The Iron Age 1940-01-18: Vol 45 Iss 3

VAN DEVENTER President and Editor n f S. BAUR Vv Vice-President and General Manager it \- Managing Editor News Editor Editor Emeritus n Machinery Editor irt Editor Metallurgical Editor Associate Editors Washington Editor is Resident District Editors Pittsburgh Chicago it Cleveland Detroit 2, Editorial Correspondents London, England Cincinnati e n Boston Hamburg, Germany Milwaukee San Francisco e SANDERSON CLYDE ENNIS ic Toronto, Ontaric Birmingham € 1. | Toronte ntario irmingh Sanuary 1k. 19 10 Leroy W. ALLISON ltioy M. EDMONDS n Newark, N. J. St. Louis The Modern Hold-Up 23 Alumina and Silica Refractories if A. H. DLN, Manager Reade Service Mill Part Fabricated Thermit and Arc Welding d Emerson Findley 2? 621 Union Bldg.. Cleveland Bldg., Phila. Stamped or Die Cast? 36 H. WK. Hottenstein. 1012 Otis Bids Chicage 5. H. E. Leonard, 239 W. 39th St New York Veirce Lewis. 7310 Woodward Ave Detroit Ober, 239 39th St., New York Practical Annealing Fitzgerald 428 Park Pitts Warren. P. O. Box 81, Hartford, Precision Gear Hobbing Don Harner 1505) Pacithe Avenue, Beach Cal. Member, Audit Bureau of Circulations Member, Associated Business Papers Indexed the Industrial Arts Index Sunken Scrap Cargo Salvaged Electric Magnet Published every Thursday Subserip tion Price: United States and Dos sexsions, Mexico, Cuba, $6.00; Can Single Annual Nun Washington News THE NEWS BRIEF Owned and Published by CHILTON Statistics Metal Working Activity (Incorporated) Weekly Ingot Operating Rates Editorial and Plant Ex ansio i i e Chestnut and 56th Sts., 230 West 39th St. ™ Philadelphia, Pa., U.S.A. New York, N. Y., U.S.A OFFICERS AND DIRECTORS A. MUSSELMAN, President JOS. S. HILDRETH Vice-President EVERIT B. TRERHUNE, Vice-President J. H. VAN DEVENTER, Vice-President Products Advertised 102 8. BAUR, Vice-President WILLIAM BARBER, Treasurer Index Advertisers | JOUN BLAIR MOFFETT, Secretary ; JULIAN CHASE, THOMAS L. KANE ©. BUZBY, P. M. FAHRENDORPF, HARRY V. DUFFY Copyright 1940 by Chilton Company (Inc.) + 7 aS ~ 3 ter A RYERSON any for any any kind steel. Your order will get Immediate Action. The steel stock, and will delivered promptly where and when you need it. When steel inventories are low, when you need unusual sizes analyses, when non-uniform quality steel hinders production, call Ryerson. Over 10,000 sizes, shapes, and kinds steel and allied products from structurals stainless, from heat treated alloys nuts and bolts are included Ryerson Certified Steel products. All are closely controlled analysis, finish, ete. and each represents the highest quality that par- ticular class and type material. Ten strategically located plants assure prompt, dependable service. Draw the one nearest you. gladly send Stock List. Joseph Ryerson Son, Inc., Chicago, Milwaukee, St. Louis, Detroit, Cincinnati, Cleveland, Buffalo, Boston, Philadelphia, Jersey City. 22—THE IRON AGE, January 18, 1940 Ryerson Products Include: Beams, Structurals Channels, Angles, Tees, Zees Hot Rolled Bars Bands and Hoops Floor Plate Plates (over kinds) Sheets (over 25 kinds) Alloy and Tool Steels Heat Treated Alloy Stainless Steel Cold Finished Shafting Strip Steel, Flat Wire Mechanical Tubing Boiler Tubes and Fittings Welding Rod Bolts, Nuts, Washers Concrete Reinforcing Babbit Metal and Solder Write for Stock List te } \ THE IRON AGE ... JANUARY 18, 1940 ESTABLISHED 1855 Vol. 145, No. Modern Hold-Up ROUND the dark and lonely corner came sinister figure confront the ap- proaching pedestrian. commanded, pointing automatic his surprised victim. came the pedestrian's hands. said he, are just little too late. Another fellow your profession just held and took money. haven't any took your money, did nmented the highwayman. you out your money, your watch and chain and other property? glad know that partner, Bill the Bandit, was the that doesn't leave anything for exclaimed the pedestrian. should think that you would sorry that somebody got ahead you. Did you understand when told you that had valuables left for you said the footpad. what you think? Don't you realize that this the modern age specialization—a new deal burglary? not inter- ested taking your money. want your exclaimed the alarmed victim. can any one steal another man's brains? thought they were burglar behind the said the highwayman. companion took care your money. specializes physical property and its redistribution. spe- cialize mental property and its redistribution. continued the footpad, the right possess more mental intellectual property than the submerged third his fellow citizens. You have written and copyrighted two books and patented two important inventions. Stand and de- liver this mental property Just then our friend the pedestrian woke from his nightmare and found him- self his accustomed chair before the fireplace. his knee was newspaper ac- count the latest New Deal attack the patent system! | | pet _ Gee 3 = ‘ 4 § j You Inland “It’s refreshing, job like mine, find men who really study problems —who contribute much toward solving them. You Inland men work like members our own staff—always the alert for ways improve our quality reduce our costs. find that the time spend with Inland sales representatives, metallurgists and executives time spent the advantage our good many steel buyers feel that way—and will good many more, when they discover the real meaning and value Inland Service. SHEETS PLATE BARS PLATES STRUCTURALS RAILS TRACK ACCESSORIES REINFORCING BARS — y j ~ St., CHICAGO District Offices: MILWAUKEE DETROIT ST. PAUL ST. LOUIS KANSAS CITY born St., CHICAGO District Offices: MILWAUKEE DETROIT ST. PAUL this carefully article the author de- scribes the nature alumina and silica refractories, meth- ods producing and types commercial material, and physical properties the various grades. this, the first section the two-part report, consideration given the alumina-silica diagram and its significance, fire clay refractories, semi-silica bricks, and manufacturing processes and properties. largest single consumer refractories the steel industry which uses well above half the total quantity produced. While basic refractories are highly important every phase their application, the so-called acid