Posco Co., Ltd

Posco

Sung-Il Kim

Hyeon-Seok Hwang

Sang-Ho Han

Hyun-Taek Na

Kwang-Geun Chin

Seok-Jong Seo

Hee-Sung Kang

Hyun-Seok Tak

Je-Woong Lee

Tae-Jin Song

Man-Young Park

Dong-Wan Kim

Chang-Sik Choi

Jeong-Eun Kim

Jeong-Bong Yoon

Gyu-Yeol Bae

Chung-Won Kim

Cho-Rong Hong

Ho-Seok Kim

Doo-Jin Paik

Seul-Ki Park

Jung-Ki Kim

Hyeon-seok Hwang

Jin-Hee Chung

Provided is a high strength multi-phase steel having excellent burring properties at low temperature, and a method for producing the same. More specifically, provided are a high strength multi-phase steel having excellent burring properties at low temperature, and a method for producing the same, wherein the multi-phase steel can be appropriately used as a member, a lower arm, a reinforcement material, a connection material, or the like for a vehicle chassis component.

High strength multi-phase steel having excellent burring properties at low temperature, and method for producing same

Provided are thick hot-rolled composite-phase steel having excellent durability and a manufacturing method therefor. The thick composite-phase steel having excellent durability according to the present invention comprises, by wt %, C: 0.05 to 0.15%, Si: 0.01 to 1.0%, Mn: 1.0 to 2.3%, Al: 0.01 to 0.1%, Cr: 0.005 to 1.0%, P: 0.001 to 0.05%, S: 0.001 to 0.01%, N: 0.001 to 0.01%, Nb: 0.005 to 0.07%, Ti: 0.005 to 0.11%, Fe, and inevitable impurities, and has a mixed phase of ferrite and bainite as a base structure, wherein, in the base structure, the area fraction of each of a pearlite phase and a martensite and austenite (MA) phase is less than 5%, and the area fraction of a martensite phase is less than 10%.

Thick composite-phase steel having excellent durability and manufacturing method therefor

The present invention provides a steel sheet comprising by weight: C: 0.10-0.30%; Si: 0.001-1.0%; Mn: 0.5-2.5%; Cr: 0.001-1.5%; Mo: 0.001-0.5%; Al: 0.001-0.5%; P: 0.001-0.01%; S: 0.001-0.01%; N: 0.001-0.01%; B: 0.0001-0.004%; Ti: 0.001-0.1%; Nb: 0.001 to 0.1%; and the balance consisting of Fe and inevitable impurities, and satisfying relational expression (1), and a microstructure includes comprising: a martensite phase; a bainite phase, wherein the fraction of the martensite phase is 50-90%, the fraction of the bainite phase is 5-50%, the sum of the fractions of the martensite phase and the bainite phase is 90% or more; and the balance consisting of a ferrite phase.CL<1,  [Relationship Expression (1)]CL=−0.692−0.158×[Mn]+0.121×[Mn]+0.061×[Cr]−0.319×[Mo]+0.035×[Hardness_HRC] (where CL is an effective cracking index, [Mn], [Cr] and [Mo] are the percentages by weight of respective corresponding alloy elements, and [Hardness_HRC] is a Rockwell hardness (HRC).)

High-strength hot-rolled steel sheet having excellent blanking properties and uniformity, and manufacturing method thereof

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.

Hot rolled steel sheet having excellent crashworthiness and method for manufacturing same

The present disclosure relates to a hot-rolled steel sheet utilized as material for heavy machinery, vehicle frames, and the like, and more specifically to a high-strength hot-rolled steel sheet having excellent bendability and low-temperature toughness and a method for manufacturing same.

High-strength hot-rolled steel sheet having excellent bendability and low-temperature and method for manufacturing same

Thick high-strength steel having a high yield ratio and excellent durability, and a method for manufacturing same are provided. The thick high-strength steel having a high yield ratio and excellent durability of the present invention comprises, in percentage by weight, C: 0.05 to 0.15%, Si: 0.01 to 1.0%, Mn: 1.0 to 2.3%, Al: 0.01 to 0.1%, Cr: 0.005 to 1.0%, P: 0.001 to 0.05%, S: 0.001 to 0.01%, N: 0.001 to 0.01%, Nb: 0.005 to 0.07%, Ti 0.005 to 0.11%, Fe and unavoidable impurities.

