The Iron Age 1939-03-30: Vol 143 Iss 13

FRITZ FRANK President VAN DEVENTER Editor Managing Editor News Editor Editor Emeritus Machinery Editor Art Editor Metallurgical Associate Editors Washington Editor Resident District Editors Pittsburgh Cleveland Detroit Correspondents London, England Cinoinnati FRAZAR Boston Hamburg, Germany Milwaukee San Francisco Toronto, Ontario Birmingham fa Newark, N. J. St. Lowis TURNER, JR. MARCH 30, 1939 (Incorporated) Publication Office Offices Versatile Effects with Wrinkle Finish Chestnut and 56th Sts., 239 West St., Hand Motions for Small Assembly Work OFFICERS AND DIRECTORS MUSSELMAN, President Knocked-Down Steel House FRITZ FRANK, Executive Vice-President JOSEPH HILDRETH, Vice-President Precise Control New Welding Apparatus GEORGE GRIFFITHS, Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JOHN VAN DEVENTER, JULIAN Washington News THOMAS KANE, CHARLES BAUR, BAUR, General Advertising Manager Rate Activity Capital DIX, Manager Reader Service Member, Audit Bureau Circulations Plant Expansion and Equipment Buying Member Associated Business Papers tion Price: United States and Pos- sessions, Mexico, Cuba, $6.00; Can- ada, $8.50; Foreign, $12.00 year. Single copy, cents. Cable Address, Indexed the Industrial Arts Index. Published every Thursday. Subscrip- ADVERTISING STAFF Emerson Findley, 621 Union Bldg., Cleveland Just Between Two Herman, Chilton Bidg., Phila. Woodward Ave., Detroit Index Advertisers 122 Ober, 239 39th St., New York Box 81, Hartford, Conn. Copyright 1939 Chilton Com Uniform Results ... Lower Costs with Ryerson Certified Alloys You can reduce failures—eliminate spoilage and get better results less time with Ryerson Certi- fied Alloy Steels. They are from selected heats steel that meet ideal specification—a “specifica- tion within assures uniform response heat treatment. All Ryerson Certified Alloys are analyzed and tested advance. Special data sheets showing exact chemical analysis, grain size, cleanliness rating, and results actual heat treatment tests, are prepared and sent with every shipment. You know exactly what you are getting. Your heat RYERSO Principal products stock for Im- mediate Shipment include— Bars, Structurals, Plates, Iron and Steel Sheets, Tubing, Shafting, Strip Steel, Alloy Steels, Tool Steels, Stainless, Babbitt, Welding Rod, etc. 20—THE IRON AGE, March 30, 1939 treater does not have test. takes chances. Spoilage eliminated and sound, dependable jobs high accuracy and uniformity are secured. Ryerson has large and complete stocks these selected identified alloy steels. They cost more and quick shipment assured. Ryerson Certified Steels also include carbon, tool and stainless steels that meet definite quality standards. They offer many advantages steel users. Let tell you the complete story. Write for booklet. Joseph Ryerson Son, Inc. Plants at: Chicago, Milwaukee, St. Louis, Cincinnati, Detroit, Cleveland, Buffalo, Boston, Philadelphia, Jersey City. | 4 ‘3 4 Wij MARCH 30, 1939 ESTABLISHED 1855 Vol. 143, No. Whitewash! READER writes with reference improved machines and employment: you trying whitewash the machine? You know well that displaces labor. You know that when machinery salesman tries sell prospect, points out the labor-saving that will effected. that isn't adding unemployment, would like know what you call Now that question should answered, and shall be. First, are not interested giving the machine coat whitewash. wouldn't last long, did, and too many people would see through it. matter fact what are trying just the opposite. want wipe off the dust that coats the machine and prevents people from seeing actually is. people could see the machine is—not reported its enemies its friends—they would see that, like any other great natural economic force, has destructive well constructive effects. People drown because the existence water, but not outlaw water be- cause that. Fire destroys houses and industrial plants, but vitally necessary have available both. Machines displace men from jobs which they have been accustomed. And machines create new jobs that would not have existed otherwise. Machines will always and have always displaced labor. That what they are for. Oftentimes this displacement the form promotion better job. After the invention the wheeled cart, one man with the aid team horses could transport more material further hour than could 100 slaves hitched skid sled. Against this displacement, think over the fact that great industry could exist today and useful product broadly made and distributed had not been for the progressive introduction so-called machinery. need sense proportion weighing the results. The displacement effect improved machinery has been vastly exaggerated. How many men women you know, among the thousands your industry, that have been actually deprived em- ployment during because the introduction machinery? venture say that the total number thus affected not anywhere near the number killed automobiles during the same period. Society has duty accident prevention. And industry has duty ameliorate the effects technical displacement. But cannot outlaw technological advances any more than can outlaw water the automobile. ‘ | | | aving Weight and Fabrication Costs The many uses structural steel equipment well building construction offer numerous op- portunities for the services the Inland engineer prove real value. Weight often can reduced without sacrifice structural strength. Ease handling and appeal the buyer’s critical eye can often up.” The possibility saving tonnage fabrication cost leads sale price and net profit considerations, important competitive markets. Inland engineers offer broad experience such problems that will aid your staff securing the best possible results. Call your nearest Inland office for this service. Make use regularly connection with every use you may have for rolled steel any form. INLAND STEEL CO. y 7 South PILING RAILS TRACK ACCESSORIES REINFORCING BARS SHEETS section this article described solely the various methods which the austenitic grain size steel may determined, the factors in- fluencing the final austenitic grain size will now discussed gen- eral manner, inasmuch the results today are not sufficient