The Iron Age 1940-01-11: Vol 45 Iss 2

VAN DEVENTER President and Editor BAUR Vice-President and General Manager Managing Rditor News Editor Editor Bmertteus Machinery Bditor Art Editor Metallurgical Rditer Associate Editors Washington Fditors W. Morrrrr JAMES ELLIS Resident District Editors Pittaburgh Chicage Cleveland Detroit Editorial Correspondents London, England Cineinnats FRAZAR Boston Hamburg, Germany Milwaukee San Francisco Toronto, Ontario Birmingham Jan uary 1940 Leroy ALLISON Roy Newark, NJ St. Louis F. T. TURNER, JR ° uffalo Pickle Polishing Stainless Steel DIX, Manager Reader Service Robert F. Blair 621 Union Bldg., Cleveland ’ Herman, Chilton Bldg., Phila. What's New H. K. Hottenstein, 1012 Otis Bidg., Chicage Leonard, 239 39th St., New York All Peirce Lewis, 7310 Woodward Ave., Detroit Ober, 239 89th New York razing Aluminum Farts Warren. Box 81, Hartford, Conn New Power Transmission Equipment Don F. Harner, 1595 Pacific Avenue, Long Beach. Cal. . the Assembly Line Member, Audit Bureau of Circulations Member, Associated Business Papers Indexed the Industrial Arts Index. I) Published every Thursday. Subscrip- Washington Ne $ Fr tion Price: United States and Pos- sessions, Mexico, Cuba, $6.00; Can- Single copy, 25 cents. Annual Num- December Pig Output Weekly Ingot Operating Rates Owned and Published by CHILTON COMPANY Rate Activity Capital Goods (Incorporated) Plant Expansion and Equipment Buying Editorial and Publication Office Executive Offices Chestnut and 56th Sts.. 239 West 39th Philadelphia. Pa... U.S.A New York, N. Y., U.S.A OFFICERS AND DIRECTORS New Industrial Literature MUSSELMAN, President JOS. S. HILDRETH, Vice-President ° GEORGE GRIFFITHS, Vice-President Products Advertised TERHUNE, Vice-President VAN Vice-President Just Between Two BAUR, Vice-President WILLIAM BARBER, Treasurer Index Advertisers 116 JOHN BLAIR MOFFETT, Secretary JULIAN CHASE, THOMAS L. KANE, G. BUZBY, P. M. FAHRENDORF, HARRY DUFFY Copyright 1940 Chilton Company (Inc.) at | | | | | ot | 2 _— pee 35 | ROL . PITTSBURGH ROLLS DIVISION BLAW-KNOX Partner” PITTSBURGH, y ... THE IRON AGE ... JANUARY 1940 ESTABLISHED 1855 Vol. 145, No. The Ticket? You Pick It! IFE the United States seems consist, nowadays, one emergency after another. First was the bank crisis, next the N.R.A., and now the war emergency, whatever that means. Probably something like limited earthquake limited cyclone. countries abroad get that they take their bombings nonchalantly, even without the aid cigarettes. Perhaps too can get used these emergencies time. And perhaps fa- miliarity may breed dangerous contempt. They say that people can get used anything and that the civilians the war-infested That would too bad, for real emergency might come along some day and would not recognize it, having heard the little boys cry many times. matter fact, the prospects are that when this war over are going face real emergency the unlimited variety that will good deal more serious its effects business than the present limited one. That coming post-war emergency will have with our world trade. Unless some- thing happens prevent it, are going see our foreign trade manufactured products melt away after peace declared with the rapidity icicle Gehenna. The reason for this obvious. For the past five years have been equipping Europe compete with after the war over. and large, European plants now have newer and better equipment than the plants this country, which the average age half the equipment years more. And more than this, Europe, being fully equipped for war, over-equipped for peace. She will able scrap her old machines and for world trade with the latest cost cutting devices. With distress labor rates abroad that will ensue, this combination will undersell American products nearly every market. That when our next unlimited emergency will occur. For this cheap foreign tion will not limited our export trade. will dash over our protective tariff walls and through the interstices our reciprocal trade treaties. When that time comes, one year, two years, four years hence, will out luck, indeed, then face the threat continuance anti-business administration. And the people who will the most unfortunate will the wage earners this country who can longer depend upon superior machines defend them against low foreign wage rates. That something for everybody think about this election year 1940. « 4. ee | 4 | | | | SHEETS STRIP Even “Kept one thing make good sheet steel—another see that reaches the customer absolutely unmarred, ready for use. Inland does both. Inland’s packing and loading methods are the result specialized study and long experience. Careful wrapping moisture-proof paper, and steel wrapping under tension provide the maximum resistance corrosion and scratch- ing caused internal movement. Car loading gets special attention, too. Each package floating unit which does not contact others, nor the ends and sides the car. The best feature this method is—it works. typical the service Inland gives every customer—a service which applies each shipment steel, large small. Inland methods sheet protection are typical the care used not only making, but shipping every Inland Product. When you need thoroughly careful steel service this the nearest Inland office. TIN PLATES STRUCTURALS TRACK ACCESSORIES REINFORCING BARS Dearborn St., CHICAGO District Offices: MILWAUKEE DETROIT ST. PAUL ST. LOUIS KANSAS CITY GENERAL discussion the flame hardening process, equipment used, quenching procedure, and the progressive method flame hardening are all pre- sented the author herein. the second and last sec- tion this report, appear LTHOUGH the process flame hardening ferrous the oxy-acetylene been use for many years, has only recently been developed position great importance the field heat treatment. The early refinements the flame hardening technique were developed England within the past Meehanite metal for general engineer- ing purposes produced five types, known as: GA, GB, GC, and GE. Process provides minimum tensile strength 50,000 per sq. in., true transverse strength 3300 lb. per sq. in. (18-in. centers, 1.2-in. bar), and com- pression strength 175,000 per sq. in. Meehanite used machinery, machine tool castings, pressure