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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, which is applied to the supporting elements of blades, furnace types, mechanical equipment, etc., can solve the problems of large amount of Cr addition, poor balance of strength and toughness, etc., and achieve excellent structural stability Effect

Inactive Publication Date: 2014-05-07
MITSUBISHI HITACHIPOWER SYST LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Precipitation-hardening martensitic stainless steel has a large amount of Cr added and a small amount of C added, so it has excellent corrosion resistance, but the balance between strength and toughness is poor (for example, refer to Patent Document 1)

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

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0043] (Sample production)

[0044] In order to evaluate the correlation between the chemical composition of the precipitation-hardening martensitic stainless steel of the present invention, tensile strength, 0.02% yield point, Charpy impact absorbed energy, pitting potential, and microstructure, samples were produced. Table 1 shows the chemical composition of each sample.

[0045] First, use a high-frequency vacuum melting furnace (5.0×10 -3 Pa or less, 1600° C. or more), the raw materials are melted so that the composition shown in Table 1 is obtained. The obtained ingot was hot-forged using a press forging machine and a hammer forging machine, and formed into a square bar of width×thickness×length=100mm×30mm×1000mm. Next, the square bar was cut and processed into width×thickness×length=50mm×30mm×120mm, which was used as a stainless steel raw material.

[0046] Next, various heat treatments were performed on each stainless steel raw material using a box-type electric furn...

test approach ）

[0048] For the tensile test, a test piece (distance between points: 30 mm, outer diameter: 6 mm) was prepared from each sample obtained above, and it was performed at room temperature according to JIS Z2241. As for the judgment criteria of tensile strength and 0.02% yield point, 1500 MPa or more and 1000 MPa or more were evaluated as "pass", and values ​​smaller than the value were evaluated as "failure". In addition, elongation and reduction of area were evaluated as "pass" if they were 10% or more and 30% or more, respectively, and those that were less than the values ​​were evaluated as "failure".

[0049] For the measurement of Charpy impact absorbed energy, a test piece having a 2 mm V-notch was prepared from each sample obtained above, and a Charpy impact test was performed at room temperature according to JIS Z2242. As for the judgment standard of the Charpy impact absorbed energy, 20 J or more was evaluated as "acceptable", and a value smaller than the value was evalua...

Embodiment 2

[0059] The steam turbine long blade using the present invention will be described. In the present embodiment, Alloy 1 described in Table 1, which is an inventive material, was used to produce long blades for an axial intake type steam turbine with a blade length of 48 inches. As a method of making long blades, first, at 5.0×10 -3 In the high vacuum state below Pa, through the chemical reaction of C+O→CO, vacuum carbon deoxidation is carried out to deoxidize molten steel. Next, it is formed into an electrode rod by forging and stretching. Electroslag remelting is performed by immersing the electrode rod in molten slag, self-melting it by Joule heat generated when an electric current is applied, and solidifying it in a water-cooled mold to obtain a high-quality steel block. Next, after hot forging, press forging is performed using a 48-inch blade die. Then, as a solution treatment, after heating and holding at 980° C. for 2.0 hours, forced cooling was performed to perform rap...

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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 (10) is made of the precipitation hardening martensitic stainless steel.

Description

technical field [0001] The present invention relates to a precipitation-hardening martensitic stainless steel having excellent structural stability, mechanical properties, and corrosion resistance, and a steam turbine long blade using the same. Background technique [0002] In recent years, from energy saving (e.g. saving fossil fuels) and preventing global warming (e.g. suppressing CO 2 From the viewpoint of the amount of gas produced), it is desired to improve the efficiency of thermal power plants (for example, to improve the efficiency of steam turbines). As one of the effective means to improve the efficiency of the steam turbine, the long blades of the steam turbine can be made longer and larger. In addition, as the long blades of the steam turbine become longer and larger, the secondary effects of shortening the equipment construction period and cost reduction due to the reduction in the number of cylinders can also be expected. [0003] In order to improve the reli...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/44F01D5/28
CPCC21D2211/008C21D9/0068C22C38/44F01D5/28C21D6/004C21D2211/004C21D1/26C21D1/18C22C38/00C22C38/06
Inventor 及川慎司依田秀夫新井将彦土井裕之
Owner MITSUBISHI HITACHIPOWER SYST LTD
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