KR20140118690A - Ferritic oxide dispersion strengthened alloy with enhanced room temperature and high temperature strength and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a ferritic oxide dispersion strengthened alloy having enhanced room temperature and high temperature strength, which includes 12-20 wt% of Cr, 0.1-0.5 wt% of Y_2O_3, 0.1-4 wt% of W, 0.5-2 wt% of Mo, 0.1-0.3 wt% of Ti, 0.02-0.3 wt% of Zr, and a remainder consisting of Fe, and a method of preparing the same. The ferritic oxide dispersion strengthened alloy according to the present invention includes 12-20 wt% of Cr, 0.1-0.5 wt% of Y_2O_3, 0.1-4 wt% of W, 0.5-2 wt% of Mo, 0.1-0.3 wt% of Ti, 0.02-0.3 wt% of Zr, and a remainder consisting of Fe. The sum of Ti and Zr in content is 0.5wt% or less. Accordingly, the ferritic oxide dispersion strengthened alloy has an excellent tensile property at the room temperature and the high temperature, especially at 700°C, so that the ferritic oxide dispersion strengthened alloy is available to power generation Ultra-critical steam generator parts (rotor, shaft, etc.) and a material for engine parts for aircraft (disc, nozzle, etc.). Further, it is expected that the ferritic oxide dispersion strengthened alloy is available to reactor core structural components (nuclear fuel cladding tubes, ducts, wires, such as end caps) of nuclear power systems, such as sodium-cooling fast reactors.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a ferritic oxide-dispersed reinforcing alloy having improved room temperature and high-temperature strength, and a method of manufacturing the ferritic-

Base alloys of yttria (Y ₂ O ₃₎ based - the present invention is the room temperature and high temperature strength, an improved ferritic oxide-dispersion strengthened alloys and a method, and more particularly to iron (Fe) - chromium (Cr) And a ferrite-based oxide-dispersed reinforcing alloy (B) containing tungsten (W) and molybdenum (Mo) as the solid solution strengthening elements and titanium (Ti) and zirconium And a method for producing the same.

Oxide dispersion strengthened (ODS) alloy is an alloy that uniformly disperses oxides such as Y ₂ O ₃ in the matrix to improve the strength at high temperature. Recently, Oxide dispersion strengthened (ODS) Fuel bundles, ducts, wires, etc.) and structural parts for thermal power generation (gas turbine blades, shafts, etc.). In this oxide-dispersed strengthened alloy, finely dispersed oxides of a nanometer-scale size have excellent thermal stability at high temperatures and interfere with the movement of dislocations in a high temperature stress atmosphere, thereby dramatically improving the creep strength at high temperatures do.

However, the conventional oxide-dispersed reinforced alloy has a sudden decrease in strength at 650 ° C or higher as well as strength at room temperature, which is pointed out as a problem in long-term use.

In order to solve such a problem, it has been proposed to use a ferrite-chromium (Cr) -yttria (Y ₂ O ₃ ) alloy which does not soften even when the temperature rises, Various methods such as adding a tungsten (W) as a solid solution strengthening element and adding a trace alloy element such as vanadium (V) or niobium (Nb) thereto (see Korean Patent Laid-Open No. 10-2012-0118312) However, the effect of improving the high-temperature strength characteristics of the oxide-dispersed reinforced alloy produced by the above-described methods is insignificant, and it is necessary to develop an oxide-dispersed reinforcing alloy having excellent tensile strength.

The present invention has been conceived to solve the problems of the prior art as described above, chromium (Cr) 12 ~ 20% by weight of yttria _{(Y 2 O 3) 0.1 ~} 0.5 wt%, tungsten (W) 0.1 ~ 4 parts by weight Ferritic oxide having improved tempera- ture at room temperature and high temperature, containing 0.5 to 2 wt% of molybdenum (Mo), 0.1 to 0.3 wt% of titanium (Ti), 0.02 to 0.3 wt% of zirconium (Zr) And a method for producing the same.

However, the technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention chromium (Cr) 12 ~ 20% by weight of yttria _{(Y 2 O 3) 0.1 ~} 0.5 wt%, tungsten (W) 0.1 ~ 4 weight%, molybdenum (Mo) 0.5 ~ 2 weight%, titanium (Ti ) Containing 0.1 to 0.3% by weight of zirconium (Zr), 0.02 to 0.3% by weight of zirconium (Zr) and the balance of iron (Fe) at room temperature and high temperature.

In one embodiment of the present invention, the ferrite-based oxide-dispersed reinforcing alloy is characterized in that the sum of titanium (Ti) and zirconium (Zr) is 0.5% by weight or less.

In another embodiment of the present invention, the ferrite-based oxide-dispersed reinforcing alloy is used as a structural component material including a rotor, a shaft, an engine disk, a nozzle, and a fuel cladding for a high-speed furnace of a super critical pressure steam generator for thermal power generation .

