The Iron Age 1945-10-25: Vol 156 Iss 17

price may VAN DEVENTER President and Editorial BAUR Vice-President General Manager LEONARD Assistant Manager HAYES Advertising Manager JOHNSON, Manager Reader Service and Market BAUR, Production Manager CLEARY, Technical Research and Promotion Manager Executive Offices Chestnut and Sts. Philadelphia 39, Pa., U.S.A. Editorial and Advertising Offices 100 East 42nd New York ° ° Regional Business Managers OBER LEONARD New York New York 100 East 42nd St. 100 East 42nd St. Cleveland Pittsburgh 1016 Guardian Bidg. Park Bidg. Philadelphia Chilton Bidg. 1134 Otis Bidg. Detroit Hartford Conn. 7310 Woodward Ave, Box RAYMOND KAY Los Angeles 2420 Cheremoya Ave. ° ° ° Owned and Published CHILTON COMPANY OFFICERS AND DIRECTORS MUSSELMAN, JOS. HILDRETH, President GEORGE GRIFFITHS Vice-President EVERIT TERHUNE Vice-President VAN DEVENTER Vice-President BAUR Vice-President Vice-President JULIAN CHASE Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR Secretary BUZBY HARRY DUFFY THOMAS KANE CHARLES HEALE WILLIAM Asst. Treas. ° Editorial Board PAUL WOOTON Washington Representative Member, Audit Bureau Circulation Member, Associated Business Papers indexed the Arts Index. Pub- lished every Thursday. Subscription Price North America, South America and Possessions, $8; Foreign, per Copy, ° AGE Vol. 156, No. Editorial Social Security for Employers Technical Articles Retained Austinate and Carbide Segregation Sectional Carbide Gas Carburizing (Part Spot Welding Machines Assessing Wear Due Friction and Corrosion Automatic Operation Vertical Turret Lathes Electric Furnace Atmospheres New Equipment Features News Front Assembly Line Washington West Coast Personals and Dear Editor This Industrial Week News Industry News and Markets Krug Reports Wartime Steel Data Smith Develops Glass Lined Silo Ohio Compensation Rules Use Statistics for Metallurgical Data Urge Management Aid for Small Business Latest Weapons Shown Wright Field Metal Aircraft Hangars Machine Tool Market Developments Nonferrous Market News and Prices Iron and Steel Scrap News and Prices Comparison Prices Week and Year Finished and Semifinished Steel Prices Alloy Steel Prices Fabricated Steel Products Prices Warehouse Steel and Pig Iron Prices Ferroalloy Prices Index Advertisers October 25, 1945 107 146 147 148 149 151 152 108 110 112 114 116 117 118 119 120 227-28 | zes yme sed osts ince in- ° HALF: EVERAL years ago, Pittsburgh electrical manufacturing plant, disc ‘‘cookie’’ die was placed operation. was made Firth- newest, original, sintered carbide develop- ment for blanking dies. This die blanked circle silicon electrical sheet .025 inch thick, used rotors and stators. proved successful that since then two other similar Diecarb dies have been put work—all averaging million blanks per grind, compared with 90,000 pieces per grind with high speed steel dies. GET TOUCH WITH complete Diecarb engineering service your call—for designing complete dies; for aiding application Diecarb die shoes brazing; shrink-fitting; press fitting and mechanical matrix; and for proper grinding. 42—THE IRON AGE, October 25, 1945 dies The original die, the latest count, had pro- duced the unprecedented over half billion stampings, and was still going! fact, the life these remarkable Diecarb dies not yet determined because all dies far made are still use. Diecarb can used for blanking and forming diversity materials including metals, plastics, paper, etc. operates successfully thicknesses 7/16 inch. proving unmatchable for high production operations, saving both downtime and maintenance. you have product that requires blanking you are planning Firth-Sterling now test the possibilities Diecarb. STEEL COMPANY OFFICES: McKEESPORT, PA. NEW YORK HARTFORD PHILADELPHIA PITTSBURGH CLEVELAND DAYTON DETROIT CHICAGO LOS ANGELES ESTABLISHED 1855 October 25, 1945 VAN DEVENTER and Director BAUR Vice-President and General Manager Editorial News-Markets Editor CAMPBELL Machine Editor...H. LINSLEY Associate JACK HIGHT WINTERS ALBIN JOHN ANTHONY BARMASEL ERNEST Editorial Assistants SPEAR Foreign Editors Canadian (Contrib.) Sanderson News and Technical Editors LLOYD Pittsburgh 428 Park Bidg. POST Chitago Otis EUGENE HARDY ANSBORO Washington National Press Bidg. LLOYD Cleveland 1016 Guardian Bidg. BRAMS DETROIT 7310 Woodward Ave. OSGOOD MURDOCK WORTH HALE San Francisco 1355 Market St. Editorial Correspondents ROBERT Cincinnati DEAN Buffalo FRAZAR Boston HUGH SHARP Milwaukee RAYMOND KAY Los Angeles JOHN McCUNE Birmingham ROY EDMONDS St. JAMES DOUGLAS Social Security for Employers SECURITY” one those resounding terms which are popular today because they can mean almost anything that those who hear read them want them mean. They are not handi- capped definition but are elastic and can stretched encompass any given amount votes. Since not definable, what may take mean may not coincide with your interpretation, which quite all right because variety the spice life opinion other matters. What take mean the endeavor alleviate eliminate certain risks for certain people, primarily our wage earners. Certainly legislation, effect and pro- posed, has this motivation. aimed establishing protection for the worker his job, his wages, his dealings with the boss, (not including his union boss, course) and him far possible for unemployment and for old age. the latter, must fairness said that the employer, payroll, comes for his share pension protection. Before the meaning the term has jelled and while still elastic, think would good idea consider taking social security out its class conscious construction and stretching admit the em- ployer its other benefits also. Certainly the present-day employer who makes jobs, tries to, and who pays wages encounters plenty occupational hazards. One particular the hazard met him today keeping his plant open for business the face wildcat believe that most employers are willing accept the principle collective bargaining. What they object and what they need pro- tection from and have not that after the bargain made and the instrument sealing signed and delivered, one party can toss overboard nonchalantly you would toss cigar butt from ferry boat. Under the present one-sided and strictly