The Iron Age 1938-11-17: Vol 142 Iss 20

FRITZ FRANK President VAN DEVENTER Editor Cc. E. WRIGHT J. A. ROWAN A. 1. FINDLEY Managing Editor News Editor Editor Emeritus Machinery Editor Art Editor Metallurgical Editor Associate Editors JURASCHEK Consulting Editor Washington Editor Resident District Editors Pittsburgh Chicago Cleveland Detroit Correspondents London, England FRAZAR Hamburg, Milwaukee San Francisco SANDERSON ASA JR. Toronto, Ontario Birmingham Newerk, N. J. Louis TURNER, JR. Buffalo NOVEMBER 1938 and Published New Day Dawns CHILTON COMPANY (Incorporated) Rolling Along Industrial Conveyors Editorial and Publication Office Executive Offices Creep Metals Under Stresses Chestnut and Sts., 239 West 39th St., Philadelphia, New York, ircraft Evolution and Press Progress OFFICERS AND DIRECTORS FRITZ Executive Vice-President Further Advances Welding FREDERIC STEVENS, JOSEPH HILDRETH, Cutting Tool Action Studied Motion Pictures GEORGE GRIFFITHS, MOFFETT, Secretary JOHN VAN DEVENTER, JULIAN CHASE, CARROLL BUZBY, FAHRENDORF Weekly Ingot Operating Rate Member, Bureau Circulations Plant Expansion and Equipment 96, Member, Business Papers Indexed the Industrial Arts Index. : ) Published every Thursday. Subscrip- tion United States and Pos- sessions. Mexico, Cuba, $6.00; Can- ada, Foreign, $12.00 year. Single copy, cents. Cable Address, ADVERTISING STAFF Emerson Findley, 621 Union Bidg., Cleveland 113 B. Bidg., Chestnut & 56th Phi adelphia, Pa. Hottenstein, 802 Otis Bidg., Chicago H. E. Leonard, 239 W. 39th St., New York Peirce Lewis, 7310 Weoedward Ave., Detroit C. H. Ober, 2239 W. 38th St., New York D. C. Warren, P. O. Box 81, Hartford, Conn, Copquighe 7 ig | | q ) Li Gurzon national me- morial Mt. Rushmore and Allegheny Ludlum fine steels are both examples that Counts.” For outstand- ing craftsmanship requires long range planning, infinite patience, and expert control every operation. Allegheny Ludlum fine steels are developed step step under exacting laboratory control. They are the prod- uct never-ending research meet industry’s demand for increased pro- duction and lower unit costs. you have any design operating problem that involves fine steels, A-L engineers and metallurgists are your service. Inquiry places you under obligation. Write Allegheny Ludlum Steel Corporation, Oliver Building, Pittsburgh, Pa. 26—THE IRON AGE, November 1938 ALLEGHEN STEEL CORPORATION tH A-L STEEL 137% BETTER fine steel made and recommended Allegheny Ludlum was tested Mid-Western plant compe- tition with other steels. The test involved turning old car axles, diameter, about .45 carbon. Speed was surface feet per minute; cutting depth feed One competing steel cut only before failure; another, The A-L steel cut 137% better than the nearest competitor. Moreover, upon re-hardening, the A-L steel repeated its remarkable performance. LUDLUM PITTSBURGH, PA. owe AY | | NOVEMBER 17, 1938 ESTABLISHED 1855 Vol. 142, No. 5 New Day Dawns FTER the past two Presidential elections and the intervening State elections, heard good deal about mandate. That was new word the lexicon American politics. § any mandate from the people was conveyed these elections, was put million unemployed back work private industry. tet was not mandate from the electorate put these people Government pay- roll, except temporary relief from distress. Certainly not build political relief machine. was not mandate redesign the Constitution, not make Democracy safe for the sit-downers, not cripple private employment abuse and persecution industry and business. How well the New Deal Administration carried out tried carry out its real and imagined mandates matter record that need not touched upon. Suffice say that after six years white rabbit pulling, the unemployed America totaled million, instead 10. Last week another mandate, command, was given the Administration. was overwhelming mandate fish cut bait. unmistakable order forget the imaginary mandates concocted the trust and concentrate the original job getting the unemployed back private industry, where they belong. else! 4 From now on, the path the employer who anxious see his business grow and have employment grow with will smoother. For Democratic Senator Tydings said his election night victory address: task Government must now help business and not put unnecessary obstacles its 4 People who have had money invest and who have been afraid put work for fear confiscation can now banish that fear. There will dictatorship America. That possibility went out the window with the failure the There will more sit-down strikes condoned Government. That possibility went out the win- dow with Governor Murphy. Most encouraging all the results the election the demonstration the sound- ness and sanity the American electorate. cannot seduced unlimited slush funds from the public pork barrel, distracted white rabbits regimented well oiled po- litical machines. November marked the dawn new day confidence and common sense. ae “a q q 7 J | : 3 | 4 5 ) + Character and Machine Performance very long ago all the parts made screw machines specified “Screw and because cut better, Besse- mer screw stock was supplied. More severe service requirements, inability achieve uniform heat treated hard- ness, and certain lack mechanical dependability forced the production free machining steel made the open hearth practice. Immediately engineers were faced with choice— when use Bessemer and when use open hearth. This question has become increasingly important service re- quirements became more severe and more especially production costs en- tered prominently into the manufactur- ing picture. Everybody knew was cheaper use Bessemer, but they knew that for certain parts Bessemer didn’t give good service. The steel which showed fewer field failures and was more dependable caused produc- tion costs rise. Why didn’t someone produce dependable steel which would cut easily and hold costs down? The choice the proper type material use has rested upon the fact that Bessemer screw stocks have always been superior machining quality and inferior heat treating possibilities and physical character those screw stocks made the open hearth process. This has meant that the selection screw stock for cer- LEAD