The Iron Age 1944-08-31: Vol 154 Iss 9

VAN DEVENTER President and Editorial Director BAUR Vice-President General Manoger ° and Advertising Offices 100 East 42nd St., New York N.Y., Hayes, Production Manager. Baur, Typography and Layout Regional Business Managers New York New York 100 East 42nd St. 100 East 42nd ROBERT BLAIR GIBBS Cleveland Pittsburgh 1016 Guardian Bidg. 428 Park Chicago Chilton Bidg. 1134 Otis PEIRCE LEWIS WARREN 4 RAYMOND KAY Los Angeles 2420 Cheremoya ° and Published CHILTON COMPANY (incorporated) Executive Offices ‘Chestnut and Sts. 39, Pa., OFFICERS AND DIRECTORS MUSSELMAN, President GEORGE GRIFFITHS Vice-President BAUR Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JULIAN CHASE THOMAS KANE HARRY DUFFY CHARLES HEALE Member, Audit Bureau Circulations Member, Associated Business Papers als. lished every Subscription Price North America, South America and Single Copy, cents. ° The IRON AGE Vol. 154, No. Editorial Uncle Sam and the Goat Technical Articles Recent Developments Industrial Furnaces Tooling for Magnesium Welding Safety Insert Prevents Tap Breakage Organic Coating Aids Magnetic Inspection Torpedoes Assembed Machine Setups Vertical Oven Overcomes Shrinking Spoilage Insulation Steel Plant Equipment New Equipment Features News Front Assembly Line Washington West Coast Personals and Obituaries Fatigue Cracks Dear Editor This Industrial Week News Industry News and Markets New Rehabilitation Plan Mad House the Potomac Reconversion Plan Navy Biggest Storage Space Cancelled War Contracts Machine Tool News Non-Ferrous Metals News and Developments Non-Ferrous Metals Prices; Scrap Prices Iron and Steel Scrap News and Prices Comparison Prices Year Finished Iron and Steel Prices Steel and Warehouse Prices Semi-Finished and Tool Steel Prices Steel Pipe and Tubing Prices Wire Products Prices Pig Iron and Coke Prices Railroad Material and Stainless Steel Ferroalloy Prices Index Advertisers August 31, 1944 165 7 110 120 121 122 125 FOR BLANKING SILICON LAMINATION STEEL CROMOVAN FOR HIGH Where the production desired hundreds thousands millions pieces, air-hardening Cromovan used for die because its unusual depth and high resistance CROMOVAN wearing and cutting capacity several times that regular oil-hardening die steels and considerably more than that high-speed steel. Write for Bulletin. INVARO FOR SHORTER RUNS—Used for intermedjate production runs, oil-hardening Invaro maintains close tolerances longer than water-hardening carbon steels. Tools and dies made Invaro can used without grinding after heat treatment; sess uniform surface hardness; have excellent cutting properties; are tough and durable. Send for Invaro Bulletin STEEL COMPANY - DA YTOR - DETROIT - CAGO « | AD ELES 26—THE IRON AGE, August 1944 the pieces, times els and n. for much steels. used IRON AGE ESTABLISHED August 1944 ° VAN DEVENTER President and Editorial BAUR and General Manager ° ° ° DIX Manager, Reader Service ° ° ° Editorial Associate Editors ALBIN JOHN ANTHONY BARMASEL Assistants WILLIAMS ROGERS VAN CAMP MUNZER O'CONNOR MILLER Regional News and Technical Pittsburgh 428 Park Bidg. 1134 MOFFETT BROWNE EUGENE HARDY Washington National MacDONALD Cleveland 1016 Guardian BRAMS Detroit Woodward OSGOOD MURDOCK San Francisco 1355 Market St. Correspondents ROBERT PENLEY Buffalo FRAZAR Boston HUGH SHARP Milwaukee SANDERSON Toronto, Ont. RAYMOND KAY Los Angeles JOHN McCUNE Birmingham ROY EDMONDS St. DOUGLAS Uncle Sam and the Goat FRIEND mine said the other day: “Funny, isn’t it, that sel- dom see picture Uncle Sam any more?” had not thought that before but, coming think it, you not often see the chin-whiskered visage the smart old gentleman nowadays. few years ago, you met him almost every day somewhere. During the first World War there was scarcely any issue newspaper magazine that did not portray him prominently. peered you from thousands billboards too, all over the country, asking you buy Liberty Bonds. “Liberty” Bonds. Today it’s War Bonds. The word “liberty” and Uncle Sam knew him seem have gone out style together. Old Uncle Sam was certainly smart looking gentleman. You could tell one look that nobody could fool him, least for very long. You couldn’t tell him that hair could made grow billiard ball that you could lift yourself your bootstraps. would say: mighty interesting, sonny, but have prove before recom- mend nephews and nieces.’ You could tell, too, one look Uncle Sam was mighty good poker player whom you could back with your dollar with your two bits, whichever you happened have your pants’ pocket. Nobody could bluff him straight game and knew enough about human nature not sit one home abroad where the opponents had marked deck extra aces. One look Uncle Sam and you knew that was man few words who meant what said, did what promised and was mighty careful not promise more than could perform. thought you were wrong, would try put you right kindly way; you per- sisted doing wrong, would not call you names but would swing that number fourteen boot his where would the most good. old-timers, Uncle Sam resembled the men who built this coun- try and its industries and made what is. had keen eye and while liked look the stars night, did not dream the daytime. Daytimes was busy working and making work for others. knew that work came from the ground and not from the sky. Our youngsters haven’t had much chance get acquainted with the real Uncle Sam. afraid some them think him composite picture Santa Claus, Hollywood pinup girl and fat little guy with horn-rimmed glasses, marcel wave and degree economics. Too bad they have turned his picture the wall. Maybe it’s because those chin whiskers. Too many people might get the idea that the “powers that be” were making goat out him! Inland Hi-Steel buckets, truck bodies, screens, chutes, etc., are giving many times the service obtained from other steels. COSTS TOPPLE TIPPLE Screens, Chutes and conveyors Inland Hi-Steel Have Outlasted Mild Steel times and Are Still Going Strong! The facts behind this story lower costs began six years ago when Inland Hi-Steel replaced mild steel for buckets, truck bodies, screens, and conveyors the tipple Maumee Collieries. The mine records indicate that mild steel failed every months due the abrasive action the coal. The same records show that Inland with its high resistance abrasion this type service, has been use for over years without single replacement and that still going strong. 