The Iron Age 1941-08-28: Vol 148 Iss 9

AUGUST 28, 1941 the New Departure production plane being produced ball bearing ever made America. Has balls, equally spaced head pin. characteristic New Departure precision manufacture. L ry AUG it : 2 n 5 ( S SS SS AUGUST 28, 1941 VOL. 148, NO. VAN DEVENTER President and Editor BAUR Vice-President and General Manager ° ° Managing Editor, LIPPERT News & Markets Editor, J. A. ROWAN Machine Tool Editor, OLIVER Associate Editors: COSMAN Art Editor, WINTERS Editorial Assistants: M. M. SCHIEN G. B. WILLIAMS Washington Editors MOFFETT JAMES ELLIS Resident District Editors CAMPBELL HERMAN KLEIN Pittsburgh Chicago Cleveland Detroit CHARLES POST San Francisco Editorial Correspondents DEARING Buffalo Cincinnati FRAZAR RAY KAY Bostor Los Angeles HUGH SHARP JOHN McCUNE Milwaukee Birmingham SANDERSON ROY EDMONDS Toronto, Ontario St. Louis Newark, Seattle ° ° Manager Reader Service ° ° Advertising Staff Emerson Findley Blair 62! Union Cleveland Herman, Chilton Bldg., Philade!phia Hottenstein, 1012 Otis Bldg., Chicago Leonard, East 42nd New York Peirce Lewis, 7318 Woodward Ave., Detroit Ober, East 42nd New York Fitzgerald 428 Park Bldg., Pittsburgh Warren, Box 81, Hartford, Conn. Don Harner, 1595 Pacific Avenue, Long Beach, Cal. ° ° ° Member, Bureau Circulations Member, Associated Business Papers Indexed the Industrial Arts lished every Thursday. Subscription Price United States and Possessions, Mexico, Cuba, $6.00; Canada, $8.50: Foreign, $12.00 year. Single copy, cents. ° Owned and Published CHILTON COMPANY (Incorporated) Executive Editorial and Office Advertising Offices Chestnut and 100 East 42nd St. Philadelphia, Pa. New York, N. Y. U.S.A. U.S.A. OFFICERS AND DIRECTORS MUSSELMAN, President JOS. HILDRETH, Vice-President GEORGE GRIFFITHS Vice-President TERHUNE, Vice-President VAN DEVENTER, Vice-President BAUR, Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JULIAN CHASE, THOMAS KANE, HARRY DUFFY CHARLES HEALE This Week ROBERT . . Editorial Among the Four Freedoms Technical Articles Magnetic Testing Simplified Optical Flats Corrosion Resistance Irons and Steels Etching Technique California Magnesium Plant Starts Production Comparable Tool Steel Features Assembly Line Washington The West Coast Fatigue Cracks News and Markets This Industrial Week News Industry Government Awards Personals and Obituaries Construction Steel Machine Tool Activity Non-Ferrous Metals Scrap Markets Iron and Steel Scrap Prices Comparison Prices Finished Steel Prices Warehouse Prices Sales Possibilities Information Free Products Advertised Index Advertisers Copyright, 1941, by Chilton Company (Inc.) New Heat Treating and Process Control Equipment 132 161 CARL * — 110 115 118 | ; yerson Night Loading Assures Quicker Deliveries after hours, any the ten Ryerson steel plants, almost any night the year! The Ryerson night shift putting the finishing touches today’s orders; loading out the fleet big, red Ryerson trucks for tomorrow’s deliveries. The entire Ryerson organization geared han- dle quickly the steel requirements, simple involved, thousands customers the country over. Special telephone order desks, hourly mail pick-ups the post telegraph and teletype lines into our offices—all help speed delivery, even before the order reaches us. Night loading “clear the decks” for tomorrow’s new crop orders the regular course business. Every order RUSH Ryerson. Ryerson Steel Service fast and sure today’s unusual circumstances will permit. Ryerson Certified Quality your assurance uniformity and exactness. Make the Ryerson Stock List your number one source for all steel requirements. you haven’t the latest Stock List send one gladly. Joseph Ryerson Son, Ine., Chicago, Milwaukee, St. Louis, Detroit, Cleveland, Boston, Philadelphia, Jersey City. Yj Yj Y, AGE AUGUST 28, 1941 ° ° ESTABLISHED 1855 Among the Four Freedoms “four which have been laid before the inalienable and unshakable foundations democracy must surely include the right change one’s mind. Thus, our antici- pated state personal liberty after emerge from emergencies, one should able quit golf club sees fit, leave the ranks the Republicans and become Democrat and even change his religion without incurring the risk extreme pen- alties, least this world. course, time like the present, one might well concede some limitations upon personal liberty, when individual mind changing impinges upon public welfare. Thus, our boys the Army camps and the Navy who decide call day before their time are labled AWOL and are visited afflictions when caught with. However, even emergency, our government extremely liberal its attitude toward mind changing the part citizens not uniform, even though this may and does directly impede the defense program. case point the strike the Federal Shipbuilding Drydock Co. Here, the Industrial Union Marine and Shipbuilding Workers (CIO), after agreeing that there would more strikes until June 23, 1943, changed its mind and struck compel the company prevent union employees from changing their minds about continuing belong the union. The process compulsion called for the union bosses was the simple and effective one having the company boot such mind changers out the plant gates and tell them seek employment elsewhere which, effeci, meant permanent excommunication from the right work the trade, for the shipbuilding industry pretty well organized. And anyone thinks that backslid unionist could simply another shipyard and get job non-unionist—and hold it—he does not know much about human, inhuman, nature. With such great principles stake the right union lead- ers change their minds and the the rank and file their membership so, the holding half billion dollars worth vitally needed warship and cargo ship construc- tion for several weeks was quite inconsequential. For what making the world safe for democracy compared making America solid for the CIO? 4 3 = > 4 A ° 4 ° 4 | q | Ss. i Re thousand airplane motors month will soon streaming from Buick’s new plant. Steel from INLAND Helps Build Buick’s Chicago Aviation Plant Less than year ago Inland was almost wholly engaged making steel for normal commercial uses. Today, quite different. Inland with the same loyal spirit shown the vast