The Iron Age 1942-06-04: Vol 149 Iss 23

JUN 5 1949 IRON AGE IN TWO SECTIONS—SECTION ONE STANDARD BEARINGS as vital as STANDARD AMMUNITION Ball bearings made to standard dimensions ond tolerances can b yet -valel i; which require extra to ent machine set-ups One ‘special may well delay delivery of many stondard bearinas. and the machines awaiting them —in adatt servicing in the field. Cc a New Deport hy WON LS: BALL BEARINGS # FOR VICTORY “Our Specifications called for worm gear drives—our called for C@velands” Look at Clevelands’ record in a particu- larly vital war metal industry—an industry noted for the heavy shock loads it is for- ever piling on its equipment. You'll have even greater confidence in Clevelands after seeing them at work in this industry’s great Mills — and hearing the comment of one Mechanical Engineer who has used them for many years: — “Worm gear speed reducers simplify the transmission of power to our machines, and our good experience has led to the purchase of many of your Units.” In fact, this large Corporation ordered a single Cleveland in 1926 and since then has bought more than 50 of them. Cleveland Engineers will help you plan drives for your equipment that will in- sure the low-cost, trouble-free operation enjoyed by the other Cleveland owners in every major industry. The Cleveland Worm & Gear Company, 3252 East 80th Street, Cleveland, Ohio. Affiliate: The Farval Corporation, Cleveland, Manufacturers of Centralized Systems of Lubrication. In Canada: PEACOCK BROTHERS LIMITED CLEVELAND THE IRON AGE, published every Thursday by the CHILTON CO. (INC.). Philadelphia under act of March 3, 1879. $8 yearly in North America and South America, Foreign $15. Vol. 149, No. 23. Entered as second class matter November 8, 1932, at the Post Office at ce at JUNE 4, 1942 VOL. 149, No. 23 © J. H. VAN DEVENTER President and Editor Cc. S. BAUR Vice-President and General Manager ° ° ° Managing Editor, T. W. LIPPERT News & Markets Editor, J. A. ROWAN Technical Editor, F. J. OLIVER Associate Editors D. R. JAMES G. F. SULLIVAN T. E. LLOYD Art Editor, F. J. WINTERS Editorial Assistants M. M. SCHIEN G. B. WILLIAMS J. 1. BUTZNER S. H. BARMASEL R. E. BENEDETTO Washington Editor L. W. MOFFETT Resident District Editors T. C. CAMPBELL W.A. PHAIR Pittsburgh Chicago B. W. CORRADO W. F. SHERMAN Cleveland Detroit CHARLES POST San Francisco Editorial Correspondents W. P. DEARING ROBERT G. McINTOSH Buffalo Cincinnati G. FRAZAR R. RAYMOND KAY Boston Los Angeles HUGH SHARP JOHN C. McCUNE Milwaukee F. SANDERSON Toronto, Ontario C. H. BACON Seattle Birmingham ROY M. EDMONDS St. Louis ° ° ° A. H. DIX, Manager Reader Service ° ° ° Advertising Staff Seen eee’ Lia Union Bldg., Cleveland B. L. Herman, Chilton Bldg., Philadelphia H. K. Hottenstein, 1012 Otis Bldg., Chicago R. Raymond Kay, 2420 Cheremoya Ave., Los Angeles, Cal. H. E. Leonard, 100 East 42nd St., New York Peirce Lewis, 7310 Woodward Ave., Detroit C oes 100 East 42nd St., New York W. B. Robinson j W. J. Fitzgerald } 428 Park Bldg., Pittsburgh D. C. Warren, P. O. Box 81, Hartford, Conn. O. L. Johnson, Market Research Mar. B. H. Hayes, Production Manager. R. E. Baur, Typography and Layout. ° ° ° Member, Audit Bureau of Circulation Member, Associated Business Papers Indexed in the Industrial Arts Index. Pub- lished every Thursday. Subscription Price North America, South America and U. S. Possessions, $8; Foreign, $15 a year. Single copy, 35 cents. Cable Address “lronage N. Y." ° ° ° Owned and Published by CHILTON COMPANY (Incorporated) Executive Editorial and Offices Advertising Offices Chestnut and 5éth Sts. 100 Eost 42nd St. Philadelphia, Pa. New York, N. Y. U.S.A. U.S.A. OFFICERS AND DIRECTORS C. A. MUSSELMAN, President JOS. S. HILDRETH, Vice-President GEORGE H. GRIFFITHS, Vice-President EVERIT B. TERHUNE, Vice-President J. H. VAN DEVENTER, Vice-President Cc. S. BAUR, Vice-President WILLIAM A. BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JULIAN CHASE, THOMAS L. KANE, G. C. BUZBY, P. M. FAHRENDORF, HARRY V. DUFFY CHARLES J. HEALE This Week in... ——— THE IRON AGE Editorial The Management Bottleneck . Technical Articles Stretch Forming Contoured Sheet Metal Aircraft Parts Recovering Light Scrap ............... | Casting 500-Lb. Aerial Bombs Reducing Aviation Crankshaft Rejects Silver Brazing Alloys and Procedures Acid Open Hearth Composite Casting by Consecutive Pouring of Two Melts Desulphurization with Acid Iron Slags New Equipment Speeds War Drive ... New Equipment: Finishing Apparatus Novel Metal Stretching Press . Features Assembly Line Washington West Coast .. Fatigue Cracks Dear Editor | News and Markets This Industrial Week | News of Industry _... Personals and Obituaries Machine Tool Activity | Non-Ferrous Metals Scrap Markets Iron and Steel Scrap Prices Comparison of Prices Finished Steel Prices Warehouse Prices Products Advertised Index to Advertisers Copyright, 1942, by Chilton Company (ine.) ee qi ae 47 49 78 82 86 90 92 94 97 143 146 147 148 150 151 152 154 194 241 “There IS Something you can do to get STEEL more quickly! Steel deliveries are a problem! Stocks are depleted, mill deliveries delayed, priorities strictly enforced, demands heavier as war production intensifies! But there is something you can do about it—several things, in fact! Work closely with Ryerson on your requirements, and follow the common sense rules of action. 1 Make sure of your priority status. essary. This will preclude the possibility of further correspondence that might de- (a) If you are engaged in direct war pro- lay shipment, or prior sale of material. duction and require immediate stock ship- ments from time to time, be sure to properly 3 When possible, send orders — not in- extend to us applicable priority ratings. This should be done by extending any blanket rating in the manner required by the blanket under which you are operating or by properly endorsing purchase orders, as in the case of priority ratings based on certificates. (b) If you are not directly engaged in war production work, check up on the proper rating for your repair and maintenance requirements, because effective after May 4, anew order,amendment No. 4, supplemen- tary to General Preference Order M-21-b, establishes closer control and greater limitations on the distribution of steel. Because of the importance of following Government regulations to the letter, make sure that your orders are formally en- dorsed, using the proper forms when nec- quiries. This is entirely safe because of the long-established Ryerson one-price policy. It is possible the steel, if in stock, might be sold while we are answering your inquiry. 