The Iron Age 1940-11-21: Vol 146 Iss 21

NOVEMBER 21, 1940 VOL. 146 NO. VAN DEVENTER President and Editor BAUR Vice-President and General Manager Managing Editor News Editor Technical Editor Machine Tool Associate Associate Editor Editor Editor Art Editor Editor Emeritus Washington Editors MOFFETT JAMES ELLIS Resident District Editors CAMPBELL HERMAN KLEIN Pittsburgh Chicago Cleveland Detroit Editorial Correspondents DEARING ROBERT McINTOSH Buffalo Cincinnati FRAZAR CHARLES POST Boston Son HUGH SHARP Milwaukee SANDERSON Toronto, Ontario JOHN McCUNE Birmingham ROY EDMONDS St. Louis LEROY ALLISON Newark, Editorial Making America Technical Articles Industrial Controlled Atmospheres X-Raying Airplane Parts Automatically Tri-Clad and New Motor Sizes Salt Bath Heating for Forging ....................... Stainless Steel Deep Drawing and Spinning Reinforcing Bar Bending Machine ................... Hydraulic Press Opens New Plant Mt. Gilead Feature Reports News and Market Reports News Industry Machine Tool Activity 114 Personals 100 Non-Ferrous Market Metal Working Activity 103 Construction 118 Comparison Prices 104 Iron and Steel Prices 120 The Industrial Pace 106 Warehouse Prices District Market Reports 108 Sales Possibilities Fatigue Free Industrial Literature Products Advertised Index Advertisers Copyright, 1940, Chilton Company DIX, Manager Reader Service Advertising Staff Chilton Bldg., Philade!phia Hottenstein, 1012 Otis Bldg., Chicago Leonard, 100 East 42nd New York Peirce Lewis, 7310 Woodward Ave., Detroit Ober, 100 East 42nd St., New York Warren, Box 81, Hartford, Conn. Don Harner, 1595 Pacific Avenue, Long Beach, Cal. Member, Audit Bureau Circulations Member, Associated Business Papers Indexed the Industrial Arts Pub- lished every Thursday. Subscription Price: United States and Possessions, Mexico, Cuba, Canada, $8.50; Foreign, $12.00 year. Single copy, cents. Owned and Published CHILTON COMPANY Publication Editorial and Office Executive Offices Chestnut and 5éth Sts., 100 East 42nd St., Philadelphia, Pa. New York, U.S.A. OFFICERS AND DIRECTORS MUSSELMAN, President JOS. HILDRETH, Vice-President GEORGE GRIFFITHS, Vice-President EVERIT TERHUNE, Vice-President VAN DEVENTER, Vice-President BAUR, Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JULIAN CHASE, THOMAS KANE, HARRY DUFFY CHARLES HEALE keg | aN: _ (As + YERSON UNIQUE PRODUCTS INCLUDE: Structurals Bars Plates (15 kinds) Sheets (25 kinds) Strip Steel Alloy Tool Steels Stainless Shafting Mech. Tubing Boiler Tubes Welding Rod Babbitt, Solder Reinforcing Nails, Rivets, 30—THE AGE, November 1940 Joseph Ryerson Son, Plants at: Chicago, Milwaukee, St. Louis, Cincinnati, Detroit, Buffalo, Cleveland, Boston, Philadelphia, Jersey City. STEELS 4 4} ‘ ¥ diate Making America Strong cannot sharpen chisel, axe sword without submitting the punishing action abrasive. the same token, you cannot refine National ideals ideas unless you submit them the grindstone criticism the crucible courageous and sincere opposi- tion. line with this general thought, seems that the unsuccessful opposition, the late political campaign, has indeed been eminently successful teaching America one outstanding truth. this: “Only the productive can strong, and only the strong can free.” we, regardless party political ancestry, can absorb this truth and resolve act upon it, the battle 1940 will not have been fought vain. Many had more less forgotten this truth the abnormal years the last decade. Many have become accustomed rides” the endeavor get the most for the least the scramble, the tune “devil take the had forgotten that when the devil catches with the tail end the procession, not long before works his way the front it. “Only the productive can look back through his- tory, how often can find that truth set forth, and exemplified. The parable the fig tree and the buried talents; the example Mother Nature the fructification the animal and the vegetable kingdoms; NOV. 21, 1940 all these emphasize the essential law survival—productivity. our own cherished land freedom, productivity has been the keynote our outstanding progress. More goods for more people. ESTABLISHED What times have produced more this that than could for 1855 the time consume. Are not surplusses better than deficits? can find ways deal with too much. But show the man who can find the way with too little. “Only the productive can And need strong America. need, with our shorter working hours, larger produc- tivity per man for the products both peace and war than that Germany Italy Japan and their satellite nations. And all energies today, regardless political belief, are bent the direction attaining it. Attaining keep free for the strong can free.” Productivity. That the challenge facing every American today, whether captain industry rawest recruit our labor ranks. And put the test, what does this mean? means that each and every one must apply ourselves more diligently; that each must strive every day produce little more and little better than have done previously, the end that America can and shall become strong and therefore remain free. get about it. ¥ ay I inks. wet - | | Saal % / The new leaded steel developed NOTE: inland has licensed many steel makers America abroad make this product under its patents. ap qd kn, > Wp Ly at On On Sy Xtra, “lees, Loy. 4, Sheets Strip Tin Plate Bars Piates Floor Piling Structurals Rails Track Accessories Reinforcing HIS the first section four-part article describ- ing industrial controlled at- mospheres and methods for heat treating high carbon, tool and alloy steels decar- burization-free Herein, attention directed determining the efficiency controlled atmosphere, and the air-gas ratio method controlled atmospheres. heat treatment high car- bon and tool steels controlled atmospheres not entirely new. However, the perfection atmosphere control methods and furnace design bright scale-free harden such steels free from decarburization carbur- ization recent new development that has taken place the last few years. Atmosphere control, protec- tive heat treating, has been some degree another long tools and high carbon spring parts have been made and hardened. Atmospheres The old timers through practical ex- perience learned