The Iron Age 1942-07-23: Vol 150 Iss 4

23, 1942 OHIO ROLLS CARBON STEEL ROLLS ALLOY STEEL ROLLS PLAIN CHILLED IRON ALLOY IRON ROLLS MOLYBDENUM CHILL ROLLS NICKEL CHILL ROLLS FLINTUFF ROLLS DENSO-IRON ROLLS HOLL-O-CAST ROLLS SPRINGFIELD, — ; for ICTORY —from the Production Lines behind the Firing Lines Increased Production Developing Forming Tool Operator Lukrafka who works for the Cash Company, Decatur, was turning brass tubing job with two knee tools and die head the hex cutter and facing tool the cross slide. The sketch shows how developing forming tool, was able combine the turning and facing cuts into one operation from the cross slide. The die head completed the job. Indexing was elim- inated. Time saved! Production stepped third! Many such ideas from patriotic operators are sent us. recognition their initiative and resourcefulness, are proud present these men with gold Victory pin. These “Ideas for Victory” are published “Blue shop bulletin sent free Warner Swasey thousands turret lathe operators. Make sure your operators are get- ting “Blue Chips” their homes. Write Warner ARN Swasey, Cleveland, Ohio. You CAN BETTER. FOR LESS = 4 JULY 23, 1942 VOL. 150, NO. VAN DEVENTER President and Editor BAUR Vice-President and General Manager ° ° Managing Editor, LIPPERT News Markets Editor, ROWAN Technical Editor, OLIVER Associate Editors JAMES Art Editor, WINTERS Editorial Assistants BENEDETTO Resident District Editors Washington Pittsburgh DONALD BROWNE W.A. PHAIR Washington Chicago Cleveland Detroit CHARLES POST San Francisco Editorial Correspondents DEARING ROBERT McINTOSH Buffalo Cincinnati FRAZAR RAYMOND KAY Boston Los Angeles HUGH SHARP JOHN McCUNE Milwaukee Birmingham SANDERSON Toronto, Ontario BACON Seattle ROY EDMONDS St. Louis DIX, Manager Reader Service ° ° Advertising Staff Emerson Findley Uni Blair nion Bldg., Cleveland Herman, Chilton Bldg., Philadelphia Hottenstein, Otis Bldg., Chicago Raymond Kay, 2420 Cheremoya Ave., Los Angeles, Cal. Leonard, 100 East 42nd New York Peirce Lewis, 7310 Woodward Ave., Detroit Ober, 100 East 42nd St., New York Robinson Johnson, Market Research Mgr. Hayes, Production Manager. Baur, Typography and Layout. ° ° Member, Audit Bureau Circulations Member, Associated Business Papers Indexed the Industrial Arts Index. Pub- lished every Thursday. Subscription Price North South America and Possessions, $8; Foreign, year. Single copy, cents. ° Owned and Published CHILTON COMPANY (Incorporated) Executive Editorial and Offices Advertising Offices Chestnut and Sts. 100 East 42nd St. Philadelphia, Pa. New York, U.S.A. OFFICERS AND DIRECTORS MUSSELMAN, President JOS. HILDRETH, Vice-President SEORGE GRIFFITHS, Vice-President EVERIT TERHUNE, Vice-President VAN DEVENTER, Vice-President BAUR, Vice-President WILLIAM BARBER, Treasurer JOHN BLAIR MOFFETT, Secretary JULIAN CHASE, THOMAS KANE, HARRY DUFFY CHARLES HEALE Editorial Spongers Technical Articles Fine Tool Finish Soaking Pit and Reheating Furnace Refractories Portable Spray Booth for Short Cuts Aircraft Chemical Finishes for Aluminum Alloys. Dry Machining Magnesium Armco Introduces New Galvanized Scrap Burned New Equipment: Small Tools and Gages. Features Assembly Line Washington West Coast Fatigue Cracks Dear Editor News and Markets This Industrial News Personals and Obituaries Machine Tool Activity. Non-Ferrous Metals Scrap Markets Iron and Steel Scrap Prices Comparison Prices Finished Steel Prices Warehouse Prices Index Advertisers Copyright. 1942. by Chifton Comeany (ine. 116 119 120 121 123 124 125 126 173 | ° ° 30—THE IRON AGE, July 23, 1942 QUALITY Fabrication even the simplest machine base requires high degree ability and exper- ience accuracy assured. But, when comes the big, complicated takes EXTRAordinary skill and equipment. The huge Base, pictured here, typical many such intricate designs produced Mahon, most which are repeat orders from customers long standing. But, remember, SIZE makes difference Mahon quality—the same ex- cellence workmanship goes into the building every Mahon Welded Base—large small —simple complicated. you demand Bases that dovetail accuracy and quality with the machines for which they are built, let quote your requirements. Your blue- prints will figured promptly. Deliveries will made promised. THE MAHON COMPANY DETROIT CHICAGO | 7 | 3 q q 4 2 q 4 q iron plant every mine thousands tons sponge iron flowing from these plants into battleships, tanks and guns; additional iron enough make for our shortage scrap and pig iron and thus win the war. That the vision seen the eminent Ickes the Interior and now being presented Congress. What en- trancing vision. This picture has considerable background. Sponge iron not new. For more than half century, engineers this country and abroad have pursued this attractive For years, The Iron Age has advised would-be investors steer clear numerous stock promotion schemes involving the low temperature iron ore reduction process. How many millions dollars have saved the innocent this advice shall never know. The best minds our steel industry have worked this problem, and millions dollars have been invested trying solve it. And now Secretary Ickes has secured appropriation $600,000 which believes will the trick. true that Sweden produces some sponge iron. But very little compared with her total iron and steel production. And Swedish ore high grade ore, not compared with the low grade ores which this process would applied this country. JULY 1942 Germany has low grade ores. And Germany the mother For years Germany has been pursuing sponge iron with the result that today she has metallurgical hangover and two defunct pilot plants. And when the great Goering Works was built, the sponge ESTABLISHED 1855 iron process was conspicuous its absence. The United States Steel Corp. has also pursued sponge iron, spend- ing over $1,500,000 doing. And here what the Corporation says about the authoritative work, “The Making, Shaping and Treating From 1850 and the present time, much money has been spent vain attempts develop direct process which would practical deemed unprofitable include details them here. Sponge iron produced, unlike pig iron scrap, full impuri- ties. This necessitates additional refining operations