RU2765870C2 - Method for connecting parts and apparatus for implementation thereof - Google Patents

Abstract

FIELD: working of metal.

SUBSTANCE: invention can be used in manufacture of bimetallic parts, e.g., for producing a connection between a nozzle made of a niobium alloy and a stainless steel adapter. An adapter is formed by surfacing on a hollow part made of a high-melting alloy, made of a less high-melting alloy. A workpiece made of the adapter metal is placed in a bath formed around the end of the vertically installed hollow part and melted using an electric discharge. The part is installed in a support, and the molten metal is continuously rotated under additional impact of a magnetic field created by a solenoid on the melt. After cooling, the resulting bimetallic part is machined. To implement the method, an apparatus containing a vacuum chamber made of a non-magnetic alloy is used, installed wherein is a rod cathode made of a high-melting material with a current lead made of a soft magnetic material located coaxially thereto, as well as an igniting electrode and a support with an axial displacement and rotation mechanism.

EFFECT: inventions ensure production of a durable, high-temperature, and hermetic bimetallic connection of heterogeneous non-weldable alloys.

4 cl, 3 dwg

Description

The invention relates to the field of mechanical engineering, in particular to the manufacture of bimetallic parts or joints by vacuum deposition of one material on another, and can be used, for example, for the manufacture of adapters between the nozzle and the head of low-thrust rocket engines.

There is a known method of induction welding of a cylindrical part to a regular polyhedron (AS USSR No. 1794610, class B23K 13/01, publ. sequentially, installing them horizontally and processing the deposited material with an inductor. The deposition process is repeated for each face after the previous one has cooled, turning the cylindrical part around the axis of rotation. The resulting part is processed to a given diameter.

The disadvantage of this method is that it is not intended for obtaining the end connection of parts installed vertically by the billet melt method and requires changes for this task.

A known method of obtaining a bimetallic part by surfacing, including a sealed installation in the area of the deposited metal of the bath (barriers), placing the deposited metal in the form of a workpiece in it, while the part is installed vertically, and the cavity of the part is closed with a lid (diaphragm) of the appropriate shape, then the deposited metal is heated until it melts with filling the bath, after which the part and the bath are cooled and the resulting bimetallic part is machined to a given shape and size (SU 375141 A1, 03/23/1973).

There are other methods in which for any part a mold is made for surfacing to place in it the original surfacing metal and the melt obtained by heating, corresponding to the shape of the deposited layer of the future bimetallic part, for example: system and method for creating wear-resistant material (EA 032732 B1, 07/31/2019 ) or a method of surfacing copper alloys on steel (RU 2753362 C1, 11/11/2020).

The objective of the invention is to obtain a strong, high-temperature and hermetic bimetallic joint in a hollow part, consisting of two dissimilar metal alloys that cannot be welded together, forming a connection of surfaces in the form of a volumetric technological lock. For example, connecting a niobium alloy nozzle to a stainless steel adapter, which is then, after machining, welded to the thruster head.

The essence of the invention lies in the methods of heating to melt the workpiece of the formed adapter, in that the workpiece from a less refractory alloy is welded by the electric arc method directly onto the end part of a hollow part made from a more refractory alloy, flowing around and filling all the gaps and protrusions, inside and outside the part.

The surfacing method provides for the installation of barriers for the deposited metal, heating this metal to a liquid state, filling the pool formed by the barriers with liquid metal, and processing the deposited metal after cooling to the specified shape and size.

According to the invention, the part is installed vertically, a bath is hermetically installed around the part in the adapter zone, and the cavity of the part is closed with a lid of the appropriate shape, the deposited metal in the form of a workpiece is placed in the bath and melted, providing a volumetric connection of the two parts, after cooling of which the deposited metal is subjected to mechanical processing to specified dimensions.

To increase the uniformity of the temperature field in the part and the melt, the part, together with the bath and the deposited metal, is continuously rotated around a vertical axis during heating.

Before the welding process, the parts are preheated to a temperature close to the melting temperature by a discharge current of reverse polarity from a separate high-voltage power source, which helps to clean the surfaces of the welded and joined parts from impurities and oxides.

In order to obtain the purity of the joint, the workpiece is welded in a vacuum chamber.

The electrical power released by the volumetric arc discharge between the cathode and the anode melts the workpiece material. The anode is a vacuum chamber and a blank with a part, the cathode is an electrode made of refractory metal. The arc discharge obtained when the igniter touches the cathode is amplified by the electric field and is displaced under the action of the Lorentz force on the end surface of the electrode under the action of the magnetic field of the solenoid. In order to obtain a better connection of parts, the workpiece and part are heated before melting by a high voltage of reverse polarity. In this case, the anode is a vacuum chamber, the cathode, with a high negative potential, is a workpiece with a part. The electrode has a low negative potential and serves to create an electric arc discharge. This electrical connection allows you to perform high-quality cleaning of the surfaces of the parts to be connected from harmful substances, because. parts, warming up before melting to a temperature close to the melting point, evaporate impurities, oxides and partially useful metal from their surfaces.

