CS259255B1 - Non-corrosive flux for melt welding of aluminum - Google Patents

Abstract

The solution concerns the chemical composition of a non-corrosive flux for fusion welding of aluminum, especially thin sheets and profiles up to 5 mm thick, using an oxyacetylene flame. The flux is in powder form and is intended mainly for welding aluminum materials in the refrigeration, food and electrical industries. It is based on fluorides and contains 30 to 50 wt. % sodium fluoride, further consisting of 30 to 39 wt. % lithium fluoride, 5 to 9 wt. % sodium fluoroaluminate or potassium fluorosilicate or potassium fluoroborate, 3 to 8 wt. % aluminum fluoride, its advantage is that it is non-corrosive and is easily removed from the weld metal.

Description

The solution relates to the chemical composition of a non-corrosive flux for fusion welding of aluminum, in particular to sheets and profiles of thin thicknesses up to 5 mm by an oxygen-acetene flame. The flux is in powder form and is mainly used for welding aluminum materials in the refrigeration, food and electrical industries. It is based on fluorides and contains 30 to 50 wt. % sodium fluoride, further comprising 30 to 39 wt. % lithium fluoride, 5 to 9 wt. sodium fluorohalite or potassium fluorosilicate or potassium fluoroborate, 3 to 8 wt. aluminum fluoride. Its advantage is that it is not corrosive and Tahko is removed from the weld metal. 259255 3 4 259255

BACKGROUND OF THE INVENTION The present invention relates to a non-corrosive flux in powder form for fusion welding of aluminum sheets and thin thickness profiles up to 5 mm oxygen by acetylene flame.

So far known fluxes for aluminum welding are based on chlorides and fluorides. Most of the melting fluxes used for aluminum welding are based on chlorides with a content of 90 to 92% by weight. and the remaining fluoride. The high chloride content makes the flux hygroscopicity, which in practice causes considerable problems with its shelf life. High-chloride melts have the property of inducing inter-crystalline corrosion of the weld joint. In order to avoid this undesirable aspect in practice, flux residues must be removed by washing with water, pickling in 20 to 40% nitric acid or 10% sulfuric acid and washing with water. These operations increase the labor and thus the cost of welding.

Non-corrosive flux according to MS. No. 11,1118 has the disadvantage of a smaller melting range and higher surface tension of molten weld, metal and molten slag, resulting in more difficult and laborious removal of flux residues.

These disadvantages are largely removed by the flux according to the invention for the fluoride-based welding of aluminum with a content of 30 to 50% by weight. sodium fluoride, which consists in that it consists of 30 to 39 wt. lithium fluoride, 5 to 9% by weight; sodium fluorohalite or potassium fluorosilicate or potassium fluoroborate, 3 to 8 wt. aluminum fluoride.

The flux according to the invention achieves excellent welding properties. The welded joint is clean and metallic shiny, the weld seam welding is good, without non-welds and pores with good mechanical values corresponding to aluminum Al 99.5 - 99.8.

Compared to other types, the flux exhibits a wide melting range, solidus of 520 ° C, liquidity of 700 ° C, and the lower surface alkaline earth content of the surface tension is lower. The slag is more fluid and, after reaction with the oxide layer, flows into the seam of the weld metal. This makes it possible for the welder to monitor the deposition and melting of the additive material and to form the weld metal so that it cannot access the uncured areas in the joint. After the welding is interrupted, the weld is free of baked flux residues and it is possible to continue welding without further treatment. For flux according to MS. No. 11,1118, the baked flux residues must be removed mechanically. The flux residues form saturated aluminum oxides which, because of their increased melting point, prevent further direct welding of the weld metal. Flux has a reduced content of toxic substances, thereby improving the welding environment.

In the fusion welding of refrigeration and freezing units to refrigerators and freezers, a flux of the following composition, 50 wt. sodium fluoride, 39 wt. % lithium fluoride, 6 wt. sodium fluoroaluminate, 5% by weight; aluminum fluoride. In another case, the flux consisted of 50 wt. sodium fluoride, 38% by weight; % lithium fluoride, 7 wt. % potassium fluorosilicate, 5 wt. aluminum fluoride.

Also, good results have been obtained with a flux consisting of 50 wt. sodium fluoride, 33 wt. % lithium fluoride, 9 wt. potassium fluoroborate and 8 pips. wt. aluminum fluoride.

The flux according to the invention is suitable for welding in particular thin sheets of aluminum and profiles A) of 99.5 to 99.8%, particularly materials and equipment in refrigeration, freezing, food and electrical engineering! industry.

Claims (1)

Non-corrosive flux for fusion welding aluminum based on fluorides containing 30 to 50 pens. wt. sodium fluoride, characterized in that it further comprises 30 to 39% YNÁLEZU wt. % lithium fluoride, 5 to 9 wt. % sodium fluoroaluminate or potassium fluorosilicate or potassium fluoroborate, 3 to 8 wt. aluminum fluoride.