4 Whenever practicable, state what alternate sizes, shapes, or types of steel you can use if the desired steel is not in stock. 5 It is also helpful to indicate the size or length to which the steel will be cut so that we may fit your requirements to avail- able sizes and lengths when regular sizes and lengths are not in stock. We are most anxious to help you with every problem of steel procurement or application, during these critical days! Do not hesitate to keep closely in touch with us. JOSEPH T. RYERSON & SON, INC. CHICAGO - MILWAUKEE : DETROIT - ST. LOUIS - BUFFALO - BOSTON - CINCINNATI - CLEVELAND - JERSEY CITY - PHILADELPHIA 46—THE IRON AGE, June 4, 1942 THE | The Management Bottleneck E have heard a great deal about all sorts of bottlenecks. That is quite natural in a forced draft economy whose prime objec- tives must be to meet successfully and satisfy constantly increasing demands which are so large as to defy imagination. First we heard about the machine tool bottleneck. But that neck has been knocked off the bottle by an eightfold expansion of the machine tool building industry. Then came the variegated material bottlenecks. Nickel, copper, aluminum, steel and so on down the line. And these, in turn, are being taken care of by a “conservation” program which emphasizes salvage and restricts the use of the available supply to essential purposes. Just now we are facing the transportation bottleneck. This, too, will be broken before long, thanks to the effective work of Admiral Land and Coordinator Eastman. Among other bottlenecks that have been mentioned is that of labor personnel and electric power. But I haven't seen or heard much com- ment about the impending bottleneck in management. ate A bottleneck in management would be a real bottleneck indeed. You can increase productive capacity, develop natural resources, build JUNE 4, 1942 power plants, train women in industry and turn out new ships and railroad cars much more readily than you can create managers capable of directing these enterprises. We can make new factories out of wood, machine bases and heavy parts of concrete, ships plates and tank cars out of glass, if need be and do it almost overnight, relatively speaking, but it takes 10 years’ time and a good man to start with to make a high grade industrial or business manager. ° ° ESTABLISHED 1855 When raw material becomes short, we apply conservation in one form or other and particularly do we seek to avoid unnecessary waste. Why not apply this principle to the most precious and vital war material that we have, namely managerial time? Today far too much managerial time is taken up in making reports instead of turning out products vital to our war program. Too much of it is taken up in defending industry before investigating committees instead of offending the Japs and Germans on the battlefields. The watchword today, in our armed forces and industry and business. as well should be “offense”, not “defense.” Today there are more sheets of paper being shipped to Washington from American industry than there are guns and planes being sent to Australia or Russia. A good job of simplification done by a competent efficiency specialist in Washington could conserve managerial time and forestall a management bottleneck. (Pelee: “Swing Over” Production is Made Easier with the Help of Inland Metallurgists In these critical days one manufacturer after another must learn, often from scratch, how to make radically new products, how to operate new equipment, how to adapt old machines to new uses, and how to control new processes. They are in the throes of a “swing over” from peacetime manufacturing to wartime production. Inland metallargists are familiar figures in many of these plants, where for years they have been applying their expert knowledge of putting steel to work for others. Today, Inland metallurgists are continuing that valuable work. Their technical and practical ex- perience in the selection of steel, in latest fabri- cation methods, and in speeding up output are helping manufacturers produce for victory. If you have a problem in the use of steel, call for an Inland metallurgist. SHEETS + STRIP - TIN PLATE - BARS - PLATES - FLOOR PLATE - STRUCTURALS - PILING - RAILS - TRACK ACCESSSORIES - REINFORCING BARS Bas: 38 S. Dearborn Street, Chicago * Sales Offices: Milwaukee, Detroit, St. Paul, St. Louis, Kansas City, Cincinnati, New York Stretch-Forming Contoured— Sheet Metal HE development of a method for forming airplane skins and other relatively shallow contoured parts by the process of stretching, to cause them to attain and keep the desired shape has been the subject of considerable research at Lockheed Aircraft Corp. The general principles in- volved in this method were de- scribed in a paper recently pre- sented before the Institute of the Aeronautical Sciences’ in January, 1942, but it is here intended to give a more detailed description of the various stages passed through in this development, together with the essential points of the technique as it now exists. In the aircraft industry it has long been customary to form skins, cowling panels, and other parts having double-curvature contours of large radius, by methods which may be classified as hand-forming. Crown rolls, speed hammers, ete., have been used, each part being an individual enterprise requiring con- siderable labor. Even with drop hammers, a great deal of hand work and intermediate annealing has been necessary, and when contours are very shallow, springback diffi- culties have been excessive. Of necessity, annealed material has Aircraft Parts . . . Detailed description of the technique, results and limitations of recently developed methods for forming double-curvature airplane skins and other shallow con- toured parts by stretching are presented herein. This is