JPS61250156A - Manufacture of heat resistant member - Google Patents

Abstract

PURPOSE:To manufacture a heat resistant member capable of withstanding high temp. and pressure and having improved resistance to stress corrosion cracking by subjecting an Ni alloy material contg. specified amounts of Cr, Fe and Zr to soln. heat treatment at a proper temp. CONSTITUTION:An Ni alloy material contg. 10-20wt% Cr, 4-10wt% Fe and <=0.01wt% Zr or one or more among Mg, Ca and Y is subjected to soln. heat treatment at 1,000-1,100 deg.C. Since sulfide is precipitated in the grains by the addition of Zr or one or more among Mg, Ca and Y, the sulfide is uniformly dispersed to inhibit the segregation of S on the grain boundaries, and a heat resistant member usable well at high temp. and pressure without causing stress corrosion cracking is obtd. The soln. heat treatment is carried out for 10-60min per 1in. thickness of the material. A heat resistant material having much superior resistance to stress corrosion cracking can be obtd. by carrying out age hardening at 690-720 deg.C after the soln. heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of heat treating a nickel-based alloy to improve stress corrosion cracking resistance.

[Technical background of the invention and its problems] A nickel-based alloy containing 10 to 20% chromium and 4 to 10% iron by weight, which is made mainly of nickel with the addition of chromium and iron, has excellent heat resistance. Therefore, it is used in fields such as aircraft materials, and it is also being used as a material for structural parts of nuclear reactors.

Since the structural parts of a nuclear reactor are used under severe conditions of 1% temperature and high pressure, they are required to have excellent corrosion resistance that can withstand these conditions. Therefore, in order to use the above-mentioned nickel-based alloy containing chromium, iron, zirconium, etc. as a material for nuclear reactor structural parts, the inventors of the present application have conducted various research and experiments in terms of corrosion resistance. The present invention was completed by focusing on the fact that it is necessary to particularly improve stress corrosion cracking resistance in order to survive under these conditions.

[Purpose of the invention]

The present invention was made based on the research results mentioned above,
It is an object of the present invention to provide a method for manufacturing a heat-resistant member with improved stress corrosion cracking resistance that can withstand high temperature and high pressure conditions.

[Summary of the Invention] The present invention has Cr of 10 to 20% by weight, l:e of 4 to
10%, lr below 0.01%, Mg, Ca, Y
A material made of a nickel-based alloy containing 0.01% or less of at least one element selected from
This is a method for manufacturing a heat-resistant member, characterized by performing solution treatment at 100° C. once.

Moreover, after applying the solution treatment to this material, 690~
The purpose is to perform age hardening treatment at 120°C.

According to the present invention, 0.01% ZR is added to the nickel-based alloy.
By adding 0.01% or less of at least one element selected from Mg, Ca, and Y, the sulfide is precipitated within the crystal grains, and the sulfide is uniformly dispersed. By suppressing grain boundary segregation, it is possible to produce a heat-resistant member that can be used satisfactorily without stress corrosion cracking even under high temperature and high pressure conditions. In the manufacturing method of the present invention, a heat-resistant member having the best stress corrosion cracking resistance can be obtained by combining solution treatment and age hardening treatment on the material.

Generally, the steps for manufacturing a heat-resistant member made of a nickel-based alloy containing Cr, Fe, etc. are as follows.

That is, after forging and rolling a material made of an alloy with a predetermined composition obtained by melting, heat treatment, that is, solution treatment, is performed to remove processing strain and dissolve carbides generated during processing. After the material is cut into a predetermined shape, a heat treatment, that is, an age hardening treatment, is performed to add strength to the state obtained by the solution treatment. In the present invention, 1000 to 1
Processing is carried out in a temperature compensation range of 100°C. In this case, the processing time is on the order of 10 to 60 minutes, preferably 15 minutes per inch of material thickness. In addition, age hardening treatment is performed at a temperature of 690
~720°C, time 18-24 hours, preferably 70°C
This is done at around 5°C for about 20 hours.

The reason why stress corrosion cracking resistance is improved by subjecting a material made of a nickel-based alloy containing Cr and Fe to a solution treatment at a temperature of 1000 to 1100°C is considered to be as follows. That is, in the above temperature range, even if carbides exist at grain boundaries, they are discontinuous, and the Qr-deficient region is also discontinuous.

In addition, any one of zr, MO, Ca, Y
By containing 0.01% or less of a species or two or more species, sulfide is precipitated within the grains and the sulfide is uniformly dispersed.
It also suppresses grain boundary segregation and improves stress corrosion cracking resistance.

10 limited the heating temperature to 1000℃~1100℃
If the temperature is less than 00°C, solid solution may not be sufficient, and 11
This is because if the temperature exceeds 00°C, the crystal grain size becomes excessively coarse, which is not preferable.

Furthermore, the age hardening heat treatment is performed to uniformly precipitate fine gamma prime phases and provide sufficient strength to the nickel-based alloy.

