Technology of the arc-braze welding process. Recommendations and examples of industrial applications

Abstract

The ever increasing use of galvanised and aluminium-coated metal plates, and stainless steel sheet in, for instance, the industries of car making (elements of car bodies), electric machinery (ventilating, refrigerating and air-conditioning systems), food containers and ship-building, in housekeeping in furniture-making and in building (roofing and facades), etc., calls for the methods of bonding which would combine quality of the joint with the retention of the anti-corrosive properties of the original material. The use of traditional arc-welding methods for the bonding of galvanised plates creates a number of difficulties because of the intensive evaporation of zinc (boiling point – 906 °C). The zinc vapour and oxides generated during processing produce pores and gas voids in the welded joint and lead to cracking, lack of depth of fusion or even fusion itself, while the welded element loses its original anti-corrosive properties. Further, the arc becomes unstable during welding and this results in a considerable spatter. Welding of thin stainless steel sheet often results in its distortion, the loss of its anti-corrosive properties and undesirable changes in the HAZ structure.