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INVENTION
Patent of the Russian Federation RU2259265
METHOD OF DIFFUSION WELDING
Name of the applicant: Milyavsky Dmitry Konstantinovich (RU)
The name of the inventor: Milyavsky D.K. (RU); Koblov A.I. (RU)
The name of the patent holder: Milyavsky Dmitry Konstantinovich (RU)
Address for correspondence: 121165, Moscow, G-165, PO Box 15, LLC "PPF-YUSTIS", Pat. LS Pilishkina, reg. No. 895
Date of commencement of the patent: 2004.04.01
The invention can be used in the electronic, jewelry and other technical fields. In the welding zone, a material is provided that provides an exothermic reaction between the constituent components. Said material is produced by filling with a thermo-reactive powder of a hollow, hermetically sealed metal shell. A powder containing components providing a self-propagating high-temperature synthesis (SHS) reaction or a powder containing components in a mixture with gallium providing an exothermic reaction with diffusion hardening is used as the thermoreactor powder. In the welding zone, at least one shell or two shells of different composition are arranged. Its heating is carried out by passing a current to initiate an exothermic reaction between the constituents entering into the thermoreactor powder. Evaporate the shell by an electric explosion to produce a metallic layer on the surfaces of the parts to be welded. The welded parts are brought into contact and insulated under isothermal conditions under a nitrogen atmosphere under pressure. The method allows to reduce energy consumption and improve the quality of the connection by reducing the upper temperature limit of exothermic aging.
DESCRIPTION OF THE INVENTION
The invention relates to the technology of obtaining a permanent joint by diffusion welding in vacuum through an interlayer and can be used in the electronic, jewelry and other technical fields.
A diffusion welding method is known in which one of the surfaces to be welded is provided with blind cylindrical holes and an intermediate spacer is formed through which the parts are joined (see SU 1463415, IPC 7B 23K 20/14, 1989). The disadvantage of this method is the complexity of making perforated holes, and high energy costs.
A diffusion welding method is known in which a metal interlayer is formed in the process of pyrolysis of a substance pumped between welded surfaces, after which an isothermal holding is carried out under pressure (see SU 1750897, IPC 7 B 23 K 20/16, 30.07.1992) .
The closest analogue of the proposed method can be considered the diffusion welding method according to RU 2025241, MPC 7 B 23 K 20/16, 30.12.1994, according to which, at least on the surface of one of the parts to be welded, a cavity is made and filled with a protective activating medium in As an exothermic mixture. The parts prepared for welding are compressed, heated to the welding temperature at a high speed, isothermally held, and after the joint is formed, the parts are cooled. Under the influence of temperature and pressure, the protective-activating medium is displaced from the cavity and fed to the heated welded surfaces, which leads to a qualitative connection by removing the oxide films and crushing the micro-roughness. However, the protection of welded surfaces from oxidation is insufficient, leading to a decrease in the quality of welding.
The object of the invention is to reduce energy consumption and improve the quality of the connection by lowering the upper limit of the exothermic aging temperature.
The task is achieved due to the fact that in the diffusion welding method, comprising placing in the welding zone a material providing an exothermic reaction between the components entering into it, bringing the welded parts into contact and isothermally holding them under pressure, said material is obtained by filling the thermo-reactive powder with a hollow, And at least one shell is placed in the welding zone by heating it by passing a current to initiate the exothermic reaction between the constituents entering the thermoregressive powder and evaporating the shell by an electric explosion to form a metal layer on the surfaces of the parts being welded, and isothermal aging Is carried out in an inert gas atmosphere, preferably nitrogen.
As a thermoreactor powder, a powder containing components providing a self-propagating high-temperature synthesis (SHS) reaction can be used, the envelope being evacuated. In this case, the shell is made of permendur alloy. As the thermoreactor powder, powder containing components in a mixture with gallium can be used to provide an exothermic reaction with diffusion hardening, with gallium pre-saturated with nitrogen, and the shell is filled with nitrogen before being sealed. In this case, the shell is made of nickel or nickel alloy. Depending on the materials to be bonded, at least one shell of one composition or at least two shells with different compositions can be used, and their evaporation is carried out sequentially.
