The Iron Age 1944-06-22: Vol 153 Iss 26

VAN DEVENTER President and Editorial Director BAUR Vice-President Seneral Manager Editorial and Advertising Offices 100 East 42nd St., New York N.Y., U.S.A. Johnson, Market Research Mgr. Hayes, Production Manager. Baur, Typography and Layout Regional Business Managers New York New York 100 East 42nd St. 100 East 42nd St. Cleveland Pittsburgh 1016 Guardian 428 Park Bidg. Philadelphia Chicago Chilton 1134 Otis Bidg. PEIRCE LEWIS WARREN Detroit Hartford Cenn. 7310 Woodward Ave. Box RAYMOND KAY Los Angeles 2420 Cheremoya Ave. Owned and CHILTON COMPANY (Incorporated) Executive Offices Chestnut and Sts. Philadelphia 39, Pa., U.S.A. OFFICERS AND DIRECTORS MUSSELMAN, President JOS. HILDRETH GEORGE GRIFFITHS EVERIT TERHUNE VAN DEVENTER Vice-President BAUR Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JULIAN CHASE THOMAS KANE HARRY DUFFY CHARLES HEALE Vice-President Vice-President Vice-President ° ° Member, Audit Bureau Circulations Member, Associated Business Papers Indexed the Industrial Arts Index. Pub- lished every Thursday. Subscription Price North America, South America and Possessions, $8; Foreign, $15 year. Single Copy, cents. IRON AGE Vol. 153, No. Editorial When the Flit Flies the Little Bugs Die First............ Technical Articles Metallurgy the Gray Iron Continuous Heat Treatment Aluminum Design for Postwar Planning Safe Practices Working Magnesium.................. Drop Forgings Produced Flat Die Features News and Markets Maritime Ship Failure CMP and Heavy Inventories Silicosis Cure Reported Finished Iron and Steel Machine Tool News Non-Ferrous Metals News and Developments Non-Ferrous Metals Prices; Scrap Prices Iron and Steel Scrap News and Finished Iron and Steel Steel and Warehouse Semi-Finished and Tool Steel Prices............. Steel Pipe and Tubing Pig Iron and Coke Prices............ Railroad Material and Stainless Steel Index June 22, 1944 47 | 100 104 105 107 110 144 146 147 148 150 151 152 153 154 155 156 157 158 quotations uP abricating this required ate Products| bend quired for IRON ESTABLISHED ° ° ° June 22, 1944 VAN DEVENTER President and Editorial Director BAUR Vlee-President and General Manager ° ° DIX Manager, Service ° ° Editorial Staff Commercial Editor, Editors WINTERS BARMASEL Editorial Assistants SCHIEN WILLIAMS ROGERS Regional News and Technical Editors LLOYD 428 Park Bidg. POST Chicago 1134 Otis Bidg. MOFFETT DONALD BROWNE EUGENE HARDY Washington National Press Bidg. MacDONALD Cleveland 1016 Guardian BRAMS Detroit 7310 Woodward Ave. OSGOOD MURDOCK San Francisco 1355 Market St. Correspondents ROBERT Cincinnati PENLEY Buffalo FRAZAR Boston HUGH SHARP Milwaukee SANDERSON Toronto, Ont. RAYMOND KAY Los Angeles JOHN McCUNE Birmingham ROY EDMONDS Louis DOUGLAS Seattle When the Flies, The Little Bugs Die First who has done gardening farming even small scale must have been impressed certain phases birth, growth and death that are analogous human life and accomplishment. The start from small beginning, the period growth and produc- tivity and the eventual withering away root and vine find their parallels all business and industrial undertakings. Most industrial “plants” are perennials, true, and few may even turn out “century plants,” but even these cannot hope forever. Nature, fortunately for hungry humans, introduces another phase the sequence birth, growth and death. seed bearing and with- out would perish. The old produces, automatically, the provision for the new. There such convenient natural provision for keeping our industrial pastures green. Yet industrial nation must find one perish. Fifty years ago out 100 our healthy present-day industrial plants had not yet germinated were mere seedlings. Fifty years hence the same statement will true. But from what seeds are these future plants coming? America has been fortunate that while Nature has not provided either the seed the soil for the beginnings new enterprise, our rather loose and democratic system government has. has, until lately, given man chance for his alley.” man had good idea for new and useful product and could induce his friends back him for few thousand dollars, just Henry Ford did more than quarter century ago, might plant seed that would grow into business that would not only generate unlimited employment but that would prove bulwark national defense. These little new businesses, generated the seeds private initia- tive years more ago prospered through the reinvestment earn- ings. What healthier way than this make businesses grow? They had particular appeal the followers the “big board” because their names and fames were then unknown. Bankers would not lend them nickel. Government’s function, see it, not distribute free seeds industrial enterprise, has done the past with its lamentably poli- tical free seeds farmers, but provide the atmosphere and the irriga- tion that will enable little plants get good start and grow big. Unfortunately has taken the standpoint that this must proceed hamper and handicap the large plants that are already full bear- ing. well cultivated garden the big healthy plants not squeeze and starve the small ones. Our man-made tax laws the present day do. They reward the businesses that can show the largest lists investors, regardless the outcome them individually and collectively and they penalize the man and his partner who have “put their shirts” into their businesses and who have been independent outside help. Punitive action aimed big business won’t the trick. ness makes room and opportunities for little business. And when you aim the flit gun business whole, remember that the little bugs die first! | | | | 5 ducts 46—THE IRON AGE, June 22, 1944 in ge this emp. | e e be News Front June 22, 1944 Out about 2800 foundries operative the time Pearl Harbor, some 200 Closed their doors due decreasing income returns and labor troubles. Loss these operations, along with reduced production other foundry establishments‘ down output from about 15,500,000 tons made nationally 1942 little more than million tons last year. Northrup's new Black Widow has proved itself effective that Army Marine Corps orders have materially stepped production schedules and backlog keep the plant busy for