The Iron Age 1941-04-17: Vol 147 Iss 16

APRIL 17, 1941 APR When you tind ina Every screech and growl your overhead crane indication that vital parts are rubbing together. The inevitable result wear, undue maintenance, and expensive repairs. That’s why Whiting cranes have been designed operate smoothly and quietly, even high speeds. Listen Whiting crane. Note its quieter operation. This quietness your guarantee long, trouble-free life. Capacities from one 400 tons. Also electric hoists from tons. Whiting Cor- poration, 15601 Lathrop Ave., Harvey, Canada: Whiting Corp. (Canada), Ltd., Toronto. Builders quality cranes for over years Send for Booklet “How Write Traveling Crane Specification.’’ Free production executives. Watch out for Reduce Noise and Wear Whiting Herringbone Gears These gears save one step gear reduc- tion. They out- last most spur gears Couplings Motor power quietly and smoothly trans- mitted without vibration binding. Two rugged roller bearings keepeach wheel alignment, reducing fric- tion and wear. OVERHEAD TRAVELING Load The herring- bone gears force oil between the brake plates and thus reduce wear. Roller Bearings Gears are kept positive align- ment and fric- tion greatly reduced roller bearings. Tapered-tread drive wheels keep the bridge square and prevent bind- ing and wear. CRANES 4 (ZA APRIL 17, 1941 VOL. 147, NO. VAN DEVENTER President and Editor BAUR Vice-President and General Manager WRIGHT Managing Editor Machine Tool Associate Editor Editor WINTERS Art Editor ROWAN News Editor LIPPERT 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 San Francisco HUGH SHARP JOHN McCUNE Milwaukee Birmingham SANDERSON Ontario ROY EDMONDS St. Louis LEROY ALLISON Newark, Technical Editor Editorial Calling All Technical Articles Flame Hardening with City Heat Treatment with Salt Baths Plastics and Corrosion Resistant Steel Involute Splines Produced with Zero Backlash How Weld Sheet Aluminum Abrasive Blast Cleaner Reduces Burr Removal Costs... Features News and Market Reports News Machine Tool Activity 104 Metal Working Construction Steel 108 District Market Reports ..... 100 Sales Possibilities Copyright, Chilton Company DIX, Manager Reader Service Owned and Published Advertising Staff Emerson Findley Union Bldg., Cleveland Herman, Chilton Bldg., Philadelphia Hottenstein, Otis Bldg., Chicago Leonard, 100 East 42nd St., New York Peirce Lewis, 7310 Woodward Ave., Detroit Ober, 100 East 42nd St., New York Don Harner, 1595 Pacific Avenue, Long Beach, Cal. Member, Audit Bureau Circulations Member, Associated Business Papers Indexed the Industrial Arts Index. Pub- lished every Thursday. Subscription Price: United States and Possessions, Mexico, Cuba, $6.00: Canada, $8.50; Foreign, $12.00 year. Single copy, cents. CHILTON COMPANY (Incorporated) Publication Editorial and Office Executive Offices Chestnut and Sts., 100 East 42nd St. Philadelphia, Pa. New York, 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 ‘ | é ‘ | - id t | | | j i 122-18 WELDING’S QUICK AND EASY WITH THIS HUSKY ALL-PURPOSE WELDER! Plug the welding current you need from clearly marked steps between and 250 amperes—and weld! This FlexArc a-c welder gives you all the ad- vantages a-c welding complete, easy-to-handle unit, ready work—and husky enough for any round-the-shop general use! When the job done, tip back and roll away. Built-in breaker protects against sustained overloads and permits disconnecting the machine. Price includes helmet with lens, welding leads, scratch- brush, electrode holder, primary cable and Ibs. electrodes.* See your nearest Westinghouse Welding Dealer write Westinghouse Electric Manufactur- ing Company, East Pittsburgh, Pa., Dept. 7-N. ALL a | / ONLY 20—THE IRON AGE, April 17, j Calling All Dreamers HIS editorial will deal with dreams. Not the kind that come men while asleep, but the day dreams which the poet John Masefield The dream that fires heart make, build, do, sing say beauty death can never take, Adam from the crumbling clay. fire men’s hearts make, build, our day dreams must set the stage for the introduction ideas. And the ideas must result action. Unless the idea and the action follow the dream, merely air castle. ‘All men action are but all dreamers are not men action. American business and industry have been plentifully supplied with constructive dreamers. That why America today the position feed and finance the rest the world. Fulton dreamed steamboat and made his dream come true. Edison dreamed many dreams, creating the phonograph, the incan- descent lamp, the motion picture and hundred and one familiar and indispensable realities. Andrew Carnegie dreamed empire steel—and built it. Henry Ford dreamed low priced car that could bought thousands people, and made them millions. Inven- tors and industrialists throughout our land have dreamed dreams and lived see the vision these dreams turn into tens thousands new products and into thousands busy factories employing millions ESTABLISHED workers. 1855 time for these practical dreamers ours, our men action, dream some new dreams. New and larger ones. they not, the impractical dreamers will get the jump them, their detriment and the detriment the future America. Hitherto, our practical dreamers industry and business have kept their dreams the confines product, business most, indus- try. Now they must enlarge their dream horizons cover the future relations industry and business America and America the problems post-war reconstruction. The test our American System Enterprise was not the depres- sion; not the armament program, will not even war come that. The test our system and its survival will the time come when the post-war consuming power our people lags far, far behind the mushroomed production capacity our factories. Unless, when that time comes, our practical men vision indus- try and business can step forward with plan, they will find themselves and their country vulnerable the efforts men and women whom our traditional system anathema and who are already making the blueprints for new and strange America. oF 3 5 APRIL 17, | fj Inland Freighters Start the 1941 Season Inland freighters have coaled and headed north the ore