THICK STEEL PLATE HAVING THICKNESS OF 50 MM OR MORE WITH EXCELLENT LONG BRITTLE CRACK ARRESTABILITY, METHOD FOR MANUFACTURING THE SAME AND METHOD AND TESTING APPARATUS FOR EV ALUATING LONG BRITTLE CRACK ARRESTING PERFORMANCE

摘要

The present invention provides the following: a thick steel plate in which in the tip shape of the long brittle fracture stopping area, in relation to a region having from 1/4 to 1/10 of the sheet thickness from the surface of the steel plate, a region comprising 20% of the sheet thickness of the central region of the sheet thickness forms a recess at least as long as the thickness of the plate in relation to the direction in which the long brittle fracture propagates, and the X-ray intensity ratio of the (211) plane or the (100) plane of the rolled surface region of at least 20% of the sheet thickness region in the central region of the sheet thickness is 1.5 or greater and the X-ray intensity ratio of the region having 1/4 to 1/10 of the sheet thickness or of the (110) plane of the rolled surface having 3/4 to 9/10 of the sheet thickness is 1.3 or higher; a steel plate manufacturing method wherein steel of specific constituent elements, after being heated to 900 to 1350°C, is rolled at a surface temperature of 850 to 1000 °C and a cumulative reduction ratio of 10% or greater, and then when the steel plate surface temperature is 550 to 800 °C after completion of rolling at a specific surface temperature and internal temperature at a one pass rolling reduction of 7% or greater and a cumulative reduction ratio of 50% or greater, is hot rolled; and a method for evaluating long brittle fracture propagation stopping performance and an evaluation apparatus for the same.