two years. Northrup and Joshua Hendy Iron Works have announced new, jointly owned pany, the Co. for research and development possible postwar developments. Possible decrease mine production copper more than per cent between and July may hurl copper back into the shortage bracket. This directly the loss labor the western mines. WLB has over 2000 forge and foundry wage cases before and some are over year Old. There are more these than for any other industry. WLB has promised try and clean them July 15. Cleveland Trust business analysis says that business volume has dropped per cent from high last November April this year; factory employment down cent; munitions output dollar volume per cent; factory payrolls per cent; and inventories per cent. White collar workers are now averaging only per cent much mechanical 1939 they averaged per cent, showing the loss ground. Lord Portal's emergency steel house for postwar use now exhibit London. Pressed steel used throughout, and aluminum foil employed for heat insulation. Companies having electrolytic tinning lines are showing considerable interest gas equipment for brightening the surface, displace induction type heaters now use. the Selas type, the double banks gas burners move toward and away from the strip give heat modulation, tin thickness, strip speed, etc., dictates. Experimental work with high speed heating forging has shown heat SAE4340 billet, in. size, uniform temperature 2150 deg. min. There was surface internal cracking, tion and scaling was about 0.001 and 0.00025 in. respectively. The cancellation Budd's large order for stainless steel cargo planes was the result mostly slowness fullfilling the order rather than for performance The latter was excellent, but only several planes have been made, and the meantime many Douglas cargo planes are available. Only the stainless planes will made, and production will cancelled this fall even this number not completed. Already about 1000 workers have been laid off, rehired later shell work speeded. Budd will not make stainless planes after the war, feeling that the costs are high, and plane manufacture more the function intrenched aircraft companies. Although War Department officials maintain that the status Republic Aviation Corp.'s contract for the remains unchanged, government officials other de- partments are discussing what with the Farmingdale, Y., facility and when the contract slashed. War Mobilizer James Byrnes predicts unemployment before the year out because heavy war production cutbacks come even though the war with means increase foundry output, wages that field will probably rise the expense possibly breaking through the Little Steel formula. 4 3 4 3 4 § | = 4 4 5 3 8 4 | RAY cast iron one the most complex alloys used for engineering application, and although large amount knowledge has been accumulated with regard its production technique and the study graphite, only recently has research been devoted exclusively the gray iron matrix. alloy steel which are embedded flakes graphite, its metallurgy in- sofar matrix concerned be- comes less complicated. fortu- nate that the matrix gray iron true steel for much the research conducted steel will apply gray iron. Although gray iron may classed unalloyed, its matrix al- ways alloy steel because the high silicon content that common cast iron. The properties gray iron are de- pendent two main structural char- acteristics: (1) The amount, type and distribution graphite, and (2) the condition the matrix. The cooling rate during and solidification and the presence absence alloy- ing elements and manufacturing prac- tice are factors that govern the graphitic phase and determine the dis- tribution carbon between graphitic and combined states. The matrix will affected the same variables and conditions steel. Some these are discussed the following para- graphs. transformation curve 3.0 per cent total carbon, per cent silicon gray iron. The S-curves Figs and derived for gray cast iron, have con- tributed greatly better under- standing the gray iron matrix. The data for the isothermal diagrams are most commonly procured metal- lographic examinations. Small speci- mens are austenitized (rendered aus- tenitic) then rapidly transferred liquid bath maintained the particu- lar temperature level being studied, held for varying periods time, with- drawn and quenched into water brine. Specimens then are polished and examined microscopically, and any untransformed austenite will ap- pear martensite. Thus, progress transformation austenite con- stant temperatures can followed from beginning end. S-curves pre- sent interesting and valuable pictures which enables metallurgist vis- ualize glance the approximate manner which austenite given composition will respond cooling below the minimum temperature (crit- ical temperature) which austenite longer truly stable. The shape the curve and its posi- the diagram are governed the chemical composition and grain size the austenite. Alloying ele- ments and increase austenitic grain size are conducive lazy austenite that becomes more reluctant transform into ferrite carbide ag- gregates the alloy content and grain size increases. 200 200 i 48—THE IRON AGE, June 22, 1944 The characteristics eutectoid approximately eutectoid matrix 3.0 per cent carbon, 2.0 per cent silicon gray iron with respect transformation austenite con- stant shown the S-curve Fig. taken from Murphy, Wood and D’Amico.' The solid curve the left depicts the beginning austenite transformation one the decomposition structures such pearlite, bainite, and the curve farthest right represents the time taken complete transforma- tion austenite. the field marked austenite (A) has not started transform. the area between the curves representing the beginning and ending austenite transformation, untransformed austenite (A), ferrite (F) and carbide (C) co-exist, the fer- rite-carbide structure increasing and austenite decreasing the longer the sojourn temperature. The field the right indicates that all aus- tenite has transferred one the ferrite (F) carbide (C) structures. From approximately 1000 deg. 1325 deg. F., austenite will trans- form pearlite, the degree fine- ness, decreasing from coarse pearl- ite deg. very