docks. The Inland fleet Great Lakes freighters pushing its way through ice the Straits Mackinac, and Whitefish Bay Lake Superior. This the start the 1941 shipping season, when enormous quantities selected raw materials, from Inland’s own sources supply, will brought the Inland mills the southern shore Lake Michigan. After winter careful and thorough preparation, the Inland fleet ready for the strenuous season ahead. Before ice again blocks the passages the Upper Great Lakes, Inland freighters will have brought record ton- nages raw materials the Inland docks. Huge stores ore, coal and limestone will needed for the year ahead, when all production records will broken. With assured adequate supplies raw materials, brought from its own mines and quarries its own freighters, Inland will prepared its full part meeting the national emergency. > om | | | OWDER metallurgy can best defined the art pro- ducing objects powders with without the inclu- sion non-metallic constituents, and with without fusion one more minor components the composition. the practice this art the powder usually pressed sequently simultaneously heated produce coalesced, alloyed welded mass. The advantages the powder-metallurgy technique have been extensively described many technical and non-technical reports the past few years. For this reason would worth while review briefly some the theo- retical aspects which must thor- oughly understood before success may attained with nique. Powder metallurgy had its first real scientific enunciation the work Wollaston. 1828 pre- ° —Some Important Theoretical Aspects ° CLAIRE BALKE Powder Metallurgist, Fansteel Metallur- gical Corp., North Chicago, ° pared pure, solid, ductile platinum from its powder. Nevertheless, ac- cording recent theory concern- ing the method formation gold nuggets, nature was using some the methods used powder metallurgy, and therefore rates the first powder metallurgist. The flecks gold occurring the gold- bearing dikes were washed down- stream, and because their high gravity collected pockets the bed the stream, where they were tumbled, rolled and hammered to- gether form solid nugget. this way nature slowly put one par- ticle metal together with an- other. The scouring effect the sands the stream bed kept the surfaces clean, and fortunate that gold itself very noble metal, otherwise oxidation the surface the particles would have prevented cohesion. This metal also had the further advantage ductility, which allowed the par- ticles readily deformed under pressure into more dense piece. There are four main stages steps the powder metallurgy process: first, the preparation the powder; second, the compaction the powder into piece having some desired shape; third, the heat- ing the compact obtain de- sired solidity and structure; and fourth, the properties the final piece. Some the most interest- ing theoretical aspects the pow- der metallurgy technique concern themselves with the first and third steps, namely the particle metal itself and what goes when compact the particles heated. putting particles metal to- gether obtain solid piece, there are number difficulties which must overcome. These might called “obstructions”; and the first obstruction the most obvious— the actual shape the particle metal. For simplicity, suppose that the particles metal are mathemati- cally perfect cubes parallelepi- peds, and that they could put together, one time, pile much bricks are laid. Once this operation had gone far enough, solid piece metal would ob- tained, yet pressure and heat were employed. Advantage was taken only the atomic bonds which are residual the surface THE IRON AGE, April 17, 1941—23 Cs A a ° a a ° ° ° i { H | | — | the metal. Perhaps the “pile bricks” might have jarred slightly cause sufficient orienta- tion the bonds between particles, but would assumed that the atomic lattices each cube were arranged all the same direction. other words, single crystal solid metal would built up. However, such con- ditions exist. Modern industry has neither the equipment nor the time nor the patience fit little cubes together. The metal particles not have such shape—they have all shapes and all sizes. For this reason the study particle size distribution takes decided im- portance. Ductility Desirable The obstruction shape can overcome some extent making the particles ductile, that when pressed die they will deform readily occupy the empty spaces which would exist loose pile 24—THE IRON AGE, April the powder. der, its preparation mechani- means, work-hardened that Often metal pow- does not deform readily, and therefore must annealed before pressing. Thus, the actual shape the particles metal have de- cided obstructing influence the attainment solid piece. second and very serious ob- struction the condition that ex- ists the surface the particle, namely, surface films usually oxide character which have formed through some chemical reaction the metal with the atmosphere. known that the first visible heat- tint color, pale yellow straw, formed iron relatively low temperature only few hundred degrees C., and that this caused layer iron oxide having thickness approximately Ang- stroms. Such depth roughly ten times the height the unit prism ferric oxide. also appreciated that the atomic cohesive force between atoms barely effective, practi- cally speaking, distance sev- eral atoms. Therefore, when two paratus for the electrolysis produce metallic tanta- lum powder. Shows water cooled iron pot cathode, graphite anode and small auxiliary electrode for starting the electrolysis. particles iron are brought to- gether each having its surface nonmetallic film Angstroms deep, practically cohesive force could obtained all between the metal the two particles unless the blanket oxides were pieced using pressure. Indeed film having thickness only few Angstroms might very effectively prevent metallic cohesion. The ox- ide film the surface metals makes itself apparent when com- noble metals and the baser ones. For instance, gold platinum pow- ders are very readily gether make solid piece. these cases the oxide film tion” almost nonexistent, where- other powders equally ductile must kept air-tight