28—THE IRON AGE, August 31, 1944 After the first year,when the higher cost Inland Hi-Steel was paid through sav- every ton coal that traveled down the chutes, through the screens and over the conveyors was handled less cost. Inland Hi-Steel not only abrasion and corrosion resistant, but its high-strength means weight saving well. doing many important war and peace jobs where these favorable characteristics mean sav- ings time, labor and materials. Write for the Inland Hi-Steel Bulletin. Inland Steel Company, So. Dearborn Street, Chicago Illinois. District Sales Offices: Cincinnati, Detroit, Kansas City, Milwaukee, New York. St. Louis, St. Paul. dia tin the News FRONT August 29, 1944 This week for the first time since April 10, 1941, there change THE IRON steel scrap composite price. General weakness the scrap market has resulted lowering heavy melting scrap prices, making the composite $18.84. Farmers are being advised their influential trade magazines that the war's end sight, and that they should sell, sell, rid everything from wheat For, said, "inventory losses can wipe out profits from several years’ work." new electroplate, ternary deposit copper, tin and zinc, has made available commercially Co., which sole agent for marketing and servicing. The coating bright deposited, non-magnetic field and its reflectivity approaches that silver. And: This new coating has high tarnish resistance, superior corrosion protective hard, abrasion resistant and eaSily soldered with non-corrosive flux. can formed without chipping where the deposit does not exceed 0.0002 in. thickness. Application recommended particularly for copper and brass, but can mde steel following initial plating copper. The British are employing their fighters for interception over Use being made them knock down flying bombs. Allied pilots have reported four types German fighters raids. Two Heinkel's, Nos. 280 and 219; and two Messerschmitt's, Nos. 262. Allied espionage was particularly good reporting details these German jet fighters prior their use. For months Allied pilots have been studying scale models the planes, and this enabled them recognize the revolutionary aircraft diately. All these German planes are reported However, the probably oxygen along with some other liquefied fuel, and the explosion not tinuous like skyrocket but rather short and rapid bursts. The plane phenomenal the air, but has operational time limit min. This the first airplane ever fly rocket power, and such years ahead its time. All opinion that the engines would reign for transition period between conventionally powered aircraft and rocket aircraft. American aircraft will likely used against the Japanese before the war's end. Whereas motors and the Bell twin-engine jet have received all the publicity, some guesses are that even more important developments are taking place elsewhere. The jet impulse motor the German flying bomb the most simple motor ever developed. the cheapest known method delivering explosives distances beyond artillery range. The motor, ordinary steel tube narrowed venturi the rear, has front end, each grid opening closed spring flap. Gasoline continually air pressure into the body the tube and the firing plug located near the venturi. leaving the launching ramp the rush air forces the flaps open, air pressure builds the body the tube, and when pressure and gasoline mixture builds point the mixture fires. Recoil the gases out the venturi acting against the flaps closes them, just like banging ordinary door, and the assembly driven forward. One major mystery was the firing plug. Examination many bombs showed electrical distributor arrangement. now pretty well lished that the firing plug wire which always white hot and automatically fires the air-gas mixture pressure and gasoline concentration builds flash ; q Recent One the most stimulating meetings the semi-annual con- vention the ASME held Pittsburgh June (for full re- port, see The IRON AGE, June 29) was the panel discussion trends furnace design. complete summation this forum herein presented with emphasis the fundamental concepts heat transfer, energy balance, physical chemistry and materials construction. report- ing tech- nical ad- vances indus- trial furnace de- sign from repre- sentatives some different groups enor- mously stimulating anyone inter- ested progress field which has changed profoundly the last two decades. The advances reported could grouped for discussion many different ways. Perhaps use- ful any discuss them evi- dence progress the application those basic fields engineering and science which underlie the whole field furnace and kiln design. These are the fields heat transfer, energy balance, mechanics (including fluid mechan- ics), materials construction, chem- process control and combustion. Heat Transfer There are today very few processes for which there not basis for fair estimation heat transfer rate, terms local conditions. That is, with shape and size and temperature heat transfer surface specified, and with flow pattern, composition and temperature the ambient medium specified, there today ade- quate knowledge for prediction local heat transfer rate. many (and perhaps most) furnace design problems, however, there little com- fort, and less help, obtained from the above statement. The miss- 30—THE IRON AGE, August 1944 HOTTEL Professor, Massachusetts Technology, Cambridge, Mass. ° ing information many indus- trial furnace de- sign problems the precise de- local conditions, de- scription which defies the engineer and forces him accept empirical formulations transfer rates terms end against local con- ditions, and refrain from attempt- disentangle the contribu- tions forced convection, free con- vection, non-luminous and luminous gas radiation, and solid-to-solid radi- ation establishing the rate trans- fer the stock. Examples improved application heat transfer principles mentioned the brief reports presented the ASME panel discussion include the following: (1) The increased recognition, the