CS259255B1 - Non-corrosive flux for aluminium fusion welding - Google Patents

Abstract

The solution relates to the chemical composition of the non-corrosive fluxes for fusion welding of aluminum especially thin sheets and profiles up to 5 mm, with an oxygen-acetylene flame. The flux is in powder form and is intended mainly for welding aluminum materials in refrigeration, food and beverages electrotechnical industry. It's based % of fluorides and contains 30 to 50 wt. fluoride sodium, further comprising 30 to 39% wt. % lithium fluoride, 5 to 9 wt. fluoroaluminate sodium or fluorosilicate potassium or fluoroborate, 3 to 8 wt. aluminum fluoride its advantage is that it is not corrosive and easy is removed from the weld metal.

Description

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

The previously known aluminum welding fluxes are based on chlorides and fluorides. Most of the fluxes used for fusion welding aluminum are based on chlorides with a content of 90 to 92% by weight. and the remainder fluorides. The high chloride content causes hygroscopicity of the flux, which in practice causes considerable problems in its shelf life. High chloride chloride fluxes have the property of causing intergranular corrosion of the weld joint. In practice, to avoid this undesirable aspect, 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 workload and thus the cost of welding.

Non-corrosive flux according to MS. U.S. Patent No. 5,768,549; 112118 has the disadvantage of a smaller melting interval range and a higher surface tension of molten weld metal and molten slag, resulting in more difficult and laborious removal of flux residues.

The above-mentioned disadvantages are largely eliminated by the flux according to the invention for fusion welding of fluoride-based aluminum with a content of 30 to 50% by weight. % of sodium fluoride, which consists 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.

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

The flux has a broad melting interval compared to other types, solldus 520 ° C, liqvidus 700 ° C, the surface tension due to the lower alkaline earth metal content is lower. The slag is more fluid and after the reaction with the oxide layer flows down to the sides of the weld metal. This allows the welder to monitor the deposition and melting of the filler material and to form the weld metal so that it is unable to access the unsupported points in the joint. After the welding is interrupted, the weld is free of flux residues and it is possible to continue welding without further modification. For flux according to MS. U.S. Patent No. 5,768,549; 112118, the fused flux residues must be removed mechanically. The flux residues form saturated aluminum oxides which, because of the elevated temperature of the taverna, prevent further immediate bonding of the weld metal. The flux has a reduced content of toxic substances, which improves the working environment of the welders.

In the fusion welding of refrigerating and freezing units to refrigerators and freezers, it has proved to be a suitable flux of the following composition, 50 wt. % sodium fluoride, 39 wt. % lithium fluoride, 6 wt. % sodium fluoroaluminate · 5 wt. aluminum fluoride.

In another case, the flux consisted of 50 wt. sodium fluoride. 38 wt. % lithium fluoride, 7 wt. % potassium fluorosilicate, 5 wt. aluminum fluoride.

Also good results were obtained with a flux consisting of 50% by weight. % sodium fluoride, 33 wt. % lithium fluoride, 9 wt. potassium fluoroborate and 8 washes. wt. aluminum fluoride.

The flux according to the invention is suitable for welding at least thin sheets of aluminum and profiles of A) 99.5 to 99.8%, especially materials and equipment in refrigeration, freezer, 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.