ers, and even the short time in- volved transferring them pressing die, acquire thin film oxide the surface the par- ticles. One the worst actors this respect lead powder. Impurities the surface the metallic particle may other than chemical compounds. surface really dry. Moisture even the common atmospheric gases are con- | } | densed the surface the metal held the film oxide. When metal powder containing this type pressed into tightly knit compact, small pockets voids will left the piece when heated, and will sometimes cause expand. Since the amount these adsorbed gaseous impurities, well the oxide film, function surface, the powder metallurgist faced with new problem, which little concern his contemporary working with the massive metals. For instance, cube cm. edge bounded sq. em. sur- face; this cube divided into smaller ones each having edge only micron, the total surface will reach the enormous value 60,000 sq. cm., 64.5 sq. ft. metal such fine subdivision might not 100 per cent metal; might contain per cent oxide. Fine iron, lead and copper powders must stored very carefully prevent the adsorption impur- ities and subsequent oxidation. Copper powder will often oxidize ARD carbide powders: Ingredients are shown bottom, left right, WC, TaC, Co. The milled powder top having particle size only several microns less pressed into blank and sintered. Shrinkage amounts per cent volume, and this case aided liquid sur- face tension the molten binder. Sintered piece right has practically theoretical density. RIGHT ACUUM sintering furnace: All parts fur- nace must water cooled because the high temperature required for sintering tantalum. The temperature controlled within very nar- row limit optical pyrometers which are fre- quently checked against standard. The final vacuum the order only several microns. few minutes allowed stand the open. This little particle metal might also contain dissolved gases dis- solved impurities some other nature. Most metal powders are prepared gaseous atmosphere, for instance the reduction metal oxides hydrogen carbon mon- oxide producer gas, and they can readily dissolve some the gas, even when the solid condition. This undoubtedly makes the par- ticle harder and less apt deform under pressure—less apt make more extensive contacts with its neighboring particles the pressed compact. For instance, tantalum powder will dissolve much 700 volumes hydrogen under ex- treme conditions, and under nor- mal production operations may con- tain much 150 volumes hydrogen which must removed order make the metal ductile. Another obstruction consists lack ductility either the sur- face compound powder throughout the body single particle. The ductility affected may one the properties the substance itself. For instance, hard tungsten carbide particles will not adhere each other unless they are surrounded thin film more ductile metal such cobalt, which aids extensively pressing the fine powder. Some metal pow- ders are prepared mechanical means, such stamp mills, ball mills, and the particles become bur- nished work-hardened, thus de- creasing their ductility and ability flow into the gaps when the com- pact under pressure the die. Wollaston warned against burnish- ing even the very ductile platinum powder, condition which ham- pered the formation good welds between particles. Tungsten pow- der itself very non-ductile compared with copper powder. Thus lack ductility will then hinder the attainment the eventual solid metal. Another very important obstruc- tion consists mechanically inter- mixed solid impurities, especially where fine powders are involved. This has necessitated the installa- tion expensive air-conditioning equipment number powder- metallurgical plants making hard carbides, where the particle size the order several microns and atmospheric dust must entirely eliminated. Although these are not all the obstructions which the powder metallurgists must face, they pre- sent gloomy picture and make the the process look doubt- ful. They least show the impor- tance the properties the single particle building block for the construction macro pieces. They have been overcome very re- markable degree shown many the commercially successful products the market today. Sintering Phenomena Interesting The third phase powder metal- lurgy, namely, the sintering heat-treating the pressed piece, presents one the most interest- ing phenomena. The most obvious change which takes place during the sintering operation which strikes the eye the fact that the pressed compact often changes its shape and volume considerable amount, sometimes expanding. some cases the shrinkage only matter others, for instance the hard car- bides, the shrinkage will amount much per cent volume. Often the sintering temperature considerably below the melting point any constituent the compact, and yet sufficient shrink- age occurs give practically solid metal. order attempt explain this phenomenon, necessary back the properties the single particle. small particle gold, which chosen ex- ample because not subject oxidation, melted form liquid bead, its surface will appear per- fectly smooth. However, when freezes, the surface wrinkles, due contraction ‘Under the microscope the bead looks like dried-up apple with ridges and creases over the surface. After subjecting the wrinkled bead temperature several hundred degrees below the melting point gold, will not long before the have completely smoothed out, indicating that there powerful force operating along the surface. The hollows are filled and the high points are smoothed off. The time required, even this low temperature, matter only few hours, which quite comparable the sintering time now used many cases commer- cial practice, and, therefore, makes the analogy all the more convinc- ing. Using gold the example again, can shown that small triangu- 26—THE IRON AGE, April 17, 1941 lar gold crystals formed the re- duction gold chloride alde- hydes will become rounded when heated temperature consider- ably below its melting point. Under magnification the crystals appear perfect little triangles, but 900 deg. (1652 deg. F.) for in- stance, the corners gradually round off and