majority industry throughout the country, doing everything within its power advance the Defense Program. That why Inland rushed from its mills more than 5,000 tons steel for fabri- cation into buildings for Buick’s Airplane Motor Works Melrose Park, This enormous plant, now nearing com- pletion, will employ 10,000 workers who will machine, assemble, and test 1,000 Pratt Whitney motors month. This typical many new and urgent demands for tonnage coming Inland steadily increasing volume. Inland knows that National Defense its No. Job and its business being managed accordingly. However, after satisfying these needs aviation are, the best our ability, propor tioning our remaining steel equitably among our many customers who are engaged non-defense industries. SHEETS STRIP TIN PLATE BARS PLATES FLOOR PLATE STRUCTURALS PILING RAILS TRACK ACCESSORIES REINFORCING BARS — “ ustenite Grain Size Manipulations, and Limitations ° ARTHUR FOCKE Research Metallurgist, Diamond Chain Co., Indianapolis hos been written grain size', grain and their application any one person were take the time thoroughly study the material covered these four references, there would reason read the balance this article. However, this present emergency, many are called upon consider the grain size problem and make decisions regarding who not have this information readily available. provide such individuals with working knowledge this prob- lem the writer presented talk Size" (on which this paper based) before the Indianapolis Chapter the A.S.M. this spring. ° ETALLURGISTS clined faddish; but their fads, unlike women’s fashions, seem run ten-year cycles. Thus, the this century, the stress was applied analysis; the became ap- parent that even with the analysis rigidly controlled, significant differ- ences could obtained and the aus- tenite grain size was considered the important variable. too anticipate what the may bring forth, but the present trend toward realization that neither the analysis nor the aus- tenite grain size, separately to- gether, are completely sufficient and efforts are being made base de- cisions tests. This trend shows that metal- lurgists have progressed far enough able consider the results the previous grain size emphasis and determine, least, some measure, its proper place metal- lurgical tests Basic Working Concepts Cicero, letter his son, stated that any proper discussion series carefully planned defini- tions. Proceeding this manner: are defined individual crystals metals’ and are coherent pieces matter which all parts have the same aniso- tropic arrangement For practical purposes, can said that grain iron composed iron atoms essentially regularly ar- ° with respect each other and that the only difference be- tween individual grains that their regular arrangements are dif- ferently oriented space, that when two grains are adjacent, there discontinuity regular atomic arrangement across the boundary. The exact character the bound- ary easy argue about the classic subject whether the mor- tar between bricks holds the bricks together keeps them apart. practical working concept, the writer has found that the “amorphous grain boundary pothesis” very useful. must recognized that this concept subject many technical criti- cisms; many, fact, that Gil- lett’ states, “Few people today be- lieve the existence unori- ented layer the boundaries—the amorphous theory appears quite wrong and therefore cannot helpful.” spite this defin- ite condemnation, the writer still feels that this theory provides useful working explanation how grains grow and the following ex- planation therefore based this concept. assumed that the inter- face between the two grains, atoms THE IRON AGE, August 28, 1941—35 | 4 \ / | the surface are pulled out their regular arrangement the opposing fields force within each the grains, and therefore along the boundary these atoms are essen- tially randomly oriented and there- fore amorphous. also assumed that the force tending the atoms regularly oriented greater the larger the grain. perhaps useful consider liquid analogy. small drop mercury de- tacned from pool flat surface and then pushed back into contact with the larger pool, will always reabsorbed. case will the small drop pull additional mercury from the larger pool. most metals room tempera- ture, the atomic vibration not sufficient permit the atoms the boundary move from their dis- organized state into the lattice the larger grain. However, some higher temperature, the atomic vi- bration becomes great enough permit this movement take place and the larger grain gains the atoms from the boundary, course their place must filled with atoms pulled out the smaller grain. There are, therefore, two essentials for grain growth. First, grain size contrast. all the grains are exactly the same size growth can take place. Second, high enough temperature permit the atoms move from the boundaries into the larger grains. nature, would impossible produce all the grains exactly the same size. The usual distribu- tion sizes would probably fol- low normal distribution curve full line. Then (Case some temperature which there suf- ficient atomic mobility for all the grains the right the vertical line “A-A” start grow, there will many grains growing that none can become extremely large and the final grain size dis- tribution will perhaps shown the dotted curve Fig. However, some means, the normal movement atoms across the boundaries this temperature can restricted that only the very largest grains (those the right the vertical “B-B” Fig. can grow, and since these large grains are few number, the final grain size this temperature may very great. (Case II) Finally, (Case III) the atomic movement from the boundary can 36—THE IRON AGE, August 28, e Increasing per cent grains one siz Increasing grain size presentation grain size distribution. restricted such extent that none the grains are large enough grow this temperature, then the grain size will changed and therefore grain growth can take place. Other methods producing ex- treme amounts grain growth in- clude: (1) Temperature differences within the piece which per- mit the largest grains some section start grow while the balance the material the required