Method for manufacturing a bimetallic tube from jewelry alloys

Abstract

FIELD: jewellery industry.SUBSTANCE: invention relates to methods for producing a bimetallic tube from jewellery alloys. The method comprises the steps of obtaining and preparing two metal tubular shells made of jewellery alloys, wherein the diameters of the shells are selected in such a way as to ensure contact between the outer surface of the first shell and the inner surface of the second shell, connecting the two shells by inserting the first shell into the second while observing the condition of coaxial alignment of the axes of rotation of the first shell and the second shell, performing diffusion welding, wherein the welding modes are selected in such a way as to ensure the formation of a diffusion weld layer with a eutectic phase in the weld seam over the entire contact area of the welded surfaces of the shells.EFFECT: increasing the reliability of the connection of layers of a bimetallic pipe.5 cl, 3 dwg

Description

[0001] Technical field

[0002] The invention relates to the jewelry industry, in particular to methods for producing a bimetallic tube from jewelry alloys.

[0003] Technology Level

[0004] A bimetallic pipe is known that contains an inner pipe, an outer pipe installed coaxially to the inner pipe, and a layer of solder that connects the contacting surfaces of the outer and inner pipes (Russian Federation patent for invention No. 2537979, B23K 1 / 00, published 01 / 10 / 2015).

[0005] A bimetallic pipe is also known, comprising an inner pipe, an outer pipe installed coaxially with the inner pipe, and a polymer adhesive layer connecting the contact surfaces of the outer and inner pipes (Russian Federation Patent for Invention No. 2344266, B23K 20 / 16, published January 20, 2009). Disadvantages of known solutions include the complexity of manufacture, as well as the low strength characteristics of the resulting joints.

[0006] Also known is a bimetallic pipe comprising inner and outer tubular shells made of dissimilar metal alloys with different melting points, and a diffusion weld layer connecting the mating surfaces of the outer and inner tubular shells (Russian Federation Patent for Utility Model No. 163633, published July 27, 2016). A drawback of this solution is that it does not address the pipe manufacturing process itself. In particular, it does not address welding conditions or the conditions imposed on the shell geometry, which can lead to manufacturing defects and deterioration in the characteristics of the resulting pipes.

[0007] Also known in the prior art is a method for producing bimetallic wear-resistant pipes. This method involves centrifugally casting hollow bimetallic blanks with a wear-resistant inner layer comprising 50-60% of the total wall thickness and a ductile outer layer comprising 50-40% of the total wall thickness. The blanks are heated to a ductility temperature (1180-1200°C), and then rolled into bimetallic pipes on pipe rolling machines. However, this method is not applicable to jewelry production due to the high cost of jewelry alloys and the high material consumption during pipe production.

[0008] A method for producing bimetallic tubing is also known. This method involves cleaning the outer and inner surfaces of the tubing from deposits and contaminants, fabricating a thin-walled electric-welded pipe from carbon, low-alloy, or stainless steel, applying an adhesive sealant to its outer surface, inserting the thin-walled electric-welded pipe with the adhesive into the tubing bore, and then jointly deforming the tubing and the electric-welded pipe by expanding them. However, pipes produced by this method will have low reliability due to the weak adhesive bond.

[0009] Problem and technical result

[0010] The objective of the claimed invention is to develop a technological method for manufacturing a bimetallic tube from jewelry alloys, ensuring a strong connection of tubular parts made from different alloys of precious metals.

[0011] The technical result consists of increasing the strength of the connection between the tubular shells forming a bimetallic pipe. Furthermore, the proposed method reduces the material consumption of the bimetallic pipe manufacturing process and shortens the pipe production time.

[0012] Disclosure of the essence of the invention

[0013] The stated problem is solved, and the technical result is achieved by implementing a method comprising the following stages: obtaining and preparing two metal tubular shells made of jewelry alloys, wherein the diameters of the shells are selected in such a way as to ensure contact between the outer surface of the first shell and the inner surface of the second shell; combining the two shells by inserting the first shell into the second, observing the condition of coinciding the axes of rotation of the first shell and the second shell; performing diffusion welding, wherein the welding modes are selected in such a way as to ensure the formation of a eutectic alloy in the weld.

[0014] In one embodiment of the method, the inner ring is made of a jewelry alloy with a lower melting point than the alloy from which the outer ring is made.

[0015] In another embodiment of the method, the tubular shell made of a metal alloy with a lower melting point is made of a hypoeutectic silver alloy.

[0016] In another preferred embodiment of the method, the tubular shell of a metal alloy with a higher melting point is made of a gold-based alloy with a silver additive of at least 5% by weight.

[0017] In an alternative embodiment of the method, the tubular shell of a metal alloy with a higher melting point is made of a palladium alloy with a silver additive of at least 5% by weight.

[0018] Brief description of drawings

[0019] The essence of the invention is explained in Fig. 1-3.

[0020] In the drawings, the same elements are designated by the same reference numbers:

[0021] 1 - outer tubular shell;

[0022] 2 - inner tubular shell;

[0023] 3 - axis of rotation;

[0024] 4 - welded seam.

[0025] Figure 1 shows a flow chart of the method steps. Figure 2 shows the process of joining two shells. Figure 3 shows a variant of the finished bimetallic pipe in accordance with the preferred embodiments.

[0026] Implementation of the invention

[0027] To increase the strength and durability of jewelry, as well as reduce its cost while maintaining its appearance, pieces are often not made entirely of precious metal, but are simply coated with it on the outside. For example, various methods of gilding are widely known in the art.

