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Thick steel plate

A thick steel plate and quality technology, applied in the field of thick steel plate, can solve the problem of HAZ toughness deterioration and achieve the effect of excellent HAZ toughness

Active Publication Date: 2018-12-21
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, the structure of the HAZ after cooling becomes coarse, and the toughness of the HAZ deteriorates.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0123] The present invention will be described more specifically by way of examples.

[0124]

[0125] Steels having the chemical compositions of test numbers Examples 1 to 28 and Comparative Examples 1 to 18 shown in Table 1 were melted through the actual manufacturing process. In this manufacturing process, the total amount of Fe in the slag is adjusted by blowing Ar gas from the top into the molten steel before the RH vacuum degassing treatment to cause the slag on the surface of the molten steel to react with the molten steel.

[0126] The flow rate of Ar gas was adjusted within the range of 100 to 200 L / min, and the blowing time was adjusted within the range of 5 to 15 minutes.

[0127] Afterwards, each element was added by the RH vacuum degasser to adjust the composition, and a 300mm slab was cast by continuous casting. The cast slab is heated in a heating furnace in the range of 1000-1100°C. After heating, it is hot-rolled at a temperature of 760°C or higher until i...

Embodiment 9

[0147] In Example 9, although the CTOD test result was acceptable, the YP and TS were low because the C content was close to the lower limit of the range of the present invention.

Embodiment 10

[0148] In Example 10, although the result of the CTOD test was acceptable, the YP and TS were low because the Si content was close to the lower limit of the range of the present invention.

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Abstract

A thick steel plate, the chemical composition of which comprises, in mass%, C in the amount of 0.01-0.20%, Si in the amount of 0.10-0.25%, Mn in the amount of 1.30-2.50%, P in the amount of 0.01% or less, S in the amount of 0.0010-0.0100%, Ti in the amount of 0.005-0.030%, Al in the amount of 0.003% or less, O in the amount of 0.0010-0.0050%, N in the amount of 0.0100% or less, Cu in the amount of0-0.50%, Ni in the amount of 0-1.50%, Cr in the amount of 0-0.50%, Mo in the amount of 0-0.50%, V in the amount of 0-0.10%, and Nb in the amount of 0-0.05%, with the remainder constituting Fe and impurities, wherein the steel also contains a composite inclusion in which MnS is present around a Ti oxide. The surface area ratio of MnS in a cross-section of the composite inclusion is at least 10% and less than 90%, the proportion which MnS constitutes along the peripheral length of the composite inclusion is at least 10%, and the number density of composite inclusions that have a particle diameter of 0.5-5.0 [mu]m is 10-100 / mm<2>. This thick steel plate exhibits excellent HAZ low-temperature properties during high heat input welding.

Description

technical field [0001] The present invention relates to thick steel plates. In particular, the present invention relates to a thick steel plate having excellent toughness in a welded heat-affected zone (Heat Affected Zone: hereinafter referred to as "HAZ") used for marine structures such as offshore oil and gas extraction equipment. Background technique [0002] In order to improve the safety and reliability of the fracture of the welded part, the toughness of thick steel plates used in various welded steel structures such as buildings, bridges, shipbuilding, pipelines, construction machinery, marine structures, storage tanks, etc., It gets stricter every year. In particular, in addition to the toughness of the base steel sheet, there is a similar demand for ensuring excellent HAZ toughness. [0003] In the HAZ, the closer to the fusion line, the higher the heating temperature at the time of welding. In particular, austenite grains are remarkably coarsened when heated to ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/58
CPCC21D8/0226C21D8/0263C22C38/001C22C38/02C22C38/04C22C38/06C22C38/08C22C38/14C22C38/16C22C38/18
Inventor 笠野和辉小栗正裕加茂孝浩
Owner NIPPON STEEL CORP
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