temperature for any growth. (2) Cold working produce artificial grain size contrast which permits grains grow temper- atures those usually required. Critical amounts cold working may permit amounts grain growth, while only slightly lesser growth takes place. steel, the problem grain growth complicated the allo- tropic transformation iron from the body-centered alpha state Austenite grain size A.S.T.M.numbers Fracture grain size and fracture austenite grain size numbers. the face-centered gamma condition, This means that the grain struc- ture the alpha iron obliterated and replaced new set grains when the iron undergoes the trans- formation the Ac, temperature. For low carbon steels and irons used for sheets, the grain size the alpha iron ferrite, the solid solution carbon other al- loys alpha iron, which the more important. altering the ferritic grain sizes changes amounts cold working reheating temperatures and the variations these which may produced melting practices are interesting and How- ever, this article, the changes which occur the grain size the iron the gamma state aus- tenite, the solid solution carbon other alloys this gamma iron, only will treated and changes the ferrite grain size will con- sidered only the extent that such changes might affect the austenite. Measuring Austenite Grain Size Since plain carbon and alloy steels the austenite only stable high temperatures, neces- sary use some device outline the grains they existed this higher temperature when the sam- ple has transformed cooling room temperature. Several possi- ble procedures include: (1) Carburizing produce hypereutectoid zone which, slow cooling, the excess cementite will located the grain boun- daries the austenite. (2) Carburizing (1), but using the separation the ferrite the higher carbon section the hypoeutectoid zone show the austenite size. (3) above perature and cooling rate which will permit the transformation fine austenite grain boundaries, and then quenching rapid- that the greater part the grain becomes mar- tensite. (4) Heating steels cient carbon critical then quenching form martensite etching produce contrast between adjacent marten- site patches which are the size the original aus- tenite. (5) Heating eutectoid steels decarburizing atmosphere tacks the austenite grain boundaries produce either | relief etched surface outline fine pearlite when the sample quench- duce martensite the areas not decarburized. All these methods depend upon measuring the grain size micro- scopically. Various methods, such the Jeffries circle count and the Heyn intercept method, are used oc- the austenite grain size, but the more common one the A.S.T.M. method’ which the grain size determined comparing the projected image with series diagrams numbered from the coars- the average number grains per square inch magnification 100 diameters given the A.S.T.M. grain size number. this basis grain size would correspond average inch 100 diameter; while A.S.T.M. grain size would 128. This system can expanded negative numbers for very large grains numbers larger than for the very small. addition these microscopic methods, the fracture method, which depends upon cooling high enough carbon steels from above the critical fast enough produce hard marten- site and then notching and breaking the sample that the fracture fol- lows the grain boundaries the original austenite, very useful. The appearance the fracture compared with that arbitrari- numbered series standards, which standards fortunately corre- late very closely with the A.S.T.M. number series, can seen from Fig. the fracture method many cases more accurate than any the microscopic procedures because possible get im- pression the whole cross-section the fracture, while the section under the microscope may show local and cant irregularities. Also, should recognized that the cross-section prepared for examination under the microscope will not cut all the grains their major axes and therefore will always possible find few apparently small grains field. However, sev- eral small grains are clustered to- gether, would have been impos- sible have cut through large grains such way have produced this effect and, therefore, mixed grain size must exist. Limitation the Concept has become customary con- sider the austenite grain size steel “heat” characteristic and speak steel “inherently fine coarse grained.” The dic- tionary defines “inherent” exist- inseparable from and gives synonym the word When applied such steels those con- taining vanadium the high alloy tool steels, the term “inher- ently fine grain” has true signifi- sands heats. But one lot S.A.E.-3115, which specified fine grained A.S.T.M. 5-8, was re- jected when the McQuaid-Ehn test showed 1-3, and when the mill in- sisted that the same test made the billets showed 5-7, additional tests were made the coiled strip. was certainly disconcerting find that one end the coils this lot showed large 1-3 grains while the other end the same coil showed 5-7 the McQuaid-Ehn test. This peculiarity was traced the fact that this particular ship- ment was for odd part which was not made regularly and was Effect tempera- ture austenite grain size. Austenite grain size numbers 1200 1300 1400 cance, since these steels under all ordinary conditions heat treat- ment remain fine grained; but applied other grades, for exam- ple, differentiate between those killed with without aluminum, some serious discrepancies may de- velop. For instance, the Diamond Chain laboratory Ehn tests (carburize 1700 deg. for hr., cool box and compare the grain size the hypereutectoid zone with the standard A.S.T.M. charts) are run all steels for critical carburized parts, and, based this austenite grain size characteristic, only one small piece, cut from the end one the samples presented for chemical and physical tests, used. This has proved satisfactory acceptance check literally thou- 1600 1700 1800 1900 2000 deg. hot rolled from billet size nor- mally used for heavier sections. Ac- tually, standard practice these parts were reheated after carburiz- ing temperature well below 1700 deg. and the fracture grain size and physical properties these parts made from this peculiar ma- terial were normal every respect. This