JPH0361553B2 - - Google Patents

Abstract

PURPOSE:To increase the surface quality of a product by extruding the compound billet forming its core part with a metallic material, its outer periphery a precious metal and its outer skin a copper alloy and sealed with degassing and by performing the cold work after exposing the precious metal layer on all the cold work and outer skin removal. CONSTITUTION:The skin cylinder formed with a precious metal is fitted to the outer peripheral face of the core member formed by a metallic material and the protecting cylinder formed by a copper alloy or carbon steel is fitted to the outer part thereof further. Both ends of the protecting cylinder is closed by an end member and the inner part is made in degassing state. The compound extrusion material that each layer is joined with diffusion is obtd. by subjecting the compound billet thus obtd. to a hot hydrostatic pressure extrusion. The precious metal layer is then exposed by removing the protection layer with its melting after subjecting the compound extrusion material to a cold work. Thereafter the surface is smoothed by performing a cold work. The product having excellent surface quality can thus be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a noble metal clad material that provides a smooth surface free from flaws on the noble metal surface exposed to the outside.

(Prior art) Precious metals have excellent corrosion resistance and decorative properties, so they are used in accessories such as eyeglass frames and watch bands.They also have excellent conductivity, so they are used as conductive materials for electronic components. .

The functions required for these applications are all required for the surface layer, and since precious metals are expensive and heavy, it is necessary to use precious metals only in the parts exposed to the outside (the outer skin layer), and to protect the internal parts. (The core part) is made of a noble metal composite material in which a lightweight material, a high-strength material, a conductive material, a magnetic material, or other metal material is arranged as a functional material depending on the purpose.
In this way, base metal composites have the active purpose of adding functions that the base metal does not have, in addition to simply reducing the amount of expensive base metal used.

The most common manufacturing method for this type of composite material is to form a precious metal coating on the outer surface of the core by plating, but the plating layer is porous and the core will corrode in a corrosive environment. There was a problem that it was easy to peel off.

Therefore, clad materials have been developed in which the noble metal outer layer and core are more firmly bonded, and the common bonding methods are diffusion bonding by heat treatment,
Explosion bonding and hot extrusion bonding are known.

The present inventor took these measures one step further and developed a hot isostatic pressure process that can promote interfacial bonding of composite materials under high temperature and pressure, and can maintain a uniform area ratio of the composite material in the length direction. We have developed a method for manufacturing precious metal clad materials. That is, in this method, a composite billet with precious metal arranged on the outer circumferential surface is hot isostatically extruded to obtain an extruded material with a noble metal outer skin layer formed on the outer circumferential surface of the core, and this is then subjected to drawing, rolling, etc. In this method, the desired noble metal clad material is obtained by reducing the area by cold working.

(Problems to be Solved by the Invention) Although it was possible to obtain a composite material with good interfacial bonding as a cladding material by the above method, the precious metal layer was removed during the processing process such as cold drawing after extraction. It is easy for flaws such as seizure flaws due to contact with tools and transfer flaws from damaged tools to adhere to the surface of the tool, and scratches are also likely to occur during handling.

These surface flaws cause a significant loss of commercial value, especially in applications where decorative properties are required.

Surface flaws can be removed by polishing, but there is a risk of exposing the core.
This cannot be an effective means, and prevention of scratches has become an important issue.

The present invention was made in view of such problems,
When obtaining a precious metal clad material in which a composite billet is hot isostatically pressed and then cold-worked to have a precious metal outer skin layer and a core of various metals diffusion bonded, it is necessary to avoid surface flaws on the precious metal outer skin. The purpose is to provide a fast manufacturing method.

(Means for Solving the Problems) Means characterized by the present invention for achieving the above-mentioned objects is to provide an outer cylinder made of a noble metal material on the circumferential surface of a core member made of a metal material. A protective tube made of copper alloy or carbon steel is interposed thereon, end members are provided at both ends of the protective tube, and the inside is degassed and sealed.The composite billet is then hot isostatically extruded and A composite in which a core made of a metal material, an outer skin layer made of the noble metal material, and a protective layer made of an inexpensive and easily workable material such as copper alloy or carbon steel are diffusion bonded. After obtaining the extruded material and reducing the area of the composite extruded material by cold working, the protective layer of the obtained composite material is dissolved and removed to expose the precious metal layer, and then the surface of the precious metal is smoothed. The point is that cold working is performed.

