The Iron Age 1940-12-05: Vol 146 Iss 23

DECEMBER 1940 VOL. 146 NO. VAN DEVENTER President and Editor BAUR Vice-President and General Manager Managing Editor News Editor Technical Edito: Machine Tool Associate Editor Editor Art Editor Editor Emeritus Washington Editors MOFFETT JAMES ELLIS Resident District Editors CAMPBELL HERMAN KLEIN Pittsburgh Chicago Cleveland Detroit Editorial Correspondents Buffalo Cincinnati FRAZAR CHARLES POST Boston Son HUGH SHARP JOHN McCUNE Milwaukee Birmingham Toronto, Ontario St. Louis LEROY ALLISON Newark, Editorial Big Business and Little Plants Technical Articles Radiographs the Modern Manner Aluminum Alloy Extrusion Industrial Controlled Atmospheres What's New Machine Tools Colored Stainless Steel Feature Reports the Assembly Line Washington News News and Market Reports News Industry Machine Tool Activity Personals Non-Ferrous Market 100 Scrap Market and Prices November Pig Iron Output 101 Construction Steel Comparison Prices 102 Iron and Steel Prices Summary the Week 103 Pig Iron Prices The Industrial Pace 104 Warehouse Prices District Market Reports 106 Sales Possibilities Fatigue Cracks Products Advertised Index Advertisers Copyright, 1940, Chilton Company DIX, Manager Reader Service Owned and Published CHILTON COMPANY Advertising Staff Publication Editorial and Office Executive Offices Chestnut and East 42nd Philadelphia, Pa. New York, U.S.A. U.S.A. Herman, Chilton Bldg., Philade!phia Hottenstein, Otis Bldg., Chicago Leonard, East 42nd St., New York Peirce Lewis, 7310 Woodward Ave., Detroit Ober, 100 East 42nd New York Don Harner, Pacific Avenue, Long Beach, Cal. OFFICERS AND DIRECTORS MUSSELMAN, President JOS. HILDRETH, Vice-President GEORGE GRIFFITHS, Vice-President VAN DEVENTER, Vice-President BAUR, Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JULIAN CHASE, THOMAS KANE, 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. ‘ 123 124 126 148 ‘al 32—THE IRON AGE, December 1940 | DEC. 1940 ESTABLISHED 1855 Big Business and Little Plants Defense Program big business. Where little companies fit into big business? This question that perplexing the many thou- sands small concerns throughout the United States today. These peo- ple want their bit for Uncle Sam. Also, they want their proper share defense production that they can survive and have chance grow into larger concerns after things get back normal. want these small plants survive and grow larger. And want new small companies come into the picture with the same fre- quency and opportunity success that they have had the past. That the way American industry grew. started with acorns, not oaks. There are about 166,000 individual manufacturing concerns the United States. the matter defense contracts, our Government has dealt with not more than 1000 them. This not criticism; helped. The way get things started fast possible was place many big orders soon possible. And that meant with the larger companies. would physical impossibility for our Gov- ernment deal directly with thousands small concerns. Negotiations and follow through would necessitate impossible expansion the Government organization. The theory and the hope that through subcontracts, placed the original large concern contractors, plenty work will trickle down and fill the available small plant capacity. some localities, Detroit for example, where the big fellows are well acquainted with their smaller neighbors, will probably work out without much difficulty. But there will nine cases ten where work out unless something done about it. Unless keep activity balance between our big plants and little plants, the latter are going seriously lose their relative position our scheme things. will come through with our big plants stronger and larger, and our small plants smaller and weaker. That will not good for the America tomorrow. Government realizes this situation and has taken steps aid the smaller concerns through the Federal Reserve system. But not enough. The smaller plants that want defense work should organize communities, preferably through their chambers commerce and after it. There will enough work around; the question is: “Who best fitted make 77 = | 2 | | | | | | | | | 4G | | 1 | | | Sound Raw Material Program Leads INLAND QUALITY One the most important means used Inland produce steel highest quality program which assures continuous flow uniform raw materials. This Inland practice illustrated the great care taken selecting, mixing and blending basic iron ore. assure uniformity and continuity supply, Inland owns large ore reserves known quality. These are mined methods which avoid inclusion impurities. Every car ore, used Inland, sampled leaves the mine. When these cars are dumped into pockets the upper lake docks, the highest and lowest different elements are evened out with infinite pains blending. Further mixing occurs when the ore flows into the steamer. The ore mixed third time during the process un- loading and piling the mill. Again, when loading the skips that feed the Inland blast furnaces, the grabs that dig through the ore accomplish final mixing. Equally important are Inland’s large stocks specialty ores that allow adjustments down manganese, phosphorus, silicon and other elements meet turers’ special requirements for particular products. this program, uniformity the watchword Inland organization. with the mining raw materials distant points and follows through every step the Inland process making quality steel. SHEETS STRIP TIN PLATE BARS PLATES FLOOR PLATES STRUCTURALS PILING RAILS TRACK ACCESSORIES REINFORCING BARS APID has been the develop- ment industrial X-ray ap- plications the past decade, tremendous impetus has been given this field the rigid testing specifi- cations recently laid down United States Government for ex- amination aircraft and other mate- rials for national defense. Indeed, seems quite probable that the next months will see the scope X-ray testing extended disclose many properties metals now discernible only more tedious and destructive methods. While this growth has not resulted —Describing lead foil technique which permits decrease exposure time and any important advance the X-ray so—it has fathered several improve- ments