Method for manufacturing low-carbon 9Ni steel thick plate

Abstract

The invention relates to a method for preparing a low carbon 9 nickel steel thick plate, the steps are that: steelmaking, the components which are weighted by weight percentages are that carbon is 0.02-0.04 percent, silicon is 0.2-0.3 percent, manganese is 0.4-0.7 percent, sulfur is equal or less than 0.005 percent, phosphorus is equal or less than 0.01 percent, nickel is 8.9-9.5 percent, the allowance is ferrum and impurities, and the components are made into steel. Red charge: molten steel is cast and is stood for 5 minutes and is red charged into a heating furnace. Hot rolling: module ingots are rolled in two stages. On-line heat treatment: when finish rolling temperature is in a dual-phase region, quenching after rolling and tempering heat treatment are used, when the finish rolling temperature is in an austenite region, the quenching after rolling, quenching after solid solution and the tempering heat treatment are used or the quenching after rolling, the quenching after solid solution, dual-phase region quenching and the tempering heat treatment or the quenching after keeping temperature in the dual-phase region for 10-20 minutes are used, and then water-cooling is done after tempering whose temperature is kept for 1 hour in 580 DEG C. The invention has the advantages of short technological process, low producing cost, and high low-temperature flexibility and other mechanical properties of 9 nickel steel.

Description

technical field [0001] The invention relates to a steel rolling process, in particular to a method for preparing low-carbon 9Ni steel thick plates mainly by red feeding, hot charging, low-temperature controlled rolling and on-line heat treatment after rolling. Background technique [0002] With the adjustment of the energy structure, natural gas acts as a clean energy, and its proportion will increase in the future. In order to facilitate transportation and storage, natural gas is generally liquefied into liquefied natural gas (LNG). The terminal of LNG is a tank with a horizontal bottom and a huge storage capacity. The main structural materials of the walls and bottom are 9Ni series low-temperature steel wide and thick plates. are joined together by welding. Therefore, the 9Ni steel thick plate not only needs to have a high strength index, but also needs to have good low-temperature performance in its weld seam and heat-affected zone. In the 35 years since 1970, the low-t...

AI Technical Summary

Problems solved by technology

5Ni and 9Ni series low-temperature steels have also received attention. The service temperatures of these two steels can reach -170°C and -196°C respectively, but they have not been localized.

[0006] After searching the domestic patent database, 123 technical invention patents related to LNG were found, but no patent authorization for 9Ni steel wide and thick plate production technology and material design required by LNG facilities was found.

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