AUTOMOBILE PART MANUFACTURING METHOD USING QUENCHED STEEL SHEET

1 - 9 . (canceled)

10 . A method of manufacturing an automobile part, comprising:

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 AC 3 or more, followed by quenching the cold-pressed part received within dies to remove residual stress while increasing strength of the automobile part.

11 . A method of manufacturing an automobile part, comprising:

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 to an extent of 80 to 99% of a final shape of the automobile part; and

heating the cold-pressed part to a temperature of AC 3 or more to form the remaining 1 to 20% of the final shape, followed by quenching the formed automobile part received within dies to remove residual stress while increasing strength of the automobile part.

12 . A method of manufacturing an automobile part, comprising:

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; and

heating the blank assembly to a temperature of AC 3 or more, followed by hot-pressing the blank assembly and quenching the hot-pressed part received within dies to remove residual stress while increasing strength of the automobile part.

13 . The method of claim 10 , wherein the steel sheets in preparation of the preparing blank sheets are subjected to surface treatment by at least one process selected from among Zn plating, Al plating, Al—Si plating and high temperature oxidizing agent coating.

14 . The method of claim 11 , wherein the steel sheets in preparation of the preparing blank sheets are subjected to surface treatment by at least one process selected from among Zn plating, Al plating, Al—Si plating and high temperature oxidizing agent coating.

15 . The method of claim 12 , wherein the steel sheets in preparation of the preparing blank sheets are subjected to surface treatment by at least one process selected from among Zn plating, Al plating, Al—Si plating and high temperature oxidizing agent coating.

16 . The method of claim 10 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.5 wt % of carbon (C), 0.15 to 0.5 wt % of silicon (Si), 0.5 to 3.0 wt % of manganese (Mn), 0.1 wt % or less of phosphorous (P), 0.1 wt % or less of sulfur (S), 0.01 to 1.0 wt % of chromium (Cr), 0.2 wt % or less of titanium (Ti), 0.1 wt % or less of aluminum (Al), 0.0005 to 0.08 wt % of boron (B), and the balance of Fe and unavoidable impurities.

17 . The method of claim 11 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.5 wt % of carbon (C), 0.15 to 0.5 wt % of silicon (Si), 0.5 to 3.0 wt % of manganese (Mn), 0.1 wt % or less of phosphorous (P), 0.1 wt % or less of sulfur (S), 0.01 to 1.0 wt % of chromium (Cr), 0.2 wt % or less of titanium (Ti), 0.1 wt % or less of aluminum (Al), 0.0005 to 0.08 wt % of boron (B), and the balance of Fe and unavoidable impurities.

18 . The method of claim 12 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.5 wt % of carbon (C), 0.15 to 0.5 wt % of silicon (Si), 0.5 to 3.0 wt % of manganese (Mn), 0.1 wt % or less of phosphorous (P), 0.1 wt % or less of sulfur (S), 0.01 to 1.0 wt % of chromium (Cr), 0.2 wt % or less of titanium (Ti), 0.1 wt % or less of aluminum (Al), 0.0005 to 0.08 wt % of boron (B), and the balance of Fe and unavoidable impurities.

19 . The method of claim 10 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.4 wt % of carbon (C), 0.03 to 0.4 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.12 wt % or less of phosphorous (P), 0.003 wt % or less of sulfur (S), 0.0005 to 0.08 wt % of boron (B), 0.005 to 0.1 wt % of zirconium (Zr), 0.001 to 0.005 wt % of calcium (Ca), and the balance of Fe and unavoidable impurities.

20 . The method of claim 11 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.4 wt % of carbon (C), 0.03 to 0.4 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.12 wt % or less of phosphorous (P), 0.003 wt % or less of sulfur (S), 0.0005 to 0.08 wt % of boron (B), 0.005 to 0.1 wt % of zirconium (Zr), 0.001 to 0.005 wt % of calcium (Ca), and the balance of Fe and unavoidable impurities.

21 . The method of claim 12 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.4 wt % of carbon (C), 0.03 to 0.4 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.12 wt % or less of phosphorous (P), 0.003 wt % or less of sulfur (S), 0.0005 to 0.08 wt % of boron (B), 0.005 to 0.1 wt % of zirconium (Zr), 0.001 to 0.005 wt % of calcium (Ca), and the balance of Fe and unavoidable impurities.

22 . The method of claim 10 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.30 wt % of carbon (C), 0.05 to 0.5 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.0005 to 0.0040 wt % of boron (B), 0.003 wt % or less of sulfur (S), 0.012 wt % or less of phosphorous (P), at least two components selected from among cobalt (Co), zirconium (Zr) and antimony (Sb), and the balance of Fe and unavoidable impurities.