warrant definite conclusions. Prior Structure (Heat Treatment): The influence prior heat treatment (which determines the structural con- dition the material) upon the austenitic grain size has been lately receiving much attention. the Grain Size Symposium, Gross- showed that when certain steels were given prior heat treatment their coarsening temperature varied. (Coarsening range the nomencla- ture applied the temperature ranges temperatures which the austenitic grain size begins show excessive grain growth coarsen- ing.) also noted some steels that the air cooled (normalized) speci- mens coarsened more readily than the the discussion the first ™M. Grossmann, Transactions .S. M., Vol. 1934, 861. *B. McCarthy, THE IRON AGE, Oct. and 17, CARL SHAPIRO Consulting Engineer, New York HIS the second section three-part article, and deals with the factors which influence the aus- tenitic grain size. Part describing the various methods which the austenitic grain size determined, appeared the 16, 1939, issue THE IRON AGE. Part Ill, de- scribing the effect the austenitic grain size upon the mechanical and physical properties steel, will ap- pear within the near future. furnace cooled, oil water hardened steels; whereas, others, this trend did not follow. explained this phenomenon the assumption that the prior structure (heat treatment) affected the degree dispersion the grain growth inhibitors the steel, which turn superimposed upon the initial grain size and, con- sequently, these factors combine influence the coarsening range. This conclusion was later verified other investigators. observe the effect prior struc- ture upon one per cent basic electric carbon tool steels, Schempp and Shapiro* carburized hr. 1700 deg. series heat treated speci- mens ranging from spheroidized martensitic condi- tion (hardening and tempering) and from coarse pearlite fine itic structure varying the cooling rates. The results obtained showed that some steels the structural con- dition, prior the McQuaid-Ehn test any other method used determine grain size, influences the final aus- tenitic grain size rating and that fine grained aggregate ferrite and cementite will yield small austenitic grain size; whereas coarse grain ag- gregate will yield coarse austenitic grain. However, other steels the same chemical composition, the results were markedly different. some cases, the austenitic grain size was identical, regardless prior struc- ture; others, the fine grained prior structure yielded coarse austenitic grain and vice versa, coarse grained prior structure yielded fine austenitic grain size. Investigating the cause these marked differences, was found that the deoxidation process varied slightly certain heats and, natural- THE IRON AGE, March 30, | ly, influenced the effect the prior structure upon the austenitic grain size, will shown later. The effect prior structure upon the austenitic grain size eutectoid steel was also studied Tobin and rolled eutectoid steel were that the final austenitic grain size same whether the steel had coarse fine-grained prior structure. From the investigations mentioned, which are also supplemented other investiga- tors, appears certain that the effect prior structure upon the austenitic grain size cannot predicted unless knowledge the melting and de- oxidation methods had since they determine the final grain growth be- havior, especially after prior heat treatment. Mechanical Deformation: Mechani- cal deformation may divided into two classes, hot and cold work. The difference between these two that the former—hot work—implies that recrystallization has already occurred during working since the temperature mechanical deformation above whereas, the latter, mechanical deformation occurs below the temper- ature recrystallization and the ma- terial distorted condition capable grain growth grain re- finement, depending upon the time and temperature recrystallization. (The function the degree cold Therefore, these two factors, hot and work, ate studied separately. Hot Work: showed hypo-eutectoid steels that hot work the coarsening range, the grain size larger. However, should borne mind that the coarsening range variable and that increasing centages mechanical deformation automatically lower the coarsening range. This shown Grossmann Fig. Schempp and also showed the effect variation reduction constant temperature heating bars 2000 deg. and forging them quickly point. Their results sub- stantiate Grossmann’s findings that the coarsening temperature lowered with the degree hot work. They RIGHT Fig. effect cold work upon the austenitic grain size, deter- mined the car- burizing test. 100 diameters. BELOW FIG. TEEL No. (Table showing the results prior hot work- ing the case. (Grossmann.) may result either finer coarser grained McQuaid-Ehn grain size, de- pending upon the finishing tempera- ture. the finishing temperature below the coarsening range, the re- sultant grain size smaller; above Hough, Cooperative Bulletin 65, Advisory Board Carnegie Institute Tech- nology. back, Transactions M., Vol. XXV, 1937, TABLE The Effect the Degree Cold Drawing the Austenitic Grain Size Diameter, Reduction Austenitic Grain Size 0.270 0.20 7/8 7/8 6/8 4/6 0.223 0.46 7/8 7/8 6/8 4/6 0.203 0.55 7/8 6/8 4/6 0.180 0.65 7/8 7/8 6/8 4/6 0.160 0.72 7/8 7/8 6/8 4/6 24—THE IRON AGE, March 30, also investigated the effect temper- ature (constant reduction) upon the austenitic grain size and found that the depth carburization and grain forging temperature. Cold Work: The effect cold me- chanical deformation upon the aus- tenitic grain size, determined the carburizing was effectively revealed and Schempp and They found all steels examined that (1) the coarsening range progressively lowered with the amount reduction; (2) grain refinement occurred below the coarsening range the hot worked steels; and (3), soon the coarsening range reached, grain growth becomes function the degree deformation (constant time and temperature). order determine whether the effect grain size variation after cold work was caused (a) re- crystallization below critical range, (b) slow heating the austenitic temperature (1700 deg. F.) bent bars in. diameter) similar the one shown Fig were heated the author 