Chapter XV: Part FOUR: Steel Welding

(=104=) When steel is in a melted condition, it seems to be in a very susceptible state. It appears to absorb gases, and with constant working an oxidation is in evidence which materially effects the strength of the metal. When working on vanadium and other alloyed steels, if kept in a molten condition too long, many of their principal characteristics are destroyed. For this reason it is advisable to execute steel welds just as rapidly as possible. While this is true of most work, it is especially to be emphasized on steel. To assist the welder in executing welds on large steel castings, the pieces are generally preheated, so that the work will take less time, be more successful, and save both oxygen and acetylene. When working on preheated jobs, in order to get the desired angle on the filler-rod so the welder may use it without discomfort, a light heat is played on the filler-rod, a matter of six or eight inches from the end being fused and then bent to an angle of 90 degrees, so that the operator may hold the rod at some distance from his work and still introduce it in the manner he desires. Some operators weld their cast-iron filler-rods together, to get the desired angle as shown in Fig. 69, but this is not as common as the steel method, probably because cast iron will not bend and it requires some time to weld the rods together in this manner.

(_a_) shows how the steel “Filler-rod” is heated by the torch flame about 6 inches from the end and bent to the angle desired.

(_b_) illustrates how cast “Filler-rods” are handled. Since they will not bend, they are welded in the T shape shown. First one side is used in fusing, and then the other.]

(=105=) In some parts of the country boiler flues are acted upon and eaten away by the impure water used, and when high prices prevail, retipping is generally resorted to. A simple method in which they can be satisfactorily and cheaply done is as follows: Cut off the poor end until solid metal is reached, with a pipe cutter, which will tend to “V” the work as it cuts and at the same time will squeeze the edge of the pipe in. After cutting, this end of the flue is placed on the horn of an anvil and the burr on the inside, which has been made by the cutter, is flattened out. It is very important that the flue be of the same size throughout in order to permit its being cleaned. It is then placed in “V” blocks or a trough, made of angle iron, such as shown in Fig. 70, and the new end which has been prepared in much the same way is placed in the position shown in _A_ in the same figure. The piece is tacked on at two or more spots and then laid aside until the whole set of flues has been prepared in this manner. Then they are replaced in the trough and welded, one after another, being turned at one end by a helper, thus allowing the welder to do continuous work. Care must be taken at all times that perfect fusion takes place between the flue proper and the piece being added, yet at no time should the metal be allowed to run on the inside of the pipe. More metal can be added than is really necessary and can later be dressed down on a grinding wheel to the desired size, which must be such that replacement of the flue can be made. Various-sized pipes can be welded in much the same way where no reducers are obtainable, the only change being that there must be a step made in the trough which will permit the various-sized pipes being lined up correctly. Jigs for the speeding up of manufactured articles which are to be welded are always being brought out by the ingenious workman and are to be encouraged whenever possible.

(_Courtesy of the Oxweld Acetylene Co._)

FIG. 71.--Welded Cracks between Staybolts.]

(=106=) In the repair of boilers many a feasible job has been given up as impossible by the unthinking welder. Cracks have been found in fire-box sheets around the staybolts which, as soon as they are touched with the flame, seem to run and keep running. They really discourage those who are not familiar with this class of work. Many such welds have been executed and are apparently all right until tested, when they give way and make the job worse than it was previously. The trouble is in these instances that the welder has made no provision for contraction and while the job might appear to be successful, yet the internal strains exerted will not show themselves at the test. Many boiler shops have found that the flat patch is not to be relied upon and when a crack is found between two stay-bolt holes, such as shown in Fig. 72, a round hole is cut as shown by the dotted line. A circular plate is then cut slightly larger than this hole and after being brought to a red heat, it is bellied by the use of a hammer or a set of dies, so that it assumes the shape of a saucer and is called by many a “dished” patch. Some idea may be had of such a patch from Fig. 73.

(=107=) The patch is placed in the sheet with the concave side toward the operator and should be securely welded in place, adding as little metal for reinforcement as possible, but seeing to it that a perfect fusion is made between the patch and the sheet all the way through. As soon as the weld is complete the torch is played upon the high part of the patch, which is protruding, and as the weld cools off, sharp quick blows can be applied to the center of the patch, which should be kept in a heated condition until it is nearly flat. This will take care of any contraction that might set up and is a very good way of handling patches which do not exceed six or eight inches in diameter.