The technical result consists in the fact that the resulting bimetallic part has a volumetric, durable and hermetic connection of materials that is resistant to cyclic temperature effects. Metallographic analysis of the boundary layer confirms the presence of mutual diffusion of materials.

The proposed method can be implemented using the device.

A device is known for coating the inner surface of parts of complex configuration, containing a rod cathode of evaporating material and a current lead located coaxially with it. The device includes an ignition electrode and a solenoid for creating a magnetic field, the rod cathode is mounted for movement along the axis of the workpiece, which is the anode, the current lead is made of a magnetically soft material, and the part of the current lead remote from the cathode is placed in the solenoid, the axis of which coincides with the axis of the workpiece.

The device can be provided with a sleeve made of evaporable material adjacent to the cathode, in which a part of the current lead is placed. (Patent of the Russian Federation No. 2339734, No. 2005137621 dated 02.12.2005).

To displace and hold cathode spots on the end surface of the cathode, a magnetic field is used, created by the solenoid and transmitted to the working surface of the cathode with the help of a magnetic circuit, the role of which is played by the cathode current supply.

Based on the well-known solution, it is proposed to make a device for fusing the material of the adapter onto the part to be connected, containing a rod cathode made of a refractory material and a current lead located coaxially to it, an igniting electrode and a solenoid for creating a magnetic field, a part to be connected, which is an anode, a current lead made of a magnetically soft material, and the part of the current lead, remote from the cathode, is located in the solenoid, the axis of which coincides with the axis of the part.

According to the invention, the device additionally contains a mechanism for axial movement and rotation of the workpiece, together with the bath and the workpiece, fixed on the workpiece.

The solenoid is installed outside the vacuum chamber and is provided with an external magnetic circuit in the form of a cylindrical screen closed with the internal magnetic circuit of the solenoid outside the vacuum chamber. The outer magnetic circuit concentrates, directs and amplifies the magnetic flux towards the end of the rod cathode inside the vacuum chamber.

In more detail, the essence of the invention is illustrated by the presented drawings and further description.

In FIG. 1 shows a diagram of a setup with a vacuum chamber, which illustrates the method of joining the parts.

In FIG. 2 shows the technical result of the connection.

In FIG. 3 shows the finished bimetallic assembly unit after turning.

In the diagram, in the vacuum chamber 1, a cylindrical rod electrode 2 is installed vertically, which is the cathode. The electrode has a common design with an igniter 3 and a solenoid 4. Under the electrode, coaxially with it, there is a support for the part and the bath, consisting of a glass 5 and a thrust split ring 6. Part 7 is placed in the support, between the ring and the glass. bath 8, made of refractory metal, and on it - the workpiece 9. The bath and the workpiece are consumables. The electrode and support are made of refractory material and are reusable structural elements. The support assembly is mounted on a mechanism 10 designed to rotate around its axis and move vertically. A protective cover 11 is installed to prevent the weld from getting into the cavity of the part. The “plus” of the power sources is connected to the vacuum chamber 1. To the cathode - the "minus" of the low-voltage source. The power connection is switched to the mechanism of rotation and movement of the support: either the "minus" of the high-voltage source, or the "plus" of the vacuum chamber.

The method of obtaining a bimetallic part by welding is carried out as follows.

Initially, the “minus” of the high-voltage power source is connected to the support. The igniter 3 is turned on and a volumetric arc discharge is initiated. The glow goes in all directions from the support assembly and from the mechanism on which it is installed. Under the action of the electric power released in the electric discharge, the support is heated at a remote distance from the electrode 2, while the support is rotated using the rotation and displacement mechanism 10. Heating is carried out uniformly to a temperature close to the melting temperature of the workpiece, i.e. "to red". The heating process is accompanied by cleaning the surface of the parts included in the support from impurities and oxides, because. the parts are a cathode with a high negative potential, emitting electrons and ions from their surfaces.