(Example) First, a composite billet applied to the present invention will be described with reference to FIG.

In the composite billet 1, a protective tube 4 is attached to the outer peripheral surface of a core member 2 by interposing an outer skin tube 3 formed of a precious metal material, and a tip member 5 and a rear end member 6 are attached to each end of the protective tube 4. is provided, and the inside of the protective cylinder 4 is degassed and sealed.

As the core member 2, an appropriate metal material is used so as to satisfy the additional function added to the function of the noble metal. For example, if weight reduction is desired, Ti or an alloy thereof having a high specific strength is suitable.

The outer shell cylinder 3 is composed of a central cylinder part 3a made of a precious metal and end cylinder parts 3b formed at both ends thereof, and the precious metal may be a gold alloy (12K, 18K, etc.), a silver alloy, a palladium alloy, etc. is used as appropriate. On the other hand, the end tube portion 3a is preferably made of copper or a copper alloy, and has a color tone different from that of the noble metal. The central cylindrical portion 3a and the end cylindrical portions 3b are joined by TIG welding or plasma welding, and the joining surfaces are smooth.

The positional relationship between the outer shell cylinder 3 and the core member 2 is as follows. That is, the entire length of the core member 2 is formed to be shorter than the length of the outer shell tube 3, and a convex portion 7 is formed at both ends, and the root portion of the convex portion 7 is arranged so as to be located between the end tube portions 3b. There is. By arranging them in this way, the yield of precious metals can be improved.

Moreover, a lining cylinder 8 is interposed between the core member 2 and the outer skin cylinder 3. This lining cylinder 8 is
It serves to prevent the precious metal material of the outer shell cylinder 3 and the core member 2 from generating harmful alloy compositions or metal compounds due to thermal effects, or to prevent the noble metal outer shell from breaking during bending or stretching. By fulfilling this role, the lining cylinder 8 makes it possible to make the expensive precious metal outer shell thinner.

The lining tube 8 is made of Ni alloy, silver alloy, palladium alloy, etc., but it is not necessarily required and may not be used in some cases.

A protection tube 4 is fitted onto the outer peripheral surface of the outer skin tube 3. The protective tube 4 is provided to prevent the precious metal layer from being scratched during cold working after hot water pressing of the composite billet 1, and must satisfy the following conditions.

First, the deformation resistance during hot working is similar to or higher than the average deformation resistance of precious metal clad materials.
It must also be ductile. With pure copper, which has ductility but low deformation resistance, the protective cylinder is squeezed at the die approach part during extrusion.
Pure copper is undesirable because it tends to accumulate in front of the die, causing clogging.

Second, although the portion forming the protective tube 4 is removed after cold working, it is required to easily identify the presence or absence of any residual deposits. If there are residual deposits, the precious metal will not be exposed to the outside, and the surface will change color, reducing the commercial value, so it is necessary to completely remove the residual deposits. Selection criteria for easy identification include having a different color tone from precious metals and having different physical properties.

Copper alloys and carbon steel can be cited as materials that satisfy these conditions. That is,
These materials have deformation resistance equal to or higher than the average hot working deformation resistance of precious metal clad materials,
and has ductility. In addition, the color tone of copper alloys can be easily changed depending on the alloy composition such as Ni or Sn, and can be easily distinguished from precious metals.
Since carbon steel has different electrical characteristics from precious metals, eddy current flaw detection can reliably detect the presence or absence of residual deposits. Note that, depending on the copper alloy, residual deposits may be detected by similar means.

A tip member 5 made of copper or copper alloy is provided at the tip of the protection tube 4, and a rear end member 6 made of copper, copper alloy, or steel is provided at the rear end. These end members 5 and 6 are in close contact with the convex portion 7 of the core member 2 and are attached to the peripheral edge of the tip of the protective tube 4.
Welded by TIG welding etc.

The front end member 5 and the rear end member 6 are formed with an engaging ring portion 9 so as to come into close contact with the convex portion 7 of the core member 2 . This engaging ring portion 9 allows a thick walled portion of inexpensive metal to be formed in the extruded material, and this portion can be extremely easily subjected to a broaching process for cold extraction.

