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Thick steel plate having excellent cryogenic toughness

A thick steel plate, extremely low temperature technology, applied in the field of thick steel plate, can solve problems such as non-brittle fracture rate

Inactive Publication Date: 2015-08-19
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the thick steel plate of Patent Document 3 has a maximum TS of 741 MPa at room temperature.
[0007] In addition, although the absorbed energy in the C direction is described in Patent Document 3, there is no description of the brittle fracture rate.

Method used

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  • Thick steel plate having excellent cryogenic toughness
  • Thick steel plate having excellent cryogenic toughness
  • Thick steel plate having excellent cryogenic toughness

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0193] Example 1: An example of a thick steel plate that satisfies the brittle fracture rate at -196°C ≤ 10%, the tensile strength TS > 741MPa, and the yield strength YS > 590MPa

[0194] Using a vacuum melting furnace (150kgVIF), melt the test steel with the composition shown in Table 1 (remainder: iron and unavoidable impurities, the unit is mass %), after casting, make 150mm×150mm by hot forging ×600mm ingot. In this example, misch metal containing about 50% of Ce and about 25% of La was used as the REM.

[0195] Next, after heating the above-mentioned ingot at 1100°C, it is rolled at a temperature above 830°C to a plate thickness of 75 mm, the finish rolling temperature (FRT) is set to 700°C, the SCT within 60 seconds after FRT: 650°C, and water cooling is performed. , thus rolled to a plate thickness of 25mm (reduction rate 83%). In addition, the average cooling rate at 800-500 degreeC was set to 19 degreeC / s, and cold rolling was carried out to the stop temperatu...

Embodiment 2

[0253] In this example, the brittle fracture rate at -233° C. was evaluated for some of the data used in Example 1 above (all are examples of the present invention).

[0254] Specifically, for the No. recorded in Table 3 (the No. in Table 3 corresponds to the No. in the above-mentioned Table 1 and Table 2), collect 3 test pieces from the t / 4 position and the W / 4 position, according to the following In the described method, the Charpy impact test at -233 degreeC was implemented and the average value of the brittle fracture rate was evaluated.

[0255] In this example, the case where the brittle fracture rate ≤ 50% was evaluated as being excellent in the brittle fracture rate at -233°C.

[0256] "High Pressure Gas", Volume 24, Page 181, "Extreme Low Temperature Impact Test of Austenitic Stainless Steel Cast Steel"

[0257] These results are described in Table 3.

[0258] 【table 3】

[0259] [table 3]

[0260]

[0261] Nos. 1 to 3, 6, 8, 9, 14, 18, and 20...

Embodiment 3

[0264] Example 3: An example of a thick steel plate satisfying the brittle fracture rate at -196°C ≤ 10%, the tensile strength TS > 830MPa, and the yield strength YS > 690MPa

[0265] Using a vacuum melting furnace (150kgVIF), melt the test steel with the composition shown in Table 4 (remainder: iron and unavoidable impurities, the unit is mass %), after casting, make 150mm×150mm×600mm by hot forging of ingots. In this example, misch metal containing about 50% of Ce and about 25% of La was used as the REM.

[0266] Next, after heating the above-mentioned ingot at 1100°C, it is rolled at a temperature above 830°C to a plate thickness of 75 mm, the finish rolling temperature (FRT) is set to 700°C, the SCT within 60 seconds after FRT: 650°C, and water cooling is performed. , thus rolled to a plate thickness of 25 mm (85% reduction ratio). In addition, the average cooling rate at 800-500 degreeC was set to 19 degreeC / s, and cold rolling was carried out to the stop temperat...

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Abstract

This thick steel sheet contains prescribed steel components, the Di value composed of the steel components is 2.5 or greater, the residual austenite phase (residual (γ)) remaining at -196°C is 2.0 to 12.0% by volume fraction, and the residual (γ) stability parameter composed of the components contained in the residual austenite at -196°C satisfies the condition of 3.1 or greater.

Description

technical field [0001] The present invention relates to a thick steel plate excellent in ultra-low temperature toughness. Specifically, the present invention relates to a thick steel plate having good toughness [especially toughness in the width direction (C direction)] at extremely low temperatures of -196°C or lower even when the Ni content is reduced to about 5.0 to 7.5%. The following description will focus on thick steel plates (typically storage tanks, transport ships, etc.) for liquefied natural gas (LNG) exposed to the above-mentioned extremely low temperature, but the gist of the thick steel plate of the present invention is not limited thereto. Instead, it is suitable for all thick steel plates used in applications exposed to extremely low temperatures below -196°C. Background technique [0002] Thick steel plates for LNG tanks used for storage tanks for liquefied natural gas (LNG) require not only high strength but also high toughness that can withstand extremely...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D6/00C22C38/58C21D8/02
CPCC22C38/02C22C38/58C22C38/04C21D8/02C22C38/14C22C38/005C22C38/08C22C38/16C22C38/06C22C38/44C21D9/46C21D6/00C22C38/48C22C38/46C22C38/12C22C38/42C22C38/001C22C38/00C22C38/50C22C38/54C22C38/002
Inventor 伊庭野朗名古秀德
Owner KOBE STEEL LTD
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