Oxy-acetylene welding manual

by Lorn Campbell

(115) Contrary to most authorities we find that an abundance of good flux is desirable on brass work and that it is almost impossible to use too much. It is desirable to use only the best welding fluxes, for the best welds are to be insured only under ideal conditions. If a welder were to run short of flux, however, he might use powdered borax of the 20 Mule Team variety, to tide him over until he could get a new supply. The flux is added in the same way as the cast-iron flux, that is, by dipping the heated end of the filler-rod into the flux container. Enough will adhere, and when added will clear up the metal in the vicinity of the weld. It should be added as often as a welder notices his metal needs cleaning and this will vary depending upon whether there is a slow or rapid worker behind the torch. A man must use his own judgment in cases of this kind. Remember that the flux is a cleaning agent and if the surface is clean, no additional flux is necessary, but if the contrary is true, that is, if the surface is full of oxide and the filler refuses to flow easily, flux is necessary and should be added.

(116) During the welding, dense white fumes will come from the fusing brass. This is the burning out of the alloy, that is, the zinc. These fumes are injurious to the welder and should be avoided, if possible, by proper ventilation. The use of a proper filler-rod and rapid work will largely tend to overcome the presence of these fumes, but if the operator is very slow, they will appear, and are followed by a porous and brittle weld, which if broken afterwards will show a large number of blow holes. The most difficult part of brass welding as a whole is to add the filler-rod, being certain of a fusion, without burning out the zinc. When brass is in a heated condition, it is very fragile and will crack readily if disturbed. All precautions should be taken to see that no sudden jarring is given the piece until the weld has completely set. When this work is done many welders plunge their work in water, in an effort to make it more ductile and easier to machine. While this, of course, is condemned by theorists and rightly so, in practice there seems to be no injury results.

CHAPTER IX

Part One.—ALUMINUM WELDING

(117) So far as the actual fusion of aluminum is concerned, it is probably more easily learned than any other metal, but on account of the rapid conductivity of heat and the loss of most of its strength when heated, aluminum has caused much concern among oxy-acetylene welders.

(118) There are two methods used in welding aluminum, the flux method and the puddle method. The puddle system gets its name from the use of a puddle stick or spoon-like rod which is used to stir the metal together, and is very satisfactorily used on all cast aluminum. The flux method is applied to both cast and sheet aluminum and it is so-called because a flux is used to break up the oxide along the line of weld. The discussion to follow applies only to cast aluminum. It is in this metal that most interest is centered, as the welding of sheet aluminum, such as is found in automobile bodies and some cooking utensils, is not encountered in the ordinary run of work.

(Courtesy of the Torchweld Equipment Co.)

Fig. 76.—Showing Aluminum Crank Cases Before and After Welding.

(119) When working with the flux method about the same sized tip is used as when working on cast iron. This is applied to the line of weld and held there until the oxide on the surface commences to wrinkle and small globules of a mercury-like appearance form on the surface. When heat is introduced in aluminum it is transmitted throughout the piece in the same manner as occurs in copper and brass, therefore it will require much more time to heat the work than the same sized piece of cast iron or steel. As soon as the weld assumes the condition mentioned, fast work is necessary or the metal will collapse, for it loses most of its strength when heated to this condition. The end of the filler-rod bearing the flux is brought down on the metal and immediately the surfaces will clear up and run together, like so much mercury. The torch is instantly jerked away and applied farther along the weld. The theory of this reaction is that the heavy aluminum oxide is the only thing which prevents the metal flowing together when heated, and as soon as the flux is introduced this oxide will be destroyed along the line of weld and a fusion of the metal effected. This actually takes place, providing enough heat has been introduced to permit this reaction to penetrate the depth of the weld. The flux contains the chemicals necessary to cause this reaction if the metal is in the right condition. There are many welders who do not use sufficient heat and blame the faulty results upon the flux. On the other hand, there are many fluxes which are absolutely useless in performing a function of this kind. The chemicals necessary in compounding a good flux for this class of work are expensive and therefore this flux cannot be procured at a low price. When the weld is finished and cooled the surface should be scrubbed with soap and water to remove all traces of the flux, otherwise a corrosion may occur a month or so afterwards, and while it may not affect the weld in any degree, the owner of the piece may not be pleased at the sight. It is therefore advisable to remove all traces of flux used on aluminum work.