ESTIMATION METHOD OF HIC SENSITIVITY OF STEEL MATERIAL AND MANUFACTURING METHOD OF HIGH STRENGTH THICK STEEL PLATE FOR LINE PIPE SUPERIOR IN ANTI HIC PERFORMANCE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an estimation method of HIC sensitivity of steel material and a manufacturing method of high strength thick steel plate for line pipe superior in anti HIC performance using the same.SOLUTION: Mn concentration is analyzed on an area including a central segregation portion on a steel material and the results thereof are mapped. Defining a continuous region of the steel material where Mn is concentrated 1.3 times of Mn concentration Cof the steel material as a Mn segregation spot based on the analysis and mapping result, a major axis DL of the Mn segregation spot and a ratio of average Mn concentration Cof the Mn segregation spot to Mn concentration Cof the steel material (Mn segregation degree) C/Care examined. The distribution of Mn segregation spots where the product of DL(mm) and the Mn segregation degree C/Cexceeds 0.8 (mm) are calculated. When the number of Mn segregation spots found in a unit length of 100 mm is one or less in a width direction of the steel material, the steel material is evaluated as a steel material superior in anti HIC performance.