December 10, 1928
INDUSTRIAL
AND ENGINEERING
CHEMISTRY
9
Accomplishments of the High-Frequency Induction Furnace BY
DUDLEY
WILLCOX
AJAX ELECTROTHERMIC C O R P . , T R E N T O N , N.
J.
The high-frequency induction furnace has been on the market Among other u s e s , it has been found by the Babcock & Wilcox for about eleven years. I t has found its w a y into most of the Tube Co. t h a t t h e y can re-melt high-chromium steel scrap with important research laboratories of t h e world and into many very little l o s s o f chromium without adding t o the carbon con industrial establishments. It is hoped that the following sum tent. This is n o t possible in other types of electric or fuel-fired mary of its more important accomplishments will prove interest furnaces. ing and suggestive. The smaller furnaces have recently been used in t w o establish Approximately 6000 kilowatts of high-frequency power are ments for m a k i n g tungsten carbide and i t s alloys for cutting and being used t o energize some hundreds of high-frequency furnaces. drilling tools to take t h e place of diamonds. They range in size from a laboratory vacuum furnace about the At the plant o f Handy & Harman, Bridgeport, Conn., there size of a thimble t o a com is a 100-kilowatt, 1 1 0 0 mercial furnace holding a pound high-frequency in t o n of steel. T h e larger duction furnace for melt furnaces, with a capacity ing sterling silver scrap. of more than 100 pounds, A crucible life record has h a v e been in use for only r e c e n t l y been made in three or four years. melting 81 tons i n o n e The largest power in clay-graphite c r u c i b l e . stallation is that a t t h e Sterling silver, t o the ex A m e r i c a n B r a s s Co., tent of 10,900 avoirdupois Waterbury, Conn., where pounds, is regularly melted there are t w o 600-kilowatt in 8 hours and 50 minutes generators operating with this equipment. The twelve 100-kilowatt 750losses are negligible. The pound furnaces for meltcrucible which forms the i n g n i c k e l silver. T h e lining of the furnace can over-all efficiency is such be quickly replaced. The that about 6 pounds of whole equipment is said nickel silver per kilowattto be eminently satisfac hour are melted. These tory. furnaces melt about 140,Other commercial uses 0 0 0 pounds of nickel silver of the high-frequency in per day and, during 1926, duction furnace i n c l u d e melted about 56,000,000 T i l t i n g F u r n a c e s f o r t h e P r o d u c t i o n of High Q u a l i t y Steel I n g o t s , the making of fountainH e p p e n s t a l l F o r g e a n d K n i f e C o . , P i t t s b u r g h , Pa. pounds. They have the pen-point m e t a l s a n d advantage over t h e Ajaxdental alloys. The Gold smith Bros. Smelting & Refining Co., which have had one of W y a t t type induction furnace, which is used for most of the these furnaces f o r a number of years, melt platinum and iridium tonnage melting of t h e American Brass Co., that the high-fre by t h e use of a n Ajax-Northrup high-frequency electrical in quency furnaces can be emptied and used for a new mixture each duction furnace,, and make carbon-free melts at temperatures heat, whereas t h e Ajax-Wyatt furnaces require a residual charge well around 5OO0 ° F. The stirring action, on account of the in order not to ruin the lining. Therefore, the high-frequency electromagnetic force, thoroughly mixes and incorporates the furnaces are used for a large variety of mixtures of which com platinum a n d t h e iridium. There is no melting loss, hence paratively small quantities are required. there is a f u l l iridium c o n t e n t . T h e Williams Gold Refining Co., This installation is unique in that the furnaces are lifted to Buffalo, Ν . Υ., claim that their "radio furnace," wireless and t h e molds for pouring. Occasional heats of brass and bronze fireless, will boil platimum i n 30 seconds in a container that can are melted. There is no difficulty in melting with high-efficiency be held in hands during the operation. They believe that the metals of the highest and lowest electrical conductivity. Claygraphite crucibles with