castings and wide range castings for many other purposes. BICKFORD Engineer, Farrel-Birmingham Co., Inc. next week, various types hardening machines will described, well the characteristics the hard- ened Meehanite case, the minimization distortion, and the advantages Mee- hanite metal flame hardened. decade effort provide satis- factory means hardening gear teeth. The contemporary advent Meehan- ite metal* has provided material more amenable treatment flame hardening than the ordinary com- mercial gray cast iron. generally well known, the flame hardening process fundamen- tally simple principle. oxy- acetylene flame located im- pinge directly against the surface hardened, thus rapidly raising the metal temperature above the crit- ical point. This temperature, course, the same required other meth- ods hardening. Rapid cooling ef- fected contact with suitable quenching medium immediately after heating. Equipment The equipment required depends upon the nature and quantity work done—it may vary from simple portable hand blowpipe set and pan water for spot hardening small parts complete acetylene generat- ing system, central oxygen manifold, and special machine for moving the torches and quenching device over the The oxygen supply station consists battery compressed oxygen tanks connected manifold which feeds the distributing line through pressure regulating valve which main- tains constant line pressure. each station where the gas consumed, must pass through another pressure regulating valve which delivers the blowpipe the pressure required the operation. The blowpipe mixes the oxygen with acetylene the proper proportions and delivers the mixture suitable head tip where discharged and burned. Acetylene supplied acetylene generators which automatically main- tain constant pressure the distrib- uting line. Like the oxygen, must THE IRON AGE, January | | y | 4 ? | : | ° ° BR Quenching Hardened case, pass through regulator station. Besides delivering the gas the required pressure, the regulator acts safety device prevent po: sible backfires from reaching the line. single quick-acting shut-off valve usually necessary give the operator control over the supply both gases simultaneously. However, main separate hoses until mixed the blowpipe. Any torch that will evenly heat the desired surface may used. single tip suitable burner for spot hard- ening hardening narrow areas, such smaller gear teeth, but does not give sufficient flame coverage for most purposes. wider flame path obtained using multi- flame The multiple tip head employs one more rows tapped holes into which are screwed small drilled tips. This type head may made con- form wide range surface con- tours selecting various lengths tips using plugs required. The tips, however, gradually become short- ened service, due the extreme heat, and continual replacement nec- essary. Plain drilled face heads are being used with good results, however, and Direction trave/ flames section YPICAL torch and quench used sive hardening. can made special shapes where plain faced head not suited. flame heads require cooling with cir- culating water prevent pre-ignition the gas This water may discharged from drilled the flame ports, thus making un- necessary use separate quench, Quenching Although possible use va- riety solutions quenching medi- ums, plain water far the most hardening converted lathe. Distortion held minimum circulating water through the core the casting. The symmetry the casting and simultaneous hardening both sides are desir- able reducing the distortion. ~ vv g ° ° ‘ The a mi\\- ¢ \ surface series jets from drilled orifices, the form sheet issu ing from slit. has been found that more efficient than total immersion the part still water, because the ve- locity the stream washes away the steam bubbles they are formed. suitable quench may made drilling row small holes piece pipe. has been done determine Considerable experimenting quenching arrangement types operations. usually de- sirable have the quenching water strike the work closely the flames guard against interference flame splashing excess water running ahead the quench. The angle between the quenching stream and the surface treated and the effect gravity are important considera- tions. Obviously, the best drainage excess quench water obtained when the direction travel relative the work upward. large volume clean water necessary for satisfac- tory quenching, and pressure fluctua tions the quenching water are avoided. Progressive Method The progressive method flame hardening, variations are used the large majority general work. consists traversing the surface hardened with one number flames immediately followed spray type quench. This results hardened case, the depth and hardness which are each function the traversing speed, the distance between the flames and the work, and the dis tance between the flames quench measured the surface. The width the hardened path de- pends upon the width the burner less. There upper limit the width the area treated, since depends which upon the number torches available maximum rate which the gases may supplied. the case rolls hard- ened the vertical combination method, the width the heated band the entire circumference the roll. The annealing previously hard- ened case may accomplished the omission the quench, Special precautions must taken when passing over edges holes the work because the heating rate f da if hardening roll the vertical combination method vertical boring mill. increased, and heat dissipation into the body the part less rapid. This re- sults dangerously high tempera- these guarded against either controlling ture the speeds, using suitable shields such carbon plates rods. rapid that traversing speeds from in. per min. are commonly Since the flame exceedingly high temperature (over deg. F.) should have full control the trav- ersing speed during the operation and impinges directly surface, the operator avoid melting searing the surface the metal. Much depends upon the skill and alertness the operator and results depend largely upon his expe- rience and training detecting the proper color the heated area for se- lection speeds. There zone lower hardness which marks the boundary between