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upon foundrymen at large that when it is necessary to weld, first consider the casting to be welded and then endeavor to secure a welding rod of an analysis similar to the casting. You will then find very little difficulty in salvaging castings and saving a great many dollars. This is particularly true in welding brass or bronze castings which may have to be polished and will show a different color at the weld.

Welding Monel Metal

A great many foundrymen have experienced difficulty in welding Monel-metal castings. Monel-metal castings are really not any harder to weld than the ordinary iron castings if the proper procedure is followed. The analysis of Monel metal shows a large nickel content and a nickel casting cannot be welded without preheating. On account of the combination of copper with the nickel in Monel metal it is easy to see that both must be brought to a rather high preheating temperature, say 1600 degrees Fahr., before the weld is attempted. After the casting is welded it should be brought again to approximately 1500 degrees and placed in hydrated lime in order to prevent any air getting access to it. Now this same principle applies to practically every type of casting.

The average foundryman will tell you that when the weld was made the casting looked first rate but 10 minutes afterward it was all cracked. The reason for this is that proper care was not taken with the casting after the weld was made. The casting should have been allowed to cool slowly and hydrated lime is the best substance that the writer is acquainted with for cooling castings slowly.

Discussion-Welding of Castings

MR. ROBERT E. KINKEAD.-The welding of any casting of gray iron whose failure would bring death and destruction should not be done by the electric process. In order to accomplish fusion, it is necessary to melt the cast iron. Now if there is a considerable mass of metal back of the line of fusion which is cold, it is quite evident that that small area or small volume of metal which was melted to accomplish fusion will be suddenly chilled, and that chilled iron has the characteristic of all chilled iron: it is hard and brittle. That is on the cast iron side of the line of fusion. On the steel side of the line of fusion, the steel absorbs a certain amount of free carbon in the cast iron; the result is that you have got a thin layer of high carbon steel. Such a junction (you may call one side cast iron and the other side steel) is not reliable. Any jar or dynamic stress is apt to pull the steel out of the cast iron because that chilled iron will not stand any dynamic stress. Now the way we get around that fundamental defect in the practice in repair work is through the application of steel studs along the line of the weld. Some people rely on a tensile strength of 5000 pounds per square inch of area due to that fusion between the steel and the gray iron; then, by introducing studs and welding across the studs on either side of the crack to get an additional strength due to the shearing strength of the studs and assume that they get up to 15,000 pounds per square inch tensile strength in the weld constructed in that manner. While on a great many gray iron castings, owing to the great factor of safety used in their design, such a job is entirely satisfactory.

In regard to the use of a flux, you can use any kind of a flux or welding compound or anything else, but the resultant hardening of cast iron under sudden cooling is something that cannot be affected by the introduction of any foreign substance, so far as I know, so that a flux is entirely useless.

PROFESSOR A. S. KINSEY.-In regard to the question of flux, is it not true that we use a flux in order to lower the temperature of the oxide of cast iron so that we can get it out of the way and reach the pure metal and make proper fusion? If we try to weld cast iron without attempting to remove the oxides, the fusion will not be a good one, and there will be porosity and weakness at the joints. The electric arc process uses a flux in the form of a coated metal electrode for steel welding, with that same thought in mind. I cannot quite see how a good weld can be made in an iron casting with steel as a filler rod without some attempt being made to eliminate the oxide. The fact that the arc is hot enough to melt the oxides does not necessarily mean that the weld will be a good one, because the oxides will melt in with the pure iron and leave a porous, hard weld.

In paragraph 3, page 494, the first sentence reads, "The attractive feature of this class of work is that it may be accomplished without preheating the casting" (referring to the welding of gray iron). In the fifth paragraph it is recommended that the operator should hesitate in his welding, taking only about 20 per cent of the time for each operation, in order to permit the heat to be distributed throughout the locality of the weld. I would like to ask if that would not mean preheating in order to avoid shrinkage cracks as the result of the distribution of the heat throughout the casting?

