ELECTRODE ELEMENT FOR SOLDERING

Abstract

The utility model relates to soldering materials, in particular to electrode elements for producing soldered joints of electrical connector tips with an electrically conductive surface. An electrode element for electric arc pin soldering comprises a first part (1) for installation in a holder, a second part (2), a groove (3), a third part (4) consisting of a brass part (4.1), a flange (4.2) and a capsule (4.3), wherein the capsule (4.3) is installed on the flange (4.2) so that a cavity is formed containing solder and flux, and the solder is an alloy of copper, zinc and silver in the ratio of Ag 44-46%, Cu 29-31%, Zn 23-27%. The technical result consists in obtaining a cadmium-free electrode element that ensures a high-quality connection of a cable lug to a base, resistant to vibration and impact loads, by preventing the formation of unfilled cavities and unsoldered joints. 1 fig.

Description

[0001] Field of technology to which the utility model belongs

[0002] The utility model relates to materials for soldering, in particular to electrode elements for obtaining soldered connections of electrical connector tips with an electrically conductive surface.

[0003] Technology Level

[0004] Soldering devices and electrode elements for them are known in the prior art. Such elements are disclosed, for example, in patent RU 54595 U1 "PERMANENT JOINT," which describes equipment for laying railway track, which can be used in the installation and repair of rail joints on railway tracks.The disclosed solution is a permanent connection of elements of a rail joint of a railway track, made by means of a connecting rod in the form of a body of revolution, having a cylindrical capsule, rigidly fixed to the end of the connecting rod, made with it of the same diameter and with a sealed cavity for placing solder, formed by the capsule shell and a plug made of flux, used for wetting the surfaces of the connected elements of the rail joint during the soldering process, wherein the connecting rod is made of a stepped shape and with a technological transverse groove to ensure the possibility of separating a part of the connecting rod after soldering and forming a permanent connection of the elements of the rail joint.Since this solution relates only to the connection of elements of a rail joint of a railway track, it does not propose any improvements with respect to the electrode element used in such a connection or the composition of the solders and fluxes used in it, etc., therefore, it is obvious that an electrode element known from the prior art is used to form the connection, such as, for example, as disclosed in the following document.

[0005] Patent SE 514494 C2 "SOLDERING PINS USED IN THE CONSTRUCTION OF RAILWAYS AND PIPELINES" discloses a soldering element for use in a soldering process, consisting of a housing with a fastening part and a solder pad containing solder inside an internal cavity and a flange, wherein flux is placed inside the cavity before the flange of the solder pad is crimped onto the fastening part of the frame, a cover fixed to the flange on the fastening part, and the cavity of the solder pad can be conical, cylindrical, cylindrical with a conical end, cylindrical with a domed end, or elliptical in shape, wherein the front part of the solder pad has a domed or conical shape.This document discloses the geometric features of the electrode element, however, there is no mention of the composition of the components used, therefore, it is obvious that the components used are known from the prior art, having a composition such as, for example, as disclosed in the following document.

[0006] Patent RU 2450898 C2 "GUN AND ELECTRODE ELEMENT FOR ELECTRIC ARC SOLDERING OF RAIL CONNECTOR TIPS" discloses an electrode element for a gun for electric arc soldering of rail connector tips, made in the form of a body of revolution, consisting of two cylinders of different diameters, an annular groove is made on the cylinder of a larger diameter, a cylindrical insert made of a silver-containing material is fixed at its end, having a diameter smaller than the diameter of the cylinder, the insert of silver-containing material is closed with a thin-walled cap made of silver-containing material with the formation of an internal cavity between the surface of the cap and the end of the cylindrical insert of silver-containing material filled with flux, in which a truncated cone with a height of 1.0-1.5 mm is made on the cylinder of a larger diameter, the smaller diameter of the truncated cone on 1.5-1.8 mm less than the cylinder diameter,and an insert made of silver-containing material is fixed on the end face of the truncated cone and has a height of 4.0-4.5 mm, a thin-walled cap made of silver-containing plate is fixed with tension on the truncated cone, the internal cavity formed by the cap has a height of no more than 1.0 mm, the thickness of the cap wall is no more than 0.3 mm, the annular groove is made at a distance from the end face of the truncated cone equal to the thickness of the soldered tip of the rail connector, has a radius of curvature of no more than 0.3-0.6 mm and a diameter of 5.4-6.0 mm, and the material of the insert and cap additionally contains additives of copper, zinc, nickel, cadmium.