fine nodu- lar pearlite 1000 deg. Below 900 deg. the transformation accord- ing the acicular mode with precipi- tation the ferrite carbide gate, and bainite occurring the austenite clevage planes. For prac- transformation curve 0.79 per cent carbon, 0.76 per cent manganese tical auste pera resu rang tral tem tak aus dep cur Atl 0.7 eX: its ca 1400 | ae tical purposes can said that austenite transforms the marten- structures below 400 deg. F., al- though some martensite may form during the cool the isothermal tem- the range 900 deg. 1000 deg. F., austenite appears unable decide whether wishes form pearlite bainite, with the result that the structures this range resemble both. Observations From S-Curves has been observed from the study the gray iron S-curve that (1) all structures found steel are common gray iron,’ all conditions being qual; (2) that the rate austenite transformation dependent the temperature which transformation takes place, and (3) the nature the austenite decomposition product dependent upon the temperature which austenite curred. The curve Fig. from “U.S.S. Atlas Isothermal Diagrams,” S-curve 0.79 per cent carbon and 0.76 per cent manganese steel. examination this will reveal that its shape almost identical that the gray iron curve Fig. and proves that the gray iron matrix be- haves steel, and that the exist- ing store S-curve data for steels can profitably employed cast iron metallurgy. comparing Figs. and for the shortest time aus- tenitizing gray iron, transformation 4—Influence austenite grain size the structure when austenite cooled rate designated ° ° ° BELOW 3—Time required for beginning transforma- tion 2.97 per cent total carbon, 2.02 per cent silicon gray iron 1125 deg. F., after being austen- itized indicated temperatures. ° HAFSTEN Ensign, ° The comments herein prove interesting the average reader accordance with the present trend thought, considering gray iron mixture steel and graphite. gray iron looked upon being graphitic steel, its metallurgy be- comes less mystery and becomes readily the average technical man. ° takes sec., whereas the steel Fig. transforms less than sec. the same temperature. This differ- ence behavior probably due the higher percentage silicon and other elements present the gray iron. like most alloys will, added appreciable amounts, move the S-Curve the right and increase the time for beginning austenite decomposition. Austenitic grain directly related the period for beginning austenite decomposition subcritical temperatures and, therefore, must considered when studying the gray iron matrix. increase grain crease hardenability. The influence austenitic grain size max- imum that portion the pearlite range where nucleation pearlite the austenitic grain The broken line curve Fig. rep- resents the beginning transforma- tion coarse grain austenite the same analysis the fine grain iron (solid curve, Fig. 1), and illus- trates the relationship that exists be- 200 ° ° tween austenitic grain size and the speed austenite transformation temperatures below the critical. The effect austenitizing temper- ature and grain size the isother- mal transformation 2.97 per cent carbon, 2.02 per cent silicon iron 1125 deg. shown Fig. from Rote, Truckenmiller and The time required for beginning trans- formation progressively greater the higher the austenitizing temperature, and accordance with the manner which grain coarsening would proceed silicon- killed steel gray iron which grain refiners were added. The mech- anism the change hardenability with respect austenite grain size shown Fig. derived from data time that some the isothermal diagrams, cooling curves are drawn show certain reactions that involve continuous cooling austenite. This not absolutely correct for the iso- transformation austenite con- stant temperatures only; neverthe- THE IRON AGE, June 22, 1944—49 yn es 1e 1e ; 1e e | 600 TIME SEC. gray iron 3.63 per cent total carbon, per cent com- bined carbon, and 1.75 per cent silicon. iron 3.68 per cent total carbon, per cent combined carbon, per cent silicon and 2.03 per cent nickel. less, they are accurate enough for most purposes used guide for explanations involving continuous cooling. Actually the continuous ing curve lies below and the curves from left right indicate in- creasing sluggishness austenite re- sulting from increase austenitic grain size. cooling curve (A) constant and austenite grain size, variable, can seen that austenite the gray iron matrix will trans- form lower temperatures and will produce harder, stronger structures the austenitic grain size becomes greater. The primary functions alloy ad- ditions cast iron are promote hardenability and control the graphite phase. Alloy additions may also made cast iron stabilize the carbide phase and prevent its dis- sociation ferrite and graphite dur- ing heat With the ex- ception cobalt* all the other com- mon alloying elements retard the rate austenite transformation and shift right, which indicates that slower rate cooling can used assure the austenite martensite transfor- mation. This also signifies that judicious selection alloy elements and percentages these elements, austenite the gray iron matrix can made transform lower tem- peratures and stronger acicular structures cooling the casting from the casting The application alloys the production as-cast acicular structures be- coming increasingly important inas- much the bainite structures cast iron are reputed possess excellent wear and physical properties and have been found certain applica- tions superior the orthodox pearlite matrix.” IRON AGE, June 22, 1944 Alloys and their relationship hardenability can best illustrated loyed and unalloyed gray irons. Com- paring the curves Figs. and taken from Hilliker and Cohen, nickel induces hardenability shifting the S-curve the right. 