The Iron Age 1940-05-30: Vol 45 Iss 22

Editorial Technical Articles Double Boiler for Melting Zinc............... Pickling and Polishing Metals Cooling System for Quenching Progress Rides the Coattails Obsolescence.......... What's New Motors and Feature Reports News and Market Reports Iron and Steel Institute Meets District Market Gear Association .... Machine Tool Activity........ National Metal Trades Non-Ferrous Metal Market... Warehouse Convention Scrap Market and Prices..... MAY 30, 1940 Exports and Imports. Construction Steel Personals and Obituaries Iron and Steel Prices........ Metal Working Activity Pig Iron, Ferroalloys Prices... Comparison Prices Warehouse Prices VOL. 145 NO. Summary the Week Sales Possibilities BAUR Vice-President and General Manager Managing Editor News Editor Editor Machinery Editor Art Editor Editor Emeritus Associate Editors DIX, Manager Reader Service Owned and Published (Incorporated) Washington Editors Advertising Staff MOFFETT JAMES Publication Office Editorial and Union Cleveland Chestnut and Séth Sts. Executive Offices Resident District Editors Bid Philadelphia, 239 West 39th St.. Hottenstein, Otis Bldg., Chicago U.S.A. ittsburgh Chicag Leonard, 239 39th New York JAMES SHERMAN Peir Lewis, .7310 Woodward Ave., Detroit Cleveland Detroit Ober, 239 39th New York JR, OBE >. McINTOSH OR 9 Hartfor Conn Buffalo Cincinnat Don Avenue, Long GEORGE GRIFFITHS Vice-President HUGH SHARP CLYDE ENNIS mber Bure Circulations BAUR, Vice-President Birmir Member Business Papers SANDERSON ROY EDMONDS shed every Thursday. tion Price: JOHN BLAIR MOFFETT, Secretary Toronto, St. Louis ssions, Cuba JULIAN CHASE, THOMAS KANE $6.00: Canada, $8.50: Foreign, $12.00 year. i i i “deg Copyri + er Ay 4 be 4 The top illustration shows one two complete units designed and installed Mahon for the Gibson Refrigerator Company, Greenville, Michigan. The above show the entrance Mahon Filter Spray the same insiallation. This Finishing System was designed for the applica- tion Synthetic and has been tion for approximately two yeors. Above: Mahon Down-Draught roughly Engineered = 4 Meet YOUR Exacting Requirements Production finishing today has reached point where proper equipment becomes more and more essential—particularly industries where product finish vital sales factor. That why many manufacturers are now turning Mahon for complete new finishing systems they know that finishing system must thoroughly engineered specific job, and that must properly balanced and coordinated operate efficiently and economically. Mahon engineers have designed and installed hundreds finishing systems industries where finishing consti- tutes major production operation through constant research and development, this highly specialized field, they have successfully solved many complex finishing problems—their prac- tical experience, and their thorough knowledge modern finishing methods, fits them produce better planned, better engineered finishing system for your finishing system that will show you greater savings and more economical op- erate over period time. you are contemplating new finish- ing system, any unit thereof, call Mahon engineer now— consultation will not place you under any obligation. Write today. THE MAHON COMPANY DETROIT— CHICAGO Designers and Manufacturers Complete Finishing Systems, Metal Cleaning Machines, Rust Proofing Machines, Hydro-Filter Spray Booths, Ovens All Types, Filtered Air Supply Units, Hydro-Foam Dust Collectors and many other Units Special Production Equipment. Hydro-Filter Spray Booth showing filtered air supply. 14—-THE IRON AGE, May 30, a Horse these days apprehension and confusion, first thoughts are not usually best thoughts. That has been pathetically demonstrated recent events England and France. England, faced with succession diplomatic and military failures, found long last that the umbrella was not potent the sword. England decided swap horses midstream. France, faced with succession military defeats and admitting lack adequate preparation, also found necessary swap horses midstream. Maybe this horse swapping the part England and France has been too late and maybe not. History will answer this question. But least clearly evident that there nothing gained sticking sway-backed and spavined nag when the time comes places. make success our defense program, will because capital and labor pull together team. American industry these mechanized days essential get capital and labor pull together team, need experienced drivers. That the first and fundamental requirement. MAY 30, 1940 say that neither capital nor labor has confidence the ability those ESTABLISHED now the seat deliver the goods the designated destination. First and foremost preparedness program the position Sec- retary War. cannot properly filled Charlie McCarthy who unknown industry, unknowing and who does not even broadcast. Assistant Secretary War Louis Johnson the man for that job. has been doing the work, give him the title. Under him should least three assistant secretaries district managers charge specific activity such aircraft, mechanized equipment and essential materials. Each man should the caliber command public respect the basis past performance. And most particularly, they should men who command the respect labor, for American labor has more stake the preservation Democracy than any other group this country. might good thing have William Green and John Lewis suggest names outstand- ing industrialists for these jobs. They know who, who and who do. little horse trading this time may get across the stream before the water gets too high. i 3 | ‘om = ine C C O | ra 4 FS | ! — Opportunity for Fabricators Increase Sales! Manufacturers machine tools long ago adopted the sound selling practice proving their customers that machine tools new designs make better prod- ucts lower costs. The reward for these alert and untiring sales efforts has been vastly greater volume machine tool orders. Fabricators structural steel can take that page from the machine tool industry’s “success book.” Never before have fabricators had many good including low interest rates, with which get new business. Thousands manufacturing plants are doing business buildings which are handicap