refractories have much wider use. Almost all acid re- fractories are made alumina and silica, and they include those produced from diaspore, flint and plastic fire clays, silicious clays, ganister, quart- zite, sand stone, etc. The products referred include extruded-repressed, HOBART KRANER Ceramic Engineer, Bethlehem Steel pressed, (power pressed) hand made, slip cast, and fused, cast refrac- tories. The alumina-silica equilibrium the ceramic engineer what carbon diagram the metallurgist. carbon diagram “from above” speak, thinking terms the changes which take place during the cooling iron-carbon melt. the solidifies, further changes take place. However, due the fact that the components have been liquid they are capable attaining degree equilibrium than the cera- mic compositions. The latter undergo only partial fusion during firing and the result usually heterogeneous mass. The ceramic therefore, looks upon his alumina-silica diagram “from below” were, and de- pends largely upon fusing tendencies estimating the value refractory for metallurgical use. mainly interested the temperature the first liquid phase form the tem- perature the refractory material raised. Naturally, also concerned about the reactions which occur upon exposure hot slag. realized engineer, that the refractory which develops liquid phases low temperatures will, generally speaking, react more readily with the slag relatively high tem- peratures than those which liquid phase does not form with the same ease. Fig. the diagram most familiar the ceramic engineer shows the true fusion relations compositions alumina and silica. will noted that silica the form the mineral cristobalite melts 1710 deg. (3110 deg. F.). Addition only per cent alumina lowers the fusion temperature 1545 deg. C., (2813 deg. F.). Alumina itself melts 2050 deg. (3722 deg. F.), and the only mineral which occurs the system mullite. This does not have defi- nite fusion but melts incongruently 1810 deg. (3290 deg. F.), that is, breaks down form corundum crystals and liquid containing about per cent alumina and per cent silica. consisting entirely mullite, would withstand load without deformation 1810 deg. (3290 deg. F.). Mixtures richer alumina and mul- lite not develop liquid phase until THE IRON AGE, January 1940—25 | | Ain = { | 100 5.5 94.5 1810 28.2 1810 100 2050 Cristobalite and Temperature deg.C So 1400 Kaolin Mullite and liquid Cristobalite and Corundum and liquid Corundum and S Temperature, Mullite Cyanite Anhydride system, Brown and Grief. 1810 deg. (3290 deg. and the extent liquid formed this tem- perature proportional the amount mullite the mixture. With more silica than mullite the mixture liquid phase appears 1545 deg. (2813 deg. F.), and the amount liquid formed attains maximum point the diagram. However, From Journal 238. intermediate composi tion, between the mullite and point show some tendency soften 1545 deg. (2813 deg. F.). High quality refractory clay bricks made from fire clays usually contain approximately per cent silica and are, theoretically least, more refractory than the eu- tectic composition Flint and plastic Flint and IG. 3—Effect fluxes constituents) and silica the refractoriness coal measure clays. From Bulletin 26, Ohio Geological Survey, 490. 26—THE IRON AGE, January 1940 Pure materials have sharp melting points. the case mullite the melting point sharp, although the melting process matter decomposition into liquid and the mineral corundum, already stated. Silica, the form cristo balite, the most refractory the silica minerals, also has melting point in- fractories amounts cristobalite will, therefore, withstand loads this temperature without developing refractory consisting entirely the mineral corundum would also have sharp melting point. However, such refractory not commercially avail- able. silica refractories with relation the Fig. generally considered that silica bricks are more retractory than most fire clay bricks, which may largely attributed the fact that they have higher softening point under load than most fire clay bricks. The softening fire clay bricks affected the presence large proportion the eutectic com- position (95 per cent silica, per cent alumina) and therefore quite evi- dent when clay bricks are heated the vicinity 1545 deg. (2813 deg F.). further and highly important rea- son for this softening clay refrac- tories the effect alkalies and other impurities upon the clay composition. Unfortunately, this fact has not vet received general recognition users ularly severe clay refractory fusion affect the toriness clay refractory. The alkalies are perhaps more important factor than any other single compon- ent determining the suitability certain refractory clays for high tem- temperature, cent will seriously perature service, and yet few analyses show this important constituent. the constituent most difficult deter- mine accurately, and many are worthless. Fire Clay Refractories The United States blessed with refractory clays type not avail- able any other country. They are generally referred clays, although the term measure clays” would more appropriate. The term 2000 0.60 Plastic . . ro) e 0.2 fire clay properly refers all clays with fusion temperature above 2750 deg. F., and clays, kaolins, Coal measure clays fact that they almost always with coal, and they are name from the two three types. The general types are flint fire clays plastic fire clays. Semi-flint fire clay intermediate type, the which are largely indicated its one would expect, flint fire characteristics name. clays are the are flinty appearance and character and have little plasticity. The plastic fire clays which naturally are plastic when ground and mixed with water, clay production such clay tories. Various plastic clay are used batches de- pending upon the plasticity required the particular process used. difference flint and plastic fire clays not the physical properties only but also the chemical characteristics. Table gives typical compositions flint and plastic fire clays, and shows their sion temperatures cones. should noted particular that the potash and soda contents represent the greatest single difference each these two groups, and this may closely correlated