Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Effect of rolling reduction rate/pass in controlled rolling on
the mechanical properties and texture of thick steel plate
Naoki TAKAYAMA*1, Shunichi TACHIBANA*1, Yoshiaki MURAKAMI*1*1 Steel Research Laboratory, JFE Steel Corporation, Kurashiki, Japan.

the total rolling reduction and finish-rolling temperature on texture
have been studied, and it has been found that texture develops as aresult of an increase in total reduction and the strength of the specificorientation changes depending on the finish-rolling temperature (Yutori,1979; Nishimura, 2014). However, few studies have focusedparticularly on the effect of the reduction rate/pass during controlled
rolling on texture formation.
In the field of shipbuilding steel, thick steel plates with arrestability
have been manufactured in recent years by utilizing texture, and as aresult, texture control technology has become an important issue.
Therefore, in this study, the effect of the reduction rate/pass duringcontrolled rolling on the mechanical properties of thick steel plates andits relationship with texture were investigated.

ABSTRACTIn the field of shipbuilding steel, thick steel plates with arrestability
have been manufactured recently by utilizing texture, and texture
control technology has become an important issue. In this study, thetensile strength, toughness and texture of specimens with different
rolling reduction rates (%) per pass (hereinafter, reduction rate/pass) inthe unrecrystallized temperature region were evaluated. Tensile
strength did not change regardless of the reduction rate/pass. Toughness
was improved by increasing the reduction rate/pass from 6.0 % to10.7 %, but was almost unchanged when the reduction rate/pass was_ __ _increased to 20.2 %. The strength of the (001) [110] and (112) [110]texture components, which contribute to arrestability, also increased
when the reduction rate/pass was increased from 6.0 % to 10.7 % but
decreased at 20.2 %. A reverse analysis for the texture of austenite
before transformation revealed that this decrease was due to theprogress of recrystallization at the higher reduction rate/pass. Thus, thisstudy clarified the importance of optimizing the reduction rate/pass for
improving mechanical properties and texture by controlling thereduction rate/pass.

EXPERIMENTAL PROCEDURE
A 140 mm thick steel ingot composed of Fe-0.05C-0.1Si-1.9Mn-Cu, Ni,Cr, Nb, Ti (mass%) was used. Non-recrystallization temperature (Tnr)of this steel is 943 °C (Bai, 2011). The ingot was heated at 1 080 °C for
1 h in an atmospheric furnace, and then rolled to a thickness of 126 mm
in the recrystallized temperature region, followed by rolling to a
thickness of 63 mm in the unrecrystallized temperature region. Thus,
the rolling reduction rate in the unrecrystallized temperature region wasconstant at 50 %, and the reduction rate/pass in unrecrystallized
temperature rolling was controlled by changing the number of rolling
passes. After rolling, accelerated cooling was applied to the steel plates
used as specimens.
The microstructure was observed by optical microscopy from the TD
direction at the center of plate thickness of the specimen. Thespecimens for the tensile test and Charpy impact test were taken fromthe center of plate thickness so that the longitudinal direction of thespecimens was parallel to the TD direction and the RD direction,
respectively. The texture was obtained by X-ray diffraction
measurement from the ND direction at the center of plate thickness.

KEY WORDS: Shipbuilding steel; Arrestability; TMCP; Texture
controlling

INTRODUCTION
Thick steel plates used in steel structures such as ships are required topossess toughness as well as strength, and TMCP is applied to obtaingrain refinement in order to achieve these properties. Texture is also
developed during the process by formation of a microstructure with anorientation relationship from deformed austenite. Since the texture
strongly affects the anisotropy of mechanical properties, texture
development and control have been studied extensively in the field ofautomotive steel sheets. In the field of thick steel plates, the effects of2877