efficient manufacturing. Today the industrial architect, con- tractor and fabricator far more than simply build. They can make structures that are really “tools” for manufacturing, tools that will give the manufacturer advantage lowered costs and higher Yet, thousands manufacturers are not fully aware these facts. Many are struggling along outmoded structures that are definite business handicap. Fabri- cators who will step out and sell structures which better products can made lower cost will new realm opportunity. Inland engineers are espe- cially equipped many years practical experience give fabricators valuable engineering assistance. free for the asking. INLAND STEEL CO. Dearborn Street, Chicago Sales Offices: Milwaukee, Detroit, St. Paul, St. Louis, Kansas City, Cincinnati STRUCTURALS PILING RAILS TRACK ACCESSORIES REINFORCING BARS the great majority uses metals the alloy chosen and its heat treatment and methods fabrication are ordered produce mechanical properties which are more less form throughout the piece. there are certain service requirements which indicate the need for surface—adapted resist wear, abra- sion, penetration, other body metal which does the accompanying which therefore will withstand shock stresses without danger failure. few examples such requirements are found ball and roller bearings, gear teeth for exacting duty, and cam shafts and piston pins motors. These examples serve merely suggest others the manifold ap- plications surface hardening gineering Since the majority such require ments are noted where simple alloy steels are emploved, the necessary gradation properties may met one three commonly (1) Case carburization, the body the piece being low steel Which will retain resisting qualities even after quench- ing treatments while the surface layer, suitable depth, converted into high carbon steel, responsive heat MAHIN Department Metallurgy, University Notre Dame, Notre Dame, Ind. ° EREIN, the author consid- ers the entire field case carburization steel de- tail, correlating all informa- tion easily understood form. this the first two parts, attention directed marily pack carburizing —the reactions involved, the sources carbon, the energizers, the influence temperature, time, etc. treatment: (2) nitriding, the surface laver hardened the tion nitrogen; (3) which combination these treat- ments, both carbon and nitrogen being introduced into the surface the low carbon body the piece. certain cases surface hardening metal, such chromium, treatment limited application and emploved, all, for other reasons than the mere production surface hardness. hardening and induction hardening are practiced for similar purposes but these proc- esses are outside the scope this article. Conversion the surface low carbon steel into high carbon steel usually discussed under the general headings “pack” carburiz- ing, gas carburizing, and liquid car- burizing. the last all these are gas carburizing processes, since only gas which carbon one the essential elements form the hardening action. Pack Carburizing Pack carburizing really adapta- tion, purpose, the old “cementation” making steel. The cementation making tool steels from wrought iron (sometimes followed crucible melt- ing) furnished practically all the commercial steel any important in- dustrial use, prior the introduction the Bessemer process. carrying out this process, puddled wrought iron fractory boxes and heated for varying periods, running into several days, iron what today designated the gamma this form iron capable holding carbon solid solution and the bars quired carbon from the charcoal. This action naturally only the surface the bars and, carbon mi- grated toward the axis the bars, gradient carbon concentration was THE IRON AGE, May 30, q us | man ° ° ° ‘ | | > at a] gas mixture, per cent S 900 950 1100 1150 Temperature 1652 1742 2012 2102 Temperoture, deg. relations the two oxides carbon (CO and CO.) the presence solid carbon. the result. This concentration was highest the surface and lowest the axis bar. This condition variable carbon content was undesirable for ished piece steel and was rem- Aus te nite + fe ppsy to Ferrite / Carbon, per cent Fic. phase diagram. edied either repeated piling and rolling the bars forging tempera- tures, melting the cut bars crucibles. The last method produced crucible steels uniform carbon con- tent. 4 cement te IRON AGE, May 30, 1940 The object case carburizing the same that the process manu- facture cementation steel one re- spect that carbon imparted the low carbon base but quite differ- ent another, its specific purpose be- hardenable high carbon while the body, left its original low carbon state. The and physical reactions case carbu rizing and the manufacture ce- mentation steel are identical. Pack Carburizing Reactions the reactions ring during the operations pack carburizing appear quite simple. The steel piece case carburized packed metal container rounded carbon-containing mate- rial granular form. The cover luted such manner prevent excessive interchange box gases and air, the assembly then brought the desired temperature, and there maintained until case predeter- mined depth and character produced. When heated air pure oxy- gen carbon forms both carbon monox- ide and carbon dioxide, represented the formulas and CO: respectively. The first will carbon iron steel when sufficiently high tem- perature, the second will remove car- bon from steel. The first therefore carburizer, the second carburizing box, the oxygen the air which bathes the steel piece, and the carburizer granules, begins combine with carbon the temperature rises. very slowly first but more rapidly higher temperatures. Both oxides carbon are formed and the ratio the concentrations these two gases function temperature. The equlibrium concentrations trated Fig. which the per cent carbon monoxide the gas mixture Considering the opposing actions the two oxides carbon, just stated, may seen that the matter car- burizing temperature one great importance. Successful carburization could not expected occur within the lower temperature ranges, where the carburizing effect carbon noxide nearly counteracted the decarburizing effect carbon dioxide. (Carburizing