API STEEL PLATE FOR LINE PIPE AND METHOD FOR MANUFACTURING THE API STEEL PLATE

摘要

PURPOSE: An API steel sheet for a line pipe and a manufacturing method thereof are provided to enable application of the API steel sheet to an oil pipeline installed in a cold region. CONSTITUTION: A method for manufacturing an API steel sheet for a line pipe is as follows. A steel slab is heated to a temperature of 1210-1280°C and extracted at a temperature of 1140-1160°C. Rough rolling is implemented in a condition where the reduction ratio per pass of the final three passes is 6.0-7.0% below the austenite recrystallization temperature(Tnr). Finish rolling is implemented at a rolling initiation temperature of 915-945°C. Cooling implemented to lower the temperature of the steel sheet from 710-770°C to 450-500°C at a cooling rate of 10-60°C/sec.