[0028] However, such methods do not produce a sufficiently strong and thick layer of precious metal on the surface of the product. Over time, the gold plating wears off the surface of the product, for example, through wear, and the product loses its appearance. Therefore, the claimed invention proposes the use of bimetallic tubes made of jewelry alloys. These tubes can be produced industrially and provide the required thickness of the precious metal on the surface of the product. Prior art methods for producing bimetallic tubes are characterized by the complexity of their manufacturing process, as they require threading, and by the unreliability of the connection, as they involve the use of adhesives or solder.

[0029] The proposed method for producing a bimetallic tube from jewelry alloys is free from the above-mentioned disadvantages and ensures the production of a bimetallic tube with a strong connection of the outer and inner shells.

[0030] Let's take a closer look at the process of producing a bimetallic pipe from jewelry alloys.

[0031] Figure 1 shows a flow chart of the proposed method. The first step in the claimed method is the production of shells from jewelry alloys. Shells can be produced by any industrial method. However, the simplest and most common method is rolling. This involves taking a sheet of metal and bending it in a rolling machine to form a cylindrical tube.

[0032] Then the shells are prepared for subsequent diffusion welding. To do this, the shells are washed to remove any possible process contaminants, such as machine oil. This can be done, for example, in acetone or isopropyl alcohol. These solvents do not require additional drying, as they evaporate quickly and easily from the surface of the cleaned workpieces.

[0033] Then the two shells are aligned, ensuring that the rotation axes 3 of the outer shell 1 and the inner shell 2 coincide (coaxial alignment). To form a strong weld, the outer surface of the inner shell 2 and the inner surface of the outer shell 1 must be in physical contact. To achieve this, the shell diameters are selected so that the inner diameter of the outer shell 1 is equal to the outer diameter of the inner shell 2.

[0034]

[0035] After joining the shells, the resulting workpiece is subjected to heat treatment to perform diffusion welding of the shells. Diffusion welding is a process that involves mutual diffusion at the atomic level of the surfaces being welded. It offers several advantages: no solder alloys or electrodes are required; no additional mechanical treatment of the surfaces being welded is required; the weld joint is high-quality; energy consumption is low; and the thickness of the parts being welded can be varied widely, from fractions of a micron to several meters. Furthermore, the weld seam is formed over the entire contact area of ​​the surfaces being welded, resulting in a highly durable joint.

[0036] Let's consider diffusion welding of shells made of jewelry alloys using an example.

[0037] The outer tubular shell 1 is made of a gold-based alloy, such as gold-silver alloys; gold, silver, and copper alloys, with a gold content of at least 50% by weight and a silver content of at least 5% by weight. Gold alloys of 583° melt at a temperature of 835 to 926°C and contain an additive of silver of at least 8%. The inner tubular shell 2 is made of a metal alloy with a lower melting point, in particular, a hypoeutectic silver-based alloy, and has higher strength characteristics than gold-based alloys. The components of the silver-based alloy form a solid solution with a low-melting eutectic phase of silver. Silver-based metal alloys, such as Ag875°, Ag925°, Ag900°, are hypoeutectic alloys that contain silver-enriched α-phase crystals and a low-melting eutectic phase at the crystal boundaries.

[0038] When heated, the alloy begins to melt along the grain boundaries (low-melting eutectic phase), starting from a temperature of 760°C, and passes into a completely molten state at a temperature of 840°C, which is lower than the melting temperature of the alloy of the outer tubular shell.

[0039] A diffusion weld layer is formed at the interface between the adjacent cylindrical surfaces of the outer and inner tubular shells by a metallic interlayer of a low-melting eutectic phase from the metal that forms the eutectic phase in the first metallic alloy. In the embodiment under consideration, the diffusion weld contains virtually only silver, which has entered the weld from the inner tubular shell (Fig. 3).

[0040] To form a sufficiently strong diffusion weld, it is sufficient to have 5% silver additive in the gold alloy, therefore, 583° gold alloys are suitable for the manufacture of bimetallic pipes. Accordingly, you can select a gold alloy whose melting point is higher than the melting point of the silver alloy.

[0041] Although the above example refers to a bimetallic tube made of silver and gold alloys, other alloys can also be used to make bimetallic tubes, including palladium alloys, such as PdSr-86-20 and PdSr-60-40 alloys (GOST 13462-2010) with a melting point of 1340-1440°C, or PD-190 and PD-250 alloys of the Moscow Plant of Special Alloys with a melting point of 1100-1200°C, etc.

[0042] This bimetallic tube can be used in a variety of products, but is particularly suitable for making precious metal alloy items, including jewelry, costume jewelry, pen and pencil housings, and other similar items. It can also be used to make tubular cases, decorative tubular shells, and more.

Claims

1. A method for manufacturing a bimetallic tube from jewelry alloys, comprising the following stages: two metal tubular shells made of jewelry alloys are obtained and prepared, and the diameters of the shells are selected in such a way as to ensure contact between the outer surface of the first shell and the inner surface of the second shell; the connection of two shells is carried out by inserting the first shell into the second, observing the condition of coaxial alignment of the axes of rotation of the first shell and the second shell; Diffusion welding is carried out, and the welding modes are selected in such a way as to ensure the formation of a diffusion weld layer with a eutectic phase in the weld seam over the entire contact area of ​​the welded surfaces of the shells.

2. The method according to paragraph 1, characterized in that the inner shell is made of a jewelry alloy with a lower melting point than the alloy from which the outer shell is made.

3. The method according to paragraph 1, characterized in that the tubular shell made of a metal alloy with a lower melting point is made of a hypoeutectic silver alloy.

4. The method according to paragraph 1, characterized in that the tubular shell made of a metal alloy with a higher melting point is made of a gold-based alloy with a silver additive of at least 5% by weight.

5. The method according to paragraph 1, characterized in that the tubular shell made of a metal alloy with a higher melting point is made of a palladium alloy with a silver additive of at least 5% by weight.

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