Cryogenic high-tensile thick steel sheet and method for producing same

A manufacturing method and high-tensile technology, applied in the direction of manufacturing tools, furnace types, furnaces, etc., can solve the problems of low-temperature toughness reduction, austenite instability, expensive Ni alloy elements, etc., and achieve excellent cold workability, improved safety, Effective effect of stabilization

Active Publication Date: 2021-01-15
JFE STEEL CORP
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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.
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Method used

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  • Cryogenic high-tensile thick steel sheet and method for producing same
  • Cryogenic high-tensile thick steel sheet and method for producing same
  • Cryogenic high-tensile thick steel sheet and method for producing same

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[0155] Example

[0156] According to the procedure described below, a high-tensile steel sheet for cryogenic temperature was produced, and the properties of the obtained high-tensile steel sheet for cryogenic temperature were evaluated.

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

[0158] Next, the obtained slab was heated to the heating temperature shown in Table 2, and hot-rolled to obtain a hot-rolled steel sheet having the thickness shown in Table 2. Next, the first accelerated cooling is performed on the above-mentioned hot-rolled steel sheet. Table 2 shows the average cooling rate and cooling stop temperature of the first accelerated coo...

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Abstract

The present invention addresses the problem of providing a cryogenic steel sheet having a Ni content of less than 9% and also having both of toughness at the same level or a higher level as or than that of a 9%-Ni steel sheet and excellent cold workability. A cryogenic high-tensile thick steel sheet having a specified ingredient component, wherein the micro-structure at a position of one-fourth the thickness of the steel sheet comprises (1) a matrix composed of tempered martensite or a matric composed of tempered martensite and bainite and (2) retained austenite dispersed in the matrix, the content ratio of the retained austenite at a position of one-fourth the thickness of the steel sheet is more than 11% by volume and equal to or less than 20% by volume, and the content ratio of the retained austenite at a position of one-fourth the thickness of the steel sheet becomes more than 11% by volume and equal to or less than 20% by volume after the steel sheet is subjected to such a subzerotreatment that the steel sheet is retained for 15 minutes in liquid nitrogen at -196 DEG C.

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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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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