It has long been recognized that electric brass melting offers many theoretical advantages, such as saving of zinc, a high quality of product through freedom from contamination of the melt by oxygen and sulphur, the elimination of crucibles, ability to melt large charges, and better and safer working conditions. Commercial experience during the last few years has shown that all these advantages may be attained in practice. Various types of electric furnaces have been devised for brass melting, some of which are suitable only for a rather narrow range of foundry and rolling-mill conditions, or have certain drawbacks that limit their applicability.

In the experimental work of the Bureau of Mines on brass melting, which has been conducted during a period of more than five years, a rocking furnace has been evolved by Dr. Gillett and his associates, which appears fitted to a rather wider variety of conditions than most other furnaces. This furnace has been built in commercial size and submitted to commercial tests, and the results indicate that it not only reduces metal losses, avoids the use of graphite crucibles, and hence the need of ships for importing graphite from Ceylon, but is so economical in use of electric power that no more fuel is required. for brass melting, after conversion of the fuel energy into electricity, than if the fuel were used direct in a fuel-fired brass furnace. Not only does the use of the furnace show a large reduction in melting cost at present prices, but it also shows a saving over the melting cost at prewar prices.

Comparison of the cost of melting, on a 10-hour schedule, in the rocking electric furnace and in the coke-fired crucibles of the plant at which the tests were made show that the cost, per ton of charge, for electric power, interest, and depreciation, electrodes, linings, and the heating of ladles is about one-half of the cost, at present prices and present crucible life, of the single item of crucibles for coke fires. Hence under present conditions a huge saving is possible by electric melting. Under normal conditions the saving will be smaller but decided. With 24-hour operation the balance in favor of the electric furnace would be still larger.

The usefulness of such a furnace in the brass industry is evident, and this paper is published in the hope that it may stimulate the use, not only of the rocking furnace but of all other electric furnaces under conditions to which each is adapted, and hasten the savings to the brass melter and the conservation of metal to the country that electric furnaces make possible.

CHARLES L. PARSONS,

Chief Division of Mineral Technology.

MELTING BRASS IN A ROCKING ELECTRIC FURNACE.

By H. W. GILLETT and A. E. RHOADS.

INTRODUCTION.

In its study of methods for reducing metal losses in the nonferrous metal industry, the Bureau of Mines has conducted a long series of experiments on electric brass melting and collected much data on the experiments of others. Reports bearing on this work that have already been published by the Bureau of Mines are Bulletin 73, "Brass-furnace practice in the United States," and Bulletin 77, "The electric furnace in metallurgical work."

A comprehensive report describing the design and operation of all types of electric brass furnaces and showing their performance in experimental tests on a commercial scale is in course of preparation. However, commercial tests of several new and promising types of furnaces are still under way, the results of which should be included in any general discussion of the subject. For this reason it has seemed desirable to issue a preliminary bulletin giving the data on a type of furnace developed in one stage of the bureau's work.

OBJECT OF REPORT.

The object of this paper is to set forth in detail the possibilities. and limitations of a rocking electric brass furnace. The general problem of electric brass furnaces is discussed and various types of furnaces are compared only so far as is necessary for the purpose of this report. Information on such other furnaces as have found commercial use is obtainable from the makers of the various furnaces. Reference to some of the more important articles in scientific and technical publications, dealing with the general subject of electric brass melting and with the performances of various specific types of furnaces, is made herein in order that interested persons may pursue the subject further. VARYING CONDITIONS A MELTING FURNACE MAY MEET.

A brass furnace for brevity the term brass is here loosely used to include brass and bronze-may have to meet widely varying conditions, according to the work to be performed. A brass rolling

mill, in general, works with alloys of high zinc content, which are normally made up in large proportion from new metals, and such a mill can, and often does, operate on a 24-hour basis. The tonnage of any given alloy is usually large enough for separate furnaces to be used for melting different alloys. There is a possibility of utilizing furnaces of fairly large capacity in the rolling-mill industry.

Brass foundries vary in size and kind of output from the little jobbing shop, making small quantities of alloys of many different compositions, to the departments of huge manufacturing plants turning out a vast tonnage of a few standard compositions. The type of castings may vary from small intricate patterns, requiring very hot metal, to large castings that are best poured with rather cool metal. The work may be such that night molding is feasible, and operating 24 hours a day is desirable, or be such that operation is practicable only in the daytime. Depending on the nature of the plant and of the work, a furnace may melt the same alloy throughout the year, or may not make two consecutive heats on the same alloy. The alloys may vary from pure copper through bronze, red brass, leaded bearingmetals, half-yellow and half-red brass, yellow brass, and manganese bronze to brazing spelter, or from no zinc to 50 per cent zinc and no lead to 25 per cent or more lead.