two areas the same surface when areas This unavoidable because the tem- perature gradient the area causes the drawing any previ- these separately. heated ously hardened area, and this hardness not restored quenching except where the temperature above the critical. However, this drawn band overlap can held narrow width, usually under half inch, and can often positioned such way that not objectionable service. Attempts harden rough casting surfaces have not been rewarded with satisfactory results. This probably due the fact that the oxide coating, commonly referred the skin the casting, acts insulator against heat induction. However, usually desirable machine surfaces which are flame hardened since this re- duces the amount subsequent grind- ing eliminates altogether, result- ing the increased depth useful case. The uniformity necessary the progressive hardening quires surface accuracy approxi- mately 1/64 in. Obviously, prelimi- nary machining required obtain this accuracy. Ed. Note:—Next week the author con- cludes this report with description hardening machines, notes the charac- teristics the hardened case Meehan- ite, and technique for the minimization distortion. THE IRON AGE, January we ‘ tig: | a £ OMMERCIAL units, licensed Rustless Steel Corp., now are electrolytically welded stainless steel wire products, such those shown these two pages. Note the typical high re- flectivity. years ago certain tech- nical director certain large stainless steel mill boggled the idea electrolytic polishing stain- less steel. the past eight months, this director went through probable $30,000 experi- mental effort develop such proc- ess, only today find himself John- ny-come-lately. competition, that old dependable persuader which packs particularly hard wallop the sen- sitive stainless steel industry, must the credit for the reversal ment. The question letting the pickle tank take the place of, supplement the wheel—with quicker, cheap- and more dependable many instances—has been boiling be- neath the surface the industry for the past several years, but never quite foaming enough break into print. Any recent visit number stain- less steel plants inevitably resulted laboratory sample being whisked from locked drawer and proudly dis- played with accompanying farrago technical and commercial patter. inevitably the sample was spot welded wire ice box shelf, one- half dark and discolored and the other half bright with the coruscation electrolytic polish. Just equally inevitably, the description never got down brass tacks regards bath performance and degree commer cialization. only proper that many mills have many ice box shelves many drawers. For, wire likely will sold 1940 for this one purpose alone than for any other single outlet. General Electric in- troducing stainless shelves its stainless wire each box, and with yearly production all boxes all makers more that 2,500,000, potential future market for 12,500 tons stainless wire indicated, which tidy bunch steel any sales man language—and particular sig nificance that electrolytic polish- ing goes the credit for opening this outlet. Additional are evolving the moment, instance small parts difficult hold against wheel, intricate parts the recesses which cannot reached tions that would tear wheel apart, and rough forging and castings which now can easily given the typical sheen stainless. For that matter, new outlets, even now not envisaged, will likely follow the more widespread commercialization this method finishing stainless steel articles. luxe Stainless, polished the conven tional manner, requires quite sojourn the buffing department. there may polish with 100 grit, then 120 grit and grease, 180 grit with grease, and final buff with 280 grit and grease secure mirror mercial No. finish. there danger the wheels loading, the work scoring burning, and flat surfaces warping. Such finishing can frequently time consuming, ex- asperating, because the human ele- ment involved, and run costs con siderably. Numerous possible outlets for stainless can not carry such costs. and there are innumerable preferably made stainless, which be- themselves readily wheel polishing reversed electroplating bath. The work polished made the anode, and naturally certain small amount surface metal removed. The elec- varieties, some which are others regards ease control. absence obnoxious, poisonous explosive fumes, speed polishing. cost current, exhaustion solution, and lucency finish. Electrolytic pickling course now common industrial process and electrolytic polishing metals such tin, copper, aluminum, nickel, cobalt and certain alloys has been described briefly. (See International Tin search and Development Council, bul letin No. 90, and for August, 1936, and April, the (anodic treatment, pickling), stainless steel com- pletely new and some instances still subject considerable refinement. The first article describing appeared the Dec. 21, 1939, issue Iron which set forth the process sponsored Allegheny-Lud lum Steel Corp. The Rustless Iron Steel Corp. has patent applications another process (described herein). which process has two commercial units operation since September. 1939, one the plant the Young Spring Wire Co., and the other Wall Wire Products Co., Plymouth, Mich. Another proc ess being merchandised under the direction Sam Tour operating the plant Philip Sievering, New York jobbing electro and Cooper Alloys, stainless steel castings processes are heing suggested Battelle Memorial Institute, Chem and perhaps parties which have far not come the attention. Che divers proc esses may dis- tinguished partic the electrolytes used. Several patents have already been issued and multitude applications are pending. for these latter, understandable that the parties involved are cent regards electrochemical char- acteristics. This much known, however. The Allegheny-Ludlum mentioned, uses straight phosphoric acid, license from Western Elec- tric Co.) although variations this electrolyte are suspected but not known, The Rustless Steel Corp. em- ploys solution concentrated citric and dilute sulphuric acids, American Rolling Mill Co. (associated with Rustless development has other types electrolyte file the patent office, the