| 摘要 |
<p>PURPOSE: A steel material having fine crystal grains and a method for manufacturing products using the same are provided to obtain desired performance without chemical heat treatment such as carburization, thereby reducing manufacturing time and costs. CONSTITUTION: A steel material having fine crystal grains is mainly composed of Fe, and the steel material comprises 0.3-0.8 wt% of C, 0.15-0.5 wt% of Si, 0.5-1.5 wt% of Mn, 0.03 wt% or less(0 is exclusive) of P, 0.01-0.1 wt% of S, 0.5-2.5 wt% of Cr, 0.02-0.1 wt% of Mo, 0.01-0.04 wt% of Nb, 0.0001-0.0005 wt% of B, 0.0002 wt% or less(0 is exclusive) of O, 0.03-0.2 wt% of Ti, and inevitable impurities. A method for manufacturing a product using the steel material comprises the steps of: cutting and hot forging the steel material, mechanically processing the hot forged steel material, processing the material with high frequency, and correcting the heat-treated material. [Reference numerals] (AA) Material cutting; (BB) Hot forging; (CC) Finish cutting; (DD) High-frequency heat treatment; (EE) Correcting</p> |
