STEEL SHEET FOR CARBURIZATION HAVING EXCELLENT COLD WORKABILITY AND TOUGHNESS AFTER CARBURIZING HEAT TREATMENT

摘要

This steel sheet for carburization having excellent cold workability and toughness after carburizing heat treatment has a sheet thickness of 2-10 mm, a component composition containing specific amounts of C, Mn, Al and N with the balance made up of iron and unavoidable impurities, and a steel structure composed of ferrite and carbides. With respect to the ferrite, the number of ferrite crystal grains having an aspect ratio of 3 or less is 60% or more of the number of all ferrite crystal grains, and the average crystal grain size of all crystal grains is within the range of 3-50 μm. With respect to the carbides, the number of carbides having an aspect ratio of 2 or less is 80% or more of the number of all carbides, and the average circle-equivalent diameter of all carbides is 0.6 μm or less.