JPH0255682A - Different material joint - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance and the joining strength of a junction part by executing a junction in a state that a shape of the junction part is inclined at the time of bringing different kinds of metallic members to solid phase joining. CONSTITUTION:At the time of joining a member 1 consisting of a Zr compound stock, etc., and a member 2 of a stainless steel stock, etc., a male die tapered part 3 is formed in the tip of the member 1, and a female die tapered part 4 is formed in a joining position of the member 2. Subsequently, the members 1, 2 are pressed under the prescribed pressure condition, and also, a junction part is electrically conducted directly and heating is executed. In this case, by setting a transformation temperature of the member 1 as a boundary, a heat cycle of suitable temperature width by prescribed heating and cooling is given. In such a way, thickness of an intermetallic compound layer generated between the joint surfaces is decreased remarkably. Also, the junction stock 1 causes transformation superplasticity, and a shrink fit effect also works on the joint interface, therefore, the corrosion resistance and the joining strength of the junction part of the members 1, 2 are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the shape of a joint of a dissimilar material joint by solid-phase joining.

[Conventional technology] Solid phase welding is a concept that includes pressure welding, ultrasonic welding, friction welding, explosion welding, diffusion welding, etc., but the conventional solid phase welding method cannot join dissimilar metal joints. It is customary to perform this on a plane perpendicular to the joining direction. For example, JP-A-62-
Publication No. 220292 relates to pipe joining technology used in piping systems that handle high-concentration nitric acid aqueous solutions, such as in spent nuclear fuel reprocessing equipment. Materials are joined vertically. One problem with such vertical bonding (hereinafter referred to as flat bonding) is that the intermetallic compound layer is relatively thick (usually 90 μm or more) at the bonding portion. In particular, when the negative material is a zirconium-based material (pure zirconium and Zr alloys such as Zircaloy are hereinafter collectively referred to as Zr-based materials), the metal formed between FeNi, Cr, etc. Since the intermediate compound is extremely brittle, the bonding strength decreases significantly as the layer thickness increases. Furthermore, during cooling, thermal stress acts as shear stress at the joint, weakening the joint strength. Therefore, in order to limit the formation of such a malignant intermetallic compound layer, the idea of interposing an insert material that acts as a bridge between the two bonding materials was reached, as shown in the above-mentioned publication.

However, when using insert materials, it is necessary to strictly control the quality and thickness of the insert materials, which not only complicates the process but also makes the technology to ensure high reliability of joint strength extremely difficult. Become.

[Problems to be solved by the invention] As mentioned above, in conventional dissimilar metal joints, the shape of the joint is perpendicular to the joining direction (the axial direction of the joined members), and the intermetallic compound layer is formed thick at the joint. There was a problem. This is due to the fact that since the vertical surfaces are butted against each other, the effect of removing intermetallic compounds is poor.

Therefore, the present invention has developed a joint shape that allows the intermetallic compound layer to be formed thinly at the joint, and a solid-phase joining method that achieves direct joining without the need for any inclusions such as insert materials. The purpose of this invention is to provide a joint made of dissimilar materials.

[Means for Solving the Problems] In the dissimilar metal joint according to the present invention, when a joint of dissimilar metal materials is made by a solid-phase joining method, the shape of the joint part is made oblique to the joining direction. The angle of the joining member with respect to the axis is preferably 45° or less, and is preferably selected to provide a shrink fit effect.

[Function] In the dissimilar material joint according to the present invention, since the tapered surfaces are pressed against each other during joining, a force acts to push out the intermetallic compound generated at the joint part to the outside along the slope thereof. Therefore, the intermetallic compound layer is relatively thin. In addition, a shrink fit effect can be expected as the bonding area increases. Furthermore, during cooling, thermal stress acts as compressive stress, which works to increase the bonding strength.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

First, a case of a dissimilar material joint made by a diffusion bonding method using transformed superplasticity will be explained. Figure 1 is a configuration diagram of the dissimilar material joint of this embodiment, and Figure 1 (a) shows the case of a bar material;
b) shows the case of pipe material. In the figure, 1.
Reference numeral 2 denotes a joining member, and in this embodiment, member 1 is made of Zr-based material, and member 2 is made of stainless steel material (SUS304L).

3 is the member with a smaller linear expansion coefficient, that is, Zr-based material 1
It is a female tapered part formed at the tip of , and the angle θ is 1
It is 5°. Reference numeral 4 denotes a female tapered portion of the dissimilar material 2 that is butted against the female tapered portion 3 of the Zr-based material 1. The coefficient of linear expansion of the different material 2 is much larger than that of the Zr-based material 1. Reference numeral 5 denotes a hollow portion formed deep inside the female tapered portion 4.