The present invention also provides a method for producing a ferritic oxide-dispersed strengthened alloy having improved strength at room temperature and high temperature, comprising the steps of:

(a) a mixture of iron (Fe), chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti) and zirconium metal powder comprising a (Zr) and yttria (Y ₂ O ₃₎ powder Followed by mechanical alloying treatment to produce an alloy powder;

 (b) charging the canned alloy with the mechanically alloyed alloy powder to perform a degassing treatment;

(c) hot-working the degassed alloy powder to produce an oxide-dispersed enhanced alloy;

(d) cold-working the hot-worked oxide-dispersed reinforcing alloy.

In one embodiment of the present invention, in the step (a), the alloy powder comprises 12 to 20% by weight of chromium (Cr), 0.1 to 0.5% by weight of yttria (Y ₂ O ₃ ) (Ti) and zirconium (Zr) in an amount of 0.5 to 2 wt%, molybdenum (Mo) 0.5 to 2 wt%, titanium (Ti) 0.1 to 0.3 wt%, zirconium (Zr) Zr) is 0.5% by weight or less.

In another embodiment of the present invention, in the step (c), the hot working is performed through any one selected from the group consisting of hot isostatic pressing, hot forging, hot rolling and hot extrusion, or a combination thereof .

According to another embodiment of the present invention, in the step (d), the cold working is performed through any one selected from the group consisting of cold rolling, cold drawing, and cold peeling, or a combination thereof.

The ferritic oxide-dispersed strengthening alloy according to the present invention comprises 12 to 20% by weight of chromium (Cr), 0.1 to 0.5% by weight of yttria (Y ₂ O ₃ ), 0.1 to 4% by weight of tungsten (W) (Ti) and zirconium (Zr) in an amount of 0.5% by weight or less, and the balance being iron (Fe), wherein the sum of titanium (Ti) and zirconium (Zr) (Rotors, shafts, etc.) and aircraft engine parts (disks, nozzles, etc.) due to its excellent tensile properties at room temperature and high temperature, It is expected to be useful as a material for core structural parts (nuclear fuel cladding, duct, wire, seal stopper, etc.) of nuclear power system such as cooling high speed furnace.

1 is a diagram showing the results of a tensile test of a conventional oxide-dispersed reinforcing alloy and a ferrite-based oxide-dispersed reinforcing alloy according to the present invention at room temperature and 700 ° C.
2 is a graph showing the creep test results of a conventional ferrite-based oxide-dispersed reinforcing alloy and a ferrite-based oxide-dispersed reinforcing alloy according to the present invention at 700 ° C.

The present inventors have studied to improve tensile properties at room temperature and 700 ° C of an oxide dispersion strengthened alloy used for steam generators for thermal power generation, engine parts for aircraft, and structural parts of high-speed furnaces. As a result, they have found that molybdenum (Ti) and zirconium (Zr) are added as the element and the addition of the trace alloy element of titanium (Ti) and zirconium (Zr), the strength at room temperature and high temperature is improved as compared with the conventional oxide-dispersed strengthened alloy, .

Hereinafter, the present invention will be described in detail.

The present invention chromium (Cr) 12 ~ 20% by weight of yttria _{(Y 2 O 3) 0.1 ~} 0.5 wt%, tungsten (W) 0.1 ~ 4 weight%, molybdenum (Mo) 0.5 ~ 2 weight%, titanium (Ti (Ti) and zirconium (Zr) in an amount of 0.1 to 0.3% by weight, zirconium (Zr) in an amount of 0.02 to 0.3% by weight and the balance of iron A ferritic oxide-dispersed strengthened alloy is provided.

When the content of chromium (Cr) is less than 12% by weight, the oxidation resistance is deteriorated. When it exceeds 20% by weight, the workability is deteriorated. The content of chromium (Cr) %, More preferably from 14 to 18% by weight.

When the content of yttria (Y ₂ O ₃ ) is less than 0.1% by weight, the dispersion strengthening effect is insignificant. When the content is more than 0.5% by weight, the effect of strengthening dispersion due to the residual dispersion particles is increased, , Yttria (Y ₂ O ₃ ) is preferably from 0.1 to 0.5% by weight, more preferably from 0.3 to 0.4% by weight.

Tungsten (W) is a solid solution strengthening element added for high temperature strength characteristics, and the content of tungsten (W) is preferably 0.1 to 4 wt%, more preferably 1 to 2 wt%.

Molybdenum (Mo) is also a solid solution strengthening element added for high temperature strength characteristics. When the content of molybdenum (Mo) is less than 0.5% by weight, the effect of improving high temperature strength is insignificant. (Mo) is contained in a large amount, which is disadvantageous from the economical point of view. The content of molybdenum (Mo) is preferably 0.5 to 2% by weight, more preferably 1 to 2% by weight.