character- istics which are not known. Sam process involves patent speci- fying concentrated sulphuric and hydrofluoric acid electrolyte, but other solutions containing acid are the patent office, some which are designed polish metals other than stainless, for instance nickel, brass and aluminum. What Battelle’s solution the writer does not know. recent patent the Chemical Foundation mentions acid solution containing titanium tetrachlo- ride, impart coruscant surface stainless alloys. And, recommenda- tion has been made Jacquet and (Comtes Rendus, March 27, 1939) acetic anhydride and acid solution for polishing stainless steel specimens for micro- scopic examination. Obviously, therefore, there are number competitive solutions soon confuse the many possible users HESE polished articles are shown demonstration the ver- satility the pickling method. Only the cooking pot (lower right) re- quired supplementary cathode. The refrigerator electric light cover (upper center) commercially pickle polished—most the other ar- ticles shown here will still commercially wheel polished, for reasons such cost, removal scratches, etc. The articles they come from the tank have the high finish shown. 24—THE IRON AGE, January 1940 this type finishing claim highly lustrous surfaces, quently with certain degree corus- cation. Most the solutions operate about amps. per sq. in.; most require comparatively ture control; and there certainly tions, life and control, well health and explosion precautions. But these details naturally must await issuance most the patents before any clarification these factors should attempted. Installations Rustless Certainly one the most energetic developers pickle polishing stain- less steel has been Rustless Iron Steel Corp., Baltimore, which com- pany has collaborated with Armco over years. method commercial production practice (designed for sheet and strip products) which some additional data will forthcoming the near future. several whereas The two large Rustless units, con- structed with the active engineering cooperation Munning Co., are now operating regular production the Detroit area the plants the Young Spring Wire Co. and the Wall Wire Products Co., and were installed and placed operation during September, 1939, following use smaller pro- duction unit which had operated about the new installations capable trolytically polishing stainless steel electric refrigerator shelves per day. shown the accompanying photograph, loading and unloading the shelves accomplished manually from single position. The work rack placed moving carrier and the articles under treatment travel around the tank and back their starting po- sitions under accurate speed control. The running time for complete cir- depending upon the shape and size the refrigerator shelf, and there are work carriers the assembly. The solution contained lead lined comparatively high temperature means electrical immersion heat- ers. most efficient temperature range fairly narrow, but control temperature the commercial units has not constituted operating prob- lem. Direct current supplied means 7500 amp. volt motor- generator set. Current density for most | | | | | | CLEAR WATER RINSE ALKALI RINSE RECLAIM RINSE TANK WORKER LOADING AND UNLOADING CARRIERS ELECTROLYTE HEATED WITH ELECTRIC IMMERSION HEATERS FANS TWO SUPPORTS EACH CARRIER BUS BARS CATHODES MOTOR REGULATE SPEED CARRIER +CONTACT CONTACT FOR INSIDE CATHODE FIXED CATHODES electrolytic polishing unit commercial operation the Detroit area, for finishing refrigerator shelves. Running time for complete circuit the tank from min. This particular installation will polish about 5000 stainless work the order 0.5 1.5 amp. per sq. in. addition the two Detroit manu- facturers, Rustless states that has other licensees under its electrolytic polishing process, which fully cov- ered patent applications. claimed that the electrolyte employed, which consists concentrated citric acid solution acid, has many desirable characteris- tics, such stability and long life and additions necessary only gases fumes, freedom from undue corrosive action the tank equip- ment, comparatively good “throwing and low cost maintenance. addition, further claimed that such operating variables density and time treatment may varied over reasonably wide range without detriment change character and brilliance the polish- ing effect which obtained. absence noxious \lexander Feild, director chemical research Rust- less, the polished surface character- ized very high intrinsic brilliance. This brilliance characterizes not surfaces which were initially flat uniform gradually varying curva- tures such sheet, strip and wire, but likewise characterizes According castings and forgings which have been electrolytically “polished,” spite steel shelves each working day. the fact that the castings forgings still retain after treatment irregular surface. probably true that the differ- ence between the stainless steel sur- face which has been subjected ordi- nary pickling treatment and electro- lytically polished stainless steel surface due the fact that the former case the surface absorbs successive reflections within its microscopically jagged matte surface large pro- portion incident light rays, whereas the latter case high percentage the light which falls the surface reflected because the absence acute indentations irregularities. The manufacture fabricated wire products generally involves welding operations, usually the spot welding Welds are fact essential im- type. most articles this type. portant feature the Detroit area stallations Rustless’ that the electro- polishing removes discoloration and oxide scale which formed result the spot welding will cut down burrs, fins and sharp corners, addition, contributes polish the underlying stainless steel surface. the standpoint con- sumer acceptance, the importance this latter fact cannot overempha- sized. Rustless reports that its process has been used successfully the electro- lytic polishing variety articles for the refrigeration and packing in- dustries, including electric refrigera- tor shelves, meat savers, meat hooks, meat pins, meat molds the household utensil field, frying baskets, percolator parts, pots, potato