technique and the appur- tenances used increase radiographic quality. One the foremost these improvements has been the use metal foils for the elimination ray secondaries and back scatter and for intensification X-ray image. order grasp clearly the impli- cations this recent advance, con- sider briefly some properties the time-honored calcium tungstate inten- sifving early 1895, Roentgen himself observed that some chemicals were excited visible fluorescence under with crystals certain salts, part the energy X-ray beam under- goes transformation the direction longer wave lengths and appears visible light. This phenomenon has which also brings out clear cut detail ROBERT WOODS Physicist, Bell Aircraft Corp., Buffalo, been put use intensify the effect X-rays the emulsions photographic films. finely divided layer fluorescent calcium tungstate crystals deposited cardboard-like backing and then covered with film transparent cellulose material protective coat- ing. application, the screen placed with its chemically covered side di- rect contact with the bare film emul- sion and both are enclosed light- tight envelope holder. Under ray exposure, the calcium tungstate screen emits visible light. wherever rays have bombarded its and this light, being emitted close con- tact with the film, naturally produces corresponding image the photo- graphic emulsion. Now since X-rays themselves also produce photographic images the fluorescent screen image clearly nothing more than reinforcement the first. Actually, THE IRON AGE, December 1940—35 » e | | | | | tungstate crystal fluorescence film emulsion grains. tungstate crystals, translucent pro- tective film covering photographic emulsion grains the X-ray film. IG. 2—Two radiographs butt weld. (A—Above) Taken with calcium tungstate screens. (B—Below) Taken with the lead foil method described herein. 36—THE IRON AGE, December 1940 however, the photochemical effect the visible light far the stronger, the intensification factor high 200 some instances. Quite evidently, then, when object combination, its image will faith- fully reproduced except that great deal less radiation intensity will re- quired produce equal amount objects, which would quire long exposure for inspection, may penetrated fraction that time recourse calcium tungstate intensification. practice, two such screens are commonly used, the film being sandwiched between them. ‘The rigid, metal, light-tight which screens are mounted are known cassettes. first glance, device and method such described may seem almost ideal condition affairs, but tunately there are drawbacks, which times can fairly serious. one thing, the crystals calcium tung- state the screen are much larger than the silver bromide grains the photographic This means that every time single tungstate crystal fluoresces, affects large number emulsion grains, illustrated the exaggerated view Fig. Fig layer calcium tungstate crys- tals, translucent protective film covering and the coating photographic emulsion grains the X-ray film. result this con- dition, distinct line demarcation between exposed and unexposed areas appears the film, one density more less fading into the other. Unfortunately, this bigness grain cannot modified too much. When the grains are small, the speed their fluorescent reaction slow and there The larger the grain size, the faster their response X-rays which also brings with the disadvantage just discussed. result, research fluorescent screens constant struggle raise the speed reaction and yet keep the diffuseness image tioned that such efforts are being re- warded continual advances the quality and usefulness both intensi- fying and fluoroscopic screens. Secondly, sort powder train phenomenon undoubtedly occurs under the stimulus X-rays. That is, short wave fluorescent rays and_ ejected photoelectrons from one particle ex- rescence. Referring Fig. again. A || j \ | / | \ ; | | \ \ \ \ \ \ \ \ | \ \ \ \ \ / \ \ / \ \ / \ \ \ \ / | | suppose the actual limit X-ray beam extends from crystal from tends excite which turn has lesser effect and on. Crystals adjacent also behave similarly. Then too, although protective coat- ing thin, does allow minute amount light reflection take place within itself. While one these phenomena too grave matter, all three taken together produce diffuseness detail and outline which detract from the diagnostic quality the Perhaps the greatest disadvantage the calcium tungstate screen, how- ever, the fact that intensifies not only the direct, primary radiation com- ponents which make true record conditions within the object being ex- amined, but also softer, less penetrating rays scattered from and emitted the object. This latter type ray adds nothing the picture except general fog, thus tending obscure outline and detail. Where possible surround the object completely with opaque X-rays, the problem scat- tered radiation not quite serious. ideal shielding condition occurs the butt weld. this instance, the weld itself the object under exami- nation and surrounded metal fused right it. Figs. and are two radiographs butt weld. taken with calcium tungstate screens and with the lead foil method about to be discussed. lt will noticed that the blowholes the weld show both films. the radiography irregularly shaped objects, shielding generally tedious and often impossible. Two the main problems, therefore, are decrease ex- cessive exposure times jects and yet bring out clear cut detail. From the foregoing discussion, may IG. 3—When lead screens are used place cal- cium tungstate ones, the ef- fect roughly that shown here. appear these two fac- tors are hardly com- patible, but the ad- vent lead foil in- tensifying screens has made possible compromise. Use screens based two factors; partial filtration scattered and secondary radia- tion, graphic image inten- sification electron emission. Two sheets 0.005-in. lead foil fastened rigid backings can mounted cassettes “a A—Radiograph made using lead screens and the exposure regulated give the predetermined photographic blackening, density, most suitable for examination. IG. Fig. 4A, but secondary and scattered rays are not filtered out. ail 46. 