MR. KINKEAD.-The application of the metal electrode without preheating is an effort to do the work cheaper than it can be done by the oxyacetylene or with the carbon arc. If we preheat the casting, we can use either the gas process or the carbon electrode process and fill in cast iron. The job obtained following that practice will be better when it is properly done than if the job is done with the steel electrode, metal electrode process, because you are filling in the same kind of metal, probably a metal of higher grade than the metal of the original cast iron. But such a practice is quite expensive, and in pursuing this practice of using the metal electrode, we are trying to do the same job at enormously lower cost. There are some castings which have been repaired by the metal electrode process

without preheating which, had they been repaired by preheating and welding with the carbon arc or gas, would have been done at a prohibitive cost. We are dealing with an economic proposition rather than a technical one.

In regard to the use of flux, the best answer that I know of is to observe the conditions and see the character of the line of fusion obtained, using ordinary bare wire. It is not true that in the metal electrode welding we use flux. Probably not 5 per cent of the metal electrode welding now performed in the country is being done with covered electrodes. The temperature is so high that the oxide gets clear to the top in a very short length of time. We do get some oxide in the metal; we get the metal oxidized in steel welding. Under commercial conditions, even with the best covered electrodes we are able to obtain we get oxidation and we do not get an appreciable degree of ductility in the metal deposited in the weld, so that the use of flux up to the present time has not been practical. It has been an experimental proposition, and the use of flux has not justified itself on economic grounds.

MR. W. D. SPERRY.-Is it not true that cast iron must be welded quickly?

PROFESSOR KINSEY.-I believe that it is not true that any metal should be welded in the quickest possible time. From a metallurgical standpoint that is not the correct way to weld. This applies to cast iron and to steel, which it is sometimes claimed should be welded as quickly as possible to avoid expansion. We know that the result of welding under conditions. where the speed is too fast is a crystalized brittle' joint. We also know that where it is absolutely necessary to prevent expansion and the resultant shrinkage of a piece of steel, the arc weld will heat up the metal fast enough to accomplish a fusion of the joints without such expansion.

THE CHAIRMAN, MR. W. R. BEAN.-For the past year and a half we have been conducting experiments in the welding of standard test bars as produced in malleable iron. We have succeeded in getting within 10 per cent of the original tensile strength of the metal in a 5-inch diameter bar, welded in malleable iron. Tests have shown just under 45 pounds on a

companion bar showing about 40,000 or 50,000 pounds as produced. We have carried on the process under both the electric and the oxyacetylene method. We do not use, in the bars. which have given us the best results, the steel rod, but use a rod of our own make which is essentially the composition of the original material, allowing something for oxidation. We weld in the hard iron state and in the annealed state, and in malleable, putting the castings through the regular process. The reason a weld cannot be produced in malleable that is machinable except in the very outer surface, is this: The extreme outer surface of the malleable castings is essentially that of a low carbon steel, as far as carbon content is concerned, and that is the controlling factor. If your sections were uniform throughout, you could weld without difficulty. The center is a high carbon content producing the carbon content of gray cast iron. When you heat that by any welding process, to the fusion temperature, the carbon which is in the graphitic or tempered form, goes back into the solution with the iron and you get, for an area surrounding the point of weld, a composition essentially that of the original white iron casting. Therefore, if an annealed casting is welded where strength is of any importance or where machining qualities are involved, it must at the same time be reannealed, else you have not a safe proposition. The danger is still there, in this, that unless extreme care is used, you get an oxidation which may, even though you have had the proper welding material, give you a weld that is not machinable and that is hard and brittle. A break cannot be welded unless it is burned down or V'd so that you can fill up to the original surface. If that is done, you can weld, but I am not willing to suggest to any one in the malleable iron industry that they weld castings and send them to their customers, except that the welding be done in parts where no particular strain comes in service. It is practical to do it and it is being done by a very considerable number of malleable foundries. There are two fields for welding, in my judgment; one in castings which are commercially produced, and the other in the repair of parts broken by accident or otherwise.

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