Posco

Postech Academy-industry Foundation

Posco Co., Ltd

Won-Hwi Lee

Kyoo-Young Lee

Joo-Hyun Ryu

Sea-Woong Lee

Sung-hak Lee

Nack-Joon Kim

Bruno C De Cooman

Seon-Jong Lee

Eun-Jung Seo

Byun-Mok Hwang

Jin-Ho Jung

Sang-Bae Lim

Sung-Hak Lee

The present invention relates to a solution for electroplating iron, comprising: iron ions comprising first iron ions and second iron ions; a complexing agent; and unavoidable impurities, wherein the amount of second iron ions among the iron ions is 5 to 60 wt %. According to the present invention, electroplating efficiency is high, there is no drop in electroplating efficiency due to a continuous plating operation, and sludge generation is prevented, and, thus, the plating solution is easily managed. Burning can be prevented even in a high current density operation, and, thus, a high-quality iron-plated layer can be achieved. The plating solution does not need to be replaced, as the concentration of second iron ions generated by a plating reaction is maintained to be constant, and, thus, the present invention is appropriate for a continuous plating process.

Solution for electroplating iron, and electroplated steel sheet manufactured by using same

One aspect of the present invention relates to an ultrahigh-strength steel sheet having an excellent yield ratio, comprising, by wt %, 0.3-0.5% of C, 2.0% (excluding 0%) of Si, 3.0-6.5% of Mn, 0.02% or less of P, 0.01% or less of S, 0.01-3.0% of Al, 0.02% or less (excluding 0%) of N, and the balance of Fe and other inevitable impurities, and a microstructure comprises 5-30% of remaining austenite by area fraction and comprises 5% or less of secondary martensite.

Ultrahigh-strength steel sheet having excellent yield ratio, and manufacturing method therefor

Provided is an ultra-high-strength steel sheet having an excellent hole expandability and yield ratio, including, in terms of wt %: 0.05-0.2% of carbon (C); 2.0% or less of silicon (Si); 4.1-9.0% of manganese (Mn); 0.05% or less (excluding 0%) of phosphorus (P); 0.02% or less (excluding 0%) of sulfur (S); 0.5% or less (excluding 0%) of aluminum (Al); 0.02% or less (excluding 0%) of nitrogen (N); and a balance of iron (Fe) and other inevitable impurities, wherein the following Equation 1 is satisfied, and wherein microstructures includes, in volume percentage, 10-30% or retained austenite, 50% or more of annealed martensite, and 20% or less of other phases including alpha martensite and epsilon martensite, Equation 1: C/12+Ti/48+Nb/93+V/51+Mo/96&#x2265;0.015.

Ultra-high-strength steel sheet having excellent hole expandability and yield ratio, and method of manufacturing the same

Provided is an ultra-high strength steel plate for automobiles and, more specifically, to an ultra-high strength steel plate having high formability and hole expandability, and a method for manufacturing the ultra-high strength steel plate. The ultra-high strength steel plate includes: by wt %, carbon (C): 0.04% to 0.17%, silicon (Si): 2% or less, manganese (Mn): 4% to 10%, phosphorous (P): 0.05% or less (excluding 0%), sulfur (S): 0.02% or less (excluding 0%), aluminum (Al): 0.5% or less (excluding 0%), nitrogen (N): 0.02% or less (excluding 0%), and a balance of iron (Fe) and inevitable impurities. Carbon (C) and manganese (Mn) satisfy Formula C+(Mn/25)&#x2264;0.46. The ultra high strength steel plate has a microstructure comprising retained austenite in a volume fraction of 20% or greater and annealed martensite in a volume fraction of 50% or greater.

Ultra-high strength steel plate having excellent formability and hole-expandability, and method for manufacturing same

Provided is an ultrahigh-strength steel sheet for a vehicle and, more specifically, to an ultrahigh-strength and high-ductility steel sheet having excellent yield ratio and a manufacturing method therefor. Provided is an ultrahigh-strength and high-ductility steel sheet for cold press forming and a manufacturing method therefor, the steel sheet ensuring ultrahigh strength and high ductility since an alloy component of steel and manufacturing conditions are controlled and, simultaneously, having excellent impact characteristics due to a high yield strength ratio (yield ratio). Provided is the steel sheet capable of satisfying formability and impact stability, which are required for a vehicle steel sheet for cold forming, and replacing a conventional steel sheet for hot press forming, thereby reducing manufacturing costs.

Ultra high-strength and high-ductility steel sheet having excellent yield ratio and manufacturing method therefor

Growing community of inventors

Gwangyang-si, South Korea

Won-Hwi Lee