DISTRIBUTION HOT TOP INGOT FIG. 28—THE IRON AGE, November 17, 1938 OPEN TOP INGOT tain part has been dependent upon ser- vice requirements; Bessemer being selected machinability was prime importance and the part was not heat treated subjected severe shock. were heat treated and service conditions were severe, open hearth screw stock was specified and sacrifice machinability with consequent comparative production cost was absorbed. Naturally, avoid this increased cost, efforts were made improve the cutting properties open hearth steels and the same time preserve the highest possible degree their qualities. First methods embraced mere duplication Bessemer analyses usually effected rephosphorization process. This method did not effect the expected in- crease machinability and resulted loss the properties considered most valuable open hearth steels. One the possible reasons why open hearth steel, the analyses which was duplication Bessemer, did not prove satisfactory, was because the differences nitrogen content. effort was made pro- duce open hearth product with nitrogen content comparable Bessemer steel. Research and develop- ment are being carried which will eventually show the merits the idea. Effort has been made increase the sulphur content about one-fourth per cent and claimed improvements nace melting and pour- ing practices offset the effect this high sulphur. Comparative tests the tensile and impact show definitely loss characteristics and ductility which limits the universality application. Efforts increase the phosphorus content these steels also met with disapproval cause even greater sacrifice was noted the result rephosphorization than with resulphurization. Accordingly, rephosphorized steels without the sul- phur content have suffered the same fate and largely for the same reasons. Deoxidation practice, rolling prac- tice, rolling and finishing temperatures all play very important part fos- tering what known good machin- ability steel and have been given considerable attention designed set standard practices which will give maximum machine rating. Cold fin- ishing operations can controlled considerable extent aid further improvement heavy rolling and heavy drafting the drawing opera- tions. Improvement from these means has not been sufficient warrant the added expense entailed and mills not find possible always perform this added cold work. the same time, the results obtained limited warrant consideration any but relatively isolated cases. None these are such nature permit production product universal application for all operations. Besides this, such control production and special processing are expensive and requirements, all which bring economic element into the problem. Research efforts have been directed along the line metallic addition which would effect good cutting char- COLD DRAWN PHYSICAL PROPERTIES SIZE CHARPY FIG. 18.5% 7 Lead Bearing Steels acter and not result loss me- chanical dependability any condi- tion; one which would permit excel- lent response heat treatment (and the production which would permit relatively standard practices which would result steel reasonably uni- versal application). For several years the cutting properties certain non-ferrous alloys have been improved additions small percentages lead. nearly possible the lead fulfilled the requirements above and still were not prohibitive from cost standpoint. came the idea lead additions open hearth steels. The whole purpose such additions, course, has been the improvement machining quality with little possible sacrifice physical character. number mechanical difficulties were encountered making the addi- insure its uniform distribution through the mass the steel. This due the fact that lead not soluble molten steel, and that the two materials are not miscible. the special proc- ess which has been developed, emul- sion the lead the molten steel formed, which solidification leaves the lead very finely divided state, uniformly dispersed throughout the ingot. The size the particles lead CORE PHYSICAL CARBURIZED POT SIZE fine sub-microscopic and ef- forts determine the size X-ray have failed because the small amounts present. About per cent necessary for the bands indicate particle size and only about this amount present these steels. evidence more than nominal segre- gation has been found due, principally, the method which the additions are made. Laboratories are severely handicapped their attack upon the metallographic characteristics the lead that the particles are fine. The nature the occurrence the lead such that even with the most powerful microscopes high magnifi- cation not possible resolve any structure the lead particles. the same time difficulty has been experi- enced finding satisfactory etchant definitely show the presence lead. date the most satisfactory metal- lographic etchant found for this pur- pose aged solution sodium picrate which small amount sodium sulphide has been added. There considerable diversity opinion the interpretation samples etched this means, that this etchant seems indicate the presence lead but not the exact location distribution. X-ray examinations and tests elec- trical properties has been definitely shown that the lead does not form solid solution with iron and there is, therefore, alloying effect the two. Mea- ger results metal- lographic examinations have provided relative- little the way information data ex- cept prove definitely that the lead there and that very fine- divided and sub- microscopic size. the lead upon the Mc- Quaid Ehn grain size that has tendency make this grain size somewhat finer than that the base heat the material which has heen added. far ° ° ° FREDERIC ROBBINS Bliss Laughlin, this has not appeared detri- mental any way regards ma- chinability heat treatment this material except that reacts way expected for steel embracing the particular grain size found. Beyond this the lead appears have effect metallographically. Fig. shows results actual chemi- cal checks made upon several halved ous spots indicate the uniformity lead distribution. Figure indicates that there little tendency the part the lead segregate any spot, re- gardless the type ingots used— hot top open top—and indicates relatively