temperature will also considered later related the migration rate carbon the steel. With the understanding that carbon 100 994 996 998 | 723° 200° Ferrite monoxide the active carburizing agent, the various stages the proc- ess may indicated follows: lower temperature ranges. (2) CO: the tem- perature rises. This reversible re- action, coming equilibrium the two gases relative concentrations which depend upon the temperature. same reversible change, written the opposite direction. Continued zation depends upon keeping the equi- librium reactions (2) and (5) shifted the right, the space sur- rounding the steel, and the left reactions (3) and (4), within the body the steel. The first condition obtained having large excess carbon the box and keeping the temperature high; the sec- start the process and further supply losses should occur. Carbon Sources From the preceding discussion might appear that practically any mate- rial which would furnish adequate supply elementary carbon would serve practical carburizer. Theo- retically this true and such materials the case: (Left) Hypereutectoid; pearlite and primary cementite. Eutectoid band; pearlite. (Right) Part gradation zone; pearlite and primary ferrite. diameters. the steel, the iron being now the gamma modification, capable holding carbon solid solution. this solution: (4) 2CO Again this reaction, which pro- ceeds toward the right because the return carbon dioxide the surrounding space and because the ele- mentary carbon remains the solid solution, austenite, and continues diffuse into the steel, away from the sur face. The carbon dioxide formed reac- tion (4) reacts with carbon the car- burizing Reactions (2) and (5) are seen the same, and reaction (4) the ond continued diffusion carbon solid solution, away from the sur- face and toward the core the piece, and return carbon dioxide the surrounding space. The entire process, once started formation sufficiently high concen- continuous one, long adequate supply solid carbon available and until the iron has reached condition saturation with carbon. practice the end never reached either these causes. large excess car- burizing compound provided and the process stopped soon carbon has diffused far enough into the steel produce case small depth. The quantity air ordinarily inclosed with the granular carburizer sufficient charcoal from hard soft woods from corn cobs, coke from coal, coal tar petroleum, sugar char, and many other substances, will do. Aside from the item ex- cessive cost, some such carbon sources are ruled out because found that they are too slow action, because they contain excessive amounts injurious impurities, such sulphur, cause permits ready reaction car- bon with oxygen the beginning, and with carbon dioxide the process con- tinues, and because makes possible ready movement and circulation the gases the carburizing box. must remembered that the continuous cycle reactions (4) and (5) depends THE IRON AGE, May 30, | gi for speed upon ready diffusion car- bon monoxide the surface the steel and carbon dioxide from the steel surface solid carbon the surrounding space. Even given form carbon obviously porous slow carburizer, apparently because the surface condition the carbon particle. This true lamp black, graphite, and most forms car- bon derived from carbons such manner form soot. Many commercial carburizers are available the trade, for use the production plant. and offered for sale reliable manufac- turers, most the various brands are dependable properly selected with regard the type steel car- burized and the character case de- sired. the manufacture these special carburizers control tions carbon quality, size and porosity granules pellets, and the nature and quantity “energizer” paragraphs following) are given attention. the manufacturer the carburizer provided with adequate information with regard the nature the steel stock, the service which the fabricated part perform, and the depth and character case de- sired, his advice regarding the car- burizer selected and the condi- tions under which used should valued and should lowed, except variations indicated practical use the plant may sug- gest themselves. Energizers While carburization may effected the earlier manufacture cementation steel, for case carburization the action slow for practical order accelerate the absorption carbon 'This is the view of energizing action Which has long been held and which the writer believes is correct. Other suggested explanations have been offered Ragatz and Kowalke (Metals and Alloys, Vol. pp. 290 and 1931), Enos (Transactions, American Society for Steel Treating, Vol. 27, 1932). 20—THE IRON AGE, May 30, 1940 the steel piece various materials known under the general are always incorporated with the carbon base the ing “compound.” The usual manufac- turing procedure includes grinding the carbon base, mixing with the appropriate amount energizing com- pounds and with binder, such cheap molasses, forming into pellets granules proper size, and baking. The action the energizer accel- erating the absorption carbon steel not difficult understand. most invariably the selected energizer metal carbonate which will slowly decompose the carburizing tempera- ture, yielding carbon dioxide. This illustrated the behavior barium carbonate, compound: with solid carbon, producing the active carburizing energizing gas, carbon monoxide, thus enriching the gas mixture this essential compound: order understand the action energizers and the need for such celerating agents necessary re- call the fact that the air inclosed the carburizing only about per cent, volume, gen, the remainder being active nitrogen. The equilibrium curve, shows that 700 deg. (1292 deg. F.) mixture the two oxides carbon, contact with solid carbon, would contain about per cent carbon monoxide, this concen- tration rising 98.4 per cent 950 deg. (1742 deg. But this far from representing the true concen- tration the active carbon for three reasons: (1) The original air the box has its oxygen diluted with per cent inactive nitrogen and this reduces the concentration oxide—that can (2) ther- mal expansion the gases the car- burizing box, the temperature rises the carburization range, causes loss about