another step in the adaptation of high speed forming operations to aircraft production. ° ° By T. H. HAZLETT and M. M. ROCKWELL Research Engineers, Lockheed Aircraft Corp., Burbank, Cal. ° been used in all cases, with the sub- sequent expense and trouble of heat treating and straightening. More recently, however, atten- tion has been focused on the de- sirability of finding a way to form large contoured parts in the heat treated condition. Fuselage and wing skins have been viewed as a particularly important problem, since heat treating such large parts is difficult. The general principle to be ap- plied seemed to be that of stretch- ing the material into the plastic range while forming it to contour over a punch, thus eliminating ex- cessive “springback.” This prin- ciple, often applied in the automo- tive industry, had been applied in the aircraft industry to a limited ° extent by the use of simple stretch presses.” *- 4 45 However, in order to assure rapid and _ successful operation on a large scale, the fol- lowing questions needed to be answered: (1) If the contour is very shal- low, must a_ positive outwarg stretching force be applied, or can enough stretch be obtained from merely restraining the edges of the material while the punch descends? (2) If the part is contoured in both directions, must it be stretched in both directions, or at least restrained in one direction while being stretched in the other? (3) How can the material be gripped without tearing? (4) How can wrinkles be avoided ? THE IRON AGE, June 4, 1942—49 To investigate the basic principle involved in stretch forming, the Production Research group at Lockheed constructed, in the sum- mer of 1940, a small skin-stretch- ing machine having clamps ar- ranged to stretch the skin in a single direction. A positive outward force-could be applied to the clamps through the action of a cam mech- anism attached to the descending ram of the press to which the wooden punch was attached. By the use of this simple skin stretcher the desirability of apply- ing the basic principle of forming a shallow contoured part by stretch- ing was clearly established. Direct verification was obtained for this assumption, based on the successful use of the stretching machine else- where. Stretching need be in only one direction even for a skin con- toured in both directions. However, serious difficulties were encountered in clamping the sheet without caus- ing it to wrinkle or tear at the clamps during forming. Later studies have shown that this is the essential difficulty with this type of equipment. In the absence of an extremely powerful external force to actuate the clamps, they must be given a serrated or other irregular shape to provide sufficient frictional re- straint to hold the sheet; and these irregularities tear the sheet when it attempts to yield locally within the clamps in the process of as- suming the desired degree of elon- gation. This fact was sensed at the time, and it was decided to go no further with the mechanical skin- stretcher, as the construction of adequate clamps bade fair to be prohibitively expensive. A version of the skin stretcher usable for forming very deep leading edge sections was developed, but here again the clamping problem became a serious obstacle. Another reason for shifting the course of the investigation away from the mechanical stretcher lay in the fact that during the experi- ments on it, observations and cal- Cc Tes, x 5 2 > I—A typical double-con- aia shawl part. Restraint was applied along the aa’ and cc’ edges, with the abc edge showing the deeper contour and the ada’ edge the shallower contour. Extra punch depth F's. 2—Forming a shallow con- tour part by a deep punch. culations were made which indi- cated that the positive outward ac- tion of the clamps was not neces- sary and that adequate stretching action could be obtained from stretching dies equipped with clamping hold-down plates to re- strain the edges of the sheet under the action of the rubber punch in the single-acting hydraulic press. This principle was tried out on several practical parts and found to work quite satisfactorily. It was definitely established that enough stretching could be obtained from simple edge restraint to form even a fairly shallow part, and that restraint in both directions is not only unnecessary, but injur- ious. In other words, parts shaped as in Fig. 1 should be restrained only in one direction, which should be parallel to the deepest contour. With reference to the forming of the double contour, it was found ECOND of a series of four articles on IMPROVED AIRCRAFT FABRICATING TECHNIQUE developed by Lockheed Aircraft Corp. The first article, last week, dealt with “Drawing Dies for Air- frame Stampings," and the two articles to follow are ‘Forming Con- vex Flanges and Joggles," Platens." 50—THE IRON AGE, June 4, 1942 and “Hydro-Press Forming With Rubber that if a part has in one direction a rather shallow contour (ada’), and in the other a deeper contour (abe), stretching of the material by restraining it in the direction of the deeper contour (abc), while the punch is descending, will not only make the sheet assume the contour (abc) but will also make it assume the cross-contour (ada’), assuming, of course, that the punch itself carries these contours. At- tempts to rotate the process and restrain in the direction (ada’) gave poor results with excessive wrinkling. Additional tests have been initiated to study this phe- nomenon more fully. Another expedient that can be successfully used in forming parts of shallow contour is to use a punch deeper than required by the con- tour, the added depth stretching the material the required amount and the shallow contour being formed across the bottom section of the punch, as illustrated in Fig. 2. To date, no skins have been encount- ered that cannot be formed success- fully by this means. Therefore, it seems unnecessary to give further thought to a possible machine with positive horizontal stretching force. Double-Acting Press The development of stretch dies for the single-acting press gave vir- tual assurance, not only of success- ful performance of the stretching operation in the double-acting press, but of even better