1100 deg., 1150 deg. and 1200 deg. from hr. and air cooled. These cooled heat treated bars were carburized hr. 1700 deg. with series un- heated bent bars and examined micro- scopically. The results obtained, after the ap- plication the McQuaid-Ehn showed that the 2 A j 3 | worked specimens which heated below the thermal critical range invariably possessed coarser austenitic grain size than those which were not reheated below the critical range. These findings definitely indi- cate that (a) grain growth occurred prior carburizing and that the Mc- test only outlined and in- tensified the variation prior struc- ture caused cold work and re- crystallization, and (b) the rate heating the carburizing temperature influences the austenitic grain size slower heating rates resulted Ferrite Solubility FIG. YPOTHETICAL curve solu- bility ferrite and aus- tenite, function tempera- ture. (Dorn and coarser austenitic grain size than the faster rates heating. Since the degree cold work has been shown affect the coarsening range and the susceptibility grain growth, seemed advantageous determine whether there existed any critical amount reduction that would tend establish the austenitic grain size. ascertain this factor, four carburizing steels the two per type were hot rolled from 3-in. square billet 0.303-in. round and then gradual- cold drawn successive steps, without any intermediate anneal, 0.160-in. diameter. The degree cold drawing and the results obtained upon these steels after carburizing hr. 1700 deg. are tabulated Table The data Table supplemented other results, show that the aus- tenitic grain size, determined the McQuaid-Ehn carburizing test, well established after per cent cold FIG. FFECT time and temperature heating the austenitic grain size eutectoid steel. (Tobin and Kenyon.) ASTM. Grain Size Number ‘ll Hours 2845 10,000 Minutes draw, and subsequent drafting does not increase the grain size although variation carburizing time and temperature will markedly affect these results. This percentage reduction (20 per cent) may termed the “critical amount deformation” and any reduction above amount does not seem greatly in- fluence the austentic grain size this type steel. (Although steels and have rating the hot rolled state (0.303 in), they are predomi- nantly with few the 0.270 in. rd.) summarize the effect cold work upon the austenitic grain size, may stated that the austenitic grain size cold worked steels influenced (1) the amount re- duction, (2) the rate heating the thermal critical range which con- recrystallization and grain growth alpha iron, and (3), the time and temperature above the ther- mal critical range which turn con- trols the austenitic grain growth. Influence the Rate Heating upon the Austenitic Grain Size: Since the rate heating cold worked steels influences the austenitic grain size, was determined note whether the same trend maintained un- worked steels. perusal the litera- ture showed that this effect was studied and Tobin and stated that the initial grain size austenite not. appreciably affected the rate heating through the thermal critical range. However, Herty, McBride and and Herty, McBride steels, the initial grain size inde- pendent the rate heating; function the heating rate, and the heating rate increases the initial grain size becomes coarser. Dorn and verified the after extensive study the effect the various rates heating through the transient range, and came the following conclusions: (1) chemical substance (or sub- stances), which Dorn and called results from deoxidation with aluminum and has, general, the solubility trend indicated Fig. (2) The inhibited austenite grain growth aluminum killed steels result the precipitation this substance (or substances) the grain boundaries the newly formed austenite grains. (3) The precipitation the chemi- cal substance (or substances) called “X” may occur any the follow- ing mechanisms: (a) heating temperatures below the thermal criti- cal range produce maximum solu- bility the grain growth inhibiting material ferrite, (b) heating relatively high temperature and then lower solubility the inhibitor ferrite; (c) heating directly from the saturation temperature (1250 deg. F.) “X” quenching from the satura- tion temperature and reheating rapid- results finer austenitic grain THE IRON AGE, March 30, than the material were cooled slow- from the saturation temperature and reheated. From the foregoing which sup- plemented other investigators, may stated that the initial austen- itic grain size unworked steel function (1) deoxidation and (2) heating rate through critical range. the deoxidation the material during melting results the contamination, rather, alloying the steel with grain growth inhibi- tors, the rate heating secondary and the initial austenite grain size immediately above the critical function deoxidation. However, sufficient grain growth inhibiting ma- terial not present, rimming (un-killed) steel, the rate heating through the critical determines the initial austenitic grain size. The Effect upon Grain Size Since the preceding paragraphs illus- trated the influence the rate heat- ing through the thermal critical range upon the initial austenitic grain size, the effect (maximum temperature) upon the final austenitic grain size now considered fully, although was briefly mentioned under the subject heading dealing with the effect prior structure. order study the full effect upon the austenitic grain size and understand its importance, the sub- ject must subdivided into two headings; namely, (a) the effect normal atmospheres and (b) the effect during carburiza- tion. (a) Since grain growth func- tion time and temperature, will discussed later, the influence upon grain size also controlled time (time temperature). How- ever, for constant time, the effect and These results show that the austenitic grain size eutectoid steel increases progressively with temperature and also with time. This illustrated graphically Tobin and Kenyon Fig. where the results are plotted logarith- mic scale. (b) The effect during car- burization similar (a) but more intense since the process carburizing usually involves long time element hr.), depending upon composition, case depth, car- burizing