Posco

Hee-Goon Noh

Hak-Cheol Lee

Jong-Kyo Choi

In-Gyu Park

Hong-Ju Lee

In-Shik Suh

Soon-Gi Lee

Hyun-Kwan Cho

Kyung-Keun Um

Woo-Kil Jang

Young-Hwan Park

Provided are an austenitic steel having excellent machinability and ultra-low temperature toughness in a weld heat-affected zone including 15 wt % to 35 wt % of manganese (Mn), carbon (C) satisfying 23.6C+Mn&#x2265;28 and 33.5C&#x2212;Mn&#x2264;23, 5 wt % or less (excluding 0 wt %) of copper (Cu), chromium (Cr) satisfying 28.5C+4.4Cr&#x2264;57 (excluding 0 wt %), and iron (Fe) as well as other unavoidable impurities as a remainder, wherein a Charpy impact value of a weld heat-affected zone at &#x2212;196&#xb0; C. is 41 J or more, and a method of manufacturing the steel. According to the present invention, a low-cost ultra-low temperature steel may be obtained, a stable austenite phase may be formed at low temperature, carbide formation may be effectively suppressed, and a structural steel having excellent machinability and ultra-low temperature toughness in a weld heat-affected zone may be provided.

Austenitic steel having excellent machinability and ultra-low temperature toughness in weld heat-affected zone, and method of manufacturing the same

There are provided a wear resistant austenitic steel having superior machinability and toughness in weld heat affected zones and a method for producing the austenitic steel. The austenitic steel includes, by weight %, manganese (Mn): 15% to 25%, carbon (C): 0.8% to 1.8%, copper (Cu) satisfying 0.7C-0.56(%)&#x2266;Cu&#x2266;5%, and the balance of iron (Fe) and inevitable impurities, wherein the weld heat affected zones have a Charpy impact value of 100 J or greater at &#x2212;40&#xb0; C. The toughness of the austenitic steel is not decreased in weld heat affected zones because the formation of carbides during welding is suppressed, and the machinability of the austenitic steel is improved so that a cutting process may be easily performed on the austenitic steel. The corrosion resistance of the austenitic steel is improved so that the austenitic steel may be used for an extended period of time in corrosive environments.

Wear resistant austenitic steel having superior machinability and toughness in weld heat affected zones thereof and method for producing same

The present invention provides steel containing manganese and nickel that is used as a structural material for a cryogenic storage container for liquefied natural gas (LNG) or the like, and a manufacturing method thereof; and more particularly, to steel having good cryogenic temperature toughness and also high strength by adding low-cost Mn instead of relatively expensive Ni at an optimized ratio, refining a microstructure through controlled rolling and cooling, and precipitating retained austenite through tempering, and a manufacturing method of the steel. To achieve the object, the technical feature of the present invention is a method of manufacturing high-strength steel with cryogenic temperature toughness. In the method, a steel slab is heated to a temperature within a range of 1,000 to 1,250&#xb0; C., wherein the steel slab includes, by weight: 0.01-0.06% of carbon (C), 2.0-8.0% of manganese (Mn), 0.01-6.0% of nickel (Ni), 0.02-0.6% of molybdenum (Mo), 0.03-0.5% of silicon (Si), 0.003-0.05% of aluminum (Al), 0.0015-0.01% of nitrogen (N), 0.02% or less of phosphorous (P), 0.01% or less of sulfur (S), with a remainder of iron (Fe) and other unavoidable impurities. Then, the heated slab is finish-rolled at a temperature of 950&#xb0; C. or less at a rolling reduction rate of 40% or more. The rolled steel is cooled to a temperature of 400&#xb0; C. or less at a cooling rate of 2&#xb0; C./s or more. Thereafter, the steel is tempered for 0.5-4 hours to a temperature within a range of 550 to 650&#xb0; C. after the cooling.

High-strength steel material having outstanding ultra-low-temperature toughness and a production method therefor

Growing community of inventors

Pohang-si, South Korea

Hee-Goon Noh