The content of titanium (Ti) is preferably 0.1 to 0.3% by weight, more preferably 0.2 to 0.3% by weight. Such titanium (Ti) is combined with yttria (Y ₂ O ₃ ) during heating to form a Y-Ti-O composite oxide such as Y ₂ Ti ₂ O ₇ or Y ₂ TiO ₅ , The strength can be improved.

In addition, the ferrite-based oxide-dispersed reinforcing alloy according to the present invention may further contain zirconium (Zr) as a trace alloy element, more specifically, the content of zirconium (Zr) is preferably 0.02 to 0.3 wt% Is 0.02 to 0.25% by weight. The zirconium (Zr) also bonds with yttria (Y ₂ O ₃ ) to form a Y-Zr-O composite oxide, which is homogeneously dispersed at a high density in the matrix, thereby further improving the strength characteristics.

As another aspect of the present invention, the present invention provides a method for producing a ferritic oxide-dispersed strengthened alloy having improved room temperature and high temperature strength, comprising the steps of:

(a) a mixture of iron (Fe), chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti) and zirconium metal powder comprising a (Zr) and yttria (Y ₂ O ₃₎ powder Followed by mechanical alloying treatment to produce an alloy powder;

 (b) charging the canned alloy with the mechanically alloyed alloy powder to perform a degassing treatment;

(c) hot-working the degassed alloy powder to produce an oxide-dispersed enhanced alloy;

(d) cold-working the hot-worked oxide-dispersed reinforcing alloy.

Step (a), iron (Fe), chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti) and zirconium metal powder comprising a (Zr) and yttria (Y ₂ O ₃₎ powder Are mixed and mechanically alloyed to prepare an alloy powder. At this time, the alloy powder contains 12 to 20 wt% of chromium (Cr), 0.1 to 4 wt% of tungsten (W), 0.5 to 2 wt% of molybdenum (Mo), 0.1 to 0.3 wt% of titanium (Ti) 0.3% by weight and the balance of iron (Fe), and the sum of titanium (Ti) and zirconium (Zr) is preferably 0.5% by weight or less. The powder of the metal powder and 0.1 to 0.5 wt% of yttria (Y ₂ O ₃ ) powder is mechanically alloyed using a mechanical alloying equipment such as a horizontal ball mill to produce an alloy powder.

In step (b), the alloy powder prepared in step (a) is degassed in a vacuum, and more specifically, the alloyed alloy powder produced by step (a) is impregnated in a can of carbon steel or stainless steel After filling the container, it is sealed and degassed at 400 to 650 ° C and 10 ^-4 torr for 1 to 4 hours.

In step (c), the degassed alloy powder is subjected to hot working by the step (b), and more specifically, any one selected from the group consisting of hot isostatic pressing, hot forging, hot rolling and hot extrusion And an oxide dispersion strengthened alloy is produced through a combination thereof.

In step (d), the oxide-dispersed reinforced alloy produced by step (c) is subjected to cold working, more specifically, through any one or a combination thereof selected from the group consisting of cold rolling, cold drawing and cold peeling .

In one embodiment of the invention, chromium (Cr) 12 ~ 20% by weight of yttria _{(Y 2 O 3) 0.1 ~} 0.5 wt%, tungsten (W) 0.1 ~ 4 weight%, molybdenum (Mo) 0.5 ~ 2 wt. 0.1 to 0.3% by weight of titanium (Ti), 0.02 to 0.3% by weight of zirconium (Zr) and the balance of iron (Fe) (see Example 1) Temperature strength and creep characteristics of the ferrite-based oxide-dispersed strengthened alloy according to the present invention showed that the ferrite-based oxide-dispersed strengthened alloy according to the present invention had better tensile properties at room temperature and 700 ° C than the conventional ferrite- (See Example 3), as well as creep properties.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the following examples.

[Example]

Example 1 Preparation of ferritic-based oxide-dispersed reinforcing alloy

A ferrite-based oxide dispersion strengthening alloy having the composition shown in Table 1 below was prepared.