1050 deg. F., which the temperature which austenite most willing transform for the steels Figs. and aus- tenite will begin its transformation the unalloyed iron sec., while the nickel iron the transformation be- gins approximately sec. This means that heavier casting can successfully heat treated. Influence Alloys The curves Fig. from “U.S.S. Atlas Isothermal Diagrams,” dem- onstrate how easily alloys influence austenite into transforming air cooling the acicular structures, and also prove the feasibility using curves already derived for steel explain reactions the matrix gray iron. soft iron the analysis, 3.4 per cent total car- bon, 2.40 per cent silicon and 0.75 per SEC. cent manganese had as-cast struc- ture that consisted pro-eutectoid ferrite and coarse the addition 1.50 per cent molybdenum the tensile strength was raised from 27,200 52,400 per sq. in. and the hardness from 170 277 Brinell. The alloy also changed the structure the matrix from ferrite and pearlite bainite. The mechanism the change can shown schematically reference Fig. The broken line curve the S-curve 0.35 per cent plain carbon steel and corresponds the matrix the gray iron. The solid line curve represents 0.35 per cent carbon, 0.82 per cent molyb- denum steel and corresponds the alloyed gray iron. the same dia- gram cooling curve rate that might obtained the center the unalloyed 0.35 per cent carbon austenite cooled rate shown the cooling curve will transform into pro-eutectoid ferrite the pro- eutectoid field and into coarse ite, (A) estimated hardness 177 Brinell. Alloyed austenite cooled the same rate transforms, with the ° ° transformation cent total carbon, 2.48 per cent sili- con, per cent nickel, 0.98 per cent molybdenum gray iron, plotted per cent trans- formation. — i 1400 800 | exce forn ite, deg. role tral the tua | con but ant SOI els 1400 p-800 ll 200 SEC. “TIME transformation curves 0.35 per cent transformation curve 2.58 per cent carbon and 0.82 per cent molybdenum steel. exception small percentage that forms pro-eutectoid ferrite, into bain- ite, hardness 221 Brinell (B) 1000 deg. appears then that the main role the alloy this case sup- press the transformation austenite pearlite and allow the austenite transform lower temperatures the stronger acicular structures. Ac- tually austenite does not transform continuous cooling (A) and (B), but little below and the right, explained previously. Figs. and from Flinn, Cohen and Chipman,’ show the S-curves some high alloy gray irons. The rate isothermal transformation mark- edly retarded all temperature lev- els. Molybdenum very effective forming bay the approximate temperature range 900 deg. 1000 deg. F., and this range that austenite most reluctant begin its transformation. Because the sluggishness austenite the range where pearlite the decompo- sition product, acicular tures can readily secured the mal tion curve 2.56 per cent total car- bon, 2.55 per cent silicon, 3.06 nickel and 1.02 per cent molybdenum gray iron, plotted per cent trans- formation. ° ° ° total carbon 2.55 per cent silicon, 1.02 per cent nickel, 0.53 per cent molybdenum gray iron plotted basis and per cent transformation. as-cast condition. the section the casting becomes greater, the per- centages alloys must necessarily increased maximum physical properties the gray iron the as- cast heat treated conditions are obtained. can concluded from the fore- going that austenite the gray iron matrix varies its speed trans- formation different temperature levels below the critical, and that this variation that determines the characteristics the and physical properties the gray iron matrix the as-cast heat treated condition. Chemical composition and grain size the austenite are the main factors that influence the shape and position the S-curve and re- sponse austenite given heat treatment. Opinions assertions contained this article are private ones the writer and are not construed official reflecting the views the Navy Department the Naval Ser- vice large. Bibliography D’Amico, Transformation Gray Iron,’ Transactions, American Foundrymen’s Association, vol. 46, 1938, 563. 2C. Hilliker and Cohen, “Iso- thermal Transformation Austenite Gray Cast Iron,” THe vol. 147, Feb. 13, 1941, 43. Flinn, Cohen and Chip- man, “Acicular Structure Molybdenum Cast Transactions American Society for Metals, vol. 30, 1942, 1255. Davenport, “Isothermal Trans- formation Steel,” Transactions Ameri- Society for Metals, vol. 27, 5A. Greninger and Troiano, “Kinetics the Austenite Martensite Transformation Steel,” Transacticns American Society for Metals, vol. 28, 1940, Steel Corp., “Atlas Isothermal Transformation Diagrams,” 23. Hafsten, “Influence Austenitic Grain Size Isothermal Transformation Behavior SAE 4140,” Technical Pub- lication No. 1276 Trans. AIME 145, Wood, “Electrical Resistance Method for the Determination Iso- thermal Austenite Transformations,” Transactions American Society for Metals, vol. 30, 1942, 1359. “Transformation Austenite Con- tinuous Cooling and its Relation Transformation Constant Tempera- tures,” Transactions American Society for Metals, vol. 29, 1941, 85. Vanick, “Methods Hardening Cast Iron Heat Treatment,” Metal Progress, vol. 29, January, 1936, 40. Archiv fur Angewandte Wissenschaft und Technick, vol. No. May, 1943, pp. 148-156. Bartholomew, “Gray Cast Iron New Treatment,” THE vol. 146, No. Aug. 1940, 52. Cast Iron,” Climax Molybdenum Co. THE IRON AGE, June 22, 1200 1200 1000 1000 a 600 400 400 200 q hoe i- | Besides illustrating some phenomenal gains output and cutter life the use negative angle carbide milling cutters over high speed steel cutters, the author presents test data chart form demonstrating the relation lead bevel angle and the number pieces obtained per grind, and the relationship between spindle horsepower and depth cut, feed rate and width cut. Cutter life tests are summarized. The material was originally presented the Westinghouse Machine Tool Electrification Forum Pittsburgh May. FROMMELT Director Research, Kearney Corp., Milwaukee IMITATIONS tungsten car- 1928 made inevitable that further developments make possible the use this cutting material not only for cast iron and the non-fer- rous materials but also for steel. The possibility machining steel with carbide first became reality with the introduction tantalum carbide 1931. about this time, industry’s experience with negative angles the single point tool machining some non-ferrous materials, such bronze, was translated the machin- ing steel with single point tan- talum carbide tools using negative angles. This naturally led ex- perimentation with flywheel