temperature, size, etc. Con- sequently, for constant time during carburizing, the austenitic grain size increases more rapidly during car- burization than normal atmos- pheric conditions since the continuous impregnation carbon the ferritic matrix the material progressively lowers the transformation range and coarsening temperature. result this automatic change during the carbon impregnation, grain growth flourishes more freely the areas subjected carburizing (case) than the unaffected portion the ma- terial (core). This effect however, cannot predicted from the McQuaid-Ehn carburizing test alone but from series carburizing tests using constant time and temperature similar the McQuaid-Ehn test. ALA AA TABLE Austenitic Grain Size Standard Nos.) After Various Heat Treatments Temperature Time Temperature, Minutes 1400 1800 3000 4500 5520 2 ‘ IRON AGE, March 30, 1939 ° ° FIG. mechanism the formation austenitic grain nodular troostite. 4000 diameters. Mechanism the Austenitic Grain Growth: compiete the picture the influence the various factors upon the ultimate austenitic grain size and characteristics steel, es- sential understand the mechanism which ferritic grain transforms austenitic grain and how the final austenitic grain size may pre- dicted from its previous history. first showed annealed hypo-eutectoid steel that the austenitic islands, the grain boundaries between the grains when they are heated through temperature. These nucleii gradually grow across the pearlitic areas and through the ferrite until the specimen entirely austenitic. also determined the man- ner which the austenitic grains are formed various heat treated eutec- toid steels. pearlitic steels, ob- served, Grossmann did, that the first austenitic nucleus usually formed the grain boundaries and less often favored locations the grains. Whenever the austenitic nucleii formed within the pearlitic grain they were generally right angles the orientation the cementite plates. Many instances were also observed where coarse white bands replaced the cementite plates and, upon con- tinued heating, quickly formed aus- tenitic areas which progressively dis- solved the surrounding pearlite. spheroidized steels (quenched and tempered), Shapiro revealed that the areas around certain cementite ay * FIG. mechanism the formation austenitic grain nodular troostite. 4000 diameters. spheroids gradually transform and form gamma grain boundary which continually dissolves the surrounding and enclosed material form aus- tenitic area sufficient time tem- perature given. Transformation troostitic steels (oil quenched) was shown begin either center the troostite nodule the grain boundaries. The formation austenitic nucleus the center troostite nodule shown Fig. Fig. re- veals the formation gamma grain boundary from the nucleus the troostitic nodule. These areas grow continually with time three strands insulated conductor wire are twisted and wrapped with insulating paper, then armored with galvanized steel strip and cut designated lengths this new combination cable armoring machine, recently built Sleeper Hartley, Inc., Worcester. The spools wire are mounted the strander head the extreme right. The armoring strip stock supplied from split spool which, when empty, may removed from the head with- TAKE-UP CUT-OFF perature until the entire specimen be- comes austenitic. From the foregoing discussions describing the various factors which influence the austenitic grain size and the manner which the initial aus- tenitic grain formed, therefore, only state that the final austenitic grain size any steel in- fluenced by: (1) prior structure initial grain size, (2). mechanical deformation (hot and cold work) which remains conferred upon during austenitizing, (3) the rate heating the austenitic condition, (4) time and temperature heating (5) method deoxidiza- SPOOLER HEAD tion and (6) the type inhibitors resulting from process. These factors may either intensify minimize one another’s effects and thereby may either refine increase the austenitic grain size, depending whether they act like opposite manner. These initial formed their own characteristic manner the various aggregates, grow fast time and temperature permit. all things are equal, the finer grains grow faster than the coarser until they reach the same size and then, with further heating (time temperature), the finer grained steel becomes coarser than the originally coarse material. This latter statement has been borne out many experiments and may at- tributed the fact that the inhibitors, which originally cause grain refine- ment, induce grain growth once certain critical temperature range passed. This so-called critical tem- perature range where grain growth flourishes determined the type inhibitors used deoxidation, g., vanadium, aluminum, etc. result this tendency, the fine grained steels temperatures excess 1900 deg. form coarser austenitic grain size than the originally coarse material. This rule does not hold for all steels but has been observed mostly fully-killed basic electric steels. Ed. Note: The third and last section this article, dealing with the effect the austenitic grain size upon the physical properties steel, will appear within the next two issues. out necessity cutting. The spooler, third line, has hollow spool spindle with rotating head and quick-release jaw. equipped with double screw traverse mechanism that lays the desired width strip stock the spool. Full spools, after winding, are shifted from the spool the armoring head means chain fall. The measuring device and cut-off saw operate automatically while the machine operation. STRANDER THE IRON AGE, March 30, 1939—27 d | HIS article fully pursue more than limited number aspects light al- loys for aircraft. The intention deal briefly with the more generally discussed features the subject, and then introduce number features which less has been publicly said written. The production aircraft com- ponents castings commends itself forcefully, owing the ease pro- duction large quantity and the favorably low cost, compared with wrought forms. The present high de- gree efficiency X-ray examina- tion has contributed substantially the production sound castings two important