3 q q 4 = : | \ | \ ° ° \ | and handled the same calcium tung state screens. When lead screens are used place calcium tungstate ones, the effect cassette loaded with X-ray film, between two lead foil screens and After passing through the flanges casting the X-ray beam composed primary radiation plus large quantity longer wave length scattered rays, and soft secondaries emitted the object itself. The scatter and secondaries, how- ever, being generally less penetrating than the original beam absorbed lead screen 1L. This process eliminates much what might called helter-skelter radiation which overlays the true image with secon- dary blanket fog. The filtration role played the rear screen, 2L, also illustrated the same figure. Some which pass completely through the casting and cassette, then strike sur- rounding objects and back toward the film. this back scat- ter not absorbed device such screen 2L, will produce further fogging the image. well known that electron im- pact will expose the grains photo- graphic emulsions, exactly pho- tons light X-rays, and this phe- nomenon here utilized obtain some measure X-ray intensification. The mechanics the phenomenon are fairly similar those the calcium tungstate screen, except that photoelec- trons discharged from the lead surface next the film are substituted for fluorescent light rays. But each elec- 38—THE IRON AGE, December 1940 IG. 5—Cassette loaded with lead foil screen be- tween the object and film, and another lead screen back the calcium tungstate. tungstate tron very small compared cium tungstate crystal and does not expose large numbers emulsion grains. Neither are emitted electrons open the powder train reflection disadvantages. The outstanding draw- back that two lead screens produce only intensification two one over screen practice, compared one hundred more for calcium tungstate. so, the increased radiographic quality obtainable with lead screens general offsets the other necessary in- creases voltages and exposure time. the steel casting radio graphs Fig. clearly illustrates the value lead screen practice. Fig. was made using lead screens and the exposure was regulated give the predetermined photographic black- ening, density, most suitable for purposes X-ray examination. The relative density photographic images ment called microdensitometer, which gives comparative readings based known and density curve. will noticed Fig. that the general detail good with clearcut edges. The lead figures show dis- tinctly, indicating that most the radiation recorded the film com- posed primary X-rays which have penetrated the object direct line. previously discussed, this desirable type radiation. Fig. good illustration what happens when secondary and scattered rays are not filtered out, but are re- corded and their along with primary radiations the casting appear quite fuzzy and the lead letter far from distinct, Fig. 4A. However, the actual photographic density tical areas the two radiographs exactly the same. Moreover, there are absolutely clear areas Fig. where the density the casting was such absorb all the X-rays before reach- ing the film. these same areas are not clear, but look though the metal those points penetrated, and under stances these areas might pass hav- ing been X-rayed. Actually, this means that part the exposure Fig. due some type radiation other than direct primary and result somewhat fogged. Conversely, the dis tinctness the first film means that detrimental secondaries rays have been mostly removed. While all this forms argument for the use lead screens, still leaves unsolved the problem overlong exposures. Most fortunately, fairly satisfactory compromise may effected the combination lead and tungstate screens. the first place, only one calcium tung- state screen used, instead two, there considerable decrease the bad effects due intensifying crystal size, powder train fluorescence, and multiple reflections between screen and film. This conclusion follows logically from the fact that the causes contribut- ing these phenomena have been cut heen done eliminate the evil in- tensified secondaries, scatter scatter, but this can taken care placement lead foil screen be- tween the object and film, with another lead screen back the calcium tungstate. cassette loaded for this technique arranged indicated Such method filters out secondary and scattered rays just efficiently lead screens alone, but has the ad- vantage retaining per cent the intensification value calcium tung- state screens. Thus object which would normally require posure for X-ray examination with two tungstate screens, would need 2-min. exposure using the combined lead and tungstate screen technique. all cases where exposure times are rea- sonable anyway, the doubling this value will certainly not prevent serious obstacles, because rule this factor only small percentage the time consumed industrial X-ray work. and shows the marked improvement radiographic quality 4 | / ° ° ° | | | / ° ° ° | 4 | j | | | lead foil and calcium tungstate used rather than the tungstate alone. conclusion, word explana tion might appropriate relative remark made early this discus- sion; namely, that important vance the X-ray machine itself need expected result recent indus trial radiographic growth. truly radical change the method production has been invention hot highly evacu ated tubes 1917. This does not imply, course, that further advance possible, but view what now known just seems And even some revolutionary new way pro would not necessarily mean any great advance industrially, simply because the would still the same old type radiation with cians are accustomed deal from day day. more practical would some startling innovation methods handling the beam system X-ray filtration, satisfac tory method for enlargement images during exposure, improvement which would X-ray more valuable present applications and extend cover tirely new fields. that most industrial workers are devoting their energies specifications should not enough those manufacturers who have sin cere desire witness the advance industry. For after all, knowledge what might termed various states material defectiveness important factor the advance preparation for the defense