cut- ter milling machines the ma- chining steel. The success such cutters, least with some restric- tions their application, indicated definitely that the milling steel with multi-toothed cutters would be- quite 52—THE IRON AGE, June 22, 1944 come possibility. Such machining operations, however, were left the commercial development new which appeared about 1938 the form tungsten titanium car- bide. was this time that multi- tooth cutter employing angles successfully milled steel considerably higher rates feed and speed than was hitherto possible. War’s insatiable demands for ma- terial increased the use and applica- tion this new carbide the mill- ing processes. present, the car- bide milling steel regular pro- duction procedure numerous indus- tries. Its peacetime use and applica- tion assured and while may never replace entirely the older cutting ma- terials such high speed steel, safe assume the present stage development that the majority steel operations will the future effected with benefit carbide-tipped multi-tooth cutters. Carbon milling steel with tungs- ten titanium tips limited the present largely for such milling cutters face, half side, shell end mills and slotting and slit- ting cutters. Inherent difficulties the application and grinding tips have thus far prevented its use form cutters and such special appli- hobs. These obstacles may overcome but for the present not possible pre- dict éven advisable consider the complete substitution carbide for high speed. Negative Angles The technique milling steel with presently limited the use negative angles both the rake and the helix. This not true included the lower Brinells and semi-steels where positive angles are quite effective. But for reasonable cutter life under every day shop con- ditions, negative angles for both rake and helix seem necessary the this procedure the mill- ing steel and its alloys. These angles are shown the accompany- ing line drawings, Figs. and pressures with negative angle are applied the tip away from the cutting edge amount approxi- mately equal the chip thickness. Whereas the use positive angles ing edge, which the weakest and least supported portion carbide tip, directly stressed the cutting forces. would seem, from these simple illustrations, that the use negative angles milling the harder and more difficult materials machine, such steel and its alloys, are necessary. any rate the present time, the develop- ment the technique carbide mill- ing steel built largely around the incorporation negative angles, bot tip 4 J | | the Spr bic tic th : ha Rotation Positive angle Positive illustrating positive and negative helix and rake angles with re- spect the direction rotation. both rake and helix, into carbide tipped cutters. High Surface Speeds This technique characterized the use relatively high surface speeds. Friction and abrasion are car- bide’s worst enemies; the use pe- ripheral speeds that range from 500 1000 ft. per min. apparently lessens the abrasive effect the carbide tip while the work. There are indica- tions that the lower surface rates (in the neighborhood 400 500 ft.) are advisable for heat treated steels that are the neighborhood 375 Brinell. The untreated steels, both carbon and alloy, the other hand, are being milled successfully peripheral speeds high 800 1000 ft. per min. Where neces- obtain high finish (in the high surface rate and relatively low chip load are necessary. The results considerable experi- mental work indicate definite advan- tage high chip loads. should pointed out that high chip load and good cutter life are related cause and effect. The thicker the chip the farther from the cutting edge will the cutting forces applied. This assists preventing the breakdown this cutting edge and creases the cutter life. high chip load also closely connected with higher rate metal removal per horsepower. Some these results high chip load may apparent from examination Fig. Here, obviously, the thicker the chip the less effect the cutting forces will have the unsupported and relatively weak cutting edge. There follows from the characteris- already referred to, namely high surface speed and high chip load, the use relatively high feeds this technique carbide milling steel. Since the feed rate dependent the three factors chip load, num- ber teeth per minute, the use high peripheral speeds and high chip loads will re- sult high rate which the work- piece being fed into the cutter. These feed rates will vary, naturally, different applications and will de- pend, among other things, upon the amount power available. These rates will discussed with reference particular applications sec- tion devoted such discussion. High Horsepower Consumption follows from the above considera- tions that the horsepower consumed carbide milling steel relatively high. Experimental work shows the cutting forces necessary remove metal with negative angles per cent. Since the peripheral speeds are five ten times higher than those commonly employed with high speed steel cutters, the rate applying these cutting forces and, therefore, the horsepower consumption creased proportionately. Specific ref- erence will made horsepower consumption section that follows, horsepower data. Since the feed rate depends upon the three factors chip load, num- ber teeth and surface feet per minute, current practice limits the number teeth employed milling cutters. This pitch varies different localities and among designers, but strike average current practice throughout the country can ex- pressed the diameter inches plus Thus, in. cutter will have two. six teeth, in. cutter eight teeth, etc. The fundamental reason for employ- ing coarse pitch cutters the neces- sity for restricting horsepower con- sumption within reasonable limits. There seems, however, further necessity for using fewer teeth certain applications where large chip accommodation space necessary due the width the cut the length time the carbide tip contact with the workpiece. Flywheel Effect Because the coarse pitch cutters that characterize current practice carbide steel milling, flywheel effect seems essential. Attempts made build such effect cutter bodies not, however, considered either good 2—Comparison chip action with