Posco

Posco Co., Ltd

Ki-Cheol Kang

Myung-Soo Kim

Chung-Hwan Lee

Kyoo-Young Lee

Sea-Woong Lee

Il-Jeong Park

Sang-Ho Uhm

Jong-Ho Kim

Jong-Sang Kim

Tae-Chul Kim

Hyeon-Seok Hwang

Yon-Kyun Song

Joo-Hyun Ryu

Young-Roc Im

Chang-Woon Jee

Kwang-Tai Min

Jong-Chan Park

Kang-Min Lee

Yong-Joo Kim

Yeon-Chae Jeong

Seul-Gi So

The present disclosure relates to a zinc plated steel sheet having excellent fatigue strength of electrical resistance spot welds and a method for manufacturing the same. According to an aspect of the present disclosure, a zinc plated steel sheet includes a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet, wherein a concentration profile of one or two of oxygen, and silicon and manganese measured in a depth direction from the surface of the base steel sheet has a maximum point in the depth direction from the surface, and an absolute value of a difference between a depth at which the maximum point of the concentration profile of oxygen is formed and a depth at which the maximum point of the concentration profile of one of silicon and manganese is formed is 0.5 μm or less.

Zinc plated steel sheet having excellent fatigue strength of electrical resistance spot welds, and manufacturing method thereof

A hot-dip galvanized steel sheet according to one aspect of the present invention comprises a base steel sheet and a hot-dip galvanized layer formed on the surface of the base steel sheet, wherein the difference between the average of the Mn/Si values of surface oxides present on a surface portion, which is the region from the interface between the hot-dip galvanized layer and the base steel sheet to a depth of 15 nm, and the average of the Mn/Si values of internal oxides, which are present in the region from the interface to a depth of 50-100 nm, can be 0.5 or more. Mn and Si of each oxide mean the amounts (wt %) of Mn and Si components in the oxide, which are measured by EDS, and the average of Mn/Si values means the averaged value of the Mn/Si values measured for each oxide.

High-strength hot-dip galvanized steel sheet having excellent surface quality and electric resistance spot weldability, and manufacturing method therefor

Provided is a zinc plated steel sheet having excellent spot weldability and a manufacturing method thereof. The zinc plated steel sheet includes a steel sheet and a zinc plated layer formed on the surface of the steel sheet, wherein the ratio (a/b) between a widthwise average value (a) of thickness of an internal oxidized layer and a widthwise standard deviation (b) of thickness of the internal oxidized layer in the steel sheet may be 1.5 or more.

Zinc plated steel sheet having excellent spot weldability and manufacturing method thereof

A galvanized steel sheet including a base steel sheet, and a zinc-based plating layer on the surface of the base steel sheet. The base steel sheet may include a first surface layer region corresponding to a depth of 25 μm from an interface between the base steel sheet and the zinc-based plating layer in a thickness direction of the base steel sheet, and a second surface layer region adjacent to the first surface layer region and corresponding to a depth of 25 μm to 50 μm in the thickness direction of the base steel sheet. A fraction of ferrite contained in the first surface layer region is 55 area % or more, an average grain size of the ferrite contained in the first surface layer region is 2 to 10 μm, and a fraction of ferrite contained in the second surface layer region is 30 area % or more.

High-strength hot-dipped galvanized steel sheet having excellent surface quality and spot weldability, and manufacturing method therefor

A welded member includes: a first steel sheet including a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet; and a second steel sheet spot-welded on the first steel sheet and facing the zinc-based plating layer of the first steel sheet, a spot-welded zone being formed between the first steel sheet and the second steel sheet. A surface layer of the base steel sheet has a decarburization ratio of 30% or more. The decarburization ratio is represented by equation: Decarburization ratio (%) of surface layer=(1−average carbon concentration in surface layer/bulk carbon concentration)*100 where the surface layer refers to a region of the base steel sheet from the surface thereof to a depth of 35 μm. A shoulder portion of the spot-welded zone includes a B-type crack having a length of 100 μm or less, and no C-type crack.

Welded member of galvanized steel sheets

The present invention relates to a zinc plated steel sheet having excellent surface quality and spot weldability, and a manufacturing method therefore. A zinc plated steel sheet according to one aspect of the present invention comprises a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the GDOES profile of oxygen, which is measured in the depth direction from the surface of the base steel sheet, has a form in which a local minimum point and a local maximum point alternately appear in the depth direction from the surface, and the difference (a local maximum value−a local minimum value) between the oxygen concentration (a local minimum value) at the local minimum point and the oxygen concentration (a local maximum value) at the local maximum point can be 0.1 wt % or more.