class legislation that exempts labor from the due processes law regards the observation contracts, the only safeguard against unsocial insecurity for the em- ployer the caliber and character the union leadership with which negotiates and agrees. Mind you, there are good unions that live their contracts. Such unions and their membership have nothing lose and much gain. state where other unions compelled equally scrupulous the observance their Damage wildcat strikes not confined the men striking the company struck. Irresponsible action comparatively few can and has caused widespread loss time, wages and company earnings even remote from the source. permit such action the antithesis social security any sense. Top union leadership, however well intentioned, has demonstrated its inability control these epidemics. But there are plenty laws already the statute books providing recourse for contract violation. Removing the exemption such laws now favoring labor unions and putting all Americans equal footing this respect would long way toward curing this particular trouble. SCHIEN CAMP MUNZER SCHIMKO ion Steelmakers Confer With Metallurgists... every order...at Inland Bars When Inland metallurgist away from his office—and that may large part each day—he can superintendent’s office talking proc- esses, may open hearth furnace following through heat, may mill laboratory getting record physical tests. This close cooperation between steelmakers and metallurgists important factor producing qual- ity steel, improving processing methods, and meeting the exact requirements each Inland cus- tomer. Inland Steel Company, Dearborn St., Chicago Floor Plate Piling Plates Rails Reinforcing Bars Sheets Strip Structurals Tin Plate Track Accessories Sales Offices: Cincinnati Detroit Indianapolis Kansas City Metallurgists and steel- makers review all orders that enter the Inland mill. There suppli advant holdin the qual the The Jones ars. Prod ool mar housand arrel News Front Reconversion the automobile industry practically complete now, with current production rate 1400 passenger cars and 750 trucks day. Barring najor production should exceed 6000 units per work day. Packard redesign includes coil spring expanded piston ring designed for uniform radial pressure the cylinder wall and avoid oil slot clogging. There also new steering gear arrangement and new type crankcase bearing material. OPA has invited steel warehousers apply for increases price ceilings cover increased costs incurred enforced buying from other than customary suppliers and subsequent fabrication for customers' requirements. controls for tools will replace the prewar nechanisms involving levers, screw adjustments balance springs. Among other advantages, this development will permit forcing implements into the ground and holding them there desired depths despite variation soil conditions. The industry going far West Coast aircraft suppliers for design and production hydraulic mechanisms. New models tractors are designed for the elimination dead weight using welded construction for frames and housings. Better traction afforded rubber tires makes this possible. heat 320 pct, can obtained using spot welding machine its ninimum throat against maximum throat. Tests determine what extent the secondary current spot welder affected various conditions the secondary loop also disclosed that constant throat opening and throat depth needlessly limited the current obtainable from the machine and wasted electrical power when the opening was very much larger than necessary. Before making tools from high-speed steel, inspection longitudinal sections the Magnaflux method provides rapid and accurate indication quality. Extensive Magnaflux indications segregation and austenitic retention, definite effect, definitely affects tool life. Use sectional carbide nib molds the Steel Pa., facilitates recutting, thus limiting the life the mold only the amount stock which removed. addition being recut original sectional nib mold also may recut large sizes within the limits the nib diameter. The addition line alloy steel cold finished bars will likely made Jones Laughlin Steel Corp. its already complete line carbon steel ars. expected purchase alloy bars and cold draw not expected that the company will any alloy lines present. Production has cast premonitory shadows the machine market. Still the design stage, aluminum hood tops and rear deck are said seriously under consideration. Production appears from eight twelve months away. Then according rival manufacturers, shift from Willow Run The Germans perfected method producing high-grade iron powder directly liquid metal machine very simple design. Output ran into the housands tons, great quantities being used for sintered iron rotating bands shells which performed better and actually gave much longer arrel life than the copper rotating bands conventionally used. experiments with sintered rotating bands were dropped after test ‘disclosed drastic reduction gun barrel life. simple German powdering machine turned out large quantities all and ferrous powdered metals. - Oct. 23, 1945 Magnetic Particle Detection Retained Austenite and examination tools, welds and aircraft parts are some the most popular present day applications the magnetic particle inspection method This nondestructive test carried out making use continuous and residual magnetic fields that can created ferromagnetic materials. Application the magnetized piece fine iron particles the form wet sus- pension dry powder gives pattern indications. The defects found this method are generally classified cracks, laps, slag, and lack metal fusion. However, the author herein will discuss Magnafiux indica- tions resulting from carbide segrega- tion and retained austenite high- speed tool steel and not patterns due the aforementioned defects. During the examination high- speed tools particle methods, build-ups were noticed near the horizontal axes the tools. This was particularly evident large reamers and counterbores, the shanks which tapered sufficiently expose view boring tool showing magnetic particle indications segregation and retained austenite the transverse section. Actual size. 46—THE IRON AGE, October 25, 1945 the original bar-stock centers, and also the transverse section the boring tool pictured fig. The magnetic particle indications seemed unaccountable, for cracks were disclosed upon closer examina- tion. The frequency occurrence the observed phenomena justified further investigations. The tool steel under investigation had the following range analysis: Pet Carbon 0.76 0.82 Chromium 3.60 4.10 Tungsten 1.40 2.00 Vanadium 0.95 1.25 Molybdenum 8.00 9.00 tool steel this type, austenite that formed during heat treatment, and carbide segregates, will always present. The distribution the segregates within the bar stock de- pendent upon mill practice casting and reducing the original ingot.’ The most desirable steel bars will have only small amounts carbide string- ers the center. the annealed condition the non- magnetic carbide stringers are dis- tributed matrix ferrite and The segregation has banded appearance and will relatively the same nature after heat treatment. The matrix sufficiently magnetic while continuous high cur- rent passing through attract fine iron particles. Microscopic examination 100 heat-treated specimen etched with nital, reveals white stringers and background tem- pered martensite. The tempered mar- tensitic areas have magnetic proper- ties. Under the influence elec- tric current flowing continuously, the martensite develops magnetic field, and current strong enough, resi- dual magnetism set up. small amount austenite re- tained even correctly hardened and tempered pieces. nonmagnetic constituent,’ and the same manner segregates, interrupts the mag- netic fields the matrix. Multiple tempe break Howe phase states, magnet interru (the These served Test bar taken Anne: conditio were ton whe were metallog tra) which low volt used. magneti: solenoid specimen tract tinuity. effected flow thro tudinal had the elon; get maxi transvers rent flow found alloy res) a Jam Tungst a t ~ 3 =. | a q j | | tempering operations will further break down the remaining austenite. However, areas heavy carbide segregation, doubtfal this phase can further transformed additional heat treatments—the high alloy concentrations are too sluggish respond normal manner. Gill, “Tool Steels,” 114. Tungsten,” pp. 95-136. pp. 284-332. the annealed and hardened states, leakage fields are created when suitable electric current passed through the steel containing non- magnetic constituents. When fine iron particles are applied, they gather interruptions the magnetic field (the austenite and segregation). These are the powder patterns ob- served the areas under examina- tion. specimens were taken from bar stock used making boring-tools. Transverse test pieces measured in., and longitudinal ones taken the center the bar were in. Annealed, the hardness was 100R,; the hardened and tempered were ground with 36-05 Nor- ton wheel; after which, some pieces were given final high polish for metallographic examination. transfer equipment) which provides high amperage and low voltage alternating current was used. First, the pieces were de- magnetized withdrawing from solenoid using 2500 amp. The test specimens showed tendency at- tract iron filings areas discon- Next, magnetization was effected allowing the current flow through the pieces. the longi-- tudinal specimens the current flow had the same direction the elongated carbide segregates get maximum field strengths; the transverse pieces the direction cur- rent flow was not important. was found necessary use higher cur- RICHARD DOOLEY Newport, Before making tools from high-speed inspection tudinal sections the wet-continuous method provides rapid and accurate indication quality. The author herein shows how segregations and areas with retained austenite are found this method. rent densities than the general practice for locating cracks. Both the “continuous” and “residual methods” inspection were used. the test piece placed between the heads the machine and the current flows through while the medium* applied, the method called con- tinuous. The duration continuous current was simultaneous application medium was sec. the residual *The medium used was red iron paste developed Magnaflux Corp. dis- solved Ultrasene (Atlantic Refining Co.) the recommended proportions method the piece magnetized current flow sec, removed from the heads and immersed the medium for sec. After the powder patterns were formed, rinse clear Ultra- sene was used remove excess par- ticles held surface tension. Table shows magnetic particle indications segregation obtained annealed pieces. The data obtained strength in- dications segregation and austenite heat-treated specimens are shown table II. From table evident that the continuous method must used with the annealed stock order obtain the desired indications. Powder pat- 2—Segregation and austenite found tool. Original tion 250X. pct wo, a ond 4 4s a — n- ¥ re- and etic iple THE IRON October 25, 3—Magnetic particle indications the same area fig. terns equal strength can ob- tained the heat-treated specimens using lower amperage and the same technique. This possible be- cause after hardening, the matrix martensite has greater retained field strength than the matrix the an- nealed steel. Magnetic particle indications segregation observed longitudinal section are more pronounced than transverse. The elongated carbide stringers have much greater area exposed when viewed lengthwise; therefore, interruptions the mag- netic field are more numerous and powder patterns are more easily formed. Surface conditions play impor- tant part obtaining proper mag- netic particle saw-cut surface either transverse longitudinal section, clinging par- ticles could found the segre- gated areas. polishing No. emery paper surface grinding with Norton wheel, in- dications were strong and easily de- termined. finished tools have fine polish and offer better conditions for testing. Local poles have tendency formed during magnetic inspection with high current densities the contact areas are not large When using the “wet-continuous pro- cedure,” particles gather fan shape the contact points the medium applied over the Current durations more than sec magnify this undesirable pattern and mask the true indications. order make positive study the