it. improvement quality through use lead foil. (A—left) Calcium tungstate screens alone; note poor detail and fog. right) Cal- cium tungstate and lead screens; improved detail fog. THE IRON AGE, December 1940—39 } | | My | | | x a 2 4 4 q q 4 q q i q q q = ar q 4 4 | 4 ; q ¥ | | | i | | | | i] | : } . Aluminum Alloy Extrusion ERNEST PANNELL IRECT Turning from the presses the process itself, should first noted that the metal dealt with always solid semi-plastic form and the laws fluid pressure applying such process die casting not hold. the plunger moves forward the hot metal billet tends move before and the part immediately opposite the die sheared off and extruded. the same time metal feeds radially the center just front the ing pressure pad and this action con- tinues the end the stroke. The operation completed when all but in. the billet has been extruded, the residue forming the “slug” which left the container. the case aluminum alloys important factor the skin oxide which surrounds the billet. The fric- tion this skin the container wall very high and the correct clear- ance used the following pad the latter will shear the metal just inside the skin leaving the latter the bore. If, the other hand, the pad approximates fit the con- 40—THE IRON AGE, December 1940 tainer, the skin will tend buckle and turn over the rear end; will then extrude with the last portion the rod and may render the latter un- sound. (See Fig. 5.) The effect produce thin tube oxide sur- rounding core solid metal, which latter may even pushed right out the rod. Some valuable studies this defect have been made the leading British authority, Genders, who has explained the effect the lines just indicated. the other hand, the late Dr. Rosenhain held the view that any unsoundness was due im- perfect casting and piping the billet itself, and recommended that the latter charged with the head next the die and also that the follower pad should corrugated hinder the radial flow the oxide the center. The general opinion favor the theory Genders, and the following precautions are now taken secure the maximum soundness and homo- geneity the extruded rod: (a) reasonable degree reduction 8:1 more (Fig. 4); (b) use clean technique, equipment. and metallurgy extru- sion becoming increasingly important, what with the cur- heavy demands for air- craft shapes light alloys, and some makers steels this country considering this method production. The author has been observing aluminum alloy extrusion England for many years, and herein describes direct, in- verted, and tube extrusion; compound dies, composite metal extrusion. Last week, attention was directed ex- equipment and die materials used. billets carefuily poured and fed; ample clearance the pressure pad; and (d) where possible the use multiple die decentralize the prod- uct. suitable practice followed, will found that unsoundness confined the front and rear end the extruded rod where cropped and discarded. Generally the soundest product that with the thin- nest sections even though the shape complicated one. Some British authorities favor some method lubricating the billet reduce its friction the container wall, but has not yet been found that any lubricant will stand the heat and pressure employed. Apart from this difficulty would have the effect permitting the oxide skin travel more freely and turned the follower and extruded. already seen, this probable source unsoundness and the better prac- tice allow the skin cling the bore. The temperature extrusion varies according the metal being pressed. Pure aluminum becomes very plastic | | : ' | } | mt i { | | | | under pressure and can worked over wide range temperature; usually pressed from 850 deg. 920 deg. might expected, the extrusion pressure falls off rapidly with temperature. The same true the heat treated alloys, but view the narrow critical range temperature this does not allow much latitude. Metals the Duralu- min and Hiduminium class are pressed 720 deg. 780 deg. using from 50,000 60,000 Ib. per sq. in. pressure. the hardness the alloys extrusion extremely slow, but any attempt accelerate would result dangerous pressures being reached. complete Duralumin billet may re- quire min. for complete extrusion this being, course, less the reduc- tion small. INVERTED According the authority, Genders, already quoted, the process wasteful energy and yields imperfect prod- per cent the power applied used forcing the along the length tion. the die, mounted hollow plunger, pressed into the billet the plastic metal motion only the die opening; there is, moreover, disturbance the oxide skin, and the central core the rod invariably (Fig. 6). Following the lower ating pressure, the strain the container, die and all working parts correspondingly reduced. Another merit the inverted proc ess the more thorough utilization the billet since the only discard the thin shell around the bore the con- authorities openly assert this method superior the direct process, tendency minor surface defects being its only drawback. must noted, however, that the mounting the die hollow plunger introduces problems its own. Not only rigid mounting difficult obtain but the size rod extruded strictly limited owing the wall thickness the plunger. ments water cooled dies are progress which show promise ac- celerated production, but such cooling will obviously possible only with stationary die. The indications are, therefore, that while the direct process will continue predominate com- mercial production there distinct field for the inverted method, and the advantage will lie with presses which are designed operate both meth- ods. press where the container has full horizontal motion (as Fig. shown last week) the die mounted 4—Structural sections produced Schloe- mann press with container. (Left) beam ft. long; reduction (Right) angle ft. long; reduction 5—Influence follower pad extrusion. Above) loose fitti fitting pad buckles and extrudes oxide. extru pad shears off oxide skin. Container sion using fixed die and moving container. THE IRON AGE, December 4 t 4 | q ig AD | k | | the end hollow stem attached rigidly the front platen. The con- tainer attached the crosshead and moves unison with the