results than those obtainable in the single- acting press. Since installation of the double-acting press at Lock- heed, this prediction has been well verified. The use of the double-acting press in a stretching operation is illustrated in Fig. 3. The punch is attached to the main ram, and there is no female or bottoming die. The place of the latter in sup- porting the hold-down plates is taken by the heavy rails shown at either side of the punch. The ma- terial is gripped between the rails and the hold-down plates which are in turn loaded by the rods passing through the main ram up to the hold-down ram. The reasons for the superior ac- tion of this method are as follows: (1) Because of the powerful in- dependent hold-down ram, the re- straining plates can be made flat and smooth, whereas with the sin- gle-acting press it is difficult to exert enough restraint through the action of the rubber punch on the hold-down plates, to eliminate the necessity of beading or corrugating the latter and so introducing a ten- dency to tear the sheet. (2) The presence of the bottom- ing die and rubber punch in the single-acting press set-up gives ir- regularities of frictional contact and stretching action. In the double-acting press this bottoming or female die is eliminated and the material is stretched quite uni- formly by the free descent of the polished and lubricated Kirksite punch. (3) The variable human element involved in stacking rubber, etc., in the single-acting press is elimi- nated in the double-acting press. Once the proper amount of “drape” to give the sheet before it is clamped in position has been de- termined by trial or calculation, this can be marked on all other sheets so that a uniform product results. The set-up shown in Fig. 3 was made for forming nacelle skins, which heretofore had been formed only in the SO condition and by a time-consuming process of hand rolling. In the double-acting press, the skins were formed in the ST condition at the rate of 90 parts F IG. 3—This stretching set-up in ce double-acting press is used in forming nacelle skins for airplanes at Lockheed Aircraft Corp. per hr. Fig. 4 shows the perfec- tion and uniformity of a production run of these nacelle skins, and the slight contour in the transverse di- rection is clearly shown in the pro- file view. This was a pioneer stretching set-up for the double-acting press. Results were so successful that plans rapidly have been made to form other parts of a similar na- ture in the same manner. Another early success was that achieved with the forming of cowling panels in %4H stainless steel, using the stretching set-up. There seems to be no reason why large fuselage skins cannot be formed by stretching in the double- acting press. It has been found that skins with very shallow con- tour in the longitudinal direction can be laid in place and fitted by hand, so that it may prove unnec- essary to preform these at all. Others of deeper section should re- spond well to the stretching proc- ess, although extensions will be needed on the platen of the double- acting press. A few sections with “saddleback” contour may prove a problem. Although the present study was undertaken primarily to solve the problem of forming parts of shallow contour, such as skins, it has been found that the stretching principle is equally applicable to forming parts which have a deep THE IRON AGE, June 4, 1942—5! contour, such as leading edge sec- tions. The only limitation is that the deep contour can be in one di-. rection only. Under such a con- dition the stretching process is readily applied by “draping” the sheet between the rails in such a way that when the punch descends, it stretches the material just enough to produce permanent set and so eliminate springback, but not enough to result in rupture. In such a process it is essential that the supporting rails have a large smooth radius and that there is sufficient clearance between rails and punch to avoid severe bending and pinching of the material. If these conditions are complied with, little difficulty is experienced in stretching even quite deep leading- edge sections on the double-acting press. It is to be noted that the process of forming a leading edge is not “deep drawing,” even though the part looks deep. Actually, the part exhibits only a relatively slight de- parture in form from a cylindrical surface, which could be formed without either drawing or stretch- ing. The latter operations are only required to form whatever devia- tion in cuntour there may be from a cylindrical or other developable surface. So long as this deviation is slight, as in the case of the skins shown in Fig. 4, a stretching oper- ation is in order. If the deviation should become very great, as in a curved wing tip for example, then a drawing operation would have to be used. The drawing involves compression of the metal in one direction while it is stretched in the other. A typical deep drawing operation is that involved in form- ing a cylindrical cup, wherein the metal flows inward from the flange into the walls of the cup as the punch descends. A draw-ring is used with enough hold-down pres- sure to prevent wrinkling of the flange, but not enough to stop the actual flow of the metal inward to the cup. Compressive action oc- curs in the circumferential direc- tion around the flange as the metal in each wedge-shaped section there- of flows inward toward the rim of the cup.* *“Mechanics of Deep Drawing Sheet Metal Parts,” Aero Digest, February, 1942. No such action occurs in forming parts such as the leading edge, hav- ing only one deep contour. There is no flow under the hold-down 52—THE IRON AGE, June 4, 1942 pads; they clamp the metal tightly. A shallow cross-contour may be formed simultaneously, as already described; but if the cross-contour were to become deep, the part would become dome-like or ellip- soidal in shape and would then present a difficult problem in deep drawing. 