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Discussion-The Effect of Sulphur
on Steel Castings
MR. McCAULEY - About six years ago when using coal as the fuel in our furnaces, we were getting from 0.042 to 0.07 in sulphur and were having checked castings. We went to the use of fuel oil about three years ago and frequently have had heats analyzing as low as 0.028 in phosphorus and sulphur, and we still have checks. We have been unable to prove to our own conclusion definitely that the difference in the sulphur makes any appreciable difference in the amount of checks in our castings.
THE CILAIRVAN, R. A. Bull.-I hope that the converter foundrymen who, perhaps especially during the war have been laboring under greater difficulties with respect to high sulphur content are able to submit more information as to tests than open-hearth founders, so that anybody can make his own deductions. In our own case, or in the case of others making open-hearth steel, of course, it isn't an extremely difficult matter to keep our sulphur down to the limit, but I know from a somewhat limited experience in converter practice that at times the extreme shortage of suitable coke made a very difficult problem for the converter foundries.
MR. E. F. CONE.-We all know that early in the war specifications had to be changed for steel castings to meet all the conditions and to get out the necessary product. I would like to ask Colonel White whether in his experience he has noted any practical observation as to whether the increased sulphur did any harm to castings that were in service; whether he ran across any data of that kind?
COL. A. E. WHUTE.—The very fact that the war ended as soon as it did has resulted in our being unable to obtain any real actual data with regard to the increased amount of sulphur in steel castings that went into ordnance work. So far as I have been able to get information from the records, the castings with the higher sulphur content were giving as good service as the castings which were held under 0.04 and 0.05 per cent, which was the case at the very beginning of hostilities.
COMMANDER RHOADES.- The U. S. S. GEORGIA had in 1909 fourteen 6-inch gun mounts or stands that broke in service and that had to be replaced. We microscoped them and looked them over, analyzed them, tested them, and they all ran high sulphur, around 0.06 and 0.07, but we never broke any that we made with 0.04 on the same job. They were large castings, weighing about 2000 pounds. I would like to ask Mr. White if in his experience he has observed that it is more difficult or less difficult to break up the dendritic structure and the bands and the ferrite in steel with a large amount of inclusions than one that has very little. In other words, we get a distribution of carbon in treatment. We can disseminate that carbon through the ferrite and get a uniform, nonbanded, nonferritic steel with low sulphur, easier than we can get it where we have large particles in the inclusions. We took a forging from a 5-inch gun at Bethlehem in 1914 in which the bands were the most remarkable I have ever seen. The streaks were uniformly white ferrite areas full of manganese sulphite inclusions in the center, and they couldn't treat that out. We knew it was sulphur from the color and sulphur prints, and from a piece a foot square we pulled 15 bars, none of which showed over 3 per cent elongation, although when we got off the streak we got up to 20 per cent elongation. COL. WHITE.--I trust
of you will misunderstand me with regard to the sulphur content. I have tried to make myself perfectly clear to the extent of stating that provided we had high grade castings and the castings were uniform with regard to the molding practice, annealing practice and design, that a low sulphur casting would then be preferable to a higher sulphur casting. The point that I tried to make, however, was that in my judgment the variations in designing and in molding practice and in annealing practice offset the variations that might be due to one or two hundredths of a per cent of sulphur. These streaks that we see in steel castings are termed, I presume, ghost lines, and I presume it is generally conceded that the ghost lines are due to the presence of phosphorus and that the phosphorus present in the steel in the manner in which it is, prevents the ferrite on annealing from distributing itself evenly throughout the casting, and that once we get that condition it is very difficult indeed to eliminate it. In fact, I don't know as any successful treatment has ever been devised where it can be eliminated. The only method whereby I know we can eliminate it is to quench the casting, but then if we draw it back the ghost lines return again. I don't know as it is usually felt that the ghost lines and streaks are due to sulphur. It is due to the phosphorus content, and, of course, we are not at this present time particularly concerned with the phosphorus content, although I realize that the two to a certain extent go hand in hand. The fact that there were streaks of manganese sulphite present in the ghost lines means, of course, that the metal was dirty, but at the same time I am not altogether convinced that the reason why those castings failed was due to high sulphur. The very fact that the castings had these ghost lines might indicate that this condition was very materially weakened through the influence of the phosphorus, and that failure possibly night be laid to phosphorus as much as to sulphur.
