The most successful texture control has been achieved in the production of grain oriented silicon steels. This paper reviews the historical background and current knowledge of texture control for ensuring the high performance of the Goss oriented silicon steel sheets. Special emphasis is placed on the important contribution of textural and microstructural inhomogeneities to perfect secondary recrystallization of the {110}‹001› oriented grains, in particular, in the production of high permeabieity grade products through the single stage cold rolling process. The texture control of grain oriented silicon steels involves the control of local inhomogeneities in texture and microstructure: both potential nuclei of secondary recrystallization and matrix as the favorable surrounding for growth of the nuclei should be optimally provided throughout the processing route. Discussion includes (1) how the {110}‹001› oriented grains occur in the primary recrystallization matrix, (2) what qualifies the {110}‹001› oriented grains for viable nuclei of secondary recrystallization, and how they can grow at the expense of surrounding grains for perfection of secondary recrystallization, (3) how the {110}‹001› oriented potential nuclei originate and survive in the processing, (4) how the texture and microstructure can be controlled in the production of grain oriented silicon steels for improved performance, and (5) what are the main differences between the single and two stage cold rolling routes in terms of the texture control.

View full abstract

This paper reviews some new techniques for rapid analyses of domain and grain structures of grain oriented silicon steel. It is focussed on nondestructive techniques which can be applied on coated sheets. Closer discussions are given for colloid, SEM, and field scanning techniques as well as for a method which applies magnetotactic bacteria for the visualization of domains.

View full abstract

Highly efficient electric arc furnace process for continuous melting and smelting reduction was developed.
The corrected power consumption in which the reduction heat of iron oxide in the pellets was estimated as the equivalent heat for the melting of iron was improved with decreasing degree of metallization of the charged pellets. This improvement of the power consumption could be attributable to the enhancement of mixing in the bath by CO boiling due to the reduction of residual iron oxide in the pellets.
The apparent reaction rates of the bath components were estimated by considering their dilution curves.

View full abstract

The activity of iron in the Fe–Ta and Fe–Nb alloys at 1 873 K was determined by means of the Knudsen cell mass spectrometry. A modified internal standard method was employed, in which a piece of pure iron foil placed on the sample surface in the Knudsen cell served as the internal standard material. The ion intensity of iron from the foil was first measured at several temperatures before the alloy sample and the foil melted together. The ion intensity from pure solid iron thus obtained was extrapolated to give ion intensity from pure liquid iron at higher temperatures. The temperature of the sample was then raised to form uniform liquid alloy and the ion intensity of iron from the alloy was measured. The activity of iron in the alloy was determined by comparing the ion intensities from pure iron and from alloy.
The activities of Ta and Nb were derived from that of iron by integrating the Gibbs-Duhem equation. The activity coefficients of Ta and Nb in the infinitely dilute solution with liquid pure metal as the standard state were also calculated. The interaction parameters were determined. These results were compared with those of elements adjacent to Ta and Nb in the periodic table.
Invariant reactions appeared in the Fe–Ta binary alloy system at high temperature were investigated by employing the ion intensity thermal analysis, in which the ion intensity represented the temperature of the sample. Heat treatment and metallographic study was also carried out for the identification and composition determination of phases.

View full abstract

Diffusion-controlled sintering is discussed from thermodynamic and kinetic points of view and sintering rate equations are derived by regarding the overall change in the free energy of a material being sintered as driving force of diffusion. This new approach is much simpler than the conventional one and it enables us to derive the rate equations without knowing local chemical potential fields. The kinetics of the diffusional shape change of pores in the sintering aggregate is also formulated. On the basis of the derived rate equations, new criteria are proposed for the change in sintering stages. The results of the present theoretical analyses are compared with previous experimental results. Reasonable agreement between them is found.

View full abstract

The nature of heterogeneous deformation bands and the mechanism of Goss texture formation have been studied in the process of cold rolling and annealing of 3%Si–Fe (111)[112] single crystals. After cold rolling, two kinds of shear bands are observed. Wide shear bands (type I) make an angle of 35° to the rolling direction in longitudinal section, whereas narrow shear bands (type II) have an angle of 17° Rotations of crystallite orientations within the shear bands occur in the direction predicted by theory, however, the angles of the bands cannot be satisfactorily rationalised at present. The fine recrysallized grains nucleated along shear bands of type I have preferentially Goss orientation with a small dispersion (±10°) along TD//[110], whereas those nucleated within the type II bands have approximately twice as large an orientation spread. Following the nucleation along shear bands, recrystallization takes place by growth into the surrounding matrix.