three-fourths the original volume. The these two reductions that the carburizing temperature only about 5.5 per cent the orginal air inclosed the box represented oxides carbon; (3) the formation carbon monoxide from ogygen and carbon re- sults the production double the volume the original causes further expulsion gas from the box and further reduction the effective amount carbon This surprisingly small carbon monoxide the box can effect only slow carburizing action. The energizer acts form this necessary gas heating progresses and this fairly cheap source carbon mon- oxide may used quantity cient drive much the original gas mixture from the box, through ices the this amounts carbon monoxide nearly pure gas, serves speed the reactions car- burization practical way. order any practical ser- vice carburizing, energizer must not decompose and evolve its carbon dioxide too rapidly within too low later backward diffusion atmospher- nitrogen through leaks the luting would again dilute the Neither energizer too difficult decompose, thus being too slow action prevent dilution backward-diffusing nitrogen from out- sometimes used, containing fairly easily decomposed will cause early formation carbon dioxide and thus expel much atmospheric nitrogen from also more stable carbonate which will slowly evolve carbon dioxide with maintain this evolution over siderable time. standpoint may understood why calcium car- Its decomposition occurs early heating process and, while serve purpose expelling air Composite photomicrograph taken across | | j the case carburized steel. from the box and replacing this air with carbon dioxide which later forms the monoxide, its action diminishes and becomes nearly negligible the later stages the long heating. the other hand, barium carbonate sodi- carbonate continues yield carbon dioxide over fairly long periods time, and these carbonates practice considerable extent. Carburizing Boxes material for carburizing time the steel becomes burized from the inside, and decarburized the outside. Em- from within and gradual scaling and destruction from without limit the useful life steel boxes. Cast alloys nickel and chromium are the most satisfactory materials for box construction. The first cost relatively high but long life and free- dom from troubles more than compen- sate for this disadvantage. These alloys satisfactorily resist oxidation carburizing temperatures and they not themselves absorb carbon. Steels for Carburizing treatments are designed only vide hard surface, maximum wear resistance, the mass, body, the piece must such composition will furnish the mass strength required for service. Plain carbon steels hav- ing carbon low 0.15 per cent, high 0.4 per cent, are used. Prop- erly chosen steels will provide greater mass strength and for this pur- pose chromium, nickel, molybdenum, used. Some the alloying elements notably chromium and vanadium also promote fine grain structure. Character Case Two factors are important case determined such consider- ations the required mass strength the case and the amount wear The necessary depth normally expected. The depth case required different types ser- vice may anywhere between few even more special instances. Ex- tremely shallow cases only for superficial resistance light wear. They are more often formed cyaniding than box carburizing. The carbon distribution the case quite another matter. The carbon gradient—the line representing carbon per cent plotted against case depth may quite steep, high carbon the surface running rather abruptly the low carbon core, may have small slope. With carbon gradient further item consider- the actual hardness required the surface. This determines the opti- mum carbon content for the surface layer because the surface hardness after thermal treatment varies more less directly with the per cent carbon the Assuming given steel composition and given commercial carburizer, the character case will determined the temperature and the time the carburizing temperature. tors will considered separately. Carburizing Temperature Earlier notice was given the fact that the gas mixture the car- box the ratio carbon mon- oxide, the active carburizing agent, total gas volume increases with rising temperature. This fact alone points more rapid carburizing higher tem- peratures, the law mass action ap- here other chemical and physical reactions. This would indicate steep carbon gradient the case, carbon absorption tending build high carbon concentration near the surface. But higher temperatures also cause more rapid carbon migration toward the core, thus nullifying the absorption factor certain extent. Assuming fairly efficient combination carbon base and energizer, experience shows that higher temperature affects the absorption factor greater exent than does the migration factor. Carburizing Time Having selected carburizing tem- perature high may employed without building excessive. carbon concentration near the surface, the time factor will determined the case depth required. commercial practice the time full carburizing temperature may anywhere from more—according temperature and case depth wanted. already noted, lower temperatures call for longer time for the production case specified depth. these influences might appear somewhat complex matter, this may perhaps simplified the fol- lowing summary (1) NATURE CARBON BASE AND SIZE AND POROSITY GRANULES. The rate reaction with oxygen with carbon dioxide directly related the rate absorption. (2) NATURE AND QUANTITY EN- ERGIZER. Affect the rate carbon ab- sorption directly, they serve in- crease the effective concentration carbon monoxide. (3) RATE ABSORPTION CAR- BON. Higher rates tend build higher concentration carbon the surface layer the steel. (4) TEMPERATURE Higher both rate carbon absorption and rate carbon migration, but the first more marked way than the last. The temperature effect carbon ab- sorption works through carbon monoxide concentration the box, and (2) higher reaction rate the iron surface and the carburizer granules. the matter carbon mi- gration the temperature naturally has with atomic mobility and the dif- fusion rate carbon after has en- tered the steel. (5) THE CARBON GRADI- ENT. Considering the