open-hearth electric furnaces, all available evidence indicating the need for least one additional run off slag each case. You can imagine how that would slow down the capacity our existing equipment. Mr. Ickes estimates that his $600,000 will build two plants, each giv- ing tons per day. Taking the average 40, this means invest- ment $7500 per ton daily sponge iron capacity. You can build blast furnaces that will make real pig iron cost $4200 per ton daily capacity. And know they will work. Let Mr. Ickes play with his $600,000. can with that what others have spent millions trying unsuccessfully do, will take our hats off him. But until makes good, not throw dollars, hours and tons material down knothole search for imaginary dimes. recently learned lot about lubrication dur- ing deep drawing operations. “For years were pretty smug about our practices, believing that our methods were good as, not little better than, the average. “That was before the war, when wastage was impor- tant, but not too important—when could specify ‘tailor-made’ steels—when could stoutly defend our practices and blame failure the steel. “Well, that all changed hurry when were betrayed false Jap diplomacy. “Suddenly found ourselves working new prod- ucts war products— made many kinds steel. Somehow wastage threatened get down. There were trying help our fighting men, but pro- duction records looked bad. seems funny now, but could have been charged with wasting vital steel. “We move fast, and did. called Inland metallurgist. That fellow was storehouse Cut Excessive Breakage Actual Experience —told Inland Customer Dearborn Street, Offices: Milwaukee, Detroit, information lubrication for forming and draw- ing steel. “He studied the construction and condition our dies. checked hold down pressures. learned from him the effect surface temperature gener- ated when drawing. also had answers chemi- cal attack dies, film strength and compounding. His suggestions the proper application and the frequency application lubricants went long way toward helping out our troubles. also gave valuable tips cleaning lubricants from formed parts. “Here the end our story. Wastage almost van- production our shop climbed up, now can hold our heads high when there talk about mass production equipment for America’s fight- ing men. “Our advice you is—call for Inland metallur- gist.” RN SHEETS STRIP TINPLATE BARS PLATES FLOORPLATE STRUCTURALS LYy Fine Tool Finish Increases Tool Life 2000 Per Cent present critical shortage necessary for many manu- facturers change molybdenum steels for the greater number their cutting tools. Some concern has been expressed the effect this might have production, but the experience the Wright Aeronautical Corp. has clearly shown that some molyb- denum steels give results com- parable tungsten cobalt high speed steels when properly applied. fact, some molybdenum high speed steels have proved their superiority individual applica- tions. The solution lies precision machine-ground and honed cutting tools the proper design. program study the ma- chinability various metals actual production has been started, but preliminary those tests, thorough research was first made order develop the most satis- factory tool design for the average rough machining operation the higher alloy steels. Several tool designs were tried, both with and without chip breakers. ample, chip curler 1/32 in. deep and 1/16 in. wide with 1/32 in. land was tried. This groove was ground the top face right out the nose and parallel the cut- ing edge. This type groove was produce effectively and economically without special set-up for chip breaker grinding, and breaking the chips. This same tool without chip curler breaker was also tried, but pro- duced unmanageable chips, and shortened the tool life due in- Tests made over period many months, which over 100,000 alloy steel forgings were machined, indicate that gains tool life times are possible high speed steel lathe tools using new form chip breaker groove and finely finishing the cutting faces. Complete details the method grinding these tools given the authors this important article. creased heat the cutting edge. tool research, single point cut- ting tool for many rough turning operations the Wright shops was produced and will described later this ar- ticle. Many the lathe tools cur- rent use were hand ground by, the operator (Fig. 1). ex- tremely difficult hand grind properly, the original tool angles were seldom duplicated whether they had first been ground cor- rectly not. The machine ground and honed tools developed pro- duced much improved tool life, several hundred per operator ground tools. Research these tools was continued there- fore and through these efforts production method machine grinding and honing tools was worked out. the same time series ex- tensive tests was being conducted various molybdenum high speed tool steels ascertain which the many brands available would give the best tool performance comparison with tungsten cobalt CARL WIBERG and WESLEY HEATH obtain accu- Production Engineering Department, Wright Aeronautical Corp. high speed steels. rate results was essential that absolute uniform- ity maintained, and the two projects were therefore merged into one. the tool life and performance under actual working conditions, all tools were used production runs with care exercised all times. final and more accurate check the various tool brands breakdown tests being made several pro- duction steels various speeds and feeds, but the results are not available this time. Standard Tool Shape The tool design adopted for this research program and used for many rough turning jobs the shop was follows: deg. side rake, deg. back rake, deg. front and side clearance, 1/16 in. nose radius, and chip breaker design adaptable the ap- plication. The chip breaker was ground the same positive rakes chips from the point the tool, and also featured design with depth 1/16 in. and THE IRON AGE, July 23, 1942—33 Wes ¥ 5 4 & J j I—A variety hand ground tools used different operators for the same type rough operation the Wright Aeronautical Corp. Proper control tool angles can only obtained with centralized tool crib control. 