Plants refining waste materials and scrap may have as wide a range of alloys as that given in the preceding paragraphs, and in addition their operation may be complicated by the use of very bulky and dirty materials.

Obviously, no single size or type of furnace, whether fuel-fired or electric, can satisfactorily meet all the various conditions encountered in nonferrous melting."

PRESENT NEED FOR ELECTRIC BRASS FURNACES.

Fuel-fired furnaces are divisable into several types, according to the kind of work that is to be done. The two chief classes, disregarding minor subdivisions, are crucible furnaces and open-flame oil furnaces. With the advent of an acute crucible shortage, coupled with a fivefold increase in price and a vast decrease in quality, the use of crucible furnaces has become more and more confined to the production of alloys high in zinc, such as rolling-mill brasses whereas the use of open-flame oil furnaces for making red brasses and bronzesalloys low in zinc-has markedly increased. That is, the metal losses in melting yellow brass in open-flame oil furnaces have in general been found to overbalance even the present high cost of crucibles. But even for red brass and bronze, many users still find it undesirable to replace crucible furnaces with types not using crucibles.

■Compare, Clamer, G. H., Melting brass in the induction furnace, Jour. Am. Inst. Metals, vol. 11, 1917. p. 381.

Zinc losses are high in melting yellow brass, even in crucibles, and there is need for furnaces that will eliminate crucible costs and reduce the zinc losses. In melting bronzes the need is for furnaces that will eliminate crucibles and, if possible, do away with the disadvantages of open-flame oil furnaces.

War conditions have greatly accentuated these needs, and have hastened the commercial development, trial, and application of various types of electric brass furnaces, for theoretically these furnaces seem capable of meeting the situation.

THEORETICAL ADVANTAGES OF ELECTRIC BRASS MELTING.

The theoretical advantages of electric brass melting are obvious. They are as follows:

1. Metal losses by oxidation and volatilization may be reduced, because electric furnaces may melt the charge in a nonoxidizing atmosphere and may be tightly closed to prevent volatilization losses.

2. As regards thermal efficiency, a greater proportion of the heat produced in an electric furnace may be utilized than of that in a fuelfired furnace.

3. The heat input and hence the temperature of the melt may be more closely controlled than in fuel-fired furnaces.

4. Storage and handling of fuel and ashes are eliminated.

5. Metal of "crucible quality" may be produced without the use of crucibles.

6. Working conditions as to health, comfort, and safety of the melters are better than with fuel-fired furnaces.

TYPES OF ELECTRIC BRASS FURNACES COMMERCIALLY TESTED.

General information on the various types of electric furnaces used in the metal industries can be found in the treatises by Stansfield ; by Rodenhauser and Schoenawö ; in Bulletin 67 4, and Bulletin 77 e of the Bureau of Mines; in the Transactions of the American Electrochemical Society, the Transactions of the Faraday Society, and in the issues of Metallurgical and Chemical Engineering.

Not every type of electric brass furnace meets every melting condition in the industry, nor does it necessarily have all the advan

• See Roeber, E. F., Manufacture of brass in the electric furnace, Electrochem, and Met. Ind., vol. 3, 1905, p. 4; Clamer, G. H., and Hering, C., The electric furnace for brass melting, Trans. Am. Inst. Metals, vol. 6, 1912, p. 95; Miller, D. D., The electric furnace for heating nonferrous metals, Jour. Am. Inst. Metals, vol. 11, 1917, p. 257.

Stansfield, A., The electric furnace, 1914, 415 pp.

c Rödenhauser, W., and Schoenawa, J., trans. by vom Baur, C. H., Electric furnaces in the iron and steel industry, 1917, 419 pp.

d Lyon, D. A., and Keeney, R. M., Electric furnaces for making iron and steel, Bull. 67, Bureau of Mines, 1914, 142 pp.

Lyon, D. A., Keeney, R. M., and Cullen, J. F., The electric furnace in metallurgical work, Bull.77, Bureau of Mines, 1914, 216 pp