization Texture of Cold-Rolled Non-Oriented Electrical Steel

With the help of orientation distribution function (ODF) analysis, experiments of different hot band grain microstructure 0.33% silicon steel were cold-rolled and annealed in the laboratory，to study the effect of the microstructure hot-rolled steel strip for cold rolled non-oriented silicon steel microstructure and texture of recrystallization annealing. The results show that hot rolled microstructure on cold rolled Non-Oriented Electrical Steel cold-rolled sheet evolution of texture and recrystallization have important influence, the quiaxed grain structure of steel by cold rolling and recrystallization annealing, the recrystallization speed than the fiber grain-based mixed crystals recrystallization fast , With the equiaxed grains made of cold rolled silicon steel after annealing the {110}<UVW> texture components was enhanced and {100}<uwv> texture components weakened. Different microstructure condition prior to cold rolling in the recrystallization annealing process the texture evolution has the obvious difference, the equiaxial grain steel belt cold rolling and annealing, has the strong crystal orientation. This shows that the equiaxed grain when hot microstructure is detrimental to the magnetic properties of cold-rolled non-oriented silicon steel to improve and increase.

Through-thickness shear strain control in cold rolled silicon steel by the coupling effect of roll gap geometry and friction

Through-thickness shear strain distribution in cold rolled non-oriented silicon steel under different roll gap geometries and friction coefficients was analyzed by finite element method (FEM). Cold rolling textures were also investigated quantitatively to validate the calculated shear strain distribution. The results showed that both direction and magnitude of shear strain through thickness depend sensitively on the two rolling parameters. The coupling effect of roll gap geometry and friction was satisfactorily explained based on their contributions to shear strain and the involved mechanisms. A shear strain distribution diagram (SSDD), which can clearly characterize the shear strain state with roll gap geometry, friction and through-thickness position as variables, was proposed to serve as a convenient tool for through-thickness shear strain control.

Microstructure and Texture of Shear Bands in Cold Rolled Silicon Steel Single Crystals of Goss Orientation

An initially Goss-oriented ({110}<001> preferred crystal orientation) FeSi single crystal was cold rolled up to 89 % reduction in thickness. The microstructure and texture of shear bands, which develop at strains higher than 70 %, were investigated by the EBSD (electron backscatter diffraction) technique. The texture components within and ouside of the shear bands are the two symmetrical {111}<112> orientations and the {110}<001> orientation. We conclude that crystallographic slip is the deformation mechanism that is active both within and outside of the shear bands.

Effect of Magnetic Field During Secondary Annealing on Texture and Microstructure of Nonoriented Silicon Steel

Magnetic fields are said to influence texture and microstructure evolution of ferrous alloys. The objective of this work is to investigate the effect of a magnetic field applied during secondary annealing on texture evolution and grain size of a nonoriented silicon steel sample. Temper cold rolled silicon steel samples were annealed under the same conditions with and without the magnetic field. The final grain size was the same for both annealing conditions. The application of a magnetic field affected texture development by increasing the strength of the Goss orientation and decreasing the intensity of grains {111} oriented parallel to the normal direction of the sheet.

Effect of magnetic field applied during secondary annealing on texture and grain size of silicon steel

Temper cold rolled silicon steel samples were annealed with and without an applied magnetic field. The final grain size was the same for both annealing conditions. Application of a magnetic field affected texture development by increasing the strength of the Goss component and decreasing the intensity of the gamma fiber.

Extraordinary mechanical bond between magnesium silicate ceramic coating and grain-oriented silicon steel

Routine observation of magnesium silicate coatings on transformer steel showed them to have a remarkable ability to withstand deformation without delaminating, contrary to experience with other glassy or crystalline coatings on steel. Out-of-specification materials may produce poorly bonded coatings. A full-scale examination of the steel-coating process was undertaken to discover the keys to this difference and to contribute to the design of improved magnesium oxides.These observations have been made possible by the development of a Br-methanol solution technique by which the steel may be dissolved away from the oxide or silicate coating. Observations have been carried out by TEM, AEM, SEM, and EDS.Before decarburization, the cold-rolled silicon steel has a thin (0.5 to 1.0 micrometter) silicon-rich coating, comprised of amorphous silica with minor fayalite (Fe2SiO4) (see Fig. 1).