EVALUATION METHOD FOR STEEL EXCELLENT IN ROLLING FATIGUE LIFE

摘要

PROBLEM TO BE SOLVED: To provide steel that is excellent in rolling fatigue life and is used for machinery components.SOLUTION: An evaluation method for steel excellent in rolling fatigue life comprises the steps of: defining steel that has an oxygen content not greater than 8 ppm in the steel, a sulfur content not greater than 0.008 mass% therein and non-metal inclusion having √Area not less than 20 μm and less than 100 μm detected per a steel volume of 1,000 mmby an ultrasonic flaw detection method and the number of pieces of the non-metal inclusion not greater than 3.5 as an evaluation object; setting a water distance that is a distance between a probe surface of an electronic scanning type array probe and a steel surface within a predetermined range when a parameter P is set as detection conditions of water immersion ultrasonic flaw detection using the electronic scanning type array probe; generating a line focus at a central portion of the steel by electronic focusing by the electronic scanning type array probe and further performing vertical flaw detection; and regulating the number of pieces of the non-metal inclusion having the √Area not less than 100 μm detected per a steel weight of 2.5 kg to be not greater than 1.5.