The tip member 5 is provided with an exhaust pipe 10 for degassing the inside of the protection tube 4, and after degassing, it is sealed by pressure welding or TIG welding after pressure welding.

It goes without saying that the composite billet applied to the present invention is not limited to the one shown in Fig. 1, and the outer shell tube may be made only of precious metals as shown in Fig. 2, and the convex parts on both ends of the core member and It is not necessary to provide a lining tube.

Next, as shown in FIG. 3, the composite billet 1' is hot isostatically extruded to form a composite extruded material 11 in which the core 12 and the outer skin layer 13 and the outer skin layer 13 and the protective layer 14 are diffusion bonded. obtain. The core portion 12, the outer skin layer 13, and the protective layer 14 are obtained by extruding and deforming the core member 2, the outer skin cylinder 3, and the protective cylinder 4, which constitute the composite billet 1, respectively. Note that the composite billet 1' in the figure is the composite billet shown in FIG. 2. Further, in FIG. 3, 21 is a container, 22 is an extrusion die, 23 is a pressurizing system, and 24 is a pressurizing medium.

During hot isostatic extrusion, the composite billet is
It is heated to reduce deformation resistance and to form a diffusion bond, and is usually heated to 600 to 850°C. This is because if the temperature is lower than 600°C, there is a risk of poor bonding, and if the temperature exceeds 850°C, there is a possibility that inclusions such as intermetallic compounds will be generated due to reaction between the noble metal and the metal of the core member.

Further, the extrusion ratio varies depending on the extrusion temperature, but is set to 8 to 100 in the above temperature range.

The composite extruded material 11 is further subjected to cold working to reduce its area. Examples of cold working include cold drawing, cold rolling, etc., but during these workings, seizure flaws and transfer flaws from broken tools are likely to be formed on the workpiece. In the case of the present invention, these flaws are attached to the protective layer of the processed material, so they are not directly attached to the noble metal that is the outer skin layer.

A workpiece whose surface area has been reduced by local cold working has only its protective layer dissolved and removed, becoming a precious metal clad material with the outer skin of the precious metal exposed. As the dissolving and removing means, pickling is a simple method depending on the material of the protective layer.

Since the precious metal surface of the precious metal clad material is not smooth and lacks luster, cold working is performed to smooth the surface. This processing does not need to be processed more than necessary from the viewpoint of preventing the occurrence of defects. For example,
In the case of cold extraction elongation, based on operational experience, the area reduction rate is 8~
25% and the number of drawings is about 2 to 4 times, and the die is preferably one that does not easily get scratches, such as a diamond die.

Next, specific examples will be listed and explained.

Example 1 A Ni alloy (Co:3
%, Cr: 3%, remaining Ni), and a three-layer structure material with a pure Ti core member with an outer diameter of 63.5φ inserted inside the tube, and a copper alloy (Ni) with an outer diameter of 68.5φ and an inner diameter of 66.3φ. :
A composite billet was prepared by placing the billet in a protective tube containing 9% copper (Cu), and providing end members at both ends of the tube and sealing the inside to remove air.

This composite billet was heated to 650°C and hot-hydraulic extruded to a diameter of 10φ, and then cold drawn to reduce the diameter to 4.4φ. This drawn material was pickled with nitric acid to dissolve and remove the protective layer on the outer surface, and then drawn three times in a row using a carbide die to obtain a gold alloy clad titanium wire with a smooth surface and an outer diameter of 3.2φ.

Example 2 A Pd alloy (Ag: 3
%, Pd: 80%), and a three-layer structure material with an outer diameter of 63.5φ pure Ti inserted inside the tube.
A composite billet was prepared by placing the billet in a carbon steel (SS41) protection tube with a diameter of 68.5φ and an inner diameter of 66.3φ, providing end members at both ends, and degassing and sealing the inside.

This composite billet was heated to 800°C and hot-hydraulic extruded to a diameter of 10φ, and then cold drawn to reduce the diameter to 5.2φ. This drawn material was pickled with nitric acid to dissolve and remove the protective layer on the outer surface, and then drawn four times in a row using a carbide die to obtain a gold alloy clad titanium wire with a smooth surface and an outer diameter of 3.2φ.

