Yunbo Xu

Effect of Cold Rolling Process on Microstructure, Texture and Properties of Strip Cast Fe-2.6%Si Steel

The use of twin-roll strip casting for the preparation of non-oriented silicon steel has attracted widespread attention in recent years, but related reports are limited. In this study, both one- and two-stage cold rolling with three intermediate annealing temperatures were employed to produce strip cast non-oriented silicon steel. The evolution of the microstructure and texture through the processing routes and its effect on magnetic properties were studied. Compared with one-stage rolling, two-stage rolling increased the in-grain shear bands and the retention of Cube texture in the cold rolled sheets, thereby promoting the nucleation of favorable Goss and Cube grains and restraining the nucleation of harmful {111}<112> grains. With the increase in intermediate annealing temperature, the η-fiber texture in annealed sheets was gradually enhanced, and the average grain size was increased, leading to significant improvement of magnetic properties.

Effects of hot-rolling reduction on microstructure, texture and magnetic properties of high silicon steel produced by strip casting

Non-oriented Fe-7.1wt.% Si as-cast strips were produced by twin-roll strip casting process. Then the as-cast strips were hot rolled with different reductions, followed by warm rolling and final annealing. The microstructure, texture evolution and magnetic properties were investigated in detail. The texture of hot rolled sheets with 40% reduction showed strongest {001} texture, whereas the dominated texture was turned into {110} and {110} as the reduction was increased to 56% and 68%. After warm rolling and annealing, the average grain size was decreased firstly and then increased with an increase in hot rolling reduction. In the case of 40% hot rolling reduction, the recrystallization texture was dominated by strong γ ( //ND) texture. With an increase in hot rolling reduction, the γ texture was gradually weakened while α ( //RD) texture was enhanced. In addition, relatively stronger {100} texture was presented in the sheet of 68% hot rolling reduction. The highest B50 value attained was 1.66 T and the lowest P10/400 was 24.26 W/kg at a reduction of 56%.

Precipitation Behavior of 1.3%Si Non-oriented Silicon Steels During Strip Casting Process

In this work, the precipitation behaviors of 1.3%Si non-oriented silicon steel during the sub-rapid solidification process under different melt superheat were investigated using scanning electron microscope and transmission electron microscope, based on strip casting process. The results showed that the precipitates of as-cast strips were dominated by coarse AlN, and MnS particles were seldom observed. The mean size of AlN particles rapidly increased from 75 to 1060 nm, and the volume fraction increased from 0.028 to 0.069%, when the melt superheat increased from 20 to 70 °C. Besides, the precipitation quantity in the center layer of as-cast strip was obviously more than the surface layer. According to the different solubility ability in the liquid and ferrite matrix, Al or N elements tend to segregate during the sub-rapid solidification process, which is attributed to the nucleation and coarsening of AlN. On the condition of low melt superheat, the solidified layers suffered from hot deformation from the solidification end point to the nip point, which provided additional nucleation sites for precipitates and can be attributed to fine particles size. In addition, different heat conductivity and hot deformation degree in various thickness layer resulted in inhomogeneous distribution of particles through the thickness of as-cast strips.

Role of Annealing Time in Thin-Gauge Non-oriented Silicon Steels Processed by Strip Casting

Cold-rolled Fe–2.6%Si sheets of 0.20 thickness prepared by strip casting and two-stage cold rolling were annealed for different time. The microstructure and texture of all samples were investigated by optical microscopy, electron backscattered diffraction and X-ray diffraction to illustrate the effect of annealing time on the development of texture and magnetic properties. The sample in the initial stage of complete recrystallization was characterized by strong η, γ and α component. Goss grains possessed size advantage, and γ grains showed the highest number density. Subsequently, γ-fiber and α-fiber was gradually weakened, whereas η-fiber always predominated the texture. However, with further increase in annealing time, γ-fiber was significantly enhanced and being a dominant component as a result of growth selection of γ grains. Ultimately, the magnetic induction gradually decreased after an increase over time, whereas the core loss displayed a continuous decrease. Texture development with annealing time in the present study could be explained by orientated nucleation mechanism and orientation pinning effect.

Evolution of Microstructures and Texture of 1.3%Si Non-Oriented Electrical Steel in the Twin-Roll Strip Casting Process

In this work, the influence of casting rollers which had different thermal abilities on microstructure and texture of 1.3%Si non-oriented electrical steel was investigated in a twin-roll strip casting process. The cooling capacity of copper rollers is stronger than that of steel ones, and the difference of heat transfer capacities had an obviously effect on the solidification structure and texture. The results show that the microstructures with an average grain size of ~60–200μm and ~120–320μm could be respectively obtained in strips under both copper rollers and steel rollers conditions when the melt superheats were in the range of 30 to 50°C There was a relatively random and diffuse texture in strips under copper rollers condition compared to the one under steel rollers condition, which lead to the occurrence of relatively weak Goss, Cube and γ-fiber in the annealed sheet.

Modeling of Microstructure Evolution and Mechanical Properties during hot-strip Rolling of Nb Steels

An integrated metallurgical model was developed for Nb steels to predict the microstructure evolution and mechanical properties during the hot-strip rolling and cooling process. On the basis of the industrial data, the transformation kinetics, strength, and elongation rate were evaluated for different chemical compositions and processing parameters. The yield strength and tensile strength increase with increasing Nb content or decreasing finishing temperature. The bainite distributed in finer ferrite matrix, which is produced at relatively low coiling temperatures, can greatly increase the strength of steel, especially tensile strength, thereby decreasing the yield ratio. A reasonable agreement was found between the predicted and measured results. It indicates that the present models can be used to simulate the actual production process.

Mechanical Property Prediction of Hot-rolled Strip by Intelligent Correction Network

Based on physical metallurgy and neural network, intelligent prediction models of mechanical property in hot strip mill were developed. A new idea of intelligent correction about mechanical property was proposed. Physical metallurgy models calculated the base value, and the deviation of predicted value with measured value under different technology conditions was obtained by neural network. The simulation indicates that predicted and measured results are in good agreement and the relative error is very low. For 88% yield strength and 98 % tensile strength results, the error is within plusmn3 %, and for 80 % elongation results it is within plusmn6%