Fe Cr W Mo Ti Zr Y ₂ O ₃ Reference alloys 1 Honey. 15 2 0.25 0.35 Reference Alloy 2 Honey. 15.5 One 1.8 0.25 0.35 New alloys 1 Honey. 15.5 One 1.8 0.1 0.2 0.35 New alloys 2 Honey. 15.5 2 One 0.1 0.2 0.35 New alloy 3 Honey. 14 0.2 One 0.1 0.25 0.35

(Unit: wt%)

(Fe, W , Cr, Mo, Ti, Zr, particle size of 200mesh or less, purity of 99% or more) and Y ₂ O ₃ Powder (50 nm or less, purity 99.9%) was mixed according to each weight ratio, alloy powder was produced by mechanical alloying in an atmosphere of high purity argon (Ar) at 240 rpm for 48 hours using a horizontal ball mill, And then degassed for 3 hours at a degree of vacuum of 500 DEG C and 10 < ^-4 > torr or less. The prepared alloy-filled cans were pressurized and heated by hot isostatic pressing (HIP) for 3 hours under the conditions of 1150 DEG C and 100 MPa to prepare an oxide dispersion strengthened alloy, and then heated at 1150 DEG C for 1 hour, To prepare an oxide dispersion strengthened alloy.

Example 2. Comparative experiment of strength characteristics at normal temperature and high temperature

YS (yield strength), ultimate tensile strength (UTS) and total elongation (TE) of the five types of ferrite based dispersion strengthened alloys prepared in Example 1 were measured at room temperature and 700 ° C, .

As shown in Fig. 1, the yield strength of the reference alloy 1 containing no zirconium (Zr) and molybdenum (Mo) was 729 MPa at room temperature and 181 MPa at 700 캜. The yield strength of reference alloy 2 containing no zirconium (Zr) was 773 MPa at room temperature and 193 MPa at 700 ° C. On the other hand, in the case of the new alloys 1, 2 and 3 of the present invention in which molybdenum (Mo) was added as a solid solution strengthening element and a trace alloy element of titanium (Ti) and zirconium (Zr) was added, the yield strength was 798 ~ 850 MPa and 239 ~ 272 MPa at 700 ℃.

From the above results, it was confirmed that the ferrite-based oxide-dispersed reinforcing alloy according to the present invention exhibits improved yield strength at room temperature and 700 ° C without lowering the elongation rate as compared with the conventional reference alloy.

Example  3. Comparison of creep characteristics at high temperature

The creep tests were performed at 700 ° C on the five types of ferrite-based oxide-dispersed strengthened alloys prepared in Example 1, and the results are shown in FIG.

As shown in Fig. 2, it was confirmed that the creep rupture time of the alloys of the present invention (new alloys 1 to 3) was significantly increased in comparison with Reference Alloy 1 and Reference Alloy 2 under stress of 120 and 150 MPa.

From the above results, it can be seen that the ferrite-based oxide-dispersed reinforcing alloy according to the present invention is superior to the conventional ferrite-based oxide-dispersed reinforcing alloy at high temperature creep characteristics.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (7)

(Cr), 0.1 to 0.5 wt% of yttria (W ₂ O ₃ ), 0.1 to 4 wt% of tungsten (W), 0.5 to 2 wt% of molybdenum (Mo) 0.3% by weight, zirconium (Zr) in an amount of 0.02 to 0.3% by weight, and the balance of iron (Fe).
The ferritic oxide-dispersed reinforced alloy according to claim 1, wherein the sum of titanium (Ti) and zirconium (Zr) is 0.5% by weight or less.
The ferritic oxide-dispersed reinforcing alloy according to claim 1, wherein the ferrite-based oxide-dispersed reinforcing alloy is used as a structural component material including a rotor, a shaft, an engine disk, a nozzle, and a fuel cladding for a high-speed furnace of a super critical pressure steam generator for thermal power generation Wherein the ferrite-based oxide dispersion strengthening alloy is characterized by:
A ferritic oxide-dispersed strengthened alloy having improved normal temperature and high temperature strength comprising the steps of:
(a) a mixture of iron (Fe), chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti) and zirconium metal powder comprising a (Zr) and yttria (Y ₂ O ₃₎ powder Followed by mechanical alloying treatment to produce an alloy powder;
(b) charging the canned alloy with the mechanically alloyed alloy powder to perform a degassing treatment;
(c) hot-working the degassed alloy powder to produce an oxide-dispersed enhanced alloy;
(d) cold-working the hot-worked oxide-dispersed reinforcing alloy.
The method of claim 4, wherein the alloy powder comprises 12 to 20% by weight of chromium (Cr), 0.1 to 0.5% by weight of yttria (Y ₂ O ₃ ), 0.1 to 4% by weight of tungsten (W) (Ti) and zirconium (Zr) in an amount of 0.5 to 2 wt%, molybdenum (Mo), 0.1 to 0.3 wt% of titanium (Ti), 0.02 to 0.3 wt% of zirconium (Zr) Is not more than 0.5% by weight.
5. The method according to claim 4, wherein in the step (c), the hot working is performed through any one selected from the group consisting of hot isostatic pressing, hot forging, hot rolling and hot extrusion, or a combination thereof Gt;
5. The method according to claim 4, wherein in the step (d), the cold working is performed through any one selected from the group consisting of cold rolling, cold drawing and cold peeling, or a combination thereof.

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