segregated carbides and aus- tenitic areas, was necessary make microscopic examination. The speci- mens were ground and polished, then etched with pct nital. Segregations and austenitic patches were located and marked for later ex- boring tool 250 magnification after photomicrograph the same area the same magnifications after Magna- flux had been used. Fig. reveals the qualitative nature iron particle in- dications. Measurements means eye piece micrometer low magnifica- tion showed that definite powder pat- terns will found nonmagnetic areas small 0.1 square cross-section. The accuracy: obtained and the ease with which the deter- FIG. 4—Longitudinal section annealed bar stock showing Magnaflux indications segregation. Actual size. $ 4 gt we a 48—THE IRON AGE, October 25, 1945 ru tel wit def too 4 its the edg car ting | thar whe minations are made, make something more than “crack find- ing” instrument. Having established the sensitivity the method, the metallurgist able use the procedure for quality bar stock and tools, Fig. longitudinal section annealed bar stock prepared and tested described, showing carbide segrega- tion. The magnetic particle indica- tions this condition will better than the results obtained macro- etching using 1:1 HCi 170° for min. further investigation warranted, metallographic ex- amination 100 should used. quality control bar stock be- fore making tools important be- cause cracks are likely develop heavily segregated areas during sub- sequent heat treatment. fig. note the white-banded appearance segre- gation and the straightline crack running the same direction the stringers. Along the crack the heavy carbide area, large amounts austenite were formed during hard- ening and not broken down down tempering. Because this retained constituent, stresses are concentrated and results, Extensive Magnaflux indications segregation and austenitic retention has definite bearing upon tool life. Boring cutting tools take the brunt the work the nose and cutting edges. The carbide stringers and the high amount austenite retained with them lie planes right angles the cutting edge. This has definite stress-raising effect. the tool ground several times during its use, the tendency across these planes increased the front edge worn down. Actual fractur- ing may take place when heavy chip being taken. drills, ream- ers and counterbores, the ends the carbide segregates are present cut- ting edges lying near the original bar-center. Chipping will occur when these areas are sufficiently large, and retained austenite present fur- ther soften these points. (1) Segregations and areas with retained austenite are found high- speed tools the magnetic particle method. (2) Leakage fields around the mag- netic matrix are weaker when in- terrupted nonmagnetic constituents than when cracks were present. These areas are indicated more strongly when higher current densities are a ~ Longitudinal section bar cen- 4 ‘a « used than the routine examination pieces for cracks. (3) Positive identification seg- regates and austenite the cause magnetic particle patterns was de- termined microscopic examination TABLE Annealed Conditions AMPERES Continuous Method 200 None None 500 700 None 900 1200 Slight Good 1500 2000 Fair Strong Residual Method Transverse Section hardened and etched specimens. (4) Before making tools from high- speed bar stocks, inspection longi- tudinal sections the wet-con- tinuous method provides rapid and accurate indication quality. INDICATIONS Longitudinal Section TABLE Heat-Treated Conditions AMPERES 500 700 900 1200 1500 2000 Transverse Section INDICATIONS Longitudinal Section Slight Fair Good Strong Strong THE IRON October 25, 4 | | tere 7 r | Continuous 200 None Fair Good Residual Method 2000 Fair 3000 sintered carbide tools and dies may now duplicated sectional carbide nib molds, accord- ing Firth-Sterling Steel Co., production records achieved Keesport, Pa., the conclusion years experiments into this branch powder metallurgy. This company probably the largest producer such preformed nibs, and also pro- duces the steel casings and shanks for the molds and plungers. Carbide Mold Co., Pittsburgh, the first fabricator the finished nibs and molds. Specifically cited, the case tory plant engaged pressing LEFT nib, now spotted, ready for the grinding jig. BELOW RINDING the sectional nib exact size done with surface grinder. 50—THE IRON AGE, October 25, 1945 Sectional Carbide Molds Facilitate Recutting tungsten-silver contacts. The tool steel molds originally used operated connection with hydraulic presses exerting presure tons per in. When this setup proved incapable producing points tense enough reduce burning, and when such molds had discarded after 12,000 fewer compresses, the de- cision was made shift sectional carbide nibs and carbide-tipped plun- ger. Simultaneously the manufac- turer stepped the pressure from unprecedented tons. After 27,000 compresses had been achieved with the new setup, the copper brazing holding the carbide tip the steel plunger failed. The manufacturer ordered plunger solid carbide, shrink-fitted into the steel shank. With change, the mold continued service from 27,000 124,000 units, which time the mold was examined and was found have worn less than 0.001 in. The plunger was redressed, 0.008 in. being removed from its head. The engineer the job, after noting that the mold had worn less than 0.001 in., and that the toler- ance permitted these electrical contacts 0.005 in., estimated that the mold should good for 500,000 compresses before recutting would become necessary. The number recuts this mold, based the amount carbide stock the nibs, reported five, which forecasts production 2,500,000 units during the complete life the mold. Regular operating test runs the new type molds other plants indi- cate that production 500,000 pieces per cut are commonplace, Mr. Loach reports, adding that number molds now operation have been recut many five times, and that ten twelve recuts would seem entirely practical many inst the sint due mat terr com cop) silv com : | instances. Specifications governing the amount stock the original sintered carbide nibs such molds determined the anticipated pro- duction, the recutting has