1/16 in. shoulder radius all sizes, but the width and angle chip breaker was dependent upon feed, depth cut, and material. speaking, the width the chip breaker the nose end varied from 7/32 in. in. square bit 3/16 in. in. square tool, and 5/32 in. tool. These dimensions were not chosen SECTION A-A 2—Tool angles for rough turning tool made from in. bit, showing the dimensions the chip breaker grove. 34—THE IRON AGE, July 23, 1942 Surfaces marked must honed -4RMS. Hardness Rockwell. C-62 min. arbitrarily, but were selected the basis results obtained series tests. Fig. shows the made from bit. group these machine ground and honed tools illustrated Fig. Advantages Chip Breaker The primary object the use step-type chip breakers the proper width and depth was dis- tribute the force break the turnings into discon- tinuous chips which take less space the machine pan and give the operator less trouble elimi- nating the wrapping chips around the work. The shear angle the chip breaker curls back the chip away from the tool point and against the flank the tool, caus- Stamp etch number = ¥ 6° , SECTION B-B \ \ ing break. Furthermore, there protracted period contact between the hot chip and the tool, and consequently less transfer heat from chip tool. Additional cooling also obtained the fact that the small, rapidly broken chips offer much struction the flow coolant over the cutting edge. The re- moval and disposal such chips since they are much more economical handle. Tool life and performance are greatly affected the grinding finish given cutting tools, may seen the accompanying table, which shows the number pieces obtained per tool grind with hand ground tools and with machine ground and polished tools. The results obtained are apparently due the keenness the cutting edge and the smoothness the end, flank and chip breaker groove tool. Under the microscope, the cutting edge appears irregu- lar saw tooth edge, which varies roughness according the abrasive wheel used and the care exercised grinding. Fig. shows the appearance under the microscope the cutting edge turning tool hand ground the operator. checked with surface analyzer the ness 20-25 micro-in. r.m.s. Fig. indicates improved cutting edge due semi-finished grinding machine ground tool, while +. <= OR 4—Enlarged cutting edge Wright Aeronautical operator. Fin- ish 20-25 micro-in. r.m.s. (Magnifi- cation 100 X). Fig. 3—Machine ground and honed tools the Wright Aeronautical Corp. representative cutting edge precision ground tool that has been carefully honed finish 1.0 1.5 micro-in. r.m.s. The irregular saw tooth cutting edge particularly noticeable Fig. produces uneven flow metal through the crevices which thereby create localized high stress concen- tration. This develops localized heating the tool point, which in- creases the rate breakdown. The resistance chip flow caused the roughness the tool face ag- gravates this condition, creating unstable condition the cut- ting the metal. This produces increasing amounts built-up edge tool, and results rougher machined surface. minimize this effect much possible, method honing the cutting edge and end was de- veloped. For the tool shown Fig. 10x2x2 in. Alundum 5—Enlarged cutting edge tool semi-finish ground, but before honing. (Magnification 100X). vitrified wheel (Norton 38220— LOBE) used. The finishing done dry Ex-Cell-O grinder and requires about min. This wheel easy use and does not burn readily some others previously tried. While easily possible obtain smoothness 1.0 1.5 micro-in. with this 220- grit wheel, finish 3.0 3.5 micro-in. r.m.s. accepted sat- isfactory for the job. Honing time was reduced grinding the clear- ance angle approximately deg. and then honing only the upper half the tool flank and end, procedure that brings this portion the clearance angle back deg. Chip breakers are ground with positive rake and then polished dry with fine silicon carbide wheel finish 2.0 2.5 micro-in. For this part the work, the tools are held one cutting edge machine ground tool care- fully honed, now used the Wright Aeronautical Corp. Fin- ish micro-in. (Magnification 100 X). THE IRON AGE, July 23, 1942—35 | 7 — ve { ‘ time magnetic universal vise surface grinder. Very little stock removed this polishing operation and care must exer- cised order avoid burning the tool producing chatter marks. For rough grinding the chip in. Alundum wheel (Norton 3846—18BE). The shoul- der radius 1/16 in. carefully formed generating the radius the edge the grinding wheel. For the honing polishing opera- moved, and the presence scale which tends accelerate the wear the tool. stated before, all conditions tests were kept uniform possible. Only H.S.S. tools with hardness between Rockwell C-61 and C-65 were used. Tools were set center axis the work and deg. the cut, experience having shown that tool life greatly reduced not keeping the work. the tools were re- Comparative Lives Hand Ground Tools and Tools Finely Finished Machine Material Part Name AMS No. Gear 6250 Gear 6250 Ring 6250 Shaft 6250 Gear 6250 Gear 6250 Ring 6250 Shaft 6254 Gear 6250 Shaft 6254 Shaft 6254 Adapter 6250 tion the chip breaker groove, con carbide wheel (Norton 37320 —J8L) employed. This wheel removes the rough grinding marks which heretofore were plainly vis- Any burr the cutting edge finally removed slight hand stoning. Tools are semi-finished ground wet the flank and end, one time, Oliver grinder adapted with formed cam guide which permits the radius and both clearance angles ground one time. The specifica- tion the wheel used for this preparatory work the tool in. Alundum vitrified wheel (Norton 3846—L5BE). The project was started the fall 1941, and since then over 100,000 pieces different forg- ings have been machined using this tool design about differ- ent brands high speed tool steel. Tests were run continuously three shifts, seven days without any change production routine and set-up. Tools were placed various rough turning operations both automatic and hand turret lathes. Only rough turning operations have been fol- lowed thus far because the 36—THE IRON AGE, July 23, 1942 Pieces per grind with Pieces per grind hand ground tool with test tools 400 100 150 290 200 319 162 102 117 103 200 ground they were brought back center