effects noted THE IRON AGE, May 30, (4), follows that steep carbon gradient the core will promoted use high carburizing tempera- tures, more gradual slope lower temperatures. the other hand, longer time periods the carburizing temperature will required for given case depth than higher tem- peratures are employed. The question may then asked: How the man charge produc- tion going determine all these factors and the summation their ef- fects? The answer that should not expect so, except quali- tative manner and checked his experimental results. This does not make the case hopeless may first appear. The superintendent production should possess knowledge principles, which will enable him make close guess requirements procedure new job. must able analyze his results and make intelligently con- sidered modifications practice, in- dicated these results. But should feel also that can assume expert knowledge the part the organiza- tion the carburizer manufacture, that advice from the manufacturer may safe for starter new work. illogical and sense- less order simply compound” for the farmer order mixed fertilizer” for his soil, know- ing nothing the qualities his ma- terial. for the householder, survey- ing the years accumulation pre- scriptions and nostrums his family medicine cabinet, decide that dumps them all into one large bottle will have mixture which may relied upon for the curing almost any family ill. Fortunately true that reputable manufacturers carburizers, and other heat treating specialties, have their organizations experts who study their special fields, and whose advice reliable where new require- ments are considered. Per Cent Carbon Surface Every carburized piece sub- jected thermal treatment, which designed accomplish two results: (1) produce maximum hardness the surface, and (2) accomplish the maximum grain refinement case and core, fine grain structure be- ing intimately related mechanical strength. Considering both time and temper- ature factors, any desired carbon con- centration may obtained the sur- face, perhaps 1.2 per cent. Patent No. 1,921,367. 22—THE IRON AGE, May 30, well recognized that higher carbon content results higher hardenability, might assumed that the maximum carbon content the surface layer would most desirable. This not necessarily true. Any steel having carbon content greater than approximately cent known and after slow cooling (the normal proce- dure box treatment) its microstruc- ture will composed primary ce- mentite, very hard and brittle phase, section) surrounding pearlite grains. present larger amount, with much higher carbon content, primary cementite may occur also (needles, crossing pearlite grains. approximately 0.85 per cent carbon the steel and after slow cooling its microstructure shows that all And the carbon content lower than this figure, the “gradation zone” and the core, the steel and microsection both pearlite and primary ferrite appear, ferrite being the softest and weakest phase any steel. All these structures are shown taken across the case of-an excessively carburized low carbon steel, cooled the carburizing box. Such carbu- rized and slowly cooled steel its annealed condition and requires reheating and quenching treatment for both hardening and grain refinement. accordance with the iron-carbon phase diagram (Fig. cooled steel must heated into the austenitic temperature quenching, order that all pearlite may converted into austenite and that this austenite may re-absorb any even though the iron-carbon diagram does indicate the solubility cement- ite any specified temperature, the time element enters because cementite rather sluggish the matter re- dissolving. the steel has been heav- ily carburized, with much hyper- eutectoid outer zone and fairly heavy cementite network present, the total re- absorption this cementite quire long heating with consequent grain growth. insufficient time given the high temperature and not all the cementite has been re- dissolved, this hard and brittle phase will remain envelopes cells. This likely cause (crack- ing) the case, service. For these reasons usually desir- able that any hypereutectoid outer zone shall limited small depth. the cellular envelopes cementite are quite thin they will more read- ily re-absorbed into the austenite, and the hypereutectoid zone shallow most will removed during the finish grinding which after carburization and heat treatment. Carbon Gradient Slope very steep carbon gradient the gradation (hypoeutectoid) zone the case, signifying abrupt change from the high carbon case the low car- bon core, always undesirable. Stress concentration this zone results and spalling the case likely occur service. steep carbon gradient may result from improper balance rate car- bon absorption and rate carbon mi- gration. absorption too far outruns migration abrupt and narrow gra- dation zone will result, carbon “piling up” the surface layers more rapidly than can diffuse inward. This would true, for example, car- burizer were used the lower temper- atures carburizing ranges. the other hand, “slow” carburizer used high temperatures, migration more nearly keeps pace with absorp- tion and deep case may obtained without excessive carbon content the surface and without objection- ably steep curve carbon concentra- tion the gradation zone. under- standing these principles will usu- ally point the way proper selection type carburizer and proper working procedure. Slow, Fast Carburizers specified temperature, varia- tion the speed carbon absorption may governed certain extent (1) the type carbon selected for the carburizer base and (2) the kind and quantity energizer used the carburizing compound. Admixture certain ferroalloys also has been found slow the carburizing action, thus making possible the use higher tem- peratures, with resulting shortening the time for production given case depth.’ Naturally there are many needs for hard surfaces mild steel where lo- calized service stresses are not expected, which instances spalling not probable. Very rapid carburiza- tion may then desirable for the pro- duction thin, hard cases. Cyaniding (see next week) serves well many such uses. Ed. Note:—Next week the author concludes with data the pearlite band the case, heat treatment carburized steel, gas and liquid carburizing, and selective carburiz- ing. j j ' ¥ j | | | “DOUBLE BOILER” FOR MELTING ZINC the problems that has come connection with the use and alloy drop hammer dies the aircraft industry has been the melting the zinc such way avoid iron pick-up from the pot. indicated earlier article,* overheating increases the amount iron pick-up from the pot, and the example mag- nesium-aluminum keeping the melting low 900 deg. the chief cure for iron contamination. Iron pick-up may still occur from local hot spots the pot, however, due impingement oil gas flames the like. eliminate such local hot spots zine melting pots, interesting boiler” arrangement has been devised Dies for Drop Hammer AGE, Feb. 1940. 4 = the Martin "double furnace for melting straight zinc for drop hammer dies. lead found the bottom the inner pot when zinc base alloys are being melted. ° ° RIGHT double boiler furnaces. Because the dies poured are often large size, the ladle almost big the pot and filled through plugged gate the bot- tom. the Glenn Martin Co. Balti- more, said the largest aircraft factory the United States. Patents have been taken out the furnace construction. can seen the line drawing, the zinc melting pot proper sus- pended larger pot which filled with molten lead. The outer pot comes contact with the combustion flames, and the heat evenly distributed the inner pot through the lead. When melting 99.99 per cent pure zinc, layer molten lead also left the bottom the zinc pot. believed Martin engineers that the inner pot will last for indefinite period, and that cheaper grades steel may safely used for such pots, since the inner pot spared the eroding effect the zine the points extreme heat. Rather recently, however, with the current trend the Martin company has adopted the use Zamak one the alloys mentioned above, place straight zinc for drop hammer dies. When melting this material the Martin furnace, the molten lead shown the bottom the zinc chamber the melting chamber, not used because the strength such alloys seriously affected the presence even min- ute quantities lead the mix. Nor steel plate used for the inner pot construction. Peculiarly enough, these zine alloys have very erosive effect upon steel, though straight zinc does not. Martin found that special analysis cast iron serves much better and when melting such alloys gives life com- parable steel pots when melting straight the Martin furnace. THE IRON AGE, May 30, 1940—23 | H ~ | > = HOMER WEAVER, General Electric, who developed the new process permanent straightness into steam turbine shafts and rotors, shown here inspecting one the thermocouples before the run. The shaft supported standard lathe bed, electric oven closed about and controlled heat applied through the strip heaters shown the wall. the oven heat raised, the rotor loses its straightness. Then, certain critical temperature, straightness restored which not affected temperature tem- perature changes. ° ° ° BELOW peace time record the periscope far more creditable than its use submarines sink shipping. the power field and throughout the industry, billions dollars worth machinery and countless lives have been protected through adequate interior inspec- tion large forged steel shafts. Here shown, the Milwaukee plant Allis-Chalmers Mfg. Co., one the biggest generator shafts ever built being set for periscope inspection make sure there are flaws the metal. handle, and portable, this new model laboratory mixer built Mixing Equipment Co., Rochester, The speed may 1750 r.p.m. This model may used beakers small 300 cc. without throwing out the contents, may used agitate the HIS electric salt bath furnace designed that the furnace itself virtually pyrometer calling for refusing electric power temperature fluctuations dictate. Made Commerce Pattern Foun- dry Machine Co., Detroit, this Upton furnace capable doing practically any heat treating operation involving temperatures from 250 2500 deg. The resistance the salt bath causes the current fluctuation. Galvanometer, electric eye, relays and system 3000 contacts are included the control. URING the latter part 1935 and the early part 1936 two men New York City tackled the problem polishing stainless steel watch case backs. These men, Blaut and Harold Lang, found that they could produce polish 18-8 stainless steel—silver soldered per cent nickel silver and covered with oxide scale result this silver soldering operation—by treating the combination anodically bath con- taining hydrofluoric acids. They applied for patent the descaling, electro-etching and elec- tro-polishing stainless steels this mixture acid and proceeded with further development work. Numerous samples were prepared. They found that was possible obtain any de- sired degree polishing properly adjusting the composition the solu- tion, the temperature operation, the current density used, and the time lines, they produced numerous sam- ples 18-8 stainless steel. artist was employed develop designs and number art panels various shades were produced. During the fall meeting the American Society for Metals 1936, the writer showed numerous sample panels produced Messrs. Blaut and Lang various members the steel industry. Examples descaling hot rolled and chrome and 18-8 stainless steels were exhibited. Examples descaling and satin finishing mill finished 18-8 were And examples vari- ous types shaded etching and elec- shown. They were all looked with interest and with skepticism. had long been known the steel in- dustry and particularly the stain- less steel industry that the more piece steel was pickled the whiter and frostier the surface became. say that this situation could reversed and that the longer piece metal 26—THE IRON AGE, May 30, 1940 was pickled, even though electric current was used, the brighter and more lustrous would the come, was rank heresy. Although the samples distinctly proved this (the samples are still available), the whole idea electro-polishing stainless steel was not taken with great serious- ness. 1937 panel board carrying number these electro-polished, elec- tro-etched and descaled samples produced Messrs. Blaut and Lang was exhibited the Metal Products Exhibit