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Low alloy steel

A low-alloy steel and metallographic structure technology, applied in the field of low-alloy steel, to achieve effective characteristics, improve high-temperature creep strength and long-term creep ductility

Inactive Publication Date: 2008-09-03
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the steel proposed in JP-A-2004-107719 mentioned above has improved toughness, but there is still room for further improvement in achieving both properties of high-temperature creep strength and creep ductility.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0069] Twelve kinds of alloys having the chemical compositions shown in Table 1 were smelted in a vacuum induction melting furnace to obtain ingots with a diameter of 144 mm and 50 kg. When melting alloys, in order to control the properties of Nd-based inclusions, the method of deoxidation and Nd addition is changed.

[0070] In steel Nos. 8, 10 and 11 in the examples of the present invention (steel Nos. 1 to 5) and comparative examples, after adding Si iron and Mn iron, deoxidize with Al, then add Nd, and further add Mn-Si to for deoxygenation.

[0071] In Steel Nos. 6 and 7 in Comparative Examples, Nd was not added.

[0072] In steel No. 9 in the comparative example, after adding Nd, deoxidation was performed by adding Si iron, Mn iron, and Al. In addition, in steel No. 12 in the comparative example, Nd was added after deoxidation was performed by adding Si iron, Mn iron, and Al.

[0073] Table 1

[0074]

[0075] The obtained ingot was subjected to hot forging and ho...

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Abstract

Disclosed is a low alloy steel which has a defined chemical composition and has a metal structure composed of bentonite or martensite. In the low alloy steel, the timing of deoxidization or addition of Nd in the steel metal dissolution process is properly selected to allow an Nd inclusion to be present in a proper amount. Thus, the low alloy steel can achieve both a high temperature creep strength and a long-term creep ductility even under severe environments, which has been hardly achieved by a conventional steel. The low alloy steel can be widely used as a material for a heat-resistant structural element which is used under high temperature / high pressure conditions for a long period of time, such as a power plant boiler or turbine and a nuclear power plant.

Description

technical field [0001] The invention relates to a low-alloy steel with excellent high-temperature creep strength and creep ductility. The low-alloy steel of the present invention is suitable for use as boiler tubes for power generation, turbines, and heat-resistant structural members for nuclear power plants, chemical industry equipment, and the like. Background technique [0002] Boiler tubes and turbines for power generation, nuclear power generation equipment, and chemical industry equipment are used in high-temperature and high-pressure environments for a long time. Therefore, heat-resistant materials used in these devices are generally required to have excellent strength at high temperatures, corrosion resistance, oxidation resistance, and excellent toughness at normal temperature, etc. [0003] In recent years, thermal power plants have been reducing CO2 in order to prevent global warming 2 Therefore, it is necessary to improve thermal efficiency, and gradually build...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/22C22C38/54C21C7/04C21C7/06
CPCC21C7/0006C21C7/06C22C38/005C22C38/02C22C38/04C22C38/22C21D2211/002C22C38/002
Inventor 中岛崇河野佳织五十岚正晃
Owner NIPPON STEEL CORP
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