Manufacturing method of non-alloyed steel with excellent impact toughness

摘要

The present invention relates to a method for manufacturing a hot-rolled crude alloy steel used as a material for parts requiring a tensile strength of about 100 kg / mm2 or more among the forging parts of engine, sash and steering device of a vehicle. Its purpose is to provide high quality non-ferrous forging for high tensile strength with low material variation and excellent impact toughness by reducing quenching during water cooling after forging. The present invention for achieving the above object is by weight% C: 0.04-0.15%, Si; 0.10-0.70%, Mn; 0.8-2.0%, Cr: 0.30-1.5, Ni: 0.10-0.50%, W: 0.20-2.0%, Ti: 0.01-0.04%, B: 0.0008-0.0040%, P: 0.0030% or less balance Fe and other unavoidable Hot-rolled steel made of impurity to destroy the cast structure, then reheated to 1200-1300 ℃, and then forged in hot, finished forging at temperature above 1000 ℃ and cooled to room temperature over 200 ℃ / min The gist of the present invention relates to a method for producing an amorphous steel having rapid impact cooling and excellent toughness.