Formation of the Goss orientation near the surface of 3 pct silicon steel during hot rolling
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I.
INTRODUCTION
THE surface texture of hot rolled 3 pct silicon iron commonly used for grain oriented electrical steel is characterized by a strong (110) [001] orientation, the so-called Goss orientation, which has a significant influence on the nucleation and growth of (110) [001] secondary grains by way of structure memory, 1'2 even after the cycle of cold rolling and annealing in the cold rolling processes. Nevertheless, there have been a limited number of investigations on the mechanism of the formation of the Goss orientation during hot rolling. The presence of a (110) [001] orientation in the hot rolled sheet of silicon steel has so far been reported by many investigators since N. P. Goss first pointed it out in 1941 3,4 T. Matsuoka showed the formation of a (110) [001] orientation at the surface of 3 pct silicon steel after single pass hot rolling of 40 pct and 60 pct reduction in thickness at 700 to 1000 ~ 5 P. N. Richards investigated the preferred orientation of commercially hot rolled 3 pct silicon steel at various depths below the surface and observed the strongest aggregation of a (110)[001] orientation near the surface. 6 V. Ya. Gol'dshteyn et al. also investigated texture formation in 3 pct silicon steel hot rolled at various temperatures and observed that a strong (110)[001] orientation was formed in the polygonized zone next to the surface layer consisting of recrystallization grains. 7 All of these studies were carried out on polycrystal samples, and no investigation has been reported on the correlation of the initial orientation to the texture formation of 3 pct silicon steel during hot rolling. This investigation has been undertaken to clarify the influence of hot rolling conditions, such as rolling temperature, rolling speed, reduction rate, lubrication, and initial orientation on the formation of a (110)[001] orientation in the surface layer.
Y. SHIMIZU, Chief of Electrical Steel Laboratory, Mizushima Research Department; Y. ITO, General Manager, Research Planning Department; and Y. IIDA, Senior Research Associate of Kobe Laboratory, Light FlatRolled Products, Research Department, are with Technical Research Division, Kawasaki Steel Company. This paper is based on a presentation made at the symposium "Physical Metallurgy of Electrical Steels" held at the 1985 annual AIME meeting in New York on February 24-28, 1985, under the auspices of the TMS Ferrous Metallurgy Committee. METALLURGICALTRANSACTIONS A
II.
EXPERIMENTAL PROCEDURE
This investigation consists of two parts. In the first part the effects of hot rolling speed, hot rolling temperature, and reduction rate per pass on the surface texture of hot rolled sheet were studied. The specimens used in the experiment were vacuum-melted 3 pct silicon iron ingots of 100 Kg in weight, the chemical compositions of which are listed in Table I. After the preliminary hot rolling of the ingot, the slabs of 50 mm in thickness were hot rolled to 3.0 mm thick in various conditions after heating at 1330 ~ for 30 minutes. Three levels of hot rolling spe
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