Al—Fe-alloy plated steel sheet for hot forming, having excellent TWB welding characteristics, hot forming member, and manufacturing methods therefor

1. An Al—Fe alloy plated steel sheet for hot press forming, the Al—Fe alloy plated steel sheet comprising:

a base steel sheet comprising, by weight percentage (wt %), carbon (C): 0.1 to 0.5%, silicon (Si): 0.01 to 2.0%, manganese (Mn): 0.1 to 10%, phosphorus (P): 0.001 to 0.05%, sulfur (S): 0.0001 to 0.02%, aluminum (Al): 0.001 to 1.0%, nitrogen (N): 0.001 to 0.02%, and a balance of iron (Fe) and unavoidable impurities;

an Al—Fe alloy layer disposed on the base steel sheet; and

an oxide layer formed on the Al—Fe alloy layer, the oxide layer having a thickness of 2 μm or less, wherein the thickness of 2 μm or less refers to a thickness to a point having 10 wt % of oxygen concentration in an oxygen concentration profile obtained through glow discharge spectrometer (GDS) analysis,

wherein the Al—Fe alloy layer comprises, by wt %, aluminum (Al): 40 to 60%, silicon (Si): 2 to 10%, and a balance of iron (Fe) and unavoidable impurities, and a fraction of an unalloyed phase is 1 area % or less, and

wherein the Al—Fe alloy layer comprises:

a diffusion layer disposed on the base steel sheet and constituting a layer while including Si in an amount of 0.5 to 12.0 wt %; and

an intermediate layer disposed in the Al—Fe alloy layer and constituting a layer while including Si in an amount of 3.0 to 20.0 wt %, and

wherein a sum of average thicknesses of the diffusion layer and the intermediate layer is 1.0 to 10 μm.

2. The Al—Fe alloy plated steel sheet of claim 1 , wherein the base steel sheet further comprises one or more of chromium (Cr) and molybdenum (Mo) in a total amount of 0.01 to 4.0 wt %.

3. The Al—Fe alloy plated steel sheet of claim 1 , wherein the base steel sheet further comprises one or more of titanium (Ti), niobium (Nb), and vanadium (V) in a total amount of 0.001 to 0.4 wt %.

4. The Al—Fe alloy plated steel sheet of claim 1 , wherein the base steel sheet further comprises boron (B) in an amount of 0.0001 to 0.01 wt %.

5. The Al—Fe alloy plated steel sheet of claim 1 , wherein the base steel sheet has a microstructure comprising, by an area fraction, 20% or less of pearlite, 10% or less of martensite, 10% or less of spheroidized carbide, and a balance of ferrite.

6. The Al—Fe alloy plated steel sheet of claim 1 , wherein the Al—Fe alloy layer has a thickness of 10 to 60 μm.

7. A hot press formed part manufactured by hot press forming a tailer welded blank, the tailer welded blank being manufactured by welding an Al—Fe alloy plated steel sheet of claim 1 to a steel sheet having a thickness or a strength different from a thickness or a strength of the Al—Fe alloyed plate steel sheet,

wherein the hot press formed part has a tensile strength of 1300 MPa or more and a welding zone hardness deviation of 100Hv or less.

8. The hot press formed part of claim 7 , wherein a portion corresponding to the Al—Fe alloy plated steel sheet has a microstructure comprising martensite or bainite as a main phase, 30 area % or less of retained austenite, and 5 area % or less of ferrite.

9. A method of manufacturing a hot press formed part, the method comprising:

welding an Al—Fe alloy plated steel sheet of claim 1 to a steel sheet having a thickness or a strength different from a thickness or a strength of the Al—Fe alloy plated steel sheet to form a tailer welded blank;

heating the tailer welded blank to a temperate within a range of (Ae3+30° C.) to (Ae3+150° C.) at a heating rate of 1 to 1000° C./sec and then maintained for 1 to 1000 seconds to form a heated tailer welded blank; and

hot press forming the heated tailer welded blank while simultaneously cooling at a cooling rate of 1 to 1000° C./sec.

10. The method of claim 9 , wherein the steel sheet having the strength different from that of the Al—Fe alloy plated steel sheet comprises carbon (C): 0.05 to 0.08%, silicon (Si): 0.01 to 0.4%, manganese (Mn): 0.08 to 1.7%, aluminum (Al): 0.01 to 0.07%, Ti: 0.09% or less, and a balance of iron (Fe) and unavoidable impurities.