RU2558322C1 - Contact point welding of copper and copper alloys - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to welding. Invention can be used in instrument making, contact welding of high heat conductivity meats, particularly, copper and its alloys, and metal with coating base on the latter. Parts elements are assembled of copper and copper alloys. Produced assembly is arranged between welding electrodes. Welding is executed by passing welding current pulses and application of welding pressure. Welding electrodes are those made of graphite. Welding current pulses feed is performed at permanently pressed electrodes for time required for heating of part components to temperature not over 0.8 of copper fusion point. Note here that welding is performed in vacuum of 1.33·10^-2 mm Hg.

EFFECT: welding of high electric conductivity metals, stable quality of welds, higher rust resistance, minimised weld defects.

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Description

The invention relates to welding, and in particular to methods of joining parts from copper and copper alloys by the method of contact spot welding, can be used for welding parts operating in operating conditions with high requirements for the quality of welded joints, and can be used in all industries, in including instrumentation.

A known method of contact spot welding of molybdenum (see, for example, copyright certificate No. 210962, IPC B23K 11/16), in which an intermediate all-metal gasket of titanium is placed between the welded surfaces.

The disadvantage of this method is its limited use - only for spot welding of molybdenum and the economic inappropriateness of using this method.

The prototype of this invention is the method of contact spot welding (patent No. 2270081, IPC B23K 11/16, B23K 11/10, publ. 02.20.2006), according to which the method of spot welding of metals with high electrical conductivity, such as, for example, copper, aluminum , alloys and metals coated on their basis, an intermediate powdery interlayer is introduced between the surfaces to be welded, said powdery interlayer being applied to one of the welded inner surfaces of the part, while the thickness of the interlayer did not exceed 0.3 mm. The powdered interlayer consists of a PG-CP self-fluxing chromium-nickel alloy with a high electrical resistance with a content of Ni and Cr of 70-80%, the rest is C, Si, Mn, B, Fe. During welding, the molten metal of the interlayer under the action of axial loads is displaced to the periphery of the forming welding point.

The disadvantages of this method are:

- low productivity of the process and high complexity of manufacturing;

- limited use;

- there is a decrease in corrosion resistance;

the limited functionality of the intermediate layer, the components included in it do not sufficiently ensure the removal of harmful oxide and gas components from the heated contact zone;

- economic inappropriateness of applying this method;

- metal oxidation, the formation on the metal surface of a dense and strong oxide film, melting at a temperature of at least 2100 ° C, complicating the welding process and reducing the quality of the welded joint;

- it is difficult to control the heating and melting of the metal.

The problem to which the invention is directed is to develop a method for connecting parts of copper and copper alloys by the method of contact spot welding, to eliminate the above disadvantages, to expand technical capabilities through the use of vacuum and graphite tips on the electrodes. All this in aggregate forms a strong and high-quality welded joint with optimal selection of the welding mode. This allows:

- reduce the complexity of the welding process;

- eliminate metal oxidation;

- provide the necessary strength of the connection;

- provide high corrosion resistance of the welded joint;

- eliminate structural changes in the molten core and impurities in it.

The specified technical result is achieved by the fact that in the proposed method of spot welding, copper and copper alloys, which includes assembling the elements, placing the assembly between the welding electrodes and welding while transmitting welding current pulses and applying compression pressure, electrodes made of electrically conductive are used as welding electrodes material with low thermal conductivity, the transmission of pulses of the welding current is carried out with continuously compressed electrodes for the time required for heating elements to a temperature of not higher than 0.8 melting point of copper, while welding is carried out in a vacuum of 1.33 · 10 ^-2 mm RT.article As welding electrodes using electrodes made of graphite.

The essence of the invention lies in the fact that the selected welding modes provide high mechanical properties of the weld. The welding current pulses are transmitted with continuously compressed electrodes for the time required to heat the elements to a temperature not higher than 0.8 of the copper melting temperature, which ensures the intensity of formation and formation of the welded joint of parts from copper and copper alloys. Welding in vacuum and during the upsetting process cleans the welded surfaces from oxides, increasing the quality of welding, and reduces the energy consumption for heating the contact, and also provides diffusion to the full depth, which creates a connection of copper and copper alloys of increased strength. Welded joints made by this method were subjected to mechanical tests. Graphite electrodes provide localization of heat exclusively at the point of contact.

According to the prototype method, the analogue method and the claimed invention, welded parts were manufactured. The test results of the mechanical properties of parts at a temperature of 20 ° C, according to standard test methods, are presented in the table.

Example 1. A part was welded by the method of spot welding by means of copper M2 with a thickness of 0.8 mm + 0.8 mm.

The assembly was placed in a chamber that provides a vacuum of 1.33 · 10 ^-2 mm RT.article. between electrodes made of graphite. Then, welding current pulses are passed with continuously compressed electrodes for the time required to heat the elements to a temperature not higher than 0.8 of the copper melting temperature.

Contact spot welding mode for all methods: welding pressure - 0.15 MPa, welding current - 16 kA, current pulse duration - 0.3 sec, forging duration - 0.1 sec, electrode diameter - 18 mm with radius sharpening of the working part.

The diameter of the resulting weld point is 5 mm.

Example 2. The part was welded by the method of spot welding using brass L63 with a thickness of 1.0 mm + 1.0 mm according to the conditions of Example 1 under the same welding conditions.

The diameter of the resulting weld point is 8 mm.

Example 3. The part was welded by the method of spot welding using brass L63 with a thickness of 1.0 mm + copper M2 with a thickness of 1.0 mm according to the conditions of Example 1 under the same welding conditions.

The diameter of the resulting weld point is 6 mm.

The test results of the mechanical properties of parts at a temperature of 20 ° C, according to standard test methods, are presented in the table.

Ways The result of mechanical tests at 20 ° C Example 1.M2 + M2 Samples were destroyed on the base metal with a force of 100 kg Example 2. L63 + L63 Samples collapsed on the base metal with a force of 120 kg Example 3. L63 + M2 Samples collapsed over the base metal with a force of 115 kg

The results revealed the reliability of the welded joint, mechanical strength, the dependence of the welded joint on the thermophysical properties of the material. Metallographic studies revealed the presence of a molten core point from the base metal and the absence of inclusions in it.

Thus, the present invention is a method of contact spot welding that allows you to weld metals with high electrical conductivity with high strength, stabilizes the quality of the welded joint, increases corrosion resistance, reduces energy costs, improves the manufacturability of the manufacture of welded structures, welding defects are minimized with proper selection of welding modes.

Claims (1)

The method of contact spot welding of parts made of copper and copper alloys, including the assembly of parts, placing the assembly between the welding electrodes and welding by passing pulses of the welding current and applying compression pressure, characterized in that the electrodes made of graphite are used as welding electrodes, the transmission of pulses welding current is carried out with constantly compressed electrodes for the time required to heat the elements of the parts to a temperature not higher than 0.8 of the melting temperature of copper, at welding is carried out in a vacuum of 1.33 × 10 ^-2 mmHg