Principles of brazing technology - technicalmaterials.umicore.com

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Principles of brazing technology Brazing with flux-forming brazing rods - BrazeTec Silfos brazing alloys. Oxygen Fuel gas Copper alloys, copper-tin alloys and silver can be brazed with phosphorus-containing brazing alloys without the use of flux. The „self-flowing“ properties of these brazing alloys can be explained as follows: On melting the brazing alloy, the phosphorus in the brazing alloy reacts with oxygen in the air to form phosphorus pentoxide. This reacts with the copper protoxide on the copper surface to form copper metaphosphate which acts as a flux. As copper metaphosphate is safe from a chemical- corrosion point of view, the brazed joints require no subsequent treatment. When brazing with BrazeTec Silfos brazing alloys, the brazing time should not be longer than about 3 to 4 minutes. 4. Brazability of components According to DIN 8514, the brazability is the property of a component to be manufactured in such a way via brazing that it meets the stipulated requirements. A component can be brazed if the following conditions are met (see diagram): - the base material is suitable for brazing, - there is a brazing capability for the manufacture, namely one or more brazing techniques can be used, - and the construction can be brazed such that a sound construction results, namely satisfactory reliability of the component under the foreseen operating conditions. Comment: In electrical engineering, the expressions „solderability“ and „suitability for soldering“ are used synonymously for soldering. Soundness of the brazed joint Construction Base material Suitability for brazing Brazability of the component Suitable base material, brazing alloy and flux combinations Each of the three properties „suitability for brazing“, „brazing capability“ and „ability to manufacture a sound brazed joint“ depend on the base material, manufacturing process and joint design. The degree of dependency on these three parameters depends on the individual brazing task. Umicore AG & Co. KG - BrazeTec, Rodenbacher Chaussee 4, D-63457 Hanau-Wolfgang Telefon: +49 (0) 6181-59-03 Telefax: +49 (0) 6181-59-3107 Email: info@BrazeTec.de Internet: www.BrazeTec.de Brazing capability Manufacture
Principles of brazing technology The suitability of base materials for brazing work is shown in Table 1. Tables 1 and 3 give information about how the indicated materials can be brazed. This does not mean to say that components brazed in this way can withstand all operating loads. In order to guarantee this, the operating conditions for the brazed joints must be known prior to selecting the conditions/methods for carrying out the brazing work. These are workpiece-specific and differ from one component to the next. More detailed information on Suitability of base materials for brazing this matter can be found in the section entitled „Selection criteria for brazing alloys and fluxes“. In certain instances where there is relatively high risk of damage, we recommend that you get in touch with us to enable optimum selection of the brazing parameters. Brazing has the big advantage that virtually all materials which are suitable for brazing can be combined with each other. It goes without saying that the brazing parameters must always be selected for the most „difficult“ material from a brazing point of view. Group 1 Group 2 Group 3 Materials which can be brazed with universal brazing alloys and universal fluxes and using all standard techniques. e.g. copper and copper alloys nickel and nickel alloys iron materials common steels cobalt noble metals Table 1 Materials which require special brazing alloys and/or special fluxes, but which do not require special brazing techniques. e.g. aluminium and aluminium alloys hard metals, stellites chromium, molybdenum, tungsten, tantalum, niobium solder-like materials Materials which can only be brazed using special brazing alloys and special techniques. e.g. titanium zirconium beryllium ceramics Umicore AG & Co. KG - BrazeTec, Rodenbacher Chaussee 4, D-63457 Hanau-Wolfgang Telefon: +49 (0) 6181-59-03 Telefax: +49 (0) 6181-59-3107 Email: info@BrazeTec.de Internet: www.BrazeTec.de
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