positive and negaitve rake milling cutter tips. the chip load comes directly the cutting edge the carbide tip, where- the cutting pressure applied away from the edge amount approxi- mately equal the chip thickness. Positive rake angle | Thicker chip THE IRON AGE, June 22, 1944—53 le, it- ‘or ‘or les nd als its es, Fig. 3—Operating data face milling operation rack segment. MATERIAL: Stee! forging HARDNESS: MACHINE: No. vertical SPINDLE MOTOR: hp. SPEED: 1074 SURFACE SPEED: 750 ft. per min. FEED: in. per min. CHIP LOAD: 0.010 in. CUTTER DATA DIAMETER: in. ANGLES: deg. neg. rake, deg. neg. helix, deg. lead OPERATION RESULTS SPINDLE HORSEPOWER INPUT: hp. NO. PASSES PER GRIND: 150 TOTAL CU. IN. METAL REMOVED: 234 CU. IN. PER SPINDLE HORSEPOWER: 0.6 TOLERANCES: Plus minus in. FINISH: 30-49 Micro-in. Depth cut 0./87 Area cut Fig. 4—Operating data face milling tractor links. MATERIAL: Annealed forging HARDNESS: 185 Br. MACHINE: Special duplex SPINDLE MOTOR: hp. SPEED: SURFACE SPEED: 418 ft. per min. FEED: in. per min. CHIP LOAD: 0.0129 in. CUTTER DATA DIAMETER: in. NO. TEETH: ANGLES: deg. neg. rake, deg. neg. helix, deg. lead OPERATION RESULTS SPINDLE HORSEPOWER INPUT: NO. PASSES PER GRIND: 125 TOTAL CU. IN. METAL REMOVED: 663 CU. IN. PER SPINDLE HORSEPOWER: 1.43 TOLERANCES: Plus minus 0.0005 in. FINISH: Superior H.S.S. cutters area wide end Fig. 5—Operating data milling slot wing hinge. MATERIAL: SAE 4340 HARDNESS: 402 Br. MACHINE: Simplex SPINDLE MOTOR: hp. SPEED: 264 SURFACE SPEED: 552 ft. per min. FEED: in. per min. CHIP LOAD: in. CUTTER DATA DIAMETER: in. NO. TEETH: effective ANGLES: deg. neg. rake, deg. helix OPERATION RESULTS SPINDLE HORSEPOWER INPUT: 18.5 NO. PASSES PER GRIND: TOTAL CU. IN. METAL REMOVED: 183.4 CU. IN. PER SPINDLE HORSEPOWER: 5.7 TOLERANCES: Plus Minus 0.0005 FINISH: 20-30 micro-in. 54—THE IRON AGE, June 22, 1944 design effective the elimination undesirable impact loads. eliminate these undesirable effects, re- sulting from large cutting forces and coarse pitch cutters, flywheel should installed the arbor, prefer- ably built into the machine spindle. There are definite indications that effect necessary some categories carbide steel milling increase cutter life and also elim- inate excessive depreciation equip- ment. The full, definite and specific results flywheel effect will come only, however, from much more ex- perimental data than now avail- able. What information hand supports the contention that definite flywheel effect necessary for eco- nomical performance the use this procedure. Production Gains Cited few typical examples will gains speeds and feeds made possible changing over from high speed steel carbide cutters with negative angles. Fig. shows regular production operation con- verted from high speed steel car- bide, permitting increase feed rate from in. per min. and increase spindle speed from 1074 r.p.m. The number pieces obtained per grind increased from 100 150 with the conversion car- bide and the finish micro- in. obtained appreciable im- provement over that obtained with high speed steel, which was estimated micro-in. The production this instance was increased approximately ten times. The operation face milling the tractor link shown Fig. was per- formed special duplex milling machine, each spindle which powered 7.5 hp. motor. con- verting from high speed steel car- bide face mills, the feed rate was in- creased from in. in. per min. and the speed from 200 r.p.m. The 8-in. cutters used had wedged solid carbide blanks instead brazed tips. The metal removed with this type cutter was 663 cu. in. per grind compared with 365 cu. in. for the brazed tip milling cutter under iden- tical conditions. Milling the slot the aircraft wing hinge, Fig. presents in- terrupted cut, which detrimental the life the carbide tips. The con- version from high speed steel car- bide tipped cutters resulted in- crease the feed rate for in. per min. in. The spindle speed was cutt in. hig twe and cut ing rak ber lea 33, sul pas ter era dif dic re] ani lin ate cel sil stepped from 264 r.p.m. Per- haps the most outstanding feature this operation, which regular production run, the increase cutter life from hinges per grind 35. addition, the tolerances are much closer—for parallelism 0.0002 in. maintained; for width 0.0005 in. The finish with carbide tipped high speed steel; micro-in. finish conservative estimate. Comparative Data Fig. shows the relationship be- tween the number workpieces cut and the lead bevel angle the The cutter used these tests was in. diameter face mill, hav- ing eight teeth with deg. negative rake and deg. negative helix. interesting note that the num- ber passes for and deg. lead angles the same, 20. The deg. lead angle shows in- crease the number passes 33, while the deg. lead angle re- sults cutter life equal passes. While these results may not absolutely conclusive, they indicate tendency the effect lead angle cutter life for this particular cut- ter. may that different periph- eral and feed rates will result different cutter life than that in- dicated this graph. The results test showing the relationship between depth cut and horsepower indicates straight line relationship, Fig. Since the ratio greater than one, the in- crease horsepower proportion- ately less than the increase the depth the cut. other words, the depth cut doubled, the horsepower does not increase 100 per Increasing the depth cut from 0.050 0.100 in., for example, increases the horsepower from approximately 10%. this graph, Fig. showing the relationship between the horsepower and the feed rate, the curve ap- proximately straight line, although here again the horsepower does not increase proportionately the same rate the feed rate. Thus, pos- sible increase the feed rate from in., while the horsepower in- creases from only 67. The graph, Fig. representing the between spindle horse- power input and the width cut with constant diameter cutter interesting that the curve approxi- mates double reverse “S” type 1G. pieces per grind using various lead bevel angles. Rake angle neg. Helix angle 7deg. neg. Cutter No. load per tooth 0.009 in. curve. The ratio between the no-load horsepower and the actual cutting horsepower for the smaller widths