eventually the triangles as- sume the shape perfect little spheres. difficult admit that several hundred degrees below the melting point the surface melts without the inside melting. The temperature makes the metal suffi- ciently plastic that the forces operating along the surface can stretch the surface out and smooth down. date little known about the surface tension solids compared with that which known concerning surface tension the liquid state. From these crude examples theoretical picture can drawn explain the shrinkage which goes during the sintering pressed powder compact temperatures below the melting point. When two particles are pressed together that certain points the metal one contact with that the other, the intervening surface films having been ruptured, there will deep crevasse which gradually filled the action the surface tension. other words, the surface tension acts “zipper.” This zipper action pro- ceeds out circular fashion from the point contact, and adjacent circles eventually meet they may catch some solid impurities even gaseous impurities little pocket. Therefore, the first part the sintering operation should taken rather carefully that these impurities may removed before much shrinkage takes place. With this going throughout the whole mass now becomes apparent why shrinkage should expected large scale, and also why there should more shrinkage one case than another. Carrying the idea still farther, can expected that with larger amounts sur- face energy—meaning smaller par- ticles with much more surface—a great deal more shrinkage should take place. Grain growth may ac- company the shrinkage, the smaller grains being absorbed into the larger ones; but seems almost im- possible with this picture mind see how grain growth alone could account for this phenomenon, even that the vapor emanating from metal below its melting point could fill gap pull two particles together. appears though the surface tension solid the prime factor causing shrinkage, and is, therefore, the best aid obtaining solid piece metal. Elevated temperatures simply allow operate rea- sonable time. Tantalum Technique Difficult order illustrate how some these theoretical considerations are applied the practice pow- der metallurgy technique, the prep- aration solid tantalum from its powder may briefly described. the many methods for prepar- ing metallic powders, the one used for the preparation tantalum considered one the most difficult. salt, double fluoride. The electrolysis carried out apparatus con- sisting principally iron pot that acts the cathode, and large carbon anode which can moved and down the elec- trolysis proceeds. The salt freezes next the surface the pot, there very little contamination iron. fine net-work metal- lic tantalum crystals built and the salt gradually solidifies this net-work which carries the current. electrolysis this sort the action which takes place the anode the liberation fluorine which forms bluish gaseous film around the graphite anode, stop- ping the electrolysis. order prevent this oxygen-carrying compound may added the bath, that oxygen liberated the anode, thus gradually burning up, but nevertheless preventing the formation fluorine. When the pot has become full the anode withdrawn, and upon cool- ing the cake shrinks that can easily removed. The electrolysis cake consists solid salt interlaced with fine net-work metallic crystals. must broken up, pulverized and air-separated, fol- lowed extensive washing process free most the salt from the heavy metal. The final tanta- lum powder then contains small percentage remaining salt, 150 volumes hydrogen, 0.05 0.20 per cent carbon, and less than | | | | | | | | 0.02 per cent iron. This the starting point for preparing the solid tantalum. will noted the photo- graph that the powder obstructions described the theo- retical consideration, mainly odd shapes and sizes. The pulverizing and beating action necessary break the salt away from the metal has deformed them, thus work-hardening them some ex- tent. The remaining solid impur- ities well the gaseous ones must removed during the sin- tering process. order remove the carbon, magnesium oxide stoichiometric relation the car- bon mixed with the powder. believed that during the sinter- ing process some the tantalum metal reacts with the magnesium oxide, liberating magnesium the form vapor which removed the vacuum pumps, and forming tantalum oxide within the porous ingot. This oxide soaks through the metallic particles be- ing appreciably soluble the metal itself, and gradually reacts with the solid carbon liberate carbon monoxide. The tantalum powder pressed into ingots weighing between and kg. under pressure the order tons per sq. in. This produces bar sufficiently strong with- stand firm clamping between molyb- denum screws embedded heavy water-cooled copper terminals the vacuum furnace. The ingot heated its own resistance, and because this method heat treatment, the cross section the bar limited. The heat gradient developed between the center and the surface the order sev- eral hundred degrees, that when the current reaches value short that necessary melt the core, the surface the ingot will still several hundred degrees below the melting point. number things happen dur- ing the course the first sintering operation. First, low temper- ature, the hydrogen evolved very rapidly; moisture and gases oc- cluded the surface the metal are driven off; and, little later, the remaining salt impurity melts and gradually vaporized. Care must exercised this first stage the heat treatment that gas not evolved too fast while the salt melting; otherwise, the bar might puff even split. the temperature raised the reaction YDRAULIC press: The segment die has been withdrawn from the press order remove the pressed tantalum bar. Pressures the order tons per sq. in. are required give the bar sufficient strength for handling. for the removal the carbon takes place, and carbon monoxide again drops the vacuum. still higher temperature, dissolved oxygen and dissolved oxide gradually are evapo- rated until the metal becomes quite pure. evident that order for all these reactions take place with the