main ram, being forced over the die for the work- ing stroke. simpler and more rigid stroke and short billets are used. ducing tubes involve the use some kind core mandrel form the bore, and the early days tube extrusion stem was attached rigidly the front the follower pad and extending through the hollow billet and die. stem in. diameter working circular die 3-in. diameter would duce tube in. in. thick. Bil- lets were cast with through the center which the stem was loose fit. Obviously while such methods would produce tube blanks for re-drawing, these were far from true concentric and only heavy walled stock could extruded. greater disadvantage was the tendency the stem break off where attached the pad account the unbalanced pressure, and while the process was satisfactory for use with higher temperature, hardness aluminum limits its use with this metal. The most usual method emploved present involves the use separate plunger and mandrel operating through the center the main plunger and traveling through the cen- ter the container right the die opening. The billet may cast which case the mandrel through the center and ejects plug waste metal. this stage the main plunger travels forward and_ forces the finished tube through the die. when all the working parts the ma- chine are correct alignment and compensated for wear ture changes. With horizontal press heavy tubes much in. diameter are regularly produced but small diameters and light gages are more accurately formed vertical machine. European practice, however, generally favors the use powerful horizontal press conjunction with series drawbenches. Tubes with wall thickness down in. are formed the press and subsequently drawn finished size the bench. authority with consider- able experience extrusion, Wragg, quotes the following degrees tolerance tubes produced com- in. outside diameter, eccentric- 42—THE IRON AGE, December 1940 tricity 0.015 in., and in. eccentricity 0.02 in. the overall usual for tubes in. diameter and in. for larger diameters. This expert points out that closer toler- ances can obtained the expense more supervision rejections. The above figures give some indication the minimum practical wall thick- ness which can leading English authority, Robson, gives 0,040 in. the minimum wall thickness commercially practicable using vertical tube press. For lighter gages drawbench operation will not only give the necessary reduction but will harden and straighten the support. Several processes have been patented closed sections without the use mandrel, and these methods are ap- limited range box sections. (See while core plug cannot sup- ported simple die can intro- duced the die two parts. possible for the opening the which the core steel supported tongue metal the side. This core extended beyond the face the die through counterpart having round opening thus forming capital proper temperature and pressure conditions the metal welds to- gether passing the tongue and emerges perfect tube. For many years the principle has been applied the extrusion lead covered cables but the case aluminum alloys has been extended and developed produce wide range complicated sections involving script patterns and openings for inserts the finished sec- tion. some designs the die opening begins four circular holes equally spaced around the central axis. These IG. Tube ex- trusion use mandrel. (Above) mandrel advancing and forming bore tube. (Below) plunger advancing forming finished tube over mandrel. open out and join around central core having sharply defined front edge form the bore the tube. The outer wall the tube formed simi- larly defined flange the outer die which registers with that the core. This method production, while in- tended mainly for tubes relatively large size and gage, claimed give great accuracy. is, course, free from any irregularity due slight mis- alignment the press components, and press without special cylinder and ram for tube pressing. The foregoing processes indicate the extent which better die steels and more ingenious die design too! making are contributing the press itself. view the first cost, cost operation and maintenance alignment mandrel type tube press, any method which can ap- plied machine the simple type has great advantage economically. METAL EXTRUSION: Some interesting studies made define the flow the metal from the billet out through the die with view establishing what part the block was the first ex- truded and what part followed. Much this experimental work was done wax, plasticine and soft metals and the results were not truly representative. Later English investigator, Pearson, studied the flow aluminum alloys splitting the billet, painting the flat inner surfaces hoard pattern and afterwards assem- bling and extruding. The elongation the black and white portions the finished rod showed graphically ex- actly how the cast billet developed when pressed. Others have experi- mented with billets two more dif- ferent metals with view obtaining The process rolling drawing / | | | / A SA A A A AAA AAAS, ° ° ° | Container Die | | | | | | | ‘ | | composite metal has been known and practiced for many years. For exam- ple, the production copper-clad steel wire involves the rolling and drawing composite billet which the cen- tral core steel and the outer copper. The final product has uniform coating copper from end end without irregularity. the case extrusion, however, the billet not elongated uniformly the same way, and concentric billet were used the container the result would for practically all the core metal ex- truded first. Alternately, experiments have heen tried with two Container side Section necessary crop off and scrap the first and last portion extruded. While this process successful for rod and tube production not adapted more complicated sections, especially those having angular con- tours. such case, while the coat- ing metal will lie thick the flat portions will quite absent the sharp edges. limita- tion that the two composite metals should have nearly the same working range temperature form homo- geneous product. ALLoys: light metals come three classes: (a) alu- —— Outlet side Compound dies for tube extrusion. ele- mentary