JPH0280182A - Method for joining particle dispersion alloy pipe - Google Patents

Abstract

PURPOSE:To obtain a joining part of a particle dispersion alloy excellent in high-temperature strength by interposing an intermediate layer containing a melting-point lowering element between an alloy pipe and a round bar and specifying the total of clearances with respect to the inside dia. of the alloy pipe. CONSTITUTION:The round bar 2 is inserted into the ferritic particle dispersion alloy pipe 1 and the intermediate layer 3 is interposed between the alloy pipe 1 and the round bar 2. When the clearances in the radial direction between the intermediate layer 3 and the inside of the alloy pipe 1, and between the intermediate layer 3 and the outside of the round bar 2 are denoted by C1 and C2 respectively, the total of the clearances (all clearances) is made to C1+C2. These are arranged so that the clearances C1+C2 are made to <=5% of the inside dia. of the alloy pipe and then, heated and maintained at the temperature between the melting point of the intermediate layer 3 and 1200 deg. and the inside of the alloy pipe 1 is joined to the outside of the round bar 2. By this method, the joining part of the particle dispersion alloy excellent in the high-temperature strength can be obtained.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for joining particle-dispersed alloy tubes.

In particular, the present invention relates to a method for joining particle-dispersed alloy tubes that achieves strong bonding without impairing the high-temperature strength, which is an advantage of particle-dispersed alloys.

(Prior Art) The strength of metal materials decreases at high temperatures. Various alloys are being researched to overcome this problem and improve high-temperature strength. As a result, materials with excellent high-temperature strength have been developed in certain types of austenitic stainless steels and ferritic high-alloy steels, and many have been put into practical use. However, as the industrial and technical fields become more sophisticated, there is an increasing demand for heat-resistant materials that can be used at higher temperatures and under more severe conditions.

In particular, high-temperature materials are expected to be used in aircraft engines, gas turbines, new nuclear reactors, etc., as higher design temperatures lead to improved energy efficiency.

Therefore, a particle-dispersed alloy, which aims to improve strength at high temperatures by dispersing fine particles in an alloy matrix, has emerged as a promising material. The particle-dispersed alloy proposed in Japanese Patent Publication No. 60-8296 is an example of this. The alloy proposed in this publication is obtained by uniformly dispersing an oxide such as intoria, It has considerably higher high temperature creep strength than SUS316).

(Problem M to be solved by the invention) Even if a particle-dispersed alloy with excellent high-temperature strength is used as a constituent material of a device, the characteristics of the material cannot be fully utilized if the strength of the joint is poor. Therefore, in the case of particle-dispersed alloys, welding and joining methods are particularly problematic.

Conventional welding methods (e.g. TIG welding) also apply to particle dispersed alloys.
can be applied. However, the weld heat affected zone (HA
It is inevitable that the high-temperature strength of the material (referred to as Z) will be lower than that of the base metal. Especially in the HAZ, in the area heated to just below the melting point by the welding thermal cycle, the high temperature strength of the material is uniformly dispersed in the base material during heating. Fine particles aggregate and become coarse. )IA
The decrease in high-temperature strength at Z is considered to be due to the agglomeration and coarsening of these fine particles. Therefore, in particle dispersed alloys, it is extremely difficult to obtain a joint with high temperature strength equivalent to that of the base metal by ordinary fusion welding.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for joining strong particle-dispersed alloy tubes without impairing the high-temperature strength of the ferritic particle-dispersed alloy.

(Means for Solving the Problems) The inventors of the present invention sought to achieve the above objectives (through repeated experiments and research, they came up with the following idea.

In order not to impair the high-temperature strength, which is a characteristic of particle-dispersed alloys, it is important not to heat the alloy to a temperature higher than the temperature at which the dispersed fine particles begin to agglomerate.

Therefore, it is desirable to use a method that heats and joins the materials in a non-molten state, without heating them above the melting point of the materials, as in normal fusion welding. If such a method of joining at a temperature lower than the melting point of the base material is defined as non-melting joining, then it is necessary to adopt a method of realizing this non-melting joining in a particle-dispersed alloy tube.