that the adjustment the flame gas-fired furnace had important bearing the surface condition both from the point view hardness and scale. They soon learned their disappointment, how- ever, that more new alloys were de- veloped this method atmosphere control became more limited and more detriment than benefit. over- come this difficulty, methods pack hardening carbonaceous material cast iron chips coating the tool with borax some other protective film were devised, but these methods were messy, makeshift, and not entire- satisfactory for all tool steels and impracticable for production harden- ing high carbon steel parts. Such methods, however, were probably high- suggestive later successful devel- opments the carbonaceous muffle block and salt bath methods for heat treating high speed, tool steels. After the development the elec- tric furnace, its use application the hardening high- carbon and tool steels depended entire- upon gaseous atmosphere pre- vent oxidation and decarburization. meet this end, the same principle that the practical heat treaters found work the opened, gas-fired furnace was applied. ratio city natu- ral gas and air was burnt and the products combustion were passed into the furnace chamber. Inasmuch the heat combustion the fuel gas was not needed, wider range dif- ferent gases the products com- bustion could obtained using various gas-air ratio though this development proved valuable contribution protective hardening, oxidation and decarburiza- tion were not entirely eliminated, but were greatly reduced many types steels that could not handled the opened, gas-fired furnace. This at- mosphere was not, however, beneficial all tool steels. The high-carbon high-chromium types, for example, could not heat treated without ex- cessive scale and decarburization, and the method pack hardening still had resorted to. The demands for the use the high carbon high grew such extent that more efficient method than pack hardening for protective heat treating was neces- THE IRON AGE, November ; ) ~ | | = | ae i 2 | rcing a IS. straight high-carbon tool steel hard- 2—Manganese non-deforming tool steel ened 1450 deg. 2.7 per cent O.— 8.3 CO.—17.0 atmosphere for hr. and water quenched. Shows visual decarburiza- tion. Magnification 100 diameters. Nital etchant. Drawn 700 deg. Rockwell hardness quenched 66-67C. sary. The method producing pro tective atmosphere cracking liquid hydrocarbon was devised and found satisfactory for scale-free, decarb-free hardening the high carbon-high chromium steels. This method and the gas-air ratio method became the stand- ard methods atmosphere control for high carbon and tool steels. Because the complexity the problem and the lack information and knowledge the gas-steel reactions, further de- velopments were not made for quite few years come. The developments bright anneal- ing low-carbon sheet and strip and bright brazing made metallurgists, heat treaters, and tool and production men even more atmosphere conscious and desirous bright harden high carbon Atmospheres Steel Treating,” Gillett, Metals and loys, Vol. August, 1935; September, 1935; October, 1935, and November, 1935. Treating Steels, Koebel, thesis for M.S. metallurgical engineering, Ohio State University, 1936. *“Grain Size and Its Influence Sur- Rowland and Upthegrove, A.S.M. con- vention, Chicago, Sept. 1935. 34—THE IRON AGE, November and tool steels order take advan- tage the savings pickling, and grinding costs. The at- mospheres used for bright annealing low-carbon strip and bright brazing were found excessively decar- high carbon alloy too! steels. Research work controlled atmospheres and studies the gas- steel reactions were made and Slowter and These studies pointed out the types gases and gas mixtures that must avoided, the type types gas mix- tures that would needed, complexity the problem obtaining such gases economically. Further re- search and development work were soon carried out several progressive furnace manufacturers, and bright scale-free hardening high-carbon and tool steels free from decarburiza- tion carburization soon became reality instead dream. Inasmuch the recent new devel- opments constitute only about cent the controlled atmosphere equipment now used industry for heat treating high carbon tool hardened 1450 deg. 2.7 per cent O.— 8.3 CO.—17.0 atmosphere for hr. and oil quenched. Shows visual decarburization. Magnification 100 diameters. Nital etchant. Drawn 700 deg. Rockwell hardness quenched 64- 64.5C. steels, the older methods will first discussed order show what steels these methods are best suited for, the limitations the equipment, and the advantages and savings one might ex- pect replacing this equipment with the recent new developments. Efficiency Atmosphere Perhaps the most logical thing before discussing and comparing the efficiencies controlled atmospheres discuss the various methods used for testing and evaluating atmos- phere. The methods that have been used for determining decarburization carburization are follows: (1) Hardness test. (2) Photomicrograph. (3) Analysis consecutive cuts. (4) Change weight. Test: The hardness test the most commonly used method check for decarburization carbu- rization chiefly because first, almost everyone with softness carburization with hardness; second, the. hardness test the easiest make; and third, prac- 3—Silicon-manganese too! steel hardened 1550 deg. 2.7 per cent O.—8.3 quenched. Shows slight decarburization. Magnifi- cation 100 diameters. Nital etchant. Drawn 700 deg. Rockwell hardness quenched 59-62C. tically all heat treating have means for making this test. The hardness test is, however, the least scientific and the least accurate the four methods the first place. this test does not give quantitative data for plotting the results compare one atmosphere with another, and second place other factors, such quenching rate and temperature have bearing the hardness the steel, and unless the steel carburized, there always doubt the real cause low value, especial- when the hardness reading only point two below the maximum hard- ness value expected. The author has found that very possible for steel become decar- burized extent influence the resistance, but not extent show the hardness tester. This can happen high carbon steels when the rate diffusion carbon from the core the surface the steel keeps apace nearly apace with the rate decarburization, loss car- bon, from the surface the the this case, the sur- IG. chisel tool steel hardened 1750 deg. 2.7 per cent O.