JPH01262081A - Joining method of zirconium-based materials and dissimilar materials - Google Patents

Abstract

PURPOSE:To directly join the both simply with high reliability by pressurizing the abutting part of a Zr material and dissimilar material by the specified pressure and giving the heat cycle that the Zr material shows a transformation superplasticity. CONSTITUTION:The Zr material 1 formed with a male type tapered part at the tip part and the dissimilar material 2 of a stainless steel, etc., are abutted under pressure conditions. Said abutting part is then heated by its electrification directly and a heat cycle is given in the necessary number of times at optimum upper and lower temp. widths as shown in the figure with the transformation temp. 862 deg.C of Zr as the boundary. The Zr material 1 thus causes a transformation super plasticity, so the load P of 0.1-0.8kg/mm<2> is applied on the Zr material 1 and dissimilar material 2 under this superplastic conditions to join the both by pressurizing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bonding method for directly bonding a zirconium-based material and a different material.

[Prior art] Equipment that handles highly concentrated nitric acid aqueous solutions, such as spent nuclear fuel reprocessing equipment, is made of stainless steel, 5US304L,
Austenitic stainless steels such as 5US310 are used, as well as materials such as titanium and zirconium.

However, Zr-based materials (pure zirconium and Zr alloys such as Zircaloy are collectively referred to as Zr-based materials).

) is extremely difficult to weld with general-purpose materials such as ordinary steel, stainless steel as mentioned above, or Ni-based alloys such as Inconel (trade name of Inco Corporation). This is because Zr easily forms intermetallic compounds with Fe, Ni, and Cr, and these intermetallic compounds are fragile.
This is because the bonding strength is significantly reduced. therefore,
TI between iron-based material or Ni-based alloy and Zr-based material
Traditional welding such as G welding cannot be used.

Therefore, in the past, for example, Japanese Patent Application Laid-Open No. 62-2202
As shown in Japanese Patent No. 92, a method has been adopted in which direct bonding of a Zr-based material and a dissimilar material is avoided, and an insert material such as tantalum is interposed between the two.

However, when an insert material is used, not only the number of joints increases, but also the quality and thickness of the insert material must be strictly controlled. Therefore, it is undeniable that the reliability of the joint strength decreases as the number of joints increases. In addition, it is desirable that the bonding strength between the insert and the Zr-based material and the dissimilar materials be at least equal to or greater than the base metal strength of the smaller strength of these members to be joined. The technology to ensure high reliability is not easy.

On the other hand, in recent joining technology, there is a technology that utilizes superplasticity, for example, in the literature entitled "Diffusion joining under superplastic state" (
It is known from Hiroshi Netsu et al., Interfacial Bonding Research Committee, Japan Welding Society, September 29, 1986). However, this document does not report anything about Zr-based materials.

[Problem to be solved by the invention] Therefore, in order to solve the problems of the prior art as described above and achieve direct bonding between a Zr-based material and a dissimilar material, the present inventors developed a superplastic method for a Zr-based material. As a result of repeated attempts at diffusion bonding under these conditions, we discovered that the bonding strength is greatly affected by the pressure applied during bonding. Furthermore, it has been confirmed that within a predetermined pressure range, malignant intermetallic compounds that should exist at the bonding interface are suppressed to an extremely thin layer.

Based on this knowledge, the present invention aims to provide a method for directly joining a Zr-based material and a different f'i material, which is reliable and simple. .

[Means for Solving the Problems] The method for joining a Zr-based material and a dissimilar material according to the present invention includes
After matching the r-based material and different materials, 0°1~0,8
Pressure is applied under the condition of kg / mm 2, and in that state, the abutting portion is resistance heated, for example, by direct energization, and the required number of heat cycles is performed to cause transformation superplasticity in the Zr-based material and join the two. It is something.

In the present invention, it is particularly suitable for the shape of the abutting part to form a wedge-shaped abutting part by forming a Zr-based material on the female tapered part and a different material on the female tapered part.

[Function] In the present invention, the transformation superplasticity phenomenon of Zr-based materials caused by pressurization and heat cycles during bonding is used to activate the bonding surface of Zr-based materials and to improve the adhesion with the mating material. This results in improved bonding between the two. Also, the reason why the intermetallic compound layer becomes thicker when the pressure is large, and becomes thinner when the pressure is small is not clear, but it is thought that it may be because a reaction involving the movement of atoms is promoted between the two. It will be done.

In addition, especially when the joint interface is wedge-shaped as mentioned above, the joint area increases, and the Zr material with the smaller coefficient of linear expansion is used as the female tapered part, and the larger dissimilar material is used as the female tapered part. Since it is formed in a tapered part, a shrink fit effect can be expected after joining, and it has sufficient joining strength as a joint.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIG. 1 is a block diagram of a dissimilar material joint obtained by the method of the present invention, in which (a) shows the case of a bar material, and FIG. 1 (b) shows the case of a pipe shaft. Furthermore, this embodiment shows an example of a wedge-shaped joint interface. In the figure, 1 is Zr
2 is a different material, in this example stainless steel (
SUS304L) is used. Reference numeral 3 denotes a female tapered portion formed at the tip of the Zr-based material 1. Reference numeral 4 denotes a female taper portion of the dissimilar material 2 that is butted against the female taper portion 3 of the Zr-based material 1.