shimming up. turret tool holders this not always pos- sible, but modifications holder designs are planned take care this factor. The brand cut- ting oil was kept constant also was the oil flow individual ma- chines. representative part ma- chined with these tools, and also sample the discontinuous type page “This Industrial Week.” The production materials used the tests are carburizing, oil hardening, and consisting mainly of: (a) AMS 6250 SAE 3312, normalized and annealed, Brinell 187-235. (b) AMS 6254 SAE 3315, normalized and annealed, Brinell 187-235. (c) AMS 6290 SAE 4615, normalized, Brinell 140-190. (d) AMS 6330 SAE 3135, heat treated, Rockwell C-26-32. (e) AMS SAE 3140, heat treated, Rockwell C-26-32. heat treated, 229-255, Brin- ell 241-285 and Brinell 290-321. The proper design cutting tools has been found mary importance the machining metals and there marked reduction power consumption shown recording wattmeter, when the cutting angles are ac- curately formed. increase the side rake angle produces corresponding decrease power consumption, but likewise crease the tool life. thin-edged (with small included angle) would cut more easily, generating less friction than tool. However, the cutting edge must heavy enough work reasonable surface speeds and feeds for the material. necessary, there- fore, strike mean, and for the average ferrous machining jobs, deg. side rake angle was found most suitable. Precision grinding been shown definitely superior hand grinding since permits the and consistent manner definite standards which have been proved experience and test. Some the advantages ma- chine grinding over hand grinding are follows: (a) Establishes definite grind- ing-angles for all tool grinds. (b) Greatly increases tool life. (c) Effects great savings high speed tool steel through re- duced regrinds. (d) Permits the maintenance smaller stock tools. (e) Minimizes machine idleness, resulting increased production. (f) surface speeds and feeds without loss tool life obtained with hand ground tools. (g) Improves quality prod- ucts. Substantial savings tool steel using smaller tool bit. many the tests tool bit, for example, produced more pieces per grind than 1-in. tool bit, pre- viously hand ground. follows, therefore, tool bit machine ground and honed and used the same job would give still greater tool life. the basis the re- sults obtained, possible establish tool change period for each operation avoid running tool complete breakdown. tions, the bits require but very lit- tle grinding restore them first class condition, and there decided economy both ma- terial and grinding time. secondary advantage pre- cision grinding that worth- while saving accomplished the costly grinding wheels themselves, due the less frequent use, and these can kept proper condi- tion being under the care direct tool grinding vision. This, course, eliminates the necessity maintaining considerable number grinding stands the shops. Moreover, makes possible the production standard tools substantial quan- tities, with consequent reduction cost. The rough grinding, for ex- ample, now being done sur- face grinder, using fixtures hold- ing tool bits one time, while the finish grinding the nose radius and clearance angles done, one tool time, using specially formed cam guide which permits the radius and both clearance angles finished one operation. importance attached the proper method handling all cutting tools after precision grinding maintain them their excellent condition. The cutting edges the tools must protected against any pos- sibility damage between the Qualitative Test for Molybdenum these days hustle ma- chine shops sometimes hap- pens that lot molybdenum steel becomes mixed with quantity 18-4-1 high speed steel. the pieces are finished size, be- comes imperative determine their identity without grinding them spark test. The laboratory the Jones Lamson Machine Co. has long sought such Failing find one, the company developed procedure which reported satisfactory the steel contains least 0.20 per cent molybdenum. The test modification the quantitative, colorimetric test now commonly used for the determina- ‘tion molybdenum steel, and based the orange colored com- pound formed from the quinque- valent molybdenum ion the re- action with after reduction with stannous chloride. With these requirements mind the following spot test was (1) small piece filter paper placed clean section the steel tested, and three drops 1-1 nitric acid are placed the filter paper. (2) After allowing the acid react for moment, the paper rolled onto glass rod and transferred medium sized test tube. (3) One ml. perchloric acid placed the test tube and after shaking for few seconds, ml. distilled water added. (4) One drop sodium sulfo- cyanate added the test tube and the contents shaken until the deep which develops, becomes uni- form. The cyanate solution consists gm. NaSCn per liter. (5) Eight drops stannous chloride are next placed the tube and the contents shaken until the solution be- comes colorless. Sometimes extra drop two may necessary render the solu- tion colorless, but excess must avoided. The stan- nous chloride solution made HCl warming slightly; then diluted 100 ml. time grinding and their being placed use machine. Tools should inspected, wrapped with Scotch tape other protector, and then stored cen- tralized tool cribs until ready for distribution. Centralized tool cribs greatly facilitate the placing tools the proper job, sharp and ready for use. Fine finishing cutting tools, carried out production man- ner, can obtained for com- paratively low cost, and will render enormous increase tool life with proportionate reduction tool cost per unit machined. adding cold distilled (6) Ten more drops sodium sulfocyanate are now added the tube and the contents shaken for few seconds. The development deep orange the presence molybdenum. Smaller quantities molyb- denum result lighter shade, and the sample contains molybdenum the solution remains the sample molyb- denum high speed the solution turns bright red color after standing for min. This test sensitive only about 0.20 per cent molybdenum. 