last statement naturally intro- duces the subject the desirability testing the austenite grain size the material one temperature treatment some other. The two curves Fig. indi- cate the general relationship be- tween the maximum temperature and the austenite grain size. The steel for which the full line has been drawn shows gradual coars- ening that the temperature increased, the austenite grains be- THE IRON AGE, August 28, 1941—37 , e n | l- r- n- S- ue IG. 4—Solubil- ity austenite grain growth in- hibiting material (After Dorn and Harder.) Austenite Increasing temperature ———> come larger and larger, while that for which the dotted line has been reproduced, which characteristic those killed with aluminum, shows very little change some critical temperature which very rapid growth occurs. Based using only one testing temperature, such 1700 deg. the Mc- Quaid-Ehn test, parts treated final temperatures lower than 1700 deg. will never show larger austenite grain size than that indi- cated the test, but the grain size may very much finer. the final temperature greater than that used the test, the austenite grain size will never finer but may very much coarser. assumed that steels which show the austenite grain size tem- perature relationship indicated the solid line Fig. fulfill the characteristics described for Case already discussed under “Basic Working Concepts,” which show the relationship indi- cated the dotted line correspond with the concepts Case II. Since this latter type austenite grain growth characteristic steels killed with aluminum, was Austenite grain size 5—Effect aging 1250 deg. austenite grain size 1750 deg. (After Dorn and Harder.) 38—THE IRON AGE, August 28, early assumed that the material ob- structing the normal grain growth was This assumption was based largely the simple analogy between the austenite grain growth characteristics these steels and the behavior tungsten contain- ing controlled amounts thorium oxide. This assumption subject several criticisms, but the work Brophy” and Mehl", who showed that alloys when carburized atmos- phere which contained oxygen were very coarse grained, while the same material carburized with the usual carbon dioxide producing compounds extremely grained, certainly and oxygen are the con- trolling elements. Dorn and suggested that this obstructing material which they called had solu- bility-temperature dicated Fig. and they were able show that the austenite grain size medium carbon steel could manipulated by: (1) Holding the steel for long periods time tem- perature corresponding position Fig. (1250 deg. F.) and then raising the temperature into the austenite zone. this case, part the phase the ferrite and this precipitated out very finely divided state when the ferrite changes aus- tenite, and this finely di- vided grain growth. treatment appears work data reproduced here Fig. (2) Heating the steel high temperature, position Fig. (2000 deg. F.), dis- solves great part the phase and the steel quenched from this high temperature, the dissolved phase will prevented tating during cooling, but will come out finely dispersed form during the reheat, and such samples when reheated will fine grained testing temperature (1700 deg. F.) [b] the sample been slowly cooled about point then the phase which had been dissolved the high temperature would pre- cipitated boundaries austenite grains formed this high temperature, and cooled room temperature and reheated the normal testing temperature (1700 deg. F.) the austenite grain size will very coarse, since the phase was not position inhibit the grain growth. The writer repeated the second part this series manipulations carburized sample X-1020, which was fine grained A.S.T.M. 7-8, after the normal test 1700 deg. and discovered that the changes reported Dorn and Harder could reproduced the hypoeutectoid zone but that the hypereutectoid zone remained fine grain. had reported similar con- dition fine grained outer case with coarse grained tion, and his explanation suggested that these steels there was excess aluminum, and that dur- ing the heating cycle enough oxy- gen diffused into the surface short distance and aluminum oxide formed before the temperature reached maximum prevented austenite grain growth the highest temperature reached while the zone below, the amount oxygen was insufficient pre- vent grain growth and large grain size quickly developed. Oxygen pene- tration continued during the car- burizing cycle and austenite grain growth inhibiting material was formed. Such material powerless refine the large austenite grains already formed, but the same sample cooled below the critical and reheated completely grained case should developed, since the austenite grain growth in- hibiting material can now act. This observation was confirmed the writer the fine grained X-1020 1700 deg. discussed above. After carburizing 1850 deg. for hr., the hypereutectoid zone showed austenite grain size A.S.T.M. 7-8, while the hypoeutec- ° toid zone was 1-2. duplicate sample quenched after carburiz- ing showed about 0.020 in. fine grained A.S.T.M. 7-8, while the rest the 0.080 in. total case was very coarse, about 1-3. After reheating this water quenched sample 1850 deg. for hr., the entire case was fine grain, A.S.T.M. 7-8. had shown that the could affected changes pre- liminary treatments. his results terms the number coarse grains present after car- burizing various temperatures and assumed that the greater the number coarse grains per cent, the lower the temperature which grain growth started. Fig. taken from his work, illustrates the effect prior heat treatment and can seen that normalizing before carburizing drastically low- ered the temperature grain coarsening. Fig. which was also taken from this work, shows the effect increasing amounts hot working and course clear that steel can exhibit various austenite grain sizes when burized high temperatures, de- pending upon the amount pre- vious hot work. The peculiar result the coiled S.A.E.