TECHNO-WELD EXPLAINED
TECHNO-WELD is for fusion welding Aluminium without the need for expensive equipment or a very high degree of welding skill.
TECHNO-WELD works on any grade of Aluminium and Aluminium alloy including "birmabrite", Cast alloys and very low melt alloys like Mazak " Pot " metals and Zinc alloys - with care it is even possible to weld Magnesium alloys. This is possible because TECHNO-WELD fusion welds Aluminium at 380ºC -that's 200ºC below the melting point of most Aluminium.
It is important to clean the joint or repair area with the stainless steel brush to remove any traces of ferrous particles from the work area which will have been deposited by tools used such as drills, files or snips. You do not have to worry about any oils that have permeated the metal, as they will not affect the TECHNO-WELD process.
Like soldering it must be the heat from the Aluminium that melts the TECHNO-WELD rod. Heat the general area and KEEP THE FLAME MOVING - as this makes it virtually impossible to overheat. The right temperature is achieved by touching the rod on the surface of the heated Aluminium in the work area, but make sure that the rod is OUT OF THE FLAME! As soon as the temperature of the Aluminium is at 380ºC the rod melts - DO NOT APPLY ANY MORE DIRECT HEAT.
Whatever job you are doing, whether it is joining or building up missing parts - the initial application of TECHNO-WELD must always be the same Once the application has been made - then you can melt the rod in the flame to make up missing parts or make modifications. By using careful heat control you can hold TECHNO-WELD in a "pasty" stage and mould it to shape before final dressing back.
When joining components, coat both surfaces with TECHNO-WELD and then re-heat gently until the TECHNO-WELD becomes molten and then draw a fillet. Generally the joint will be stronger than the parent material. It is nearly as hard as mild steel and can be drilled, tapped and machined like any other metal.
(Fig. 1
This is a bead of TECHNO-WELD on an oxide layer between the molten TECHNO-WELD and the Aluminium (Fig. 1), because although the oxide is cleaned off when brushed with the stainless steel, as soon as the Aluminium is heated it re-oxidises immediately
(Fig. 2)
The Aluminium oxide is very hard. It is broken by scratching through the molten TECHNO-WELD with the stainless steel abrader (Fig. 2). Once the oxide layer is just slightly broken, the TECHNO-WELD gets onto the Aluminium, and manganese in the TECHNO-WELD rod splits the oxygen off of the Aluminium oxide, depositing Aluminium, leaving the oxygen free.
(Fig. 3)
Magnesium which is also a constituent of the TECHNO-WELD rod "grabs" the free oxygen to form Magnesium Oxide, which being very light floats to the surface of the weld pool preventing any further oxidisation. This reaction generates heat, which together with the background heat of 380 degrees C raises the temperature in the molten area high enough to melt the Aluminium, causing a fusion of TECHNO-WELD with the parent metal.
To join components, both surfaces are coated with TECHNO-WELD, jigged together and then re-heated until the TECHNO-WELD becomes molten.
Generally the joint will be stronger than the parent metal. It is nearly as strong as mild steel and can be drilled, tapped and machined like any other metal.
HOW TO HEAT ALUMINIUM PROPERLY.
Aluminium is very conductive and therefore is very good at moving heat away from where it is needed. It is necessary to heat back from the joint area and push the heat into the area in which you want to weld.
Fig 5) Correct. (Fig 6) Incorrect
THICK TO THIN.
When joining thick section Aluminium to thin, or a small part to a larger casting ALWAYS apply the greater amount of heat to the larger component and use the heat transfer from the larger mass to re-melt the TECHNO-WELD in the join area.
MAGNESIUM, MAZAK AND LOW MELT METALS.
It is not always possible to know whether a type of cast alloy will melt below the melting point of TECHNO-WELD just by looking at it. If the metal melts at the same temperature as TECHNO-WELD or just before then a different technique is used.
To test the melting point of a suspect metal, place a small piece of TECHNO-WELD and a similar sized sample of the metal on a flat metal surface and heat evenly from below checking to see when the sample melts.
To apply TECHNO-WELD to a low melt metal, the process is closer to conventional welding. Warm the work piece generally, then using a smaller concentrated flame heat the work area, continually prodding it with the stainless steel abrader until you see the surface just starting to lift. Then heat the TECHNO-WELD rod into the job, as you would do for a conventional weld.
TROUBLESHOOTING.
There are only two problems you might encounter -
This is caused by the joint cooling too quickly because the heat has been too localised in the joint area. The heat in the Aluminium should be sufficient to keep the TECHNO-WELD molten for at least 6 seconds (on large castings 15 - 20 seconds).
This is caused by the TECHNO-WELD rod being heated by the flame, either because it is being directly heated, or the flame is not moved back enough when checking the temperature of the Aluminium.
Peter Remfry, Sole Proprietor, T/A Thrust Distributors
P.O. Box 783822 Sandton 2146
( (011) 883 4857
E-mail: kalent@global.co.za
Compiled by G Baldwin
Last updated on 19 October 1998