MR. LOCKE.--In connection with the matter of the effect of sulphur on castings from the producing standpoint, I collected data on some 1600 consecutive heats, involving about 35,000 tons of basic open hearth, in order to see if there was any appreciable effect of sulphur on the cracks. Our sulphur runs entirely between 0.020 and 0.030, and I found that the castings that cracked at 0.030 were about three times as many as the castings that cracked at 0.020, and the curve is very close to a straight line. I took a large number of heats in order to avoid any local conditions, such as molding or temperatures of the heat, and felt by doing so that I eliminated those things. Now, when it comes to phosphorus I found that the curve was practically horizontal. In other words, I could not see that there was any effect at all which probably could be expected, so that as a result I feel that apart from
the service of the castings after they are completed, the sulphur is very injurious from the producing standpoint.
Mr. C. S. Koch.—Regarding the matter of hot cracks, I believe that some foundrymen have more trouble the higher the sulphur, but this is a matter for each individual foundryman to determine for himself.
I think Professor White has been rather modest, in omitting from his paper much that he learned from the ordnance department. One point which he could have emphasized was that very frequently a list of 30 or 40 heats, which had been rejected by the inspection division of the ordnance department, by reason of their failure on physical tests, was referred to Washington for final decision. In the course of time, many such lists were compared with other similar lists from other foundries, and in the comparison of these, I do not believe it was very often found that high sulphur was the cause for their failure on the physical tests. In other words, there were many times when the sulphur and phosphorus were extremely low, and having failed in the physical tests as often as those which were high in sulphur and phosphorus. After a con, siderable number of these batches of rejected heats had been handled and compared, it was interesting to see that almost invariably the foundry was given the opportunity of reannealing, and in almost all cases the second lot of tests from the same heats would be returned as having satisfactorily passed the physical tests.
In fact, it is my opinion that if all of the cases of rejected heats were compiled, as well as all the data concerning reannealing, etc., it would have been almost invariably found that the cause of rejection, or failure to pass physical tests, was due to poor heat treatment.
Briefly, our whole trouble last year in the ordnance department was not analysis, not how the steel was made, or in what kind of a furnace, but was absolutely and almost entirely a matter of poor annealing equipment and poor annealing knowledge.
The Acid Electric Furnace Process
By L. B. LINDEMUTH, New York
In considering the electric furnace as a steelmaking instrument, whether acid or basic, we must always bear in mind that it offers the one method of manufacture by which we can obtain commercially either oxidizing or reducing conditions, and are therefore able to produce high quality steels at prices which are not prohibitive.
It will be necessary in this paper to assume that everyone is familiar with the metallurgy of the basic process, and it will, therefore, be mentioned only to point out differences or similarities between it and the acid process.
The electric furnace lined with sand, with the steel covered with silicious slag, varies from the basic-lined furnace with a basic slag, in that all of the constituents of the steel, except silicon, being in themselves basic, hold a different relation to the slag and lining, which are acid, than they do in a furnace where the bases are always in a very material majority. This difference in relationship affects not only the constituents of the steel but also influences the effect of the reducing conditions which make the electric furnace a superior steelmaking container.
How Phosphorus is Removed In the basic furnace, phosphorus is removed from the steel by producing an oxidized condition. Slag containing the phosphorus is then scraped out of the furnace and a second slag of a definite composition is made up and introduced in any desired volume. In the acid process, however, the removal of phosphorus which is itself an acid, is not possible in the presence of an
excess of silica, which is the stronger acid.
It is, therefore, unnecessary in the acid process to remove the slag provided it is possible to produce the necessary reduc