[0007] However, this type of electrode element has disadvantages, namely that the insert and cap material contain cadmium additives.

[0008] Although the boiling point of cadmium is 767°C, it begins to actively evaporate at temperatures above 320-400°C, and some active fluxes can accelerate the release of cadmium from the solder due to chemical reactions, for example, in alloys with tin or lead, cadmium is released earlier due to the difference in boiling points of the components.

[0009] When cadmium-containing materials are heated to high temperatures, cadmium atoms are converted into a gas, forming cadmium vapor. Upon exposure to air, cadmium vapor reacts with oxygen to form cadmium oxide (CdO), a highly toxic, finely dispersed powder that is easily inhaled.

[0010] When inhaled by humans once, cadmium can cause acute poisoning, manifested by nausea, dizziness, chest pain, pulmonary edema, and when inhaled once, it can cause dermatitis.

[0011] Frequent work with cadmium-containing materials can cause chronic diseases such as damage to the nervous system, brittle bones, lung cancer, etc., which progress due to the accumulation of cadmium in the kidneys and liver.

[0012] Therefore, the use of cadmium solders is restricted in many countries (RoHS Directive in the EU).

[0013] Also disclosed is a solution described in the Internet URL: https: / / galvoteccorrosion.com / pin-brazing / , which is an electrode element that uses a cadmium-free solder with a composition of: Ag 55%, Cu 21%, Zn 22%, Sn 2%. However, compared with cadmium-containing solder, the strength and ductility of the joint obtained using such solder become lower.

[0014] This is especially relevant for connections that, during operation, experience increased vibration and shock loads.

[0015] Disclosure of the essence of the utility model

[0016] Accordingly, the technical challenge that the solution is aimed at is to create an electrode element that is safe for use by humans and the environment and capable of providing a high-quality connection that is resistant to vibration and impact loads.

[0017] The technical result, which the claimed technical solution is aimed at achieving, is the production of a cadmium-free electrode element that ensures a high-quality connection of the cable lug to the base, resistant to vibration and shock loads, by preventing the occurrence of unfilled cavities and unsoldered joints.

[0018] The specified technical result is achieved by means of an electrode element comprising: a first part (1) for installation in a holder; a second part (2); a groove (3); a third part (4) consisting of a brass part (4.1), a flange (4.2) and a capsule (4.3); wherein the capsule (4.3) is installed on the flange (4.2) so that a cavity is formed which contains solder and flux; characterized in that the solder is an alloy of copper, zinc and silver in the ratio of Ag 44-46%, Cu 29-31%, Zn 23-27%; and the diameter of the third part (4) is made so that when the electrode element is inserted into the hole of the part to be soldered, a gap of no more than 10% of the diameter of the hole is formed.

[0019] In one embodiment, the second part (2) has a diameter equal to the diameter of the third part (4).

[0020] In one embodiment, the part to be soldered is a cable lug.

[0021] In one embodiment, the diameter of the hole of the part to be soldered is 6.4 mm.

[0022] In one embodiment, the diameter of the hole of the part to be soldered is 8.4 mm.

[0023] In another embodiment, the hole diameter of the part to be soldered is 10.5 mm.

[0024] The electrode element thus provided can be used, for example, to provide conductive connections for rails or pipelines.

[0025] Brief description of drawings

[0026] Fig. 1 shows the appearance of the electrode element.