5 IG. 4—A production run of na- celle skins. The depth of con- tour in the transverse direction can be seen in the gg view of the SKINS. It is to be noted that parts which should be drawn are sometimes in- advertently stretched by using too great a pressure on the draw-ring; but this results in premature fail- ure of the material and should not be confused with the stretching process as applied to correctly se- lected parts. It is quite possible to use a “stretching machine” in place of the double-acting press in stretch- forming operations. This machine has mechanically or hydraulically operated clamps which grip the sheet while it is being formed by the motion of a punch. No positive outward stretching force is applied to the clamps; hence it does not operate on the principle of the me- chanical stretcher tried at Lock- heed, but simply on the same prin- ciple as the double-acting press. However, without the powerful hold-down ram of the double-acting press, it is difficult to develop a very high pressure in the clamps. As a substitute for high pressure, serrated clamps seem to be in use with most stretching machines in use at the present time. As already pointed out, these tend to tear the sheet within the grips. Of course, it is possible that the clamps could be so designed as to apply enough pressure (10,000 to 15,000 Ib. per sq. in. according to work done at Lockheed) to allow the use of flat, fairly smooth grips. In this case, the machine should be the equal of the double-acting press, provided that means can be found for insert- ing and removing sheets as quickly as can be done in the press. It might be thought that the pos- sibility of alining the grips in the stretching machine with the direc- tion of the sheet would offer a pos- sible advantage. It has already been pointed out that even for quite deep parts, no trouble seems to be experienced in the double-act- ing press due to the material bend- ing over the edges of the flat sup- porting rails, provided proper radii and punch clearance are used. Technique of Stretching Tests and observation have re- vealed that the following factors are important in stretch forming on the double-acting press: (1) Permissible elongation of the ma- terial; (2) elongation required to form the part; (3) shape of the rails over which the material is stretched; (4) radii on the rails over which the material is stretched and on the punch; (5) surface con- dition of the punch, and (6) lub- ricant used or the punch. It has been found that allowable elongations in 2-in. gage lengths, as given in the customary handbook data, are not applicable for deter- mining the limits of stretch form- ing. For example, for 24ST Alclad the Aluminum Co. of America specifies minimum elongations from 12 to 15 per cent, and stand- ard tensile coupons on average ma- terial usually show about 18 per cent. However, experience indi- cated that maximum elongations of only 8 to 10 per cent were being obtained in stretch forming this material. Accordingly, some tests were made by stretching strips of ma- terial 12 in. wide and 48 in. to 72 in. long, using a polished Kirksite punch. It was found that a max- imum elongation ‘of 10 per cent is all that can be counted on in stretching long pieces of 24SO or 24ST Alclad. It requires great care and careful polishing and lu- brication to achieve this value; and under practical production condi- tions it is not considered advisable to try to form any part by stretch- ing which requires an overall elon- gation of more than 7 per cent for 24SO Alclad and 8 per cent for 24ST Alclad. Recent experiments with form- ing the trailing edge of a stabilizer tip have revealed that an overall stretch up to 12 per cent can be obtained by using 61SW; or by stretching 24SO or 24ST about half way, solution heat-treating, and then completing the operation. There is very little difference be- tween the limits of stretching 24SO and 24ST where long distances are involved; but the elongations ob- tainable from 24ST appear to be somewhat more consistent than from 24SO. Observations during the stretch- ing tests indicated that elongations as high as 17 per cent were sus- tained in 24ST material at locations where it did not come into contact with the punch. This and other ev- idence indicates that the major cause for the apparent loss in ductility of the material lies in frictional effects occuring where the material is in contact with the punch. Lateral restraint produced by the punch friction may also in- troduce secondary crosswise tensile strains which lower the effective ductility. Some tests on panels 5 x 6 in. in size, compared with results on standard narrow tensile coupons, indicated that the width of the sheet being stretched has little or no effect on the allowable elonga- tion. It is, of course, necessary to keep the elongations required in forming the part below the limiting values described. Usually an elon- gation of only a few per cent suf- fices to produce permanent set. In many cases the part can be “draped” in the press to achieve the desired results, and the amount of “drape” can be calculated in ad- vance from the contour of the part or ascertained by trial and error. Sometimes the part is not so shaped that it can be successfully “draped,” r IG. 5—A plan view of the hold down rails. The edges marked "A" must be straight lines in this view. and in such a case the possibility of stretching is definitely deter- mined by the shape of the part. The use of analytical curves in aircraft design, in place of “faired-in” surfaces, would often greatly fa- cilitate the advance calculation of formability of certain types of parts. Present information indicates that the rails must, for most work, have straight sides in the plan view as shown in Fig. 5. The inner edges of the rails do not have to be parallel, however, for successful forming. The radius on the edge of the rails over which the material is being stretched should be kept as large as possible, preferably 1 in. or greater. This is necessary in order to prevent the strains in the sheet from becoming excessively large due to bending around the radius. When the part is of shallow con- tour it has to be formed by over- stretching by means of an extra oo 6—The radii on punches used for over-stretching a shal- low part should be I!