SU1764892A1 - Method for resistance spot welding of parts of different thickness - Google Patents

Abstract

Purpose: for spot welding of parts with a thickness ratio of 1:10 or less. The invention: between the electrode and the part of smaller thickness is placed a package of 2. 5 layers of foil. 1 tab.

Description

The invention relates to resistance welding and can be used to permanently join differently thick parts with a thickness ratio of 1:10 or less, preferably when the melting point of a thin piece is lower than the melting point of a thick piece.

For high-quality welding of parts with a thickness ratio of 1: 3, an interchangeable heat shield made of a material with low thermal conductivity is placed between the electrode and the thin part (P. Chuloshnikov. Dot and roller electric welding of alloyed steels and alloys. M., Mashinostroenie, 1974, p. 120- 121). The disadvantages of this method include: high consumption of scarce molybdenum or tungsten foil; low resistance of the electrode from the side of the screen and, therefore, the need for frequent stripping of its working end; labor productivity is low, etc.

The closest to the claimed method is contact welding, in which the remaining heat screen with a thickness of 0.05-0.15 mm is installed between the electrode and the thin part (Technologists and equipment for resistance welding, edited by B.D. Orlov, M. , Mechanical Engineering, 1975, p. 165). However, this method of resistance welding does not allow to obtain a satisfactory quality of the welded joints of different thickness parts with a thickness ratio of 1:10 or less, preferably when the melting point of the thin part is lower than the melting point of the thick part. The increase in the heating temperature of the parts to be welded here due to a decrease in the heat sink to the electrode as compared to contact welding without a heat shield is not enough to obtain the required volume of a bath of liquid metal in the contact zone of a thin piece and to form a quality welded joint. A further increase in the heating temperature due to an increase in the welding current leads to the penetration through the thin part and the heat shield, splashes and a sharp decrease in the durability of the working electrode surface and the strength characteristics of the welded joint.

(L

VI

Os

00

about

Yu

The aim of the invention is to expand the technological capabilities of the method by welding parts with a thickness ratio of 1:10 or less.

This goal is achieved by the fact that in the method of contact welding of different-thickness parts, in which the remaining heat shield is installed between the electrode and the thin part, a bag of 2. 5 layers of foil is used as the heat shield.

A comparative analysis of the proposed solution with the prototype shows that the proposed method differs from the well-known one in that a package of 2 ... 5 foil layers is used as a heat shield. Thus, the claimed method meets the criteria of the invention of novelty.

Comparison of the proposed solution not only with the prototype, but also with other technical solutions in this area did not technically allow revealing into them the signs that distinguish the proposed solution from the prototype, which allows to conclude that the criterion meets significant differences.

The introduction of the described method into the welding zone of different-thickness parts with a thickness ratio of 1:10 or less (between the electrode and the thin part), mainly when the melting temperature of the thin part is lower than the melting temperature of the thick part, the package of several foil layers causes the appearance of additional contact resistances of the foil. foil in the amount of (p-1), where p is the number of layers in the package, which are additional sources of heat generation distributed over the package thickness, which prevent heat transfer to the d. A change in the number of foil layers in a package allows, in comparison with a known method, to reduce heat removal to the electrode and to obtain, in the contact zone of a thin layer of detail, the volume of a bath of liquid metal necessary to obtain a high-quality weld. In this case, the through melting of the foil layer under the electrode does not occur and the working end of the latter with molten metal is not contaminated,

Example. When welding parts from aluminum and silver-based materials with a thickness of 50 µm with a beryllium-based alloy of 2.5 mm thickness (the ratio of the thickness of the welded parts to 1:50), a welded joint with stable quality was possible only when using the proposed method. Welding is performed on a K-718 unit for spot-capacitor welding.

with one-way current lead. As the material of the remaining heat shield, the material used is a thin piece. The table presents the technological parameters of welding, maximum (Fp max) and minimum (Fp min) breaking strength per weld point.

As can be seen from the table, high-quality welded joints in contact welding

materials with a thickness ratio of 1:10 or less, mainly when the melting point of a thin part is lower than the melting temperature of a thick one, are obtained by using a package of n foil layers as the remaining heat shield. For example, for compound A + 8% Si b 50 µm with Be 6 2.5 mm, the best mechanical test results were obtained using a package of heat shields of 3

layers (50 µm x 3) of AI + 8% Si foil, and for the PSR-62 d 50 µm connection with Be d 2.5 mm - a package of 5 layers (50 µm x 5) PSR-62. It follows from the table that when welding parts from Al + 8% Si alloy with a thickness of 50 μm and

beryllium with a thickness of 2.5 mm, the ratio of the greatest and smallest breaking forces per weld point, characterizing the ranges of the strength characteristics, is for one screen layer

1.88, for two and three layers 1.32-1.38, and for five layers, the total is 1.17. A further increase in the number of layers, for example, to six, dramatically increases this figure. Thus, the most stable and high

The results on the strength of welded points were obtained with the number of layers of the heat shield from 2 to 5.

Similar results were obtained when welding parts from alloy PSR-62, d

50 microns and beryllium d - 2.5 mm.

The use of the proposed method of resistance welding, in comparison with existing methods, ensures welding parts with a thickness ratio of 1:10 or less, including when the melting point of a thin part is much less thick, and also eliminates splashes and a sharp decrease in the working surface resistance of the electrode, the most

increase the strength characteristics of the welded joint. At the same time, it should also be noted, as a positive effect of the claimed method, that the introduction of additional distributed contact resistances into the welding zone reduces the magnitude of the amplitude value of the welding current required for high-quality welding of parts. In addition, the proposed technical solution allows for the installation welding of several foil layers of solder onto the composite assemblies of large-scale optical devices.

In connection with the absence of splashes of metal aerosols, sanitary and hygienic working conditions are improved.

Thus, in comparison with the prototype, the proposed method allows to obtain high quality welds of parts with a thickness ratio of 1:10 or less.

Claims (1)

The invention of the method of contact spot welding of parts of different thickness, in which between the electrode and the part of smaller thickness The remaining heat shield is installed, characterized in that, in order to expand technological capabilities by providing welding parts with a thickness ratio of 1:10 or less, a package of 2 ... 5 foil layers is used as the heat shield. Technological parameters of the welding process 2.0 Note. 1VDD - the maximum current of the heating pulse; 1свм - maximum current of the welding pulse; tno, is the transit time of the hot-water pulse; t "is the time during which the current reaches the value of IMM; CC6 - welding time; F - ycv.-va electrode shrinkage 2.5 3.7 0.0 30 Stability of welding could not be obtained