form. (Below) patented design. different metal charged into the con- tainer this case the fin- ished rod would show first one then the other and lastly the first metal pre- dominating the composite rod, wire tube, the ingot special way that the central core metal forms perfect cone surrounded the outer coating metal. (See 9.) ingenious method patented and coming into extensive practical often desirable for light alloy tube lined cov- ered with layer high purity alumi- num few thousandths thick act corrosion resisting skin. such case the ingot would poured with the alloy forming the cen- tral cone and the pure metal the sur- rounding material fill the mold. The proportions the two metals will de- termine the thickness the layers that either thin lining thin cov- ering can produced the tube. minum per cent (b) normal and heat treated alloys. The first mentioned important com- mercially the shape architectural and auto body moldings, tubes and wide range sections which not call for mechanical strength. The ten- sile strength averages 11,000 Ib. per sq. and the elongation per cent; this high degree ductility makes possible form shape the sections after extrusion. For example. extruded flat busbars for switchboards can edgewise; tubes can coiled around short radius and mold- ings can shaped conform the curves motor coach hodies. the engineering sense, however, pure alu- minum extrusions are unimportant. Normal alloys aluminum-copper, aluminum-zine are extruded commercially, giving product some three stronger than pure pressures are called for and closer con trol working temperature means container with thermo- static regulation. alloy per cent zinc and per cent copper was extruded experimentally the late Dr. Rosenhain, using pressure 34,000 47,000 Ib. per sq. in. and temperature 700 deg. The re- sulting rods gave tensile strength 66,000 Ib. per sq. in. and elongation per cent. view these re- markable properties without heat treat- ment this alloy was expected rival duralumin, but was not adopted com- mercially because its high density and low corrosion resistance. al- loy per cent zine and per cent copper however being extruded for use screw machine rod and gives 40,000 Ib. per sq. in. tensile strength with per cent elongation. The British standard, known 32, the same class but contains per cent zine. series normal alloys has been investigated Pearson, the British authority. These were mainly the aluminum-copper group contain- ing per cent copper. 660 deg. and pressure 29,000 33,000 Ib. per sq. in., the finished rods gave tensile strength 26,000 29,000 Ib. per sq. in. with and per cent elongation respectively, depending the percentage copper. The tests were made principally establish re- lation between operating temperature and pressure; the hotter the billet the lower the working pressure the con- tainer. limits temperature are, however, not wide enough the case alloys take full advantage this law. Pearson’s made small inverted type press and cannot compared with the con- ditions direct extrusion. Heat-treated alloys the Duralu- (CONCLUDED PAGE 92) Plunger 9—Composite billets for ex- truding coated rod and tube. THE IRON AGE, December 1940—43 | | ne | “ AA \ AAA Af } A | © WA | @) 4 4 | 4 j ae } 4 AAA PPO LS AA | } | if, WE. | | | ~ | Cable Applications ANY thousands feet cable enter into the assembly Douglas transport and tary planes, large proportion being the preformed type which does not fray out when cut and which can run over pulleys sheaves smaller diameter than the type which not preformed. great deal the cable used made from stainless steel wire because the safety factor in- herent its resistance corrosion. the casual observer, cables and the methods which they ened other parts may appear like minor but they are far from being taken for granted aircraft manufacture. the Douglas plant Santa Monica, Cal., entire de- partment given over the prepara- tion lengths cable and the appli- Several different methods attaching fittings are employed and all cables used flight control are subjected test under loads much beyond those they must carry service, make sure that the cable itself well the fittings attached will not fail service. All cables for flight control must have fittings attached swaging splicing and without the applica- tion heat. Swaging done standard swaging machine, with the sleeve portion the clevis other fitting held suitable die, the cable, course, being inside the sleeve. The series blows applied the hammer- like action swaging cause the metal the fitting flow into the spaces the individual wires the cable, making the fitting, effect, vir- tually one piece with the cable. solder other foreign substance applied this operation and heat- ing needed. average case, the fitting can slipped over the cable, adjusted position the swaging machine and the swaging done the rate about one fitting minute. The machine has hollow spindle through which the cable ex- tends and through which cable, with the fitting attached, can withdrawn after the swaging com- pleted. The fastening secure that the cable itself will break under pull much less than that which would required separate the cable from the fitting. Splicing over thimbles done jig which holds the parts correct relative position, and follows well standardized procedure. done hand, but with the use pliers and other hand tools and involves inter- lacing the separated cable strands with those forming part the cable itself where the strands are not sep- arated except provide openings through which the strand ends are threaded. Again, solder plied the case flight control cables but, after the wire ends are cut off the splice often covered with tape wound with cord afford smooth surface. Some cables not used for flight control soldered, the solder being applied from ladle and touched with electric soldering iron make sure FEW the numerous sizes and lengths flexible cable and some the fittings applied them, methods outlined the text, the Doug- las Aircraft plant, Santa Monica, Cal. required. many cases where fittings are applied sweating, the cable supplied with the steel wires tinned. After the cable has been cut length, the clevis other fitting slipped