JPS62992B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to sliding structures, particularly for use in nuclear reactor core control rods such as pins and rollers for fuel control rods that require excellent corrosion resistance and wear resistance. Regarding sliding structures. [Prior Art] Fig. 1 shows an example of a nuclear reactor fuel control rod. In the figure, 1 is a handle of a fuel control rod, 2 is a guide roller consisting of a pin and a roller, which is the object of the present invention, 3 is a stainless steel pipe containing a neutron absorbing material,
4 is a blade that encloses the stainless steel tube 3. As shown in FIG. 2, the guide roller 2 includes a roller 5 made of a cobalt (Co)-based superalloy and a cobalt (Co)-based superalloy.
It consists of a pin 6 made of forged material. [Problems to be Solved by the Invention] The Co-based alloy used in this roller contains high carbon (C1.0%) and high chromium (Cr28%). Therefore, it contains many carbides, and therefore has high hardness, and because of its high chromium content, it has excellent corrosion resistance to high-temperature, high-pressure pure water, and has excellent properties as a roller material. On the other hand, it is used for pin material.
Co-based forged alloys require forgeability, workability, and weldability, so although the C content is 0.1% low and the Cr content is low at 20%, it still has excellent wear resistance and corrosion resistance. However, these alloys have approximately 65%
Since the pin material contains about 50% Co, abrasion powder is generated by the wear of both during use, which is activated and circulates within the system, and is also eluted by corrosion caused by high-temperature and high-pressure pure water. This poses a problem in that the Co that has been removed is contaminated with radioactivity and circulates. An object of the present invention is to provide a sliding structure that has good wear resistance and corrosion resistance and does not cause problems due to Co-induced radioactivity. [Means for solving the problem] In order to achieve the above objective, the materials of the sliding side member and the fixed side member must not contain Co, have excellent wear resistance, and have corrosion resistance against high temperature and high pressure pure water. In addition, the pin material can be forged.
Since it is fixed to the blade by welding, it is also required to have excellent weldability. To obtain wear resistance, the alloy is required to have a certain hardness. The hardness of the alloy is obtained by (a) precipitation hardening due to precipitates and (b) solid solution hardening of the matrix. In the method (a), methods using carbides and intermetallic compounds are typical, and in the method (b), it is necessary to contain a large amount of solid solution strengthening elements such as Mo and W, and furthermore, Work hardening by temporary processing etc. is effective. In addition, in terms of corrosion resistance against high temperature and high pressure water,
The amount of Cr, the amount of Ni, and furthermore the amount of Mo are the most important, and the amount of C is also important. From the above points,
It is necessary to select a suitable alloy that does not contain Co. From the above-mentioned viewpoints, the present inventors have developed (1) a nickel (Ni)-based material containing a large amount of titanium (Ti) and aluminum (Al), and a large amount of Cr;
The so-called γ′ strong precipitation superalloy (Ni ₃ (Al, Ti)
(2) Ni-based hardening alloys with high C and even higher Cr by crystallization or precipitation of carbides; (3) Ni-based alloys with B-type intermetallic compounds precipitated; Alloys with high C crystallized; (4) Ni-Cr-Fe-based alloys containing a large amount of Mo and further cold-worked; (5) Fe-based alloys containing Ti and Al; An alloy with a sufficiently high Cr content was selected, and a sliding wear test was conducted in pure water using a combination of four types of alloys as roller materials and three types of alloys as pin materials. This was done because there are materials that are suitable for the roller material on the sliding side but unsuitable for the pin material on the stationary side, and the combination of the two is important in terms of wear characteristics. be. As a result, the Fe-based alloy (5) was used as the pin material.
An alloy containing Ti and Al and a sufficiently high Cr content, and (4) Ni-Cr-