temperatures. however, important, will seen Fig. view the fact that they produce small amounts liquids especially soda and potash, promote early fusion softening the clay temperatures below 1545 deg. (2813 deg. F.). various temperatures, affected the content these fluxes, fusion result, the por fired also directly and the alumina-silica ratio. shows early Fig. effect alkalies; and rapid decrease the pore volume the plastic clays when fired cone whereas the flint fire clays show only slight tendency this di- rection. From this would seem that one should use refractories consisting almost entirely flint fire clays. This may hold true number cases; however, for many purposes such re- fractories might not all suitable economical. must remembered that exten- use increased proportions Silica mortars 2—D Hint fire clay must paid for the consumer. owns and mines flint fire clay, and coal, and fire clay most economical use larger pro- portion the plastic fire clay which mines. 4 Per cent volume absorption porosity) The poorer grades clays, with lower softening ranges, provide refractories more impervious slag than those type clay bond inter- \hea \mediate heat duty Silica, per cent istribution alumina-silica refractories with relation the alumina- silica equilibrium diagrom. greater refractoriness; this may The firebrick manufacturer considerable value preventing slag plastic penetration. centage flint fire clays, are not generally fired temperatures which low porosity Should this done the present kilns the bricks the lower tories fusion temperatures Cones 2000 2100 2210 2300 2380 2520 characteristics fire clays referred Table Note how the plastic clays shrink whereas the flint clays, because their greater refrac- toriness, are practically unaffected these temperatures. THE IRON AGE, January 1940—27 y > ) l- q it part the setting would that part the setting which they support. not entirely practical attempt attain low porosity firing alone. Many the flint fire clays are suscep tible what termed secondary the break-down certain minerals which occupy the space microscopic stratification the origi Linear change, per cent 300 2350 2400 flint fire clay grains. Obviously such secondary expansion Hint fire clay grains apart and opens the attainment low porosity. clays used with such Hint fire clays over-fire elevated temperatures, evidenced bloating after they have been fired hard attain minimum porosity. This overfiring the plastic 2550 2600 2650 2100 2750 Temperature deg. plastic fire clay (rounded pores) and secondary expansion the flint fire clay grains (long, thin, parallel pores). the same temperature which ondary expansion occurs the flint clays. The net result rather than decrease the porosity, hevond certain degree fire. This shown Fig. which shows thin section refractory taken from open hearth door, which the flint fire clay grains show secondary while the plastic fire clay pansion load bearing ability 3000 3050 3100 6—Load test curves (load lb. per sq. in.), showing the rigidity silica brick failure, contrast the pyroplastic characteristics fire clay bricks. Semi-silica bricks are somewhat superior clay bricks this respect. 28—THE IRON AGE, January 1940 | - 4 wries high temperatures con siderable importance furnace walls and roofs, especially where insulation used. the furnaces operate con tinuously, silica bricks are the most logical from cost and standpoints If, however, they must able withstand sudden heating and cooling, clay bricks fairly open and coarse texture, generally flint clay, should used. Semi-Silica Bricks Clay bricks type, with minimum clay content, have been found even more suitable purpose. The reason for this fectly obvious when again the situation considered from the standpoint early softening portion the fractories. Clays general, ticularly the more plastic clays, has been stated, are seriously affected fluxes. Any one the forms pure silica, quartz, tridymite cristobalite, has definite and high melting point. should stated silica brick with approximately per cent silica, contain quartz undoubtedly are close enough together make contact with each other, with the clay filling only the interstices. the clay portion carries the impurities and small comparison with the large amount quartz mineral pres ent, the actual impurity content viously low. The alumina-silica dia gram indicates lower fusion tem perature for such clay-bonded brick than fire clay bricks higher alumina con tent. Manufacturing Processes and Properties However, must remembered that this case not only alumina silica combinations are being consid ered, but also the effect naturally occurring fluxes the constituents which substantially all alumina and silica. Such clay refractory will, therefore, shrink and soften badly 2800 deg. F., though that temperature soften ing very slight, due the high purity the principal portion the material. Fig. shows the deforma tion curve such refractory, com pared with that silica and other fire clays super-duty refractories. The type process used manu- facture clay refractories affects Porosity, per cent 800 2000 2200 2400 2600 2800 Firing temperature, deg. mortar clay which expands bloating moderate temperature may more desirable many applications than one which more refractory and does not bloat until higher temperature reached. No. above clay which expands 2400 deg. F., whereas No. does not bloat until higher temperature their properties, illustrated the data Tables II, and IV, sub mitted different refractory manu facturers. general, the following holds true: Increase value property reached. Cold crushing strength generally that process which pro- duces the most namely, the steam process, involving and vacuum treat- Increase degree burn 8—Effect fire properties fire clay bricks. These properties result from the greater density, lower porosity and greater degree coalescence hard fired clay products (From, Status Tests for and McDowell, Blast Furnace and Steel Plant, June, 1929). THE IRON AGE, January 18, 1940—29 | No.2 fuses cone 18° c& TABLE Ohio Coal Measure Clays Used for Firebrick* Flint Clays Plastic Clays Ignition loss 12.90 10.53 11.29 10.72 9.95 8.12 7.80 9.33 ..... 