/, in., as shown in "'R" in this illustration. deep punch, as indicated in Fig. 2. In this case radii of at least 1% in. are needed on the corners of the punch, as shown in Fig. 6. Since friction between the ma- terial being formed and the punch is such an important factor in the elongation obtainable in the ma- terial, it is essential to polish the surface of the punch. The punch used in early stretching experi- ments was cast lead. Results from this material were not very good, and it proved necessary to form the punch of Kirksite with a good polish. The need for a good lubricant for this type of forming, as well as for deep drawing, is well recog- nized. The extreme pressures en- countered in drawing are not pres- ent in stretching, so that most of the better drawing oils will serve satisfactorily as long as they do not break down below 150 deg. F., and will provide viscous lubrication up to about 5000 Ib. per sq. in. nor- mal pressure. Experience to date indicates that material should always be re- strained in one direction only, parallel to the deepest contour to be formed, as indicated in Fig. 1. Further study is being given to this subject. As emphasized, the hold- down pads and rails should have flat, almost smooth surfaces. No serrations or corrugations should be used. Stainless steel is well adapted to the stretch-forming process, even the 14 hard temper being capable of sustaining at least as much stretch as 24ST. The annealed ma- terial will stretch quite extensively. A better grade of lubricant, how- ever, is needed in some cases, than for Alclad materials. Bibliography '“Elastic Theory as a Tool in Sheet Metal Forming Problems,” F. R. Shanley. Paper presented at the an- nual meeting of the Institute of the Aeronautical Sciences, Jan. 28 to 30, 1942. *“Junkers Stretching Press Tech- nique,” Aircraft Engineering, April, 1937, and August, 1940. *“German Production Equipment,” Aircraft Engineering, K. Frydag, October, 1940, p. 314. ; ‘“Men and Machines,” Automotive Industries, April 1, 1940. *“Special Machines Designed for Flexibility in Aircraft Production,” H. A. Berliner, Aero Digest, Janu- ary, 1939. *““Cutting and Forming Sheet Metal Parts,” Aero Digest, January, 1939. *Pressings in Aeroplane Construc- tion,” E. J. Ritter, Luftwissen, Vol. III, 1938, No. 7: Aircraft Engineer- ing, February, 1941. THE IRON AGE, June 4, 1942—53 not been a recent notion of Germany’s, and both indus- trially and economically, the coun- try began adjustments for such a project years ago. These adjust- ments have been proclaimed at vari- ous times both in Germany and abroad,- and some of them, espe- cially those of an industrial nature, might be considered by the Amer- ican plant operators. Germany has made an especially concentrated effort to conserve ma- terials with which to carry on the war, one of the most interesting of which has been the reclamation of light metal scrap, both magnesium and aluminum. A process for the ft ARRYING on a total war has ABOVE Fis. 2—The gas fired drying chamber of this furnace keeps revolving and catching the chips in longitudinal panels seen in the barrel. This agitation keeps the chips from burning, and aids in the drying. 54—THE IRON AGE, June 4, 1942 German Recovery recovery of aluminum scrap, dis- cussed by H. Schiek and H. Wal- bert, German technicians, points out that the production of new alu- minum in Germany could not pos- sibly keep up with the ever increas- ing demand, and therefore efficient scrap recovery was of growing im- portance. Furthermore, it was felt that recovery should be so effective in the German plants that the sec- ondary metal would be equal in quality to the virgin aluminum. The operation of one recovery plant was completely described. With the best modern scientific and technical equipment available, this plant was converting aluminum and aluminum alloy turnings into useful ° ° ° BELOW IG. |—After leav- ing the centrifugal dryer, the aluminum chips are passed up this automatic con- veyor into a furnace dryer where moisture is removed down to traces. ° ° ° ¢ Light alloys at very slight losses in metal. The recovered metal proves equal in quality to new material, and, since turnings are a considerable item in light metal scrap, their com- plete recovery is possible. Hereto- fore, recovery from turnings has been incomplete, due jointly to the lack of modern equipment and in- experienced operation. The inexpert operation of the recovery process means not only high losses by oxi- dation and low metal recovery, but also an inferior recovered product, to which the addition of virgin metal may mean a waste of good metal. Scrap Recovery Process The aluminum recovery plant de- scribed, apart from chemical and metallurgical laboratories, has a chip breaker, centrifuge for dispos- ing of oil on the turnings, a drying drum, a magnetic separator, a charging machine, and a melting furnace. These separate installa- tions are interconnected by mate- rial handling devices, and as many of the operations as possible are completely automatic. Metal Scrap The operation of the plant itself involves rather unusual operating practices. The turnings are col- lected for recovery and carefully weighed so that a loss and gain budget can be calculated at the end of the process. In handling and storing the turnings, they become interlocked and form firmly con- nected bales. For convenience of mechanical conveyance, these bales are passed through gyratory crush- ers that break the turnings down into small chips. The crusher is charged at the plant floor level so that one man can serve the machine adequately, and simultaneously do some rough sorting, such as remov- ing wood, paper, rags, etc. Following the crushing operation, moist or oil bearing chips are charged into a centrifugal drum where excess moisture or oil is re- moved. The oil that is separated from the chips by the centrifuge is recovered. After this first drying, chips are then conveyed by a screw feed to a drying drum furnace shown in Figs. 1 and 2, where the remainder of the moisture is re- moved, down to traces. This fur- nace is arranged horizontally and heated centrally through a hollow shaft by a gas burner. Guides in the furnace conduct the chips through the drum, forc- ing the metal to fall continuously on the free space where it is sur- rounded by hot furnace atmosphere, as illustrated in Fig. 2. The heat- ing is adjusted in such a manner that the chips, when removed, will contain 1 to 2 per cent moisture, because complete drying entails the danger of overheating and possibly burning the chips. This furnace drying creates con- siderable dust, which, with the water and oil vapors, is conducted through a suction pipe into an ex- haust chimney. To avoid the loss of chips through the draft, a sifter, probably of a baffle type, is in- stalled in the chimney, and is regu- larly removed and emptied of ac- cumulated material. A magnetic separator, Fig. 3, is used to remove ferrous admixtures in the aluminum turning scrap. For ..