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 being iron and unavoidable impurities, and contains ferrite and pearlite in a specified area ratio, the remainder being bainite. In the hot-rolled steel sheet, a number of grains having an aspect ratio of major axis to minor axis of 3 or less is 60% or more of a number of all grains and an average grain size of the all grains is from 3 to 50 μm.