Abstract: Disclosed are heat-hardened steel with excellent crashworthiness and a method for manufacturing heat-hardenable parts using the same. The heat-hardened steel according to the invention comprises, based on wt %; C: 0.12-0.8%; Cr: 0.01-2%; Mo: 0.2% or less; B: 0.0005-0.08%; Ca: 0.01 or less; Sb: 1.0% or less; and Ti and/or Nb: 0.2%; and the reminder being Fe and inevitable impurities. In addition, the heat-treatment hardening steel satisfies anyone of following conditions i)-iv), wherein condition i) comprises Si: 0.5-3%; Mn: 1-10% and Al: 0.05-2%; condition ii) comprises Si: 1% or less; Mn: 0.5-5%; Al: 0.1-2.5%; and Ni: 0.01-8%; condition iii) comprises Si: 0.5-3%; Mn: 1-10%; Al: 0.1% or less; and Ni: 0.01-8%; and condition iv) comprises Si: 0.5-3%; Mn: 1-10%; Al: 0.1-2.5%; and Ni: 0.01-8%.

Abstract: Disclosed are a preparation method of a steel product capable of local reinforcement using laser heat treatment, and a heat hardened steel used in the method. According to the present invention, the preparation method of a steel part comprises the following steps: (a) preparing a material comprising 0.1-0.5 wt % of C, 0.1-0.5 wt % of Si, 0.5-3.0 wt % of Mn, 0.1 wt % or less of P, 0.05 wt % or less of S, 0.01-1.0 wt % of Cr, 0.1 wt % or less of Al, 0.2 wt % or less of Ti, 0.0005-0.08 wt % of B, and the balance of Fe and inevitable impurities; (b) preparing a formed product by forming the material into a predetermined shape; and (c) locally reinforcing the high strength portion by carrying out laser heat treatment on a portion requiring high strength at the formed product.

Abstract: Disclosed herein is method of manufacturing an automobile part having different local strengths, more particularly, a method of manufacturing an automobile part using a steel sheet subjected to heat-treatment hardening and having different local thicknesses. The method includes preparing blank sheets using steel sheets subjected to heat-treatment hardening and having different thicknesses or different material properties according to desired strength; forming a blank assembly by joining the blank sheets to each other via laser welding; cold-pressing the blank assembly; and heating the cold-pressed part to a temperature of AC3 or more, followed by quenching the cold-formed part received within dies to remove residual stress while increasing strength of the automobile part.

Abstract: Disclosed are a preparation method of a steel product capable of local reinforcement using laser heat treatment, and a heat hardened steel used in the method. According to the present invention, the preparation method of a steel part comprises the following steps: (a) preparing a material comprising 0.1-0.5 wt % of C, 0.1-0.5 wt % of Si, 0.5-3.0 wt % of Mn, 0.1 wt % or less of P, 0.05 wt % or less of S, 0.01-1.0 wt % of Cr, 0.1 wt % or less of Al, 0.2 wt % or less of Ti, 0.0005-0.08 wt % of B, and the balance of Fe and inevitable impurities; (b) preparing a formed product by forming the material into a predetermined shape; and (c) locally reinforcing the high strength portion by carrying out laser heat treatment on a portion requiring high strength at the formed product.

Abstract: Disclosed are heat-hardened steel with excellent crashworthiness and a method for manufacturing heat-hardenable parts using the same. The heat-hardened steel according to the invention comprises, based on wt %; C: 0.12-0.8%; Cr: 0.01-2%; Mo: 0.2% or less; B: 0.0005-0.08%; Ca: 0.01 or less; Sb: 1.0% or less; and Ti and/or Nb: 0.2%; and the reminder being Fe and inevitable impurities. In addition, the heat-treatment hardening steel satisfies anyone of following conditions i)-iv), wherein condition i) comprises Si: 0.5-3%; Mn: 1-10% and Al: 0.05-2%; condition ii) comprises Si: 1% or less; Mn: 0.5-5%; Al: 0.1-2.5%; and Ni: 0.01-8%; condition iii) comprises Si: 0.5-3%; Mn: 1-10%; Al: 0.1% or less; and Ni: 0.01-8%; and condition iv) comprises Si: 0.5-3%; Mn: 1-10%; Al: 0.1-2.5%; and Ni: 0.01-8%.

Abstract: Disclosed herein is method of manufacturing an automobile part having different local strengths, more particularly, a method of manufacturing an automobile part using a steel sheet subjected to heat-treatment hardening and having different local thicknesses. The method includes preparing blank sheets using steel sheets subjected to heat-treatment hardening and having different thicknesses or different material properties according to desired strength; forming a blank assembly by joining the blank sheets to each other via laser welding; cold-pressing the blank assembly; and heating the cold-pressed part to a temperature of AC3 or more, followed by quenching the cold-formed part received within dies to remove residual stress while increasing strength of the automobile part.