Provided are a plated steel sheet for hot press forming including: a base steel sheet containing, by wt%, 0.14 to 0.5% of C, 0.001 to 1% of Si, 0.3 to 4% of Mn, 0.001 to 0.015% of P, 0.0001 to 0.02% of S, 0.001 to 0.1% of Al, 0.001 to 1% of Cr, 0.001 to 0.02% of N, 0.1% or less of Ti, 0.01% or less of B, 0.005 to 0.1% of Sb, and a balance of Fe and unavoidable impurities; an aluminum or aluminum alloy plating layer provided on at least one surface of the base steel sheet; and a Sb-rich layer provided between the base steel sheet and the plating layer, wherein the plated steel sheet for hot press forming satisfies the following Relational Expressions 1-1 and 1-2, a hot press formed member manufactured using the same, and methods for manufacturing the plated steel sheet for hot press forming and the hot press formed member.

[00001]$\begin{array}{cc}\frac{S{b}_{\max }}{S{b}_{coat}}\ge 1.2& \text{­­­[Relational Expression 1-1]}\end{array}$

[00002]$\begin{array}{cc}\frac{\left(S{b}_{\max }-S{b}_{coat}\right)}{2}\times \text{Δ}t\ge 0.008& \text{­­­[Relational Expression 1-2]}\end{array}$

[In Relational Expressions 1-1 and 1-2, Sb.sub.coat represents an average content of Sb in the plating layer, and a unit thereof is wt%, Sb.sub.max represents a maximum value of a content of Sb in the Sb-rich layer, and a unit thereof is wt%, and Δt represents a linear distance from a boundary between the plating layer and the Sb-rich layer to a point where Sb.sub.max is measured, and a unit thereof is .Math.m.]

Provided is a high-strength cold rolled steel sheet, a high-strength hot-dip galvanized steel sheet manufactured using the cold rolled steel sheet, and manufacturing methods therefor, the high-strength cold rolled steel sheet comprising, by wt %, 0.17-0.21% of carbon (C), 0.3-0.8% of silicon (Si), 2.7-3.3% of manganese (Mn), 0.3-0.7% of chromium (Cr), 0.01-0.3% of aluminum (Al), 0.01-0.03% of titanium (Ti), 0.001-0.003% of boron (B), 0.04% or less of phosphorus (P), 0.02% or less of sulfur (S), 0.01% or less of nitrogen (N) and the balance of iron (Fe) and other inevitable impurities, wherein the amounts of carbon (C), silicon (Si) and aluminum (Al) satisfy the following mathematical relation (1). [Mathematical relation (1)] [C]+([Si]+[Al])/5≤0.35% (wherein [C], [Si] and [Al] respectively mean the wt % of C, Si and Al.)

A hot-rolled flat steel product having a thickness of <1.5 and consisting of, in % by mass, C: 0.04-0.23%, Si: 0.04 0.54%, Mn: 1.4-2.9%, Ti+V, wherein 0.005%<%Ti+%V<0.15%, and optionally one or more elements of Al, Cr, Mo, and B, where AI: 0.01-1.5%, 0.02<%Mo+%Cr<1.4%, and B: 0.0005-0.005%, and the remainder consisting of iron and inevitable impurities. The structure of the flat steel product consists of, in percent by area, in sum, 50-90% ferrite and bainite ferrite, 5-50% martensite, 2-15% residual austenite and <10% other structure elements. The flat steel product has a yield point Rp0.2>290 MPa, a tensile strength Rm>490 MPa and an elongation at break A80 where A80[%]=B−Rm/37 with 31<B<51. To at least one surface of the flat steel product, a Zn coating is applied by hot-dip coating. Also a method for producing a flat steel product of this kind.

An ultra low carbon interstitial free steel having an improved composition, wherein Ti+Nb+V is max 0.10 weight %. This steel has a very good ductility.

A continuous hot-dip galvanizing apparatus has a vertical annealing furnace, one or more hearth rolls, a hot-dip galvanizing apparatus, an alloying line, and humidified gas supply ports. When the steel sheet having a Si content of 0.2 mass % or more is conveyed inside the annealing furnace, the humidified gas supply ports positioned in a latter part of the soaking zone supply the humidified gas to the soaking zone and the at least one dry gas supply port supplies the dry gas to the soaking zone. When the steel sheet having a Si content of less than 0.2 mass % is conveyed inside the annealing furnace, the plurality of the humidified gas supply ports do not supply the humidified gas to the soaking zone and the at least one dry gas supply port supplies the dry gas to the soaking zone.

A high-strength galvanized steel sheet and a method for producing the steel sheet. The steel sheet has a composition that includes C: 0.030% to 0.250%, Si: 0.01% to 3.00%, Mn: 2.00% to 10.00%, P: 0.001% to 0.100%, S: 0.0001% to 0.0200%, N: 0.0005% to 0.0100%, Ti: 0.005% to 0.200%, on a mass basis, and Fe and inevitable impurities. Additionally, the steel sheet has concentration of solute Mn at a depth of 5 μm or less from a surface of the steel sheet that is 1.50% by mass or less, and a value obtained by dividing the average mass percentage of Mn in retained austenite by the average mass percentage of Mn in ferrite is 2.0 or more.

Provided are a steel sheet dehydrogenation apparatus, a steel sheet production system, and a steel sheet production method capable of producing a steel sheet excellent in hydrogen embrittlement resistance without changing the mechanical properties of the steel sheet. A dehydrogenation apparatus comprises: a housing configured to house a steel sheet coil obtained by coiling a steel strip; and a sound wave irradiator configured to irradiate the steel sheet coil housed in the housing with sound waves to obtain a product coil.

Provided are a hot dip galvanized steel sheet comprising a base steel sheet and a hot dip galvanized layer on at least one surface of the base metal steel sheet, wherein the base steel sheet has a predetermined chemical composition and contains, by volume fraction, ferrite: 0% to 50%, retained austenite: 6% to 30%, bainite: 5% or more, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, a number density of tempered martensite with a circle equivalent diameter of 5.0 μm or more is 20/1000 μm.sup.2 or less, and an area ratio of fresh martensite with a circle equivalent diameter of 2.0 μm or more after imparting 5% plastic strain is 10% or less, and a method for producing the same.

Provided are a hot rolled steel sheet having excellent crashworthiness and a method for manufacturing same. The hot rolled steel sheet of the present invention contains, in weight %, 0.05-0.13% of carbon (C), 0.2-2.0% of silicon (Si), 1.3-3.0% of manganese (Mn), 0.01-0.1% of aluminum (Al), 0.001-0.05% of phosphor (P), 0.001-0.05% of sulfur (S), 0.001-0.02% of nitrogen (N), and the balance being Fe and other inevitable impurities, and has a steel microstructure comprising, in area %, 55% or more of bainitic ferrite, 10% or more of a martensite/austenite composite phase (MA), the sum of the bainitic ferrite and the martensite/austenite composite phase (MA) being 95% or more, and the remaining total being less than 5% of granular ferrite, retained austenite, and carbides.

A steel member according to an aspect of the present invention has a predetermined chemical composition, in which a metallographic structure includes, by a volume %, 60.0% to 85.0% of martensite, 10.0% to 30.0% of bainite, 5.0% to 15.0% of residual austenite, and 0% to 4.0% of a remainder in microstructure. A length of a maximum minor axis of the residual austenite is 30 nm or longer. A number density of a carbide which exist in the steel member and has a circle equivalent diameter of 0.1 μm or more and an aspect ratio of 2.5 or less is 4.0×10.sup.3 pieces/mm.sup.2 or less.