168-Hr. Work Week for Machines Spence Engineering Co., Walden, Y., uses the set-up shown below secure 168-hr. week its machines. The numbers the squares are the seven men who operate the two machines. The relief man in- MACHINE No. Time Sun. Mon. dicated bold face. Spence Engineer- ing has found that hr. week about all man can stand. Further- more, not enough skilled men are available for 40-hr. week, and the men usually want the hr. overtime. DAY Tue. Wed. Thu. Fri. Sat. 32 63 63 63 63 | THE IRON AGE, July 23, 1942—37 e- fe. re- ate di- Soaking Pit and Reheating Furnace earlier types soaking pit, the side walls were generally straight and unbroken except for the fire boxes one end and the flues the other. more re- cent designs, for Salem type, the walls are circular and are broken regular intervals burner blocks, Figs. and There still some difference opinion just what expan- sion allowances are required building furnace walls, but would least appear certain that the amount that gives the most satis- factory result less than that which would expected from purely theoretical consideration the expansion the hot face the brickwork. With gas oil-fired reheating furnaces, the walls are broken frequent intervals burners, each which has its own burner block. This often superior quality +4 — | 38—THE IRON AGE, July 23, 1942 material compared with mainder the side wall. Materials: general soaker and reheating furnace side walls are constructed medium alumina brick, but low and high alumina refractories are also employed and give satisfactory service. Table III gives the prop- Sillimanite Chrome Super Duty Brick High Heat Duty Brick Heat Duty Brick Chrome Brick Brick Concrete Ss erties eight bricks that have been found give good results. will seen that they show wide variation properties, the melting point varying from 2822 3200 deg. The use the very refrac- cal economics rather than operating conditions, the clay from which made being mined close the steelworks and the bricks being available cost competitive with that lower grades brought from farther afield. The first six bricks Table III are more typical normal practice. will no- ticed that most these show ten- dency bloat when refired for hr. 2552 deg. They have fairly high bulk density and 9—Circu- lar soaking pit. (Courtesy Salem Engineer- ing Co., ~ = ra = Refractories fairly low permeability air with the exception 15, which cheap, wire-cut brick that does not give good service the others. Their thermal shock resistance 30+ reversals. The use this type brick soaker side walls offers certain advantages, notably their tendency bloat, giving tight joints, and take glaze. Whether insulation used behind the walls also largely question local conditions. Thus, unfortu- nately too often the case, the in- gots tend impact the walls, then walls are better not insulated since they are they not pos- sess the same rigidity. the other hand, well designed rec- tangular pit, insulation quite practical and undoubted fuel economy will result. Hite and Soler mention figure per ton ingots, the insulation being paid for weeks. the United States considerable use made soaking pits micaceous sandstone, commonly known which can cut into large blocks. first sight would appear probable that the use this material, essentially raw quartz, would lead spalling trouble, but this does occur not severe enough make its use uneconomic. When the ingots are exposed the atmosphere and the high tem- perature the soaking pit they inevitably scale some extent, loss about per cent weight being typical. The molten scale formed drips onto the hearth and many soaking pits accumulate depth several inches. The ef- fect this molten iron oxide both the side walls and the hearth can reduced some extent placing coke breeze calcined do- lomite, onto it, but the attack usually severe enough warrant the use special refractories this level the side wall. the past, either magnesite straight chrome brick have been used, but more recently chrome- ° ° ° CHESTERS Central Research Department, United Steel Companies, Ltd., Stocksbridge, England ° ° ° the soaking pit and reheating fur- nace refractories, the author discusses the refractories used the construction furnace side walls, hearths, and flues. magnesite chrome-silica bricks have been employed with consider- able success. The properties the magnesite, chrome and chrome- magnesite brick have already been discussed earlier articles the open hearth furnace. Those the chrome-silica brick are given Table IV. The use these bricks, which were first devel- oped several years ago Great Britain Rees and Lynam, has been largely limited the washline soaking pits, where the results obtained have led their con- tinued use. They represent com- promise between the properties silica and chrome brick which de- pends upon the fact that little, any, reaction occurs between the two main constituents. Thus, the thermal shock resistance, which the same order that chrome brick and markedly higher than that the ordinary silica brick, while the refractoriness under load low compared with that silica brick. Unless some such course employed withstand the attack the molten scale, the firebrick walls rapidly become undercut, and tend fall in. The side walls reheating fur- naces are generally constructed medium alumina brick, the type quently employed. will seen that this dense brick good crushing strength, high thermal shock resistance, reasonable volume stability and melting point about 3056 deg. For the burner blocks, more refractory material usually specified, the quality being similar that described the United States the terms “super- duty” “high heat duty” fireclay brick, whose definitions are given the Manual A.S.T.M. Stand- ards Refractory Materials. The super-duty quality has pyromet- ric cone equivalent value cone (3173 deg. F.) over, while that the high heat duty over (3056 deg. F.). The super-duty brick must also show an, after contraction less than per cent and spalling loss less than per cent the speci- fied tests. For very special work, burner blocks are em- ployed, typical properties this material being given Table under the code No. 14. will seen that these sillimanite brick are not only dense and strong, but show negligible length change refiring for hr. 2732 deg. F., have thermal shock resistance 