JPS6233079A - Production for precious metal clad material - 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 (Industrial Field of Application) The present invention relates to a method for producing a noble metal cladding material that provides a smooth surface without any flaws on the surface of the noble metal layer exposed to the outside.

(Prior art) Since precious metals have excellent corrosion resistance and decorative properties, l12
It is used in accessories such as mirror frames and watch bands, and because it has excellent conductivity, it can also be used as a conductive material for electronic components.

The functions required for these applications are all required for the surface layer, and since precious metals are expensive and heavy, the parts exposed to the outside (outer skin 1'ii)
A noble metal composite material is used in which noble metals are used only in the core, and metal materials such as lightweight materials, high-strength materials, conductive materials, or magnetic materials are arranged as functional materials in the interior (core) depending on the purpose. In this way, in addition to the purpose of simply reducing the amount of expensive precious metals used, noble metal composites have the active purpose of adding functions that precious metals do not have.

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, cladding materials have been developed in which the noble metal outer skin layer and core are more firmly bonded, and common bonding methods include diffusion bonding by heat treatment, explosion bonding, and hot extrusion bonding. It is being

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 developed a manufacturing method for precious metal cladding 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, which 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) By the method described above, it was possible to obtain a composite material with good interfacial bonding as a cladding material, but during the processing process such as cold drawing after extrusion, the surface of the precious metal layer Scratches such as seizure scratches due to contact with tools and transfer scratches from damaged tools are likely to adhere.
In addition, it is easy to incur equivalent costs 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, etc., but this is not an effective method as there is a risk of exposing the core, and prevention of flaws is an important issue. .

The present invention was made in view of the above problems, and is a precious metal craft material in which a composite billet is hot isostatically extruded and then cold worked to bond a precious metal outer layer and a core of various metals to each other by diffusion bonding. It is an object of the present invention to provide a manufacturing method that does not cause surface flaws on the precious metal outer skin layer.

(Means for Solving the Problems) A characteristic feature of the present invention for achieving the object of the present invention is to interpose an outer cylinder made of a noble metal material on the outer peripheral surface of a core member made of a metal material. A protective tube made of copper alloy or carbon steel is attached to the protective tube, 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 to remove the metal material. A composite extruded material in which a core made of a metal, 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. The composite extruded material is reduced in area by cold working, the protective layer of the obtained composite processed material is dissolved and removed to expose the precious metal layer, and then cold processing is performed to smooth the surface of the vaginal precious metal layer. The point is that it involves machining.

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

In the composite billet) l, a protective tube 4 is attached to the outer peripheral surface of the 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. and
The inside of the protective tube 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, which has a high specific strength,
Otherwise, this alloy 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 noble metal is made of gold alloy (12K, 18, etc.), silver alloy, palladium alloy etc. are used as appropriate.

On the other hand, the end tube portion 3b is preferably made of copper or a copper alloy, and has a color tone different from that of the noble metal. Central cylinder part 3a and end cylinder part 3
b is joined by TIG welding or plasma welding, and the joining surface is 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.

Further, between the core member 2 and the outer skin cylinder 3, a lining cylinder 8 is provided.
is interposed. This lining cylinder 8 prevents the precious metal material of the outer skin cylinder 3 and the core member 2 from being affected by heat and generates harmful alloy compositions or intermetallic compounds, or prevents the precious metal outer skin from breaking during bending or stretching. play a role in avoiding By fulfilling this role, the lining cylinder 8 makes it possible to make the expensive precious metal outer shell thinner.

The lining cylinder 8 is made of Ni alloy, silver alloy, palladium alloy, etc., but is not necessarily required.
Sometimes it is not used.

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 noble metal layer from being scratched during cold working after hot isostatic extrusion of the composite billet 1, and must satisfy the following conditions.

First, it must have ductility that is comparable to or greater than the average deformation resistance during hot working of noble metal cladding materials. With pure copper, which has ductility but low deformation resistance, the protective tube is squeezed at the die approach portion during extrusion, and the pure copper tends to stay in front of the die, resulting in clogging, which is undesirable.

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 residual deposits are present, the noble metal layer will not be exposed to the outside, resulting in discoloration of the surface and lowering the commercial value, so it is necessary to completely remove the residual deposits. The selection criteria for easy identification are that the color tone is different from that of precious metals,
One example is that they have 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 a noble metal clad material, and have 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.
On the other hand, since carbon steel has different electrical characteristics from noble metals, the presence or absence of residual deposits can be reliably detected by eddy current flaw detection. still,
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
, 6 are in close contact with the convex portion 7 of the core member 2, and are welded to the peripheral edge of the tip of the protective tube 4 by TIG welding or the like.

An engaging ring portion 9 is formed on the front end member 5 and the rear end member 6 so as to bring them into close contact with the convex portion 7 of the core member 2. This engaging ring portion 9 allows a thick portion of inexpensive metal to be formed in the extruded material, and this portion can be provided with a cold drawing opening very easily.

The tip member 5 is provided with an exhaust pipe 10 for degassing the inside of the protection tube 4, and after the gas is introduced, 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. 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. Said core 12, outer skin] 1i13 and protection 1m!
Reference numeral 14 is obtained by extruding and deforming the core member 2, the outer shell cylinder 3, and the protective cylinder 4, which constitute the composite billet 1. Note that the composite billet 1'' in the figure is the composite billet shown in FIG. 2. In addition, in FIG. 3, 21 is a container, 22 is an extrusion die, 23 is a pressure stem, and 24 is an extrusion die.
is a pressurized medium.

