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Ferritic heat-resistant steel

A technology of ferritic and heat-resistant steel, applied in the field of ferritic heat-resistant steel

Inactive Publication Date: 2008-03-26
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the invention disclosed in the above-mentioned documents does not aim at improving the creep fatigue strength of heat-resistant steel.

Method used

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Embodiment

[0105] Steel having the chemical composition shown in Table 1 was melted using a vacuum induction melting furnace to form a 50 kg steel ingot with a diameter of 144 mm. Codes A to M represent steels of the present invention, and codes 1 to 22 represent comparative steels. For steels with codes A to M and steels with codes 15 to 20, Nd is added immediately before casting after sufficiently deoxidizing with C, Si, Mn, and Al. Nd was added to steel code 21 from the start of melting, and Nd was added to steel code 22 after deoxidation by carbon (C) only.

[0106] The above steel ingot was hot forged and hot rolled to form a 20 mm thick plate. Next, after holding at 1050 degreeC temperature for 1 hour, air cooling (AC) was performed. Further, it was kept at 760° C. to 780° C. for 3 hours, and air-cooled (AC) tempering was performed. A sample was selected from the above-mentioned plates, and the longitudinal direction of the sample was oriented in the rolling direction, and a cre...

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Abstract

Disclosed is a heat-resistant steel which is excellent in high-temperature long-term creep strength and creep-fatigue strength. Specifically disclosed is a heat-resistant steel having a composition consisting of, in mass%, 0.01-0.13% of C, 0.15-0.50% of Si, 0.2-0.5% of Mn, not more than 0.02% of P, not more than 0.005% of S, more than 8.0% but less than 12.0% of Cr, 0.1-1.5% of Mo, 1.0-3.0% of W, 0.1-0.5% of V, 0.02-0.10% of Nb, not more than 0.015% of sol. Al, 0.005-0.070% of N, 0.005-0.050% of Nd, 0.002-0.015% of B, and the balance of Fe and impurities. As some of the impurities, less than 0.3% of Ni, less than 0.3% of Co and less than 0.1% of Cu are contained in the heat-resistant steel. This ferritic heat-resistant steel contains Nd inclusions at a density of not less than 10,000 inclusions / mm<3>. This steel may further contain one or more elements selected from Ta, Hf, Ti, Ca and Mg in addition to the above-described components.

Description

technical field [0001] The invention relates to a ferritic heat-resistant steel. More specifically, it relates to a ferritic heat-resistant steel excellent in high-temperature long-term creep strength and creep fatigue strength. The heat-resistant steel of the present invention is suitable for use in steel pipes for heat exchange, steel plates for pressure vessels, turbine materials, and the like used in high-temperature and high-pressure environments such as boilers, nuclear power generation equipment, and chemical industry equipment. Background technique [0002] For heat-resistant steels used in high-temperature and high-pressure environments such as boilers, nuclear power generation equipment, and chemical industrial equipment, high-temperature creep strength, creep fatigue strength, corrosion resistance, and oxidation resistance are generally required. [0003] High-Cr ferritic steel has better strength and corrosion resistance than low-alloy steel at a temperature of ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/32
CPCC22C38/02C22C38/04C22C38/22C22C38/24C22C38/002C22C38/005C22C38/26
Inventor 吉泽满五十岚正晃宫原光雄野口泰隆
Owner NIPPON STEEL CORP
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