30+, and refractoriness under load, per sq. in., 3200 deg. Excellent these test results are, they not give fair impres- sion the usefulness the silli- manite brick. Its resistance thermal shock considerably greater than that most the best fireclay brick, while its maxi- mum safe temperature much higher. Like fireclay brick, subject fairly rapid attack molten scale, but contrary the opinion frequently expressed, its resistance ferruginous slags usually greater than that of, say, per cent alumina fireclay brick. The one serious factor preventing its more general use its high price, which the same order as, though somewhat less than, that most basic refractories. The end walls reheating fur- naces are usually just doors. The refractories used for bricking them THE IRON AGE, July 23, 1942—39 ° ° ° 5 q vary widely with the precise con- ditions existing the furnace. Where these are not particularly severe, light-weight structed from high temperature in- sulating brick are sometimes used, but medium high alumina fire- brick are more commonly employed. Doors can also constructed ramming insulating refractory concrete into door frame either with without reinforcing, while lids made this way have also been used with success soaking pits. The technique preparing such refractory concretes has been dis- cussed Hussey and other au- raphy the end this article. general, firebrick high tem- perature insulating brick grog first soaked water mixed with about per cent Ciment Fondu together with suffi- cient additional water give the necessary set. After standing for day, the doors are hard and may dried out prior use. many installations, doors this type are preferred because the ease with which the material may rammed fill complex frame that would present com- paratively difficult problem the brick mason. the continuous slab heating furnaces, the refractory pillars sup- porting the water cooled skids have given great deal trouble be- cause the difficulty finding brick that combined high refrac- toriness under load with good spal- ling resistance. Super-duty semi- silica and high alumina brick have all, according Hite and Solar, been used quite successfully, but some plants recourse has been made water cooled U-supports. Causes Failure: Ideally, ingots should not rest side walls nor fall against them during charging. practice they often do, and account must taken this the initial construction. Thus has been found advan- tageous insert five courses the side wall few feet from the top, each course being stepped one TABLE Properties Miscellaneous Soaking Pit and Reheating Furnace Side Wall and Door Bricks Medium Sillimanite Type: Chrome-Silica Burner and Soaker Slag Line Brick Door brick Hearth brick Code No.: X.1 X.2 F.5 X.14 Apparent porosity, per cent 29.5 27.5 23.0 23.8 Bulk density gm. per 1.95 2.06 1.98 per cu. ft. 122 129 124 146 Apparent specific gravity 2.84 2.58 3.06 Crushing strength, end, per sq. in. 1360 1950 4110 3380 Permeability air, c.g.s. units, perpendicular, 9x3 in., skin 2.13 1.93 0.0086 0.025 After contraction hr. 2570 deg. (Exp) —0.1 (Exp) —4.8 (Exp) —0.05 (Exp) hrs. 1500 deg. Pyrometric cone equivalent >30 n.d. (Seger) 3002 deg. 2858 deg. Over 3056 deg. Refractoriness under load Maintained temperature, 0.3 per cent failed per sq. in. hr. 2552 deg. collapse min. Rising temperature, Initial softening 2084 2732 deg. Rapid softening 2300 deg. F.| 2876 deg. Fail temperature 2624 deg. 3200 deg. 40—THE IRON AGE, July 23, 1942 inch order that the middle course projects several inches into the furnace. When the ingot falls against the wall, this course that takes the brunt the impact rather than the wall whole. Furthermore, this protrusion keeps the ingot off the wall during re- moval. The actual life obtained depends many factors, for example; the rate drive the furnace, wheth- coal gas firing employed. and how often the soaking pit cooled off order that can removed from the hearth. With some soaking pits this latter pro- cess far too vigorous, water be- ing employed cool off the slag with inevitable damage the side walls thermal shock and steam. With coal-fired soakers, the arch over the fire box exposed high temperatures and coal ash and hence the life may short even when high alumina fireclay brick silica brick are employed. the ordinary reheating fur- nace, working say 2192 deg. the wear slight and side-wall life year more not un- usual. such furnaces, the charge rarely comes into contact with the walls and the atmosphere gener- ally quite clean. might ex- pected, furnaces operating continu- ously with slow heating and cooling schedule show markedly longer lives. Lines Improvement: Here again the possibility im- proved life seems much matter design material. Where walls show instability, small changes design, for example, from straight wall slightly convex one, may avoid loss shape; while extreme cases some type tied-in construction such employed for suspended roofs might well prove worth while. The Hearth Construction and Materials: the hearth temperature high, 2192 2372 deg. F., and there considerable scaling, monolithic top hearth often pre- ferred, particularly the charge pushed over the hearth and tends grip and dislodge any brick whose edges protrude even small amount above the general level. Several courses material are often em- ployed. soaking pits the hearth may consist monolithic section perhaps plastic chrome, resting medium alumina fireclay brick course, which turn rests in- sulating brick concrete. Coke breeze often used top the plastic chrome absorb some the molten scale and prevent ingots sticking the hearth. Another type construction employs monolithic hearth basic calcined dolomite resting sub-hearth either chrome stabilized dolo- mite brick. some soaking pits considered more economical build the hearth low grade fireclay brick and renew frequently required. reheating furnaces, firebrick hearth usually adequate and this generally rests layer insu- lating brick concrete. If, how- ever, the temperature sufficient result considerable scaling, then basic hearth more econom- ical. Attempts have been made heat billets forging temperatures fireclay hearths, even con- tinuous furnaces, but the results have often been disastrous