—8.3 atmosphere for hr. and oil quenched. Shows only slight decarburization, but steel was actually badly decarburized. Magnifica- tion 100 diameters. Nital etchant. Drawn 700 deg. hardness quenched 40-41C. face does not become totally rized and although amount carbon has been lost the surface, there still enough present give high reading the hardness tester. example, the surface high carbon-high chromium steel the per cent carbon, per cent chro- mium type may decarburized down 1.5 per cent carbon type and still capable obtaining the maximum hardness expected from the 2.5 pet cent steel. Likewise, water-hard- having carbon content 1.2 per cent may decarburized down 0.80 0.90 per cent and still obtain hard ness reading equivalent the mum value the 1.2 per cent carbon steel. One should remember that the Rockwell any other hardness tester gives relative figure indicating the hardness the steel tested and that this figure does not indicate the wear resistance. The hardness test may thought and used rough, qualitative field test. Such simple check and test atmosphere comes very handy setting and making preliminary adjustment generator atmosphere equipment and atmosphere furnaces. When the point reached where difference can determined the hardness value, then more sensitive and accurate test can made. good procedure use checking for de- carburization Rockwell superficial tester well the standard Rockwell tester. Then means conversion table, the value values obtained various weights the superficial tester are transposed the Rockwell scale. These values are compared with the value obtained from Rockwell tester using the scale. lower transposed reading indicates decarburization while trans- posed reading indicates carburization. This method makes the hardness test somewhat more accurate eliminat- ing the doubt and guesswork speci- mens that are only point two over under the maximum hardness value the steel. The use two machines not, however, make the method 7 THE IRON AGE, November 1940—35 the cases where decarbu- rization carburization take place such degree not affect the hardness the steel. The method checking decarburization carburiza- tion the microscope has the advan- tage giving one picture what has taken place. This method does not, however, always give true picture show the total amount depth decarburization. The free- ferrite laver which one usually looks for decarburized steel may only small percentage the total depth decarburization. some types steels, depending the carbon and takes place without showing rite below that area can detected readily while others quite cult impossible even when the hard- ened samples are drawn from 600 deg. 1000 deg. obtain secondary troostitic sorbitic structure show the decarburization carburization more readily than can seen the hardened specimens having austen- itic-martensitic mary troostitic structure. structure for tracing the total depth decarburization, especially straight- carbon steels, that obtained full annealing, e., heating AC; and cooling very ously this method only practical checking the effect the atmosphere annealing and not hardening various time periods. The disadvantages the use the microscope may summarized first, not sensitive enough check for small amounts show the total depth and second, does not give data for plotting curves com- pare one atmosphere with third, requires. special equipment; fourth, requires considerable time and technique prepare the specimen and photograph the results. other hand, the microscope may used alternative method add further data used the cases where the accuracy the other meth- ods fail cannot used. ANALYSIS CONSECUTIVE The method checking decarburiza- tion carburization analyzing con- secutive cuts from the diameter the specimen has been used Row- Paimer, Vol. Nos. 14, and 16. 5“An Experimental Study Gases for Controlled Atmospheres the Heat Treat- ment Steel,” Slowter and Gonser, Metals and Alloys, June, 1937; also, “Comparative Effects Con- trolled Atmospheres on Alloy and Carbon Metals and Alloys, February and March, 1938. 36—THE IRON AGE, November 1940 land and Clair and many others. This meth- carried out using specimen in, long turned down after normal- remove any decarburization and provide original concentric turnings. the speci- men has been heat treated the atmos- phere for the desired length time, consecutive cuts 0.003 in. are taken and carbon analysis made each turning until the set reached having the same carbon content the orig- inal specimen. the hardened from the atmosphere being atmosphere obtain machinability be- fore the cuts can made for analyz- ing. This method has the advantage giving complete picture what has taken place. not only shows the total amount carbon lost gained, but also gives the gradient de- carburization carburization. Such data can used for plotting various curves study the efficiency the atmosphere and compare with other atmospheres. Another dis- tinctive advantage the method that accurate results can obtained under conditions that limit the use the other three methods. The biggest drawback and tage the use the method the IG. 5—High carbon-high chromium hardened 1750 deg. 2.7 per cent O.