The Zr-based material 1 and the dissimilar material 2 formed as described above are butted together under various pressure conditions, and the abutted portion is directly energized to heat this part. Apply the required number of heat cycles at an appropriate temperature range.

FIG. 2 shows an example of a heat cycle pattern. The peak temperature is 1027℃, the bottom temperature is 677℃, and the heating and cooling rate when passing the transformation temperature is 20℃/see.
And so. In addition, the number of cycles is 3 to 20 times, and 1
Around 0 times seems to give the best results.

By applying such a heat cycle, the Zr-based material 1 undergoes transformation superplasticity, so that 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. A part of the Zr-based material 1 which has undergone transformation superplasticity is removed from the inner and outer ends 6°7 of the tapered surface and becomes solid and fixed, so that it is finally machined to a predetermined size.

After bonding, a shrink fit effect acts on the bonding interface, increasing the bonding strength. In addition, the fracture position in a joint tensile test depends on the strength of both base materials, the strength of the joint reaction layer, and the angle of the tapered part, so by selecting this angle, it is possible to determine whether the fracture position is at the joint or on the lower strength side. The base material changes.

Next, an experimental example will be shown. For reference, a comparison will be made with a conventional flat bonding case as shown in FIG.

Experimental example> (1) Composition and tensile strength of sample material (Table 1 and WS
(See Table 2) (2) Experimental conditions Pressure force 0, 1-1, 0 kg/
mm 2 Heat cycles 3 to 20 times Heat pattern See Figure 2 Atmosphere 10-2 Torr or less (3) Experimental results (See Tables 3 and 4) In addition, in Tables 3 and 4, TJ is as shown in Figure 1. (a) shows the case of the tapered joint, and FJ shows the case of the flat joint in FIG. 3. Also, T.J., F.J.
The subscript 1 indicates the combination of pure Zr-3US304L, and the subscript 2 indicates the combination of Zr alloy-5US304L.

Table 3 Thickness of intermetallic compound layer (μm) Table 4 Tensile strength (kg/mm) Table 6 shows the results of examining the corrosion resistance of the joint by an accelerated corrosion resistance test.

Test material TJ (pressure force 0.8 kg/1n2)F
J2 (pressure force 0.8 kg/mm) Table 6 (4) Fracture position (see Table 5) Table 5 Fracture position (5) Corrosion resistance test results (see Table 6) 1.0 g/liter of Cr6+ Note: In the table, O indicates no selective corrosion at the joint interface, Δ indicates selective corrosion at the joint interface, and X indicates severe selective corrosion at the joint interface.

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 (intermetallic compound layer) at the joint interface and the breaking strength. Figures 4 and 5
In the figure, A is when the pressurizing force is O15kg/ll11,
B is when the pressing force is - -Okg/++us2.

As is clear from the above experimental results, the thickness of the intermetallic compound layer in the joint according to the present invention is considerably thinner, approximately 1/2 or less than that of the conventional flat joint. In addition, the bonding strength is sufficient for practical use, and there is little variation. On the other hand, in the case of conventional flat bonding, the bonding strength is not stable and the range of bonding conditions in which fracture of the base material can be obtained is narrow.

Next, a case using the hot pressure welding method will be described. The shape of the dissimilar material joint is the same as that shown in FIG. 1(a), and 5US304L was used for member 1, and AA606B-76 was used for member 2.

(1) Experimental conditions Heating temperature: 300℃ Pressure: 0.5kg/stop2 (2) Experimental results Thickness of intermetallic compound layer: 3μm Tensile strength: 19kg/mm2 (base metal fracture) From these results, it is also possible to determine that the intermetallic compound layer It can be seen that the thickness is thinner than that of FJ in Table 3. In addition, there is no problem with the bonding strength as the aluminum base material breaks.

[Effects of the Invention] As described above, the dissimilar material joint according to the present invention has a thin intermetallic compound layer at the joint, has high joint strength and corrosion resistance, and can be provided at low cost because it is directly joined.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are configuration diagrams of a dissimilar material joint according to the present invention, Figure 2 is a diagram showing an example of a heat cycle pattern, and Figure 3 is a diagram showing an example of a heat cycle pattern.
The figure shows the configuration of a flat joint joint used for comparison, Figure 4 is a graph showing the relationship between pressing force and breaking strength, and Figure 5 is a graph showing the relationship between intermediate layer thickness at the joint interface and breaking strength. . 1.2...Joining member 3...Female taper part 4...Female taper part Agent Patent attorney Muneharu Sasaki

Claims (1)

[Claims] 1. A joint made of dissimilar metal materials produced by a solid-phase joining method, characterized in that the shape of the joint is oblique with respect to the joining direction.