throughout the mass the ingot which course carried over into the bar rolled from that ingot. This effect mentioned before due prin- cipally the method which the lead added and is, course, feature prime importance makes for uni- form machinability and for mini- mized effect upon physical character that steel. are the physical properties these materials the unheat-treated and heat-treated conditions. necessary discuss these some detail because this point considerable impor- tance fulfilling one the original S.A.E. CORE PHY SICAL PROPERTIES CARBURIZED YS. COOLEDIN POT REHEAT WATER QUENCH SIZE ROUND R.A. CHARPY FIG. THE IRON AGE, November 17, ingots SAE 1115 plus lead vari- > FIG. COLD DRAWN PHYSICAL PROPERTIES SIZE ROUND QUENCH requirements set for this type material; namely, the production free-machining, open hearth steel with- out loss physical properties and mechanical dependability. close study the effect lead physical properties has been possible because the fact that both lead bear- ing and non-leaded specimens could obtained from the same heat steel. Bars for this purpose were rolled from adjacent ingots, lead addition having been made one and not the other. This practice which has been used the preparation test data gives the benefit standard base material, the only major variable between the prod- ucts the companion ingots being the lead. Fig. shows the cold drawn physical properties SAE 1115 versus 1115 plus lead. noted that the tensile and yield strengths compare very favorably with slight edge the leaded steel. This edge, however, 4000 lb. tensile and 3000 Ib. yield, slight within testing toler- ances. The elongation and reduction 30—THE IRON AGE, November 17, WATER QUENCH area are identical; Brinell hardness leaded steel 143 compared with 137 the non-lead bearing steel, cold drawn, while the Charpy impact slightly higher for the SAE 1115. Here again these impact values are close cause the differences assigned testing variance. Fig. shows the physical properties the same size bar and same analysis material when carburized for eight hours and quenched directly from the pot into oil. Note again how closely the two compare: 2000 difference tensile, 4000 Ib. yield, per cent elongation favor the lead, per cent reduction area favor the leaded steels. Brinell slightly soft- er, and Charpy slightly lower for the leaded steels. Fig. shows the same steel car- burized for eight hours, cooled the same pot, reheated 1425 deg. Fahr. and quenched water. Here tensile there 6000 favor the stand- ard SAE 1115, 10,000 yield favor standard SAE 1115, per 1045 WATER QUENCH cent elongation favor leaded steel, per cent reduction area favor leaded steel, points lower Brinell and identical Charpy values. Fig. shows the comparative cold drawn physical properties SAE 1015 and the same analysis plus lead in. round. Physical proper- ties are almost identical throughout. Fig. shows the comparative physi- cal properties SAE 1045 and 1045 plus lead, companion ingots, rolled the same time under identical prac- tices. Heat treatment simple quench into oil and draw both per- formed samples same time. Here again note how closely the physical properties compare. Fig. shows the same steels Fig. except that they have been quenched water. Again find the close com- parative values physical properties. Fig. shows the comparative im- pact values the steels referred Figs. and water quenched and oil both tempered 1000 deg. Fahr. Fig. shows the comparative physi- IMPACT STRENGTH QUENCH TEMPER er CHARPY g00° 1000° 1200°¢ ° SAE. WATER QUENGH TEMPER ENDURANCE LIMIT SIZE- DIA. CHARPY cal properties SAE X-1335 and X-1335 plus lead. again note that the differences physical character are slight within testing variations. Figs. and show fatigue values for the leaded 1045 and SAE 1045. The endurance limit the same for both steels. The only significant dif- ference the fact that the leaded steel curve approaches the axis less rapidly, indicating its ability withstand stresses excess its endurance limit for greater number cycles. The conclusion reached from con- sideration the test data which have been presented, together with that from other similar tests, that the addition lead any the standard SAE plain carbon open hearth screw stocks steel grades re- sults significant change their physical character. Those differences which have been brought out the tests are felt attributable ex- perimental error the result nor- mal variations chemical and metal- lurgical characteristics ENDURANCE LIMIT QUENCHED TEMPERED same heat steel. Even though consider these slight variations due solely the presence lead fact which has not been conclusively dem- onstrated), the effects are actually engineering design material specification. connection with the heat treat- ment these lead bearing steels, field service reports indicate that occasion- ally their ability case carburize seems slightly retarded. This, believed, due the fact that the lead causes modifications the char- acteristics determined the McQuaid- Ehn grain size test, mentioned above. This, however, can safely compensated for slight variations temperature carburizing with danger the part. connection with the steels higher carbon content which are simply quenched and drawn, the lead- steel shows tendency form slightly more adherent scale than those like analyses containing lead. Tests have shown that general QUENCHED AND TEMPERED 76000 this can overcome the control furnace atmosphere which rela- tively simple matter the gas fired furnace. has also been found that electric furnace artificial at- mosphere produced the presence small amount carbon tetrachloride coke satisfactorily removes this scale retards its formation and eliminates loss hardness which would result heavy scale were left adhering the piece when quenched. Beyond this, laboratory experiments and production experience have shown significant differences the vari- ous processes heat treatment neces- sary produce comparable results lead bearing and non-lead material. regards the hardenability, Fig. shows comparison the hard- ness penetration 1045 leaded and non-leaded bars from companion in- gots, water quenched and drawn 300 deg. Fahr. The hardness readings were taken in. apart