—8.3 atmosphere for hr. and quenched Shows bad decarburization. Note layer scale. Magnification 100 diameters. etchant. Drawn 700 deg. Rock- well hardness quenched 43-55C. A special equipment, the expense, the la- bor and the time involved making the test. Another disadvantage that hardened specimens must annealed before concentric cuts can made. Unless the annealing carried out laboratory furnace using atmos- phere that definitely known neutral, decarburization carburiza- tion will occur and this will introduce error the results. CHANGE The change weight method was first and later Slowter and scientific means for de- termining decarburization rization studies controlled atmos- pheres. This test made accurately weighing the steel sample grams the fourth decimal place (to 0.1 mg.) chemical balance. the sam- ple has been heat treated the atmos- phere tested for the desired length time, then reweighed. loss weight represents decarburiza- tion, while gain weight represents carburization. order that the re- sults may put common basis for the comparison one sample with another and one atmosphere with an- other, the change weight grams divided the total area the sam- ple square centimeters. This then gives the loss gain per square centi- meter steel surface submitted the atmosphere for test. the sample not scaled oxidized, the loss decarburization, and gain weight rization. convenience sake plot- ting the results, the loss gain weight per square centimeter multi- plied 100,000 move the decimal place over obtain whole number. The size the sample should se- lected that its weight will not too great affect the sensitivity the balance. round bar used, in. diameter in. length con- venient size use for the test. The sample should machined ished remove any decarburization formed the manufacture the steel and also provide smooth, bright surface determine the effect the brightness the steel. Care should taken that the sample washed with solvent, such alcohol, ether, carbon tetrachloride and thoroughly dried before weighing and reweigh- ing. The change weight method for determining decarburization burization extremely accurate and sensitive (more than any the IG. high speed tool steel decarbur- ized 1350 deg. preheat furnace. Magnification 100 diameters. Nital etchant. Hardened phere show ef- fects decarburi- zation. 14 other three methods and easy and convenient make there good chemical balance hand. Ob- viously this method cannot applied the testing atmospheres that scale oxidize the steel. The change weight method definitely limited bright scale-free atmospheres. stain, temper color, very light oxi- dation will not affect the results any serious noticeable degree, and this method safe use long defi- nite scale oxidation has not formed. \lso caution should exercised applying this test check the decar- burizing carburizing effects salt baths. Most salt baths dissolve away the steel surface, and such condition would lead very erroneous results. interpretation the results ob- tained the change weight method somewhat puzzling those who are not accustomed the method those who wish think decarbu- rization carburization ferms depth hardness. The best way interpret the results and determine the efficiency controlled atm the change weight method run one set samples the proper hardening temperature and the av- erage time required for heat treating the average run work made the steel the samples being tested; then second set samples should run using the same temperatures the first set, but leaving the samples sub- mitted the atmosphere two four times long. The results should plotted using the change weight ordinate and the heat treating time abscissa. curve drawn for each set samples connecting the two points. The closer the curve the zero, change weight ordinate, the better the atmosphere for that particular steel. The efficiency atmosphere for tool high-carbon steels determined the number curves that fall very close and also parallel the zero ordinate axis. The theoretical allowable any steel may set gm. per sq. cm. change weight. This limit has been established making many tests various types steels these the other methods. gm. per sq. em. too small detect the use the microscope any type steel. The practical allowable limit the change weight for steel depends upon its thickness and its carbon alloy content. example, change weight —0.00050 gm. per sq. cm. will affect piece 0.020-in. thick, 0.70 per cent carbon steel such degree that will lose most its hardness and spring properties, while the same change weight the same type steel having thickness in. may not noticeably affect the maximum hardness. This due the fact that the heavier section the carbon diffuses from the center the surface, keeping pace with the rate keep the surface carbon content enough obtain the maximum hard- ness. The same amount carbon lost beth cases, but the thin stock more materially affected. Thus thin stock, the practical maximum allowable limit the change weight would the same the theoretical +0.00020 gm. per sq. cm. heavier sections and tool steels this limit may far —0.00050 gm. per sq. cm. without affecting the maximum hardness mind, however, that loss carbon may materially affect the wear resis- tance even though does not affect the maximum hardness. Controlled Atmosphere Used The methods protective heat treating used during the past and the present time but not including THE IRON AGE, November 1940—37 = | the recent new developments are (1) ratio method. (2) Pack hardening. (3) Carbonaceous muffle blocks. (4) Cracking liquid hydrocarbon. order that the chemistry and chemical reaction can discussed more readily, the chemical symbols will used. These symbols and for- mulas are follows: CO, Carbon dioxide. Carbon monoxide. Hydrogen. H,O Water water vapor. CH, Methane. C,H, Ethane. H,S Hydrogen sulphide. Air-Gas Ratio Method The method producing protec- tive atmosphere means burning definite ratio air gas has been employed ever since gas fired furnaces were used for the heat treatment high carbon and tool heat treaters employing gas furnace which the steel heat treated was exposed the products com- bustion soon learned that good bad results could obtained turn valve. the use such furnaces, the proper adjustment the flame be- came important phase the art heat treating. When the electric nace was developed, this method controlled atmosphere was applied overcome the bad scaling and decar- burizing properties air. Such fur- naces are equipped with flow gages measure and ratio the air and gas which then burnt separate com- partment beneath the vestibule the doorway the furnace. The products combustion are then passed through slot the doorway vesti- bule, through the furnace chamber, and exit through vent the rear the furnace top. furnaces are equipped with valves operated auto- matically from the door lever burn curtain gas the doorway vesti- bule whenever the door opened air from entering the furnace cham- ber. Until