with furnace which should have run for several months having been put out action few davs the slag from the billets had bitten into the hearth until looked like ploughed field. Where this severe attack occurs, recourse must had basic neutral hearth such IG. soaking pit un- der construction. (Courtesy Salem Engineering Co., can made with magnesite, chrome magnesite, stabilized dolomite brick. The peculiar shapes such hearths, such the circular “tunnel kiln” type furnace, make easier and cheaper use chrome plastic. Fortunately materials are avail- able that will this job quite satis- factorily. There are two main types. The first consists essentially chrome ore ground pan mill with small amount water-glass and sometimes other bonds such clay; while the second consists chrome chrome-magnesite mix- ture bonded with about per cent Ciment Fondu. The first type bricks are sealed tins under number brand names and simply reauire placed the hearth and tamped into posi- tion. Since they contain water glass, which tends form skin drying, considerable care must the steam formed during drying and heating-up will cause disruption the working face. Such venting conveniently done prick- ing the surface intervals with pointed rod. The Ciment Fondu type material supplied the dry condition and mixed with suitable amount water, usually about per cent, and rammed position the hearth. carry- ing out such ramming, which also done with other hearth mix- tures such chrome, magnesite, sulphite lye, and iron borings, the use wooden shuttering essen- tial since otherwise the material tends flow under the rammer and good compacting not obtained. The Ciment Fondu hearth can dried out rapid rate after has had hr. which set, and yields excellent hearth for use contact with scale. With both types material, the proper grad- ing the batch first essential, and this may obtained either sieving out and re-mixing the con- stituents controlled pan mill- ing. One type grading found give excellent results the per cent coarse, per cent medium, and per cent fine type grading already referred connection with induction furnaces. THE IRON AGE, July 23, | ° ° ° l l position which the chrome plastics have given excellent service and which, present, ade- quate substitute appears avail- able, the finishing zone the triple fired two-zone continuous type ‘slab reheating furnace, re- ferred the introduction and illustrated Fig. Here the large slabs temperature suitable for rolling are pushed off the water- cooled skids the preheating zone chrome plastic hearth. This latter therefore subjected not only contact with scale but also severe abrasion. spite the difficult operating conditions, good chrome plastic will withstand through-put 600 tons slabs per day for periods year more. certain special purposes, such the reheating stainless steel sheets, where any reaction between the brick and the metal has deleterious effect the final fin- ish, sillimanite sometimes used. Its principal advantage that higher temperature required than with firebrick before reaction with dry mill occurs. Causes Failure: The greatest difficulty with the soaking pit hearth the removal the molten scale which drips from the ingots. Many soaking pits are fitted with through which the should drained, but some plants this never used because the superheat the scale in- sufficient permit efficient drainage and the tapping arrange- ments are for from ideal. has been found that drainage from fireclay hearths can facilitated sand fireclay bricks onto the hearth prior use. The molten scale reacts with this form very fluid material, re- sult which might have been predict- SiO, diagram, the lowest melting points which are obtained when about per cent present. other plants the soakers are periodically shut off and after cool- ing with water the “bulldog” fused scale broken and taken out. undeniable that such procedure has bad effect the life the soaking pit refractories, but some method removing the scale has employed and any case the finds ready market which compensates some extent for the damage done. With reheating furnaces oper- 42—THE IRON AGE, July 23, 1942 ating low temperatures, the hearth presents serious problem although does ultimately have renewed due abrasion the charge. With furnaces operating under conditions which the scale molten pasty, problem exists which still far from solved. The scale losses are the order per cent even the most modern type furnace, and proportion this scale adheres the hearth extremely dense and tough layer. This soon builds inconveniently great height and most furnaces this type some method descaling the hearth employed, often during week-end shut-down. The result, from the standpoint the refractory manufacturer, most unsatisfactory since mat- ter how well his refractory has withstood attack molten scale, may badly damaged during the removal the adhering layer. There considerable difference opinion whether brick chrome plastic least damaged this process, and doubtless these differences depend real differ- can only stated here that for some furnaces better results are obtained with chrome plastic than with, say, chrome chrome mag- nesite brick, while with others the opposite true. Lines Improvement: The outstanding problem there- fore regards the hearth the method removing preventing the adherence molten scale from the ingots billets. The present methods represent tory compromise and would better work with really fluid slag which can efficiently tapped off, employ some device en- able hard scale removed with- out damage the hearth below. Thus, recent reheating furnace trials has been found that stabil- ized dolomite brick can protected brushed off the hearth soon becomes slagged with scale. Flues might anticipated that flues, which frequently contain reducing gases and which are built from common firebrick, would subject like the brick blast furnace stack disintegration carbon deposition. any such disintegra- tion does occur, must very slight scale since the life even low medium alumina fireclay brick this position generally matter years. Both soaking pits and reheating furnaces may equipped with regenerator recuperator system that the sensible heat the exit gases can recovered preheat the