and indicate very close correlation between the two. The same found the com- HARDNESS PENETRATION b WATER QUENCH 300°F TEMPER SIZE ROUND THE IRON AGE, November 72000 64000 quenched and tempered 1000 deg. Fahr., shown Fig. 13. critical examination these fig- ures will indicate that lead bearing steels are slightly more shallow hard- ening than non-lead bearing. Such slight variations can usually com- pensated for nominal modifications chemistry heat treating practices. recapitulation the information shown here along with the many other tests whose results are identical closely comparable those shown, seem sufficient evidence that car- bon screw stock steels containing about per cent lead added present standard SAE analyses can handled almost the same production procedures are true for those same grades not containing lead and that result heat treatment physical properties and mechanical dependabil- ity the same order can antici- pated. This means that the addition lead open hearth steels has fulfilled one the original conditions which were enumerated the outset for free- machining material embrace, name- the retention good physical char- Now, briefly, let inquire into the ability leaded steels meet the ‘other requirements set up, namely, its comparative machinability. The choice evidence illustrating the relative machinabilities mate- rials always difficult one make. many variables have direct in- direct effect upon the production pro- cedures, speeds and feeds that impossibility quote figures which will applicable for the same part any set other than the one directly 32—THE IRON AGE, November 1938 involved. One shop can run certain steel much higher rate produc- tion than another and yet produce ex- cellent results. The old argument heavy feeds and slow speeds versus light feeds and higher speeds; equip- ment available, its age and condition repair; operating skill and hundred others materially complicate the whole problem. The following illustrations sults production tests run manu- facturing plants screw machine job- bing houses where especial features WATER QUENCH TEMPER SIZE ROUND SURFACE FEET were incorporated into the tests. Every effort was made prevent any injec- tion prejudice which might influ- ence the results any way. Identical production procedures were employed each individual comparative test. true that procedures used other shops might have resulted different figures and consequently either greater less savings part cost. not felt that this invalidates the test, re- gards the production the part in- volved, particularly, since the noted savings actually appeared the job cost sheet. Fig. shows the comparative pro- duction base hub made from SAE X-1112, high sulphur Bessemer screw stock, originally 168 ft. per min., net production parts per hr. and total cost per part $0.059. Com- pare this the same part run the same machine using heavier feeds and higher speeds surface speed 256 ft. per min., net production parts per hr. and total cost $0.046 per part, saving part cost per cent. Fig. shows bushing used the automotive field which formerly was made SAE X-1314 128 ft. PARTS/HOUR per net production 156 parts per hr. cost per part $0.028. Against this let compare the same part made from 1115 plus lead, the same machine using speed 236 ft. per min., net production 288 parts per hr., total cost part $0.023. This represents saving per cent. Another typical part spur gear used washing machine, formerly made X-1335 134 ft. per min., giving production 150 parts per BASE HUB COST PART Against this lead-bearing X-1335 steel was run 187 ft. per min., giv- ing net production 214 parts per hr., and total cost $0.029, showing saving 6.4 per cent the cost this part. This shown Fig. 16. All three these parts were run sufficiently large quantities show very definite increase tool life well make certain that the ma- chines would continue run pro- duction basis this rate. Tool life in- dications have been sufficient war- rant assumption that tool expenses will show decided decrease the operations necessary high production parts this type. Certain jobs have shown increases tool life great 200 per cent. Others, course, have not shown nearly this much increase but have been large enough considered significant factor the reduction general tool expense for any job. should mentioned here that number instances has been found advantageous from the stand- point tool life and part finish make some small adjustments clearances and rake angles grinding tools when running leaded steels. This HARDNESS PENETRATION MACHINE has definite enough gen- eral enough permit the presentation data. Usually the machine oper- ator can “feel his way” the most satisfactory machine set any given job. Innumerable examples could cited other jobs which leaded steels (plain carbon open hearth, open hearth screw stock and Bessemer grades) have been substituted for variety standard grades and all which they have shown definite improve- ment part character, tool life, and MACHINE FIG. FEET have increased production effect considerable saving part cost. Explanations, metallurgically, for this effect upon speeds and feeds and tool life, date are more less theoretical. The assumption that these improvements are due two functions the lead; one being that form serves effectively break the continuity free-ferrite man- ner similar that performed man- ganese sulphide but much more ef- much finer particles and more uni- formly throughout the mass, and, the same time, exhibits considerably less tendency towards segregation. The resulting discontinuity motes machinability producing fine and well broken chip which building around the cut- ting edge the tool. Frictional heat is, course, minimized which results tool life. even greater consideration the possibility higher speeds and heavier feeds made possible this fact. Nor should the improvement part finish over- looked, The uniformity distribution lead particles and their extremely PARTS HOUR small size possible explanation the fact that lead much more powerful than manganese sulphide promoting machinability. the same time these characteristics may explanation its not affecting the physical properties the steel which added. The effect upon