recent years this has been one the chief means producing con- trolled atmosphere for the heat treat- ment tools. The use this atmos- phere for decarburization-free heat treatment high carbon steels quite limited but not impos- sible certain steels, provided light scale can permitted. impos- sible, however, simultaneously ob- tain scale-free and decarburization- 38—THE IRON AGE, November 1940 free hardening. The scale can, how- not allowing the steel soak the hardening temperature. Although there are many analyses that there really only one air-gas ratio setting that can applied, and only limited number steels, for de- carburization-free hardening. This ratio will produce atmosphere con- taining from per cent excess the combusted gas with the remain- ing constituents CO,, H,O, and typical analysis produced burn- ing city gas with air for decarburiza- tion-free hardening high-carbon and tool steels having hardening tem- peratures not greater than 1600 deg. follows: 2.70 per cent O,, 8.30 per cent CO,, per cent H,O and per cent The small percentage excess portant subdue the decarburizing properties CO, and H,O. The ad- dition third decarburizing gas offset the effects two others seems but works out satisfactorily. The theory such atmosphere may ex- plained the basis that the slight excess forms impervious type oxide scale that acts protective coating. The CO, and constitu- ents are also oxidizing gases, but these seem oxidize the carbon the steel selectively over the iron, thus producing only half-hearted, spongy tvpe iron oxide scale with decar- steel layer beneath it. The oxide film produced the seems act barrier prevent the dif- fusion the carbon the steel the surface and thus prevents the oxida- tion the carbon, decarburization, from faster rate than the oxidation the iron. The only decarburization below 1600 that the oxide the film scale itself. Above 1600 deg. this phenomenon longer exists; the decarburization begins proceed faster rate than the scaling, produc- ing soft skin beneath the scale. The best results are obtained high-carbon water-hardening tool steel manganese oil-hardening tool steel having hardening temperatures from 1375 deg. 1475 deg. these temperatures only very thin film scale produced, especially the steel quenched when reaches the hard- ening temperature and not allowed soak. Photomicrographs Figs. and show that high-carbon water-hardening tool steel man- ganese oil-hardening tool steel can heat treated free from visual decar- burization even when soaked for hr. the hardening temperature. This also true silicon tool steel, Fig. heat treated 1550 deg. and soaked for hr. this temperature, however, the steel begins pit and scale quite appreciable extent and pro- longed soaking must avoided. Above temperature 1600 deg. this at- mosphere longer useful; both bad scaling and decarburization take place. This shown the photo- micrographs Figs. and tung- sten alloy chisel steel and high car- bon-high chromium tool steel treated 1750 deg. One the biggest mistakes made many users this type atmos- phere adjust the air-gas ratio that scale-free hardening can ap- proached obtained. Any air-gas ratio from one that will produce sooty atmosphere down O,) will produce decarburization. tool work—if one the two evils scale decarburization must accom- pany hardening—it much better produce light scale that must ground off before the tool can put into service, than produce scale-free tool that may into service without grind and thus with soft skin decarburized surface. the case high speed steels, air-gas ratio used that will produce “reducing” atmosphere containing much possible without becoming sooty. Although this composition decarburizing and scal- ing all high speed steels, the least decarburizing that can obtained from the air-gas ratio atmosphere. Tools heat treated such atmosphere cannot put into ser- vice without grind soft skin always present some degree. The amount decarburization will depend upon the type steel and the time re- quired for hardening. The 8.0 9.0 per cent molybdenum type high speed steels cannot heat treated this type atmosphere; the depth decarburization becomes great that its removal grinding becomes most impracticable. The atmosphere used heating furnace for high speed steels just important toward decarbu rization-free hardening the atmos- phere used the hardening furnace. High speed steels will decarburize temperatures low 1350 deg. The author experienced this when making investigation determine the cause soft, high speed, form cutters. The cutters were found to decarburized 0.035 in., practical- through the cutting edge. This can seen the photomicrograph Fig. The cause this decarburization was traced down the preheating fur- nace. The cutters were preheated the front zone air-gas ratio type atmosphere furnace tempera- ture between 1300 deg. and 1400 deg. The atmosphere this furnace oxidizing, but the time when this particular batch cutters heated, the reducing valve stuck the air line, and the atmosphere fluctuated between neutral per cent and per cent CO) and slightly reduc- ing one. the total time the cutters remained the preheat furnace was not obtainable, but inas- much the cutters were rehardened several times, the heat mated the time between and hr. The cutters were hardened the high temperature carbonaceous muffle block furnace. Cutters hardened this furnace without preheat showed trace decarburization. The air-gas ratio for preheating should either set give atmos- phere containing about per cent ex- cess oxygen one that very “re- just short being sooty. Many prefer the oxidizing oxidize the steel slightly pro- tect against the decarburizing action the high heat. molybdenum high speed steel used, the preheating atmosphere should the reducing one not de-molybdenumize the steel. Any atmosphere obtained from the air-gas ratio method decarbu- rizing some degree another any high speed steel, and better atmos- phere desired for hardening totally free from decarburization that may not permit grinding. Ed. Note:—In the second section next week the author describes pack hardening, the necessity for better atmos- phere heat treatment high carbon and tool steels, etc. Automatic X-Raying 5000 Parts Per Day