It has been found that the combination of an Fe-based alloy containing a large amount of Mo and an alloy that has been subjected to cold working is the most excellent. Therefore, in order to achieve the above-mentioned object, the present invention provides C0.01~0.3%, Ni30~50%, Cr18~24%,
The sliding side member is made of an alloy consisting of Mo7~10%, W3% or less, and the balance Fe, which has been subjected to 5~40% cold working, and the weight is C0.01~0.3%, Ni20~30%, Cr15~
20%, Mo0.5~2%, Ti1~3%, Al 0.1~0.5
%, B0.2% or less, V1% or less, and the remainder is Fe. [Function] The reasons for limiting the components of the sliding side member (roller material) and fixed side member (pin material) are as follows. <Sliding side member> C: 0.01 to 0.3% C is an important element that combines with Cr to form carbide and improve strength. However, the amount of C is 0.3%
If it exceeds this value, the corrosion resistance of the matrix will be poor, and the workability will be poor, resulting in cracking during cold working and hot working. Moreover, since hardness may decrease if it is less than 0.01%, the amount of C is limited to a range of 0.01 to 0.3%. Ni: 30-50% Ni is an important component that forms an austenite structure and improves corrosion resistance. The higher the amount of Ni, the better the corrosion resistance. Particularly good corrosion resistance with Ni content of 30% or more. If it is less than 30%, the corrosion resistance effect will not be sufficient. On the other hand, if it exceeds 50%, hot workability decreases and material cost increases, so it is necessary to add it in a range of 30 to 50%. Cr: 18-24% Cr is an important additive element that improves strength, corrosion resistance, and oxidation resistance. If the Cr content is less than 18%, the effect will be small, and if it exceeds 24%, the bond with carbon will increase and become brittle, so the Cr content should be 18%.
Limited to a range of ~24%. Mo: 7-10% Mo strengthens the austenite base and
It is an element that forms carbides and improves tensile strength etc. If it is less than 7%, the effect is small, and 10%
If it exceeds this amount, the ductility decreases and cutting becomes difficult, so the amount of Mo was limited to a range of 7 to 10%. W: 3% or less W, like Mo, is an element that strengthens the austenite base and forms carbides to improve tensile strength and the like. However, if the amount of W exceeds 3%, the ductility decreases and cutting becomes difficult, so the upper limit is set at 3%. Working degree: 5-40% Even if cold working is performed to a degree exceeding 40%, the hardness does not increase in proportion to the working degree. Further, since hardening is not promoted with a working degree of less than 5%, the working degree was limited to a range of 5 to 40%. <Fixed side member> C: 0.01 to 0.3% C is an important element that combines with Cr to form carbide and improve strength. However, the amount of C is 0.3%
If it exceeds this value, the corrosion resistance of the matrix will be poor, and the workability will also be poor, causing cracks during cold working and hot working. If it is less than 0.01%, the hardness may decrease, so the amount of C was limited to a range of 0.01 to 0.3%. Ni: 20-30% Ni is an important component that forms an austenite structure and improves corrosion resistance. However, if it is less than 20, the effect is not sufficient. On the other hand, if it exceeds 30%,
Reduces hot workability. Furthermore, the amount of Ni was limited to a range of 20 to 30% because it would increase weld cracking. Cr: 15-20% Cr is an important additive element that improves strength, corrosion resistance, and oxidation resistance. If the Cr content is less than 15%, the effect will be small, and if it exceeds 20%, the bond with carbon will increase and become brittle, so the Cr content should be 15%.
Limited to ~20% range. Mo: 0.5-2% Mo strengthens the austenite base and
It is an element that forms carbides and improves tensile strength etc. If it is less than 0.5%, the effect is small, and 2%