necessity for removal impurities, the bar must porous, and that cannot closed until the impurities are completely out. For this reason the powder must not too fine. Otherwise the porosity would closed the action the surface tension al- ready described the theory. The density the heat-treated bar approximately gm. per cu. whereas the density solid tantalum 16.6 gm. per cu. Thereafter severe hammer- ing operation takes the place the action which fine grains would have closing the pores. This forg- ing must done cold because tan- talum when heated has powerful affinity for all the com- mon gases which render the metal hard and unusable. During the sec- ond heat treatment the porosity almost completely removed the zipper action the surface ten- sion. The cold-working from the forging operation aids recrystal- lization. The density this metal substantially equal that the solid melted material; has the polygonal crystal structure pure metal that has been melted, cast, worked and annealed. From this point the tantalum may worked any the known meth- -ods into sheet, wire tubes. THE IRON AGE, April 17, | / j } 3 28—THE IRON AGE, April 17, 194! BURNERS: Improvements ob- tain higher surface tempera- tures may obtained from two separate viewpoints. multiple port type equipment serving higher pressure mixtures the burner head are advantageous. Apparently the high- port velocities resulting increase both the turbulence the air-gas mixture and the heat transfer rate the surface being heated. The mixture pressure available from proportional mixing blowers inspirators relatively low, be- ing the order in. water column. result improvements may obtained reducing the frictional resistance flame ports minimum. This readily ac- complished using relatively large port sizes for natural gas (No. larger) and using relatively shallow port depths. The alloy grid burner No. was only 1/16 in. thick and operated without flash- back all natural gas inputs from 15,000 40,000 B.t.u. per hr. Close port spacing also ad- vantage obtaining high rate heat release. fact, spacing Combustion, Third Edition, 109. may used which close that the outer flame cones merge. Heat resisting alloy steel re- fractory tunnels are required insure reasonable service life for the burner head. The final design adopted for burner No. shown Fig. The tests this burner higher mixture pressures showed that limit had been reached the amount natural gas which could burned with this head. The results calculated indicate that when port velocity about ft. per sec. was reached the flames lifted from the ports and tended burn outside the tunnel. port velocities could probably tained when using manufactured gas due its higher flame velocity. The turbulence caused the tunnel explains part the high port ve- locities obtained. interesting compare the velocity obtained with that for atmospheric type burner operating approximately the same primary air-gas ratio. The velocities which flames lift from the ports atmospheric type burn- ers are given 2.5 3.5 feet per USE OXYGEN: Where the area 4—Final design adopted for burner No. Grid and tunnel made oxidation resisting alloy. Tunnel nipple Gas Mixing Check arrestor Mixing valve Standard oxygen for gas burners. for example hardening piston pin bearing, more concentrated heat release can obtained using gas, air and oxygen mixtures, extreme case, gas and oxygen mixtures. fact these higher temperature flames could ap- plied wherever limited hibited the installation multiple air-gas burners. Another typical example hardening confined spaces would include the heat treat- ment gear teeth. Indications the present time are that surface temperatures which are sufficiently high for these using oxygen, air-gas mixtures rather resulting considerable savings cylinder oxygen consumption. Proportional mixing blowers and inspirators have been used for the purpose pre-mixing gas and oxygen with some sults. one case the flashback which occurred cracked the casting blower mixer. damage was done steel and iron inspirators, but the explosions obtained upon flashback were very intense. result, work with oxygen, and gas mixtures was continued using small size mixing tee just back Compressed Gas air supply Gas Oxygen cylinder riame ly | | fleck valve | | the burner head for the purpose introducing oxygen. flash- back difficulties were experienced with this arrangement. However, light weight swing check valves were used prevent either the air oxgyen from traveling back into the gas line. Higher mixture pres- sures used also backs for some These swing check valves effective- protected the meters from dam- age when back-firing was obtained during the runs with proportional mixers using pressure oxygen from When working with air, gas, and oxygen, the air-gas mixture was first adjusted obtain soft, blue, large volume flame the burner head. Then the oxygen valve was opened gradually until sharp flames, having distinct inner cones which burned the flame ports were ob- tained. After obtaining flame which would remain the ports was often possible increase the gas and air input after which second adjustment the oxygen input was made. The success obtaining smooth operation with gas, air, and oxygen attributed the high mixture pressures developed back the burner head. well remem- ber that high mixture pressures with consequent high port veloci- ties would operate prevent flash- back. The general arrangement the mixing equipment used shown Fig. was also found that single compressor could used supply mixture gas and air placing throttling valve and suc- tion tee the inlet line the compressor. The negative pressure developed the inlet inspirated air from the atmosphere mixing with gas the compressor. The mixing method thus similar that used the Selas pre-mixing system, except that the Selas units avail- able have higher capacities and serve air-gas mixtures pressures burner tips. Safety devices used included both KRAPPE School Chemical and Metallurgical Engineering, Purdue University, Lafayette, Ind. —Continuation data presented last week. Herein, attention directed toward improve- ments air-gas burners, use oxygen, and test results with gas and cylinder oxygen