Oxy-acetylene welding manual

by Lorn Campbell

Part Two.—STEEL WELDING

(92) It is still supposed that the beginner knows very little about the various kinds of metals, or methods of distinguishing between them. This is of great importance and should at once be overcome, as he will not at all times have someone over him to diagnose his case and tell him the proper procedure. For instance, were he to be given a piece of cast steel to weld, thinking that it was cast iron, he would use a cast-iron filler-rod in executing his weld. The results of such a weld would not be very favorable, and the same would hold true if a steel filler-rod were used on cast iron. An occasional glance at the table in [paragraph 67] will acquaint him with the various tests to make when deciding upon the nature of the piece to be worked upon. The tests should be applied in every doubtful instance. When working on cast steel, a student may think that he must have a cast-steel filler-rod, but this is an exception to the general rule and he can use the same style filler-rod as he would employ on ordinary steel work. It might be mentioned here that when working on alloyed and high-carbon steels, the filler-rod generally contains some of the alloy or carbon which will tend to replace that destroyed by the action of the flame in the original metal.

(93) In welding cast steel the same procedure takes place as previously described for steel, and it should present no real difficulties after that process is understood. There may be more sand, oxide and other impurities present on account of the nature of the metal, but these can all be worked out if plenty of heat is applied. At times, when working in steel, it will be found that there may be a small hole develop in the center of the weld and as the torch is worked into this hole it is found that it goes down a short distance and seemingly refuses to be worked out. This is what most welders call a “crater,” and is caused by the metal at the bottom not being hot enough for the surrounding melted metal to fuse it. When found they should be removed before adding any more metal. By playing the torch flame around and around it, so that the heat may be transmitted to the bottom of the “crater” and it brought to the melting-point like the surrounding metal and suddenly jerking the torch away, it will disappear. “Craters” are generally formed during the first part of the weld, especially if the “V” is narrow, and they are hard to handle when deep. Under no circumstances should the filler-rod be melted into them in trying to make them disappear, as this will only mean covering them over.

(94) Some welders find that hard spots develop in their welds which they have difficulty in overcoming, and it is a very serious handicap when the weld is to be machined, for ofttimes it will break very expensive tools and leave a portion of a drill or die broken off in the metal. It is probably safe to say that the principal cause of hard spots in steel welds is due to lack of heat. This, if given careful thought and consideration, will be brought home forcibly to the welder as he proceeds in his work, for the lapping of metals, trapping of oxides, “craters,” too rapid cooling, etc., may all be directly attributed to a lack of sufficient heat. If the metal is in a molten state, all impurities will be brought to the surface, for they are bound to be displaced by the weight of the metal, the same as corks in a barrel will float to the top if water is introduced. The water in this case has a greater specific gravity than the corks.

Fig. 61.—The Open Ends on long Steel Welds will Overlap as the Welding Progresses if Improperly Started.

Fig. 62.—Showing how Open Ends of Steel pieces are Spread Slightly to Overcome Lapping of Ends in Making Weld.

(95) In welding on sheet iron and steel, many operators will find that they have more difficulty in executing a successful weld than on slightly heavier work. This is no doubt due to the thin nature of the work and the ease with which it may be burned or carbonized if the operator is not alert. When working on such material a very small filler-rod is used if thought necessary but this rod must be as free from impurities as possible. When working on a long seam such as may be encountered on a steel tank, it will be noticed that in welding from one end along the seam that the metal ahead of the flame will tend to overlap as shown in [Fig. 61]. This may be overcome by tacking (that is, fusing the metals together), at various points before starting the weld, or the parts ahead of the torch can be separated as is shown in [Fig. 62] and held this way by using a wedge. This is moved along as the weld advances and permits the edges to close together. Another method used by manufacturers who make a specialty of this work is to construct a jig which clamps the ends rigidly and they are welded while in this position. This phenomenon in steel welding will appear rather strange to the welder who has had some experience on thin cast-iron work, such as oven doors and the like. In these he found that as his weld advanced, the welded portion before him would separate, and when he had welded about four inches or so it would be necessary for him to jump his flame back to the beginning of his weld and heat up that portion, in order to close up the cracks before him previous to his continuing the work. This is illustrated in [Fig. 63]. This may be explained by the fact that steel is a very ductile metal and when it is fused, the expansion is taken care of internally by the two edges combining. Then, in cooling, the metal contracts, an action much more rapid in steel than in cast iron, and draws the edges of the steel plates past each other so that they overlap. In cast iron, which is rigid, the edges are expanded by the fusion of the metal and this space is then filled up with new metal, holding the edges apart. As the weld progresses the metal ahead of the torch is pushing out, and that behind is cooling off, which acts as a lever on each side to open up the unwelded ends.

Fig. 63.—This Illustration Shows how the Open Ends of Thin Cast-iron Pieces Spread apart as the Weld Progresses. To Close the Edges together, Jump the Torch Flame from B to A; as A heats up, B Cools and the Lever-like Action Closes the Opening.

(96) To weld a broken automobile frame successfully the body of the car should be raised if necessary, to keep it from burning and all pipes, wires and gasoline leads protected with a covering of asbestos paper. Plenty of room should be allowed, so that the welder may have easy access to the break, and the frame should be jacked up on both sides of the break until the frame is in proper alignment. Then weld the crack from the outside, working across the top, then down the side and across the bottom, reinforcing a little if necessary on all sides but the bottom. Then repeat this operation on the inside, reinforcing at all points. Then take a strip of steel about one-eighth or one-quarter inch thick and six or eight inches long and as wide as the bottom of the frame. This piece should be welded securely to the bottom of the frame with the former break in the middle of the strip. A cut representing this job is shown in [Fig. 64]. By this method the frame can be made stronger than originally.

Fig. 64.—A Good Method of Reinforcing a Weld on an Automobile Frame is Here Shown. The Patch as Pictured Here is only “Tacked On.” It Should be Welded Securely to the Bottom of the Frame on all Four of its Edges.