1.30 1.91 2.85 1.76 2.52 3.48 2.80 2.38 CaO 0.50 0.26 0.25 0.21 0.42 0.22 0.39 0.20 MgO 0.08 0.19 0.06 0.32 0.17 0.87 0.24 0.05 trace 0.00 0.10 0.39 0.25 0.22 0.18 K.O 0.52 0.66 0.34 0.17 2.40 3.02 2.30 1.46 MnO trace trace trace 0.05 Fusion, deg. 3128 3080 3114 3052 2786 2800 3002 From Bulletin No. 26, Ohio Geological Survey. TABLE Test Data Bricks Made Processes Hand Made Dry Pressed Stiff Mud Wood Hammer porosity ............ 16-17 8-12 24-26 18-19 Bulk Specific Gravity 2.18-2.23 2.25-2.32 2.0-2.04 2.13-2.18 Reheat, 2552 deg. 0-0.3 0-0.3 Reheat, 2912 deg. 0.5 1.0-3.0 0-1.0C tion 246? deq. F., per cent load per sq. 2.0-4.0 1.0-3.5 0.5-1.5 Panel Spalling Test, per cent loss cycles 0.5-4.0 6.0-12.0 3.0-8.0 2.0-8.0 Modulus rupture, 1800-2000 1600-1800 1600-1900 Grain medium fine coarse and coarse medium TABLE Effect Processing Raw Materials (Same mix and grind used all cases) Hand Made Dry Dry Pressed Process Repressed Pressed Repressed Porosity 20-24 16-18 12-15 14-16 Spalling loss, A.S.T. per cent. crushing strength, Lb. per Modulus rupture, Lb. per sq. Above data apply high heat duty fire clay brick made predominantly flint fire clay and having the following P.C.E. and chemical analysis: P.C.E., 52.6 SiO.; 43.3 2.5 0.3 CaO; 0.3 MgO; alkalies. TABLE Properties Firebrick Made Three Processes from the Same Clays Auger Machine Hand Dry (Vacuum) Method Manufacture Made Pressed Repressed per cent linear change ...... 0.3 0.3 A.S.T.M Panel Test, per cent loss Load Test, 2462 deg. per cent shrinkage, load per 4.7 6.0 3.3 Water absorption, per cent weight water 9.6 7.9 Apparent specific gravity 2.68 2.54 2.59 Bulk density, grams 1.99 2.04 2.17 Modulus rupture per sp. in. 570 700 1500 Cold crushing end, 900 1800 2500 Chemical analysis, per cent: SiO. 50.40 50.40 50.40 ...... 42.02 42.02 42.02 Fe.O,; 2.32 2.32 2.32 2.62 2.6? 2.62 0.17 0.17 0.17 1.97 1.97 1.97 30—THE IRON AGE, January 1940 operations produce the lowest will noted that the hand made bricks have the highest porosity and, general, though not entirely, lower loss the spalling test. mass not compacted. High spalling loss would expected from the most dense product. Fig. illustrates the behavior two clays which are ordinarily used mortar clays. difference composition these clays produces individual characteristics which cause over-firing clay No. 2400 deg. whereas clay No. shows such evidence 2600 deg. This over- evidenced bloating, and results higher porosity and conse- quent lower bulk gravity after 2400 deg. has been reached. Clay mortar where open joints are avoided, The bloating clay No. gives tendency toward filling the joints, whereas the ity clay No. accompanied continued shrinkage the entire mass which tends open the cracks the hotter face the brick. The degree fire likewise the properties clays tories. Fig. shows what may ex- pected when clay bricks are fired various temperatures, although must kept mind that the firing clay bricks governed the processes in- Firing effects partial in- cipient fusion and carried too far causes the refractory lose its shape, either pressure where the firing only moderately excessive, due its own weight where the heat treat ment more severe. will also noted that the resis- tance thermal spalling decreased the fire. While resistance spalling not im- portant many installations, must taken into account. dense refractory might not suitable for intermittently operated furnaces while entirely satisfactory for furnaces such glass tanks which are operated continuously for more, Ed. Note:—Next week the author con- cludes this paper with methods manu- facture for and detailed data the manufacture and properties aluminous refractories. | a j ~ | | | | 4 | ~ AST week, the first part this two-part article, the author described the flame hardening process, equipment used, quenching procedure, and the progres- sive method flame hard- ening. attention directed various types hardening machines, charac- teristics the hardened Meehanite case, the minimi- zation distortion, and the advantages Meehanite metal flame hardened. HERE are several standard ma- chine tools that are well adapted for conversion torch harden- ing machines, among which the lathe probably the best suited the greatest number shapes encountered. The torches may held attachment from the tool holder, and the work pan should provided catch the quench and cooling water, and vari- able speed drive the carriage de- sirable give the operator full con- trol speeds during the operation. The hardening cylindrical objects can accomplished the spiral pro gressive method which the work BICKFORD Co., Inc. rotated centers vive the required surface speed while the torch and quench advance distance equal the width the treated section each revo This method, course, avoidably results spiral soft streak overlap, but may not objection able many types service. These overlaps may made parallel the axis the cylinder desired, traversing the torch with the carriage while the work stationary. Many shapes composed variation treating cylinders turning the cylinder slowly while each pass being made. ‘This results number spirals, depend ing upon the width the torch and quench assembly and the ence the piece. lathe also well suited har method. differs pro treated surface heated before any high rate speed and heated suitable heads placed two three points around the circumference. The surface temperature raised above the critical few seconds—the flames are shut off and the quench applied simultaneously. results from using large vol water under low pressure. [his process best suited automatic con trol and large quantity production. chine may made the conversion small horizontal boring mill milling machine. The slotted table mounting for torch equipment, and permits the operator equipment three directions. adjustments while the operation progress. The spindle fitted with variable speed drive and chuck for revolving the work. Such machine well suited such shapes short disks, pulleys, tapers and certain types cams. standard flame cutting machine well suited hardening because the range speeds encountered cor- responds that used cutting. The conversion merely requires the sub stitution heating blowpipe with suitable heads for the cutting blow- pipe. Such machine suitable for hardening straight parallel