mixtures. the swing check valve and flame ar- restors placed the mixture line and the air inlet. The size the compressor should selected the basis the total gas and air requirements, allowing cu. ft. air for each cubic foot natural gas burned. pressures lb. per sq. in. ap- peared adequate for most the burners tested including the al- lowance for pressure drop mix- ing tees and pipe lines. TEST RESULTS—AIR, GAS, AND OXYGEN MIXTURES: The maximum temperatures attained refrac- tory brick ranged from 2120 deg. 3180 deg. depending principal- the gas input the burner and amount cylinder oxygen in- jected into the air-gas mixture. These are the equilibrium tempera- tures obtained allowing enough time for the surface the refrac- tory heated its maximum temperature. For any given gas input the amount oxygen which would result short, sharp flames was limited narrow range. general, the gas input given burner was increased, larger pro- portions oxygen were required obtain concentrated heat release. Burner No. 11, blow-pipe de- signed for air-gas mixtures, was damaged when operated with per cent cylinder oxygen the air- oxygen mixture. tem- perature 3180 deg. was reached, but after min. opera- tion, the brass head began melt. Heat-resisting alloy heads are re- quired when operating tempera- tures above 2600 deg. Burners not equipped with flame retention devices will give satisfac- tory flames when cylinder oxygen introduced into the air-gas mix- ture. typical example that Burner No. ribbon type burner. which could not produce sharp flame with natural gas and air alone but which performed very satisfactorily when using per cent cylinder oxygen the mix- ture. The surface temperature pos- sibilities for Burner No. were not exhausted. alloy steel construc- tion were used place bronze, the gas and cylinder oxygen input could increased without damag- ing the head. Burners equipped with flame re- tention ports around the main flame port produced heated areas with hot spot the center. The sur- face temperatures reported are those the central hot spot. Typi- cal examples are burner No. and burner No. 16. Burner No. 17, similar construction, produced relatively large heated area but there was evidence cold streaks spotty heating. For all the burners tested ex- cept No. the cylinder oxygen was introduced into mixing tee di- rectly back the burner head. Burner No. was special design which the jet oxygen was in- troduced directly into the air-gas flame using No. orifice and oxygen pressure Com- pared the other burners tested, the flame was extremely noisy and the surface temperatures developed comparatively low. Table sum- marizes the test results obtained using air, gas and oxygen mix- tures. The wide range surface tem- peratures obtainable may visu- THE IRON AGE, April 17, 1941—29 J —= s 4 } alized from Fig. which also sum- marizes the results for air-gas and gas-oxygen burners. TEST RESULTS—GAS AND CYLIN- DER OXYGEN MIXTURES: Surface temperatures excess the melt- ing points iron and steel were obtained using burners and torches designed for oxygen and gas. All the burners tested were fur- nished with burner heads capable resisting oxidation and excessive scaling high temperatures. How- ever, was necessary avoid placing these alloy steel heads too close the refractory surface. one test run, the hot gases were reversed direction when firing into-a depression the refractory resulting slight fusion the alloy tip. interesting note that these temperatures were obtainable when using relatively low gas and oxygen pressures. The maximum gas pressure available from the small gas compressor was lb. per in. previous research work welding with city gas -and oxygen pressures high were required, probably due the fact that the conventional welding torch was signed for use with compressed gas cylinders. probable that Research Series No. 41, Engineering Experiment Station, Purdue University. the diameter internal pas- sages and the small diameter tub- ing used accounted for considerable pressure loss. this experimental work there was little pressure drop the piping, most the pressure energy being used the mixing tees. shown Table the me- tered usage cylinder oxygen was less than the theoretical require- ments for natural gas. The stoich- iometric theoretical requirement roughly cu. ft. pure oxygen per cu. ft. gas burned com- pared with actual ratios 1.5 apparent that the addi- tional requirements for combus- tion the natural gas were sup- plied diffusion air from the atmosphere into the flame. The flames appeared oxidizing steel; consequently scaling factor actual practice selec- tive heating, excess gas may used with some sacrifice the sur- face temperature obtained. Burner No. 13, hand torch de- signed for low pressure city gas and oxygen produced surface tem- peratures excess 3000 deg. without the use gas compres- sor. Uniformly heated areas from in. 1.5 in. diameter were easily obtained depending the gas input used. Burner No. 14, fish-tail tip, de- veloped maximum surface tem- TABLE Ill Representative Test Results Using Air, Gas, and Cylinder Oxygen Per Cent Cylinder Oxygen Surface Area Burner Gas Input, Pressures, per sq. in. Temperature, Heated, No. Mixture Air—Gas 0.** Deg. In. Oval Circle* Oval Circle* 32,600 1.4 2650 diam. Circle 42,000 2.3 2450 diam. 40,400 2.6 2475 diam. *Small diameter refers inner hot spot, large diameter total area heated visible color daylight. Burners with number flame retaining ports around the central port produced this effect. **Pressure outlet cylinder regulator. Oxygen pressure further reduced burner head means valve oxygen line. 30—THE IRON AGE, April 17, 1941 perature 3250 deg. rating 40,000 B.t.u. per hr. The uni- formly heated area was oval sec- tion having dimensions in. in. This flame melted groove chrome brick. The melting point this brick given 3700 deg. F., but apparently the high ve- locity the hot gases against the refractory surface resulted fu- sion taking place 3250 Burner No. 15, circular tip having central port 1/16 in. diameter, with flame retention ring surrounding this port pro- duced maximum atures between 2500 deg. and 3000 deg. The tip operated vis- ible light red