JPH0794048B2 - Manufacturing method of inner surface silver clad aluminum tube - Google Patents

Description

The present invention relates to a method for manufacturing an aluminum tube having an inner surface clad with silver.

[Prior Art] For example, a copper tube has been conventionally used as an outer conductor of a semi-rigid coaxial cable. Also aluminum material is desired. However, even if the electric resistance of the aluminum material is pure aluminum, it is as low as about 60% of that of pure copper, which leads to deterioration of characteristics such as attenuation rate. In the outer conductor of the coaxial cable, the current flows on the order of several μm on the inner surface, and the outer portion has a strong reinforcing meaning.

Therefore, it is conceivable to use the inner surface silver clad aluminum tube from the viewpoint of both weight reduction and electrical characteristics.

[Problems to be Solved by the Invention] However, it is difficult to provide a thin clad layer on the inner surface of the aluminum tube, and it is the current situation that it cannot be realized by plating or other methods.

As a method of cladding, there are methods such as co-drawing, rolling and extrusion, but it is difficult to clad the inner surface of the pipe material.
Normal cladding has never been done.

In the case of cladding, it is desirable to clean the joint interface to increase friction and, on the contrary, to sufficiently lubricate the tool surface. In this respect, it has been said that hydrostatic extrusion is suitable for processing a clad composite material, because the tool surface is well lubricated. However, the success or failure of the cladding may be greatly affected by the composition of the cladding material as well as the lubrication of the tool surface, and even in the hydrostatic extrusion product, the thin layer cladding on the inner surface of the pipe material is not performed. .

There is also a method such as explosion welding as a cladding method, but it is not suitable for processing a long product and is economically expensive.

The present invention has been made based on the above, and an object of the present invention is to provide a method for producing an inner silver clad aluminum tube which is easy to form into a tube even when the inner silver clad layer is thin.

[Means for Solving Problems] The method for producing an inner surface silver clad aluminum tube according to the present invention is
A composite billet having a silver tube as an inner layer and an aluminum alloy tube having a deformation strength equal to or higher than that of silver as an outer layer is formed, and the composite billet is subjected to interfacial joining between the inner layer and the outer layer by a method such as hydrostatic extrusion or lubrication extrusion. However, this is characterized by forming a tube, which makes it possible to realize an aluminum tube in which a thin silver layer of 50 μm or less is clad on the inner surface.

[Examples of the Invention] Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples.

FIG. 1 shows an example of an inner surface silver clad aluminum tube manufactured according to the present invention. Reference numeral 1 is a silver layer as an inner layer, 2 is an aluminum layer as an outer layer, and the silver layer 1 and the aluminum layer 2 have a structure in which they are interface-bonded.

FIG. 2 shows a cross section of a composite billet as a starting material for manufacturing an inner surface silver clad aluminum tube. 21 is a silver tube as an inner layer, 22 is an aluminum tube as an outer layer, and 23 is a plug. The inner layer 21 is fitted inside the outer layer 22, and the plug 23 is attached to the rear end. Inner layer 21
It is important that the outer layer 22 and the plug 23 are sealed by a method such as silver brazing, soldering or tape winding so that the pressure medium during extrusion processing such as hydrostatic extrusion or lubrication extrusion does not flow into the joint interface. is there. Also, the inner layer 21
The bonding interface between the outer layer 22 and the outer layer 22 needs to be sufficiently cleaned.

FIG. 3 shows an example of a hydrostatic extrusion method in which pipe forming is performed while interfacial bonding between the inner layer 21 and the outer layer 22 of the composite billet. 31 is a composite billet, 32 is a stem, 33 is a pressure medium, 34 is a mandrel, 35 is a mandrel holder, 36 is a die, and 37 is a tube. The mandrel 34 is supported by the composite billet 31 via the mandrel holder 35, and is moved to the die 36 side as the composite billet 31 is extruded (moving mandrel system). According to this method, the pressure medium 33 can be reduced and stable extrusion processing can be performed.

Lubrication between the inner surface of the composite billet 31 and the mandrel 34 is important when manufacturing the inner clad tube, especially when an inner clad layer having a thickness of 50 μm or less is obtained. , Inner surface of composite billet 31 and mandrel 34
It is preferable that a gap be provided between them to apply a fluid pressure by the pressure medium 33 and to apply an extreme pressure lubricant (for example, MoS ₂ ) to the outer peripheral surface of the mandrel 34.

As an example, a composite billet using silver as the inner layer 21 and an aluminum alloy (2.5% Mg-Al) as the outer layer 22 was prepared. As a comparative example, the same silver as the example was used for the inner layer 21 and the outer layer 22 was pure. A composite billet using aluminum (99.5% Al) was created. The outer diameter of the composite billet was the same in both the examples and comparative examples.
It was set to 28 mmφ.