NSTALLATION new, fully automatic X-ray machine that will photograph 5000 average parts per day has been completed the Triplett Barton laboratories the Lockheed factory, Burbank, Cal. Representing complete departure from equipment previously used, both speed operation and design, this machine regarded one the answers the stepping aircraft production 10, thousand planes year. All the high voltage X-ray equip- ment housed black and chro- mium-trimmed cabinet ft. high and ft. square. Projecting from the bot- tom the cabinet both sides are chromium-covered braces for the con- veyor table that works shuttle fash ion from one side the other. The cabinet and table are lined with 1500 lb. lead completely shield the op- from the high voltage X-rays. The focal spot the machine ex- tremely small order obtain radio- graphs that will show smallest defects, yet parts any length ft., and not more than ft. diameter can handled. The portion the cabinet housing the X-ray tube and transformer works tric lift that raises above the table which the parts X-rayed are placed. When the photographic con- trol turned on, the cabinet low- ered place and held there until the raised automatically and table, with its set-up parts, pulled into position for the next photograph, the extension with the parts just photo- graphed being shifted the opposite side the cabinet. The parts are either replaced with new set-up rear- ranged for the second third view. whichever called for. The timing. together with the period X-ray ex- posure desired, can pre-set the operator. The rapidity with which parts can X-rayed dependent the skill the operator. During rush periods two more men may kept busy. safety bar the under edge the cabinet, sensitive that will react the slightest pressure, will stop the machine any point during the time the cabinet being raised position. All parts the ma- chine are jig fabricated ability. Some them were made Spencer Morris and the Var- num Engine Co., Los Angeles. tubes and transformers Triplett Barton’s own shops. The X-ray inspection was started the Lock- heed plant five years ago. first was re- garded purely ex- periment, and outset only per cent Experience proved, however. that insurance against structural fail- X-raying these parts. also re- vealed that construction expense could cut and time saved this proce- dure. The rejection parts from single foundry shipment will sometimes run into the hundreds. These flaws rule are caused the faulty pouring the parts are made. wey oe Ke: ‘ 7 | UTSTANDING mechanical and are found entire line completely new polyphase induction motors just announced General Co. Known the Tri-Clad motor and representing one the most extensive product the his tory the company, has called for many new methods and new materia!s ratings, the motor features modern streamlined appearance, more com- plete protection than heretofore avail- able except especially enclosed ma- chines, major advances insulation, and improved bearing de- sign and lubricating arrangements. the same time, the line retains the cast aluminum rotor, pressure relief system greasing for motors and other proven features, appearance the motor frame has simple surfaces with few recesses projections. Box type frame made cast iron new foundry tech- nique that assures concentricity the core and hence the most effective dis- tribution the metal. The end shields are designed match the frame and are enclosed above the center line thus offering greater degree protection against the entrance falling liquid particles than existed previous open motor designs. Sleeve bearings ball bearings are interchangeable for the same frame sizes. Principal feature the sleeve bear- ing design that the length much 40—THE IRON AGE, November 1940 shorter than previous conventional practice—averaging 1.5 times the di- The design intended overcome the concentration high unit bearing pressures the end the bearing resulting from shaft tions under load. using shorter bearing length, the deflection the shaft inside the bearing can main- tained value less than the thickness the oil film. assure that the oil film maintained over all parts the bearing lining under heavy load, spiral type grooving has been de- veloped give the thorough oil distribution worst operating conditions. com- plete sleeve bearing utilizes hard tin centrifugally cast into shell. The bearing ported through 360 deg. and locked dust-tight, oil-tight enclosure. The bearings are lubricated oil ring dipping into reservoir. The oil filler gage can located either all frames larger than frame 254, drain plug permits complete draining the bearing housing without tilting the motor. The same assembly shaft and rotor used many popular sizes Thus many sleeve bearing motors may converted ball bearing chang- ing only the end shields, bearings and caps. integrally cast rotor fans draw low velocity air through openings the lower portion each through the use large, smooth air passageways and baffles which control its direction, velocity ri-Clad otors Announced through openings the above the motor feet. Performance the motor has been horsepower outputs are being obtained smaller frame sizes than heretofore. Improvements have been made the silicon steel for the stator laminations, and the air gaps between them have been reduced, largely result the improved bearing design. The greatest gain space saving and electrical characteristics has ob- tained through the use the new General after ten research and now used all ratings eliminate largely the older type paper, cotton coverings, and other fibrous materials thus saving considerably slot space. Abrasion tests have shown enameled magnet wire the ratio about three one. Motor windings are proved synthetic resin varnish and covering coat Glyptal No. 1201 red alkyd-resin material which gives the coils not only neat appearance but also moisture, acid, oil and arc resisting surface. the double end system ventilation, cool air drawn into both ends the motor immediately impinges against the coil extensions, resulting equally low temperature these parts both ends the motor. The motor oper- ates well within the standard deg. temperature rise. The Formex wire itself particularly resistant heat shock which usually