heat. The area heated consisted central white hot spot around which area in. diameter was heated visible red. Many the burners equipped duced this type heated area. depression was produced the surface fireclay refractory whose melting point given 3200 deg. Descriptions burners and mix- ing equipment for heating tests are listed below: (A) Natural Gas-Air Burners: (1) Sticktite Maxon Premix Eclipse Fuel Engineering Co. (2) Sticktite %-in., firing into 2-in. alloy steel tunnel in. long insulated with high tempera- ture insulation. (3) McKee blast head No. 70, Eclipse Fuel Engineer- ing Co. (4) McKee counter-sunk Lava tip No. 3N, 1%-in. I.P.S. Eclipse Fuel American Lava Corp. (5) McKee Ferro-Fix I.P.S. (6) “No Blow” blast tip No. 3K, %-in. I.P.S. (8) Special Gas Engineering Lab- oratory design with punched circular ports. Consists reducing coupling in. in. and in. close nipple which serves combustion tunnel. The punched grid in. diam- eter, port size 0.079 in. staggered, Harrington King designation, holes per sq. in. The grid made pure nickel sheet 1/16 in. thickness. (B) Burners Used for Mixtures Natural Gas, Air and Oxy- gen: (7) Ribbon Tip No. IRT, Eclipse Fuel Engineer- ing Co. (9) Elbow gas burner, nozzle mix- ing type North Ameri- Manufacturing Co. Air-natural gas mixture supplied burner from inspirator using gas pressure 5-in. water column. Oxygen mixed nozzle through No. orifice wit tor ete n with oxygen pressure from per sq. in. (11) Stand blow pipe No. INS. American Gas Furnace Co. (12) Stand blow pipe No. ONS. American Gas Furnace Co. (16) Machlet Tip No. 63, %-in. American Gas Furnace Co. (17) Machlet Tip No. 422, LP.S. American Gas Furnace Co. (C) Burners Designed for Gas- Oxygen Mixtures: (13) Oxygen-gas blowpipe (hand torch) No. 583E. American Gas Fur- nace Co. Central port 3/32-in. diam- eter with flame retention ring. (14) Oxygen-gas fishtail burner, No. 1081A. American Gas Furnace Co., Nine ports No. drill, with smaller ports surrounding these ports. (15) Oxygen-gas tip with circular port and flame retaining ring. No. 814D, American Gas Furnace Co., I.P.S. Central port 1/16-in. diameter. (D) Mixing Equipment and (1) Mixer Catalog No. Rating 100 cu. ft. natural gas per hr.; maximum mix- ture pressure 2-in. water column. Mason Premix Co., Muncie, Ind. (2) Gas air compressor, capacity 200 cu. ft. per hr. measured deg F., in. Hg. Maximum outlet pressure, lb. per sq. in. Ensign- Reynolds Co., New York. (3) Mixing tees. Ordinary galva- nized iron pipe tees, and pipe sizes. (4) Oxygen cylinder regulator with pressure gages. Alexander Mil- burn Co., Baltimore. (5) Back pressure valve. Light swing check valves, Con- nelly Iron Sponge Governor Co., Chicago. (6) Flame Arrestor, American Gas Furnace Co. (7) Precision flow control valve, numbered, I.P.S. Mehler Preci- sion Valve Co., Pittsburgh. (8) Flow control I.P.S. Jenkins Valve Co. Summary review the fundamentals the hardening operation indicates that the rapid water quench pro- duces the hard, martensitic surface structure desired flame harden- ing operations low carbon steels. Required surface temperatures be- fcre quenching depend the type being hardened which may anywhere the region from 1500 deg. 2400 deg. This phase the investigation burners for selective heating covers the operation and applica- tion natural gas-air burners TABLE Test Results Using Cylinder Oxygen—Natural Gas Mixtures Surface Area Pressures Temperature, Diameter In. Ratio Burner Gas Input, Cylinder No. B.t.u. Per Hr. Oxygen Gas 8,400 1.5 1.0 (hand torch) 16,000 1.2 1.0 11,500 1.3 1.0 14,000 1.1 1.0 5,940 2.0 1.0 (fishtail 11,800 1.5 1.0 37,800 1.4 1.0 41,500 1.2 1.0 4,030 0.9 1.0 (circular tip) 5,950 1.7 1.0 in. Ib. 2830 oval 3.3 2980 overall *Pressure outlet oxygen cylinder regulator. This pressure was throttled further means valve the mixing tee directly back the burner head. and compares surface temperatures reached air-gas burners and burners using supplementary oxygen. (1) Surface temperatures 2100 deg. have been reached using gas and air mixtures. Sur- face temperatures increase rapidly the gas input given burner increased, being limited the gas (and air) input which flames lift from the flame port. suggested that multiple air-gas burners may used for flame hardening obtain higher produc- tion speeds. (2) Surface temperatures 2700 deg. have been reached mixing per cent oxygen the air-oxygen volume used for combustion. 3,250 3,000 2,750 IG. surface temperatures ob- tainable with burners for selec- tive heating using natural gas. Burner num- ber indicated op- posite point. Maximum surface temperature, optical pyrometer, deg.F (3) Surface temperatures 3250 deg. have been reached when using cylinder oxygen and gas. This temperature excess the melting point iron and steel and was obtained using gas pressures only per sq. in. (4) The use mixing equip- ment serving high mixture pres- sures the burner head has fa- cilitated the production higher surface temperatures and improved burner operating characteristics. Ed. Note:—Next week another article will presented the use gas for surface hardening. will concerned with the design burner tip for flame hardening cam shafts. All these data were presented the Mid West Indus- trial Gas Sales Council the Industrial and Commercial Gas Section, American Gas Association. Air Cylinder only cent cylinder oxygen air-oxygen mixture oxygen only THE IRON AGE, April 17, 1756 ° ° 1,500 salt bath has distinct use the heat treating room every manufacturer. These may divided into two distinct types, the baths used for hardening and those used for tempering. Hardening Baths The baths used for hardening and annealing have three distinct ranges. The normal hardening tem- peratures, the high-chromium high- carbon steel range, and the high speed steel range. These harden- ing baths have distinct advantages over lead baths, because the salts not adhere the steel does lead, which results difficult clean- ing operations; they require charcoal cover when operated steel hardening tempera- tures, and they not have the toxic fumes lead ated temperatures 1600 deg. higher. However, they are not rapid heating the lead baths are. The baths used for