HOT-ROLLED STEEL SHEET HAVING EXCELLENT SURFACE HARDNESS AFTER CARBURIZING HEAT TREATMENT AND EXCELLENT COLD WORKABILITY.

摘要

A hot-rolled steel sheet that: has a sheet thickness of 2-10 mm; contains specific amounts of C, Mn, Al, and N, the remainder comprising iron and unavoidable impurities; and has a specified surface area occupied by ferrite and pearlite, the remainder comprising bainite. Of the total number of crystal grains in the hot-rolled steel sheet, 60% are crystal grains that have an aspect ratio (major axis/minor axis) of 3 or less, and the average crystal grain diameter of all of the crystal grains is 3-50 µm.