over the cable end and, the sleeve open the outer end, the ends cable wire are slightly spread turned over. Then the cable end and fitting are dipped molten solder once twice make sure that the solder runs where required, after which the assembly wet set the solder. This operation, though simply described, requires considerable skill insure good joint and done, course, workmen who have acquired the neces sary skill through long experience. Stops are sometimes required cables points between the ends and these also are applied soldering. The clip stop ready tinned and, when correct position, soldering applied the use electric iron. Before cables have fittings attached they are usually cut required lengths benches provided for this purpose, many the lengths being ft. more and others shorter, down few inches long. some cases, necessary thread the cables through sheave holes before the fittings are attached. All cable assemblies are given, course, rigid visual inspection and those involved flight control are proof tested. done attach- ing the fitting one end the short vertical arm bell-crank, the long horizontal arm which carries weight required size. other end the cable then attached small hydraulic jack arranged track which can clamped when adjusted. When ready receive the load, the jack used apply the quired pull, which that necessary raise the weight the horizontal arm the bell crank. Naturally, the pull, which may two three that the cable will subjected ser- vice, applied the end fittings well the cable. The test affords assurance that the joints between the cable and the fittings have been prop erly made. The accompanying illustration shows several the shorter lengths cable and the various types fittings plied each the methods above. Naturally, many much longer lengths cable than are shown and various other shapes and sizes tings are included among those handled for different purposes | | | | | | | 4 EREIN, the third sec- tion four-part ar- ticle, the author describes nitrogen generators and nitrogen atmospheres, and double cracked gas for heat treating high carbon and tool steels decarburization- free, bright scale-free. previous issues attention was directed efficiency con- trolled atmospheres, the air- gas ratio method, pack hard- ening, atmospheres produced carbonaceous mufflle blocks, cracking liquid hydro- carbons, etc. recent developments con- trolled atmosphere methods pro- posed for heat treating high carbon and tool steels bright scale- free and free from decarburization carburization are follows: (1) Chemical purification tors. genera- (2) Nitrogen generators. (3) Endothermic reaction genera- (4) Charcoal gas charcoal gas mixed with other gases. (5) Specially designed furnace for using cracked anhydrous ammonia. Chemical Purification order produce atmosphere which could used heat treat high carbon and alloy steels scale-free and decarburization-free, industrial furnace and atmosphere manufacturers decided eliminate the remaining un- chemical purification and drying. some The flow sheet for this process can seen Fig. 17. This method and equipment for removing the COs and the consist closed and auto- matic system scrubbing towers which the laden gas bubbled passed through spray the chemical absorbent, which usually one the ethanolamines related chemical that series. this process all the H:S and practically all but light trace COs effectively removed. The free gas then passes through surface cooler where the excess water vapor condensed and separated out. The partially dried gas finally passed through activated alumina drying equipment and dried down dew point —50 deg. —60 deg. C., practically bone dry. The Industria rolled Atmospheres NORBERT KOEBEL processed gas now ready enter the furnace chamber. The laden absorber from the scrubbing tower passes automatically into another tower having electri- cally gas heated chamber for dis- tilling off the and any The COs, and steam from this dis- tillation process passes through re- flux condenser which the and are separated from the water. This water returned the system after the hot and somewhat concen- trated and ethanolamine solution passed through heat ex- changer and cooler. The ethanolamine then passed back through the scrub- bing tower complete the cycle. Thus, this method the chemical absorbent kept the proper concentration and used over and over with only slight addition the chemical from time time for make-up losses. The activated alumina dryer regen- erated from time time heating the chamber with either electric gas and blowing air through the activated alumina drive off the moisture steam. some cases the air heated the heat from the combustion cham- ber, thus supplying hot air regen- erate the dryer and also controlling the temperature the combustion chamber the same time. While this THE IRON AGE, December | t 3 | | | | | | | J regeneration process being carried out second activated alumina cham- ber used for drying the gas from the removing equipment make the process continuous. The resulting gas from the above equipment will contain CO, and possibly trace (0.05 0.10 per cent) The amount and depend upon the air-gas ratio the combustion equipment. re- ferring back Fig. 10, apparent that great variety gas composi- tions containing CO, and can obtained. However, from both laboratory experiments practical experience from industrial furnaces best control the combustion composition possible and also end with about 1.0 2.0 per cent The small amount CH, needed balance out the de- carburizing properties the and also keep the atmosphere balance small traces air filter into the fur- nace react with the form and with the form Also, from Fig. apparent that the resulting gas will always higher than CO; thus raise the right amount that the re- sulting processed gas neither car burizing decarburizing, the range air-gas ratios becomes quite limited. also desirable keep the CO: overtax the removing equipment and thus obtain better efficiency and sulting purified gas. The above equip purified and dried atmosphere the following composition: per balance Fig. shows the results obtained testing high carbon steel samples chemically purified atmosphere. The tests obtain