ways. the first place has provided means ex- amination individual castings for defects, and has achieved second and probably more important providing the manufacturer with practical aid developing the best methods producing the casting con- cerned. Experience indicates that for success, necessary that design should evolved with due considera- tion the duty performed and the requirements the foundry for the production satisfactory casting. This means that the designer and founder must collaborate the Abstract lecture before the Mid- land Metallurgical Societies, Birmingham, England. IRON AGE, March 30, 1939 evolution satisfactory design for casting alloy best suited the general requirements. regards castings for important components subjected stresses service, the following are important features: (a) The static strength properties that can relied upon developed each particular casting. (b) many applications the ability the material withstand fluctu- ating alternating fatigue stresses. (c) The effects occasional over- loading, e.g., brittle fracture plastic deformation. (d) The permanence the casting under operating conditions. For the use castings com- ponents performing such important duty that failure particular cast- ing might imperil the entire aircraft, will appreciated that very high standards quality are the other hand, the applications castings aircraft are becoming increasingly numerous and the duties performed more and more vital. Aluminum alloy castings different types are used for aircraft purposes, the heat-treatable casting al- loys forming very important group today. This group may sub-divided into casting alloys heat treated low temperatures only, and casting alloys solution heat treated and then given low temperature treatment. low temperature heat treatment lowers the elongation value without rendering the castings unduly brittle, but usually increases the ultimate stress slightly and the appreciably. These effects arise from age-hardening the raised tempera- ture heat treatment, the cooling from the liquid state the mold re- sulting some retention solid solution condition. important prac- tical advantage lies the fact that internal casting stresses are released appreciable extent and danger future distortion much reduced. Double heat treatment, i.e., solution heat treatment followed aging elevated temperature, applied number important alloys, princi- pally for the development high strength properties. This frequently entails precautions against distortion the moment quenching, especi- ally for the larger castings. general, the double heat treatment effects substantial increases ultimate and proof with decrease elongation value, to- gether with improved machineability. There increasing use cast- ings pressure systems and pressure tightness here all important. Micro- porosity the inter-dendritic shrink- age type frequently not discernible radiography. light sections particular, this type porosity liable troublesome. Castings 4 ~ SUTTON By Chief Research Chemist, Aircraft Research Board, England pressure tight air liquids represent field which there seems scope. For very wide range small components there frequently not the same need for very high strength, and heat treatment generally not necessary for larger components. The high silicon type aluminum casting alloy used for aircraft parts which high intrinsic resistance corrosion re- quired. The proof stress and ultimate stress values are raised substantially the double heat treatment and moderately the case single heat treatment. indicated the results both laboratory tests and service experi- ence, the corrosion resistance not seriously impaired the heat treat- ment, while the machining properties are improved. The high magnesium type aluminum casting alloy amen- able the double form heat treat- ment and developing high strength development. The basic alloy con- taining 4.6 per cent copper and 0.9 per cent silicon with small amounts other elements, gives good response heat treatment both the single and double types. The strength properties are high for aluminum castings and the elongation value the single heat treated ma- terial high for sand cast alu- minum alloy. the field the wrought alu- minum alloys, duralumin the duralumin type remain the most important type high strength single heat treatment alloy. This type alloy very well known, but demands some attention. The fact that has been known long and used ex- tensively is, itself, tribute the value the material. with other materials, experience and the indus- trial application the results re- search have yielded improved prod- uct. recent years there have been many developments this field light alloy technology. The alloys are available the form sheets, bars and extrusions. They have high ulti- mate and 0.1 per cent tensile proof stresses, good working properties and high resistance corrosion. The improved mechanical properties com- pared with duralumin are obtained very slightly increased amounts alloying elements, notably magnesium and suitable control the other ad- ded elements. Duralumin Improved The double heat treatment type improved duralumin alloy has found extensive use modern aircraft. Here the optimum mechanical properties are obtained applying first solu- tion heat treatment and then aging treatment raised temperatures, say uct the skill and careful adaptation the part the plane builder. Many alloys are now used: the single and double heat ment types duralumin and magnesium alloys many types, including alloys carry- ing cerium and cobalt. Service failures such light alloys remarkably rare. ° ° the elevated aging treatment, the ulti- mate stress usually raised slightly and the 0.1 per cent tensile ‘proof stress appreciably, the ductility ing reduced slightly. The corrosion are affected adversely, notably regards resistance the intercrystalline type corrosion. the other hand the alloys are capable being used satisfactorily suitable protective treatment and coatings are applied. The aluminum clad material that respect, the re- sistance corrosion and mechani- cal deterioration being much increased the aluminum coating. Mention should made new high strength wrought aluminum al- loy recent origin. The alloy con- cent