passes such machine ways and gear patents for the use such machine are held the Linde Air Products Co. The vertical combination method for hardening the surfaces cylindrical objects such rolls has been patented and extensively developed within the THE !RON AGE, January 18, \ a Y q 1 q q q 8 | | | | 4 war | ORCH and quench assembly for hardening roll the vertical com- bination method. Photo courtesy Linde Air Products Co. past year. Rolls treated this method are supported vertical position and rotated while torch and quench as- sembly entirely surrounding the cir cumference the roll horizontal plane passed upward over it. Thus the entire surface the hardened single pass. (See accom Since narrow band heated entire- around the roll, and the quenching this band uniform and simultan- eous all points, the overlap inher- ent the lathe methods avoided. The vertical position also minimizes the tendency distort, and most advantageous for quench water drain- age. Annealing previously hardened rolls may accomplished method with minimum distortion, after which the roll may again chined and rehardened. boring mill can con 32—THE IRON AGE, January 1940 verted harden rolls this method. plate supported horizontally from the tool holders, and carries the torch and quench equipment. should covered with shield pro tect from the quench water, which trough built around the bed the machine and drained. Air sprays are required prevent over- heating parts the machine exposed the flames. The roll held chuck the boring mill table, while the top held central floating center which must compensate for pansion the roll during heating. The quench used special de- sign, and each one limited small range diameters. Each quench ring used with different number multiflame heads, which are equally spaced around the circle radially fac ing the roll surface. radial adjust ment the heads required change the set-up from one another, even when the change diameter not great enough re- quire change quench rings. After this adjustment made, the torches and quench are bolted together form rigid unit. vertical boring mill only suitable for comparatively light rolls, and necessary handle them vertical position, which sometimes and awkward. special roll harden- ing machine constructed which will facilitate handling and accommodate larger rolls. more recent process the harden method similar the one just de- scribed except that the flames and quench are directed radially outward radially inward. The method especially applicable cyl- inder liners, etc. The relative motion between the torches and work the same the case hardening Characteristics Case case produced flame hardening the same the base metal. Only the structure The zone maximum hardness tends from just below the surface about one-half three-quarters the total depth the case. This zone consists martensite with hardness about 550 (See accompany- ing figure.) change zone the base metal gradual, the martensite blending into troostite, this sorbite, and finally the itic base metal having hardness approximately 240 This grad ual change due the temperature gradient can seen both the curves hardness versus case depth taper ground samples, and the accompany ing photomicrographs case, transition zone and base metal. The slightly lower hardness surface probably due the presence austenite caused rapid quenching this point. The fact that there sharp demareation line be- tween the case and base metal explains the high resistance spalling flak- ing, which resistance characteristic flame hardened Meehanite. The greatest hardness obtainable setting the flames close the sur- face produce the most rapid heating effect and traversing compara- tively high speed, following closely causes minimum heat absorption the core and allows the highest rate cooling the surface metal heat extraction the quenching water This procedure results shallow case, however, and usually sirable gain increased case depth the expense lowering the surface hardness. The relation between hardness and depth case may seen from the accompanying curves. distance between the flames work variable, there are practical limits beyond which effect can gained. These values have been found from experience correlated with results. The same also true traversing speeds. The distance between the flames quench affects the time interval heating and quenching, thus having its effect upon the depth case. rough general rule gives thi- distance three times the case depth desired. Obviously, this not vari able where combination heating quenching heads are used. the spot hardening and spinning methods, the hardness and depth are controlled within limits the length heating time only, since the Hardness, Brinell converted from Scleroscope quench applied. assuming that removal the flames immedi ately followed quenching. Minimum Distortion factor hardened castings usually small, and well within manufacturing tolerances. depth treated, while the core relatively cool. Therefore distortion decidedly less than from other methods hardening. The amount distortion unpredictable most cases and depends upon the shape and stiffness the casting, the initial stresses it, the method hardening employed, and the depth case desired. Some experiments have been made URVE graphs showing hardness and structure the case, transition zone and base metal flame hardened Meehanite sample, taper around. Linde Products Co. photo. dicting distortion regularly shaped objects, but these have sulted demonstrating that probably such rule exists. However, usually found that contraction the hardened case causes. flat piece become bowed dish shaped, and amount distortion hardening the reverse side. possibility pre- correction exists when sufficiently large numbers identical castings are desired. After measuring the dis tortion encountered, allowance made for the amount subsequent castings. This procedure limited the difficulty exact duplication conditions both casting and hard- ening. variation which might un- detected the hardening procedure could substantially alter the amount distortion. stresses are present before the hardening operation, they will tend deformation when heat applied. Therefore, stress relieving castings prior harden- ing