the curve 1750 deg. F., 250 deg. higher than necessary for the steel treated, were pur- posely made determine the stability the atmosphere, whether the various gases the atmosphere react with each other various furnace temperatures produce undesirable atmosphere, and also able pre- dict the tendency the atmosphere towards decarburization rization. The results obtained both sets samples are not only excellent, but are also perfect. The advantages chem- ical purification can readily seen from these results noting that the 46—THE IRON AGE, December 1940 elevated temperature curve practically coincides with the lower temperature curve showing the ten- dency remain neutral and showing indirectly its stability. This atmosphere can quite reasonably cost about 75c. per thousand cubic feet depend- ing upon the cost the raw gas and the design and efficiency the unit. The only serious disadvantage this atmosphere the initial cost the equipment produce it. The smallest unit that can about 200-400 cu. ft. per hour and costs from $3,000 $5,000 depending the design and manufacturer. One can imagine the difficulty industrial furnace manufacturer would have selling continuous produc- tion furnace tool room furnace employing atmosphere equipment cost- ing much twice much the furnace itself. Because this disad- vantage only few installations are now use, and these are very spe- cial applications. Within the last year strides have been made the development low cost equipment produce atmospheres low for high carbon and tool and alloy steels, and thus the method chemical puri- fication scrubbing out the COs has practically been abandoned has chosen for very special application where the optimum atmos- phere conditions are Nitrogen Atmospheres One the first lessons taught chemistry that certain and gases like nitrogen, neon, argon, helium, are inert and not react with other substances. With this idea mind coupled with the re- sults obtained from laboratory almost all who have had anything with heat treating conceived the idea that nitrogen would the ideal heat treating atmosphere. Because the high cost reclaiming nitrogen from air and selling bottled con- tainers, this gas has had very little use application commercial heat treating and has been confined chiefly the laboratory experiments. With the above views mind, sev- eral manufacturers have developed and perfected very ingenious method producing nitrogen low cost with purity from 99.0 99.85 per cent. principle this method identical with the one already described under the heading purification,” and the same explanation and flow sheet, Fig. 17, will therefore apply this method. The only difference operation that the air-gas ratio the combustion unit set that prac- tically perfect combustion obtained (see Fig. 10) and the only products resulting are and H:O. The mine, and the excess moisture con- densed out and the gas finally dried the use activated alumina dryers leaving practically pure The sulting gas usually analyzes from 99.0 99.85 per cent 0.05 0.030 COs, 0.10 0.90 CO, 0.00 0.05 de- pending upon the setting the air- gas ratio and the efficiency the CO. removing equipment. Usually tempt made keep the air-gas ratio set produce fractional per cent order prevent any fractional percentage case the gas conditions should happen fluctu- ate abnormally. desired, however. the above equipment can operated other composition with amounts and CO. The chief difference equipment and the other explained under the heading “chemical purifi- cation” the design the combus- tion unit obtain precision results perfect combustion and the design the COs remover handle the in- creased volume effectively and efficiently. This has plished very effectively, and all credit must the engineering skill that has been put into the design this equipment. shows the results obtained the high carbon steel strip samples heat treated commercial furnace the muffle type employing atmos phere from commercial nitrogen generator. these results can seen that this type atmosphere far from being neutral and too decarburizing for thin springs 0.005 in. in. stock such were al- lowed had remain the fur- nace for period over The elevated temperature test this stee! shows that the decarburizing proper- ties this atmosphere are magnified, and even worse decarburization might expected from this atmosphere high carbon tool and alloy steels. The above samples heat treated atmos phere were quenched directly into oil, through chute, without contact- ing the air. These samples were scale- colored. explanation the decarburizing properties atmosphere “A” Fig. 19, the section the theory good atmosphere and the effects impuri- ties, the previous section this - | | | | | | | | i | i] i | | i} } | | | — | article should referred to. this section the effects COs impurity atmosphere were discussed and illustrated curves. should also noted that the ratio atmos- curves, Fig. 15, will noted that 1500 deg. such ratio decar- not. The results this test can also seen Fig. 19, referring the curve atmosphere This atmos- phere was even more decarburizing than the one with less CO. The sam- ples were also stained colored. CO, Although the ratio greatly decreased atmosphere another decarburizing combination Surface Reactivating these curves have very little use predicting the results protective atmosphere since most atmospheres are complex mixtures various gases. above results obtained from nitrogen atmosphere, set tool steel samples were heat treated the same com- mercial, muffle-type furnace using atmosphere with high purity that could obtained within the valve Flowmeter other important point which often overlooked when considering atmos CO, phere; the ratio what really counts and not the percentage the atmosphere. The high percen- tage nitrogen would tend slow such reaction down dilution, but the equilibria would not changed. From the above consideration and analysis atmosphere the decar- burizing tendency such atmos- phere might predicted, but the mag- nitude its effects would have never great without the aid actual test data. attempt was made eliminate the undesirable decarburization and temper marks adjusting the air-gas ratio the generator unit put