(=108=) A “corrugated” patch has been brought out more recently than the “dished” patch, and as its name would indicate, it has corrugations around at least three of its sides. While a “dished” patch is limited in its scope and cannot be applied to square holes unless the square holes be cut round, the “corrugated” patch knows absolutely no limits as to size or shape. While its preparation is probably more difficult, yet its purpose is the same, that is, to take care of the contraction which takes place in sheets of metal where heat has been introduced. To prepare a “corrugated” patch, a piece of metal which is somewhat larger than the hole is taken and the corrugation is made by placing two rods on one side and somewhat separated and between them on the other side another rod. With this section of the patch heated to a red heat, a drop hammer is played upon it and a corrugation effected. Or an easier method is by the use of specially prepared dies, which will turn out a patch in quick order. It must be remembered that while the patch shown in Fig. 74 is only for a very simple job, which is rectangular in shape, yet “L” shaped patches can be prepared and handled in the same manner. When the corrugation has been introduced into the patch, the latter is cut so that it will fit the hole, and it is tacked in position with the bellied sides out. The method used in applying a patch of this kind is to weld the uncorrugated side, then start up the corrugated side and weld for two or three inches, then play the torch upon the corrugation, adjoining the part welded, and slightly hammer to assist in the expansion of the same; then return to the weld, continuing it until the corrugation can again be played upon. By doing this, when finished the patch will be flat and no signs of the corrugations will be shown. While many patches of this nature are in use giving the very best service, the welder who looks upon the finished job cannot tell how it has been accomplished.

(=109=) While the methods here given seem only to apply to boiler work, they are not so restricted and can be applied to tanks and various vessels with success. However, when welding on tanks which have contained inflammable gases or gasoline the welder is cautioned to take every measure to safeguard himself, and while it is known that much work is being done on such jobs, it is not recommended and in fact quite the contrary. It is true that there are such methods as filling the containers with water; cleansing with live steam, and so forth, but the cautious man will refrain from working on these vessels even though such measures have been taken. Gasoline has a faculty of penetrating the pores of metallic surfaces, and although these vessels have been emptied and have remained so a matter of a year, the gasoline is still present to some extent, as is evidenced by the fact that as soon as heat is applied and the molecules of the metal are expanded, the gas is released in sufficient quantities to cause an explosion. This is not in one instance only, but in many, so it has been thought best to discourage any welding work on vessels which have contained gasoline at any time.

(=110=) While it is possible to weld cast iron on the vertical, by the use of carbon blocks and so forth, the same kind of work can be accomplished on steel with much ease, without the use of any blocks, or materials other than the filler-rod and the welding torch. There are two methods of handling vertical welds; welding from the top down, or starting from the bottom and working up. The former seems to be condemned by those who have never tried it, on account of the carelessness which is apt to be used on work of this kind. However, for the beginner, it is thought advisable to teach this method, as there are many places where it can be used advantageously. The metal at the top of the seam, such as a broken automobile frame, or the like, is brought to a molten state and held there, not only by the velocity of the flame, but also by the filler-rod, as is shown in Fig. 75. With the choosing of a tip of the correct size, the melted metal can be held under control with much ease, after a little practice, and it is allowed to descend as soon as the metal below it is in the proper shape for fusion. The filler-rod is added continually, for it is never lifted out of the molten metal, merely stirred a little from side to side as it descends. None of the melted metal is allowed to precede the flame, and at all times the operator can see whether the edges to be fused are at the right heat. As soon as the bottom is reached, the weld can again be gone over if it is not thought strong enough, and reinforced as much as desired. As soon as the operator is familiar with this method, he will find that much more speed can be developed, less filler-rod lost and less lapping done than by building up from the bottom.

(=111=) In welding over head there is a tendency on the part of most welders to avoid the use of enough heat to bring their metal to a molten state, for fear that it will drop upon them. It must be remembered that lack of heat means poor welds and that the metal must be in a molten condition whenever the weld is to be made. As soon as a little practice is given to this kind of work, the welder will see that the melted metal can assume some proportions without dropping off, despite its weight. It has probably been noticed that on “sweating” water tanks drops of water accumulate on the bottom of the tank and do not fall off. It is the same sort of problem in the case of melted steel. The adhesion of the molecules and the surface tension are the forces that keep the metal from dropping.