proved not only practical but economi- The sectional nibs existence are made Firthite hardness de- termined the metal powder compressed. The test applications date have covered the following pow- dered metals: carbon, brass, bronze, copper, iron tungsten, and tungsten- silver. substantial number the new type molds also are being used connection with pellet presses for compressing pharmaceutical powders. Sintered carbide has proved its ability resist compression load- ing with its compression strength some 700,000 pounds per sq. in. Deci- sion shift from solid sectional nibs followed the persistent observa- tion that sharp corner solid nib subjected load doubles, triples further multiplies the stress, de- the largest diamond tool containing the largest industrial diamond ever used, diamond grinding wheel dresser weighing 62.5 carats when service Oct. 18, 1940, now weighs The dresser, manufactured Diamond Teol Co., Chicago, yielded 8064 dressings for 10.55 carat loss since its last resetting. RIGHT the the mold. Toler- ance 0.0003 “in. each side. BELOW AND-LAPPING the mold with diamond powder. pending upon the angle and sharp- ness the corners. was noted that under such repeated stress, the high local stresses the corners fatigue failure cracking and chipping. Recutting solid nibs was only possible hand, which was impractical. comparison, the lap- ped seams the sectional nibs achieved “controlled” cracks com- paratively free trouble and insur- ing full life for the mold. Sectional nibs, thought, will eventually make possible for the user fin- ish his own molds. The major advantage the sec- tional opposed the solid nib, pointed out, the fact that the nib may recut and that the life the mold limited only the amount stock which Recutting the original size ad- vantageous for both standard shapes and special shapes that call for long production runs, because worn molds are reclaimable. addition being recut original size sectional nib mold also may recut larger size within the limits the nib di- ameter. The dresser was used Northwestern Engineering Co. in. diam in. face, Grade 401N27 Carborundum wheel Norton crankshaft grinder. THE IRON AGE, October 25, 4 y j 4 . | . — GAS CARBURIZING the second part this three-part article, the reactions the various used the carburizing process are de- considerable detail. The control soot precipitation and the physical and chemical factors involved gas carburization are discussed. ° ERNEST Lieutenant, U.S.N.R. generally accepted theory the mechanism gas carburiz- ing represented the reac- tions: This evidently does not represent the actual condition. carburizing temperatures, not formed such, rather there present carbon dissolved This would therefore modify the above reactions follows: CH, + Fe Clin Fe) 2H, temperature and any carbon content the steel, there definite ratio which the carburizing and ten- dencies are just 100 Cementite- Austenite ® a 1500 1600 Temperature, IRON AGE, October 25, 1945 1800 CaRBON contact with steel carburizing temperature, car- bon given the steel surface and decarburizing agent (carbon dioxide) formed, shown the reaction: The reaction reversible, and or- der continue the carburizing opera- tion, sufficient concentration must maintained drive the reaction from left Carbon monoxide relatively feeble carburizing The term “available carbon” used RIGHT Available gases for carburiz- ing. mathemati- cal computation, seen 0.0337 natural gas avail- able for carburizing 1700 °F, shown point above. This about 1200 times the amount for vol- ume generator gas, shown point Lb. carbon per cu.ft. natural gas ° ° determined. express the maximum amount carbon pounds that may ob- tained from given gas composition given temperature. commonly used gas used com- mercial carburizing, CO, pet has relatively low available carbon. For partial pressure 0.2 atmosphere (which about the common commercial usage), the car- bon available for carburization can equilibrium constant deter- mined the relationship 15,966 15,966 1.668 46.56 *Based the reactions: +0, Curve for natural Temperature 1800 Lb. carbon per charcoal gas — where This For ing used.” gas Ss ora and let The 1000 buri Temperatu 1:100 Ratio CH,: 1:20 ratios for the and CO::CO re- with loys saturated with carbon. ° ° 1100 3—The equilibrium curves show thot very small will equilibrium with high carbon steel carburizing temperature. composition the right curve; composition the left decarburizing. Simplifying: The equilibrium constant also re- lated the partial pressures and CO, by: Since the volume the active gas equals unity, that is, CO. Therefore, since the partial pres- sure 0.2 atmosphere, 2 46.56 0.2 where 0.9957 Thus, the total carbon 0.2 mol, which 0.2 2.4 only 0.43 pet available for carburization the rest locked gaseous com- pounds system equilibrium. Sinee 60°F, occupies 380 ft, the weight available carbon ing agent, high rates flow must used.” also used diluent gas for the heavier Penetration, per cent For any given tem- perature and any car- bon content the steel, there definite ratio and decar- burizing tendencies are just balanced fig 1750°F, about are required keep the gas mixture slightly carburizing high-carbon steel.” Fig. shows, for example, that when sufficient time has been allowed for equilibrium, pct CO, pet gas 1500°F will carburize but higher; 1600°F this gas would carburize only 0.40 pct carbon. METHANE: Methane carburizes ac- 5—A mixture containing over pct air has reduced carburizing potency. Smaller air additions, how- ever, reduce the amount soot. 120 100 120 020 030 040 050 060 070 080 Ratios 0.6 Ratio 0.2 0.7 when the atmosphere diluted with nitrogen. cording the following CH, + Fe - Cie 7 Fe) + 2H, This reaction also reversible, and the CH, concentration must main- tained high enough drive the equa- tion from left right. agent can shown computation similar that made for From the relationship: shown that 0.0337 carbon per natural gas available for carburizing 1700°F. This shown point fig. and about 1200 times the amount for equivalent volume generator gas, shown point fig. 2.” equilibrium curves shown fig. 3,” that very small will equilibrium with high carbon steel carburizing temperature. the figure, composition the right