Hall New York City. This was referred the August, 1937, issue Metal Industry. photograph the panel which was display the Metal Products Exhibit was shown Fig. the first section this article, last York, United States patent No. 2,115,005 April 26, 1938, describe their process considerable detail. For descaling all stainless steels bath about per cent sulphuric and per cent hydrofluoric acid used. For electro-polishing the burnishing process, bath per cent sulphuric and per cent hydro- fluoric acid used. Operation room temperature lower and cur- rent densities are the order 0.5 amp. per sq. in. original Blaut-Lang Process considerable value and has its applications, there are operat- ing objections the use acid pick- ling baths containing per cent hydrofluoric acid. fumes are bothersome, although not gerous acetic anhydride acid, and problems develop connection with suitable tanks vats for operation. Blaut and tinued work intensely develop other electro-polishing baths which would get around their difficulties. This they have accomplished and the present Blaut-Lang baths for success- ful operation all types stainless steel, nickel, monel, aluminum and aluminum alloys contain fluoric acid. These baths are the sub- ject further patent applications now the United States Patent Office. The new Blaut-Lang bath for use all forms stainless steel for elec- tro-polishing has base phosphoric and sulphuric acids. produces electro-polish all grades less steel. Lindh Sweden, United States patent No. 2,145,518 Jan. 31, 1939, describes method brighten- ing nickel surfaces. the development the use sul- phuric acid bath deg. deg. and with current densities 280 560 amp. per sq. ft. method brightening nickel plated surfaces. interesting note that Proctor recommended sulphuric acid bath nickel. This has already been referred the item appearing Metal used current densities only per sq. ft. instead the high current densities Lindh. Sykes, Chicago, United States patent No. 2,146,488 Feb. 1939, lytically pickling metals. This ap- paratus consists arrangement whereby electrical contact need made the strip being pickled. High current density and either d.c. a.c. Current densities the order 100 amp. per sq. it. surface be- ing treated are reported. The ap- paratus mentioned particularly connection with pickling acid solu- tions but makes reference the particular kind acid use its Yerger and Todd, New Jersey, United No. 2,165,326 July 11, 1939, describe method electrolytic treatment | ~ 7 4 % f ' “age j 4 | | | | | | | | | whereby the material made cathodic for period and then anodic with the optional procedure again making cathodic. They refer both pick- ling and bright dipping steel arti- cles this means. United States patent No. 2,172,421, Sept. 12, 1939, describes chemical treating process for stainless steels develop more corrosion-resistant sur- face. The treatment consists chemical pickle mixture sul- which has been added. Forty per cent sulphuric acid, plus per cent hydrochloric acid plus per cent titanium tetrachloride recommend- ed. description given the technique followed adding titanium tetrachloride the solution holding the solution once has been added. tetrachlo- ride the chemical used for smoke screens and for skywriting air- planes. Its fumes are very irritating indeed. George Kiefer, Allegheny Lud- lum Steel Corp., The Dec. 21, 1939, discusses electrolytic polish- ing stainless steel, and describes the use phosphoric acid for this purpose. This process one believed licensed under the Burns patent No. 1,658,222, which has been dis- cussed previously, The conditions Kiefer and the conditions favor- able for cleaning suggested the inventor, Burns, are given the com- parative table that follows: Burns Kiefer 70 per cent Solution 70 per cent phosphoric acid acid Temperature 50 deg. C. No control Current 100 amp. ver 432 amp. per density sq. ft. sq. ft. Carl Schaefer, Casco Products Corp., Bridgeport, Conn., Metal dustry, January, 1940, SAM TOUR Vice-President, Lucius Pitkin, Inc., New York electrolytic polishing metals currently showing considerable com- mercial activity. Three proprietary processes have already been presented THE IRON AGE, and fourth, the Blaut-Lang process which Lucius Pitkin has interest, presented herein. the first section this article last week the author described the background and development the idea elec- trolytic polishing metals. conclusion, herein, attention directed primarily the Blaut-Lang process, its characteristics, operation and future possibilities. “Anodic Polishing This article mainly review the numerous articles Jacquet which have been referred previously and which are also referred the Jan- uary, 1940, issue Metal Progress also previously referred to. Lippert, metallurgical editor The Iron The Iron Ace, Jan. 11, 1940, discusses “Pickle Pol- ished Stainless Mr. Lippert’s article describes the electro-polishing process the Rustless Iron Steel Corp. and shows pictures installa- tions operating accordance with their process. Lippert reports that the Rustless Iron Steel Corp. em- ploys solution concentrated citric and dilute sulphuric acids. detailed data are given regarding the concen- trations acid used has not been possible make complete experimental runs with the acid concentrations Rustless Iron Steel Corp. Lippert reports also that the Amer- ican Rolling Mill Co. (associated with Rustless this development work) has other types electrolytes file the Patent Office the characteristics which are not known. has been impossible make experi- mental tests using any these elec- trolytes determine what their appli- cation might be. Lippert also refers processes be- ing suggested Battelle Memorial Institute and states that their solution Again impossible make tests for com- composition not divulged. parison results obtainable from their solutions compared those obtained the solutions others. Pray and Faust Battelle Memorial Institute, The Iron April 11, 1940, make numerous inter- esting comments electrolytic polish- ing metals, but they fail give any information what electrolyte they use they propose suggest for doing the work. They propound theory why electro-polishing takes place certain metals cer- tain solutions, and