the tools further explained the well known lubricating effect lead component part various bearing materials giving the effect lubrica- tion bearing action the tool passes through the steel. Further BUSHING COST/ PART tests progress present may add subtract from these ideas. While lead additions were first made open hearth screw stocks and plain carbon steel grades with the view developing without sacrifice the physical prop- erties characteristic open hearth steels, the fact was not overlooked that comparable improvement the ma- chinability Bessemer steels alloy steels was highly desirable. There large volume automatic screw machine parts being made, for which the physical characteristics Bessemer steels are entirely adequate. Many these parts are intricate design and involve extensive machine operations their fabrication. meet the demands the fabricator this class parts for increased pro- duction and decreased finished part cost, leaded Bessemer steels are avail- able with machinability ratings hereto- fore not approached any free cut- ting steel. The analyses the base material these steels, which the lead has been added the same amounts the open hearth steels noted above, con- form the standard for SAE 1112 and X-1112. Laboratory experiments PARTS/HOUR have indicated that these materials ex- hibit the same general physical and metallurgical characteristics com- parable analyses without lead, and that from this standpoint they specified for any parts formerly made these grades without the lead. The improvement machinability the same general order has been previously noted for the leaded open hearth steels. realize fully the potential machinability provided these lead bearing Bessemer steels, necessary, course, that adequate MACHINE RATES-COSTS SPUR GEAR FIG. COST/PART machine equipment available, which will permit sustained operation with high spindle speeds and heavy feeds. The development leaded alloy steels with lead content such has been used the grades previously dis- cussed, still the experimental stage. While several different grades leaded alloy steel have been pro- duced, sufficient test data are not yet available permit final judgment the merits and possible shortcom- ings which these steels may have. not the intention the writer indicate any way that lead bear- ing steels represent panacea for all machining troubles nor suggest that they will replace entirely those grades which have effectively served great purpose the industry. The writer does believe, however, that steels with lead are attaining definite place material specifications with those now standard. great service they could made perform the elimination the many slight and usually unimportant variations from standard analyses for so-called “special jobs” and “special results,” the promo- tion which has resulted great dif- ficulty for both steel producer and fabricator. THE IRON AGE, November 2 3 } 7 7 7 7 ABOVE conveyor installa- tion large strip steel mill, feeding battery continuous pickling units. LEFT installation, delivering coil automatically the unrolling mechanism just ahead the pickling operation. BELOW 3—Logan handling equip- ment the discharge end the four pickling units same steel mill Figs. and Economics Materials Handling Methods and Equipment terials handling seem complex that few these prob- appear have anything all common with others. But simple inalysis shows that two facts cover practically all the real essentials any situation. These facts are the characteristics the load and the other words (and this not intended joke) the subject materials handling consists merely consid- eration the materials handled, and the handling those materials. But all the possible variations these two factors (which seem the surface include innumerable compli- cations and variations) may re- duced just five physical character- far any materials han- dling problem concerned, all the essential qualities the load may expressed terms weight, shape and size; and all the essential qualities the movement may expressed terms direction and speed. Once this idea grasped, the ap- parent complexities the subject re- themselves elementary princi- ples, and longer necessary think ore-handling one problem and the automotive assembly line an- first glance the problems ma- Rolling Along Industrial Conveyors ° FRANCIS JURASCHEK Consulting Editor, The Iron Age other, regard package handling es- sentially different from the progressive machining engine block, the transfer miscellaneous cargo from ship rail marine terminal totally unlike the process convert- ing slabs steel into coils rolled strip. Each and every materials han- dling problem may converted, for the purposes engineering and eco- nomic analyses, the five physical factors weight, shape and size load, and the direction and speed the movement. And, reducing the elements the problem com- parable data, the solution more than likely suggest itself without further ado. Subject, course, the special conditions each problem, may said general that when the move- ment intermittent character the equipment called for apt some form wheeled, mobile truck, some form crane and hoist com- bination; while, when the movement regular and constant, over the same path, the equipment called for apt some form conveyor. Industrial Conveyors certain cases the weight and size the load are complementary; ma- terial generally heavy because big. Now, the shape such that flat surface presented the ma- terial its container, sufficient size make effective contact with two more rollers simultaneously. ° lugical means handling apt the roller type conveyor. the other hand, small, irregularly shaped loose materials probably indicate the use the belt conveyor, some one its variants, the apron, bucket. drag-link conveyor. Or, the ma- contained box, crate, barrel drum, and over the same path regular, continuous flow, the equipment may either the roller the belt conveyor, other condi- tions may indicate. Again, the material consists products parts which may readily suspended from hook sling, any size shape which may readily suspended from hook sling, overhead conveyor may the ideal solution either the unit trolley type. the continuous chain type. says “Natural Laws