Powders with components providing SHS response are used for the first variant of use of thermoreagging powders. Technical solutions are known concerning the synthesis of materials (nitrides, carbides) by the SHS reaction. However, in the claimed solution, a synthesis and spraying of the coating on the surface of the parts to be connected is carried out in a single technological cycle while passing current through the shell with SHS powder, while the discharge plasma is used to clean the welded surfaces. Knowing the rate of SHS reaction, it is possible to obtain juvenile surfaces, which ensures high adhesion of the sprayed material.
In the experiments, powders containing graphite, tungsten, and aluminum were used.
In the second variant of the use of thermoreacting powders, powders containing components in a mixture with gallium are used, which provide an exothermic reaction with diffusion hardening. Technical solutions for the use of thermo-reactive powders for the repair of machine parts, for example, the inner-combustion engine sleeve, are known. Technological techniques and modes of obtaining permanent joints using diffusion-hardening pastes based on gallium are also known. Gallium dissolves metals, quartz glass, gases, etc., as the temperature rises. It is also known that nitrogen in the molecular state is a protective gas, and, dissolving in gallium, passes into the atomic state and becomes extremely active.
In the claimed technical solution, the thermo-reactive powders together with gallium saturated with nitrogen provide, during the exothermic reaction, 100% diffusion hardening and obtaining an all-in-one compound of strength up to 50 MPa. Gallium at a temperature of 30 ° C and above dissolves in itself all metals, oxides, etc. In this case, gallium is only a catalyst, dissolving all the metals entering into the thermo-reactive composition, allowing to synthesize nitrides of dissolved metals and not participating in the synthesis process. The authors explain the increase in the strength of the compound by obtaining supersaturated solid solutions.
The experiments used powders mainly with an excess of aluminum (7-10%) based on copper and nickel. In the process of diffusion hardening, the alloy passes into an equilibrium state, and the broken aluminum bonds are replaced by atomic nitrogen; A spatial grid of nitrides synthesized on a gallium catalyst is formed, which provides high strength of the joint.
The use of one or more shells of the same or different composition is due to the material of the parts to be joined. The proposed method makes it possible to combine both difficult-to-weld metals and non-metals in various combinations.
The manufacture of shells with a thermo-reactive powder is carried out as follows.
I option . A mixture for the SHS reaction is used: a pure graphite powder of 60 parts by weight, pure tungsten powder 40 parts by weight with the addition of aluminum powder, 2 parts by weight. The mentioned powders are loaded into a shell of permendur and profiled in the form of a rectangular tube. The shell is sealed and evacuated.
II option. Technical gallium Ch. 0.96 according to known technology is pre-saturated with nitrogen. A thermo-reactive powder of the mark PT-19M-01 and gallium in a 1: 1 content by weight, previously stirring, is placed in a nickel shell. The shell on one side is sealed, filled with known nitrogen technology, sealed and placed in a refrigerator.
The figure shows the scheme of the diffusion welding installation.
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In the vacuum chamber 1, between the working table 2 and the punch 3, the welded parts 4 and 5 are placed with the shell 6 installed between them, containing a mixture of thermoreactor powders 7. The sheath is connected to the holders of the high voltage electrodes 8. The holders are included in the pulse current generator circuit 9. The heater 10, Located in the process chamber, serves to conduct isothermal aging. A gas supply system 11 serves to supply gas to the chamber. An example of a method in which two shells of different compositions are used. The punch and the work table are fixed with welded parts made, for example, from quartz 12B1 and molybdenum MV4P, on the holders are fixed shells with thermo-reactive powders, between which there is an exothermic reaction in two variants. The chamber is sealed and evacuated, to about a pressure of 1.33 × 10 -2 Pa. Then, the first envelope (with SHS powder) by direct current transmission from the power transformer 10 is heated for 20-25 seconds to a temperature of 1000 ° C and the electrical explosion is evaporated, switching the electric circuit by 2 UT, with an energy reserve of 20 KJ. Then a similar operation is carried out with a second shell (the components in a mixture with gallium), only the temperature of the shell heating is 750 ° C. |
After evaporation of the last shell, nitrogen is introduced into the process chamber through a gas supply system and an isothermal holding heater is turned on. The speed of temperature rise is not limited, but it must exclude the thermal shock of the welded part.