attempt show that Fink and Kenny equipotentializ- ing surfaces occurs anodic pol- ishing metals. discussing the Fink and Kenny patent, has already been pointed out that Fink and Kenny did nothing that numerous others had not done before anodically pickling steel acids. was also pointed out that Fink and Kenny obtained equipotentializing surface, then everybody who ever anodically pickled steel acids obtained similar result. Experimental Comparison the most interesting application the electro-polishing process connection with stainless steel, was decided make comparative tests various stainless steels with number the processes which have been re- ferred connection with the his- torical part this article. The three common varieties stainless steel are 18-8, meaning per cent chromium and nickel with carbon under 0.10 per cent; chrome, meaning approximately per cent chromium, any nickel and carbon under 0.12 per cent; and THE IRON AGE, May 30, 1940—27 i j ¥ ° ° 5 ut 4% | = Bre 4 grade with carbon about per cent. The 18-8 stainless steel com- monly used two finishes known No. and No. polish respectively. The No. finish produced pickling clean after annealing and then giving the material pass the The No. polish finish obtained the application emery polishing procedure. supply 18-8 each these two finishes and supply each the stainless steel was purchased. The material was cut into in. panels and number panels each type stainless steel were treated each seven methods. The seven methods will described below Method No. covered patent applications. This acid and sulphuric acid. these tests temperature 180 deg. and current density amp. per sq. in. were used. The 18-8 No. finish was treated for min., the 18-8 No. polish was treated for min., the chrome stainless steel for min., and the chrome stainless steel for min. Method No, process described Kiefer The per cent phosphoric acid, current density amp. per sq. in., time treatment min., and with temperature control. Warner, patent No. 1,658,222 1928, assigned Western Blaut-Lang process 28—THE IRON AGE, May 30, 1940 patent under which Allegheny-Lud- lum operating. The principal dif- Burns’ patent and its application Allegheny-Ludlum Steel Corp. de- scribed Kiefer change time and current density. the tests be- ing described, per cent phosphoric acid solution was used deg. for min. with current density 100 amp. per sq. ft. Method No. Colin Fink and Kenny, United States patent No. cordance with the preferred practice described this patent, bath 42.5 per cent chromic acid was used temperature deg. C., and current density 0.06 amp. This equivalent 0.39 amp. per sq. in. accordance with the patent recommendations, the time treatment was hr. Method No. James Kelvie, United States patent No. 2,037,633 April 14, patent describes making the steel alternately anodic and cathodic with intermediate periods straight chemical pickle. patent requires temperatures kept below 100 deg. mends bath per phos- phoric acid. attempt dupli- cate the conditions called for this patent, per cent acid bath was used room temperature. Voltages 634 volts were used. Lead electrodes were take the place the fixed alternate anodes piece 4 7 stainless steel was treated being made the anode for then al- lowed still pickle for then being cathode for sec. then still pickling for more and then repeating this cycle four more times, making total time treat- ment anode sec., cathode sec.. This gross 175 sec. approximately Method No. Larsen, United States patent No. Dec. 18, This patent describes metals using phosphoric acid hibit the formation stains work when exposed air after dipping the bath. not electrolytic pickling process. has gested that Larsen’s bath consisting mixture sulphuric, nitric and phosphoric acids used still pickle might give some indications pro ducing polish stainless steel with- out the use electric current. Tests acid, per cent nitric acid, and per cent acid straight still pickle ature for min. British patent No. 305,036, Jan. 28, 1928. accordance with the wording this patent, deg. sulphuric acid solution was prepared. specific volume this solution was added the weight with the sulphuric acid, the products ° ° sam ples stainless steel articles finished electropolishing, the Blaut-Lang proc: ; | 7 \ | 5 j | 4 | stainless steel ar- ticles have been electropolished the Blaut-Lang proc- ess demonstra- tion. being calcium sulphate acid. The reaction resulted which after hr. was removed from the solution filtration. Anhydrous sulphate was then the filtrate until more would dis- solve, thus indicating Specimens were treated the manner. The specimens were made anode for min. and then made cathode for equal length time. current density 100 amp. per sq. was used. The runs were made room temperature, Such series experiments shows some interesting results. Some the processes clean the steel, and some ap- parently have polishing effect vary- ing amounts. Some etch certain steel and some polish, 18-8 very well but have far less satis- factory straight-chromium grades, vice-versa. This series experiments can duplicated laboratory. Blaut-Lang Process Blaut-Lang acids for the purpose all types steel, nickel silvers. also for electro- = 4 alloys nickel-silvers. The Blaut-Lang processes which have heen developed since and which are the subject further patent applica- tions are applicable all types stainless steel, aluminum and many aluminum alloys, nickel and monel metal, plain carbon steels and variety other metals. these proc- esses, the base the electrolyte acids. The proportions trations acids, the temperatures operation and the current densities vary according the particular metal alloy heing treated. Special tion agents have been developed Which cedures have been developed for col- trolling the solutions during operation that they will continue function and uniformly for long periods time. installation for the Blaut-Lang processes consists lead-lined tank for holding the electrolyte and equipped with suitable tain temperature. The work hung from copper racks designed copper lead may used cathodes. Cathodes are placed near the work possible order tank capacity and order Normal required. operations are carried out with practice. The length ti