Applied Production,” that every materials handling device must adapted the load characteristics the material handled, the reduction these characteristics the physical factors weight, size and shape shows that they are essentially few number, relatively simple type, and easily met. The really essential factor materials handling system move- ment, its two elements direction and speed. the materials handling system whatsoever type may considered, these two elements are the THE IRON AGE, November > | | 7 ° ° ° ‘ | | | | | = two essential phases the principle continuous flow—the principle which has probably done more make modern production methods efficient and economical than any other idea industrial management. Continuous Flow has been said that efficiency and economy both are gained materials handling when load moved mere muscle that can moved me- chanically. But more than that re- 36—THE IRON AGE, November 1938 quired for true efficiency and true economy. Only when the handling planned that rehandling eliminat- ed, that retrograde movements are done away with, and that the goods movement becomes one, forward-pro- gressing line from the beginning the end the work, may the ultimate ideal attained. And this ideal summed the principle “contin- uous flow,” which the conveyor, all materials handling devices, best adapted. ° Standard ment handling coils into storage another strip mill. This thought may readily grasped when considered that the output any piece processing equipment, matter how efficient may itself, cannot exceed the amount material which fed into any given period, and taken away from after the processing work done. therefore the utmost importance provide constant flow material into such equipment, and likewise provide means for swift, positive re- moval the discharge end order prevent production hold-up. Any machine process that idle sixty during working day loses exactly hour’s productivity. example, consider the modern strip steel mill, where may readily found the continuous strip pickling operation. Equipment Illustrated Fig. shows such condition. Four continuous pickling units, the back- ground, must kept supplied con- stantly with fresh coils strip steel, these expensive units are worked full capacity. this particular mill, Logan Co. conveying dling equipment accomplishes this de- sirable condition. Overhead crane ser- vice delivers supply coils the 5—The new Mathews re- silient suspension gravity roller conveyor, handling flasks large foundry. on | Continu- ous flow trans- former disks through battery Gehn- rich flash enameling ovens electri- manufacturing plant. heavy-duty roller conveyors foreground, which are ciently cause the coils travel gravity the down-tilters. down-tilter delivers single coil trough-section roller conveyor, which turn discharges the coil side- tilter unit. The side-tilter delivers the coil, needed, the coil box the uncoiling machine the head end the pickling unit. Fig. shows coil which has just been delivered the coil box one the side-tilters. the discharge end the pickling units the recoiled strip rolls onto V-shaped pedestal mounted scale platform, tied, weighed, weight recorded. Each coil discharged onto heavy-duty apron conveyor leading skid table, shown Fig. these skid tables the finished coils are transferred trucks storage the shipping series operations, first, that the terial fed into the pickling units 7—Almost ready drive away. automo- tive assembly line conveyor near- ing the end its journey. just fast those units can take it; second, that there can delay here, for each coil unrolled, another coil poised readiness the side- tilter immediately front the coil box; third, that adequate storage, loading line facilities precede the above operations; and fourth, that the han- dling operations are entirely automatic, both the pickling unit intake points and the discharge points. Thus the speed handling becomes function the speed operation the pickling units, and the pickling opera- tion does not have wait the possible vagaries intermittently operating materials handling system. THE IRON AGE, November j veyor Co. trough-shaped gravity roller conveyors another strip mill are shown leading from similar pickling units into coil storage room. Note particularly, here, the middle line conveyor, which coils traveling either side line are trans- ferred means kick-over mech anism, controlled the operator pic- tured. this mill considered advisable transfer the coils their sides the storage room, but when stacked storage best have them stand end. Consequently the middle line conveyor leads mechanism, which table the background, from which the coils are picked and stacked overhead crane. Fig. new type spring- suspended gravity roll conveyor, built Mathews Conveyer Co., used large foundry handle heavy flasks. Normally, the delivery heavy flasks overhead crane roller conveyor produces shock load great severity the roller bearings. The resilient mountings this new type con- veyor take such shock loads without bearing damage. Each 8000 Ib. load. Such conveyor lines are pitched toward the discharge end that the flasks travel 38—THE AGE, November 1938 and the conveyor lines serve means storing empty flasks until needed. Other Conveyor Types Fig. illustrates type con- veyor which carries material directly through the processing equipment. Two Gehnrich flash enameling ovens, heated external oil heating sys- tem located between the ovens, are used large electrical manufactur- ing plant for treating transformer core plates 660 deg. The process continuous one, and requires the ma- terial moved through the ovens constant rate speed. The thin plates are placed hand in- verted, U-slat, which rides track angles for total dis- tance ft. The conveyor ft. in. wide. the discharge end the work falls off the conveyor into re- ceiving bins, and the conveyor returns the bottom the oven the load- ing position. The continuous flow principle has been brought high state velopment the automotive industry. Fig. shown automotive as- sembly line conveyor made Palmer-Bee Co. for leading car man- this conveyor, the drag-chain type, entire cars are carried definite intervals, cradles; the movement the whole line progress- ing such rate speed that