strainers, egg cookers, and many other items; the field, knives, forks and spoons, well variety miscellaneous items such shelves, bar spoons, wire baskets mashers, various types and sizes, valve forgings, soap dishes, bathroom fixtures, screws, electric fan encasements springs, ven- tilators, test tube racks, hub caps, lens windshield wiper parts, moldings, rings various sizes, tubing, wire screen, instrument panels, ladle han- dles, castings, straight wires, etc. Some trated, have area less than sq. in. while others may have 600 sq. in. more surface. experimentally polishing certain articles formed from sheet strip, such cooking pots and cups, has been found necessary use cathode which conforms general way the shape the article question. However, spoons, bathroom fixtures and other small shallow sheet articles require special cathode. Also, such special cathode has not been re- quired the polishing fabricated THE IRON AGE, January at. e d y e wire articles, even those articles that appear subject severe problems current distribution. far the writer knows, none the electrolytes mentioned herein has really excellent throwing power, which tates the use supplementary cath- odes for deeply recessed articles. Rust- less’ electrolyte, for example, has been compared with chromium plating solu- tions However, this unfortunate com- parison that the former anodic throw whereas the latter cathodic throw. certainly true that many problems connected with throw into recessed articles are lieved when taking off metal rather than putting metal on. And, some the large ice box shelves are now being cleaned without supplementary cath- odes, whereas chrome plating the same shelf would hardly attempted without extra anodes. power. Pickling Panacea made herein, perhaps, would carry the suggestion that polishing stainless steel mechanical means doomed, such definitely not the case. Elec trolytic polishing certainly uni versal panacea—it bound definite limitations, least far. electrolytic polishing complementary mechanical polishing, the writer’s opinion, least. The final polish obtained electrolyt 26—-THE IRON AGE, January 1940 ically definitely related the condi tion the surface start with. The electrolytic treatment with its brilliant finish contrast accentuates the vis- ibility metal defects such pits, scratches, abrasions, and actually serves the best inspection meth- ods possible. Thus, frequently the elec- trochemical treatment can serve preparation for mechanical polishing, HIS stainless steel valve forging has been polished elec- Note the typical bright- ness the surface, even though still rough. Castings can handled the same manner, the re- sult being stain- less-looking surface without going un- necessary cost re- move the roughness. thereby shortening the entire finishing process considerably permitting the operator rapidly pick out defects. also quite likely that the removal of, say, 0.002 in. from rough forging casting will smooth the surface some- what and remove some the surface defects. Starting with good surface (or drawn surface, wire rod), the articles coming will have very bright specular finish. articles with rough sur- for instance, castings, the elec- trolytic treatment course brings out the intrinsic brightness the stain- less alloy, but the incident light dif- fused and the finish naturally not specular. far, generalization regards competitive costs mechanical and electrolytic polishing possible. Each has its own particular sphere su- premacy, and where overlap careful study would neces- sary show which should used what combination the two should many articles, for molding, which can polished chanically automatic machines, the electrolytic method cannot compete regards cost, one reason manual racking involved. Success- ful experimental work has been done bulk treatment small articles such screws, but doubtful conventional barrel burnishing will repleced any large extent. For drawn articles electrolytically, careful study has made the shape, location and cost supplementary cathodes, the method submersion prevent ing pocketed hydrogen, current dis- tribution, all which runs costs which would liquidated only long runs many similar parts Makers drawn articles such pots and pans have investigated electro- lytic polishing but far the writer knows have not adopted the process. Rather, the preference retain me- chanical polishing which one oper ation removes scratches, etc., and gives uniform appearance over the entire article. Electrolytic polishing would not remove the scratches, and there might well differences re- between the flat portions and those portions where the grain had been coarsened severe drawing tion. Still another exasperating prob- has been encountered—whether close the bead leave left open and then closed after electro lytic polishing, difficulty would perienced with marring the finish closed, the maker has positive the closure tight. Otherwise, elec trolyte will creep and not moved the cleansing wash. heaven would ring the loud cries the housewife who later had such pot which, after washing, drooled forth some goo that would etch line down the side. This problem has not been satisfactorily solved, and when quite likely equally exasperating prob lems will develop other directions regards incidental characteristics tions are stated their sponsors not directly affecting the corrosion re- that is, passivating effect pro- duced. The Rustless and Armco proc esses, however, are claimed pow- erfully passivating action, and al- though the complete theoretical back- ground for such action not known, the result may well due the anodic action which powerfully ox- idizing, from the nascent oxygen that liberated 1 | | i } | 4 | ; 4 H | ae | | | LNICO, the magnetic alloy which over the past few years has en- joyed rapidly increasing commercial acceptance, has always been cast shape. Because the hardness the metal any finishing machining oper- ations have been most difficult. Now, Alnico being sintered shape, with dimensions held very close limits. How this done and what results are obtained are herein described for the first time. metallurgy, guished many unique char acteristics, has been used great advantage several applications which have grown