After heating, the supports turn on the movement mechanism 10 at low speed towards the approach to the cathode. The high-voltage power source is disconnected from the support, and the support is connected to the vacuum chamber to a common "plus". The arc current reverses direction. The current density of the arc discharge begins to concentrate, under the action of the solenoid, in the gap between the workpiece and the electrode, the temperature of the workpiece increases, the workpiece 9 begins to melt, and the resulting melt flows into the bath 8, filling the gaps and the free space between the workpiece, the bath and the cover 11. Approach procedure accompanied by rotation of the melt under the action of the rotation mechanism 10, as well as under the influence of the magnetic field of the solenoid 4. Due to rotation, the probability of pore formation when filling gaps and voids is reduced. The movement of the support to the electrode is stopped at a distance at which the workpiece is completely melted, and the bath 8 is not yet, and after the melting stabilization time, the arc discharge is turned off. The connection is made.

A device for producing hardfacing bimetallic parts works as follows.

In the initial position, the loaded support is at a remote distance from the electrode. The "minus" of the high-voltage power source is connected to the support. The igniter 3 is turned on and a volumetric arc discharge is initiated. Under the action of the electric power released in the electric discharge, the support is heated at a remote distance from the electrode, while it constantly rotates using the rotation and movement mechanism. An arc discharge has formed between the support, vacuum chamber 1 and electrode 2, which has a relatively small and uniformly distributed current density around the support with mechanisms and an increased current density towards electrode 2. The support is heated to a temperature close to the melting temperature of the workpiece. The heating process is accompanied by cleaning the surface of the parts included in the support (8, 9, 11).

Since the solenoid 4 was initially removed from the end of the electrode 2 and installed outside the vacuum chamber 1, in order to enhance the magnetic field in the zone of the arc discharge, the solenoid is equipped with an external magnetic circuit 12 in the form of a cylindrical screen, which concentrates the magnetic field lines and directs the magnetic flux towards the end electrode 2. Vacuum chamber 1 is made of stainless non-magnetic alloy.

Electrode 2 and vacuum chamber 1 are cooled by running water.

After heating the support to a temperature close to the melting temperature of the workpiece 9, the high-voltage power source is disconnected from the support, and the support is connected to the vacuum chamber 1. The arc discharge current changes direction. The current density of the arc discharge begins to concentrate in the gap between the workpiece and the electrode, the temperature of the workpiece increases. Next, the mechanism 10 is turned on and the support is moved towards the approach to the electrode. In the process of moving, the blank 9 melts and, partially, the bath 8 melts. The minimum distance and time of the blank melt process is determined empirically. The approach procedure is accompanied by constant rotation of the melt under the action of the rotation mechanism 10, as well as under the action of the magnetic field of the solenoid 4. Due to rotation, the probability of pore formation when filling gaps and voids is reduced. The movement of the support to the electrode is stopped at a distance at which the workpiece 9 has completely melted, and the bath 4 has not yet. Upon completion of the surfacing, the arc discharge is turned off and the support is cooled.

All parameters of the cyclogram of the process of manufacturing a bimetallic part, namely: cathode current, solenoid current, support heating time, support movement time and speed, melting and cooling time, are specified empirically for specific dimensions of parts, vacuum chamber, cathode diameter, material of parts, etc. .d.

Claims (4)

1. A method for producing by surfacing a bimetallic part made in the form of a hollow part of a refractory metal material and an adapter formed on it by surfacing of a less refractory metal material, including hermetic placement around the end of a vertically installed hollow part of the bath, in which a workpiece of adapter metal is placed, while the cavity of the part is closed with a lid of the appropriate shape and the metal of the adapter blank is melted by heating with an electric discharge to fill the bath to form the adapter, the part being installed in a support that is moved along with the bath along the vertical axis in the direction of the electrode with its continuous rotation around the axis, which ensures rotation of the molten metal of the formed adapter with additional action on the melt of the magnetic field created by the solenoid, and after surfacing, the part and the bath are cooled and the resulting bimetallic material is mechanically processed. what details. 2. The method according to claim 1, characterized in that before surfacing, the hollow part is preheated to a temperature below its melting point by a discharge current of reverse polarity from a separate high-voltage power source. 3. A device for producing a bimetallic part made in the form of a hollow part made of a refractory metal material and an adapter made of a less refractory metal material formed on it by surfacing, containing a vacuum chamber made of a non-magnetic alloy, in which a rod cathode made of a refractory material is installed with a current lead made of soft magnetic material, an igniting electrode and a support equipped with a mechanism for axial movement and rotation, for coaxial placement of the said hollow welded part, which is the anode, and a bath for the welded metal of the adapter, while the device is equipped with a coaxially placed solenoid to create a magnetic field, in which is placed part of the current lead remote from the cathode. 4. The device according to claim 3, characterized in that the solenoid is installed outside the vacuum chamber and is equipped with an external magnetic circuit in the form of a cylindrical screen closed with the internal magnetic circuit of the solenoid, which ensures the concentration of the magnetic field lines and the direction of the magnetic flux towards the end of the rod cathode.

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