RU2014977C1 - Method of microplasma welding of light alloys - Google Patents

Abstract

FIELD: welding of non-ferrous metals. SUBSTANCE: method comprises steps of placing parts of light-weight alloys into a container, having aqueous solution of electrolyte with concentration of potassium hydroxide 0.001-0.005 g/l at temperature of the solution, equal to 20 C, as a flux; carrying out the process in a microplasma mode at asymmetric pulsating current with density 5-10 5...20 A/дм², voltage 400-600 V, frequency 50 Hz over 60-200 min. EFFECT: simplified welding process due to elimination of preliminary cleaning and etching of parts, welding of complex configuration parts. 2 cl, 1 tbl

Description

 The invention relates to methods for microplasma welding of light alloys with a pulsating current.

 A known method of arc welding under a layer of protective fluid from oxidation by atmospheric air, such as salts, acids and alkalis [1]. Also known is a method of welding aluminum in microplasma mode [2].

 Regardless of the method of welding, the surfaces of the edges to be welded should not only be mechanically cleaned, but also well etched with various etchants. After processing the metal with etchants, it is necessary to thoroughly rinse the places of etching with warm water and dry them with warm air or, in extreme cases, wipe with dry wooden sawdust. All this reduces labor productivity and worsens its conditions.

 Virtually none of the methods can be used to weld precision parts of complex configuration.

 The purpose of the invention is to increase the productivity of the process by eliminating the preliminary mechanical cleaning, washing and etching of parts.

 Another goal is to create such a method that allows you to automatically weld the details of a complex configuration, including precision without tracking the trajectory of the joints of the welded parts.

This goal is achieved in that the parts are welded in a tank with an alkaline electrolyte with a potassium hydroxide (KOH) concentration of 0.001. 0.005 ... at a solution temperature of 20 ... 60 ^C.

 The welding process is conducted in microplasma mode.

 The proposed method is specifically as follows.

Pre-assembled parts are placed in a bath (container) with an aqueous electrolyte solution with a concentration of KOH - 0.001 ... 0.005 (1 ... 5 g per 1 l) and an electrolyte temperature of 20 ... 60 ^o C.

The process is conducted in a microplasma mode for 60 ... 200 min with a pulsating current of positive and negative polarity with a frequency of 50 Hz, with a ratio of cathodic and anodic current intensities I _k / I _a = 1.0 ... 1.3 and a voltage of 400 ..600 V, current density 5 ... 20 A / dm ² .

 Since the indicated voltage is higher than the electrolyte sparking voltage, many microarc and arc discharges (whose temperature is up to 3300 K) arise rapidly moving along the surface of the assembly electrodes between the electrolyte and the assembly electrode. As a result, microplasma welding of tightly connected edges of the welded parts occurs. Since the microplasma process proceeds on all surfaces simultaneously, the shape (geometry) of the parts to be welded will not affect the welding process. Moreover, the proposed welding method does not require preliminary etching and edge preparation.

However, it should be noted that the strength of the weld depends on the composition of the flux, the concentration of the electrolyte, the time of the welding process at the specified ratios of the cathode and anode currents 1 ... 1.3, current density 5 ... 20 A / dm ² , voltage 400. ..600 V, the pulsating current frequency of positive and negative polarity is 50 Hz.

The table shows the dependence of the weld characteristics of parts made of aluminum alloy D16 on the composition of the flux-electrolyte at a processing time of 120 min and a current density of 20 A / dm ² .

In examples 2 and 3, the Na ₂ SiO ₃ salt was introduced into the electrolyte in a concentration of 2 g per 1 liter in example 2 and 3 g per 1 liter in example.

 The indicated electrolyte salt may contain up to 12 g per 1 liter. Concentration depends on the grade of the welded alloys and the requirements for the weld.

The strength of the welded joint σ _{su is} achieved after 180 ... 200 minutes of processing 340 MPa, which is almost compatible with the strength of the base metal.

 Using the proposed technical solution in comparison with the known one greatly simplifies the welding process, allows you to weld parts of any configuration, including precision parts without tracking the path of the joints. After welding, washing and drying of the welded parts is not required. Simply wipe the product slightly.

It can be used at the enterprises of the clothing industry, especially when welding small parts from aluminum alloys, which require high heat resistance of the surface, because simultaneously with the welding process, a layer of material is formed on the surface of the parts to be welded, which consists of solid phases containing α = γ = Al ₂ O ₃ and mullite.

 The phase ratio depends on the grade of welded alloys.

 The layer thickness after 180 ... 200 min reaches 200..400 microns, depending on the processing mode and the material being processed.

 As you know / this layer gives the parts to be welded high wear resistance / heat resistance / corrosion resistance.

Claims (2)

1. METHOD OF MICROPLASMIC WELDING OF EASY ALLOYS by pulsating current, characterized in that the parts are welded in a tank with an alkaline electrolyte with a potassium hydroxide concentration of 0.001-0.005 g / l at a solution temperature of 20-60 ^o C. 2. The method according to claim 1, characterized in that the welding process is conducted with a pulsating current frequency of positive and negative polarity 50 Hz, while the ratio of the cathode and anode currents is 1.0 - 1.3, the current density is 5 - 20 A / dm ² , voltage - 400 - 600 V.