clay linings h a v e been used, but recent a t t e m p t s have been made to a d a p t carbon-free crucibles so as t o eliminate the possibility of contaminating t h e product with carbon. Another objective is t o use more kilowatts per pound in the furnace in order to melt more rapidly and therefore more efficiently. If more power is p u t into the furnaces when claygraphite crucibles are used, the crucible wall is so conductive t h a t it becomes m u c h hotter than the metal within, thus increas ing the radiation losses and decreasing the crucible life. The next most prominent installation of high-frequency fur naces is that of Edgar Alien & Co. Ltd., i n Sheffield, England. Their motor-generator equipment is rated a t 150 kilowatts out put and melts of about 600 pounds are regularly made. They have developed a new tool steel, known in England as Stag Major and in America as Imperial Major. They claim that this steel is several times more effective than the best high-speed tool steel previously produced. The over-all efficiency in a day's run is reported by t h e E d g a r Allen Co. as about 660 kilowatt-hours per short ton. I n their booklet, "Imperial Major," they state: T h e molten mass of high-grade pure base metal i s kept constantly on the move, owing to t h e complex electrical field in which t h e material exists. T h i s has t h e very i m p o r t a n t advantage of maintaining complete homogeneity throughout t h e mass. When such pure and expensive steel is being manufactured, it is essential t h a t t h e material should n o t b e contaminated in a n y w a y by sulfur, phos phorus, a n d other impurities which h a v e , in t h e past, been t h e deadly enemies of all steel makers. As the steel m a d e b y this n e w a n d novel process of melting does not come into contact w i t h a n y gases whatsoever (as compared with crucible melting), the extreme p u r i t y of the base metals used is pre served.
T w o furnaces of similar capacity for steel-melting are in use in this country, and three more are now being installed. A number of similar furnaces are being installed in Europe. One in particular, in France, is being built for handling 1-ton charges and will operate from a 650-kilowatt high-frequency generator. A furnace of similar capacity is being constructed in Germany for operation from a 300-kilowatt high-frequency generator. This furnace will be for refining rather than for melting.
Courtesy, Bell Telephone Laboratories, Inc. B e l l T e l e p h o n e L a b o r a t o r i e s , I n c . , New Y o r k , w h e r e P e r m a l l o y Was Discovered w i t h H i g h - F r e q u e n c y I n d u c t i o n F u r n a c e s
introduction of this furnace in t h e manufacture of dental golds marks the greatest step forward in dental metallurgy since den tistry has been practiced b y making better dental golds possible. T h e y also m a k e a g r e a t point of t h e lack of segregation and the homogeneity i n alloys produced b y the high-frequency induction furnace. I n a paper 1 presented before t h e fifty-fourth general meeting of t h e American Electrochemical Society the authors say: 1 Schuette: and Maier,'"The High-Frequency Induction F u r n a c e for Chem ical Preparations above 1 0 0 0 ° C , " paper presented a t the 1928 fall meeting of t h e American. Electrochemical Society, Charleston-Huntington, W . Va.
INDUSTRIAL
10
AND ENGINEERING
In reviewing the work done during the past year, there is one fact in connection with high-frequency induction furnace operation that becomes more striking with use and diversity of operations attempted. This is the reproducibility of results under the same experimental conditions. Records of certain repeated experiments a s kept during operation are almost exact duplicates a s to time interval and event. To an experienced operator, making a standardized run, the power indicator tells the whole story. The speed and ease of operation are other features that make this equipment of great value in high-temperature work, as also the applicability of the furnace t o different conditions imposed by experimental requirements.