-3115 which one end was coarse and the other fine, considered further evi- dence that relatively small changes the processing the steel the mill may produce significant aus- tenite grain size differences. Schempp and Shapiro” showed the effect various treatments the grain size produced carburiz- ing eutectoid tool steels, haps their most interesting result was that critical amounts cold working could lower the tempera- ture austenite grain growth suf- ficiently permit large austenite grains form the normal Quaid-Ehn temperature. The writer has never been able reproduce their results the carburizing grades steel. fact, recent series tests different lots, which included annealed plain car- bon and nickel cast steel, S.A.E.- 1020 plates, and X-1020, and open hearth free machining burizing grade rounds, with aus- tenite grain sizes the normal McQuaid-Ehn treatments ranging from coarse 1-3 fine 7-8, the aus- tenite grain size the base sides Brinell impression was essen- tially the same that found the cut edges the samples. Ar r IG. ence prior heat treatment the coarsen- Per cent coarse grains ing temperature. and more recently, Rosenberg and have stud- ied the effect the rate heating through the critical range the grain growth the austenite. They found that changing the rate heating did produce differences, but the direction the change varied with the material. With pure iron-carbon alloys, containing 0.50 the grain size tempera- tures 1600 deg. increased with decrease rate heating; whereas the grain size 1800 deg. was less noticeably dependent upon the heating rate. 1475 deg. the austenite grain size com- mercial steels containing 0.49 per cent carbon tended increase with increase rate heating heats which had been treated control the grain size well those which were non-controlled, but 1650 deg. and 1800 deg. only the aus- tenite grain size the uncontrolled steels was affected. The writer was unable find significant differences the nor- mal McQuaid-Ehn results burizing steels between samples packed cold compound cold box and those added after the box and compound had reached 1700 S increasing amounts hot working the coarsening tem- perature. Qa ° ° 1600 Carburizing 1800 Carburizing deg. Grossman) 1900 2000 2100 deg. With the size samples used, the differences between the heating rate were the order 60-100 but these results not alter the conclusion Rosenberg and Digges that consideration must given the possible effects that rate heating through the trans- formation range may have upon the austenite grain size steel. difficult explain the mech- anism which all these variations the austenite grain size can produced these manipulations except assume that these treat- ments have varied the amount distribution the inhibiting mate- rial which probably but should apparent that the term “inherent” applied the aus- tenite grain size these steels has only limited significance. Also, should clear why not possible desirable specify the austenite grain size more closely than the restrictions listed the American Iron and Steel Institute” which follows: “Limited austenite grain size re- fers specifying restricted range grain size numbers. Manufactur- ing practice limits such restric- Grossman) 1900 2000 THE IRON AGE, August 28, 1941—39 Furnace 100 TABLE Effects Austenite Grain Size Applications which austenite grain size has been found very important: [A] hardened and tempered state: (a) Toughness relatively high (b) Hardenability (depth hardened zone) (c) Hardenability from soft spots) Distortion ........ Internal stress ............ (f) Austenitic retention (a) Machinability (rough) A.S.T.M. Grain Size Coarse, Fine, 5-8 lower higher greater lower better poorer greater lower greater lower better poorer higher lower Applications which austenite grain size may important some special cases: [A] annealed normalized condition: (a) Machinability (fine (b) Blanking inferior superior moreirregular burrs Rate cold working more rapid less rapid Creep resistance: lowest temperatures inferior superior highest temperatures. superior inferior [B] austenitic state: Applications which austenitic grain size may considered unimportant: [A] hardened and tempered state: Maximum hardness (assuming that there direct transformation fine pearlite nor any retained austenite). Resistance fatigue. Toughness relatively low hardness. tion the following conditions: The specified range shall include not less than three consecutive numbers either end the series, for example, tical control grain size the The grain structure con- sidered satisfactory per cent within the specified grain size limits.” Effects Austenite Grain Size Grain size has been shown important some cases that probably every phase the prob- lem the use metals has been investigated determine the sig- nificance this variable. general way Table based summaries Ward and and probably repre- sents the present state knowledge about the effects austenite grain size. Such tables give only rough com- parisons and for many purposes would necessary have more definite data before would pos- sible make definite tions attempt include austenite grain size the specifications for the steel for any part. 40—THE IRON AGE, August 28, Unfortunately, such quantitative data are not readily available might expected and the discus- sions presented next week simply amplify some the main points Table References 1A.S.T.M. Standards 1939, Part Metals: (a) “Preparation Micro- graphs Metals and Alloys,” pp. 1216-1217 (E2-39 T); (b) “Austenite Grain Size Steels,” pp. 1175-1177 T). The Science Metals, Jeffries and Archer: (a) “The Amorphous Metal Hypothesis,” Chapter IV, 63; (b) “Grain Growth and Chapter 85. National Metals Handbook, A.S.M., 1939 Edition: (a) “Austenitic Grain Size Steel,” Bain and Billela, 754; (b) “The McQuaid-Ehn Test,” McQuaid, 750; (c) “The Use Aluminum for Control Grain Size *“Crain Size Steel—A Critical Review,” Ward and Dorn, Metals and Alloys, vol. 10, 1939, 74, 115, 212, 246. National Metals Handbook, 1939 Edition, National Metals Handbook, A.S.M., 1939 Edition, 12. “Some Things Don’t Know About the Creep Metals,” Gil- lett; Transactions A.I.M.E., 1939, 30-31. Growth Sheet Steels during Box Samuels; Transactions A.I.M.E., vol. 131, 1938, 327. Effect Type Cold De- formation Properties Armco Iron,” Kaiser and Taylor; Transactions vol. 27, 1939, 227. Normality Steel,” Brophy and Parker; Transactions A.S.M., vol. 25, 325. Factors Influencing Aus- tenite