(82) Another cylinder block job that generally causes more confusion than is necessary is brought about when welding on small lugs, such as shown in [Fig. 55]. When welding these lugs on from the outside only, they generally warp upwards in cooling and it is either necessary to build up the bottom side of this lug or to machine off the entire face in order to have the end square. This can easily be overcome by permitting the lug to sag before welding and then dress off the small portion that continues to sag, after it is welded, rather than face off the whole surface. See [Fig. 56].
CHAPTER VII
Part One.—STEEL WELDING
(83) The term “steel,” as used in the following pages, unless otherwise specified, will be the term applied to wrought-iron and low-carbon steels. High-carbon and alloyed steels are to be considered only in advanced work and will therefore not be deemed a topic of interest to the beginner in laying his foundation.
(84) The welding of steel is much more difficult than cast iron on account of the many points which must be observed. In cast iron the metal is brought to a molten state and may be worked in that condition for some time without any apparent change in the characteristics of the metal. A flux is used to break up the oxide or scale and the metal will flow very easily. The flux is necessary because the oxide has a higher melting-point than the iron itself. When working on steel, it will be observed that just the reverse is true, that its oxide has a lower melting-point than the steel and consequently no flux or cleaning powder is necessary when working upon it.
(85) A large quantity of steel kept in a molten condition by the flame acting upon it is very easily influenced. The same area is not kept in a molten condition as with cast iron. The heat does not hold to the vicinity of the weld nearly so much as in cast iron because of the greater conductivity of the metal. If the flame is removed, the molten metal will set almost immediately. This means that the flame must be in contact with the metal at all times. It must be a strictly neutral flame or else one of the two gases will be introduced into the weld and its strength will be materially affected. The size of this flame must be such that too great an area will not be covered, yet enough must be covered to keep the metal along the line of the weld in a molten condition. If a carbonizing flame is used, one which has an excess of acetylene, such as was shown in [Fig. 23], much carbon will be taken up by the metal, producing a brittle weld. If the flame is oxidizing, that is, contains an excess of oxygen which is noticed by the shortening of the flame and an accompanying hissing sound, [Fig. 25], the metal will burn and a white foam will appear on the weld like a milky white glue. This tends to weaken the weld. This same effect will be in evidence if too large a tip is used. On the other hand if the tip is too small not enough heat is obtained and the oxides and other impurities which may be present will not be allowed to float to the surface but will be trapped in the weld.
(86) The filler-rod used on steel should be as near the same grade, if not better than the metal to be welded and should be very low in its carbon content. A pure grade of soft iron wire or mild steel will make a very good filler-rod for ordinary purposes. The size of this filler-rod is very important, for it should fuse at the same time as the metal being worked upon, and unless it does this the weld will not be satisfactory. If the filler-rod is too large it will not be at the fusion point when the work is, and will not fuse with it. If the rod is brought to a melting-point the work will have too much heat and will burn. On the other hand, if the filler-rod is too small, it will burn up before the work is at the fusion point, or in other words, the work will still be too cold when the rod is melted.
(87) There are many different methods of executing a steel weld, and it has been noted that very few experienced welders handle their steel in the same manner. Most of these methods are very difficult to learn and can be perfected only after years of practice. However, a simple method which will produce results is thought the most advisable for the beginner. A careful examination and study of this point has brought out the following method, which is very easily picked up and which dispenses with most of the torch movements that are generally advocated by the old time welders.
Fig. 57.—Preparing and Heating Steel before Welding.