Grain Refinement of C–Mn Steel to 1 μm by Rapid Cooling and Short Interval Multi-pass Hot Rolling in Stable Austenite Region

<i>In Situ</i> EBSD Analysis on the Crystal Orientation Relationship between Ferrite and Austenite during Reverse Transformation of an Fe-Mn-C Alloy

“…The following two things are indicated: i) At Interface 1, the orientation relationships quite close to the K-S relationship with Δθ of 3 or less is satis ed for seven γ grains. ii) When the orientation relationships within 10 in Δθ are taken into account 6) , six γ grains have such orientation relationships at Interface 2 and Interface 3 in addition to the K-S relationship at Interface 1. By analyzing all 154 γ grains measured in the present study, the frequency of γ grains satisfying Conditions i) and ii), that is the double K-S relationship with the tolerance angle of 3 and 10 , was 53%.…”

“…The mechanism of variant selection has been intensively studied on the γ→α phase transformation in the cooling process [1][2][3][4][5][6][7] because the eventual texture after cooling has a signi cant in uence on the various mechanical properties of the nal products. The crystal orientation selection rule during the reverse phase transformation (α→γ) in the heating process is also important for controlling the microstructure in the steel making process.…”

“…Tomida et al proposed the variant selection model for α−γ transformation based on the orientation relationship at multiple interfaces with different α grains showing the texture memory effect. They assumed that the orientation of γ during reverse transformation is selected in order to satisfy the Kurdjumov-Sachs (K-S) relationship 23) or near K-S relationship at two or more interfaces with adjacent α grains at the same time 6,7) . They call this hypothetical relationship the double K-S relationship.…”

Phase Transformation from Fine-grained Austenite

“…Since application of such concepts to the commercial steel production line still accompanies large difficulty, some modification such as short-interval multiple rolling has been attempted. 4) It is known that ferrite grain size decreases linearly with decrease in austenite grain size in continuously cooling of recrystallized hot rolled sheets for a wide range of austenite grain size between 20 to 250 mm. 5) Therefore, another route proposed to produce ultrafine grained ferrite structure is transformation from ultrafine grained austenite structure.…”

Transformation Texture in Hot-rolled Steel Sheets and Its Quantitative Prediction

“…In this article, the methods to calculate the transformation textures are briefly reviewed. Then the recent method [5][6][7] that the authors and their co-workers have proposed to predict the transformation texture in hot-rolled steel sheets is described, in which the variant selection [8][9][10][11][12] that we call 'the double KS relation' is taken into account.…”