23 . The method of claim 11 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.30 wt % of carbon (C), 0.05 to 0.5 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.0005 to 0.0040 wt % of boron (B), 0.003 wt % or less of sulfur (S), 0.012 wt % or less of phosphorous (P), at least two components selected from among cobalt (Co), zirconium (Zr) and antimony (Sb), and the balance of Fe and unavoidable impurities.

24 . The method of claim 12 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.30 wt % of carbon (C), 0.05 to 0.5 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.0005 to 0.0040 wt % of boron (B), 0.003 wt % or less of sulfur (S), 0.012 wt % or less of phosphorous (P), at least two components selected from among cobalt (Co), zirconium (Zr) and antimony (Sb), and the balance of Fe and unavoidable impurities.

25 . The method of claim 10 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.40 wt % of carbon (C), 0.03 to 0.30 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.0005 to 0.004 wt % of boron (B), optionally, at least one of 0.003 wt % or less of sulfur (S), 0.012 wt % or less of phosphorous (P), 0.001 to 0.005 wt % of calcium (Ca), 0.005 to 0.05 wt % of niobium (Nb), 0.005 to 0.1 wt % of zirconium (Zr) and 0.0005 to 0.5 wt % of cobalt (Co), and the balance of Fe and unavoidable impurities.

26 . The method of claim 11 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.40 wt % of carbon (C), 0.03 to 0.30 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.0005 to 0.004 wt % of boron (B), optionally, at least one of 0.003 wt % or less of sulfur (S), 0.012 wt % or less of phosphorous (P), 0.001 to 0.005 wt % of calcium (Ca), 0.005 to 0.05 wt % of niobium (Nb), 0.005 to 0.1 wt % of zirconium (Zr) and 0.0005 to 0.5 wt % of cobalt (Co), and the balance of Fe and unavoidable impurities.

27 . The method of claim 12 , wherein the steel sheets in preparation of the blank sheets comprise 0.15 to 0.40 wt % of carbon (C), 0.03 to 0.30 wt % of silicon (Si), 1.0 to 2.0 wt % of manganese (Mn), 0.0005 to 0.004 wt % of boron (B), optionally, at least one of 0.003 wt % or less of sulfur (S), 0.012 wt % or less of phosphorous (P), 0.001 to 0.005 wt % of calcium (Ca), 0.005 to 0.05 wt % of niobium (Nb), 0.005 to 0.1 wt % of zirconium (Zr) and 0.0005 to 0.5 wt % of cobalt (Co), and the balance of Fe and unavoidable impurities.

28 . The method of claim 10 , wherein the steel sheets in preparation of the blank sheets comprise 0.19 to 0.40 wt % of carbon (C), 0.5 to 2.5 wt % of manganese (Mn), 0.1 to 0.5 wt % of chromium (Cr), 0.0015 to 0.0040 wt % of boron (B), 0.01 to 0.5 wt % of silicon (Si), 0.05 wt % or less of phosphorous (P), 0.05 wt % or less of sulfur (S), 0.03 wt % or less of aluminum (Al), one or two components selected from among 0.01 to 2 wt % of nickel (Ni), 0.01 to 0.10 wt % of niobium (Nb), 0.01 to 1 wt % of copper (Cu) and 0.01 to 0.20 wt % of molybdenum (Mo), and the balance of Fe and unavoidable impurities.

29 . The method of claim 11 , wherein the steel sheets in preparation of the blank sheets comprise 0.19 to 0.40 wt % of carbon (C), 0.5 to 2.5 wt % of manganese (Mn), 0.1 to 0.5 wt % of chromium (Cr), 0.0015 to 0.0040 wt % of boron (B), 0.01 to 0.5 wt % of silicon (Si), 0.05 wt % or less of phosphorous (P), 0.05 wt % or less of sulfur (S), 0.03 wt % or less of aluminum (Al), one or two components selected from among 0.01 to 2 wt % of nickel (Ni), 0.01 to 0.10 wt % of niobium (Nb), 0.01 to 1 wt % of copper (Cu) and 0.01 to 0.20 wt % of molybdenum (Mo), and the balance of Fe and unavoidable impurities.

30 . The method of claim 12 , wherein the steel sheets in preparation of the blank sheets comprise 0.19 to 0.40 wt % of carbon (C), 0.5 to 2.5 wt % of manganese (Mn), 0.1 to 0.5 wt % of chromium (Cr), 0.0015 to 0.0040 wt % of boron (B), 0.01 to 0.5 wt % of silicon (Si), 0.05 wt % or less of phosphorous (P), 0.05 wt % or less of sulfur (S), 0.03 wt % or less of aluminum (Al), one or two components selected from among 0.01 to 2 wt % of nickel (Ni), 0.01 to 0.10 wt % of niobium (Nb), 0.01 to 1 wt % of copper (Cu) and 0.01 to 0.20 wt % of molybdenum (Mo), and the balance of Fe and unavoidable impurities.