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Precipitation Hardening Martensitic Stainless Steel and Long Blade for Steam Turbine Using the Same

a technology of martensitic stainless steel and precipitation hardening martensitic stainless steel, which is applied in the direction of blade accessories, machines/engines, waterborne vessels, etc., can solve the problems of poor balance between strength and toughness, and achieve excellent texture stability, mechanical properties, and corrosion resistance.

Inactive Publication Date: 2014-04-17
MITSUBISHI HITACHIPOWER SYST LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention is about a type of stainless steel that has excellent mechanical properties and resistance to corrosion. It is made by a process called precipitation hardening, which involves adding a small amount of nitrogen to the steel to form special structures that make it stronger and more durable. The resulting steel has a smooth texture and is highly resistant to wear and corrosion.

Problems solved by technology

However, a balance between strength and toughness thereof is poor (refer to, e.g., JP-A-2005-194626).

Method used

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  • Precipitation Hardening Martensitic Stainless Steel and Long Blade for Steam Turbine Using the Same
  • Precipitation Hardening Martensitic Stainless Steel and Long Blade for Steam Turbine Using the Same
  • Precipitation Hardening Martensitic Stainless Steel and Long Blade for Steam Turbine Using the Same

Examples

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example 1

Preparation of Sample

[0036]Test samples were prepared to evaluate a relationship between the chemical composition of the precipitation hardening martensitic stainless steel of the present invention, tensile strength thereof, 0.02% yield strength, Charpy impact absorption energy, pitting potential, and micro-texture. Table 1 illustrates a chemical composition of each test sample.

[0037]First, raw materials were melted by using a high-frequency vacuum melting furnace (5.0×10−3 Pa or less, 1600° C. or higher) to obtain compositions listed in Table 1. The obtained ingot was hot-forged by using a press forging machine and a hammer forging machine, and formed into a square bar having a width×thickness×length of 100 mm×30 mm×1000 mm. Next, the square bar was cut and processed to a width×thickness×length of 50 mm×30 mm×120 mm, thereby giving stainless steel starting materials.

[0038]Next, the stainless steel starting materials were subjected to various heat treatments by using a box electric ...

example 2

[0046]The following describes the steam turbine long blade to which the alloy of the present invention is applied. In this embodiment, by using Alloy 1 illustrated in Table 1 of materials of the present invention, an axial-entry-type steam turbine long blade having a blade length of 48 inch was produced. As a method for producing the long blade, vacuum carbon deoxidation was first performed in a high vacuum state of 5.0×10−3 Pa or less to deoxidize molten steel by a chemical reaction of C+O→CO. Subsequently, the steel was formed into an electrode bar by extend forging. Electro-slag remelting was thus performed to give a high-grade steel ingot by self-dissolving the electrode bar by Joule heat generated upon the application of current at the time when this electrode bar was immersed in molten slag, and then coagulating it in a water-cooled die. Next, the steel ingot was hot-forged, and then press-forged by using a 48-inch blade die. After that, as a solution treatment, the resulting ...

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Abstract

A precipitation hardening martensitic stainless steel is provided with excellent mechanical property and corrosion resistance and contains, by mass, 0.1% or less of C; 0.1% or less of N; 10.0%˜15.0% of Cr; 10.0%˜15.0% of Ni; 0.5%˜2.5% of Mo; 1.0%˜3.0% of Al; 1.0% or less of Si; 1.0% or less of Mn, and the rest is Fe and inevitable impurities. A steam turbine long blade is made of the precipitation hardening martensitic stainless steel.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a precipitation hardening martensitic stainless steel having excellent texture stability, mechanical properties, and corrosion-resistance; and also a long blade for a steam turbine using the same.[0002]Recently, in terms of energy saving (e.g., the conservation of fossil fuel) and the prevention of global warming (e.g., the suppression of CO2 gas production), it has been demanded to improve the efficiency of a thermal power plant (e.g., efficiency improvement in a steam turbine). One of the effective measures for improving the efficiency of the steam turbine is to increase the size of a steam turbine long blade. In addition, an increase in the size of the steam turbine long blade is also expected to have secondary effects such as shortening a facility construction period, and reducing the resulting cost by decreasing the number of casings.[0003]A long blade material having both excellent mechanical properties and corr...

Claims

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Application Information

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IPC IPC(8): F01D5/28
CPCF01D5/28C21D1/18C21D1/26C21D6/004C21D9/0068C21D2211/004C21D2211/008C22C38/00C22C38/06C22C38/44
Inventor OIKAWA, SHINJIYODA, HIDEOARAI, MASAHIKODOI, HIROYUKI
Owner MITSUBISHI HITACHIPOWER SYST LTD
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