[0027] Implementation of a utility model

[0028] When providing conductive connections, in particular rails, special attention is paid to the reliable transmission of electric current through the joints, while ensuring mechanical strength under dynamic loads.

[0029] The most optimal option, taking into account the specified requirements, is electric arc pin soldering. This is a method of connecting copper cables to the steel surface of the rails using a welding arc, providing a reliable electrical connection and is widely used for connecting grounding and other electrical circuits on railway tracks.

[0030] The arc pin soldering technology is based on the use of a portable soldering iron, a soldering gun, and an electrode element. The electrode element contains flux and solder, arranged on a metal base. When the metal base is heated, usually by induction, and the solder temperature reaches its melting point (e.g., 650-800°C for silver solders), the solder melts. Due to capillary action and surface tension, the molten solder, upon cooling, forms a secure joint.

[0031] In the known solutions, as described earlier, cadmium was present in the solder composition, the main functions of which were to lower the melting temperature and expand the soldering range, since the addition of 15% cadmium to copper-silver-zinc solder reduces the melting temperature of the solder by 50°C, as well as improving fluidity and wettability.

[0032] At the same time, the addition of cadmium to the solder composition did not have a negative effect on the mechanical properties of the joint, as, for example, in the case of adding tin or lead.

[0033] Thus, in accordance with the embodiment of the claimed utility model, an electrode element is provided, consisting of a brass cylindrical body at one end of which there is a capsule filled with flux and silver-containing solder.

[0034] For a more detailed description, let us refer to Fig. 1, which shows an electrode element, the working body of which consists of three main zones: a part for the soldering gun holder (1) (the first part), a middle non-working part (2) (the second part) and a part with solder (4) (the third part).

[0035] The first part (1) has a smaller diameter than the second part (2), and the third part (4) is composite: and consists of a brass part (4.1), a flange (4.2), solder, flux and a capsule (4.3). The second part (2) and the third part (4) are separated by a groove (3), which can be cone-shaped, rectangular, square, etc. The groove (3) provides the formation of a thermal bridge to limit the outflow of heat from the soldering zone, in addition, after soldering is complete, it serves to facilitate the separation of the first part (1) and the second part (2) of the electrode element from the formed joint.

[0036] The brass portion (4.1) in the third section (4) of the electrode element serves to secure the capsule (4.3). A flange (4.2) is provided in the brass portion (4.1) for this purpose. The flange can be straight or truncated cone-shaped to securely hold the thin-walled capsule (4.3) by means of an interference fit achieved by crimping. The capsule (4.3) itself is made of a silver-containing material.

[0037] The flange (4.2) may have an internal cavity for placing solder, which is an alloy consisting of copper, zinc and silver, in the ratio of Ag 44-46%, Cu 29-31%, Zn 23-27%.

[0038] When the capsule (4.3) is installed on the flange (4.2), a cavity is created for the flux. Fluxes suitable for soldering copper, copper alloys, and steels with an operating temperature range of 400-900°C can be used as flux. At active temperatures, the flux removes oxides from the metal surface, thereby cleaning the surface for optimal wetting of the metal and increasing capillary action in the gap between the surfaces being joined.

[0039] The specified composition of the solder used, for example, when compared with a known cadmium-free solder from the prior art, having a ratio of Ag 55%, Cu 21%, Zn 22%, Sn 2%, due to the higher copper content and the absence of tin, provides higher strength and ductility of the joint, while the working melting temperature of 665-730 °C remains below the upper critical temperature Ас3 of the soldered base (for example, for high-carbon steel - 800 °C), which eliminates recrystallization with the formation of martensite in the soldering zone. Martensite is a brittle, hardened structure, the formation of which leads to the formation of microcracks, as well as corrosion foci along the boundaries of different crystalline structures. Moreover, the resulting joint better withstands vibration and impact loads, and it can be subjected to mechanical processing (e.g., drilling, filing) without the risk of delamination.

[0040] In addition, the strength and ductility of the connection provided when using such a solder is comparable to the specified parameters for cadmium-containing solders.