Therefore, the present inventors realized that a so-called liquid phase diffusion bonding method should be used. In this bonding method, a layer containing a melting point lowering element is placed at the bonding interface and heated to the melting temperature of the intermediate layer. In this way, only the intermediate layer is melted. As the melting point lowering element in the intermediate layer diffuses toward the base material, the melting point of the intermediate layer increases and solidifies. In this way, joining is completed.

Therefore, the present inventors continued their research to confirm the applicability of the liquid phase diffusion bonding method to ferritic particle-dispersed alloys and to clarify the conditions for application. In particular, the pressure on the bonding interface required for bonding (approximately 0.1 kgf/■-
2 or more), we developed a method of interposing an austenitic material to provide a thermal expansion difference and utilizing the resulting thermal stress, and completed the present invention.

Thus, the gist of the present invention is to insert a round rod or tube made of an austenitic material into a ferritic particle-dispersed alloy tube to reduce the melting point between the inner surface of the alloy tube and the outer surface of the round rod or tube. After arranging the intermediate layer containing the element so that the total gap between the intermediate layer and the inner surface of the tube and between the intermediate layer and the outer surface of the round bar or tube is 5% or less of the inner diameter of the alloy tube, the melting point of the intermediate layer is The above is a method for joining particle-dispersed alloy tubes, which is characterized in that the inner surface of the alloy tube and the outer surface of the round bar or tube are joined by heating and maintaining the tube at a temperature of 1200° C. or lower.

At this time, it is preferable to mechanically pressurize the outer surface of the tube to reduce the tube diameter before heat joining.

(Function) Before starting a detailed explanation of the present invention, first, the arrangement of the alloy tube, round bar, tube, and intermediate layer in the present invention will be explained (
.

FIG. 1 shows the principle of joining particle-dispersed alloy tubes according to the present invention, where fa) is a side sectional view of the joint before heat joining;
Mountain) is its cross-sectional view. A round rod or tube 2 is inserted into the ferritic particle-dispersed alloy tube 1, and an intermediate layer 3 is interposed between the alloy tube 1 and the round rod or tube 2. Let C1 and C2 be the gaps in the radial direction between the intermediate layer and the inner surface of the alloy tube l, and the outer surface of the round bar or tube 2, respectively, then the total gap (total clearance) is given by C++CZ. Furthermore, if the thickness of the intermediate layer 3 is t, then the gap in the radial direction between the inner surface of the alloy tube 1 and the outer surface of the round bar 2 is C, +C, + t.
, is.

Next, the reasons and effects of each limitation in the method of the present invention described above will be explained in order.

The 2-niostenite-based austenitic material has a so-called austenite phase-only structure consisting of a face-centered cubic structure at room temperature, and specifically includes austenitic stainless steel or Ni-based alloy. These austenitic materials have a larger coefficient of thermal expansion than the ferritic materials constituting the particle-dispersed alloy tube 1. For example, when comparing the linear expansion coefficients of austenitic 5US304 and ferritic 5US405, they are 1.7 Xl0-' and 1.
1 Xl0−', austenitic SO5
304 is about 1.5 times that of ferritic SO5405. The reason why the material of the round bar or tube 2 is limited to austenite is to utilize the thermal stress caused by the difference in thermal expansion between the two to apply pressure to the joining interface necessary for joining. Therefore, this round rod or tube 2 may be made of an austenitic particle-dispersed alloy.

Intermediate Layer 3 In order to perform the liquid phase diffusion bonding method, an intermediate layer 3 containing a melting point lowering element is required. As the melting point lowering element, an element with a high diffusion rate is preferable. Specifically, P, B, etc. can be mentioned. The amount of P and B added is about 1 to 5%, preferably 1 to 3%. The intermediate N3 can be arranged by wrapping a metal foil containing a melting point depressing element around a round bar and using it as an insert material, or by plating or plating the joining surface of the materials to be joined.
There is a method in which an intermediate layer is formed by coating P, B, etc. in advance by a method such as original deposition or ion implantation.

The thickness to of the intermediate layer 3 is 0.01 μm or more and 200 μm.
m or less is desirable. If the intermediate layer is thinner than this, it cannot contribute to the improvement of bonding properties, and if it is too thick, it will take a long time for the melting point lowering element to diffuse during heat bonding, which is not practical.