curve carburizing the steel represented that curve; composi- tion the left decarburizing. Fig. shows comparison between burizing power methane com- pared with carbon monoxide. City gas usually contains THE IRON AGE, October 25, 1945—53 1600 1700 Peot Heavy 5 Annealin cent Penetration, cm. 004 008 016 Penetration, in. pet methane natural gas up- wards ETHANE, PROPANE AND BUTANB: Ethane, propane and butane are alike their behavior. They break down rapidly carburizing. temperatures, and concentrations above approxi- mately pct neutral diluents, will deposit free soot the work. These gases can considered rapid-reacting LEFT 6—Moist hydrogen active decarburizer, perhaps the most active decarburizer known. ° ° RIGHT 7—Methane equilib- rium curves. Curve represents deoxidized and dried; gas mixture containing 0.6 pet volume, and gas mixture contain- ing 3.3 pct volume. The presence small crease the percentage 0.24 methane required main- tain equilibrium. Ethane present almost all nat- ural gases varying percentages, while propane available very pure state liquid form. For car- burizing purposes, propane from the natural gas fields preferred that made oil refineries. The lat- ter type contains high percentage propylene which certain gas mix- tures deposits coke.“ ° ° ° coefficient rithm scale against coefficient increases quite rapidly the temperature in- 9 creases. 18 o-Grube methoo concentration the dif- x< 10 ° ° Atomic per cent carbon gases carrying only combination two separate ways amount available carbon per unit volume when mixed with neutral diluents the proportions for best 54—THE IRON AGE, October 25, 1945 has been used overcome coke forma- tion when using the higher hydrocar- bon gases. One dilution with hydrogen and the other intro- gas.in atmosphere, per cent ducing most the hydrocarbon gas into the high temperature zone the The high hydrogen diluent lowers the tendency toward tar forma- tion retarding polymerization chemical change resulting formation new compound whose molecular weight multiple that the original substance—a reaction involving successive addition large number relatively small mole- cules form the final compound polymer) and bringing about high temperature pyrolysis (thermal de- composition) the hydrocarbon into hydrogen and carbon that free from the objectionable features. intro- ducing most the gas into the high- temperature region, the thermal breakdown rapid that the saturated hydrocarbons are unable persist and the lower and more stable saturated series bring about carburi- zation without these interfering reac- NATURAL Natural gas may used either raw diluted. From any one source has the advantage hydrocarbon content and the disad- vantage, used the raw state, depositing excessive amounts soot the work and retort unless care- fully rotary machines and vertical fur- naces, natural gas usually diluted mixing with air mixing ma- chine such the Selas mixer. For box-type batch operation continuous furnaces, unit used pre- pare burned gas constant composi- tion from natural gas. this unit, practically perfect combustion the air and natural gas occurs and flue gas almost any desired composition can produced. The proportion raw gas gas pet CO, pet H:, 4.5 pet CO., remainder used gas 2600 2400 | ur cit ing sin suc ani mit con ten bon not | depen upon the character the case Typical analyses natural gas are given the table Detroit 0.4 76.0 14.0 Pittsburgh 83.4 15.8 0.8 Canton, Ohio 1.2 0.8 1.0 79.2 16.1 0.2 0.8 80.7 17.0 1.5 Hydrocarbons the paraffin series and constitute over pct these gases and, therefore, provide very active carbonaceous atmospheres. The sta- bility the paraffin series decreases with increasing molecular weight, methane being decomposition prod- uct. Methane -in turn. decomposes slowly equilibrium between HERE are great variations analysis from day day depend- ing demand, the gas being modified additions produce standard heating The gas very rare- used for carburizing purposes, but some instances, weakly carburizing city gases has been enriched satu- ration with hydrocarbons, the gas be- ing bubbled through benzene similarly mildly volatile liquid,” the addition may made injection in- the gas stream. Atmospheres may prepared volatilization such hydrocarbons dipentene and aniline. The liquid usually ad- mitted the carburizing chamber controlled quantity. The soot-forming tendency these heavier hydrocar- bons great, but artificial turbu- lence fan produced, the excess available carbon introduced need not great, and soot deposit may held harmless amount.‘ Natural gas preferred for gas carburizing because its relative purity and because the high content the sluggish reacting methane makes the gas easy Gas: Typical analyses city gas are follows: Unsaturates Lowe reported the use hydrocar- liquids dripping the liquid into the chamber containing the hot charge, volatilizing the liquid. The resulting gas forced through the charge fan. The majority the the hydrocarbon done the charge carburized; thus use made nascent carbon. The fan also recirculates part the cracked gas, thereby diluting the rich incoming gas and preventing the for- mation soot.” PREPARED ATMOSPHERES: mercially prepared atmosphere called gas used for carburizing. This gas prepared cracking non- combustible mixture air and gas contact with catalyst high peratures. The gases are quickly chilled after the cracking reaction has been completed. The prepared gas contains water carbon dioxide; HIS gas becoming increasingly popular for bright carburizing. Another prepared atmosphere, gas used bright carburizing. This gas prepared similarly gas, except that not cracked com- pletely. The composition gas used for the carburizing atmos- phere, excess carbon will form the work surface soot. Soot precipitation may ocetir such degree that dense, sheath produced, firm and continuous enough large sections from work. the popular opinion that some soot desirable insure satisfactory carburization, with the belief that visible soot indicates that the carburizing reaction proceeding the proper direction, well protect the surface the work against oxidation removal from the furnace,” but may, accumulates sufficient quantity, block the sur- face the steel interfere with Wyzalek states that soot formation the work less objectionable when carburization accomplished with work motion, thus continually breaking the soot surface, the case revolving horizontal retort fur- naces, than when the work sta- tionery.” control the carbon content the case and eliminate formation excess soot, diluting gases are used with the object controlling dilution the rate which carbon liberated from the hydrocarbon source carbon.