T h i s is a bit of general praise which has been repeated manytimes by experimentalists in different parts of the world. One prominent metallurgist states that real alloy research work cannot be done without the aid of one of these furnaces. Another stated that the use of such a furnace saved about four thousand dollars in one year in operator's time on account of the extreme speed of melting and carrying on various laboratory heating experiments. A number of new alloys have been invented with t h e aid of the high-frequency induction furnace—notably, Permalloy and its brother, Mumetal, both used for loading submarine cables. Permalloy was discovered at the Bell Telephone Laboratories, Inc. (then the Western Electric Co. Research Laboratory), New York, N. V . Mumetal was developed by the Gutta Percha Co. in England. These metals have enabled the cable companies to build cables having over five times the speed of those previously used. "A" metal, used in audio-frequency transformers, w a s discovered in the high-frequency induction furnace. The General Electric Co. has developed in a high-frequency furnace a new alloy for use in integrating wattmeters. 2 T h e Bureau of Standards in Washington developed a new standard of purity for platinum with the high-frequency furnace. Edgar Allen's n e w steel, .o which reference has previously been made, should be included in the list. Laboratories of many of the larger steel companies have small alloy melting furnaces in which hundreds of melts are made t o determine the effect of changes in composition. Among these may be named the Midvale Co., Central Alloy Steel Corp., Taylor Wharton Iron & Steel Co., National Tube Co., Simonds Saw & Steel Co., Carnegie Steel Co., and Vanadium Alloy Steel Cc In the nonferrous industry the following firms are represented : the Crane Co., Ohio Brass Co., and Scovill Mfg. Co. Among the colleges represented are Yale, Harvard, Massachusetts Institute of Technology, Cornell, University of Illinois, University of Wisconsin, Princeton, Pennsylvania, Ohio State, and the University of South Dakota. A very interesting use for the high-frequency induction furnace has been developed by the Bureau of Standards 3 and t h e Union Carbide a n d Carbon Research Laboratories. This is a new method of determining occluded gases in metals. The idea i s to heat a few hundred grams of metal in a vacuum chamber within a high-frequency induction coil. The metal is heated for a n hour or more and all of t h e occluded gases come out and are measured in one or more analytical trains. Work of t h e same character has been done in England and in Germany and the results compared with those obtained at the Bureau of Standards. T h e s a m e sort of work has been done recently on a larger scale at4 t h e plant of the Westinghouse Electric & Mfg. Co. I n a paper presented at the spring meeting of the American Institute of Mining and Metallurgical Engineers, i n 1928, P. H. Brace and N. A . Zeigler described their work somewhat as follows: Whereas previous work along this line has been with a sample of metal of less than 1 cubic inch, we worked with from 4 to 13 pounds of metal and t h e ingots produced were large enough to provide adequate material for making determinations of magnetic and other physical properties. Temperatures above 1600° C. were attained in a chamber evacuated to 0.0002 mm. mercury. Studies have been made of the amounts of gases removable from electrolytic iron and from Armco ingot iron. I t was found that much less gas w a s removable from the Armco iron than from the electrolytic iron.
M r . Rentschler, of the Westinghouse Lamp Co., has done some exceedingly valuable work with a small high-frequency furnace of h i s own devising with which he has succeeded in reducing m e tallic thorium and other rare metals. Walter Rosenhain, 5 of the National Physical Laboratory, described t h e preparation of pure chromium and pure manganese. In t h e case of chromium, the metal which ordinarily contains some oxide is placed in a high-frequency induction furnace and treated while h o t with specially purified hydrogen. The manganese is produced b y distillation in a high-frequency vacuum furnace.