consider importance. Three outstanding examples are ductile tung sten, culminating efforts the search for durable and efficient lamp fila ment; so-called oilless bearings; and hard cemented carbide tool materials. Sintering tungsten powder circum vented the problem melting and pouring metal above 6100 deg. Powder metallurgy furnished meth- for attaining self lubricating porous, copper-tin alloy, having even distribution graphite which could readily sized press without expensive machining. HOWE Research Laboratory, General Electric Co. the application powder metallurgy the manufacture per manent magnets the Alnico type, similar those made the form castings several General Electric Co. licensees, has become established basis which assures future devel opment The adaptation sintering Alnico unique that broadens the field magnet application through the production magnets too small and factorily economically. Sintered competes with castings where greater physical strength desirable. where higher uniformity flux distribution required, and plications where the smoothness and accuracy size minimize eliminate grinding operation. Aluminum Complicates Sintering Alnico may contain per cent aluminum addition nickel, copper and iron. were not for the aluminum content, sintering might simple matter, but this element has such great affinity for oxygen that readily converted inert oxide, not reducible hydrogen. When the particles aluminum come oxidized, they are not free enter into combination with the other metals. Many attempts were made include appreciable quantities alu- minum hydrogen sintered alloys, but the conversion aluminum the oxide alumina occurred aluminum could alloy with the other metal particles. many instances the pressed bars increase volume. The conception that aluminum dis solved one the other Alnico con stituents would less subject oxi- dizing influences led trying several alloys. The most practical these was per cent ferro-aluminum which very brittle and readily disintegrates into fine powder. The this alloy powder with the other powders produced the first sintered magnet having properties comparable with those cast Alnico. Hydrogen Purification Another important feature early stages the development sintered Alnico was that large quan tity pure dry hydrogen was neces sary. The laboratory means for re- moving traces oxygen from hydro- gen that time was pass the gas over crushed ferro-silicon heated 1650 deg. With freshly exposed surfaces, that method efficient and useful small scale, but extended use diminishes the useful surface the silicon ineffective amount. has been known for some time that oxygen can removed THE IRON AGE, January 1940—27 2 | “\ i 4 | drogen passing over hot copper. The copper acts catalyzer con- verting the oxygen water which can absorbed drying agent. was found possible use elaboration this method for producing the con- tinuous supply dry hydrogen neces- sary for successful sintering. Regardless the purity the hy- drogen, real advantage will derived unless the hydrogen used enclosure where purity tained. avoid contamination the gas, rectangular iron sintering box was first used. Pure dry hydrogen was fed into one end through tube, the other end being tightly fitted with plug having opening large enough allow escape hydrogen from the container slight positive pressure. Such container was loaded and troduced into hydrogen for the sintering operation. sintering, the container cooled the furnace and then re- moved from the furnace cooling. The load inside the contaiaer was under the protection hydrogen during cooling. Magnets sintered this method cooled too slowly im- part metallurgical state suitable for good permanent magnets therefore, the magnets had reheated and cooled controlled rate. processing step, that sinteriag, and 28—THE IRON AGE, January 1940 make the production Alnico commercially feasible, pressed magnet preforms could fed continuously. The desirability such furnace became apparent the very early stage production when dif- was experienced getting uni- form sintering each piece over the entire length the load, which was sintering and, therefore, subject in- equalities temperature. This was acute problem because the sintering temperature close the melting point the alloy. Also, putting large masses cold material into furnace this type sets thermal shock which, when repeated several times, destructive refractory aad heating unit, which further contributes condition uneven heat distribution. passing continuously through furnace, the effect any temperature gradients the hot zone nullified because each magnet, regardless position boat, passes through the length the hot zone and all magnets receive exactly the same sintering treatment. Boat Construction the sintering temperature the alloy iron, surfaces reducing atmosphere are condition for sticking together. Some IG. group articles sin- tered Ainico, the smallest weighing oz. and the largest oz. The paper clip cluded show relative size. materials used for boats, for ex- ample cold rolled steel (0.20 per cent C), may slag which will stew out and come contact with the sin- tering tube bottom. Such ously interferes with the progress though the tube dusted with alumina. Rolled boat materials sometimes swell over sizable areas because in- ternal gas pressure developed the reduction oxide seam. Any one these conditions hazard the furnace operation and may cause appreciable loss production was apparent that operating one would trouble keeping the sinter- ered with alumina prevent sticking and consequent buckling boat with greatly reduced ten- hydrogen was made pressing com- posite slabs from high purity iron powder and iron powder containing alumina, the latter forming the weld- ing resistant surface. After sintering hydrogen ordinary purity, these slabs were fabricated into boats welding the straight sides. End pieces against which pushing done were cut from sintered slabs and welded abutting surfaces are faced with the protected side. This | | ys | | ! © type boat has been used with ex- cellent results and particular atten- tion has been paid periodic replen ishment alumina dust the tube bottom. The boats tend become warped after prolonged use, but they may