magnesium, 1.5 per cent copper, one per cent nickel and small amounts other elements. present the alloy being supplied the form extrusions which, after appropriate double heat treatment, have strength properties the order 60,000 74,000 per sq. in. tensile proof stress, and 74,000 85,000 Ib. per sq. in., ultimate tensile strength, with per cent elon- gation. The specific gravity about 2.8. The alloy, this condition, ap- pears possess good resistance corrosion, judged laboratory tests. The results practical experi- THE IRON AGE, March 30, 7 1€ ence this material will awaited with interest. For hulls and floats sea-going aircraft constructed light alloy, aluminium coated sheets are widely used. The present stage metal air craft development involves extensive use these high strength light alloys not only for skin coverings, but also for ribs, stiffeners, spars, and wide skins, resistance wear and tear service and handling may place the stronger alloys position ad- vantage. The extensive use ex- truded forms for spars, frames and stiffeners perhaps the standing development the present time. For many components, good bend- ing and forging properties are neces- aluminium alloys possessing excellent working properties from which the designer may choose his material ac- cording the strength properties de- sired the finished component and the method manufacture. Most these materials possess high resistance corrosion. some degree the position attained modern magnesium alloy castings regards physical properties. The bene- fits heat treatment are very marked here and more marked the results practical experience than the speci- fied mechanical properties bars would suggest. the light present experience, these values that are specified can exceeded appre- ciably. The author believes that the improved ductility solution heat treated magnesium alloys tributed substantially the success and reliability the castings ser- vice. the case aircraft landing wheels, for instance, there has been abundant experience show that the castings, suitably designed cuted, can give satisfactory service under conditions shock loading. The quantity magnesium alloy castings used aircraft now very large and appears likely increase further. The low density the alloys, the mechanical properties, good gen- eral standard quality attainable castings and the excellent machining properties are all important practical points the aircraft constructor. Fur- ther, the modern methods protection against corrosion coupled with the higher intrinsic resistance the al- loys have permitted satisfactory ser- vice life obtained under all except the most extreme conditions use. would misleading one were 30—THE IRON AGE, March 30, 1939 give the impression that there were difficulties that failures did not occur. These have occurred with most aircraft materials. Application principles, when these dangers are realized, doing much overcome troubles. Porosity magnesium castings has given some trouble especially when designers have been too ardent sav- ing weight. The best treatment the problem porosity castings that which leads its elimination. Advances have been realized pres- sure tightness magnesium alloy castings the development alloys suitable composition, and with im- proved technique design and casting are bringing magnesium alloy castings into use pressure systems. alloy has been developed specially for castings required cent tin, per cent aluminium, 0.25 4.0 per cent silver, magnesium alloy. Sand cast test bars have stress 0.10 about 9000 Ib. per sq. in., ultimate stress 20,000 27,000 Ib. per sq. in. and elongation this alloy yields castings having uni- form properties. Magnesium Alloys Workable Magnesium alloy sheets two types are used aircraft work. The first type, made the alloy con- taining about per cent manganese. The second type the aluminium- magnesium alloy and contains per cent aluminium, 1.5 per cent zinc and 1.0 per cent manganese. Simple bending and shaping operations can formed the cold, but most opera- tions forming and shaping are carried out heated material. Both these materials can welded with the acetylene torch using flux and filler rod the same alloy. Development work now improved alloy the same family appears likely provide alloy capable being worked more severely normal temperatures. Mag- nesium alloy forgings, stampings and bars afford material 20,000 25,- 000 Ib. per sq. in. proof stress and 31,000 38,000 Ib. per sq. in. mate stress. New developments indi- cate that these properties can im- proved and that stronger alloys will available. Magnesium alloy propeller blades have shown remarkable The alloy used for the modern magnesium alloy propeller blade contains 9.5 per cent aluminium small amounts zinc and manganese. The blade blanks are the product power- ful presses. The form propeller blade the detachable type one that does not make easy the produc- tion forgings having uniform properties all parts. The labors those concerned the production these forgings have been fruitful however, yielding product very uniform properties indeed. major practical importance con- nection with practical applications recognition the notch sensitivity magnesium-rich alloys both cast and forms. Sharp corners and sudden changes section must Cerium Used Pistons loys recently evolved are special interest for parts subjected raised temperatures and seem likely take the magnesium alloy piston consider- able step forward. Aircraft structures are designed that they will not collapse before with- standing external loads corresponding the specified ultimate factor. The structure must airworthy condition after carrying per cent the ultimate loads for one minute. This load known the proof load. Members tension are designed the ultimate strength the material. The ultimate factor based the ultimate stress and the proof factor the 0.1 proof stress. For members stressed compression, the ultimate factor estimated from strut formu- lae based the 0.2 per cent proof stress. can generally assumed for such members that compliance with the ultimate factor requirement will automatically ensure compliance with the proof factor requirement. Owing the necessity for keeping weight down minimum, consider- able