High tensile strength steel and marine structure having excellent weld toughness

Inactive Publication Date: 2007-03-08
SUMITOMO METAL IND LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0038] According to the present invention, it is possible to manufacture a high tensile strength steel having excellent weldability and a yield stress of at least 420 N/mm2 which can be welded with a welding heat input of at least 300 kJ/cm by a welding method such as electrogas arc welding,

Problems solved by technology

This is thought to be because when the N/Al ratio is too small, coarse AlN precipitates, and not only does this itself have an adverse effect on toughness, but also it impedes fine dispersion

Method used

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Examples

Experimental program
Comparison scheme
Effect test

examples

[0090] In this example, steel slabs having a thickness of 300 mm and having the chemical compositions shown in Table 1 and Table 2 were prepared by continuous casting. In order to control inclusions at the center of the thickness of a steel plate, during continuous casting, the temperature of molten steel was not made too high, and the difference thereof from the solidification temperature which was determined by the molten steel composition was controlled so as to be at most 50° C. and electromagnetic stirring just before solidification and reduction in thickness at the time of solidification were carried out.

[0091] Table 3 and Table 4 show the working conditions of steel slabs having the chemical compositions shown in Table 1 and Table 2. The working conditions shown in Table 3 and Table 4 are for the steel slabs having the chemical compositions shown in Table 1 and Table 2, respectively.

[0092] After a slab with a thickness of 300 mm was heated at the indicated heating temperatu...

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PUM

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Abstract

In order to provide a high tensile strength steel having excellent low temperature toughness and which can withstand large heat input welding, a steel comprises, in mass percent, C: 0.01-0.10%, Si: at most 0.5%, Mn: 0.8-1.8%, P: at most 0.020%, S: at most 0.01%, Cu: 0.8-1.5%, Ni: 0.2-1.5%, Al: 0.001-0.05%, N: 0.0030-0.0080%, O: 0.0005-0.0035%, if necessary at least one of Ti: 0.005-0.03%, Nb: 0.003-0.03%, and Mo: 0.1-0.8%, and a remainder of Fe and impurities, and the N/Al ratio is 0.3-3.0.

Description

TECHNICAL FIELD [0001] The present invention relates to a high tensile strength steel and a marine structure, and particularly to a high tensile strength steel for welding and a marine structure having excellent weld toughness. [0002] More specifically, the present invention relates to a high tensile strength steel for welding for use in welded structures such as buildings, civil engineering projects, construction equipment, ships, pipes, tanks, and marine structures, and particularly to a high tensile strength steel for welding to construct marine structures as well as to a marine structure thus constructed. For example, it relates to a thick, high strength steel plate with a thickness of at least 50 mm and a yield strength of at least 420 N / mm2 and to a marine structure using such a plate. BACKGROUND ART [0003] In recent years, as energy demands show a tendency to increase more and more, the search for undersea oil resources is being actively carried out. Marine structures used fo...

Claims

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Application Information

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IPC IPC(8): C22C38/16C21D8/02C22C38/00C22C38/58
CPCC22C38/02C22C38/48C22C38/44C22C38/42C22C38/001C22C38/002C22C38/005C22C38/58
Inventor KAMO, TAKAHIROURABE, TAKESHINAKAMURA, HIROFUMIOHNISHI, KAZUSHIHAMADA, MASAHIKO
Owner SUMITOMO METAL IND LTD
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