manifests ordinary magnet wire cracking the surface due internal strains set during the forming operation. e \ec te oP xed e\e we ° ° | Westinghouse Introduces New = Motor Sizes major change the original motor dimension standards adopted members the National Electrical Manufacturers Association since 1928 was put into Oct. when new frame size, 203, was added and new assignments were small, open horizontal and vertical mo- tors frames 204 and 224. effect the previous horsepower-speed ratings have been reduced one frame size, thus resulting saving weight, space per cent less and per and size. Smaller motors are now cent less space than its prototypes possible because two major improve- the same speed ratings. ments, core iron and insulation. The new NEMA ratings are shown the new 203 frame, the dimensions have been the accompanying table. The pres- are the same for frame 204 except proved until now less motor ent standard mounting dimensions ap- that the maximum overall width the necessary produce the frames 204 and 224 are not feet in. in. less than for power. New synthetics and new cloth changed, although some the other frame 204), and the centerline bolt insulations higher dielectric strength dimensions may slightly. hole foot 234 in. have been developed which permit insulation the same quality form- New NEMA Small Motor Standards erly smaller space. Westinghouse has just completed General Purpose Squirrel Cage Motors broad program small motor redesign Open, Horizontal Continuous Duty, 40° Rise which covers much wider scope 110, 220, 440 and 550 volts, and phase, cycles improvements than are called for the new standards. smaller Horsepower Approximate Speed dimensions and lighter weights called 3500 1750 1150 875 for the new standards will 203 shapes have been Open, cycle motors are satisfactory for operation cycles. designed and new bracing structure Temperature rise will not exceed 50° continuous. gives them more strength although These ratings also apply d.c. motors, 115 230 volts. they are and sleeve bear- Single Phase Motors ings and housings have new type sea dirt which are tar more Volts, Single Phase, cycles* efficient than those used the old motors. motors and ma- Horsepower Approximate Speed chines for smart appearance now de- 1150 manded industry has been met 203 use smooth finish and curved lines 204 All frame corners are rounded. 224 rel cage induction motor which weighs *Ratings changed NEMA standards revision. THE IRON AGE, November Ye wh; th; 4 eq a ; 'ch bo 's Mot e lat, Me, le Ww re) 'Otin off Oct / “Orda, for. h ed Qa Salt Bath Heating for Forging been aroused recently the use Ajax-Hultgren elec- tric salt bath furnace heat bar stock for testing dies forging machines and presses the plant Ajax Mfg. Co., Euclid, Ohio, suburb Cleve- land. The Ajax Mfg. Co. (which has connection with the company making Hultgren furnaces) builds number types hot metal working machines including upsetting forging machines, forging presses and forging rolls. These machines are generally sold equipped with set forging dies which must developed and test- their plant prior shipment. Heretofore has been necessary move these machines test floor with permanently constructed oil type furnace, whereas the salt bath furnace fitted with lift rings that can transferred crane any part the erecting floor where its service required. Bars heated this fur- nace are free from the formation scale, because during heating they are completely immersed the salt bath. Another advantage the fact that the heat absolutely uniform and held whatever close temperature limits are required for the particular forging being produced. Bars in. diameter are being heated the Cleveland minute cycles are employed bars, with in. being heated each bar. With six-position holder the output the furnace thus equiv- alent one heat every min. Other size holders than the six-posi- tion unit can used, course. alloy steel plate, immersed the salt 42—THE IRON AGE, November 1940 IEW new Ajax-Hultgren electric salt bath furnace the plant Ajax Mfg. Co., Cleveland. Operator has removed hot bar from the furnace and about put the forging machine test the die. any length bar desired heated. practice the Cleveland plant bars are only immersed the quired for making the test forgings. merged portion. Taken out the bath, the bar tapped lightly the operator move excess salt and placed adjacent forging machine. While the hot piece being transferred from the furnace the forging machine, the film liquid salt clinging the sur- face maintains protection the sur- face. Two electrodes, closely spaced, are immersed the salt. stirring action obtained. The liquid can seen circulating. The Cleve- land company using Hough- Temperatures can varied, depend- ing the type steel being used, but the Cleveland company uses tem perature around 2200 deg. and when the furnace idling, the tem- perature dropped back around solidify, the furnace kept hr. per day. The furnace cap- able using any number groups electrodes, containing two, three more electrodes per group. low voltage, from volts, obtained means step-down transformer. \lternating current then through the molten salt lying the tween the which heats the the flow current. Any desired the bath may ob- tained. Temperatures are controlled Cleveland installation Leeds Northrup Micromax system. Speed heating dependent only the conductivity the steel. The time required for the bath recover temperature after charge placed very short. More power instantly available and distributed through the bath the automatic stirring action. heavy wall in- sulation around the furnace prevents excessive the absence scale, in- creased die life attained, according Ajax Electric Co., advantages include: grain growth due fast heating cycles; decarburization, selective heating with sharp line between unheated portions, low operating and improved working conditions due the lack excessive heat noxious fumes. The use salt baths heat steel finding favor other directions, There are now many Ajax-Hult- gren salt bath furnaces use for shell nosing, the sizes varying from mm. nent carbide tool some weeks ago announced price reductions approximately per cent. Undoubtedly the time this article print