care has taken structures make the most economical use material. This leads the use thin sections. The increased need torsional wing stiffness due the speeds modern aircraft has led the development stressed skin con- struction. The use thin sections introduces risk instability failures due buckling the material stresses well below those which the material can develop thicker sec- tions. This type instability has usually predetermined from me- chanical tests suitable sections. The stability these thin sections more (CONCLUDED PAGE 92) q 7 + wrinkle finishes, there ten- dency feel that they are dif- ficult apply order obtain uni- form results. This not the case, according one maker this type finish, New Wrinkle, Inc., Dayton, Ohio. said that such finishes are among the easiest use, there being only two things that must watched clean spray gun nozzle and uni- form heat throughout the oven. furthermore stated that, (1) the product finisher does not have careful about avoiding careful about dirt dust his finishing room, (3) there should flaws wrinkle finished surface, they are not apparent the naked eye, (4) wrinkle finish one coat application, and (5) inexpensive base metal may often used wrinkle finish fills all the seams and hides other flaws under single coat. Regardless the wrinkle effect de- sired, one caution has with the colors selected. When pastel shades are chosen care must exercised against overheating. Because pastels being delicate, too much heat has tendency burn the colors, but this not true standard colors their pigments are basic. Sag wrinkle has the appearance draped curtains, shown the ac- companying illustration. combi- nation bakelite, varnish and synthetic base, and when applying this finish metals and other materials which will stand heat, must sprayed heavy enough create “runs.” then baked 225 deg. for hr. Pine tree wrinkle, its name im- plies, looks like miniature pine trees uniformly distributed over the entire finish area. Heavy, medium small design governed the amount material sprayed, adjusted the noz- zle the spray gun. caused very small “runs” which set immedi- ately heat applied, and requires bake hr. 225 deg. small wrinkle more universally ap- plied. establishes uniform design over the entire finished surface with each individual wrinkle identical size and character. Typical products which this wrinkle finish used include automobile radios, air condi- tioning equipment, heating units, metal boxes all kinds, medicine cabinets, business machines, etc. Opalescence wrinkle the same basically uniform wrinkle. (See accompanying illustration.) The dif- ference finish acquired adding opalescence the uniform wrinkle formulations give them more variant color effect such irides- cent array pearl-like colors, con- trast solid colors. “Birdseye,” describes wrinkle finish exceptional char- acter found such products high quality laboratory equipment, aircraft instruments, coin banks, beauty parlor equipment, clocks, door chimes, etc. Such wrinkle requires more care application than any the other wrinkle finishes, but does not offer complications the product finisher practices judgment its use. While varying effects are obtained based the size the “eyes” de- sired, but one formulation required. The variation derived from the amount material sprayed. The prod- uct then put into the oven and baked for hr. heat 100 150 deg. This sets the “eyes” and now ready for 3-hr. bake 225 deg. THE IRON AGE, March 30, SAG WRINKLE—Medium OPALESCENCE WRINKLE—Medium > | . | { ANAGEMENT has been slowly developing from art into applied science. Today industrial managers and industrial engineers, increas ing extent, look the basic sciences for data use solving their prac- tical problems. Since all manual work consists various combinations but fundamental motions, has seemed logical make investigations some the most important these motions with the purpose finding fundamental data that might have wide use. The data given fundamental investigations this na- ture. One section the study deals with the time required handle small parts, and subdivided into. (1) study the time required grasp washers from flat surface using “hook” grasp and “pinch” grasp, and (2) study the time required grasp machine screw nuts and ma- chine screws from various types bins. The second section the study deals with study the time required assemble screws with the three dif- ferent types screwdriver bits. should particularly noted that general conclusions could safely based only investigations much broader scope than presented herein, and these studies are therefore pri marily indicatory nature. From analyses the movements the various members the human body performing many different kinds Extensive abstract report just issued the University Iowa, and continuation investigations reported 1936 and 1938. 1Therblig word coined Frank Gilbreth designate the subdivisions events that thought common all kinds work. Although the therbligs are not all pure elements the sense that they cannot further subdivided, they are the best classification hand motions available. 32—THE IRON AGE, March 30, 1939 work, has been found that all tions may divided into different well defined classes. These funda- mental motions are wide- known and will used study. The therbligs together with their mnemonic symbols are follows: (1) Search (Sh.) Search refers that part the cycle during which the eyes the hands are groping feeling for the object. Search may performed with either the eyes the hands. (2) Find (F.) Find occurs the end the therblig search and represents more movement. (3) Select (St.) Select refers the choice one object from among several. many cases difficult not im- possible determine where the boun- daries lie between these first three therbligs. For this reason usually the practice combine referring the group the one therblig select. Using the broader definition, select then refers the searching, finding, and se- lecting object. Select usually oc- curs between the therblig transport empty and the therblig grasp. However, there therblig select when parts are pre- positioned for such cases transport empty followed directly grasp. (4) Grasp (G.) Grasp refers tak- ing hold object, closing