Clearance for 1 person The gap (clearance) C++Cz between the alloy tube 1, the intermediate layer 3, and the round bar or tube 2 before joining and heating is equal to 5 of the inner diameter of the alloy tube.
% or less, preferably 3% or less. The reason why the clearance is limited in this way is because if the clearance is too large, even if there is a difference in thermal expansion between the tube and the round bar, thermal stress will not occur and it will not be possible to secure the pressurizing force at the joint interface. be.

Further, the clearance may be as close to zero as possible for the arrangement of the intermediate layer, so the lower limit is not particularly limited.

The temperature should be higher than the melting point of the intermediate layer 3 and lower than 1200°C, but it is preferably about 900 to 1100°C since it varies depending on the amount of the melting point lowering element. This is because liquid phase diffusion bonding is impossible at a temperature lower than this range, whereas if the temperature is too high, the performance (high temperature strength) of the base material will be impaired.

In order to increase the thermal stress caused by the difference in thermal expansion during heating of the joint,
It is effective to reduce the clearance by mechanically pressurizing the outer surface of the pipe to reduce the pipe diameter before joining, and this is desirable for improving the joining strength.

If the degree of processing is too large, the tube may become flat or cracked, so the reduction rate of the outer diameter of the tube should be 5% or less.

(Example) Next, embodiments of the present invention will be described in detail.

Twisting Metal Body Structure First, an example of the structure of a tube joint made by the method of the present invention will be described.

FIG. 2 shows an example of manufacturing a joined body in which two particle-dispersed alloy tubes 1 are joined via an austenitic stainless steel round bar 2 shown in FIG. 3 according to the present invention. Diameter d, (m
J diameter d z by machining both ends of round bar 2 with
(mm), and as the intermediate layer 3, a metal ribbon containing 1.5% B as a melting point depressing element (19% Cr - 7.5% S
After winding the round bar 2 (remaining Ni) to a predetermined thickness, both ends of the round bar 2 are inserted into the alloy tube 1 and heated to obtain a joined body. In this case, the diameter d of the round bar 2! is selected according to the inner diameter of the alloy tube l, the ribbon thickness, and the set clearance value, and dl is d! +311
It was designated as II. Further, 11.12 of ta+ in FIG. 3 is, for example, Ni = 30+*m 1g = lQmm.

On the other hand, FIG. 4 shows an example of the construction of a joined body obtained by plugging the end of an alloy tube 1 with a round rod 2. The construction of the joint is the same as that shown in FIG. 2.

Joints (creep test pieces) shown in Figure 5 were produced under various conditions according to the method of the present invention and the comparative method, and their performances were compared. That is, the dimensions, materials, and heating bonding conditions of the tube, round bar, and intermediate layer were varied within and outside the scope of the present invention, and the high temperature bonding strength (creep rupture time) was compared.

Figure 5 shows the state after joining, and the joined body shown in the figure has a pair of round bars 2 with stepped parts machined at both ends of the alloy tube l in the same way as shown in Figure 4. It is obtained by doing.

Reference numeral 4 schematically indicates a bonding interface obtained by melting, diffusing, and solidifying the intermediate layer, and the dimensions in FIG. 5 are as follows.

Ax = 4On+m 7! a = 201+w's = 10mm 1. D 80+wm Note that a screw for creep rupture test is carved on the outer peripheral surface of the portion 14 of the round bar 2.

Test pieces were manufactured under various conditions both within and outside the scope of the present invention. Table 1 below shows the dimensions, materials, and heating temperatures of Examples A1 to A15 according to the present invention and Comparative Examples 81 to B6. This is a summary of the conditions and creep rupture time.

In table 1 IH: High frequency induction heating F: Charge heating to heat treatment furnace (Reduce J++ old pipe outer diameter by 3% High frequency induction heating after cold working V: High vacuum of 1O-3Torr Ar: 99.9% A "atmosphere" NB: Poor bonding It is.

The material of the alloy tube 1 in these examples Al-A15 and B1-82 is ferritic particle dispersed alloy 0DS1.
It is. The material of the round bar 2 is shown in Table 1.

Table 2 below shows the composition of these materials.

When using a thin ribbon insert as an intermediate layer, the thickness is 50μ or 300μ, and the width is 1.
A ribbon No. 01 was wound around the outer periphery of the round bar 2 in the same manner as in the case shown in FIG. 2, and placed inside the alloy tube 1.