heating stock through large temperature interval, the istence different ranges permis- sible preferred heating rates, lead- ing the use energy sources different potentials for different parts the process. Such tailored heat transfer rates are common electric resistor furnace design; fuel-fired furnaces they impose more design problem. Three the con- tributions the discussion referred the heating steel billets, all with the idea focusing attention what the billet can take rather than what the furnace can give. One speaker (Mawhinney) referred the possible use different levels available heat approach the problem cutting down the period high- temperature punishment the sur- face; one (Bloom) described experi- ments which indicate what heating rates are now attained, pre- liminary increasing them cer- tain ranges operation; one kis) interested calculations unsteady-state heat flow establish new criteria (or, rather, make old criteria more quantitative) per- missible heating rates. further ex- ample the application the prin- ciple varying the potential heat available comes from con- tributor (Levin) who called attention the induction furnace field where heating process described which slow (relative term) combined heating-soaking operation followed faster surface temperature rise. still further example tailoring the local transfer rates the needs the various parts the fur- nace comes from the contributor (Kniveton) who describes the use burner placement control local rates. (2) The extension the field convection heat transfer, evidenced the contributor (Gamble) who gives 1750 deg. temperature level which forced convection heat- ing now effectively used. Without trying too specific about where the dividing line comes, de- signers have carved off the low-tem- perature region for convection and high-temperature region for radiation. certain fields, notably refinery tube-still design, has been said that the greater the fraction the total heat transfer which carried out the radiant section the furnace, the better the design, that the cheaper for given job done. ing out pre Furnaces vol he: set ‘ | sa m eaker ssible ilable high- sur- ating pre- cer- asch- old per- ex- prin- vhich con- ntion ere vhich bined owed rise. the fur- local need who iture heat- hout here de- tem- and tion. nery that the one. However, the inability radiation around corners makes many heat- ing operations benefit increased use ing out differences heating rates outside and inside surfaces. Many problems stock packing relation the establishing local heat trans- fer rates have been solved empirically and with good success. oppor- tunity open for further improve- ment study the principles in- volved, and the student convection heat transfer will the future find himself more and more concerned with problems the field aerody- namics. Many engineers know how set flow system obtain con- vection coefficient almost any de- sired magnitude. But most them say too much! Far fewer know how obtain the minimum pressure drop consistent with given heat transfer rate. (3) The use different mechan- ism heat transfer old job (better, sometimes). This what makes furnace The use salt-bath volves change both the medium and the temperature level the heat sink. The use salt-baths fer pro- tected heating parts 2150 2400 deg. (referred both Solakian and Rosseau) substitutes liquid-film for gas-film coefficient the stock surface. The use gas quenching with high-velocity jets. (Cone) reverses the substitution; gas film replaces liquid film! (4) The protective cooling fur- nace parts. Mention has been made the water-cooling critical fur- nace parts contributors. Higher-temperature forced-convection furnaces necessitate the cooling fan shafts and bearings (Gamble); the introduction electrode cooling glands and water-cooling pipes the roof rings electric arc-melting furnaces has greatly increased fur- nace life (Watson). much for application heat transfer Energy Balance less important good furnace the proper exploitation generalizations which can made from the energy balance This enough more fundamental than heat transfer have received earlier consideration. Greater heat economy better quality control shared with one an- other the for the early trend from continuous furnaces. hot carburizing box from furnace Lindberg Steel Treating Co. trend comes from one contributors (Webber) who describes the heat economy that comes from combining several operations single furnace such way eliminate complete cooling steps the parts being processed. Here again the advantage solely that heat economy more im- portant are the simplified handling and the qudlity control. Enormous opportunity exists for the integration successive furnace operations, which the brazing-heat treating case one example. Mechanics easy build something with large safety factor that the de- signer cannot possibly embarrassed structural failure. The use higher and higher temperature levels various furnace operations leaves very little any safety factor many designs, and the designer forced make the best use his highest temperature furnaces cannot afforded. Rotational unbalance fans for high temperature recircu- lating furnaces cannot afforded, pointed out (Gamble). Controlled warpage fans and furnace parts, referred the same paper, comes from more well load stresses. Those the industry who furnish new and better construction are not materials magicians, and designers must learn use available materials more ef- fectively. Possibly able squeezed the present general heading, that amplified include fluid important development men- tioned Dr. Robson, namely, the use venturi injector pump hot air with cold and thereby eliminate the hot fan. will interesting watch the extent application this principle, lower mechanical efficiency than fan, but having its compensating advantages simpli- fied upkeep and temperature level limited refractories rather than Materials Construction Progress this very important field had been mentioned several papers. listing good alloys for various uses, and cheaper and many cases good enough substitutes for alloys has been made (Sayles). most interesting research (Stafford) the adverse effect reducing gases, and even the load- bearing