The heating temperature was limited to 690°C to 120°C in 69
If the temperature is less than 0°C, the precipitation of the gamma prime phase will be delayed, making it impractical; if the temperature exceeds 720°C, the grain size of the precipitated gamma prime will become coarse, making it impossible to obtain sufficient strength. Due to the reason.

Therefore, heat-resistant members manufactured by the manufacturing method of the present invention by subjecting a nickel-based alloy containing chromium and iron to solution treatment at a temperature of 1000 to 1100°C and then subjecting it to age hardening treatment can withstand high temperature and high pressure conditions. Parts that are used and have excellent stress corrosion cracking resistance, e.g.
It is suitable for nuclear reactor structural parts used under conditions of ℃ and approximately 70 atmospheres.

[Examples of the invention] Example 1 N 172.15%, Cr 16.4%, F by dissolution
e6.6%, Z ro, 01%, G O, 04%, S
io, 10%, M no, 40%, Qo O, 006%
, AJ20.82%, Ti 2.5%, Nb and T
Inconel X-750 with a composition of a O, 97%
The alloy material is rolled to a thickness of 2.8n and a length of 110OB.
A sample consisting of a plate material with a width of 110 m was formed, and each sample was subjected to solution treatment under the conditions shown in the table, and each sample was further subjected to age hardening treatment under the conditions of 704°C x 20 hours. .

Then, tests were conducted on each sample under the following conditions to examine stress corrosion cracking resistance. That is, after polishing and degreasing the sample, it was fixed in the jig shown in Fig. 1 to give a strain of 1%, and the temperature was 290°C, 70 atm, and the amount of dissolved oxygen was 20 pp-.
50QW in a boiling water reactor (BWR) simulated environment.
After being immersed for ##, the sample was taken out and examined to see if there was any stress corrosion cracking on the surface of the sample. Note that the jig shown in figure W41 is a holder 1.21 with an arcuate surface! The sample 5 is sandwiched and fixed together with the graphite 3 and the spacer 4.

The results of the stress corrosion cracking test described above are shown in a diagram in FIG. In this diagram, the horizontal axis shows the solution treatment temperature of the sample, and the vertical axis shows the maximum stress corrosion cracking depth that occurred in the sample. Yoreha in this microcosm, 1000-1100
Ilv other than ℃! Sample A subjected to L1% solution treatment,
(Comparative example), many stress corrosion cracks occurred, but 100
Sample S subjected to solution treatment at a temperature of 0 to 1100°C,
C, O <Inventive Example) Stress corrosion cracking hardly occurred.

Therefore, it can be seen that the products manufactured by the manufacturing method of the present invention have very excellent stress WA corrosion resistance.

Example 2 By dissolving Ni72.15%, Cr16.4%, F
e6.6%, Mg and Qa O, 01%, CG, 0
4%, S to, 10%, MnO, 40%, Co
O, 008%, An O, 82%, TI 2.5%,
A stress corrosion cracking test similar to that in Example 1 was conducted on samples of Inconel show. The results are the same as in Example 1, and samples F and J (comparative examples) that were solution-treated at temperatures other than 1000-1100°C developed many stress corrosion cracks; Sample G1H%I (example of the present invention) subjected to the treatment showed almost no stress corrosion cracking. Therefore, it can be seen that the products manufactured according to the present invention have very excellent stress corrosion cracking resistance.

[Effects of the Invention] As explained above, according to the method for manufacturing a heat-resistant member according to the present invention, a heat-resistant member with excellent stress corrosion cracking resistance can be obtained, and the temperature range of solution treatment temperature is 1000 to 110.
It has the effect of widening the temperature to 0°C.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing a stress corrosion cracking resistance test device, and Figures 2 and 3 are diagrams comparing the relationship between solution treatment vA degree and stress corrosion cracking for the present invention and conventional example, respectively. It is. 1...Holder 2...Holder 3...Graphite 4/Axis...Spacer 5... ...Sample applicant: Toshiba Corporation Patent attorney Suyama Sa - 1st figure 2, 1, 2, Maruho Jc/L ('C) 3rd tooth

Claims (4)

[Claims] (1) In weight%, chromium 10-20%, iron 4-10%,
A method for manufacturing a heat-resistant member, comprising the step of subjecting a material made of a nickel-based alloy containing 0.01% or less of zirconium to solution treatment at a temperature of 1000°C to 1100°C. (2) Chromium 10-20%, iron 4-10%, M
A material made of a nickel-based alloy containing 0.01% or less of at least one element selected from g, Ca, and Y,
2. The method for manufacturing a heat-resistant member according to claim 1, further comprising the step of performing solution treatment at a temperature of 1000°C to 1100°C. (3) The method for manufacturing a heat-resistant member according to claim 1, wherein the solution treatment is performed for 10 minutes to 60 minutes per inch of material thickness. (4) After applying solution treatment to the material, 690°C to 72°C
The method for manufacturing a heat-resistant member according to claim 1, which comprises the step of performing age hardening treatment at a temperature of 0°C.