CHEMISTRY
News
Edition
In Germany, a paper 6 h a s been prepared based upon the work with a 35-kilowatt high-frequency induction furnace at t h e Kaiser Wilhelm Institute. Much valuable information was o b tained on t h e possibilities of reducing the carbon content i n molten metals by the rapid refining action in these furnaces o n account of electromagnetic stirring. During the past year, Horace C. Knerr, consulting engineer of Philadelphia, has published a paper o n his development of a n e w salt bath furnace.7 Mr. Knerr's work is directed toward t h e development of a heat-treating furnace f o r temperatures u p to 2400° or 2450° F. i n which the conducting container of t h e salt is heated b y high-frequency induction. The Radio Corporation of America uses the high-frequency induction furnace for driving the occluded gases out of the m e tallic parts of thermionic tubes during evacuation. High-frequency furnaces will find increasing employment i n research laboratories as more and more metallurgists, chemists, a n d ceramists learn of their possibilities. Their ease of control a n d the extremely high temperature which can be obtained i n t h e m under perfectly controlled conditions combine t o make them ideally suited to a wide variety of laboratory operations. The commercial use of these furnaces for ferrous, nonferrous, a n d precious metal melting and annealing, heat-treating, etc., seems destined to wide expansion. Steel practice is being rapi d l y altered b y the introduction of alloy steel a n d especially b y t h e introduction of stainless steel. It appears likely t h a t highfrequency induction furnaces will play an important part in t h i s change. Their rapid stirring and consequent refining action h a v e already been proved extremely valuable i n some steel processes. While it has not been used extensively for heating forgings a n d for other heating operations aside from melting, it seems likely t h a t such uses will be developed and will find wide application. 6 Franz Wever und Heinz Neuhauss, "Zur Kenntnis des HochfrequenzIuduktionsofens II—Ueber die Métallurgie des eisenlosen Induktionsofens." 7 Knerr, **A New Method for Heat-Treating High Speed Steel," paper presented at the meeting of the American Society for Steel Treating, Philadelphia, October 12, 1928.
E x a m i n a t i o n for J u n i o r C h e m i c a l Engineer The U n i t e d States Civil Service Commission announces a n open competitive examination for junior chemical engineer, applications for which must be on file with t h e Civil Service Commission, Washington, D . C , not later than January 22. The examination is to fill vacancies in various branches of t h e service throughout the United States. T h e entrance salary for positions in Washington, D . C , is S2000 a year, and approximately the same for field service. Higher salaried positions a r e filled through promotion. * The duties of t h e position will involve routine testing, i n spection of engineering material, drawing up plans for minor projects, preparing specifications for engineering material o r apparatus, performing field work, making computations, preparing maps, assisting in t h e conduct of experimental research tests, compiling reports, a n d handling technical correspondence. Competitors will be rated on general physics, mathematics, general engineering, and chemical engineering. Senior students will be admitted to the examination. Full information may b e obtained from t h e United States Civil Service Commission, Washington, D. C , or from t h e secretary of t h e United States Civil Service Board of Examiners a t the post office or customhouse in any city.
Junior Chemist Examination The U n i t e d States Civil Service Commission announces a n open competitive examination for junior chemist, applications for which m u s t be on file with the Civil Service Commission, Washington. D. C , not later than February 5. T h e examination is to fill vacancies in the federal classified service throughout t h e United States, including t h e departmental service at Washington, D. C. The entrance salary in the District of Columbia is $2000 a year, and will be approximately the s a m e in t h e field. The optional subjects are advanced inorganic chemistry, analytical chemistry, organic chemistry, and physical chemistry. Competitors will be rated on general chemistry and elementary physics, and t h e optional subject selectedFull information may b e obtained from t h e United States Civil Service Commission, Washington, D. C , or from t h e secretary of t h e United States Civil Service Board of Examiners a t the post office or customhouse in any city.
V. P . I. Has Course i n R a y o n M a n u f a c t u r e 2
Kinnard and H. T. Faus, paper presented at the midwinter convention of t h e American Institute of Electrical Engineers, New York, M. Y., Feb. 9-12, 1925. 8 Bur. Standards. Sci. Paper 457 (1922). * Inst. Metals Div., Am. Inst. Mining Met. Eng., February 20, 1928. 5 J.Iron Steel Inst. {London), 115, Pts. V, V I , and VII, May, 1927.
The Virginia Polytechnic Institute at Blacksburg, Va., is preparing t o install machinery for the manufacture of rayon. Seniors in t h e chemical engineering classes w i l l be offered a course in t h e production of this material. It i s believed t h a t V . P. I- will be the first American college to initiate a course i n rayon manufacture.