incoming air. Where regen- erators are used, they are essen- tially similar type those em- ployed with the open hearth fur- nace and may even fitted with slag pockets. The conditions gov- erning the selection the refrac- tories are also similar and will not therefore re-discussed. should, however, pointed out that the temperature the exit gases general far below that open hearth furnace and that there much lower concentration dust the atmosphere. Hence, con- siderably longer life may ex- pected than obtained with open hearth furnace checkers. Recuperators may built variety the main aim being recover waste heat passing the exit gases through tubes hollow tiles the chimney flue and bringing the air for pre- heating over the outside these tubes, generally direction right angles. With soaking pit re- cuperators, hollow fireclay blocks are often used together with tiles, but considerable use has been made with reheating furnaces recuper- ators built with either silicon car- bide metal tubes. The high con- ductivity silicon carbide brick, about times that fireclay, and metal make for very efficient heat transfer. The utility carbide the steelworks the moment limited, but its peculiar properties make extremely suit- able for this particular purpose. addition this high conduc- tivity, has very high refrac- toriness under load and made with very low permeability. has been stated that even 2462 deg. its compressive strength the order 10,000 per sq. in. Furthermore, shows unusually high thermal shock resistance. All these properties mark out material peculiarly suitable for re- cuperator construction. The stand- ard tube developed for this purpose ft. in. long, and has ex- ternal diameter 5.75 in., and internal diameter 4.10 in. Cylin- drical fireclay rods, known “core busters,” are placed the tubes give high turbulence the gases and thus promote efficient heat transfer. said that reheating furnaces equipped with recuperators possess number advantages over re- generative system and particular enable much more constant tem- clear that the preheated air can supplied fixed temperature, then both fuel and atmosphere con- trol will much easier. Acknowledgment pressed Dr. Swinden, direc- tor research, for permission publish this article; the publicity department the United Steel Companies Ltd., the Detrick Co. Ltd., and the Salem Engineer- ing Co. Ltd., for supplying illustra- tions, and numerous friends the steel and refractories industries for their constant assistance. Bibliography Exclusive reference included under sections dealing with “Materials” General: Bent., Journal Iron and Steel In- stitute, 1938, 138, 11, 397. Etherington, Furnace Portable Spray Booth for SPECIAL portable Binks spray booth, made specifically for this operation the Ryan Aeronautical Co. factory, equipped with exhaust system carry away the spray and fumes while painting the interior train- ing plane fuselages. The booth may moved down the fuselage production line, the fuselages their “move can brought the special spray unit. Technclogy,” Charles Griffin Co., Ltd., London, 1938. Havard, and Fur- naces,” McGraw Hill Book Co., New York, 1912. Hermann, “Industrial Furnace Technique,” Ernest Benn, Ltd., Lon- don, 1929. Hite, and Soler, Brick and Clay Record, 1940, (1), 62. 1940, (3), 57. Inman, and Wainwright, British Steelmaker, 1939, 277. Morton, and Steel Engi- neer, Jan. 24, 1938, 15. Norton, Transactions Electro- chemical Society, 1939, 75, 123. Peters, Rolling Mill Journal, February, 1931, 109. Shack, “Industrial Heat Transfer,” John Wiley Sons, Inc., New York, 1933. McDowell Spotts, and Gill, Steel, 1938, 102, (17), and (20), 48, 55. John Wiley Sons, New York, 1934. Watts, Steel, June 17, 1935, 96, 30. Soaking Pits: Anon., Steel, July 18, 1936, 66. Fiske, THE IRON AGE, Dec. 1936, 138, 52. Gillies, and Martin, Jour- nal and Steel Institute, 1938, 138, 11, 319. Hollinger, Steel, March 22, 1937, 100, 41. Jenkins, Steel, March 1936, 98, 64. Longenecker, Blast Furnace and Steel Plant, 1937, 25, 995. Mawhinney, and Steel Engineer, April, 1936, 13, and June, 1936, 13, 26. Iron and Steel Engi- neer, June, 1935, 12, 369. Morton, Steel, 13, 1937, 101, and 80. Rees, and Lynam, Trans- actions Ceramic Society, 1936, 35, 138 and 153. Coal Ash Attack: Endell, Fehling, and Kley, Journal American Ceramic So- ciety, 1939, 22, 105. Fehling, Feuerungstechnik, 1938, 26, 33. Fettke, and Stewart, Car- negie Institute Technical Coopera- tive Bulletin Mining and Metal- lurgical Investigations, No. 73, 90, 1936. Moody, and Langan, Com- bustion, 1935, (8), 13. Refractory Concrete: Chadeyron, and Rees, Re- fractory Materials Joint Committee Institute Gas Engineers, 28th report, 1937, 76. Coutant, Blast Furnace and Steel Plant, 1937, 24, 1142. Hussey, Chemical and Industrial Metallurgy, 1937, 56, (3), 53. McGrue, Blast Furnace and Steel Plant, 1937, 25, 624. THE IRON AGE, July 23, 1942—43 ery ven lay lly ing xit eat en- en- ur- ith ac- not the ust re- re- | ~ - — — — | Advances Electric Welding Tubes requirements the war program for large quantities steel tubing have stimulated interest improved methods producing tubing all types. weld mills with their adaptability for producing large range tubing sizes, particularly those with diam- eter and wall thickness below the capacity seamless mills, are ad- vantageous when seamless mills are working capacity and unable meet all requirements. The expiration the basic pat- ents electric resistance weld methods 1938 has tended stim- ulate development newer types machines embodying improve- ments leading higher mechanical and electrical operating efficiency, particularly the methods conveying the welding current the point contact the welding electrodes and the tube. Older types welders ordinarily necessitating the use rather long flexible leads from the tranformer the point where the high amper- age current could transferred the welding electrodes means brushes. the original Par- part machines, the bearings sup- porting the electrode roll shafts, the other hand, were the point entry the welding current the electrodes. These designs were recognized being inefficient due current losses, and required high maintenance because maintain good bearing surfaces, since adequate