Inclusions in High-Strength and Bearing Steels. Their Dependence on Processing Variables and their Effect on Engineering Properties.
Final technical rept. 15 Jun 67-15 Aug 69,
COLT INDUSTRIES INC PITTSBURGH PA CRUCIBLE RESEARCH CENTER
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The relationship between quantity and type of nonmetallic inclusions and critical mechanical properties was determined for the high-strength steels, 4340 and 300M, and the bearing steel, 52100, through the use of a quantitative television microscope QTM, an ultrasonic volume inspection system and various identification methods. For the structural steels, transverse reduction of area was the property most influenced by inclusion content. Fatigue and impact properties were also affected, though to a lesser degree. Plane strain fracture toughness was little affected by inclusion content and, in fact, longitudinal and transverse properties were substantially the same in direct contrast to reduction of area, impact and fatigue properties. KIc is thus not a meaningful parameter for quality control measurement of the high-strength structural steels. Rolling contact fatigue life improved markedly with reduced inclusion contents for 52100 steels. Inclusion statistics showed that improved cleanliness was obtained in ascending order of 1 electric furnace air-melted, 2 Dortmund-Horder degassed, 3 vacuum-arc-remelted, 4 electro-slag remelted and 5 vacuum-induction remelted steels. Studies on the latter two melting methods were made on 1000-lb heats, whereas the remaining data were obtained on large-scale production heats. Author
- Metallurgy and Metallography