[0041] For example, when comparing the solder used in accordance with the claimed solution with the solder having a ratio of Ag 35%, Cu 26%, Zn 21%, Cd 18%, in which cadmium is obviously used, the difference in tensile strength, ductility and shear strength is less than 10%.

[0042] Accordingly, the solder alloy is made in such a way that it does not contain cadmium, the vapors of which, as mentioned earlier, are not safe for humans and the environment, while providing a connection that is resistant to vibration and impact loads.

[0043] However, due to the high copper content in the solder used in accordance with the proposed solution, the fluidity of the molten solder is somewhat lower than that of solders containing cadmium or tin. For example, in the case of cadmium-containing solders, cadmium reduces surface tension and "loosens" the oxide films that form on the surface of the melt. Therefore, cadmium-containing solder behaves most actively and is able to flow into the narrowest and longest capillary gaps. In the case of tin-containing solders, tin acts as cadmium; although not as effectively as cadmium, it also lowers surface tension. However, when the temperature is elevated, tin tends to oxidize and burn off, which impairs fluidity and leads to slag formation.

[0044] Consequently, the solder, in accordance with the stated solution, has a denser and less mobile structure in its molten state than the previously mentioned solders. Consequently, it flows confidently, but more slowly, requiring more heat and time to fill long capillaries. As a result, if soldering technology is not followed, unfilled cavities and unsoldered joints may occur.

[0045] Since, in the case of providing conductive connections of rails or pipelines, cable lugs are installed at the ends of the conductive connectors, for example, such as those installed in accordance with GOST 7386-80, a hole is made in the lug to make a connection to the part being connected.

[0046] To prevent the said phenomena, a solution has been developed, according to which the diameter of the third part (4) of the electrode element is made so that the difference between the diameter of the hole, for example, of the cable lug to be soldered, and the diameter of the third part (4) of the electrode element, i.e. the gap between the wall of the hole and the electrode element inserted into said hole, is no more than 10% of the diameter of the hole.

[0047] This implementation allows for the placement of a sufficient amount of solder and flux in the cavity formed when installing the capsule (4.3) on the flange (4.2) to qualitatively fill the cavities of the connection and to ensure the insertion of the electrode element into the hole, i.e. the electrode element rests directly against the plane, which is the plane of contact of the parts to be soldered, accordingly, the solder spreads to the sides of the electrode element exactly to the places in which it is necessary to ensure the connection, while if the gap between the electrode and the wall of the hole becomes too large, then the solder, instead of spreading in the plane of contact, rushes into the gap and comes out of the connection, which also leads to the appearance of unfilled cavities and unsoldered joints.

[0048] When soldering with this electrode element, the surface is first prepared by grinding. Next, the soldering equipment is prepared. The electrode element is then inserted into the soldering gun. A cylindrical body made of a non-conductive material (such as ceramic) is placed on the electrode element. After soldering, an electric arc is formed at the point of contact between the electrode element and the surface, melting the flux and solder to operating temperature. The electrical circuit is then broken, and the main part of the electrode element is extended forward into the pool of molten solder, ensuring uniform distribution of solder along the edges of the cable lug and in the narrow gap between the cable lug and the work surface. After soldering is complete, it takes a few seconds for the solder to solidify, after which the soldering gun can be removed.The protruding part of the soldering cartridge is knocked off along the groove (3) with a light hammer blow.

[0049] The connection obtained by soldering is characterized by low electrical resistance, high mechanical strength and corrosion resistance.

Claims

An electrode element for electric arc pin soldering, comprising a first part (1) for installation in a holder, a second part (2), a groove (3), a third part (4) consisting of a brass part (4.1), a flange (4.2) and a capsule (4.3), wherein the capsule (4.3) is installed on the flange (4.2) so that a cavity is formed in which solder and flux are contained, characterized in that the solder is an alloy of copper, zinc and silver in the ratio of Ag 44-46%, Cu 29-31%, Zn 23-27%.

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