distortion. many cases, castings are partly submerged circulating water used the un- treated surfaces during the hardening 0.020 0.040 0.060 0.080 0.100 0.120 Depth below surface, inches 0.160 0.180 0.200 = | THE IRON AGE, January INCHES This prevents overheating the base metal, consequently result- casting sections should not less than formity the casting section desir able and abrupt changes thin sections are avoided. any growth the flame harden- ing Meehanite occurs, small negligible because the fact that heating takes place for such 600 Qa ° 2514 5b Cc 2 357 34—THE IRON AGE, January 1940 5/ inches short time, and limited small part the section. formed the process, and the change the surface slight dis coloration due the formation very thin film oxide. occurs when the surface becomes overheated. usually possible make second even third pass over the same surface the event that the previous passes have not given the sult. this however, pre except ABOVE ROSS-SECTIONS rounds, flame hardened the ver- tical combination method. Linde Products Co. photo. ° ° LEFT PPROXIMATE sur- face hardness versus depth case Meehanite, ing conditions. cautions should taken starting stopping the previously treated surface. drawing after hardening sometimes recom- mended, has not been found the best procedure and not generally practiced. Advantages Hame hardened Meehanite metal are superior flame hardened steel. one case where the surface was contact with plastic abrasive material, the life flame hardened Meehanite was considerably than that casting given similar treatment. instance, however, was necessary change steel casting meet the shock requirements. For the most part data with flame hardened steel, are lacking because most applications are too re- cent give useful information however, that the excellent lubricating ability Meehanite will continue make very desirable material for many applications, even when the in- itial cost the casting not portant consideration. hoped that the foregoing planation the various flame harden ing processes presents clear picture from which the designer visualize its application his particular prob lem. the whole, the process lends itself well accessible surfaces regular shapes. While possible harden surfaces unusual shapes the machines use, such types cams, variations the case are expected due unavoidable variations the hardening operation this type work. Many advantages flame hardening over other types hardening are parent. hardened surface obtain- able without affecting the properties the core. Thus, with their inherent disadvantages may replaced many applications with hardened case which integral part the casting. The process applicable many castings for which full hardening would entirely suitable, operations are possible which would very difficult fully hardened Acknowledgment The author wishes express his ham Co. for permission publish the material contained this paper. knowledgment also made for assist- ance rendered Linde Air Products - \ ‘ | | | = 4 + | | | > 7 T | | | | | + + | | | | | | | | e i ECAUSE lubrication ties experienced with cast iron housings blooming mill pin- ions, the Andrews Steel Co., Newport, Ky., recently evolved new type housing fabricated from plate means welding. Somewhat unusual welded fabri- cation was the combined use both the thermit welding process and elec- tric arc welding the construction the first the new type housings. Central members were flame-cut from 8-in. plate the form two pieces. These two members were then thermit welded together make large U-shaped piece, in. cross-section the weld. All other members, flame-cut from plate rang- were welded the U-shaped central section means are welding. Heavy mineral coated electrodes, depositing weld metal containing 0.50 per cent molybdenum and having tensile strength 68,000 73,000 Ib. per sq. in., when stress relieved, were used for the electric welding. Joint design included double beveling all plate edges and the work tioned that, with the exception few short passes, all welding could done downhand. All the work was preheated be- fore the electric welding and the entire assembly was kept 250 300 deg. during welding. The welding was done continuously, with two four welders working three shifts, that welding each joint, once started, could finished without interruption. About 140 weld- ing hours were consumed, aside from the making the thermit weld. Prior machining, the entire struc- MILL TED AND ARC WELDING ture, including bases and caps, which were fabricated separately, was an- nealed approximately 1200 deg. The procedure followed resulted warping being held minimum, and inspection after heat treatment showed that where misalinement had occurred, was, most cases, less than 1/16 in. The fabricated housing, ft. in. high and ft. in. wide, weighed, when completed, 22,500 including caps and bases. Design and construction the new type housing were done under the supervision Mitchel, chief engineer, and Gruell, welding superintendent, Andrews Steel Co. 4 | 1 4 4 al 4 a ena a j central section this blooming mill pinion housing made two J-shaped pieces 8-in. plate thermit welded make large U-shaped piece. All other members are arc welded. The finished housing weighs 22,500 THE IRON AGE, January 18, 1940—35 | | q Carre ¥ A ha | ea parts, admittedly have wider field application than die castings. But. still, there are nu- merous cases which either can used. good knowledge compara- tive physical Properties and the fac- tors which affect relative production costs required making logical choice. There are unvarying rules govern the selection. However, feasible make some statements fact and cite some specific examples which will aid the designer deter- mining which type product will bet- ter meet certain sets conditions, general, the sheet metals from which stampings are ductility, toughness and strength not commonly associated with cast metals, should remem- bered, however, that the zinc alloys, which are the most widely used for die casting, are high ductility and (among the cast metals) and have tensile strength about half that mild steel. These die castings are often sub- jected the same punching operations performed stampings and some cases