straightened cold vise hydraulic press without damage. lron-Alumina Boat Another useful type boat made completely iroa-alumina mixture which may pressed thick enough that the middle can machined out est 1/5 oz. Fig. shows larger mag nets formed automatic mechanical and hydraulic presses. Alnico not readily machineable the final sintered condition. the “as pressed” condition too fragile for machining, enough for ordinary handling. strong satisfy requests for experimental samples cases where mold expense not justified, pressed bars are par- tially sintered hydrogen furnace and pushed directly into jacketed cooling chamber. this par- tially sintered condition, bars j J 2—Sintered Alnico magnets larger type, formed automatic mechanical and hydraulic presses. alumina boat refractory and when badly warped, must discarded. With the exception ferro- aluminum, the other constituents Alnico are purchased manufactured powders. Most sintered magnets are small size and can economically and well tablet mak- ing machines. The magnet preforms pressed these machines are loaded boats and fed into continuous furnace for progress through the hot zone and into the extension for controlled cool- resentative current production shown Fig. compared with ordinary steel paper clip for size. The smallest weighs 1/224 oz. and the larg- easily machined. Parts shaped this are just good magnetically after the final sintering the bars sintered the regular way. example this process, Fig. shows the sequence operations form- ing magnet from disk pressed stock mold. The material cost for sintered Alni present greater than that for the cast product. Some this dif- ference undoubtedly made the elimination the scrap loss which oc- curs the casting process. However, other economies are desirable make the cost sintered magnets more at- tractive. big step this direction has been accomplished controlling the cooling rate the magnets that they cool rate which gives the magnetic quality. Proper desirable magnetic quality depends largely upon the state dispersion the inter- tional aid this direction obtained making modification composi- tion. ‘The incorporation final heat treatment the sintering furnace operation leaves only pole face grind- ing, magnetizing and checking done. The latter two operations are now being done automatically one large scale application. the present stage development, the economics sintered product over the cast tor magnets weighing 0.1 Ib. less. optimum cot ling is The term sintering applied Alnico might well defined the thorough inter diffusion four five metal powder constituents into complex alloy comparable with cast- ing physical density. The sintered magnets are fine-grained and, therefore, have much higher physical strength than the cast product times greater respectively transverse and tensile tests]. The photomicrographs Fig. show the grain size contrast Alnico made sintering and melt- ing. The same permanent magnet qual- ity cast Alnico present the sintered product. This includes the highest amount stored energy per unit volume any permanent magnet material produced commercially today and high resistance demagnetiza- tion due stray fields, vibration and heating. sintered herently physically and magnetically homogeneous throughout and are used standard reference test specimens for General Electric licensees, and for comparative tests with the Bureau Standards. They serve the important function get- ting accurate comparative magnetic measurements the different permea- meters which not test the same They have consequent poles and are sufficiently strong me- chanically withstand breakage accidents occasionally encountered handling shipping. Magnetic properties two representative stand- ard bar specimens are recorded Table section. Solder Used Mounting some applications desirable mount magnets apparatus means other than clamping. Overheat- ing during low temperature brazing with fluxes and alloys sometimes has caused magnet spoilage. When this THE IRON AGE, January 1940—29 Ip g x F le, re V- 1g ot n- n- : d- se 1S 3—In partially sintered condition Alnico can machined, after which final sintering carried out. lowed the proper cooling rate restore the desired metallurgical struc- ture necessary. Welding develops large grain size locally and imparts extreme local brittleness. Since the proper cooling rate incorporated the sintering cycle, desirable either the physical magnetic strength. Experimental with this objective mind strong joint could made with soft solder and the usual zine chloride solu- tion flux after the aluminum has been removed from the surface etching. with good results, particularly perimental assemblies. the sim plest method attachment and means fabrication prefer able the cutting down cross section which sometimes occurs with bolting clamping. Also bolted loosened Soldering was invaluable the construction assembly designed demonstrate the possibilities high ratios. early design resulted lifting ratio excess 4400 the object held weighed Ib. and the magnet, oz. Differing from usual magnetic circuits, this new high ratio unit con- sists assembly several parts, including sintered Alnico magnet. When joined together, they form unit containing segmented shunt. this method leakage very low and the magneto-motive force ized efficiently that greater loads may held ing the amount Alnico used. Hith erto holding ratio has not increased directly proportion magnet size, due metallurgical and the greater internal reluctance. should stated that this kind hold- ing magnet assembly not intended for miscellaneous use, nor pected competitive with the large so-called lifting electromagnets use today for car loading and unloading. greater energy Alnico can used utmost advantage and sible the expansion permanent mag net applications. Pole Faces Attached Soldering pole faces can attached soft soldering both sintered and cast Alnico for the purpose collecting flux and concentrating small air gaps. also possible form iron faces integral with magnets ing. This done depositing layer iron powder top the Alnico mixture the mold die prior pressing. During the sinter- ing operation both layers sinter and bond together. iron backing appreciable thickness similarly applied may drilled and tapped spot welded. the use this method attachment the magnetic path must one which partial shunting will not occur. Iron pins sleeves may anchored sintered magnets sertion the pressed ing sintering Alnico shrinks per cent, depending upon pressure) and holds inserts tightly. Insert di- ameters should small with respect the surrounding mass avoid the extreme strain and distortion which cause unsound magnets. Alnico has made available perma nent magnet greatly improved char- Fic. 4—Grain size contrast Alnico made melting (left) and sintering (right). Both views 250 diameters. 