Self fluxing solder for use on Aluminium and its alloys.
Metal Composition: 93 Zn, 4 Al, 3 Cu
Melting: 380°c
U.T.S N/mm²: 200
Hardness BHN: 100
Soldering with SIF 555 Aluminium Solder
Historically, engineers have considered that welding aluminium presents a range of problems, due to its surface oxide and that it does not change colour when heated. With the advent of MIG and TIG welding, it is now regularly welded with great success. Certain alloys can be gas welded or brazed, but the removal of flux residue is most important, as its corrosive action will continue after the joint has been completed.
There is another ‘low temperature’ process called soldering, although the workpiece is melted. The parts to be joined are heated (even by a small propane burner) and the rod is rubbed on the work surface. At the correct temperature (370ºc), the rod is seen to melt, creating an exothermic reaction generating sufficient heat to melt the aluminium locally. An advantage of this process is that flux is NOT required. We refer to the material as SIF 555 Aluminium Solder. The product gives high-strength deposits that do not have galvanic corrosion problems between base metal and solder. The low working temperature keeps distortion and discolouration of the work to a minimum.
This process is commonly used by manufacturers of aluminium windows and doors. It is ideal for repairing and sealing defects in aluminium boats, gutters, engine parts, castings and sheets, being specially recommended for applications where flux residue removal is a problem.
The correct procedure is as follows; cracks and joints should be bevelled to a 60º to 90º Vee. Remove all dirt, grease and foreign material from the surface to be bonded. For a higher-strength bond, roughen the surface before applying the alloy. Using a carburising flame, heat the part broadly. As the temperature approaches 370ºc, rub the rod on the surface to be soldered. Continue heating the base metal until enough heat is present to cause the rod to melt off when it is rubbed on the joint. Do not overheat but be sure the entire joint surface is tinned before adding additional alloy to make a build-up. Tinning action may be improved by using a clean, stainless steel wire brush to brush through the molten metal to the base metal surface. Allow the part to cool slowly.