other carbide tool will have followed suit. This terrific drop prices carbide tools will set them without economical equal among metal cutting brought new and closer ratio be- tween initial tool costs and tool costs per unit produced, giving even greater economic appeal carbide cutting tools. large and small, who have hesitated use carbide tools will encouraged now that prices are more line with budget allow- ances. There will demands for ser- vices, demonstrations, and instructions will tax the capacities the carbide manufacturers provide them. Some- body will have wait his turn. This will cause many prospective user carbide tools turn reading mat- ter the subject. may read about stand them because they savor the fundamentals most any principle when comes making carbide tools —well—that’s just like meeting with “new breed pups.” Carbide tools are different because they seem violate all the old established laws metal cutting technique. The new prices carbide tools, will, for the time being, affect only very limited number styles. Vol- mine that. Because this, consum- ers carbide tools will have still make their own tools, that is, buy the carbide blanks and braze them onto Carbide GAYLORD THOMPSON the desired sizes tool shanks. manufacturers carbide tools give very thorough instructions their sales literature the man- ner brazing carbide blanks shanks and also the grinding technique in- volved bring the tool meta! cutting condition. There are numerous other factors that must considered when building carbide tools order obtain the fullest efficiency The field large would practically im- possible for the carbide manufacturers cover every type carbide tool used metal cutting. Special forms and shapes tools involve too many intricacies for other than the fundamental knowledge carbide tools and their performance. almost resolves itself the “make, cut, and learn” method acquiring carbide tooling knowledge. The major consideration bear mind when building carbide tools stability—good solid support for the carbide blank. Vibration poison carbide tools. They'll fracture like hunk chalk. But give them good support and foundation and eat into metal cutting duties with thor- oughbred vigor and stamina. Proper grade and quality have plenty with that, too. Boring bits were considered one Wis. time type tool very detri- mental carbide tips. Carbide sales- steer clear any such tool entanglements and concentrate heavy shanked tools. There was less types boring bars and flybars were, course, designed for high speed steels and little vibration did harm. But the mistake was use carbide tools these types boring bars without due consideration ex- cessive vibrations. Then, too, the cen- terline set-up the high speed steel bits the boring bar was not im- portant with carbide tipped bits. The conventional bar with, for ex- ample, square hole for square tool bit, will have the cutting edge the tool approximately 3/16 in. above center. cross-sectional end view this type bar shown Fig. The circle representing hole illustrates the relation the centerline and the cutting edge the average high speed steel tool bit. Note the negative angle where the work passes over the tool against all laws correct cutting procedures. Clean, smooth cutting results are prac- tically cutting strain denoted the direction the ar- row, has tendency break off the tip the high speed steel tool bit and would the tool were THE IRON AGE, November the M e j | e | > = ‘ent - J 3 AS + Sectional view bar force ¢-, mie" Rake Bit Rake conventional boring bar with high speed steel bit set 3/16 in. above the center the bar produces effect negative rake and cutting force the angle shown. carbide tool would fail this application. carbide tipped. Unless proper angles and rakes are ground the carbide bit, doomed complete failure this type bar. Fig. shows carbide tipped bor- ing bit that was condemned and de- scribed the looking tool.” Machine operators turned with vehement protestations. “It have enough clearance under the cut- ting edge. would drag the they said. Now look how the tool fits into the prescribed circle rep- finish bore. Note the 26-deg. angle necessary provide 6-deg. top rake the tool because its position the conventional type boring bar. And most important all the 7-deg. negative rake front clearance that condemned the tool sight. angle gave such thorough support the cutting edge the carbide that finished bored removing 0.010 in. stock speed 300 ft. per min. and retaining the dia- metrical dimension within in. The material was per cent semi- stee! casting and each bore had screw hole wall. inter- mittent cutting. The length each tal 144 in. the end this performance, which was the best that was ever accomplished tool the history the insofar accuracy and the cutting edge were concerned, the tool was still capa- continuing without resharpen- Unconventional Boring Bit The tool shown Fig. happens finishine tool and has ground for light cuts. However, for heavy the 26-deg. top back rake just essential and should ac- companied with 5-deg. top side rake for boring cast iron all sizes and for small holes ap- proximately in. steel. bor- larger holes steel could accomplished with less chip trouble 44—THE IRON AGE, November 1940 the top side rake was straight and the 5-deg. angle its equivalent retained the front the cutting the tool. Bear mind, however, the angle shown deg. (top back rake) should always retained under similar dimension conditions shown the illustration. large bor- ing bars boring bits are involved, the top back rake angle will change light high speed finishing cuts are all that will re- quired tool, should not neces- sary provide top side rake angles chip curlers. ° 2—Apart from its set-up boring bar, this desiqn carbide tipped bor- ing tool looks say the least. Yet was highly successful. While the subject carbide bor- ing bits, might well mention here example what can done life can had from the car hide bits. bars. The bar shown the usual piloted boring bar used tur ret lathes. These bars are neces- rather long order reach the pilot bushing located deep the body and sufficient permit simultaneous opera- tion the cross slide durine the bor ing Bars this tvpe have considerable amount