‘ The effect diluting gas, shown fig. 4a.” Williams states that nitrogen apparently does not enter into any the reactions carburizing.“ carried out Williams using pure nitrogen mixed with natural gas showed variation until the percentage became high enough dilute the medium too great extent. shown fig. will noted that mixture con- taining over pet air has reduced carburizing potency, although soot somewhat decreased smaller air ad- curve obtained for pro- pane diluted with air, which patented process.” Pure dry hydrogen considered slow decarburizing agent.” decarburize, hydrogen must combine with carbon according the reaction: mixture prevents this reaction from proceeding, nonexistent all gas the other hand, moist hydrogen fig. Jominy states that the most active decarburizer known.” Sykes has investigated the carburiz- THE IRON AGE, October 25, 3.0 0.6 5.6 12.1 44.6 4.3 4 0, co, co H, | CH, N, 1.20 carburizing. This rate supply the desired 0020 0040 0060 0080 0.100 Case depth, inches ing and decarburizing equilibrium for hydrogen and methane 0.18 pct car- bon steel, using natural gas pct methane content, the source methane. also studied the effect the equilibrium increasing amounts moisture. shown fig. the presence small amounts moisture increase the percentage methane required maintain equi- librium.” Oxygen powerful de- accordance with the reaction: CaRBON Carbon dioxide active decarburizing de- according the reaction: While vigorous media with high avail- able carbon (previously defined) can apparently tolerate large percentage carbon dioxide, its presence dilute media definitely For example, active carburizing ob- tained from pct propane neutral diluents, whereas concentrations this same gas pct the mix- ture fed furnace, have been found necessary produce equivalent re- sult diluting media con- tained approximately pct water vapor and carbon dioxide.“ Reduction soot and consequent as- depth, inches 020 STEEL surance maximum carburizing use carbon dioxide diluent has been disclosed Brower.* However, the absence economical source carbon dioxide renders this method scientific interest Water vapor also active decarburizing media, al- though contradictory experiences have been reported. Bramley found that dehydrated greater carburization than bub- bled through water,” while Guthrie found dry city gas inferior gas with definitely controlled content. Williams could find dif- ference carburization with natural gas—fiue gas mixtures with dew point ahd 85°F, nor with natural gas dry and saturated with room temperature. Here, with CO; the tolerance natural gas apparently great, for has been found very damaging working with dilute media reduced carburizing the other hand, Jominy has shown that saturated steam alone amounts water vapor with hydro- gen Gas: The general term flue gas used cover media prepared partial complete combustion heating gas under controlled condi- tions, resulting medium contain- ing largely with CO, CO, and present amount determined IG. ature penetration curves after can seen that in- creasing the tempera- ture acts increase the rate carburization. Carburizing heat, hr. 56—THE IRON 1945 ‘the partially spent, the mixture burnt. Such gas it- self usually oxidizing carburiz- ing temperatures due the high moisture and content. the per- centage flue gas increased, the richness the medium decreased, and lower maximum carbon content will CHARCOAL TREATED Gas: Commer- cial use has recently been made diluent prepared passing flue-gas mixtures over heated charcoal, pro- equivalent and high with but traces CO. and This, will noted, based the water-gas reaction which steam, passed over hot coke, reacts give gas largely and The diluent prepared this manner, containing practically oxidizing CO. and should and does make very satisfactory carrier medium. Since the amount what may anti-carburizing gases, that is, CO: and small, large excesses carburizing agents counteract are unnecessary, and the medium can run close the desired equilibrium analysis. Thus high low-carbon may produced with minimum soot deposition, only sufficient active gas being used produce the desired available carbon. The percentage active gas required obviously lower than when the diluent contains CO, H:O which tend reverse the de- sired reactions. Carburizing has been performed such gases with com- plete absence soot tin has presented data carburiza- tion atmospheres butane diluted with high percentages dissociated This diluent was prepared unit giving output high dis- sociation products ammonia, that pet and pet According Williams, commercial applica- tion this work has been made carburizing, but believes that this diluent should useful for carburiz- ing media controlled activity give selected maximum carbon con- tents, since free from oxidizing and decarburizing constituents.” Dow reports that the most nearly perfect diluent gas has found decarburizing- agent-free, but still methane-rich, gas which comes from the muffle gas carburizing furnace. This gas need only slightly additional hydrocarbon and returned the fur- nace.