The amount of Mo was limited to a range of 0.5 to 2% since ductility decreases and cutting becomes difficult when it exceeds this amount. Ti: 1-3% and Al: 0.1-0.5% Ti and Al are precipitation hardening elements that combine with Ni to form a γ' phase [Ni ₃ (Al, Ti)] which is an intermetallic compound. This γ' phase has good consistency with the austenite matrix and causes lattice strain, so it is effective in improving strength. In addition, Ti is an important element that acts as a deoxidizing agent and precipitates the γ' phase, which is effective in improving strength and ductility as mentioned above. If it exceeds the Ti content, the η phase, which reduces ductility, tends to precipitate, so the amount of Ti was limited to a range of 1 to 3%. On the other hand, Al is an element that combines with Ti and precipitates a metal compound γ' phase to improve strength, but if it is less than 0.1%, this effect is small, and if it exceeds 0.5%, it will actually reduce the strength. The amount of Al added alone was limited to a range of 0.1 to 0.5%. B: 0.2% or less B is an element that significantly strengthens grain boundaries and improves ductility, but when added in large amounts, it has a negative effect on forgeability and oxidation resistance, so the upper limit is set at 0.2%.
The following was made. V: 1% or less V is an element that generates precipitates such as VC. V.C.
Since it has age hardening properties, it is effective in improving tensile strength. However, when the amount of V increases, V
diffuses into metal protective coatings such as Cr ₂ O ₃ and lowers its melting point, thereby adversely affecting low oxidation properties. Therefore, the amount of V was set to 1% or less. In addition, the Ni-based γ' type (1), the carbide precipitation type (2), and the Ni ₃ B intermetallic compound precipitation alloy (3) had sufficient hardness and excellent corrosion resistance. However, the wear resistance was poor. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Table 1 shows the chemical components (% by weight) of the materials subjected to the sliding wear test. Table 2 shows the heat treatments applied to the materials and their hardness. No. 1 to 5 as roller materials
Four types of seed and pin materials, Nos. 6 to 9, were tested. A sliding wear test was conducted in pure water with the roller material placed on the sliding side and the pin material placed on the stationary side. The test conditions were at room temperature and 70°C under high temperature and atmospheric pressure, but no difference was observed between room temperature and 70°C. Sliding cycle 28
times/min, sliding distance 60mm/times, surface pressure 25Kg/ ^cm2 ,
The amount of wear was measured after 500, 2000, and 5000 times. The test results are shown in FIGS. 3 to 5. FIG. 3 shows the results of the combination of roller materials No. 1 and No. 2 and pin material No. 8. As shown in Table 1, No. 1 is a γ' precipitation hardening alloy based on Ni with a high Ti+Al content of 7.5%, and has a hardness of 500H. No. 8 is an Fe-based alloy, with Ti
+Al is 2.2%, lower than No. 1, Ni is also 26%, and hardness is low at 260H. In this combination, the amount of wear on No. 1 (roller material) is relatively small, but the amount of wear on the fixed side (pin material) of No. 8 is large. No. 2 is a Ni-based hardened alloy made of carbides with a high content of C and Cr, but the result of the combination with No. 8 is
The amount of wear is slightly greater than that of No. 1. In addition, No. 8
Although the wear of No. 1 is also large, it is no different from that of No. 1.

【table】

〔Effect of the invention〕

The sliding structure according to the present invention has an alloy composition of
Since it does not contain Co, there is no risk of induced Co radiation when used, for example, in rollers and pins installed in nuclear reactor core fuel control rods that are exposed to high-temperature, high-pressure pure water. It is excellent in both, and has advantages such as increased structural reliability.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of the reactor fuel control rod, Figure 2 is a diagram showing the configuration of its guide roller, and Figure 3 is a diagram showing the configuration of the reactor fuel control rod.
FIG. 4, FIG. 5, and FIG. 6 are diagrams showing the results of wear tests in Examples and Comparative Examples of the present invention, respectively. 5... Sliding side member (roller), 6... Fixed side member (pin).

Claims (1)

[Claims] 1 C0.01~0.3%, Ni30~50%, Cr18~ by weight
The sliding side member is made of an alloy consisting of 24% Mo, 7 to 10% W, 3% or less W, and the balance Fe, which is cold-worked to 5 to 40%, C0.01 to 0.3%, Ni 20 to 30% by weight,
Cr15~20%, Mo0.5~2%, Ti1~3%, Al0.1~
A sliding structure comprising a fixed side member consisting of 0.5% B, 0.2% or less, V1% or less, and the remainder Fe.