In addition, as a method for forming the intermediate layer, in addition to the thin strip insert method, there are two methods for forming the intermediate layer: ■ After B is vapor-deposited on the outer periphery of the round bar in an area with a width of 10 #, Ne ions are ionized at an accelerating voltage of 30 kV and a beam current of 30 mA. Ion implantation method for implantation, (A13), ■ Electroplating in a nickel sulfate + phosphorous acid solution at a current density of 3 x 10'(A/da") on the radius 10- area on the outer periphery of the round bar. The P plating method (A12) was used to obtain a P-enriched layer.

The heating conditions are as shown in Table 1.

i.e., high vacuum (V) of 10-' Torr or 99.
After being held at a constant temperature of 1000 to 1300° C. for 5 minutes in a 9% Ar atmosphere (Ar), it was air cooled. Heating methods include direct induction heating of the tube (Ill) or heat treatment furnace method (Ill).
The test piece A14 designated as F) was subjected to cold working to reduce the outer diameter of the tube by 3% before heating.

The high temperature bonding strength was evaluated by a creep rupture test with a load stress of 15 kgf/ms.The rupture test was performed by applying a tensile load in the longitudinal direction of the tube using a screw carved on the outer periphery of a round bar. .

The results of this experiment are shown in Table 1. As can be seen, in joining examples ^1 to 15 according to the present invention, creep strength almost equivalent to that of the base material was obtained.

However, in Comparative Examples 81 to B6, as shown by the umbrella, ferritic stainless steel was used for the round rod inserted inside the alloy tube, no intermediate layer was used, the clearance was too large, and the joining temperature was low. Too big or too big. Therefore, in the comparative example, good bonding could not be obtained, and even if bonded, the creep strength was extremely low.

(Effects of the Invention) As described above, the method of the present invention utilizes a liquid phase diffusion bonding method by interposing an intermediate layer containing a melting point-depressing element between an alloy tube and a round bar or tube, and The material, dimensions, heating temperature, etc. are specified within the optimal range, and the difference in thermal expansion of the inserted round rod or tube is used for joining. Therefore, according to the present invention, a joint of a particle-dispersed alloy with excellent high-temperature strength (creep properties) can be obtained, and can be used for joining pipes when joint strength and airtightness are required. The present invention can also be used, for example, to join end plugs or two-piece joints of cladding tubes for nuclear fuel.

[Brief explanation of the drawing]

Fig. 1 shows the principle of the present invention, (al is a cross-sectional view of the tube joint part taken along the line A-A in Fig. 1(b), and the mountain is a cross-sectional view taken along the line B-BM in Fig. 1al). Top view; Figure 2 shows an example of the structure of the joint part of the present invention, (al is the same figure of the joint part (
A cross-sectional view along the A-A line of bl, the peak is B- of ta+ in the same figure.
B-line sectional view; FIG. 3 shows the round bar used for the joining in FIG. 2, (al is a front view, (bl is an end view; FIG. This is a diagram showing an example, where fa+ is a cross-sectional view of A-A!
B-line sectional view; and FIG. 5 schematically show the test pieces used in the joint strength experiments of the present invention example and the comparative example, +al is a partially broken view,
(b) is a cross-sectional view along B-BvA of the same figure (bl). 1: Particle-dispersed alloy tube 2: Round bar 3: Intermediate layer 4: Joint interface

Claims (2)

[Claims] (1) A round rod or tube made of an austenitic material is inserted into a ferritic particle-dispersed alloy tube, and an intermediate layer containing a melting point-depressing element is formed between the inner surface of the alloy tube and the outer surface of the round rod or tube. , After arranging the intermediate layer and the inner surface of the alloy tube and the intermediate layer and the outer surface of the round bar or tube so that the total gap is 5% or less of the inner diameter of the alloy tube, the temperature is 1200° C. at a temperature equal to or higher than the melting point of the intermediate layer. A method for joining particle-dispersed alloy tubes, which comprises heating and maintaining the tube at the following temperature to join the inner surface of the alloy tube and the outer surface of a round bar or tube. (2) The method for joining particle-dispersed alloy pipes according to claim 1, wherein the pipe diameter is reduced by mechanically pressurizing the outer surface of the pipe before heating and joining.