30—THE IRON AGE, January 1940 | “4, | | i | | x * 4 « my i q ‘ " 4 4 iif greatly increased the number ap- plications for the use pendent and constant source mag neto-motive force through substitution for electromagnets, and has made possible new applications small light-weight magnets high physical and magnetic strength. And, the limi tations imposed the lack ductility and machineability cast Alnico have become less important with the devel opment the sintering process. Both cast and sintered Alnico have definite economic places industry, but press ing and sintering close size have minimized finishing operations. What finishing necessary can done rap- idly grinding without danger incipient surface cracks The extent any commercial sub stitution sintering for casting will depend costs, further simplification techni powder TABLE Magnetic Properties Two Types Alnico tizing Induc- Force, tion, Oersteds, Gauss, H max. Bmax. Alnico 2000 12,375 Alnico 2000 12,800 Residual Energy Force, tion, Product Oersteds Gauss (BaHa) 420 7400 4900 528 7610 4650 problems and processing gained production perience. Improvements i For information regarding theory permanent magnets, the reader referred the following: “Permanent Magnets Theory and Practice,” by S. Evershed, Journal [.E.E., vol. 58, No. 295, September, 1920, p. 7S8 to 827 “Magnet Steels and Permanent Maze vol. 51, No. June, 1932, 410 417 Also A.S.M. Metals Handbook, 1939 tion. “Some Principles Governing the Choice and Utilization Permanent Magnet Standards Scientific Paper No. 567. “Permanent Magnets,” Edgar, General Electric Review, vol. 38, No. 10, October, 1935, p. 466 to 469. Low Temperature Joining Sheet Metal methods sheet metal parts the form jomming low temperature soldering eration have recently been announced Both use pastes, one combination with rod. The so-called Colaweld brushed onto the metal the points paste where joining take place, rod applied, then subjected heating claimed that the lighter the gage the metal, the faster the action, and the stronger the band. The range gages from 0.005 0.050 and ferrous metals, particularly alumi num alloys also carbon steels and stainless steels. The material made form for similar application production basis, according the maker, the Colonial Alloys Co., Somerset and Trenton Avenues, Meltomatic paste solder the name given new self-cleaning fluxing paste solder being marketed Wayne Chemical Products Co., The paste brushed the metal where needed (see accompany ing illustration) and heat apphed the parts being joined, either with gas other flame, electricity, hot oil the furnace. The paste melts temperature slightly higher than 400 deg. Because simplicity oper ation and the absence prior clean ing, substantial reductions labor costs over conventional soldering op- erations are claimed. Material waste lessened also, since there ex- cess solder melt and drop off. Only enough paste used cover the area to be bonded. said facilitate sol dering small articles where irons are difficult manipulate, and per mits the operator reach small spaces not accessible with stock. also permits the simultane ous soldering several articles units. unconventional application has been the attachment name- plates motor blocks. THE IRON AGE, January » , be a foundry molding sand can prepared this No. size Simpson mixer, the largest machine ever built National Engineering Co., Chicago. This mill ft. in. eter and weighs 35,000 The mullers weigh 5500 each, and the drive 60-hp. motor. 32—THE IRON AGE, Januray 1940 ABOVE first aluminum pressure cast rotors made Reliance Electric Engineering Co., Cleveland, had outside diameter in. The larger rotor shown here in. diameter, and indicates the ad- vance casting technique since The increase size has been made possible preheating the core around 600 deg. before casting, the use increased casting pressures, and the speeding the casting press. LEFT ONTINUOUS processing alu- minum strip facilitated through roll type cross seam welder built Federal Machine Welder Co., War- ren, Ohio, for welding the ends successive aluminum strips together. This machine makes two welds once series. Aluminum alloys 24-ST and 52-ST are handled, maximum width being 104 in. and minimum width in., while thicknesses range from minimum 0.008 0.08 in. maximum. > * q 7 a at ABOVE JOHN X-RAY SERVICE, has announced cas- for X-ray technicians. The main feature this cassette here} the fact that always remains the job. The only thing that has carried back the darkroom for re- loading are flexible film folders. An- other feature visible the photograph are interchangeable filter set fronts. ABOVE These filter sets can chosen ac- EMENTED carbide now available the cordonce with the voltage employed form tubing, spirals, and round ard the thickness the metal shaped bars, according the Carbolo Co., penetrated. Inc., Detroit. Produced means ex- trusion process, these products are considered distinct innovation compared with previous practice. Formerly such parts were available only within ex- tremely limited size range and was necessary perform large part the shaping operation manually. With the new process, the parts are available lengths in. and within diameter range from 0.015 in. O.D. RIGHT type steel mill slitter developed the Yoder Co., Cleveland. The speed the pull-out tension rolls synchron- ized with the speed the operation, and the slitter page either through the rolls cutters. The first unit recently installed Ohio River steel plant 275 300 ft. per min. THE IRON AGE, January 1940—33 $ fi BRAZING ALUMINUM RAZING aluminum al- loys, particularly batch brazing the furnace method, t