During hot isostatic extrusion, the composite billet is heated to reduce deformation resistance and to diffusion bond.
The temperature is set at 600-850°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 layer that is the outer skin layer.

A workpiece whose area has been reduced by a predetermined cold working process has only its protective layer dissolved and removed, becoming a noble metal clad material with an exposed noble metal outer skin layer. As the dissolving and removing means,
Pickling is easy, 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 pressure generation. For example, in the case of cold drawing, operational experience shows that the area reduction rate is 8 to 25% and the number of drawings is 2 to 4 times. In addition, it is preferable that the die be a diamond die or the like that is hard to get scratched.

Next, specific examples will be listed and explained.

Example 1 Inside a gold alloy shell tube with an outer diameter of 66φ and a wall thickness of 0.5 mm (D N
A 3-layer structure material with an outer diameter of 68.5φ and a pure Ti core member with an outer diameter of 63.5φ inserted inside a tube lined with i-alloy (Co: 3%, Cr: 3%, remaining Ni). Inner diameter 66.
A composite billet was prepared by placing the billet in a 3φ copper alloy (Ni: 9%, residual Cu) protective tube, providing end members at both ends, and deaerating and sealing the inside.

This composite billet was heated to 650"c and hot isostatically extruded to 1oφ, and then cold drawn to reduce the diameter to 4.4φ. This drawn material was pickled with nitric acid to form a protective layer on the outer surface. After dissolving and removing, perform three consecutive stretchings using a carbide die,
A gold alloy clad titanium wire with a smooth surface and an outer diameter of 3.2φ was obtained.

Example 2 A Pd alloy (Ag: 20%, Pd: 80%) with an outer diameter of 64.8φ and a wall thickness of 0.5 t@ was placed inside a No. 18 gold alloy jacket tube with an outer diameter of 66φ and a wall thickness of 0.5 mm. ) is provided with a 3-layer structure material in which pure Ti with an outer diameter of 63.5φ is inserted inside the tube lined with carbon steel (S) with an outer diameter of 68.5φ and an inner diameter of 66.3φ.
A composite billet was produced by placing the billet in a protective tube of S41), providing end members at both ends, and sealing the inside to remove air.

This composite billet was heated to 800° C., hot isostatically extruded to lOφ, and then cold drawn to reduce the diameter to 5.2φ. After pickling this drawn material with sulfuric acid to dissolve and remove the protective layer on the outer surface, it was drawn four times in a row using a carbide die, and the outer diameter was 3.
．． A gold alloy talalide titanium wire with a diameter of 2 and a smooth surface was obtained.

Example 3 A 2Ff1 structural member with an outer diameter of 68.5φ and an inner diameter of 66.3φ was made by inserting pure Ti with an outer diameter of 64.5φ into the inside of a No. 18 gold alloy outer shell tube with an outer diameter of 66φ and a wall thickness Q of 5 mm. Copper alloy (Ni
: 9%, residual Cu), end members were provided at both ends, and the inside was degassed and sealed to produce a composite billet.

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

Example 4 Ag, Pd alloy (Ag:
20%, Pd: 80%) inside the outer shell cylinder with an outer diameter of 64
．． 2N structural material with 5φ pure Ti inserted into outer diameter 68.5φ
A composite billet was prepared by placing the billet in a copper alloy (Ni: 9%, remaining Cu) protective tube with an inner diameter of 66.3φ, providing end members at both ends, and deaerating and sealing the inside.

This composite billet was heated to 850° C., hot isostatically extruded to a diameter of 10 φ, and then reduced in diameter to 3.4 φ by cold drawing. After pickling this drawn material with hydrochloric acid to dissolve and remove the protective layer on the outer surface, it was drawn twice using a diamond die to obtain a gold alloy crund titanium wire with a smooth surface and an outer diameter of 2.3φ. Ta.

(Effects of the Invention) As explained above, according to the present invention, a noble metal outer shell tube is attached to the outer circumferential surface of the core member, and a copper alloy or carbon steel protection tube is further attached to the outer side of the outer shell tube for gas-tight sealing. Since the composite billet is hot isostatically extruded, a composite extruded material is obtained in which the core, the precious 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. The cladding material from which the protective layer has been removed is only subjected to a slight cold working process 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. A cladding material is obtained.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing two sides of a composite billet used to carry out the present invention, and FIG. 3 is a cross-sectional explanatory view showing the composite billet in a state of hot isostatic extrusion. 1.1°...Composite billet, 2...Core member, 3...
・Outer shell tube, 4...Protective tube, 5...Tip member, 6...
- Rear end member, 11... Composite extrusion material, 12... Core, 13... Outer skin layer, 14... Protective layer.

Claims (1)

[Scope of 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 of the cylinder to degas and seal the inside thereof is hot isostatically extruded to form a core made of the metal material, an outer skin layer made of the noble metal material, and the outer layer. Obtain a composite extruded material in which the skin layer and the protective layer formed of the copper alloy or carbon steel are diffusion bonded, and after reducing the area of the composite extruded material by cold working, the protective layer of the obtained composite processed material is A method for producing a noble metal clad material, which comprises exposing a noble metal layer by dissolving and removing it, and then cold working the noble metal layer to smooth its surface. 2. Claim 1, characterized in that the cold working for smoothing the surface of the noble metal layer is cold drawing with an area reduction rate of 8 to 25% and a drawing number of 2 to 4 times. The method for producing the described precious metal cladding material.