stations workmen particular assembly jobs. excellent detail view such conveyor shown Fig. 8—also Palmer-Bee installation. continuously moving chain shown riding its regularly spaced trolley wheels, which turn carry apron plates size adequate hold vari- ous-sized loads boxes, crates, pal- let-loads material, miscellaneous loads material directly. all the foregoing examples, the principles continuous flow are ex- emplified. Likewise, the type load varies from coils strip metal foundry flasks, light, thin metal Close-up typical ous chain package conveyor, similar general principle the automotive as- sembly line conveyor. disks, automobiles, miscellaneous packages. Fundamentally, regardless the characteristics the load any case, the problem ma- terials are moved forward, con tinuously, rate speed accommo- dated the needs the situation. materials handling problems are not simple, course. When they are, likely that some form indus trial conveyor will provide the best however, that conveyor problems are When the conditions faced preclude the possibility statement the situation similar simple terms, other equipment than conveyors must almost invariably considered. { j | | i Creep Metals Under Static and Repeated Stresses LEA* Professor, University, England demand upon metals work increasingly higher temperatures during the last years has made necessary change the point view from which the suitability particular metal for particular purpose shall judged. Before the great war good deal work had been done the effect temperature the properties metals judged from what were thought the fundamental proper- ties metals, namely, the maximum stress required break specimen without reference time fracture, the so-called elastic limit and the yield point. When the author began experiments years ago the effect tempera- ture the properties metals, soon became clear that when certain temperatures were reached, none the so-called fundamental properties were independent the time taken loading and also that constant stress, whether direct lecture before Midland Metal- Societies, Sept. 22. studies cover months time and require extreme accuracy and observation. This machine the Westinghouse Electric Mfg. Co. laboratories one the most elaborate its kind—photo-electric tube maintains inside temperature deg. 1000 deg. F.; each weight below stresses specimen through lever arrangement; and the microscope the circular trach permits measurement elongation any particular specimen. stress, strain might continue, and certain stresses, much less than the so-called breaking stress obtained loading the specimen comparatively quickly, fracture might eventually Further, paper published 1917 the Proceedings the Royal Society, the author and Guest showed that even ordinary temperatures and stresses far be- low the elastic limit, small increases strain might occur constant stress. soon became evident that “creep” was great importance, but unfortunately the war work and, for some time after, other research pre- vented the phenomenon being investi- gated. Experiments the effect high temperature aluminum alloys, coiled springs for and valve seats for airplane engines all showed that the relationship stress and strain could not determined with- out consideration what may called the time element, time func- tion that term preferred. Preliminary experiments quickly dicated that the investigation the phenomenon creep would require years research and the devotion preliminary, experiments were carried out number metals ordinary temperatures. Taking, for example. specimen mild steel, the funda- mental properties which are known, the creep the neighborhood the yield point was investigated and was shown that when THE IRON AGE, November 1938—39 creasing strain creep might con- tinue for some hours; however, seemed quite certain that the creep eventually ceased. yield point, but well below the break- ing stress, creep would continue for long periods but would eventually cease. For instance, mild steel con- taining 0.14 per cent carbon, heat treated 1517 deg. crept 31,360 per sq. in., first irregularly and then very slowly but steadily for al- most four hours. the stress was raised, creep took place for several hours 33,600 35,840 and in. the specimen crept until finally broke little over five hours, the total time loading after yield being hr. Another specimen, 1634 deg. was loaded gradually 59,136 Ib. per sq. in., and the load was kept constant for fourteen days. Dur- ing the last four days movement capable measuring extensions much less than 10° in. With sample stainless steel containing per cent chromium and per cent nickel, small creep took place 13,440 lb. per sq. in., but after hr. creep could detected. 22,400 per sq. in., creep apparently ceased after hr., creep being observable after further hr. 31,360 per sq. in., comparatively rapid tinued per 106 hr., and had probably just ceased. 89,600 per sq. in., after 672 hr. creep could not ob- served, but 98,560 Ib. per sq. in., the specimen broke ten broken quickly specimen would not break less than 123,200 Ib. per sq. Preliminary experiments temperatures showed that very long times would required determine the stress which rate creep would become small that could not observed, and also soon be- came apparent that sensitive strain measuring devices were neces- sary and that control temperature the test was the greatest impor- tance. For example, will seen later that reference will made creep strains per hour less than Suppose specimen in. long tested and the rate creep 10° elongation say hr. will only 0.00001 per in. Suppose now that the temperature the test changes in. per in. per hr., 40—THE IRON AGE, November 1938 3.6 deg. the specimen will 0.000028 in., other words much greater than then the change length the change due creep. appears therefore that changes temperature during the test must controlled within very narrow limits, com- paratively long periods time must taken. one degree centigrade (1.8 deg. F.) change temperature occurs, then for creep strain observed with any confidence, the time observation greater than hr. when greater than 0.000014, greater than hr. Torsion Testing Easier Again, will clear that specimen tested tension and