the fingers around preparatory manipulating it, picking up, holding it. This therblig begins when the hand fingers first make contact with the grasped and ends when the hand fin- gers have reached the position necessary for the performance the next therblig. (5) Transport Loaded (T.L.) port loaded requires that change the moving object from one place another. The object may carried the hands fingers may moved from one place another dragging pushing along. (6) Position (P.) Position consists turning locating object such way that will properly oriented fit into the location for which in- tended. possible position ob- ject during the therblig transport loaded. The carpenter, for example, may turn the nail into position for using while carrying the board into which will driven. Position usually follows the therblig transport loaded and pre- cedes the therblig use. (7) Assemble (A.) Assemble consists placing one object into another object with which becomes integral part. The therblig begins the hand starts move the part into its place the assembly. The motion ends when the hand has completed the assembly and just hegins release the part. (8) Use (U.) Use may almost infinite number particular cases. always consists manipulating tool, device, piece apparatus for the pur pose for which was intended. Use the most important all therbligs. represents the therblig for which the pre- ceding therbligs have been more less preparatory and for which the ones that follow are supplementary. the instant the hand applies itself manipulating device such way that the device functions for the purpose was intended and ends the instant the hand ceases the application the next therblig. (9) Disassemble (D.A.) Disassemble consists separating one object from another which integral part. The therblig begins when the hand starts remove one part from the assembly. The motion ends when the hand has sep- arated the part completely from the re- mainder the assembly and begins the next therblig. (10) Inspect consists testing examining some property mental reaction and may taneously with other therbligs. (11) Pre-position (P.P.) This therblig the same position with the added qualification that pre-position refers positioning object predetermined place such way that may held when needed. This elim- inates the therblig position which would otherwise necessary after the object was grasped. Usually holder, bracket, special container some kind used for holding the object way that per- mits grasped easily the posi- tion which will used. Pre-position the abbreviated term used for pre- position for the next operation. (12) Release Load (R.L.) Release Load refers that part the cycle dur- | j 7 » 7 7 7 RALPH BARNES and MARVIN MUNDEL College Engineering, University ing which the hand letting the object grasped—letting slip out the hand. This therblig begins when the object starts leave the hand and ends the object has been completely sepa- rated from the hand fingers. (13) Transport Empty (T.E.) port Empty consists moving the empty hand reaching for object. This therblig usually begins the instant the hand begins reach for object and ends the instant part the hand comes contact with the object grasped. (14) for Overcoming Fatigue (R.) Rest for overcoming fatigue fatigue delay factor allowance pro- vided permit the worker recover the fatigue incurred his work. (15) Unavoidable Delay (U.D.) Un- avoidable delay may result from either (a) failure interruption the proc- ess, (b) delay caused arrange- ment the operation which prevents one part the body from working while other members are busy. (16) Avoidable Delay (A.D.) Avoid- able delay refers any delay the op- erator for which responsible and over which has control. refers delays which the operator may avoid wishes—(a) this therblig assigned most cases where there avoidable stopping all motions the hand, and (b) delay avoidable when occurs work that requires delay. (17) Plan (Pn.) Plan refers men- tal reaction which precedes the physical movement, that is, deciding how pro- ceed with the work. (18) Hold (H.) The therblig has been used some separate and distinct element. Strictly speaking, form grasp and was considered such Gilbreth. Hold denotes the re- tention the object after has been grasped, movement the object tak- ing place. Time Required Grasp Washers From Flat Surface Grasp vs. Grasp object this investigation was determine the effect washer thickness and manner grasp upon the time required for grasp, position, release load, and transport empty, when mov- ing washers from one flat surface second flat surface approximately five inches closer the operator. The washers used were circular, in. diameter with in. hole the center. The following four washer thicknesses were used: 1/32, and in. The flat surfaces from which the washers were grasped and which they were deposited were the form grids made eight brass bars in. wide, in. thick and in. long. Fiber spacers, in. wide, were used insulate each brass bar electrically from the others. The bars and the spacers were glued together and firmly screwed base support shown Fig. The top surface this assembled plate was milled smooth and the spacers were undercut 1/32 in. that the washers would make good contact with the brass bars. The bot- tom surfaces all washers and the upper faces the grids were coated with mercury further insure good contact all time between the wash ers and grids, 1—Examples grasp: Top— pinch pressure grasp being used pick brass washer in. thick. Bottom—hook lip grasp being used pick brass wash- thick. Seven washers were placed along the edge the “grasp” grid, each directly over fiber strip. photo- electric cell was placed in. above the grasp grid. Mechanical electrical recording equipment served indicate the moment the operator reached down grasp washer (as light beam photocell was interrupted), the mo- ment washer was removed from the grasp grid (as electrical contact was broken), and moment the washer was placed corresponding position the “release” grid (as electrical con- tact was made). Time measurements were kept the nearest thousandth second. The sequence therbligs for one cycle the task was follows: Pick one washer from “grasp” grid carry washer second grid an