The deformation strengths (tensile strength [kgf / mm ² ]) of silver, aluminum alloy, and pure aluminum used to make the composite billet are as shown in Table 1, in the order of aluminum alloy>silver> pure aluminum. There is.

In the hydrostatic extrusion method shown in FIG. 3, the mandrel 34
MoS ₂ was applied to the surface of, and polyethylene was used as the pressure medium 33, and warm isostatic extrusion was performed at 350 ° C.

When the composite billet of the example is used, the inner surface has a thickness of 30
6mmφ (outer diameter) × 0.35mmt with silver clad layer of μm
The (thickness) tube could be manufactured soundly.

On the other hand, when the composite billet of the comparative example is used,
The thickness of the silver clad layer on the inner surface was changed in the longitudinal direction, breakage occurred at a portion where the layer thickness was thin, the aluminum material was exposed, and a uniform tube could not be obtained.

Fig. 4 shows another example of the hydrostatic extrusion method.
Is a composite billet, 42 is a stem, 43 is a pressure medium, 44 is a mandrel, 45 is a mandrel holder, 46 is a die, and 47 is a tube. The mandrel 44 has a structure fixed to the main body via a mandrel holder 45 (fixed mandrel method). This method can be used in the present invention, although the amount of the pressure medium is large relative to the volume of the billet and the extrusion behavior tends to be unstable, as compared with the moving mandrel method described above.

In the present invention, not only hydrostatic extrusion but also hydra
Similar effects can be expected in film extrusion and lubrication extrusion using a viscous lubricant.

FIG. 5 is a cross-sectional explanatory view of an embodiment of a coaxial cable using an inner surface silver clad aluminum tube manufactured according to the present invention, in which 51 is an inner conductor, 52 is an insulator, 53 is an outer conductor, and an outer conductor. Reference numeral 53 is an inner surface silver clad aluminum tube in which a silver layer 54 is clad on the inner surface of an aluminum layer 55.

Such a coaxial cable has the inner conductor 51 inside the outer conductor 53.
(Silver-plated steel wire) and insulator 52 (polytetrafluoroethylene) are inserted and sinking is performed.

Table 2 shows the evaluation results for coaxial cables.
For comparison, pure aluminum (99.99% A
l) and the evaluation results of examples using oxygen-free copper are also shown.

From Table 2, the amount of attenuation of the coaxial cable using the inner surface silver clad aluminum tube as the outer conductor is smaller than that of the case of using aluminum as the outer conductor, and the characteristic impedance is equivalent to that of the case of using copper as the outer conductor.

[Effect of the Invention] As described above, according to the present invention, even when the thickness of the inner surface silver clad layer is extremely thin, such as 50 μm or less,
It is possible to maintain stable dimensional accuracy and manufacture a stable inner surface silver clad aluminum tube. Further, by using this tube, it is possible to realize a semi-rigid type coaxial cable that is equivalent in weight to a coaxial cable using aluminum and equivalent in electrical characteristics to a coaxial cable using copper.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of an inner surface silver clad aluminum tube manufactured by the present invention, FIG. 2 is a vertical cross-sectional explanatory view of a composite billet used in the present invention, and FIG. 3 is a hydrostatic extrusion method. FIG. 4 is an explanatory view of another example of the hydrostatic extrusion method, and FIG. 5 is a cross-sectional explanatory view of a coaxial cable using an inner surface silver clad aluminum tube manufactured according to the present invention. . 1: Silver layer, 2: Aluminum layer 21: Silver tube, 22: Aluminum alloy tube 31: Composite billet, 32: Stem 33: Pressure medium, 34: Mandrel 35: Mandrel holder 36: Dice, 37: Tube 51: Inner conductor , 52: Insulator 53: Outer conductor, 54: Silver layer 55: Aluminum layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masahiro Kiyoto 3550, Kidayo-cho, Tsuchiura-shi, Ibaraki Hitachi Cable Ltd. Metal Research Laboratory (72) Ryosuke Kaizu 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Electric Wire Co., Ltd. (72) Inventor Hitoshi Kikuchi 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Hitachi Electric Cable Co., Ltd. Hidaka Plant

Claims (1)

[Claims] 1. A composite billet comprising a silver tube as an inner layer and an aluminum alloy tube having a deformation strength equal to or higher than that of silver as an outer layer. The composite billet is formed into an inner layer and an outer layer by a method such as hydrostatic extrusion or lubrication extrusion. A method for producing an inner surface silver clad aluminum tube, which comprises forming a tube while performing interfacial bonding of the tube.