properties insulating fire- brick doubtless explains many failures which had previously been classed here, often the case, the ac- quisition quantitative knowledge concerning deficiency predeces- sor its Other interesting ex- amples progress materials construction are the development THE IRON AGE, August FIG. 2—Salt heat treating the American Twist Drill Co. ° better electrode alloys for immersed- electrode salt baths and better refrac- tory pots for the same use (Solakian and Rosseau). There doubt that some the reticence concerning new materials construction conse- quence their being the secrecy list for the duration. may hopefully expected that the war will have uncovered new materials en- gineering. Chemical Process Control Chemical’ processing furnaces such did not come for discussion the panel, but any heating opera- tion involving material which re- quires surface protection obviously presents problem chemical con- touched this problem. Bright gas quenching, recarburizing, use neu- tral atmospheres for clean forging, and gas pickling were mentioned (Cone). Salt baths offer another means protected heating. Protec- tion exploiting the differences be- tween the activity hot and cold atmospheres possibility induc- tion heating (Levin). Protection simple control prevent unnecessarily high excess air has been mentioned one contributor (Mawhinney). This particularly 32—THE IRON AGE, 1944 ° ° mteresting example because old and yet important. doubt- ful whether any single advance fur- nace design yield much divi- dends increased control over the air-fuel ratio. talk other advances while there much room for improvement here faintly similar discussing the be- fore one can add. Combustion Combustion one process which many have for long taken for granted. References patterned combustion the use burner-combustion chamber combina- tions (Kniveton), and the advan- tages better combustion steel re- heating furnace operations (Maw- hinney), constituted the only mention of. trends combustion. all pres- ent were electric furnace engineers there would justifiably little inter- est combustion. There doubt that electric furnaces can some things better than fuel-fired furnaces and certainly they merit important place among industrial furnace types. also true that fuel-fired furnaces have given the electric furnace some fields use which they need not have given the combustion process were under better control. burn fuel and then transfer heat from presents two problems, each moderately well known. carry out the operations simultaneously raise much more cheaper operation. Some operations put such demand the heating schedule most safely handled transfer. Some are gross, in- sensitive conditions atmosphere and transfer rate, easily han- dled furnace which combines combustion and heat transfer, even though poorly. Some are borderline jobs, able handled fuel-fired furnaces which mix the combustion and the heat transfer process provid- ing they proper job it. Only the last few years has there been any precise knowledge the mixing pattern around open fuel gas jet and complete story mixing simple jet with orifice-controlled air injection and certain amount self-generated recirculating still missing. Flame requirement for combustion, perfect mixing that combustion products the front where they pass over the stock are uniform composition—not only judged comparing long-time samples, but even comparing snap samples taken one-hundreth second (uniform composition judged Maxwell demon)—these are problems about which little known. not out turn call attention the fact that there are gas turbine combustion power plants that fly—the newspapers and maga- zines have described them. takes little imagination see what enor- tern control have had solved make such power plants sufficiently compact practical. takes but little see that com- bustion attained are completely outside the field industrial furnace experience, and takes but brief search the literature see how little there was the way guid- ance the solution the problems involved. may expected, then, that pre-war experiences will serve enormous impetus industrial furnace design, and the forward-look- ing furnace designer will recognize potentialities application the new knowledge the field better atmosphere control, better flame placement, and consequently closer approach the ultimate job tailoring the combustion transfer process the needs the stock. a mt al ‘ a 7 ing for magnesium welding are many respects similar those other metals. The exceptions are due the characteristics the magnesium. Before the more critical aspects tooling design are dwelled upon, the following cautions re- quirements should observed: The jig framework support- ing structure should heavy enough adequately support the remaining structure the required tolerances, and still not excessively bulky interfere with the operator’s move- ments around the jig. Mounts for trunnions are prime requisite and may either hand power driven; the worm gear type being the most practical for ease operation and the safety factor involved (Fig. 1). The jig structure that holds the parts being welded should strong enough and properly supported critical points withstand welding strains, maintain dimensions, and provide sufficient cooling factor that distortion and warping ‘the magnesium can held minimum. two inter-related factors which must given consideration when design- ing weld jig. Neither them may necessary allow for, and make cor- rections when the amount and direc- tion movement the magnesium has been determined each part in- volved. There fixed constant that can used predetermine the amount error allow for since dependent the personal element welding, well the size the assembly, their design and the condition the magnesium. The condition the magnesium will vary depending the forming the part sheet. Whether roll- ing, braking, stamping, hot cold forming, heat treated annealed. Unless the stresses set the mag- nesium such forming have been relieved, buckling and distortion can caused parts which have high Tooling Magnesium Welding Allowance for expansion and contraction magnesium poses special requirements for rigid sup porting the welded structure. designing jigs