PRODUCTION METHOD OF EXTRA THICKNESS MARTENSITIC STAINLESS THICK STEEL PLATE EXCELLENT IN INNER QUALITY CHARACTERISTIC, AND EXTRA THICKNESS MARTENSITIC STAINLESS THICK STEEL PLATE EXCELLENT IN INNER QUALITY CHARACTERISTIC

摘要

PROBLEM TO BE SOLVED: To provide a production method of an extra thickness martensitic stainless thick steel plate excellent in an inner quality characteristic; and an extra thickness austenitic stainless thick steel plate excellent in the inner quality characteristic.SOLUTION: A production method of an extra thickness martensitic stainless steel palate of at least 80 mm thickness includes the following processes. 1: A process in which a slab by continuous casting is heated at 1010°C-1150°C, both ends of a crosswise direction of the slab is performed by forging draft from the crosswise direction, a slab width is shortened by at least 300 mm, and these both ends are thickened. 2: A process in which forging is performed to draft in a slab thickness direction by a draft ratio exceeding 10% at a temperature of at least Atransformation point (830°C). 3: A process in which the slab is heated at a range of 1090°C-1150°C, and rolling is performed by a working condition in which the total draft ratio in which a forging draft ratio and a rolling draft ratio in the 2 are summed is at least 20% and less than 60%. The extra thickness martensitic stainless steel plate is that a number of a porosity of a 0.1 mm&phgr;-1.0 mm&phgr; radius in a slab rolling vertical direction full width, and a board thickness of 1/2 thickness ±10 mm position is at most 10/100 mm.