Chapter XIX: Part THREE: Aluminum Welding

(=131=) Many times aluminum crank cases which have large holes punched in them and parts missing are brought to a welder for repairs. A question arises as to whether it is best to back up these holes and fill in the missing parts with a filler-rod as the welding progresses, or whether these parts should be cast separately or cut out of another crank case. It will generally depend upon the size of the hole, as to the desirable procedure in a case of this kind. It must be remembered that if the casting and welding are to be done at one and the same time each additional layer of metal must be fused to the last layer and that in reality a great deal of welding is necessary. In addition this added metal must be fused to the crank case. On small holes, perhaps two or three inches in diameter, this method is recommended, but if the hole is much larger, it is best to cast a piece and then weld it in, for in this instance there is only one line of weld to look after.

(=132=) On aluminum work it is proper to weld from the closed end of a crack toward the open, whether the piece has or has not been preheated. This is true also of all other metals, for if the weld were to be started at the open end and worked backwards there would certainly be internal strains set up, which would be undesirable. If it is not clear which end is the open one, the operator should stop a moment and figure it out.

(=133=) Were a suspension arm of the U type on an aluminum crank case to break about three or four inches from the body of the case, it could be welded in place without dismantling the motor, if handled properly. Free access must be had to the line of break, so that the operator can manipulate his flame at whatever angle he thinks best. Due to the contraction and expansion, which may throw the piece being welded out of alignment slightly, it is best to blank the bolt hole at the end of this suspension arm and face it off, before the piece is welded in position. Later a new hole can be drilled which will line up accurately with the frame, and the welder will not then have to worry or attempt to return it exactly to its former position. In order to keep the case itself as cool as possible, wet asbestos should be packed around it, near the broken arm, so that too much heat will not be absorbed by it. The broken end is then tacked in position at two or three places and the weld started. On such a problem the puddle system will be found best, for both horizontal and vertical welding are to be done, as well as some overhead. As flux causes the metal to flow, it is rather difficult for the beginner to apply it to vertical and overhead work. The puddle stick should work through the metal its full thickness and eliminate every possible trace of the break, digging out the old metal where dirt is found, and adding new metal for reinforcing. When one side has been welded and reinforced it should not be allowed to cool while the other side is being worked. The torch should be played upon it every now and then, in order that the whole line of weld will be at approximately the same temperature; otherwise, the weld may break in cooling. The ease with which aluminum is puddled together, which many welders have likened to the children’s method of making mud pies, seems so simple to the beginner that he cannot see where the strength comes from when cooled. On account of this, he invariably works his aluminum too long. After welding a few test bars of this metal and breaking them in the line of weld, many old welders will gain confidence upon seeing the results of their own efforts.