and holding devices, the problem not only relieve welding strains but accommodate also for another warp- ing factor, the locked-in strains resulting from prior operations done the magnesium such as, rolling, braking, hot and cold forming and heat treating. Towards this end, the author presents analysis hold down devices, stiffeners and other tool elements and illustrates the adaptability heavy drop hammer dies for the bases the welding jigs. locked strains caused the initial forming. every pos- sible instance the design the jig should that the welded part assembly can retained the jig and placed heat treat oven and annealed before the clamps are removed. This will insure the correct contour relations surfaces when removed from the jig, otherwise the locked strains can cause warp- ing while reliev- ing the welding strains. large assemblies where obvious that would im- practical put the jig oven even transport it, torch relieving and hand work- ing may em- ployed. The jig should acces- the welding involved and also for the workers comfort and convenience. Poor welds partly KENNETH KIME Production Engineering, Northrop Inc. Hawthorne, Cal. cramped working positions. The clamp- ing devices that hold the parts being welded should quate for the purpose and sufficient numbers, yet they should placed not obstruct the welders move- ment, and they should quick act- ing and positive. Several examples ° ° ° Worm gear type mount for supporting jig structure. 4 THE IRON AGE, August 1944—33 isfer well nore ting dled heat here han- ines even rline fired been xing jet air still pace fect ucts the -not nap hese call ants nor- but rief nid- rial nize the eat the will illustrated later; there are, however, unlimited possibilities for ingenuity and resourcefulness de- signing holding devices indicated the immediate tooling problem. many cases will advan- tageous incorporate drill fixtures the weld jigs drill critical holes. This will true where would difficult too expensive duplicate the tool just drill the holes. Actu- ally all critical holes should drilled after strain relieving and before the part has been removed from the jig. Extra Compensating Metal Sufficient excess material trim must added the required amount INCORRECT TENSION magnesium sheet caused improper restraining force hold downs. for the sheet extrusion being welded. This extra material used for shrinkage caused the welding and trimmed the welding progresses. this manner the amount shrinkage limited the last weld and can practically eliminated adjustment the jig after several assemblies have been built and the amount shrinkage has been determined. The tooling will allow for the extra size the part and the same time restrict the size the hold one edge dimension, the other edges must free move. Two edges may held stopped but manner that they not limit the movement one direction; that is, the edges held must not op- posite parallel. Also some allowance should made for expansion when clamping directly against the welded part the direction the expansion. Spring loaded clamps jacks may de- vised suit the particular job. Pre- heating would the best method but any case some provision must made accommodate the expansion the material. For welded skin sheets as- semblies built one more sections, the weld jig may designed over- 34—THE IRON AGE, August 1944 1G. 2—Sheets are drawn due de- posit more molten metal topside. size that when the cast weld made the parts will shrink the de- sired dimension. The amount over- size can only approximated for the first setup. When the finished parts are checked, corrections may made the jig bring the finished part the proper size for the next as- sembly made the jig. The results will uniform only after welding ACK Material thickness RIGHT Setback distances hold down plates. O00 ww sequence has been worked out for the jig and strictly adhered to. all cases the confined the last weld pre- vent accumulation errors; also the welding strains should worked out each weld before the next bead started. This will prevent the accumulation weld- ing strains the structure incor- poration locked stresses and the welded parts will fit into the jig and not have forced into position. When parts are forced into posi- tion and welded, strain re- lieving will not remove these additional locked These can have adverse effect when the structure tested under actual load. PLATES Fis. force hold downs permits magnesium expansion movement. HOLD DOWN PLATE SET BEVEL FOR HOLD DOWN CORRECT TENSION What might have been adequately designed structure may show unfavor- ably under test. the parts had been properly strain relieved and fitted, the design would have been ade- quate for the load applied. Types Jigs Care must exercised design ing male jigs fixtures where cover close the jig the outside. The weld- assembly can shrink tight and impossible remove unless the jig can relieved eollapsed from the inside. .In such cases female jig preferred provided the design requirements can met, although Weld BUTT TEE WELD wn the oversize allowance for shrinkage somewhat more difficult obtain. Female jigs for partial full monocoque sections, and for this type construction and jig the weld seams should the inner surface the skin. The reason for this evident the sketch. Fig. tion depos the heate plate Adva femal quire wher resul addit weldi male pone the are 0.40 0.50 060 min atta For ran the ter AK er had and kage tain. for ions, jig nner for > 9 When the sheets are welded they will drawn shown. This condi- tion due more molten metal being deposited the greater opening the top the weld seam. The area heated greater this side because the cooling effect the back-up plate the other side the sheet. Advantage this may taken female jig since less forming re- quired restore the desired whereas male jig flat spot will result that difficult remove. addition, the female jig leaves the in- terior clear for locating frames, stiff- eners and longitudinals. Access for welding and clamping devices male jig would require extra jig com- ponents, one for the skin and one for the inside structure. Clamping devices for cover sheets are more easily installed female jig and more positive action can attained female than male jigs. For