creep occurs, the specimen changes diam- eter, and the load kept constant, the stress changes. This not seri ous difficulty when creep small, but can got over the test torsion instead tension and, will seen later, torsion testing the whole much easier than tension testing, and hollow specimens are used the stress variation can kept fairly small. For standard testing, the author inclined the view that the torsion test has many advantages. There are two important points noted about creep tests such are being described. The first is—what the total strain produced given time, and secondly, what the final rate creep, the final rate creep less than some specified rate? the case material for boiler tubes, the increase diameter per 10,000 in., and the final rate creep was less than in. per in. per this rate creep remained constant, the boiler could work 100,000 hr., that about years’ continuous work, with- out the tube increasing diameter another hundredth inch. inch diameter the tube was The creep was comparatively large first loading, and pertinent ask, the reason for diminu- tion the rate creep?” The answer appears that strain work- hardens the material. The next ques- tion which arises “Will the pro- longed heating produce changes the metal that will allow the rate creep increase again, and such will lead failure?” That changes the properties steels take place prolonged heating temperatures which modern steam plants work now well known. Spher- oidization the pearlite carbon Roberts, takes place and this leads author has shown number pub- lished papers, changes take place certain alloy steels which lead em- brittlement and the very consider- able lowering the impact value obtained from the Izod test. Experi- ence shows, however, that provided stresses and temperatures are kept be- low certain values, creeps are small that they are not observable tice and not lead failure. Pipe Flanges Tested From what has been said will appear that the ordinary method ‘of defining the breaking stress ma- terial and using some function this designing parts structures machines work high temperatures cannot satisfactory, and becomes necessary define what may called ing creep rate” particular stress, and also the maximum possible strain the assumed life the plant. Be- low certain temperatures, the limiting creep stress, the stress below which creep ceases has, the author believes, real meaning but above certain tem- peratures seems possible that creep will continued even small stresses. The Institution Mechanical Engi- neers (English) has, during the last three years, been carrying searches the National Physical Laboratory pipe flanges for high pressure steam plants. the design such joints number problems arise, but the one which interest centered that the possible creep the materials under temperature and stress. The second report gives interesting particulars’ the creep flange bolts temperature 975 deg. F., and under pressure 1400 Ib. per sq. in. Failure occurred after days. The full consideration the strains that occur flange joint when under tightened bolts and heated for long periods during which creep can take place, while interest impor- tance, means easy. some The tightness the joint depends upon sufficient pressure being retained the joint face. When the nuts are tightened, the bolts and other parts the joint are elastically strained. During the heating the joint, these strains will modified and some creep will take place. The bolts and other parts the flange creep that 7 7 q 7 7 7 | 2 j | q | | | | | | j | | | | | | | the elastic extensions are diminishing. When the permanent distortions certain amount, the joint fails. changing the design, hoped increase the life the joint. From the data that has been presented, clear that when creep under stress and temperature occurs, very large proportion the total place the early stages. Thus, well known, the joint tightened after period service. seems very desirable subject the bolts initial heating under stress that large initial creep shall eliminated before the bolts are stressed the pressure the pipe. Periodicity Stress Important The creep metals has been shown depend upon the length time any particular stress applied. there- fore, specimen subjected re- peated stress cycles, might expected that the resistance the material would depend upon the peri- odicity the cycles, and creep did occur, the form the creep curve would similar those under static stress. can shown that specimen steel containing 0.46 per cent carbon, subjected cycles ten- sion and compression 2000 cycles per minute, very small extensions took place, and finally the specimen broke after known number repetitions. stress range plus minus 31,808 Ib. per sq. in., and tempera- ture 745 deg. nearly 6,000,000 repetitions were resisted, and 34,- 048 Ib. per sq. in., and 766 deg. the specimen broke less than 250,000 repetitions. the case spiral spring tested 752 deg. rate oscillation 160 cycles per minute, when the mean stress was 44,800 Ib. per sq. in., the spring crept and broke after 5,000,000 repetitions. When the mean stress was 17,920 per sq. in., there was creep, but became less and less and fracture did not occur repetitions. interest notice, that with rapidly repeated cycles stress, ranges stress temperatures high 1112 deg. F., can resisted for many mil- lion cycles, nearly great that the material will resist ordi- nary temperatures. When the cycles are repeated slowly, say two three per minute, then the behavior the specimen very similar that under steady load. Under cycles stress tension from Ib. per sq. in., the rate cycles per minute, the form the creep curve not very different from that under static test. 817 deg. mild steel which had tensile strength 62,720 per sq. in. will, static test 13,440 per sq. in., settle down steady creep Under repeated tensile and compres- sive stresses 2000 cycles per minute will withstand range plus minus 31,360 Ib. per sq. for many millions reversals, but under cycles per minute range from 18,000 Ib. per sq. in. would probably cause creep and fracture few months. summarize—creep can take place fracture and lead static stresses temperatures above 572 deg. stresses much less than those which will break the spec