workpieces smaller than the ratio no-load horsepower actual cutting power for the wider width workpieces. The rate increase power less than in. in- dicated the graph, than from in. Two factors should noted playing important part 0.225 Machine: 2408 Simplex Spindle pindle speed- 205 in. per min. Cutter data in. No. 7—Relation- ship between spindle horsepower and depth cut using negative angle milling cutter. Depth cut Oo Oo lead Type inserts Solid carbide this relationship: First, the en- trance angle with the smaller work- piece decidedly positive com- pared with true negative entrance angle in. workpiece. Second, the wider workpiece involves longer arc carbide cutting tip contact and hence relatively greater power con- sumption. The interesting series curves shown Fig. indicate the increase helix Spindle horsepower THE IRON AGE, June 22, 1944—55 l- )- )- 0.200 r- 0.075 0.050 vertical horsepower-50 Depth cut- 0.325 in. Material BHN So Spindle horsepower + w CUTTER DATA Cutter Brazed body Diameter Relation- ship between spindle horsepower and feed rate using negative angle mill- ing cutters. rake in. Angles-same above Feed per min horsepower with increasing number passes. Use deg. lead angle calls for increase horsepower immediately after the first pass. This likewise true for the deg. lead angle, the and the deg. indicated the curves. The most striking characteristic these curves the fact that there deg. lead angle until just prior the breakdown the tip. The power spindle motor Cutter data: Solid carbide inserts 205 36.75 in. per Chip load per tooth cs ©. Width cut, inches 56—THE IRON AGE, June 22, 1944 then increased from hp. Cutter life tests are summarized the accompanying table. The tabuia- tion largely self-explanatory but deserving the following comment: will noted that both brazed and wedged type face mills are included these tests. Without exception, the wedged type cutters show from 100 300 per cent increase total cubic inches metal removed per grind. The note the bottom the Relation- ship between width cut and spindle horsepower input. that these cut- ters were operated the point where reasonable regrind was necessary and not complete tip breakdown. indicates tabulation This information not presented being entirely conclusive, for con- siderable additional experimental and production experience necessary, but certainly the very definitely the benefits the wedge tip whose original strength brazed tips. There every reason believe from these results that laboratory tests indicating tion per cent carbide strength due brazing, hold true the pro- duction line. This conservative state- ment regarding advantages wedge tips versus brazed tips does not, course, include such obvious ad- vantage the lower cost recon- ditioning. Conclusions Carbide milling steel not only production line. This does not mean that all operations will the future converted from high speed steel cutters carbide tipped cutters. In- dications exist, however, majority steel milling operations will performed with carbide. Considerable experimental work re- mains done regarding optimum angles. Present indications point the advantageous use combina- tion deg. negative rake and deg. negative helix for mill- milling operations. slotting, definite results over long production runs in- dicate that deg. helix and deg. negative rake represents com- bination remarkably effective the milling different workpieces. The relationship diameter and face width workpiece important. From the above data, obvious that this relationship should the ratio approxi- mately larger ratio results disastrous entrance angle, which lessens cutter life; smaller ratio re- sults lessened cutter life due pro- longed contact carbide tip with workpiece. This may also due chip confinement when the arc cut- ting ranges from 150 180 deg. This latter effect can apparently elimi- nated increasing the peripheral speed which assists throwing the chips clear. may also noted that with increase the peripheral speed, the chip load reduced and adv dial use pie red the tre ing cia jec thi this may assist eliminating the dis- advantages large workpiece width compared with the cutter diameter. There are definite indications that carbide tipped face mill cannot used confined cut where the arc contact between the tip and work- piece 180 deg. Adequate chip clearance can provided for such operation using fly cutter, very coarse pitch cutter radically reducing the chip load increasing the peripheral speed above. brazed tip cutters are used, ex- treme care must exercised both the brazing and the grinding. Cold treatment helpful relieving braz- ing strains shown appre- ciable increase cutter life when brazed carbide tipped cutters are sub- jected cold treatment 120 deg. below zero for hr. Results thus far obtained with solid wedged carbide blanks both slotting and face mill cutter bodies definitely point the advantages this type construction. The results are apparent not only increased cutter life, much 200 300 per pindle horsepower input BHN Feed Speed- Number pieces cut life tests showing the number workpieces cut and the spindle horsepower input for various lead bevel angles. cent, but also reduced cost cut- ter maintenance. The wedged type cutter can easily adjusted for suc- cessful grindings; broken blade can readjusted and the cutter ground and placed back service within CUTTER LIFE TESTS few hours. broken tip brazed cutter results the cutter being out use for least hr.; the braz- ing necessitates regrinding the bore and frequently the spindle nose recess. NEGATIVE ANGLE MILLING CUTTERS SIZE MATERIAL CUTTER DATA WORKPIECE OPERATING CONDITIONS RESULTS CU.IN 185 ALL CUTTERS WERE FACE MILLS AND WERE RUN SUCH POINT REQUIRING REASONABLE REGRIND THE IRON AGE, June 22, 558.0 405.0 0.63 349.) 