Example 3 A two-layer structure material in which pure Ti with an outer diameter of 64.5φ was inserted inside an 18K gold alloy outer tube with an outer diameter of 66φ and a wall thickness of 0.6 mm was used as a copper alloy (Ni) with an outer diameter of 68.5φ and an inner diameter of 66.3φ. :9%, remainder
A composite billet was prepared by placing end members in a protective tube made of Cu), providing end members at both ends, and sealing the inside to remove air.

This composite billet was heated to 600°C, hot isostatically extruded to 15φ, and then cold drawn to reduce the diameter to 1.9φ. This drawn material was pickled with nitric acid to dissolve and remove the protective layer on the outer surface, and then drawn twice using a diamond die to obtain a gold alloy clad titanium wire with a smooth surface and an outer diameter of 1.5φ.

Example 4 Ag, Pd alloy (Ag: 20
%, Pd: 80%) inside the outer shell cylinder with an outer diameter of 64.5φ
Two-layer structure material with Ti inserted, outer diameter 68.5φ, inner diameter
A composite billet was prepared by placing the billet in a 66.3φ copper alloy (Ni: 9%, residual Cu) protective tube, providing end members at both ends, and degassing and sealing the inside.

This composite billet was heated to 850°C and hot-hydraulic extruded to 10φ, and then cold drawn to reduce the diameter to 3.4φ. This drawing material was pickled with hydrochloric acid to dissolve and remove the protective layer on the outer surface, and then drawn twice using a diamond die to obtain a gold alloy clad titanium wire with a smooth surface and an outer diameter of 2.3φ.

(Effects of the Invention) As explained above, according to the present invention, a noble metal outer skin surface is attached to the outer circumferential surface of the core member, and a copper alloy or carbon steel protective tube is further attached to the outer side of the outer skin surface to provide a gas-tight seal. Since the composite billet is hot isostatically extruded, a composite extruded material is obtained in which the core, the noble metal layer, and the protective layer are diffusion bonded, and the area ratio of each part is maintained along the extrusion direction. Since this composite extruded material has a protective layer formed on the outside of the precious metal layer, tool flaws and the like will not adhere to the precious metal even if a large area reduction process is performed by cold working. Thereafter, the protective layer is dissolved and removed, but since the protective layer is made of a specific material, the remaining portion of the protective layer can be easily determined and its complete removal can be easily performed. Then, the clad material from which the protective layer has been removed is only subjected to a slight cold working to smooth the exposed precious metal layer, so no new flaws will be attached, and the precious metal will have a smooth surface and good gloss. Clad wood is obtained.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing two examples of composite billets used to carry out the present invention, and FIG.
The figure is an explanatory cross-sectional view showing the state of hot isostatic pressure extrusion of a composite billet. 1, 1'... Composite billet, 2... Core member, 3
...Sheath tube, 4...Protection tube, 5...Tip member, 6
... Rear end member, 11 ... Composite extrusion material, 12 ...
core, 13...outer skin layer, 14...protective layer.

Claims (1)

[Claims] 1. A protective cylinder made of copper alloy or carbon steel is attached to the outer peripheral surface of a core member made of a metal material by interposing an outer skin cylinder made of a precious metal material, and the protective cylinder is made of a copper alloy or carbon steel. A composite billet with end members provided at both ends and whose interior is degassed and sealed is hot isostatically extruded to form a core formed of the metal material, an outer skin layer formed of the noble metal material, and the outer skin layer. A composite extruded material is obtained in which a protective layer formed of the copper alloy or carbon steel is diffusion bonded, and the area of the composite extruded material is reduced by cold working, and then the protective layer of the obtained composite processed material is melted. 1. A method for manufacturing a noble metal clad material, which comprises removing the noble metal layer to expose the noble metal layer, and then performing cold working to smooth the surface of the noble metal layer. 2 Cold working to smooth the surface of the precious metal layer
2. The method for producing a noble metal clad material according to claim 1, wherein the cold drawing is performed with an area reduction rate of 8 to 25% and a drawing number of 2 to 4 times.