High-tensile thick steel plate for extremely low temperature and manufacturing method thereof

A manufacturing method and high-tension technology, applied in manufacturing tools, furnaces, heat treatment equipment, etc., can solve the problems of low temperature toughness reduction, austenite instability, expensive Ni alloying elements, etc., and achieve excellent cold workability and improved safety. Effect

Active Publication Date: 2022-03-01
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] However, Ni is an expensive alloy element, and therefore, from the viewpoint of cost reduction, development of a low-temperature steel sheet with a Ni content of less than 9% and toughness equivalent to or higher than that of a 9% Ni steel sheet is strongly desired.
[0004] Generally, when the Ni content of the low-temperature steel sheet is reduced, the austenite becomes unstable in the low-temperature region, so the low-temperature toughness decreases, and it is difficult to ensure the high level of safety required for LNG storage tanks

Method used

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  • High-tensile thick steel plate for extremely low temperature and manufacturing method thereof
  • High-tensile thick steel plate for extremely low temperature and manufacturing method thereof
  • High-tensile thick steel plate for extremely low temperature and manufacturing method thereof

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Embodiment

[0156] A high-tensile high-tensile steel plate for extremely low-temperature use was manufactured in accordance with the procedure described below, and properties of the obtained high-tensile-strength steel plate for extremely low-temperature use were evaluated.

[0157] First, molten steel having the composition shown in Table 1 was melted in a converter, and a billet (thickness: 250 mm) was produced as a billet material by a continuous casting method. In addition, the Ac1 point (°C) obtained by the above formula (1) and the Ac3 point (°C) obtained by the formula (2) are shown in Table 1 together.

[0158] Next, the obtained slabs were heated to the heating temperatures shown in Table 2, and hot-rolled to obtain hot-rolled steel sheets with the thicknesses shown in Table 2. Next, first accelerated cooling is performed on the hot-rolled steel sheet. Table 2 shows the average cooling rate and cooling stop temperature of the above-mentioned first accelerated cooling. In additi...

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Abstract

An object of the present invention is to provide a steel sheet for low temperature use having a Ni content of less than 9%, a toughness equal to or higher than that of a 9% Ni steel sheet, and excellent cold workability. With a specified composition, the microstructure at the 1 / 4 position of the plate thickness consists of (1) a matrix composed of tempered martensite or tempered martensite and bainite and (2) residual austenite dispersed in the above matrix 1 / 4 of the plate thickness, the volume ratio of retained austenite in the 1 / 4 position of the plate thickness is more than 11% and 20% or less, and after performing cryogenic treatment in liquid nitrogen at -196°C for 15 minutes, 1 / 4 of the plate thickness The volume fraction of retained austenite at the 4th position exceeds 11% and is 20% or less.

Description

technical field [0001] The present invention relates to a high-tensile high-tensile steel plate for ultra-low temperature, particularly a high-tensile high-tensile steel plate for ultra-low temperature that is excellent in ultra-low temperature toughness and cold workability, and can be suitably used for applications such as tanks for storing liquefied natural gas (LNG). In addition, the present invention relates to a method of manufacturing the above-mentioned high-tensile-strength steel plate for extremely low temperature use. Background technique [0002] Tanks for LNG storage often require a high degree of safety. Therefore, steel sheets for low temperature used in tank bodies are required to have excellent toughness at the temperature at which LNG becomes a liquid (approximately -162°C). In addition, severe processing such as forming into a cylindrical pipe is performed in the manufacture of the tank, and thus cold bending workability is also required for the steel she...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/00C21D8/02C22C38/08C22C38/58
CPCC22C38/00C22C38/58C22C38/08C21D8/02C22C38/04C22C38/02C21D8/0247C21D9/46C21D2211/008C21D2211/002
Inventor 佐藤祐也村上善明伊木聪
Owner JFE STEEL CORP
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