Steel sheet for hot press formed member having excellent resistance to hydrogen delayed fracture and method for manufacturing thereof

1. A steel sheet for a hot press formed member, comprising:

a base steel sheet;

an aluminum alloy plating layer formed on a surface of the base steel sheet; and

an oxide layer formed on a surface of the aluminum alloy plating layer and having a thickness of 0.3 μm or greater.

2. The steel sheet for a hot press formed member of claim 1 , wherein the aluminum alloy plating layer includes 35 weight % or higher of Fe.

3. The steel sheet for a hot press formed member of claim 1 , wherein the aluminum alloy plating layer includes 45 weight % or higher of Fe.

4. The steel sheet for a hot press formed member of claim 1 , wherein the aluminum alloy plating layer includes 50 weight % or higher of Fe.

5. The steel sheet for a hot press formed member of claim 1 , wherein a lightness value of a surface of the steel sheet is 70 or lower, where the lightness value refers to an L value in a L*a*b* colorimetric system prescribed in KS A 0067.

6. The steel sheet for a hot press formed member of claim 1 , wherein the base steel sheet has a composition comprising, by weight %, by wt %, carbon (C): 0.04% to 0.5%, silicon (Si): 0.01% to 2%, manganese (Mn): 0.01% to 10%, aluminum(Al): 0.001% to 1.0%, phosphorus(P): 0.05% or less, sulfur (S): 0.02% or less, nitrogen (N): 0.02% or less, and residual iron (Fe) and inevitable impurities.

7. The steel sheet for a hot press formed member of claim 6 , wherein the composition further comprises, by wt %, one or more among a sum of one or more selected from the group consisting of Cr, Mo, and W: 0.01% to 4.0%, a sum of one or more selected from the group consisting of Ti, Nb, Zr, and V: 0.001% to 0.4%, Cu+Ni: 0.005% to 2.0%, Sb+Sn: 0.001% to 1.0%, and B: 0.0001 to 0.01%.

8. A method of manufacturing a steel sheet for a hot press formed member, the method comprising:

obtaining an aluminum plated steel sheet by plating a surface of a base steel sheet with aluminum and coiling;

obtaining an aluminum alloy plated steel sheet by annealing the aluminum plated steel sheet; and

cooling the aluminum alloy plated steel sheet,

wherein an amount of the plated aluminum is 30 to 200 g/m 2 with reference to one side of the steel sheet,

wherein coiling tension is 0.5 to 5 kg/mm 2 during the coiling,

wherein the annealing is performed in a batch annealing furnace in a heating temperature range of 550 to 750° C. for 30 minutes to 50 hours,

wherein, when the steel sheet is heated from a room temperature to the heating temperature in the annealing, an average temperature increase rate is 20 to 100° C./h, an

average temperature increase rate in 400 to 50° C. section is 1 to 15° C./h, and a temperature increase rate in a temperature section from the heating temperature −50° C. to the heating temperature is 1 to 15° C./h,

wherein a partial oxygen pressure in the batch annealing furnace during a heat treatment is air pressure 10 −70 to 10 −20 , and

wherein a difference between an atmospheric temperature in the batch annealing furnace and a temperature of the steel sheet is 5 to 80° C., thereby producing the steel sheet of claim 1 .

9. The method of claim 8 , wherein the base steel sheet has a composition comprising, by wt %, carbon (C): 0.04% to 0.5%, silicon (Si): 0.01% to 2%, manganese (Mn): 0.01% to 10%, aluminum(Al): 0.001% to 1.0%, phosphorus(P): 0.05% or less, sulfur (S): 0.02% or less, nitrogen (N): 0.02% or less, and residual iron (Fe) and inevitable impurities.

10. The method of claim 9 , wherein the composition further comprises, by wt %, one or more among a sum of one or more selected from the group consisting of Cr, Mo, and W: 0.01% to 4.0%, a sum of one or more selected from the group consisting of Ti, Nb, Zr, and V: 0.001% to 0.4%, Cu+Ni: 0.005% to 2.0%, Sb+Sn: 0.001% to 1.0%, and B: 0.0001 to 0.01%.