cover sheets, wrap-around ar- rangements are about all that can Use Hold Downs Hold down strips plates should used along all weld seams. They serve twofold service; first, clamp hold the material place and second, cooling medium, re- moving the heat from the vicinity the weld more rapidly than the ma- terial radiated the heat into the air. The hold down strips should wide practical. they are too harrow they require more clamps and not have the rigidity resist buckling the material. some 5—Distortion resulting when stif- fener not properly held. places narrow strips will necessary but wherever possible they should wide the space permits. Four inches width good average for material 0.093 in. thickness. weld jig for fusil- age structure. (En- circled portions are shown enlarged Figs. 14.) The thiekness the plates and strips should in. except where contours make the forming the ma- terial difficult. terial used should thick the forming allows. The edge adjacent the welding should for accessibility the weld seam. the edges the plates are not beveled and the edges are too close the weld seam the are may jump the hold down plate. Hence the distance from the weld seam the hold down plates must maintained uniform. Also the plates are too close, the cooling effect be- ronounced, proper comes too prop 7—Setup for hold downs welding T-stiffener. penetration will not obtained. The head, too, will rough and this case the ma- porous. The distance that the plates should set varies with the thickness the material. Recommended dis- tances for butt and the toe welds are given Fig. The hold down strips should not clamped tightly restrict the movement the material being welded. Just enough pressure bring the material against the jig should used; otherwise when the temperature the magnesium raised and ex- pands, the magnesium should al- lowed move under the hold down strips. this not done the mag- nesium will buckle between the hold down and the weld seam; will pull away from the jig plate and burn through under the Also when cools after welding, contracting strains this area will cause buck- ling adjacent sections that will re- quire considerable hand working remove all possible. addi- tion the buckling the material will have fine cracks appear along the line weld where the magnesium has been restricted from contracting. Tension Distortions The same pressure considerations are true holding extrusions and T-welds. Only sufficient pressure hold the extrusion the magnesium sheet should used. too great pressure exerted, when the mag- nesium soft the welding tem- perature, the leg the extru- sion will forced into the mag- nesium sheet, resulting buckling, distortion and unevenness the ex- trusion and flat spots the opposite side the sheet. This shown Fig. and one the hardest types distortion work out. the hold downs are set the proper distance from the weld seam and the tension correct, then the for THE IRON AGE, August FIG.12 FIG. magnesium can expand and move back under the hold down strips plates since there restraining force the plane movement, may result the hold downs Expansion are too loose. The weld the ex- trusion may pull the sheet away from the jig when the weld bead cools and this action can more pronounced corner welds the edge sheet. Fig. the proper tension was the hold down the sheet but the stiffener was not properly held. Pulling away from the jig may also due lack care fitting when setting for welding. Especially contoured surfaces, the web ex- trusion not carefully trimmed and fitted, bear all points evenly along the contour, then when the weld bead made, the sheet which usually smaller cross-section than the stiffener will pull away from the jig and follow the contour the stiffener. Too much emphasis cannot made the importance the proper preparation the parts welded. Fitting, contouring and tack welding are the three main items for consideration. These items. well shrinkage, should kept mind when setting the hold down plates. Typical Jig Structure general conception the com- plexity provisions that must taken avoid distortion during and following the welding operation can gained from Fig. which illus- trates the hold downs, jacks and clamps used weld jig for fuselage structure. The details in- volved the various parts this jig are illustrated Figs. 14. typical method using the hold down plates where T-stiffeners are welded cover sheet shown 36—THE IRON AGE, August 1944 channel bar secured across the jig back the small jacks for holding clamps; clamps are used fasten the T-sec- Fig. tion the jig structure. The jacks and clamps will have shifted clear for welding but should lo- for overall shrinking. The cover sheet trimmed 0.10 in. outside the mold line and the jig structure re. cessed for expansion clearance approximately 0.187 in. After weld. ing, the edge the cover sheet trimmed off flush with the side frame the door. Another expansion gap allowed the top cap the frame, This allows for expansion along the width the frame and another gap LEFT left each end. Trim left Fis. 8—Typical location each end the cover sheet. hold Small jack screws clamp Expansion Gaps the The jig construction Fig. shows method designing for expansion The width the magnesium cover sheet determines the depth the gap ‘Expansion the thickness the amount for medium ABOVE 10—A design door frame design and method jig- member for T-extru- ging. sion. that complete weld bead can laid one time without stopping shift around clamp jack. The weld should also strain re- lieved before the clamps are ever loosened. Fig. illustrates another typical manner which the hold down plates are ‘ocated. These may made full Wi | IN J plates providing they can inserted through the jig struc- ture. Otherwise they may broken into sections. They sized sheets about 0.187 in. This formed the contour the cover sheet. The previous considerations given for clamping pressure hold true. Just enough tension hold the cover sheet down the jig plate suffi- cient, otherwise the cover sheet will and distort the door frame warp the complete door this in- The small jack screws provide convenient method clamping the hold down plates. bar channel fastened across the jig and series jacks used secure the plates