forming operations, although much inferior stampings this lat- Aluminum die castings rank below the zinc alloy type duc- tility and tensile strength and much below them impact strength, but are widely used for parts, particu- larly parts which must light weight. Brass die castings having tensile strength approximating that are They are high ductility and remarkably high wide choice die casting alloys. Their are certainly not inferior those sheet stock suitable for that they cannot, numer- cases substituted for stamp- ings. Whether and where the substi- tution feasible economic grounds depends upon other factors con- sidered below, 36—THE IRON AGE, January 18, 1940 HERBERT CHASE often weigh less than the correspond- ing die casting, but this frequently offset greater stiffness. The latter may result from somewhat greater thickness metal, from variations thickness and shape from ribbing not feasible the MATERIAL Costs: Most stampings are produced from sheet steel which costs much less than the alloy most widely used for die casting. the re- stamping for one steel, however, the cost material may favor the die casting. This especially likely when the stamping scrap, for the scrap losses die casting are almost negligible. the stamping can made than the die casting, can some in- stances, the lower weight may offset higher material cost. But should not forgotten that many small alloy die castings are produced with sections thin 0.030 in. and fairly large ones with sections only 0.050 in. thick, VARIATIONS When the part logically calls for consider- from point point, provide bear- ings, mounting bosses, integral stiffen- ing ribs, for self-fasten- ings and the like, the die casting usually presents marked advantages. For stampings not usually feasible vary the section thickness greatly, even though drawing opera- tions and certainly not the extent possible die Stampings well die castings are often provided with stiffening ribs and flanges, course, but ribs can often added die casting where not feasible the RATES: \mong advantages the stamping tion. Fifteen “shots” die fillings minute exceedingly high rate production for die even the other hand, die casting dies, espe- cially those for small parts, often have several cavities, two which need have the same shape. Hence, single cycle the casting machine, several variously shaped parts often rarely feasible stamping. NUMBER OPERATIONS: Die ings are completely formed sin- gle cycle the casting machine, opposed this, the stamping, espe- volved, often requires several opera- essary. Drawing operations are fre- quently done, course, progressive dies which turn out finished piece each working stroke, but this ne- cessitates rather expensive series dies and feeding mechanism without parallel the die casting. The latter usually Passed through trim die, but similar die needed, rule, for trimming stampings also. Cost: Die cost significant and frequently controlling factor af- fecting the choice between stamped and die cast parts. for certain simple parts, die cost for casting isually lower than for the correspond- ing stamping, unless the latter requires little forming. This partly because die involving several cavities often the stamping, whereas single die Cavity suffices form die casting. Moreover, parts which are readily die cast one piece often necessitate the use two more pieces stamped. This, course, requires more dies and involves assembly operations not needed the die casting. ~ | | ° ° ° | } | 4 P Cost: Despite these ences die cost and sometimes as- sembly cost, the stamping often less expensive than the casting, largely because the stamping produced rule much more rapidly, once the dies are available. The lower piece cost the stamping (especially stamping) may not offset the greater die cost the quantities required range from small medium. But quantities are large, say over 100,000 steel pieces, the differential cost frequently favors the stamping. There are, course, exceptions both ways and there are often other factors be- sides cost which affect the choice. Accuracy: accuracy and DIMENSIONAL spect ability maintain required tolerances long dies remain service, the die casting usually has advantage over the stamping. Dies for casting, especially those for which dimensional does not have high melting point, are usually subject much less wear than stamping dies. Then too, variations springback, which affect the stamp- ing, not occur die castings. cored almost any angle the die casting and often require further operations except, some cases, the removal fins. are often punched blanking stamping, but the part must drawn, likely Comparative Physical Characteristics and Costs for Similar Die Cast and Stamped Parts ! (See Illustrations) Name Part Gear for seat adjuster Glove Compartment Door Blower Housing End fitting for paper rule Weight, Over-all dimensions, in. Quantity required per year 2,000,000 125,000 2000 large Cost dies Stamping $20,000 $2,000 $500 Die casting $2,500 $785 $450 (2 cavities) Piece cost, cents 1.93 64.821 61.5 per cent less than stamping Rate production, pieces per hr. Advantages stamping Cheaper, stronger, Simplified application trans- Lower piece None harder, more wear- fer used finishing, opera- resistant. tion which gave trouble the die casting. Advantages die casting Made one piece Made one piece with inte- Lower die cost which per- Lower cost, more satisfac- against twoforstamped gral mounting bosses, as- mitted alterations mod- tory, red rust, better assembly. sembly required. Die cost erate cost. Also total cost for appearance, requires ap- much for 2000 parts plus die lower plied finish. stiffer, held stamping dies. than for stamping. closer dimensions and includes letters and cast serrations. THE AGE, January 18, le, q | e- | n ron > | | ! | with center line within This diameter must concentric with center within 0.005" 0.299" Sis Shave 0.303 both sides XAMPLE Gear for seat adjuster die cast form, made one piece with integral hub. (Right) Two stamped parts which were substituted for the die cast part because they were more cheaply and rapidly produced. See table for relative costs. require separate die punch required can formed integral especially the latter has axis holes, especially they come odd with die casting and can set disposed that not feasible draw angles, which would present prob- any angle. stamping usually readily. lem die casting. sleeve boss necessary provide separate piece possible, course, such provide bearing long where there must boss bearing, produce stampings, such All edges must for transfer application 7; of i Holes 90° Ctsk across width may vary either template Top surtace direction across length with exception clock mounting area XAMPLE B—Die cast door for glove compartment with integral bosses for clock and lock mounting. Except for difficul- encountered applying transfer part the finish (which led the substitution stamped assembly in- volving much higher die cost) this part was satisfactory. See table for cost die and castings. Piece cost for stamped assembly not available. 