View full abstract

Structure and mechanical properties of austenitic Fe–(20 and 30)Mn–(0 to 7) Al alloys in the temperature range between 77 and 295 K have been investigated in relation to the occurrences of phase transformation and deformation twinning. Additions of aluminum to the 20 wt% Mn alloys significantly decreased the γ→ε transformation temperature. The yield stress of these alloys increased with increasing aluminum content, whereas the strain hardening of them decreased. This tendency is prominent at low temperatures. In the 30 wt% Mn alloys the yield stress and strain hardening were almost identical regardless of aluminum contents. Additions of aluminum strongly suppress the γ→ε transformation and give birth to the occurrence of deformation twinning. Calculated stacking fault energy based on a regular solution approach shows that the austenitic Fe–Mn–Al alloys which have the stacking fault energy approximately larger than 20 erg/cm² favor the deformation twinning leading to the increase in low temperature ductility.

View full abstract

In order to characterize the Lake Erie Works hot strip mill, Stelco Steel, two grades of steel (C-Mn and Nb) were subject to torsional simulation. The flow stresses and rolling loads are considered in this report. The microstructural behaviours of the two grades are compared in a separate publication. As anticipated, for long interpass times, the T_nr temperature (temperature of no-recrystallization) can be clearly established only for the Nb steel, the other grade under-going nearly full softening, i.e. recrystallization, at all temperatures. By contrast, for short interpass times of the order of 2 s, typical of the strip mill, there is little pass-to-pass strain accumulation in either steel. In the temperature range 1 020 to 920°C, static recrystallization is largely responsible for the hight degree of interpass softening in the C-Mn steel. In the case of the Nb steel, because of solute effects, the short interpass times do not permit much conventional recystallization. Instead, softening is brought about mostly by dynamic and post-dynamic recrystallization. This is possible because there is considerably less Nb(CN) precipitation during the short interpass times than under reversing (plate) mill conditions. The decreased level of precipitation in the Nb steel, followed by the initiation of dynamic recrystallization, leads to lower rolling loads in the strip mill for this grade than in the plate mill at the same rolling temperatures.

View full abstract

In the production of Ni–Zn alloy electroplated steel sheets, the concentrations of Ni²⁺ and Zn²⁺ ions in the plating bath are necessary to be controlled. An automatic on-line analyzer has been developed for the process control. The on-line analysis system consists of a sampling system and an energy-dispersive X-ray fluorescence analyzer. The plating process solution is continuously supplied to the X-ray fluorescence analyzer through the sampling system form the plating trays. The concentrations of the Ni²⁺ and Zn²⁺ ions are determined from the intensities of Ni, Zn, Fe and S fluorescent lines. The intensities of the S and Fe lines are measured for interelement correction. The intensity of the S line is easily measured after a path in air with the energy-dispersive X-ray spectrometer. The S line is excited by chromium, and the Ni, Zn and Fe lines are by tungsten X-ray source, for obtaining a higher excitation efficiency. The analysis can be completed within 8 min. The analytical accuracies on the production line were 0.77 g/l for Ni²⁺ and 0.48 g/l for Zn²⁺ ion.

View full abstract

The Ni–Zn electroplated steel sheet is used as a car body material because of its high corrosion resistance. On production of this sheet, the coating weight and Ni content of the alloy coating are necessary to be controlled to ensure the quality of the products. An on-line X-ray fluorescence analyzer has been developed for the determination of the coating weight and Ni content of the alloy coating. The features of the analyzer are summarized as follows:
(1) The analysis is carried out full automatically.
(2) X-ray intensities are measured by a detector (ionization chamber) with an Fe filter and the other with a Ni filter.
The coating weight and the Ni content are calculated from the intensities measured by the two detectors.
(3) This analyzer has been operated for seven years without any trouble.

View full abstract