normal tem- peratures are three general types. The first mixture al- kali carbonates and chlorides and may used from 1200 deg. 1650 deg. The second mix- ture alkali chlorides and may used from 1400 deg. 1650 deg. Both these baths are usually used with addition about per cent borax, otherwise they become contaminated oxide which will cause some decar- treated. bath composed barium, so- dium and potassium chloride may used from 1200 deg. 1800 deg. graphite cover main- tained when used the higher temperatures. Many attempts have been made the past years produce satisfactory bath for the treatment high speed steel. The original bath barium chloride was ceived with open arms until was found that this bath operated 2350 deg. F., was extremely cor- rosive the pots, and tac bei th: sil an ay | Ww tl 4 3 tacked the thin edges the tools being treated it. The result was that generally fell into disuse. the past few years suitable silicate bath has been developed for the treatment high speed steel, both the standard tungsten steels and the molybdenum high speed steels. The composition the high speed steel hardening bath not available for publication, but the mechanics the operation are follows: The high speed hardening done unit three distinct baths. The first one preheat bath which operated 1500 deg. From this bath the work trans- ferred the high heat bath until the predetermined time reached, after which transferred the quenching bath which tained between 1200 and 1300 deg. The purpose this bath not only cool the tools this temperature but help remove the high temperature salt which carried over the tools facilitate the subsequent washing operations. The tools may then cooled air quenched. The Cyanide Reheat The per cent sodium cyanide bath extensively used for reheat- ing carburized work and for hard- ening the high and medium carbon steels, those the oil hardening types. This bath has the advantage over the other types hardening baths that decar- burization whatever will take place during the heating cycle. This extremely important grinding take place work- ing after the hardening process. This bath advantage treating the newer air harden- ing steels that are hardened from the range 1500 deg. 1575 deg. These steels may heated the bath without preheating, when LLOYD RAYMOND Fairfield, Conn. —Continuation data presented the issues April and April 10. Herein, attention directed salt baths for hardening and tem- pering, operation salt baths, and types equipment general use. section less than in. thick- ness, and air cooled after heating. The cyanide prevents decarburiz- ing during heating and cooling, there coating the bath the steel throughout the air cooling process. course, oc- change and the advantages this type steel are fully realized. treating the oil hardening die steels the cyanide bath for hard- ening, the same coating the tool slows the rate cooling slightly that not necessary heat the oil when intricate sections are used, and the result hard sur- face, scaling, and minimum loss due cracking. The cyanide reheat the usual gear steels slight increase surface hardness over the con- ventional methods gear harden- ing, and has been claimed that gears which have been heated the cyanide bath are less subject tooth pitting under severe service than gears hardened direct from the pack muffle furnaces. There are two disadvantages the cyanide reheat for hardening bath. Certain machine parts are carburized and then have section the case removed machining before hardening that machining operations may performed dur- ing assembly, and then hardened. These types machine parts may not hardened from the cyanide reheat they will pick sufficient hardness where not desired ren- der them unfit for the machining operation during assembly. Very thin springs cannot sat- isfactorily hardened from the cyan- ide bath due nitrogen pickup during heating, which renders them quite brittle. The nitrogen will not react the subsequent spring tem- pering operation readily the carbon, and unsatisfactory spring results. This layer nitride thin, however, that not all objectionable quite heavy springs. Tempering Baths The tempering baths may di- vided into two classes, those for low temperature tempering and those for high speed steel temper- ing. The low type are composed either alkali nitrates, mixture These baths have melting points from 285 deg. 585 deg. F., and may used from deg. above their liquefaction points about 1100 deg. any nitrite composed entirely nitrates. These baths, particularly the bath composed potassium nitrate and sodium nitrite, are well adapted for use heat coloring steel. using polished articles, excellent colors may obtained with little effort. The cyanides are widely used for tempering hardened high speed steels. The usual practice harden and temper the high speed tool and then, after grinding, THE AGE, April 17, 1941—33 De 4 { heat the tool cyanide bath for period time. This second treat- ment actually nitrides the surface the steel, giving greater hardness. Extensive studies this process were reported the 1939 National Metals Congress Messrs. Morrison and and Messrs. Cohen and The usual salt bath used for treating the high speed steels per cent NaCN and per cent KCN, although some prefer use mixture sodium cyanide and fluidity used the tempera- tures usually employed, about 1050 deg. These baths may also used for nitriding alloy which are capable being nitrided. Operation Salt Baths These salt baths may used conventional hardening and tem- pering baths and the majority them are employed. However, since the interest has become keen the method interrupted quenching usually called austem- pering, new and important field for the use the salt bath has been opened. The steels, when austempered, are generally heated hardening temperature lead bath and then quenched into hot salt bath from 450 deg. 850 deg. F., depending upon the service de- manded from the material being treated. salt bath used for heating the high temperature, care must exercised that the dragout from the high temperature bath does not increase the melting temperature the lower tempera- ture bath due contamination. The cyanide must alwa