| 摘要 |
<p>The invention provides a steel material for non-heat-treated steel parts having a high strength in a state formed by hot working. A high-strength non-heat-treated steel for hot forging, which contains carbon, silicon, manganese, chromium, sulfur, vanadium and nitrogen and at least one of aluminum and titanium each in a specified quantity and has a carbon equivalent and a bainitic transformation start point each in a given range; and another high-strength non-heat-treated steel for hot forging, which contains carbon, silicon, manganese, chromium, sulfur, vanadium, nitrogen and calcium and at least one of aluminum and titanium each in a specified quantity and has a carbon equivalent and a bainitic transformation start point each in a given range. This steel material has a tensile strength of 900 MPa or above in a hot-forged and non-heat-treated state and enables size and weight reduction of automotive parts.</p> |