Zinc plated steel sheet having excellent surface quality and spot weldability, and manufacturing method therefor

The present disclosure relates to a high-strength hot-dip galvanized steel sheet having excellent surface quality and electrical resistance spot weldability, and a method for manufacturing the same. A galvanized steel sheet according to an aspect of the present disclosure is a galvanized steel sheet including a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet, wherein a ratio (a/b) of a hardness of a surface layer portion (a) to a hardness of an internal portion (b) of the base steel sheet may be less than 0.95.

Advanced high strength zinc plated steel sheet having excellent surface quality and electrical resistance spot weldability

Provided is a steel sheet having excellent resistance to liquid metal embrittlement cracks and a method for manufacturing the same. The steel sheet includes, by weight %, 0.04% to 0.35% of C, 0.99% or less of Al+Si, 3.5% to 10% of Mn, 0.05% or less of P (excluding 0%), 0.02% or less of S (excluding 0%), and 0.02% or less of N (excluding 0%) with a remainder of Fe and other inevitable impurities, wherein the steel sheet comprises a microstructure comprising at least 10% of residual austenite, at least 60% of annealed martensite and 20% or less of alpha martensite and epsilon martensite, by volume fraction, and an average thickness of a Mn-depleted layer is at least 0.5 &#x3bc;m from a product surface.

Steel sheet having excellent resistance to liquid metal embrittlement cracks and method for manufacturing the same

Provided is a hot dip aluminized steel material including a base steel and a hot-dip Al&#x2014;Si-coated layer, wherein the surface layer of the base steel is provided with an Al-enriched layer in which 2 wt % to 20 wt % of Al is solid-solubilized, and an interface between the base steel and the hot-dip Al&#x2014;Si-coated layer has a double-layer structured interfacial alloy layer having different hardnesses.

Hot dip aluminized steel material having excellent corrosion resistance and workability, and manufacturing method therefor

Provided is a high-strength hot-dip galvanized steel sheet having good surface quality and spot weldability. The high-strength hot-dip galvanized steel sheet includes a base steel sheet and a zinc plating layer formed on the base steel sheet. The base steel sheet includes carbon (C): 0.1% to 0.3%, silicon (Si): 0.5% to 2.5%, manganese (Mn): 2.0% to 8.0%, soluble aluminum (sol.Al): 0.001% to 0.5%, phosphorus (P): 0.04% or less (excluding 0%), sulfur (S): 0.015% or less, nitrogen (N): 0.02% or less, chromium (Cr): 0.01% to 0.7%, titanium (Ti): (48/14)*[N] % to 0.1%, and a balance of iron (Fe) and inevitable impurities. The base steel sheet has a microstructure comprising ferrite in an area fraction of 5% to 30%, austenite in an area fraction of 5% to 20%, bainite and martensite in an area fraction of 50% to 80%, and precipitates in an area fraction of 2% or less.

High-strength hot-dip galvanized steel sheet having excellent surface quality and spot weldability

A high strength galvanized steel sheet having excellent surface qualities, plating adhesion, and formability is provided, wherein a galvanized layer is formed on a cold-rolled steel sheet comprising 0.1-0.3 wt % of C, 1-2.5 wt % of Si, 2.5-8 wt % of Mn, 0.001-0.5 wt % of sol. Al, at most 0.04 wt % of P, at most 0.015 wt % of S, at most 0.02 wt % of N (excluding 0 wt %), 0.1-0.7 wt % of Cr, at most 0.1 wt % of Mo, (48/14)*[N] to 0.1 wt % of Ti, 0.005-0.5 wt % of Ni, 0.01-0.07 wt % of Sb, at most 0.1 wt % of Nb, and at most 0.005 wt % of B, with the remainder being Fe and other inevitable impurities.

High strength galvanized steel sheet having excellent surface qualities, plating adhesion, and formability, and method for manufacturing same

The present invention relates to an ultra-high strength, hot-dip galvanized steel sheet having excellent surface quality and coating adherence and to a method for manufacturing thereof, the ultra-high strength, hot-dip galvanized steel sheet comprising: 0.1-0.3% by weight carbon (C); 0.1-2.0% by weight silicon (Si); 0.005-1.5% by weight aluminum (Al); 1.5-3.5% by weight manganese (Mn); 0.04% by weight or less phosphorus (P) (excluding 0% by weight); 0.015% by weight or less sulphur (S) (excluding 0% by weight); 0.02% by weight or less nitrogen (N) (excluding 0% by weight); the balance being Fe; and other inevitable impurities, and further comprising 0.01 wt.% to 0.07 wt.% of at least one kind of element selected from the group consisting of bismuth (Bi), tin (Sn) and antimony (Sb).

Growing community of inventors

Gwangyang-si, South Korea

Ki-Cheol Kang