ROAD AND WORKSHOP by Handyman
Page 53
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Arc Welding Hints—Alloys
A LUMEN1UM in its own pure form 1-3would be of little service to the vehicle industry. Therefore, it must be alloyed to several other elements, such as copper, nickel, manganese: silicon, and so on—and not all of these combinations are easy to weld.
Also, because of a high degree of contraction, the main problem for the welder is distortion and cracking. Another important feature is the current, and here the ordinary ac. transformer is not a practical proposition for alloy welding— this is because of interference caused by the alternating current flutter ". Direct current is, therefore, recommended, and this, of course, calls for either a welding rectifier or a motor-driven generator.
A word on the flux surrounding the electrode: extra care should be taken of the electrode 'both during storage and handling, as the flux plays a most important part in controlling the arc. Also, although the flux will do its job satisfactorily in placing the deposit, it is important that the slag is removed at the earliest possible moment, otherwise it will begin to attack the material. Strong wire brushing and a hot water rinse will usually kill the chemical action. However, in difficult cases—apertures, corners and sri on--a hot 3 per cent nitric acid soak may be needed.
The electrodes are heavily coated and permit ,almost " touch " welding; in other words, a really short -arc with the electrode almost riding on the flux. Electrodes of 12, 10 or 8 gauge are regularly used in vehicle repair, and the current would range 50 to 70 amp. at 12 gauge, 70 to 100 amp. at 10 gauge and 100 to 130 amp. for the 8 gauge. A further point of some importance is that because of the short "touch" arc, the actual arc voltage will be low, and therefore the amperage will be somewhat higher than the dial setting—this is where the welder will find that "feel" is becoming more and more important.
Another factor to hear in mind is that the electrode will melt at a faster rate than the work, and unless it is possible to pre-heat the work, there is a procedure to learn as an alternative. This is to strike the arc ahead of the intended weld start point; this will permit the heat to spread and so even out the temperature as the start is reached. If it is not possible to lead up to the start, another method is to oscillate the -electrode in order to build up heat, but this will produce piling. It is also necessary to work quickly to avoid further piling. In preparation, apply the same technique as with other.metais, prepared butt welds to he bevelled to 71:40° where the section is more than in. in thickness, but the electrode should beat 90° to the work; weaving is also recommended and should cover the sections equally. In joining angles, it is wise to avoid the fillet weld if possible, as slag can be trapped in the root and cause early corrosion. On a casting of any bulk it. is advisable to warm up or pre-heat, otherwise the hot electrode on the cold metal will cause porosity.
This Week's Winner THIS Week's prizewinner is Mr. D. J.
Farrow. .of tit. Yarmouth, Norfolk. His idea concerns Perkins R6 engines as fitted to Bedford S-type chassis. When removing the sump, he says, the two inside bolts at the front are most difficult to get at, and it is often necessary to take out the front engine-mounting plate. If, when this is removed, it is heated and the back edge shaped inwards it will be found that when the sump is next removed a socket extension will reach the " difficult" bolts.
Comments Handyman: This is a good answer to an awkward arrangement.