place. typical design for welded door frame shown Fig. The edge the frame located 0.040 in. out- side the mold line the door allow will take care 0.10 in. for trim and allow 0.087 in. for expansion which most cases will ample. The width the gap should approxi- mately 0.020 in. larger than the thick- ness the cover sheet, which will allow for movement parallel the surface, The jig construction Fig. similar that Fig. except for the supporting member for the mag- nesium T-extrusion. Here the angle where contour encountered. The joggle may cause some difficulty. such instances the construction Fig. will easier form the width the expansion gap for the door frame. Any amount for sona for stiff ther: sion. ture tha not par bes fitt str als loc cover the ice weld. eet frame gap rame, the gap eft igning sonable clearance the parts will sufficient. The arrangement shown Fig. for locating and holding T-section stiffeners serve the purpose for inter- mittent welds, but for solid welding there should allowance for expan- sion. order keep the jig struc- ture from moving and maintain the proper tension the parts being welded, the jig structure will have clamped place, care being taken that too much clamping pressure does not cause buckling “cans.” The greatest difficulty with this type jig structure the setting the parts and the fitting, and get the best results from the welding, each T-section should trimmed and fitted the welding progresses. Fig. shows typical jig con- struction for holding bar stiffener running across the contoured sheet and located angle with stops. The T-section stiffener held the contour with built-up T-section steel strips formed the contour and also located with stops. typical method holding and locating bar stiffeners and T-sections Fig. 14. The angle used sup- port the stiffeners running normal the curve because the difficulty en- countered rolling angle sections. formed T-section supports cates the stiffeners running with the curve. The stops the angle locate the and bar stiffeners mag- nesium one side only which allows for any creep due heat. More con- sideration must given clamping Pressure with this type construc- tion which less flexible. Use Jig Templates The use jig templates for the construction weld jigs probably the most important point con- sidered. contoured plates where cover sheets are welded, and mono- and nacelle sections where con- tours and tapers predominate setup jig templates essential. The oversize required compensate for shrinkage should incorporated the template. Naturally any adjust- ments for welding should noted thereon after the first assembly has been welded and checked. Another feature the jig template, tooling for small parts subas- semblies, fasten the template suitable base, and mount clips LEFT variant Fig. 10. The supporting member has joggle. and stops, etc., the lines the template. Clamps are also provided for holding pur- poses. This type construc- tion used only where there need provide for backing-up hold downs when the effect shrink- age negligible there are contours. Use Drill Fixtures Attachment holes, clear- ance holes fact any openings other than lighten- ing holes should not drilled until all welding has been completed and the part has been stress relieved. The ex- panding and contracting during weld- ing combined with such hand forming may necessary, will cause the metal creep, and this will cause the holes shift the general direction the greatest movement; hence, all critical holes must left until the last operation. extreme cases, where im- practical use clamps, holes may drilled through the sheets and bolts used hold the parts the jig. Clearance must allowed around the bolts for shifting the material, and the same pressure considerations al- lowed for hold down strips. These holes must plugged and the sur- face finished down before the struc- ture strain relieved any holes drilled for attachment points, etc. Drill fittings may designed removable make the jig more ac- cessible for welding. This not good practice, however, for holes that must line reamed. Holes that are matched some other assembly should permanently attached the jig, but the whole pattern can incorporated one fixture trouble should arise the fixture carefully indexed the jig. LEFT feners for intermit- tent welds. BELOW bar stiffener across contoured sheet. Fig. shown zine drop hammer die reworked into weld jig. This practical method for con- toured surfaces where there are weld seams which require grooves, be- cause the die would not stand un- der the heat the The heavy steel angles along each side are rein- for the attaching the THE IRON AGE, August 1944—37 and the ster. right D) ing > We Sd NK @ > Sy ‘he QD which i will the for mag- angle sheets The ty. the the rea- locating members for the ribs. The skin sheet held the die with the quick acting clamps are also the hold down bars. The skin sheet first trimmed 0.10 in. outside the mold line the part scribed the die. Then lo- the die and the ribs and stiff- eners welded in. Dies make the most economical jig base for doors and removable panels. After the parts have been stamped out, the dies continue used ‘iy fy data which base any changes made the welding sequence, imperative that there written procedure for welding each assembly part. This work should done someone who experienced fab- rication, welding, tool design and tool planning. The procedure should not too brief, nor should bulky with unnecessary details, but com- plete and directly the point. many instances the success the tool depends upon LEFT Method locating bar stiffeners and T-sec- tions curved sur- face. BELOW 1G. ing how drop weld jig part this jig. This saves the large labor cost contouring heavy plates match the dies and lowers the cost making the dies their continued use. The illustration, Fig. 16, shows the door frame place after has been welded. The advantage this type jig that the part can stressed relieved oven. Torch relieving can also used. The weight the die another factor con- sidered when designing the jig. Contoured jigs for fillets should have the plates stamped out the same dies the fillets are made, see Fig. 17. The formers are made and located jig templates. The con- toured