SU1558588A1 - Method of electric resistance brazing - Google Patents

Abstract

The invention relates to soldering, in particular, to methods of soldering by electrical resistivity, and can be used in various fields of engineering. The purpose of the invention is to improve the quality of soldering by self-regulating the heating process and expanding technological capabilities. When assembling, a mixture of non-conductive flux and solder is placed between the ends of the soldered parts. The parts are connected to the contacts of the current source and transfer the flux to an electrically conductive state by indirectly heating the junction zone to the melting point of the flux with an additional electric heater connected to the direct heating source in parallel to the soldered components. Direct heating is performed to the soldering temperature by direct current passing through the paed connection. Parallel connection of direct and indirect heating circuits to one current source ensures self-regulation of the heating process — at first, the current flows only through an additional heater, and after the flux melts, almost all the current flows through the parts and the connection. Such connection of the heater ensures uniform heating and improved soldering quality. 1 il.

Description

soldering temperatures of the current passing through the soldered connection.

When electric circuits are closed, current due to the large resistance of the pasty mixture in a cold (solid) state passes through heater 6, causing its intense heating. The heater 6 indirectly heats details 1 and 2 and the paste mixture. When heated to the melting point of the flux, the pasty mixture begins to be squeezed, its resistance drops sharply and becomes less than the resistance of the heater. As a result, the current begins to flow directly through parts 1 and 2 and the paste-like mixture 3. Since the resistance of the paste-like mixture is higher than the resistance of the parts, the main heat generation occurs in the zone where the mixture is placed. This leads to a rapid achievement of the soldering temperature. The solder spreads over the ends of the samples, after which they are compressed with a force of 2-3 kg / mm1 to form a joint and remove excess solder with flux residues from the soldering zone. The current is then disconnected and the junction is cooled down in the clamped state to the crystallization temperature of the solder.

Temperature control is carried out indirectly, at the beginning and end of the melting of the pasty mixture. The soldering process is actually self-regulating due to the shunting of the indirect heating circuit of the circuit. Part t - mixture 3 - part 2. The heater is installed either symmetrically to the soldering point (when soldering homogeneous metals), or is shifted towards the part with lower electrical resistance and higher thermal conductivity.

Example. The soldering of round specimens from Art. S with specimens of aluminum alloy AD1 with a diameter of 20 mm was produced. Pa flax blend made from

ten

15

20

25 here

85884

solder powder grade PA25A with so pl. 425 ° C and flux brand FA with so pl. 380 ° C for soldering aluminum. The heater is made of graphite. Brazing is performed on an MS-20.08 machine for resistance butt welding, the solder mixture is placed between the ends of the soldered parts and the parts are compressed. The preheating was carried out to the melting point of the flux (380 ° C), and then the samples were heated to the soldering temperature (x440-450 ° C) by direct current flow. After that, the current is turned off and the samples are cooled under pressure to the solidification temperature of the solder.

Mechanical tests of the samples show good stable quality of the solder joint. There are practically no soldering defects (non-solder, oxide inclusions, pores, etc.). The tensile strength is close to the strength of the melted alloy. A.

Claims (1)

Invention Formula A soldering method, in which a mixture of non-conductive flux and solder is placed between the ends of the paired parts, converts the flux to an electrically conductive state and produces direct heating to the soldering temperature of the current passing through the parts and the solder connection. that, in order to improve the quality of soldering by self-regulating the process, the expansion of technological capabilities was heated, the flux was converted to an electrically conductive state by indirectly heating the junction zone to the melting temperature f It is connected with an additional electric heater connected to the source of direct heating in parallel with the steam components.