After reaching the temperature of the welded parts 200 ° C they are brought into contact at a pressure of 5.0 MPa. The temperature interval of isothermal exposure is not determined, because It can be from 40 ° C to 1000 ° C depending on the materials to be welded.
The advantage of the claimed method of diffusion welding through the interlayer is the extremely low temperature of isothermal aging (from 40 ° C) and low pressures (from 1.0 MPa).
The following are examples of welding using shells with powders capable of reacting self-propagating high-temperature synthesis (SHS), with various combinations of powder compositions and materials of the parts being joined.
EXAMPLE 1
It is known that only two methods of sputtering pass with diffusion into the substrate. This is a spraying of plasma focuses and an electric explosion. A method for forming a tungsten carbide support for gyro rotor support is proposed. Sheath of alloy 29 КФ (permendur). The powder composition is tungsten plus carbon in equal weight fractions and 2 wt% aluminum. Shells of this composition evaporate in the hole of the support to form a refractory support up to 1 mm thick, followed by diffusing annealing and grinding. The advantage of the method lies in the fact that the use of high temperature technology and the formation of coatings by spores for retaining the lubricant are excluded.
EXAMPLE 2
Welding of an alloy, for example VK8 with STZ, for high-temperature cutting of materials, when soldering of such materials is excluded. The shell has the composition of the powder the same as that given in Example 1. The shell material must have a temperature not lower than the melting point of the steel. After evaporation of a number of conductors, the parts are brought into contact with deformation up to 20%, followed by diffusing annealing. Diffusing annealing is carried out in a vacuum.
EXAMPLE 3
The use of a shell with powders capable of thermoreagging during heating and diffusion hardening, for welding refractory materials with materials with a complex structure, heating of which is higher than 400-500 ° C when welding is unacceptable (sital, ferrites, piezoceramics, etc.).
The composition of the powders is 50% thermoreactive powder and 50% gallium (by weight). After evaporation of a number of conductors at the temperature of the welded samples no higher than 400 ° C, the welded parts are brought into contact, diffusing annealing is carried out, followed by cooling at a rate of no more than 12 ° C per minute. Diffusing annealing is carried out under a nitrogen atmosphere.
EXAMPLE 4
Welding using shells with a composition capable of reacting SHS, and powders capable of thermalreaction and diffusion hardening.
Aluminum nitride is welded with the materials listed in Examples 1-2. Welding is carried out in a vacuum with diffusing annealing at a temperature of no higher than 400 ° C in a nitrogen atmosphere.
When welding, the samples are heated to 400 ° C, the shells are successively evaporated with powders capable of reacting SHS and thermo-reactive powders. The parts are brought into contact, isothermally held and cooled at a rate of 12 ° C per minute. Similarly, the welding of precious metals with semiprecious and precious crystals, always always the first evaporate powders, capable of the reaction of SHS.
CLAIM
A diffusion welding method comprising placing in a welding zone a material providing an exothermic reaction between the components entering into it, bringing the welded parts into contact and isothermally holding them under pressure, characterized in that the said material is a hollow, sealed metal shell filled with a thermoregressive powder , Wherein at least one shell is placed in the welding zone by heating it by passing a current to initiate an exothermic reaction between the components entering into the thermoregressive powder and evaporating the shell by an electric explosion to form a metal layer on the surfaces of the parts to be welded, and the isothermal holding is carried out in Atmosphere of an inert gas.
2. A method according to claim 1, characterized in that a powder containing components providing a self-propagating high-temperature synthesis (SHS) reaction is used as the thermoreactor powder, and the shell is evacuated.
3. Method according to claim 2, characterized in that the shell is made of a Permendur alloy.
4. A method according to claim 1, characterized in that a powder containing components in a mixture with gallium providing an exothermic reaction with diffusion hardening is used as the thermoreactor powder, wherein gallium is pre-saturated with nitrogen and the shell is filled with nitrogen before being sealed.
5. Method according to claim 4, characterized in that the shell is made of nickel or nickel alloy.
6. A method according to any one of claims 1 to 5, characterized in that at least two casings filled with different compositions are used, and their evaporation is carried out in series.
print version
Date of publication 09.12.2006гг
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