38—THE IRON AGE, January 18, 1940 — Ss t I : ‘ : A 4 0861, | \! ' RIN 90 \ it} 32" | id ----- > wy Section B-B ” \ 1775 automobile bodies, much larger than any die castings, and fabricate assembly welding, not feasible most die castings. But for smaller parts, including some mechanical and some largely decorative, the die cast- ing offers certain advantages, both shape and changes section thickness. cast one piece. There are, however, rule, such parts are many assemblies which both stamped and die cast parts are em- ployed. Usually, such cases, each part supplements the other—each per- forming functions which the other could not perform with equal economy all were made one type process. FINISHING: the score econ- omy finishing and the types finish feasible, advantages can cited for both types product. smoothness attainable stamped parts and they can even formed from pre-finished stock. Moreover, finish can baked stamping almost any required temperature and finishes such vitreous enamel can used which require firing tem- peratures well above the melting point most die castings. the other hand, drawn parts often show draw marks and ripples which are hard remove and, buffing polishing required, the part may out shape and have scrapped. Die castings are not subject the latter faults. Today, they are often made with sur- faces smooth, cast, that only light buffing required prepare them for plating. Organic thetic finishes many types are avail- able for die castings, some them suitable for baking temperatures which have adverse effect upon the die casting. equal care the selec- tion and application the finish exercised, there reason why the finish applied die casting will not match durability that corre- sponding finish stamping. After long exposure weathering, plated die castings often show less deteriora- tion than steel stampings plated with corresponding care, partly because the latter develop stains from This one reason why die cast radi- ator grilles are used preference the stamped type large propor- tion American makes cars. Differences appear- ance tending favor the die casting over the stamping account for selec- tion the former numerous cases. | | C—Housing for blower which was produced die cast form largely because the lower die cost compared with stamped hous- ing, for which the piece cost much lower. Also, the die casting die permitted making certain contemplated changes which would cost much more had stamped housing been produced. Comparative costs are given the table. The die castings make possible use sharper corners and edges and certain combinations shapes not at- tainable without extra operations undue expense the stamping. though this may considered some- intangible what advantage, has tional view stamped as- BLACK sembly first used producing STEEL this end fitting for photo- graphic paper reel spool. Experiments attempting form the stamping one piece did not give satisfac- tory results, hence the three- piece assembly was used which cost more than the cor- responding die casting and was less satisfactory. (Right) Die cast end fitting now produced large quantities two-cavity die, which cost less than the stamping dies, and which yields lower cost well more satisfactory product. See table for de- tails. proved real importance numerous Cases, Cost Estimates: When experience indicates that part can produced either stamped die cast form, the foregoing are among the consider- (CONTINUED PAGE 65) TIN-PLATED STEEL THE IRON AGE, January at | — \ | a | ; { : +6 x i MIDS H \\\ \\\ \\ o = | A essential step the cold working metals the appli- cation mechanical energy the metal alter size and shape. doing, there results change the internal structure the metal nature impart new physical properties. The application heat energy the metal will further change its physical properties. This hot treat- ment may have for its purpose re- storing the metal structure that which possessed before cold work- ferent structure. The thermal treat- ment encompassed the generic term, The word annealing compre- hensive term which has been suscep- tible many definitions. The most authoritative that set forth the 1939 edition Metals Handbook which annealing described cluding the following thermal opera- tions: full annealing, process anneal- ing, normalizing, patenting, spheroid- izing, tempering, malleableizing, graphitizing. not within the purview this paper consider all these opera- tions—only consideration will given the annealing processes which have direct bearing upon the art cold working metal. its simplest form annealing in- volves subjecting metal tempera- ture substantially below that which will melt and allowing the metal found so-called spot annealing which cold worked metal shape heated specific spots its surface means blow torch. This usually applied points where the metal has been subjected maximum deformation strain, and thus relieving these localized strains the metal shape can subjected fur- ther cold working without the neces- sity annealing the shape whole. 40—THE IRON AGE, January 1940 Research Director, Surface Combustion Corp., Toledo More specifically, however, anneal- ing should considered three- step process: (1) Heating predetermined temperature, (2) hold- ing such temperature for prede- termined time, (3) cooling pre- determined rate. The several terms previously enumerated are used designate methods w