Grain Size High Purity Steels,” Mehl, al.; A.S.M., vol. 26, 1938, Steels Austenite Grain Growth,” Dorn and Harder, Transactions vol. 26, 1938, 106. “General Relations Between Grain Size and Hardenability and Normality Steels,” Davenport and Bain, Transactions A.S.M., vol. 22, 1934, 879. (Grain Size Symposium). “Crain Size Metals with Special Reference Grain Growth Austen- Grossmann, Transactions A.S.M., vol. 22, 861. (Grain Size Symposium). Influencing Grain Size Determined Standard Methods,” and Shapiro, Transac- tions A.I.M.E., vol. 125, 1937, 411. Through the Range Austenite Grain Rosen- berg and Digges, A.S.M., 1940 Pre- print No. 12. Steel Products Manual—Standard Chemical Compositions, ete. for Car- bon Steels, American Iron and Steel Institute, May, 1941, Unpublished talk grain size steel, delivered Stagg the Canadian May, 1940. (To continued next week) UCCESSFUL cold forging com plicated contact fingers from copper bar stock ina single die form- ing operation now being performed with the aid dry lubricating part- ing compound. Seizing the copper the die and normally high die wear eliminated dipping the copper slugs Oildag type colloidal graphite suspended oil, thereby forming graphoid surface the part and preventing metal-to-metal contact the die and consequent pick-up and sticking. Magnetic Testing Simplified Electric Co., Schenectady manent records cracks, seams, and other defects re- vealed forgings, shaftings, and tools means magnetic testing. Heretofore, the most satisfactory method recording these defects has been photograph the defec- tive part, illustrated Fig. However, considerable item re- quired provide background sufficiently contrasting make the defect visible. often desirable make per- new, quick and inexpensive method making equally good even better records these defects has been developed the labora- tories General Electric Co., Schenectady, When defect located the usual magnetic testing transparent, gummed cellulose tape applied, gummed side down, over the defect. This tape then removed and mounted white cardboard. Some the magnetite outlining even the smallest part the defect adheres the gummed surface the tape, and, when sealed against card, forms durable and perma- nent record, shown Fig. more than one record de- sired, the original tape, mounted the cardboard can photographed, or, mounted glass other transparent material, can silverplated. The method has various applications, among others being the recording mag- netic field strengths and patterns. photographic reproduction steel part showing the cracks disclosed magnetic testing. IG. 2—Magnetite, adhering the strip gummed cellulose tape, plainly outlines the crack defective metal German Manual Wire Technology the Carnegie Institute Technology, the first book series small manuals well cir- cumscribed subjects, published Stahleisen (the German Iron and Steel Institute) German, has just been received. This book, de- voted the subject steel wire, entitled Stahldraht, Pomp, and published Stahleisen, Dus- seldorf, Germany. The book begins with properties the hot rolled rod and ends with testing the finished wire. All inter- mediate stages and processes are described detail. The book happy mixture sound theory and advanced practice, far the lat- ter has been released for publica- tion. may remarked that Dr. Pomp the outstanding German authority the theory wire drawing. Those readers who are exceed- ingly well versed the manufac- ture steel wire may possibly miss information extremely spe- cialized details here and there, but the average reader will find his every question answered gards theory, engineering, metal- lurgy and operation pickling, drawing, annealing, patenting, hardening, coating and testing. The book can imported through any dealer foreign books such THE IRON AGE, August 28, * & | | OPTICAL FLATS PTICAL flats have become in- dispensable industry for gaging the surfaces parts used oil seals, compressor thrust washers and many other machined parts, and the growing importance surface finish modern preci- sion work has brought increasing demand for wider application. Ex- tensive study, notably the Mid- West Abrasive Co., Detroit, has been devoted the development method for obtaining optically flat metal surfaces mass-pro- duction basis. With perfection this method, discussion the characteristics optical flats and some the problems involved their production timely. JACKSON Mid-West Abrasive Co., Detroit Modern precision work requires dimensional accuracy millionths inch. For measuring surface flatness that degree accuracy, the principles light waves and light wave interference are used. The equipment for making these measurements optical flat, and source light preferably monochromatic (light one wave length color). typical optical flat disk, 42—THE IRON AGE, August 28, OPTICAL FLAT about in. thick and in. diameter. For flatness need have only one plane face which, for average commercial use, working flat 0.000001- in. accuracy. For checking height spacing parts, both faces must and the thickness accurate with- plus minus 0.00001 in. Checking Surface Flatness checking the flatness sur- face, the optical flat lightly slid over the surface from the side placed directly the surface and tapped lightly, taking care keep the surface free foreign matter. illustrated the exaggerated drawing Fig. incoming rays light, and from source passing through the optical flat are partially reflected its own sur- face, and and partially the surface the work, and these two surfaces are separated minute film air, the rays and must travel farther than tween the two surfaces, and they will therefore lag slightly behind. rays light travel waves, this causes the two reflected wave trains shifted slightly length- wise each other. If, and the two reflected wave trains are out phase, that is, the waves wt A i i J O PHASE OPTICAL FLAT FIG. Mass Production oppose those q', they produce and the two reflected wave trains are phase, match and reinforce each other, they produce band light The spacing between these bands represents height dif- ference between the two surfaces half wave length the light used. With daylight the light source, the bands contain all colors the spectrum, for