PRODUCTION OF HIGH PURITY STEEL EXCELLENT IN COLD WORKABILITY AND FATIGUE CHARACTERISTIC

摘要

PROBLEM TO BE SOLVED: To obtain excellent cold workability and fatigue characteristics by melting a steel ingot by a vacuum arc remelting method (VAR method) for one or >= two times, controlling the contents of C, Si and Mn as final steel ingot components to specified ranges and moreover controlling the content of Al by secondary ion mass spectrometry to the specified value. SOLUTION: In the final steel ingot components, the content of C is controlled to, by mass, 0.3 to 1.0%, Si to 0.1 to 2.5% and Mn to 0.1 to 1.5%, and also, the content of Al is controlled to 2.3 to 6 ppm. It is also preferable that, as the final steel ingot components, the content of Co is controlled to 0.05 to 1.0%, and Cu to 0.05 to 1.0%. In the case of applying VAR melting for one or >=two times, by controlling the [Al] in the final steel ingot to 2.3 to 6 ppm, Al2O3 inclusions are sufficiently reduced and decomposed, by which high purity steel small in harmful inclusions can be obtd. In the case the [Al] in the steel exceeds the upper limit value, Al2O3 inclusions are precipitated by oxidation reaction, and in the case it is the one below the lower limit value, the reduction decomposing effect of the inclusions is insufficient.