The Zr-based material 1 and the dissimilar material 2 formed as described above are butted together in a wedge shape under various pressure conditions, and the abutted portion is directly heated by energization, and then the Zr-based material 1 and the dissimilar material 2 are heated at appropriate upper and lower temperatures after reaching the Zr transformation temperature of 862°C. Give the required number of heat cycles in the temperature range.

FIG. 2 shows an example of a heat cycle pattern. Peak temperature 1027°C, bottom temperature 677°C
The heating and cooling rate when passing the transformation temperature is 20℃/se.
It was set as e. In addition, the number of cycles is 3 to 20 times,
About 10 times seems to give the best results.

By applying such a heat cycle, the Zr-based grit material undergoes transformation superplasticity, so under this superplastic state, Zr
A load P is applied to the r-based material 1 and the dissimilar material 2 to join them together under pressure. Finally, it is machined to the desired dimensions.

Experimental example> (1) Composition and tensile strength of sample (Tables 1 and 2)
(See table) (2) Experimental conditions Pressure force 0, 1-1, 0 kg/
n++n 2 heat cycles 3 to 20 times heat pattern See Figure 2 Atmosphere ] 0-2 TOrr or less (3) Experimental results (See Table 3) Table 3 shows the wedge-shaped junction (WJ) in Figure 1 (a) This is a comparison between the case of 1 and the case of the flat junction (FJ) shown in FIG.

Table 3 Tensile strength (kg/mm2) Subscript 1 of Tatami, WJ, and FJ is pure Zr-3US304L
, the subscript 2 indicates each combination of Zr alloy-8US304L.

(4) Fracture position (see Table 4) Table 4 Fracture position Figure 4 is a graph showing the relationship between pressing force and fracture strength.
FIG. 5 is a graph showing the relationship between the intermediate layer thickness at the joint interface and the breaking strength. In FIGS. 4 and 5, A and B correspond to microscopic structure photographs (A) and (B) in FIG. 6, respectively. In addition, A is a pressurizing force of 0, 5 kg/
When mm2, B is the pressing force of 1゜Okg/mm2
This is from the time of.

As is clear from Tables 3 and 4 and FIGS. 4 and 5, the joints produced by the method of the present invention exhibit practically sufficient bonding strength and have little variation.

On the other hand, in the case of flat bonding, the range of bonding conditions that can stabilize the bonding strength and cause the base metal to break is narrowed, or if the pressurizing force is set to 0, 5 kg/lIl+n2 or its vicinity. It is possible to obtain a bond strength sufficient to withstand use.

In the present invention, in the case of wedge-shaped joining, the pressing force is 0.1 to 0,
The desired strength is shown at 8 kg/mm2. If we observe this in the microscopic structure photograph in Figure 5, the thickness of the intermetallic compound layer is less than 20 μm within the above range, but it becomes as thick as 90 μm when the pressing force is 1.0 kg/mm2. It becomes thicker, resulting in a decrease in bonding strength. In addition, in the case of a wedge-shaped joint, the linear expansion coefficient or the smaller of Zr
It can be seen that the SUS abrasive material with the larger coefficient of linear expansion was shrink-fitted to the system $4 material 1, contributing to an increase in bonding strength compared to flat bonding.

[Effects of the Invention] As described above, according to the present invention, it is possible to directly join a Zr-based material and a different material, and an insert hole is not required as in the conventional method. The bonding strength has no practical problems and is stable. Therefore, the present invention is extremely convenient and highly reliable as a method for joining Zr-based materials with dissimilar materials.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are block diagrams of a cumulative joint obtained by the method of the present invention, Figure 2 is a diagram showing an example of a heat cycle pattern, and Figure 3 is a flat joint joint used for comparison. Figure 4 is a graph showing the relationship between pressing force and breaking strength.
FIG. 5 is a graph showing the relationship between the thickness of the intermediate layer at the joint interface and the breaking strength, and FIG. 6 is a photograph of the microscopic structure of the joint interface of the present invention. 1.Zr-based material 2..Different material 3.Female taper part 4.Female taper part Agent Patent attorney Souzo Sasaki Amendment (method) November 1, 1937

Claims (1)

[Claims] A zirconium-based material and a dissimilar material are butted together, the abutted portion is pressurized under conditions of 0.1 to 0.8 kg/mm^2, and a heat cycle is applied to the zirconium-based material in which the zirconium-based material exhibits transformation superplasticity. A method for joining zirconium-based materials and dissimilar materials.