Disclosed are a low-silicon and low-carbon equivalent GPa grade multi-phase steel plate/steel strip and a manufacturing method therefor. The steel plate/steel strip comprises the following components in percentages by weight: 0.03-0.07% of C, 0.1-0.5% of Si, 1.7-2.0% of Mn, P<0.02%, S<0.01%, N<0.01%, 0.01-0.05% of Al, 0.4-0.7% of Cr, 0.001-0.005% of B, and 0.07-0.15% of Ti, and also comprises one or both of 0.15-0.4% of Mo or 0.02-0.08% of Nb, with the balance being Fe and other inevitable impurities; and at the same time, the steel plate/steel strip satisfies: the content of available B*>0.001, the content of available B*=B-[Ti-3.4N-1.2(C—Nb/7.8)]/22, CE<0.58, and CE=C+Mn/6+(Cr+Mo+V)/5+(Si+Ni+Cu)/15. The steel plate has a tensile strength of >980 MPa and a yield strength of >780 MPa, and the hole expansion rate satisfies: if an original hole is a punched hole, the hole expansion rate is >50%; and if the original hole is a reamed hole, the hole expansion rate is >60%. The steel plate is mainly used in the preparation of vehicle chassis and suspension system parts.

Disclosed are a low-silicon and low-carbon equivalent GPa grade multi-phase steel plate/steel strip and a manufacturing method therefor. The steel plate/steel strip comprises the following components in percentages by weight: 0.03-0.07% of C, 0.1-0.5% of Si, 1.7-2.0% of Mn, P<0.02%, S<0.01%, N<0.01%, 0.01-0.05% of Al, 0.4-0.7% of Cr, 0.001-0.005% of B, and 0.07-0.15% of Ti, and also comprises one or both of 0.15-0.4% of Mo or 0.02-0.08% of Nb, with the balance being Fe and other inevitable impurities; and at the same time, the steel plate/steel strip satisfies: the content of available B*>0.001, the content of available B*=B-[Ti-3.4N-1.2(C—Nb/7.8)]/22, CE<0.58, and CE=C+Mn/6+(Cr+Mo+V)/5+(Si+Ni+Cu)/15. The steel plate has a tensile strength of >980 MPa and a yield strength of >780 MPa, and the hole expansion rate satisfies: if an original hole is a punched hole, the hole expansion rate is >50%; and if the original hole is a reamed hole, the hole expansion rate is >60%. The steel plate is mainly used in the preparation of vehicle chassis and suspension system parts.

A steel sheet includes a predetermined composition satisfying Expression (1), in which the microstructure at the ¼ thickness position from the surface in the sheet thickness direction includes, by vol %, ferrite: 95% or more and a remainder of the microstructure: 5% or less, has a proportion of unrecrystallized ferrite in the ferrite of 5% or less, and a half width w and an X-ray wavelength λ at a peak of (200) plane of the ferrite satisfy Expression (2).

0.80≤{(Ti/48−N/14)+Nb/93}/(C/12)≤5.00  (1)

w×λ≥0.20  (2)

A steel sheet includes a predetermined composition satisfying Expression (1), in which the microstructure at the ¼ thickness position from the surface in the sheet thickness direction includes, by vol %, ferrite: 95% or more and a remainder of the microstructure: 5% or less, has a proportion of unrecrystallized ferrite in the ferrite of 5% or less, and a half width w and an X-ray wavelength λ at a peak of (200) plane of the ferrite satisfy Expression (2).

0.80≤{(Ti/48−N/14)+Nb/93}/(C/12)≤5.00  (1)

w×λ≥0.20  (2)

This hot-rolled steel sheet has a predetermined chemical composition, in which a metallographic structure contains, by area %, more than 92.0% and 100.0% or less of martensite and tempered martensite in total, less than 3.0% of residual austenite, and less than 5.0% of ferrite, has a ratio S.sub.60/S.sub.7, which is a ratio of a density S.sub.60 of a length of a grain boundary having a crystal misorientation of 60° to a density S.sub.7 of a length of a grain boundary having a crystal misorientation of 7° about a <110> direction, of more than 0.34 and less than 0.60, has a standard deviation of a Mn concentration of 0.60 mass % or less, and has a tensile strength of 980 MPa or more.