plates should fastened the formers flush head screws and not tack welded. This true for all jigs prevents distortion. typical nose section jig for the wing shown Fig. 18. The ribs are located the angles across the jig and the cover sheet held out the contoured plates the clamping fixtures, three which are shown place. The contoured plates are sup- ported each rib station formers. Welding Procedure order save time the job, determine which part welded first and the sequence weld- ing and also have some concrete 38—THE IRON AGE, August 1944 presentation the way the tool function, combined with the proper welding sequence. the procedure too sketchy, the will not develop all its possibilities and the finished product wil rejected. Also, the procedure not fol- lowed strictly, and any deviations are not noted that appear during welding setting up, there noth- ing guide the worker the next assembly fabricated that jig. The need for careful study work- ing out the welding procedure can- not overemphasized, and flected the time saved the shop, labor cost and material cost well uniformity the finished Analysis Structure The first step writing weld procedure study the structure jigged. Note the inaccessible points those most difficult reach for welding and determine their tion the jig, also the method holding. possible these points should made first they should worked time when the welding can performed most con- veniently. they can made subassemblies, may more eco- nomical the long run design separate jig for these difficult loca- tions. Also check for castings fittings and heavy extrusions formed sec- tions. They will require the heaviest amount weld material greatest amount heat. The weld- ing these heavier parts should done early possible the weld- ing sequence and strain relieved that the amount heat and the sulting expansion will plates stringers, etc. Distortion caused welding castings heavy sections will very difficult work out due the lack bility the larger mass metal and its resistance any change posi- tion and shape. Care should also exercised when welding castings formed shapes intricate fragile design. The expansion and contrac- tion details welded them may cause distortion, | < 2 shop, weld loca- hod points should the eco- sign loca- ittings the weld- weld- uckle flexi- and posi- may used base for door frame, shown welded. breaking cracks difficult notice with the eye, especially the casting has been put under strain that just equals the ultimate yield point the metal. many instances will found more convenient break down the structure fabricated into smaller units and then combine them into the completed structure sew-up jig. This satisfactory the shrinkage the jointing weld does not affect the basic dimensions the structure. There are two fundamental reasons for making subassemblies—to facili- tate welding doing the more diffi- cult sections first separate units, and increase the rate production making greater number smaller units reduced amount time. determining whether there will need for unit assembly, must kept mind that the shrinkage must held the last weld order control the total amount shrink- age for the whole structure. Welding Sequence order limit the shrinkage the last weld, starting point for the welding sequence must determined. may start with one edge as- sembly and advance progressively across the opposite edge, may start the center some other and progress both outer edges, may start somewhere the body the structure and grow out all directions the edges the structure. The design determines this and must ascertained from the particular assembly con- structed. definite rule can laid down other than pick out the key point where the work can start and progress uniformly, strain relieving and removing buckling the welding goes along order prevent minimize locked strains and warping and able the final weld with the shrinkage limited this last bead. There will exceptions and prob- lems encountered where this may seem impossible, but the welding procedure revised and kept date these more difficult sections are worked over, eventually after several trials procedure can worked out the shop. All parts for welding should specified oversize lengths for ex- trusions and with edge trim for plates, doublers and sheets. The first part welded can most usually trimmed size start, although better trim each part for each weld. female jigs for contoured sur- faces, the covers are trimmed, fitted, welded and strain relieved first with FIG. 17—Application contoured jigs for fillets. THE IRON AGE, August 1944—39 — trim left ail around until the last weld has been completed. The stiff- eners, frames, etc., are then fitted, trimmed, welded and strain relieved the work progresses. Strain re- lieving should called for after each weld bead has been completed there any indication buckling dis- tortion any time when there possibility that locked-in stress may incorporated the joint. The following typical weld procedure for the access door shown Fig. 19: (1) Place cover sheet (2) jig (jig not shown). (2) Locate stiffener (8) place and clamp. not trim ends. (3) Weld stiffener (8) cover sheet (2). (4) Strain relieve and straighten. (5) Fit and trim stiffeners (12) two places. Leave trim outer ends. (6) Weld stiffeners (2) and (8) starting (8). (7) Strain relieve and straighten. (8) Fit and trim stiffeners (10) two places leaving trim outer ends. (9) Weld stiffeners (10) (2) Safety NEW safety insert for tapping heads developed three em- ployees The Glenn Martin Co., Baltimore, has almost completely eliminated tap breakage where this factor previously ran high six taps per 8-hr. shift threading hard, heat treated steel The first innovation was cutting groove near the top each tap, that the tap did jam, would break this weak point and could removed from the work. But while 40—THE IRON AGE, August 1944 ABOVE Method handling con- shown this typical Req. FIG. 19—Access door for which weld procedure worked out test. and (8) starting (8). (10) Fit and trim frame (6) two places. Leave trim each end. (11) Weld frames (6) (2), (10) and (12). (12) Strain relieve and straighten. (13) Trim ends (6) and (8). Fit and trim end frames (4) each end door. (14) Weld and frame