* Gas carburizing depends the ability the carburizing medium supply atomic carbon the metal surface. The carbon absorbed whe carl sion conc surf quit crea the the high the face amot time conce close! and fusio mens neale vary AST! pract count steels vary ent solvec tion, rate Sch the fir and face tempe contra staten The the wo! on lar on | 5 the steel surface and diffused into the work. The rate diffusion depends temperature, carbon concentration gradient and the factor diffusivity (diffusion coefficient) for the particu- lar steel use. This diffusion phenomenon based Fick’s Law form) AD. where the rate diffusion carbon into the steel, the diffu- sion coefficient, and the carbon concentration gradient between the surface and the core the steel. The diffusion coefficient increases quite rapidly the temperature in- creases, shown fig. The diffusion coefficient carbon gamma iron increases regularly the carbon concentration increased, the rate increase being somewhat higher the higher concentrations, Harris conducted carburizing ex- SAE 1020 steel and cal- culated the diffusion rate terms the carbon concentration the sur- face the calculated values for the diffusion coefficient (the amount substance diffused unit time across unit area through unit concentration gradient) agree very closely with the calculations Wells and The latter conducted dif- fusion experiments using steel speci- mens different carbon contents welded together and nealed. The coefficient diffusion does not vary with grain size the range ASTM Nos. which includes practically all the grain sizes en- countered plain carben and alloy The rate diffusion does not vary with impurities ordinarily pres- ent steels. Oxygen dis- solved gamma iron, even satura- tion, does not appreciably change the rate diffusion carbon.’ Schlumpf remarks that the non- forming alloying elements tend retard the progress car- burization impeding both (1) the surface carbon build-up and (2) the diffusion action.” Harris corroborates the first statement, stating that nickel and silicon particular lower the sur- face carbon concentration (at given temperature).” Wells and Mehl, contradiction Schlumpf’s second statement, have found that the effect manganese 2.5 pet and nickel The elements that are strong carbide ° ° 12—Typical carbon pen- etration curves. eliminate peeling chipping between and core, the carbon gradient should gradual. Carbon, per cent ° ° formers, according Schlumpf, tend increase the surface carbon con- centration and the rate carburiza- tion.” This plausible that the al- loys will absorb additional carbon form alloy carbides and doing increase the carbon concentration gradient. The rate flow carburizing gas over metal surface must sufficient supply the desired amount car- bon the steel. The results obtained varying the flow the gas shown fig. Cowan conducted corresponding velocity tests using propane the carburizing medium and found that there was optimum rate gas flow which gave the best carburizing re- sults.” Too low volume carburizing gas results shallow depth case, while too slow movement the gas results nonuniform depth case. the other hand, increasing the flow beyond satisfactory maximum results apparently pronounced tur- bulence carburizing gas the This creates nonuniformity both depth and character case and the same time produces car- bon deposit the product with tendency toward coking, resulting soft spots the quenched work.” In- creasing the rate carburization can also accomplished increasing the temperature, illustrated fig. (prepared from test runs produc- tion vertical stationary type gas re- tort using natural gas atmospheric pressure). These curves approximate closely the carburization rates obtain- ° 13—Actual carbon pen- etration gradients for car- burizing bars SAE 1020 steel, withdrawn after 2.3, 4.3, 6.3 and 8.3 1700° and air cooled. Penetration, inches able regardless the gaseous me- dium used.” Great stress laid avoiding sharp line demarcation between case and core, that the carbon-pene- tration curve should not steep. Such curve makes the case liable peeling chipping that line, phenomenon called enfoliation ex- Fig. shows typical car- bon-penetration curves.” may that the surface carbon concentration obtained higher than desirable. change the carbon con- centration gradient, diffusion period may added the carburizing pe- riod, all the same cycle. The flow natural gas stopped, and the diffusion cycle proceeds atmos- phere weak charcoal gas, which has carburizing power and which pro- tects the work from decarburization. Thus the carbon allowed diffuse inward the desired extent without building excess carbon the sur- face.” has been established that car- burizing, the penetration varies di- rectly with the square root time elapsed after the steel has reached the carburizing temperature, and the con- dition maximum carbon the sur- face has been attained.” The relation time carbon penetration (case depth) illustrated fig. 13, which represents actual concentration-depth curves for carburizing bars SAE 1020 steel, withdrawn after 2.3, 4.3, 6.3 and 8.3 1700°F respec- tively and air cooled.” Boegehold and Tobin report tests made that show the outer case con- tain higher carbon content 1500°F 0.100 0020 0040 0060 0080 Depth, inches THE IRON AGE, October 25, 1.20 1020 Steel than 1700°F and further, that the carbon content was greater than pre- dicted the They explain this inverse variation carbon con- tent the surface with temperature, the basis absorption rate dif- fusion rate. the lower tempera- tures, the absorption rate much faster than the diffusion rate that supersaturated layer austenite produced. The diffusion rate increases with increasing temperature causing the surface carbon decrease stead- ily until finally point reached very high temperatures where the diffusion rate fast enough pre- vent the formation saturated austenite the Harris challenges this hypothesis and reports that the Buick Motor Div., carbon contents the surface carburized samples come fairly close the amounts called for the A.m line the equilibrium diagram, modified according alloy content. bear this out, fig. (shown Part III) shows the results car- burizing various steels with steady flow-of controlled mixture parts natural gas, analyzing pet Ch, pet C,Hs lene, analyzing 22.7 CO, 2.2 and 75.1 pet (0.0 pet CO.). The figure indicates what would expect- theoretical grounds, that the saturated austenite contains more car- bon the temperature increased, and the carbon any particular tempera- ture greater than called for the Harris suggests that deposition hard coke the steel surface, (due gas mixtures far from equilibrium) surface carbides which are quite com- plex found alloy steels, may pro- duce the results shown Boege- hold and Tobin. goes say that from straight diffusion stand- point, difficult postulate any movement carbon from the steel surface build concentration above that percentage carbon which sol