The present disclosure provides a cold-rolled steel sheet having excellent high-temperature properties and room-temperature workability, including, by weight: carbon (C): 0.0005 to 0.003%, manganese (Mn): 0.20 to 0.50%, aluminum (Al): 0.01 to 0.10%, phosphorus (P): 0.003 to 0.020%, nitrogen (N): 0.0005 to 0.004%, sulfur (S): 0.015% or less, niobium (Nb): 0.005 to 0.040%, chromium (Cr): 0.10 to 0.50%, tungsten (W): 0.02 to 0.07%, and a balance of iron (Fe) and other inevitable impurities, wherein C, Nb, and W satisfy the following relationship 1, a microstructure comprises 95 area % or more of polygonal ferrite and 5 area % or less of acicular ferrite, and the cold-rolled steel sheet comprises (Nb,W)C-based precipitates having an average size of 0.005 to 0.10 μm and a method for manufacturing the same:
0.00025≤(2×Nb/93)×(W/184)/(C/12)≤0.0015  [Relationship 1]
where, C, Nb, and W are in weight %.

The present disclosure provides a cold-rolled steel sheet having excellent high-temperature properties and room-temperature workability, including, by weight: carbon (C): 0.0005 to 0.003%, manganese (Mn): 0.20 to 0.50%, aluminum (Al): 0.01 to 0.10%, phosphorus (P): 0.003 to 0.020%, nitrogen (N): 0.0005 to 0.004%, sulfur (S): 0.015% or less, niobium (Nb): 0.005 to 0.040%, chromium (Cr): 0.10 to 0.50%, tungsten (W): 0.02 to 0.07%, and a balance of iron (Fe) and other inevitable impurities, wherein C, Nb, and W satisfy the following relationship 1, a microstructure comprises 95 area % or more of polygonal ferrite and 5 area % or less of acicular ferrite, and the cold-rolled steel sheet comprises (Nb,W)C-based precipitates having an average size of 0.005 to 0.10 μm and a method for manufacturing the same:
0.00025≤(2×Nb/93)×(W/184)/(C/12)≤0.0015  [Relationship 1]
where, C, Nb, and W are in weight %.

The present disclosure provides a hot-press formed part comprising a plated steel sheet and an aluminum alloy plated layer formed on the plated steel sheet, wherein the aluminum alloy plated layer comprises: an alloying layer (I) formed on the plated steel sheet and containing, by weight %, 5-30% of Al; an alloying layer (II) formed on the alloying layer (I) and containing, by weight %, 30 to 60% of Al; an alloying layer (III) formed on the alloying layer (II) and containing, by weight %, 20-50% of Al and 5-20% of Si; and an alloying layer (IV) formed continuously or discontinuously on at least a part of the surface of the alloying layer (III), and containing 30-60% of Al, wherein the rate of the alloying layer (III) exposed on the outermost surface of the aluminum alloy plated layer is 10% or more.

The present disclosure provides a hot-press formed part comprising a plated steel sheet and an aluminum alloy plated layer formed on the plated steel sheet, wherein the aluminum alloy plated layer comprises: an alloying layer (I) formed on the plated steel sheet and containing, by weight %, 5-30% of Al; an alloying layer (II) formed on the alloying layer (I) and containing, by weight %, 30 to 60% of Al; an alloying layer (III) formed on the alloying layer (II) and containing, by weight %, 20-50% of Al and 5-20% of Si; and an alloying layer (IV) formed continuously or discontinuously on at least a part of the surface of the alloying layer (III), and containing 30-60% of Al, wherein the rate of the alloying layer (III) exposed on the outermost surface of the aluminum alloy plated layer is 10% or more.

The present invention relates to a hot stamped component, a precoated steel sheet used for hot stamping, and a hot stamping process. The hot stamped component of the present invention is provided with a coating of aluminium or an aluminium alloy on at least one surface of the base steel, the coating is produced by interdiffusion between the base steel and a precoating of aluminium or aluminium alloy, and the coating has a thickness of 6 to 26 μm.