Texture and Deformation Behaviour through Thickness Direction in Strip-cast 4.5wt% Si Steel Sheet.

Abstract

Fe-4.5wt%Si strips were made using vertical type twin-roll strip casting process, and the microstructure and texture of as-cast strips were studied through thickness direction. The heterogeneity of the texture and microstructure through thickness direction was observed. Between the subsurface layer and the middle layer, Goss texture, with the subgrains of low angle grain boundary was evolved by the shear deformation. In the center layer, major rolling and recrystallization textures with minor solidification texture were evolved.The deformation behavior during strip casting process was simulated by hot rolling of Al alloy with temperature gradient through thickness direction. And the shear and normal strains distribution through thickness direction were measured. The heterogeneity of the texture and the microstructure through thickness direction resulted from the strength gradient, which originated from the temperature gradient through thickness direction.KEY WORDS: Fe-4.5wt%Si; Twin Roll Strip Casting; deformation behavior; texture; hot rolling strength gradient; temperature gradient..given in Table 1. The schematic diagram of the twin-roll strip caster is shown in Fig. 1. Hole-type nozzle was positioned at the center of the tundish. Molten metal was supplied from an induction furnace to the tundish by using a temperature-controlled ladle. Specimens for metallographic examination were etched with Nital (2 vol% Nitric acidϩ98 vol% ethanol) reagent. The microstructure of the specimens was observed at the transverse direction by using optical microscope and EPMA. At the normal direction, subgrain boundaries in the subsurface layer were investigated by using transmission electron microscope. Texture MeasurementThe texture variation of the as-cast strip was investigated through thickness direction. The position through thickness direction can be used by a parameter s, defined as sϭ2a/d, where a and d are the distance from the center layer of strip and the thickness of the strip, respectively. The parameter s is called the normalized thickness. To analyze quantitatively the texture of the strip, three incomplete pole figures, {110}, {200}, {211}, were measured in the range of the polar angle a from 0°to 70°with Co Ka 1 radiation in the Seifert D3000 with PTS goniometer. Samples for pole figures measurement were etched at room temperature in a solution of 90 ml H 2 O 2 and 10 ml HF for the stress relieving from the mechanical polishing. ODF was calculated from the measured pole figures by WIMV method.10) The orientation of the subgrain in subsurface layer was investigated by the EBSD, which was operated by Link Opal system at JEOL 6300 SEM. Temperature Gradient Hot Rolling Simulationduring Strip Casting Process The deformation behavior during strip casting was simulated by hot rolling of Al alloy with temperature gradient through thickness direction, called the temperature gradient hot rolling simulation. Figure 2 shows a schematic diagram of the temperature gradient hot rolling simulation. The curved plate of Al-0.1wt...

The Eftects of Superheating on Texture and Microstructure of Fe-4.5wt%Si Steel Strip by Twin-roll Strip Casting.

“…These subgrains were formed by hot deformation and dynamic recovery during strip casting. 15) However, in the case of the strip which was cast in the condition of superheat 30°C, subgrains were not observed in the subsurface layer.…”

“…Region I was an initial rapidly solidified layer, which remained in undeformed state after solidifying on the surface of the roll during strip casting. 15) Region II was hot deformed in the casting condition of 20°C superheat, but region I was not deformed during strip casting and {100}͗uvw͘ solidification texture was maintained, because region I was the rapid-cooled hard surface. 8,15) In the case of superheat 20°C, region II of equiaxed dendritic layer was observed from the subsurface to the middle layer (sϭ0.8-0.2) and region III became narrower than that of the case of superheat 30°C.…”

“…The subsurface layer and middle layer of the strip could be shear deformed when the solidification end point was located above the roll nip point during strip casting. 15) Columnar dendrites (region III) were grown in the preferred crystallographic directions of ͗100͘ in cubic crystals, which was closest to the heat flow direction. 16) Figures 6(e) and 6(f ) show that the major a and g-fiber and minor solidification texture of {100}͗uvw͘ evolved in the center layer.…”

The Thickness Gradient of Microstructure and Mechanical Property in an As-cast Thin Steel Slab

“…As confirmed by Park,5) Raabe 17) and Choi,18) there is an apparent texture gradient in the through-thickness direction of as-cast stainless steels and Fe-Si steels. The inhomogeneity of microstructure and texture was found to be detrimental to the final surface quality and plastic anisotropy of steel strips.…”

Recent developments in semiprocessed cold rolled magnetic lamination steel

“…Because of this, it is unlikely that Caststrip will be able to produce high-quality CRML steel with the current technology. If Nucor can develop a process to cast aluminum killed steels, Caststrip could revolutionize electrical steel manufacture because the fast cooling rates allow novel CRML compositions to be produced that are metallurgically clean and uniquely textured [21].…”