- A method of converting scrap aluminum turnings and chips into high grade usable metals, and the recovery program for aluminum and magnesium alloy scrap carried out in two German piston manufacturing plants are de- scribed herein. successful removal of such impuri- ties from the turnings, the par- ticles of scrap are kept at a fairly uniform size; the scrap is dried carefully; and there must be an optimum distribution of the mate- rial over the separator. The turn- ings are distributed evenly over the separator by a screw feed in a drum that forces them out on to an os- cillating surface of sheet steel. From this oscillating table, the chips progress over two permanent magnet rolls arranged one below and behind the other. This ar- rangement insures uniform flow of metal, steady and smooth feeding of chips, and the retention of all iron admixtures. However, care is taken to prevent the scrap from falling too vertically, so as to elimi- nate the possibility of having the chips bound, with the resulting incom- plete removal of iron. Freed of iron and steel, the chips progress to the 1G. 3—For removing the ferrous inclusions in the aluminum scrap. the chips are passed over these magnetic rolls. The feeder to the rolls oscillates laterally in such a manner that it evenly distributes the chips over the rolls. melting furnace. As hand charging requires about 15 to 20 min. per ton, during which time the gas in the furnace must. be throttled with resulting temperature drop in the furnace and the rapid deterioration of the refractory lining, all charg- ing is automatic. Charging time is reduced to 1 or 2 min., reflecting corresponding reductions in labor costs, heat losses, and time losses. The driving mechanism of the ro- tating drum type furnace charging machine is placed as low as possible to remove it from the area ex- posed to high heat radiations. Melting Fine turnings and chips, since they have large surface areas en- tailing the danger of burning, are THE IRON AGE, June 4, 1942—55 melted under a salt blanket. Fur- nace rotation permits immediate protection by the salt cover to the metal. On charging, an excess of salt is maintained and the caloric reserve of the bath is sufficient to prevent any marked cooling down of the furnace because of the cold chips.” Since there are traces of oil and dirt in the scrap charge, the salt becomes viscous and must be renewed after every five melts. Al- though there is a considerable con- sumption of salt in the bath, the higher cost of working with a salt blanket is more than offset by the higher yield and better quality of the product. Mechanically enclosed metal par- ticles can be recovered by breaking and grinding the slag cake; alumi- num oxide is recovered by leaching and filtering; and finally, some of the salt is recovered by concentra- tion and evaporation of the solution. The latter conservation is vitally FIs. 4—The variety of threads on this part made entirely from aluminum scrap remelted bespeak the quality of the recovered metal. German metallurgists claim that the re- covered metal is in no way inferior to virgin aluminum. important since the low tempera- ture melting salts commonly used are expensive. Attempts are being made by German technicians to re- cover the salt, and if successful, the complete cycle will permit much greater economy. Further evidence of the measures of stringent econ- omy in the German plants is the recovery of vapors carrying salts and particles of scrap metal that are caught in the flue exhaust filter. After melting in the furnace has been completed, the metal is cast into a movable trough and then into settling or alloying furnaces. Continuous metallurgical super- vision of the entire process is main- tained. Throughout the plant, metal- lurgical stations and testing depots insure that mechanical and manual operations proceed according to very strict schedules. The aluminum recovered from the scrap turnings by the process outlined is claimed to be free from Reclamation and Conservation of Metals .-+ This is No. 5 of a series of articles designed to aid industry obtain the utmost value from every pound of metal. 56—THE IRON AGE, June 4, 1942 1G. 5—Above shows the fine grain structure of the alu- minum recovered from turnings when the recovery processes are carefully controlled, while below shows the coarser and inferior grain structure of an ingot recovered from scrap but with the recovery processes not controlled so rigidly. inclusions and gases, well con- densed, and very high percentages, by weight, are reclaimed. The part shown in Fig. 4 was made from secondary metal produced from dross, the worst scrap obtainable. The variously pitched threads evi- dence that the metal is of high quality and fulfills considerable re- quirements. Density and excellent grain structure of metal recovered from scrap by the described method is shown in Fig. 5, above, while Fig. 5, below, shows a sample re- covered from remelted aluminum scrap, but without particular care being taken in the re-melting and the equipment used was not accord- ing to the standards observed in the plant described. Consequently, neither the grain structure nor the density of the sample is particularly desirable for further working into fabricated parts. Magnesium Recovery Another article, by Dr. E. Meyer- Raessler of the German Electron Works, describes the conservation and scrap recovery program for magnesium, aluminum, and light metal alloys as carried out in a plant that manufactures pistons for internal combustion engines. The author claims that the great den- sity of population and comparative scarcity of raw