High-strength steel having high yield ratio and excellent durability, and method for manufacturing same

Provided is a method for manufacturing a steel sheet, the method including: reheating a steel slab at a temperature of 1200° C. to 1350° C., the steel slab including, by weight %, carbon (C): 0.05% to 0.14%, silicon (Si): 0.01% to 1.0%, manganese (Mn): 1.5% to 2.5%, aluminum (Al): 0.01% to 0.1%, chromium (Cr): 0.005% to 1.0%, phosphorus (P): 0.001% to 0.05%, sulfur (S): 0.001% to 0.01%, nitrogen (N): 0.001% to 0.01%, niobium (Nb): 0.005% to 0.06%, titanium (Ti): 0.005% to 0.11%, and a balance of iron (Fe) and inevitable impurities; finish hot rolling the reheated steel slab under predetermined conditions to obtain a hot-rolled steel sheet; cooling the hot-rolled steel sheet at a cooling rate of 10° C./s to 100° C./s to a temperature of 400° C. to 500° C. after the finish hot rolling; and coiling the steel sheet at a temperature of 400° C. to 500° C. after the cooling.

High-strength steel sheet having excellent impact resistant property and method for manufacturing thereof

The hot-rolled coated steel sheet comprising: in wt %, C: 0.05-0.14%, Si: 0.1-1.0%, Mn: 1.0-2.0%, P: 0.001-0.05%, S: 0.001-0.01%, AI: 0.01-0.1%, Cr: 0.005-1.0%, Ti: 0.005-0.13%, Nb: 0.005-0.03%, N: 0.001-0.01%, Fe residues, and other inevitable impurities; a mixed structure of ferrite and bainite as a main phase; and as a remaining structure, one or more selected from the group consisting of martensite, austenite, and phase martensite (MA), wherein a fraction of the ferrite and bainite is 95-99 area % and Equation 1 is satisfied. [Equation 1] FCO+FCO&#x2265;10 where, FCOand FCO, each representing an area fraction occupied by a structure having ac crystal orientation of {110}&#x3c;112&#x3e; and {112}&#x3c;111&#x3e;.

Hot rolled coated steel sheet having high strength, high formability, excellent bake hardenability and method of manufacturing same

The present invention relates to material utilized for heavy construction machinery, vehicle frames, reinforcing members, and the like, and more specifically to a high-strength steel sheet having excellent impact resistance and a method for manufacturing same.

High-strength steel sheet having excellent impact resistance, and method for manufacturing same

A hot-rolled coated steel sheet including: in wt %, C: 0.05-0.14%, Si: 0.1-1.0%, Mn: 1.0-2.0%, P: 0.001-0.05%, S: 0.001-0.01%, AI: 0.01-0.1%, Cr: 0.005-1.0%, Ti: 0.005-0.13%, Nb: 0.005-0.03%, N: 0.001-0.01%, Fe residues, and other inevitable impurities; a mixed structure of ferrite and bainite as a main phase; and as a remaining structure, one or more selected from the group consisting of martensite, austenite, and phase martensite (MA), wherein a fraction of the ferrite and bainite is 95-99 area % and Equation 1 is satisfied. [Equation 1] FCO+FCO&#x2265;10 where, FCOand FCO, each representing an area fraction occupied by a structure having ac crystal orientation of {110}&#x3c;112&#x3e; and {112}&#x3c;111&#x3e;.

Provided is a steel sheet having excellent image clarity after painting, including: carbon (C): 0.001% to 0.03%, silicon (Si): 0.001% to 0.35%, manganese (Mn): 0.05% to 2.2%, phosphorus (P): 0.003% to 0.1%, sulfur (S): 0.001% or 0.025%, aluminum (Al): 0.01% to 0.1%, nitrogen (N): 0.001% to 0.007%, and a remainder of iron (Fe) and inevitable impurities. The microstructure of the steel sheet mainly is ferrite phases. An R-cube texture of a surface layer of the steel sheet is 5% or less by area %.

Steel sheet having excellent image clarity after painting

Provided is a high-strength steel sheet having excellent burring workability in a low temperature range, which is mainly used for automobile chassis parts such as members, lower arms, wheel disks, etc.; and a manufacturing method therefor.

High-strength steel sheet having excellent burring workability in low temperature range and manufacturing method therefor

Provided is an ultra high strength hot-rolled steel sheet including, in percentage by weight: 0.15-0.25% of C, 0.6-2.0% of Si, 1.5-3.0% of Mn, 0.01-0.1% of Al, 0.01-0.5% of Cr, 0.005-0.2% of Mo, 0.001-0.05% of P, 0.001-0.05% of S, 0.001-0.01% of N, 0.003-0.1% of Nb, 0.003-0.1% of Ti, 0.003-0.1% of V, and the remainder being Fe and other unavoidable impurities, and satisfying following relational expressions (1) and (2). [Relational Expression 1] 4.5&#x2264;[Mn]+12[sol.C]+2.5[Mo]+2[Cr]+300[B]+[V]&#x2264;5.3. [Relational Expression 2] [sol.C]=[C]&#x2212;(0.25[Ti]+0.13[Nb]+0.125[Mo]), 0.17&#x2264;[sol.C]&#x2264;0.22. (In relational expressions 1 and 2, each element symbol represents the content of each element in wt %).

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Gwangyang-si, South Korea

Sung-Il Kim