sharper band pattern and more accurate reading, monochromatic preferred. Krypton gas mercury 0.000012 in., while sodium vapor light permits readings accurate 0.000006 in. The pattern formed these in- terference bands indicates the ex- tent and direction any deviation the surface the work from true flatness. the bands are straight and evenly spaced, shown Fig. the surface flat. the surfaces should contact with- about 0.000003 in. and both are accurate flats, instead series bands the entire area will show solid gray color. Figs. and show other typical band patterns and exaggerated drawings the deviations from flatness which they indicate. Fig. the depression the surface the work indi- OPTICAL FLAT FIG. —Elimination hand lapping operations making opti- cal flats has effected considerable savings their pro- duction time and cost, thus making the manufacture these surface gages practical for general industrial production. cated the bands becoming nar- rower and closer togethey and the appearance additional bands over the center the depression. Fig. the bands become narrower and curve closer together the sur- face the work falls away from the high center. Fig. the sur- face the work gives straight and evenly spaced bands over the larger portion which flat, the bands narrowing and the curving closer together over which curves away. Making Optical Flats Optically flat surfaces have been used automotive and airplane precision parts for some time but the chief drawback their more extensive industrial use has been For articles selection and grading abrasives and superfinishing, see THE and July 11, 1940. OPTICAL FLAT the time and skilled labor required produce them. The piece ground. This machine opera- tion and the time required deter- mined the area ground. The second operation finish grind which produces surface that flat and smooth within correc- tion about microinches r.m.s. The final finishing consists series lapping operations which have been done largely hand. Even when lapping machines were used, the final operation was still hand. Hand lapping slow and highly skilled operation. The work rotated cast iron lapping blocks with abrasives varying degrees fineness and hardness. Where fine precision was required, hand lapping resolves itself into several operations, each employing abrasive increasing fineness. spite the time and high degree skill involved and the re- OPTICAL FLAT WORK FIG. THE IRON AGE, August 28, 1941—43 | ° ° | WORK sulting high production cost, the advantages optically flat surfaces have proved sufficient justify their limited use. The desire ob- tain such surfaces mass-pro- duction basis and thus extend their application many parts where the high production cost made them prohibitive led intensive study the problems involved. Experimental work with differ- ent types abrasives was under- taken the Mid-West Abrasive Co., some time ago, with view eliminating all hand lapping opera- tions. From experiment soon be- came apparent that the solution lay bonding agent. With the bonding agents then use, the abrasive Corrosion URING discussion between Taylerson, when the former was visiting this country, the sugges- tion was made that would interesting compare corrosion rates steels the with those obtained the various ex- posure stations the Corrosion Committee (English). 1931 sev- eral specimens the committee’s steels, and were received from Dr. Hudson, the commit- tee’s official investigator. that time Mr. Taylerson’s company started extensive in- vestigation large number other materials, that was pos- sible include the British steels exposure tests three locations— industrial marine atmosphere (Kearny, J.); industrial at- mosphere (Vandergrift, and rural atmosphere (South Bend, Pa.). While these tests were in- tended supply information for the commercial development low- alloy steels, the results for num- ber the American materials have been included matter gen- Taylerson, presented recently the Iron and Steel Institute (Brit- ish). The chemical compositions the materials are covered the accom- panying table. Also, graphs show- ing the corrosion rates the one area—industrial marine atmosphere are given herein. The results 44—THE IRON AGE, August 28, stone disk was “hard” enough retain the abrasive grains firmly, thus reducing wear and assuring that the stone would stay flat, the tendency “load up” and stop cut- ting became great. the bond fracture rate was increased suffi- ciently make the stone self-clean- ing, then the grits would tear away unevenly, spoiling the flatness the stone and, consequently, the work. The search for bonding agent that would allow the stone self-cleaning and still wear evenly led the development Micro- Bond. Being high capillarity, each grain completely insulated and supported, adherence two more grains impossible, and illustrate the great influence cop- per and the even greater protective even grain structure maintained. The grain structure remaining uni- form, even wearing and precision flatness assured. Using stones made with Micro- Bond, surface finish two micro- inches r.m.s. obtained mini- mum contact time directly from microinch ground finish. All hand lapping operations are eliminated with consequent tremen- dous saving time and cost, and the manufacture optical flats for general industrial production work made practical. Flats obtained this method have perfect surface that, when two are pressed together they will adhere manner similar the action gage blocks. Resistance and Steels value higher percentages al- loying elements. per sq. in. exposed t,gm. Loss weig Bessemer steel Time, years Results atmospheric corrosion tests Kearny, atmosphere). Chemical Analysis the Materials Mn, Per Per Material Cent Cent stee! (0.03 per cent Cu) 0.18 0.61 steel (9.26 per cent Cu) 0.19 0.60 Committee’s steel (0.54 per cent Cu) 0.20 0.62 pollution specimens (ingotiron) 0.02 0.05 Experimental heat, low and 0.015 0.02 Experimental heat, medium Mn, low Cu. 0.040 0.24 Open-hearth iron, very low 0.018 0.025 Steel (0.05 per cent Cu) 0.040 0.49 Wrought iron (0.29 per cent Cu) 0.018 0.095 Steel (0.27 per cent Cu) 0.026 0.47 Bessemer steel (0.5 per cent Cu) 0.10 0.40 3.5 per cent steel 0.043 0.46 Cr-Si-Cu Steel 0.11 0.62 