STEEL PLATE AND METHOD OF PRODUCING SAME

Abstract: provided is a steel plate having high strength of ts≥690 mpa, excellent low-temperature toughness, low yield ratio, and low acoustic anisotropy. a steel plate comprises a chemical composition containing certain elements in certain amounts with a balance consisting of fe and inevitable impurities. in a microstructure at a depth position of � of a plate thickness from a plate surface in a plate thickness direction, a ferrite fraction is 5% to 95% and a martensite austenite constituent fraction is 1% to 30% with residual microstructure consisting of tempered martensite and/or bainite, an average aspect ratio of crystal grains that are regions surrounded by large-angle grain boundaries with an orientation difference of 15 degrees or more is less than 2.0, and a number density of crystal grains having an equivalent circular diameter of more than 30 �m among the crystal grains is 250/mmor less.

Inventor(s): Yuya SATO, Shunichi TACHIBANA, Yoshiaki MURAKAMI

CPC Classification: C22C38/08 (ALLOYS (flints ; treatment of alloys , ))

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