JPS61223169A - Shaft of turbine rotor - Google Patents

Abstract

PURPOSE:To maintain the ductility at high temp. such as >=600 deg.C temp. of steam and to improve the reliability by using a heat resistant Fe alloy contg. prescribed percentages of C, Si, Mn, Cr, Ni, Mo, etc. CONSTITUTION:The shaft of a turbine rotor is made of a heat resistant Fe alloy contg., by weight, <=0.1% C, <=0.5% Si, <=2% Mn, 10-20% Cr, 20-30% Ni, 1-3% Mo, 0.1-0.5% V, 0.5-2% Ti, <=0.5% Al, 0.001-0.01% B and 0.005-0.1% Zr. The shaft has superior ductility at high temp. such as >=600 deg.C temp. of steam and improved reliability.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a turbine rotor shaft having high temperature ductility.

[Technical background of the invention and its problems]

Conventional steam turbines have a steam temperature of 566C or less, and the materials for the rotor shaft include Cr-Mo-V steel and 1
20r base steel etc. have been mainly used. However, from the standpoint of improving thermal efficiency, the steam conditions for steam turbines are at a high temperature. In this case, in a high-temperature steam turbine with a steam temperature of 600C or higher, conventional Cr-Mo-
V steel and 12cr base steel have low creep rupture strength, and materials with better high temperature strength are required. The r' phase (N
There are Fe-based heat-resistant alloys JII9SUI (660, etc.) strengthened by I, (TJ, person 1)), but this type of strong precipitation-strengthened heat-resistant alloy beam has a high 9-ply breaking strength C, but has low ductility at high temperatures. It has the disadvantage of being inferior, and there is a problem with reliability as a turbine rotor shaft.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a highly reliable steam turbine rotor shaft having immersed high-temperature ductility at steam temperatures of 600C or higher.

[Summary of the invention]

In order to achieve the above object, the turbine rotor shaft of the present invention has a weight percentage of C001 or less, Old 0.6 or less, Mn2 or less, and Cr 10 to 20. Ni 20-3
0, Mo 1.0-3.0% V 0.1-0.5,
Ti 0.5-2.0, human 10.5 or less, B 0.
001~0.01, Zr 0.005~0.1,
It is characterized in that it is formed of an Fe-based heat-resistant alloy consisting of the remainder pe and incidental impurities. The steam turbine rotor of the present invention is made of an Fe-based heat-resistant alloy having a specific composition as described above. The purpose of adding each component in the alloy and the reason for limiting the composition are as follows.

C is an essential element for increasing high-temperature strength, and high-temperature strength improves as the amount of C increases, but on the other hand, if there is too much C, it reacts with Ti and forms coarse carbides of MCW, which deteriorates the alloy. Since it reduces ductility, the amount of C is set to 0.1 S or less.

Si acts as a deoxidizing agent, but when added in large amounts, N
Since it combines with L and TI and precipitates as a G phase at one grain boundary, reducing the ductility of the alloy, it is set to 0.6 or less.

Mn acts as a deoxidizing agent, but if added in a large amount, the oxidation resistance deteriorates, so the amount added is limited to 2% or less.

Or is an effective element that forms a healthy oxidation-resistant film and imparts oxidation and corrosion resistance to materials, but if it is less than 101, sufficient oxidation and corrosion resistance cannot be obtained; If the length exceeds 10 to 20 m, σ phase, which is a brittle phase, will be generated during long-term use at high temperatures.

Ni is a necessary element for stabilizing austenite, and also combines with Ti and AI to form an intermetallic compound r' phase (Ni3 (Ti, human 1)) to improve high-temperature strength. is necessary. For this purpose, 201 or more is required for the above range of cr*, and a higher number is preferable, but it is expensive, so the upper limit is set at 3o- for profitability.

MO is an element that dissolves in the austenite phase and is effective for solid solution strengthening. If it is less than f1, the effect cannot be obtained,
Also, if added in a large amount, the austenite matrix becomes unstable and the high temperature ductility decreases, so the range is 0.6 to 3.
Let it be 0chi.

Ti acts as a deoxidizing agent, and together with Nl, it forms the intermetallic compound r' phase (Nl, ('f'l, Renfeng)).
C is an essential element, but if it is less than 0.5 S, the amount of r' phase precipitated is small and its effect cannot be obtained sufficiently. Furthermore, if added in a large amount, the η phase (Ntm'rt) will precipitate in layers from the grain boundaries, impairing ductility, so it should be set at 0.5 to 2.01. .

Ni is an important element that imparts oxidation resistance and forms the r' phase (Ni, (TI, Mu1)) with N[, TI, but when added in large amounts it reduces ductility.
0.5 S or less.

(2) is an effective element for increasing high-temperature notch toughness and forming carbides to improve high-temperature strength; 0.1 to 0.
5-.

B segregates to the grain boundaries, is effective in strengthening the grain boundaries, and improves high-temperature ductility. To achieve this, a value of 0.001- or more is required, but too much will impair hot workability, so the upper limit should be set to 0.001- or more.
．． 01%.

Zr is an effective element for strengthening grain boundaries and increasing both Lubutture strength and high-temperature ductility.

If it is less than 0.005%, it has no effect, and if it is added in a large amount, it impairs hot workability, so the content is set at 0.006 to 0.1 inch.

In order to obtain the turbine rotor shaft of the present invention, first, various raw material metals are mixed and melted in a vacuum or in the atmosphere, and after deoxidation, a molten Pa-based heat-resistant alloy having substantially the above composition is obtained. This can then be cast into a steel ingot and then TT forged to form a material in the shape of a turbine rotor shaft, but it is not possible to apply vacuum arc remelting or electroslag remelting to this steel ingot. This is preferable in terms of high-temperature ductility. The turbine rotor shaft of the present invention can be obtained by forging the steel ingot produced in this manner and subjecting it to necessary heat treatment.

[Embodiments of the invention]

The present invention will be explained in more detail below using examples. Four types of alloy samples having the compositions shown in Table 1 were each melted in a high frequency furnace, and B8B was remelted using this as an electrode to obtain a steel ingot. This was upset and forged to obtain a forged material, which was then subjected to the heat treatment shown in Table 1 and subjected to a tensile test and a Loveture test. The results are shown in Tables 2 and 3. Example 1 of the present invention
Comparing Example 3 with Comparative Example, the tensile strength and yield strength at room temperature and 650C are the same, but the tensile elongation at break and the area of area at room temperature and high temperature, as well as the Labourture elongation and area of area, are significantly improved by 30 to 60 - respectively. There is. Also, the third
The rupture life shown in the table is also that Examples 1 to 3 are approximately equal to or superior to the comparative example.

(Leaving space below) Table 2 Table 3 [Effects of the invention] As is clear from the results of the above examples, the turbine rotor shaft of the present invention has better room temperature and ζ resistance than conventional materials.
It has two high-temperature elongation and narrowing properties, and its Loveture life is as good as or better than conventional materials. Therefore, the turbine rotor shaft of the present invention can be said to be extremely reliable as a rotor shaft for a steam turbine used at 600C or higher. Note that the rotor shaft according to the present invention can be used not only as a steam turbine rotor but also as a gas turbine rotor.

Claims (1)

[Claims] Weight ratio: C0.1% or less, Si0.5% or less, Mn2
% or less, Cr10-20%, Ni20-30%, Mo1
．． 0-3.0%, V0.1-0.5%, Ti0.5-2
．． 0%, Al 0.5% or less, B 0.001-0.01%
, 0.005 to 0.1% Zr, the balance being Fe and incidental impurities.