Si, Cu, Ni, Cr, Per Per Per Per Per Per Cent Cent Cent Cent Cent Cent 0.041 0.043 0.008 0.03 0.05 0.04 0.040 0.043 0.009 0.26 0.05 0.05 0.038 0.043 0.010 0.54 0.05 0.05 0.013 0.044 0.008 0.07 0.05 0.001 0.004 0.038 0.004 0.02 0.006 0.003 0.062 0.032 0.008 0.01 0.007 0.005 0.019 0.002 0.008 0.002 0.01 0.074 0.042 0.003 0.05 0.006 0.09 0.096 0.028 0.14 0.29 0.006 0.066 0.045 0.003 0.27 0.03 0.03 0.107 0.057 0.007 0.52 0.002 0.02 0.014 0.027 0.004 0.06 3.52 0.16 0.012 1.25 1.03 0.07 3.88 |_| < Cu) marine ° ° CORSON Metallurgical Consultant, New York WELVE years ago this author was investigating the nature iron-silicon alloys. During that research co-worker took number micrographs the al- loys the strictly binary well the ternary series—the latter containing about 0.8 carbon. Among the micrographs were some which did show rather strange markings which looked like wide open barley shells. These markings might definitely identified analogous the needles marten- site were not for the fact that their location had little common with the granular structure the metal. large number them crossed the grain boundaries from one grain into another, while those that stayed within the individual grains were strewn around most irregular manner. (At that time was still believed that mar- tensitic needles possessed definite orientation reference the orig- inal austenite Time passed and iron-silicon al- loys were examined again and again other researchers and some them claimed that these markings had real existence. What were they? Oh, just some etching effects. This expression “mere etching effects” used too frequently some metallographers order brush aside problem which they cannot solve. But, last week there etching effect, matter how queer, which not con- nected intimately loosely with the state the surface etched. Etching effects are constitutional features, and those markings re- produced here Figs. pos- sessed the following specific char- acteristics: (1) They never appeared al- loys with less than nor more than Etching Technique continuation last week's discussion the theory etching and the application ferric solutions the etching nickel and its alloys. Herein attention directed using the same solution for copper alloys; also, certain "strange structures" are noted, i.e. structures that not exactly conform the over- simplified ideas prevalent among metallographers. per cent silicon. (See Figs. (2) They were most frequent the range per cent silicon. (3) They were particularly dense samples that were quenched from about 1000 deg. (5) They could not elimini- nated rubbing off polishing wheel the absence alumina. (6) They did not take place the presence higher amounts carbon. (7) The starting point group such barley shell mark- ings always carried small but definite particle usually square shape, that the structure might have represented cracks heavy plate glass that had been hit with already mentioned, the barley shell markings did not take place the presence carbon. The lat- ter formed sort eutectic very much like graphite cast iron when the alloy was sand cast. The chill cast alloys looked quite differ- ent. They also carried graph- ite (?) eutectic, but its granules were quite round and the general appearance was not unlike that copper-copper monoxide silver- copper, the modified aluminum- silicon eutectic. (See Figs. and 8.) course these two types structure were not particularly un- usual and could explained variations the speed. However, there was also appearing usually with slightly lower carbon contents. it, the carbon phase formed thin, sharp lines running three definite di- rections within individual grain. (See Fig. 9.) Those who believe that naming thing means explaining might satisfied saying: “just case Widmanstaettens.” This author neither inclined accept such explanation nor yet proffer one his own. The fact merely men- tioned that carbon iron-silicon alloys may take three shapes lamellar graphite, globular graph- ite, and sharp linear graphite, the latter forming the “queer” feature, just the barley shell markings form queer feature binary iron-silicon alloys tween and per cent silicon. And, would worth the while any metallographer study these queer features detail instead dismissing them with shrug the shoulders. The case per cent copper- silicon Another case queer structures was observed 1925 while working copper-silicon al- loys. (Figs. and 11.) was found then (and reported paper) that alloys containing per cent silicon behave rather pe- culiar manner. Quenched from any temperature above 600 deg. they THE IRON AGE, August 28, | H | ings. ings. as-cast. rains 100 con alloy with Shows but marki shell" con alloy with per cent Si, as- cast tion 100 diameters. IG. IG. per cent Si, Columnar with but few ley mark 100 diameters. tate, but “barley markings. diameters. precipi c c 100 an- and quenched. The structure ters. silicon alloy 100 diameters. markings. diame per cent Si, as-cast. shell" looks decidedly sitic. nealed 1000 deg Shows big brushes 1 5 < O5265 om wi a 2 4 PA © = © o 2 . ~ Md ‘4 * 4 2 4 ey - | ‘ slowly cooled the furnace. Ex- CuBe system. with per cent Be. treme striation along the crystal- line planes intimate com- bination the alpha and kappa phases. and slightly overaged compound. culiar striation dismissed them “just case multiple twinning.” were composed grains that were heavily but not excessively marked with fine parallel lines. Furnace without the subterfuge just giv- ing some proper name. Not having some the fine tools When strange structures are not cooled they possessed grains that were completely striated and this three definite directions. the first state they were soft and ductile, the second hard and brittle, while the ultimate strength was exactly the same. Pictures published this author passed quite unnoticed. The high- est metallurgical “authorities” with whom conferred about this pe- metallurgy hand (dilatometry, X-rays, etc.) the author paid little additional attention the striated grains per cent cupro-silicon until, 1938, two researchers, Drs. Smith and Anderson, reported the finding new phase—the kappa, which forms fine hexagonal plates between the layers the alpha phase. finally one the strange structures