0.92 | g | | | ea | | re | in re n- m a, j- Continuous Heat Treatment Aluminum Herein are construction and operating data for what prob- ably the largest and most fully automatic unit used aluminum heat treating the aircraft industry. The experience gained will likely prove value future efforts refine and simplify alum- inum heat treating. automatic heat treating fur- nace, designed approx- imate continuous operation, being used the Texas Division North American Aviation, Inc. processing aluminum parts going in- Liberator bombers. This furnace (built North American design specifications the Despatch Fur- nace Co.) probably the largest and most fully automatic unit used alu- 58—THE IRON AGE, June 22, 1944 minum heat treating the aircraft industry. The operation the furnace briefly follows: Parallel conveyor chains, running guides along the floor tunnel- like heating chamber, carry racks aluminum parts from loading posi- tion into the furnace. The conveyor stops; the entrance door closes; and the conveyor remains ° ° LAWS Assistant Process Engineer, Texas Divi- North American Aviation, Inc. Dallas rest for predetermined interval. During this time, another load placed racks just outside the en- trance door. When the predetermined waiting time has elapsed, warning bell rings, the doors (both entrance and exit) open and the conveyor moves forward distance just sufficient bring the second load into the heat- ing chamber. The doors again close soon the conveyor comes rest. this manner, two five loads are moved into the heating chamber before the first load reaches the exit door. the first load leaves the fur- nace, enters quenching chamber. water valve automatically opens chamber from the unloading end, showing how the un- loading platform has been lengthened care for long mate- rial. The operator turning which lifts the load off the conveyor and moves out the end the quench chamber. This facil- itates unloading long parts. side quen and retu are the com ft. the and are and out the: pos ele through spray nozzles that line the side walls, top and bottom this “fog” chamber. After suitable quenching time, the water valve closes and the discharge from the pumps returned lines leading water- cooling towers. When the load reaches the end the quenching chamber, the parts are, removed from the racks, and the racks are wheeled back the loading end the furnace. Except for loading and unloading, the furnace completely automatic. The ft. heating chamber will ac- commodate loads ft. wide and ft. high. Electrically heated air forced into this tunnel-like chamber through ports the side walls near the floor and passes upward through and around the load checkerboard louvres the ceiling. These louvres are adjustable that areas high and low temperature may “ironed out” opening closing some these closely-spaced ports. The air heated four Nichrome elements, pair elements being situated top and near each end the heating chamber. The elements the loading end are 140 and kw. capacity and those the exit end are 100 and kw. capacity. Switches are provided that make possible use any combination elements. During periods idleness, potentiometer pyrometers, which record the tempera- ture the furnace atmosphere either end the heating chamber and switch the heating elements and off main- tain the desired tem- perature. The auto- matic control circuit adjusted mak- ing settings elec- shown the the temperature may maintained using only one element each unit without putting excessive loads the current supply. The fans that circulate air through the heating elements and the heating chamber have rated capacities 10,- 500 and 8,000 cu. ft. per min. 1000 Airflow switches are provided for turning off the heating elements the event fan failure and, course, over-heating switches are incorpor- ated the heating element circuits. Temperature controlled between the specification limits 910 deg. and 930 deg. two potentiometer ing) which are connected with ther- mocouples situated near each end the heating chamber. These controls are the off-on type and are sufficiently sensitive maintain the temperature between about 915 deg. and 925 deg. The “cold” and “hot” areas the heating chambers, except for cool zones extending ft. inward from the doors, have been brought within deg. the general average ad- justments the louvres. The quenching chamber the orig- inal design was ft. long and con- tained 384 nozzles. permit the quenching loads, this “quencher” was lengthened North American ft., and the piping was redesigned accommodate nozzles with larger passages. The present quenching chamber contains 405 noz- zles design that less easily clogged, but produces dense fog spray that essential rapid and even quenching. Water supplied the nozzles two 325-ft. head centrifugal pumps rate 225 gal. per min. When the automatic valve turns off the water the quenching chamber, the pumps force the water through pressure relief valve and begin circulating through cooling towers. The use circulating system and cooling tow- ers necessitated the temperature the plant water (90 deg. F.) which obtained from company wells. The same circulating system supplies the quenching chambers two other alu- minum heat treating furnace. The automatic control circuit ad- justed making settings four electrical timers. The first timer con- trols the heating time metering the interval between movements the conveyor. The second timer adjusts the conveyor movement the length load metering the time during which the conveyor motor energized. The third timer the start quench closing contact which opens water valve after the convey- motor has run for preselected interval. The fourth timer controls the duration quenching closing THE IRON AGE, June 22, al. yes at- st. xit er. the water valve after preselected quenching interval. Those familiar with aluminum proc- essing will recognize the unconven- tionality this “robot” furnace. Or- dinarily, the heating chambers air furnaces not exceed ft. length and the furnaces are designed heat treat one load time. Parts are customarily hung racks that are designed fill the heating chamber. The furnace door opened hand-operated air valve and two three men push the loaded rack along track which guides into the heat- ing chamber. Loads are usually ex- tracted from the furnace manual- controlled mechanisms. The advantages automatic oper- ation are manifest. Fewer men are needed operate the equipment and stricter control over heating time and the beginning quenching can maintained. The advantages long heating chamber built around conveyor are twofold. the first place, the long stringers used the B-24 bombers can processed with ease the 40- ft