materials in Ger- many naturally focussed attention on the most frequent metals, alumi- num, and magnesium, many years ago. However, it was only when the German economy was reorganized and redirected after World War I that use was made of these metals. In 1921, cast iron was replaced as piston material by magnesium, and in 1925 magnesium die casting was introduced. In the same year, the first magnesium cast airplane wheel was produced in Germany, re- placing the usual wire spoked wheels. The process of metal conservation described by Dr. Meyer-Raessler is in use at the Mahle, K. G. and the Electron, G. m.b. H., plants at Stuttgart, Germany. It is designed to conserve the raw materials used only in the manufacture of light metal pistons, and recovery of the scrap from this product is complete. Apparently there have been ob- jections in Germany to the use of light metal scrap, but it took Pro- fessor Guertler of the German Four Years’ Plan organization to show that precise laboratory supervision and geod care in handling and proc- essing would produce a recovered metal that was in no way inferior to virgin metal. Magnesium and magnesium alloy scrap have always been melted and re-used to a large extent, but only recent research made the recovery of aluminum scrap possible. Naturally, in the manufacture of pistons, neither aluminum nor mag- nesium is used as a pure metal, but is always alloyed with copper, nickel, silicon, or some other agent that produces desired physical properties in the metal. However, some of these alloying elements are only available in a limited degree, and must therefore be used as spar- ingly as possible. While it seems strange to Americans, one of the main reasons for conserving light metal scrap in Germany lies in the recovery of the alloying elements. However, the war calls for a widened economy of metals in Ger- many, and recovery of the base light metal is becoming as impor- tant as the recovery of the alloying materials. In the German piston plants, metal is received in the alloyed state, ready for forming into pis- tons. In order to differentiate be- tween the stocked alloys, they are designated by colors. For example, bars of alloy EC 124 are marked blue and EC 138 bars are marked white. Also, letter and number symbols are shown on the material to indicate laboratory analyses. W right Aeronautical Corp.'s Metal Segregation System ETAILS of the Wright sal- vage plan for vital steel, aluminum and other high grade materials segregates the various metals as fast as they are re- moved from forgings and cast- ings by a machine tool. Machine tools ranging from small boring machines to massive turret lathes have bins attached which catch and hold all shavings and chips produced, and since “in-line” production methods are em- ployed, where a tool is used for one specific part only, the same kind of scrap always accumu- lates. Salvage collectors wheel large boxes along the aisles of the plant and collect the waste. To ro a foolproof method of eeping various alloys separated, The pistons manufactured are both forged and cast. As would be expected, cast pistons are produced directly from the ingot by casting the melted metal into the semi-fin- ished part, as shown in Fig. 6. The forged piston, however, passes through a number of shapes being worked down to the semi-finished state. The forged pistons, being more ductile and having higher physical properties than the cast part, are used only on heavy duty motors. The semi-finished pistons, either cast or forged, are collected in batches for finishing, being stacked until finishing can be done. Special reserves of off-size semi- finished pistons are maintained. Both casting and forging result in scrap. In casting, gates and risers are cut off, and in forging, the cropped top and bottom ends are scrapped. Furthermore, during sawing and rough turning, scrap is produced. As work on the pistons progresses, through the semi-fin- the bins on the tools are each marked with a color for a spe- cific grade of alloy, and the col- lectors’s boxes are similarly marked. Thus, a collector gath- ering steel, identified by a green and yellow mark, gathers the shavings and chips from every machine tool bearing a green and yellow card. Although steel, aluminum, and magnesium are the principal me- tals salvaged, the list also in- cludes copper, beryllium bronze, hosphor bronze, aluminum Saale brass and a variety of others. Monitors throughout the plant enforce strict observance of the salvage procedure regula- tions, and the same control of salvage has been applied to all non-metallic products. ishing and finishing operations on highly specialized machines, addi- tional scrap and chips are produced. In Table I is shown the weight com- parison between semi-finished and finished pistons and the scrap. The scrap resulting from the manufac- ture of pistons amounts to several tons per month, but care is taken to insure against loss of even the most minute chip. To save the turn- ings, all machines are equipped with catchers and every operator is responsible for the clear separa- tion and collection of all turnings according to their composition. Since these plants produce a va- riety of types of pistons, a great many different materials are re- quired and it cannot be avoided to work on a variety of materials in succession on a single machine. It therefore becomes quite a problem for the machine operator to keep different light metal alloys segre- gated. However, this is the respon- sibility of the operator. Depart- ments working with ferrous mate- ——OsXOSSSSSSlaSpql_Qwl"l"“"“™“_“ W"_O“™NON=“QDNOSO™NOO®ENOO®OEOSOSOl_™"=——= TABLE | Relation of Weight of Semi-Finished and Finished Piston to Chip Losses During Manufactu:'2 Semi-Finished Weight, Oz. Type of Piston Cast pistons: 74 mm. diameter 8.85 105 mm. diameter 63.49 Forged pistons: 63 mm. diameter 4! 18.48 105 mm. diameter 61.02 Finished Chip Weight, Weight, Oz. Ox. 6.24 6.14 52.03 11.46 12.34 2.61 40.39 20.63 OOOO —ooOoooaaaeeeeeeeeaeaeananaejejlelewesesSs THE IRON AGE, June 4, 1942—57 rials are separated from the rest of the plant so the iron content of alloys recovered by this careful supervision of individual machine operations can be kept low, l