The Iron Age 1936-09-17: Vol 138 Iss 12

PORTANT WORK DONE HERE THIS Hoskins Furnace the plant the Mechanics Universal Joint Co. There used for the heat- treatment important and delicate tools, and for tests establish their carburizing practice. Mr. Waisner, metallurgist, says the main advantage the furnace for this work its Thru-out the metal working industry, Hoskins Electric Furnaces are use where heat-treating facts must known, and results must certain. heat-treatment vital you, find Catalog 55(T) useful. Send for copy Hoskins Mig. Co., Detroit, Mich. 2—THE IRON AGE, September 1936 THE IRON AGE, published every Thursday the CHILTON CO., Chestnut 56th Philedelphia, Pa. Entered second November 1932, the Post Office Philadelphia under Act March 1879. $6.00 year S., Canada $8.50, Foreign $12.00. Vol. 138, No. 12. FRITZ J. FRANK President VAN DEVENTER Editor Managing Editor Editor Emeritus Machinery Editor Art Editor Metallurgical Editor Associate Editors Resident District Editors Washington Chicago Cleveland Detroit Pittsburgh Editorial Correspondents London, England Cincinnati Boston CHESTNUT AND STREETS, PHILADELPHIA, PA. Hamburg, Germany SANDERSON ASA ROUNDTREE, JR. ALLISON Sales Offices Toronto, Ontario Birmingham, Ala. Newark, 239 WEST 39TH STREET NEW YORK, Roy TURNER St. Louis Buffalo Conten 17, 1936 Steel and Electricity Partnership Electricity and Progress the Steel Industry Superposed Generators for Steel Electrification Hot Strip Mill Drives................. Electrification Cold Strip Mill Electric Equipment for Steel Mill Auxiliaries Electric Heat-Treating Furnaces Steel Mills Open-Hearth Stainless Stee! New Equipment Automotive Industry Statistics Metal-Working Activity Rate Activity Capital Goods Washington News NEWS CONTENTS Owned and Published Products Advertised Index Advertisers 182 CHILTON COMPANY (Incorporated) Copyright 1936 Chilton Company (Inc.) Chestnut and 56th Sts., Philadelphia, Pa. BAUR, General Advertising Manager MUSSELMAN, President DIX, Manager Reader Service FRITZ Executive Vice-President Member, Audit Bureau Circulations ADVERTISING STAFF JOSEPH HILDRETH Indexed the Industrial Arts Index. and Chilton Chestnut Published every Thursday. Sts., Philadelphia, Pa. GEORGE tion Price: United States and Pos- Hottenstein, 802 Otis Chicage EVERIT BR. TERHUNE - sessions, Mexico, Cuba, $6.00: Can- Peirce Lewis, 7310 Woodward Ave., Detroit ada, $8.50, including duty; Foreign Ober, 239 39th St., New York ERNEST HASTINGS, $12.00 year. Single copy. cents. Robinson, 428 Park Pittsburgh Cable Address, ‘‘Ironage, Warren, Box Hartford, Conn. WILLIAM BARBER, Treasurer = - atter ASSURANCE REGARDING DELIVERIES Depend Ryerson for Immediate Stock Shipment your production schedules—make sure steel deliveries drawing the largest and most diversified stocks steel the country. More than 10,000 sizes and kinds steel and allied products are carried the ten Ryerson Steel-Service plants, strategically located for quick delivery throughout the principal industrial areas. Special handling, cutting and dispatching facilities assure prompt ship- ment every order, large small. Josenh. Ryerson Son, Inc., Chicago, Milwaukee, St. Louis, Cleveland, Cincinnati, Detroit, Boston, Buffalo, Philadelphia, Jersey City Don’t Worry About Steel Deliveries ...You Can When you need steel, draw the nearest Ryerson plant. 32—THE IRON AGE, September 1936 | } > ‘ a » J pat SEPTEMBER 1936 ESTABLISHED 1855 Vol. 138, No. Steel and Electricity Partnership HIS issue The Age keynoted tune with the annual convention and exposition the Association and Steel Engineers, held next Tuesday and Wednesday the Hotel Statler Detroit. Advances steel production technique, notable indeed dur- ing the past years, have been made possible largely the fact that steel and electricity have formed technical partner- ship. the design, construction and operation our modern mills, not think steel mill and electrical apparatus separate entities but coalescing components with the common objective more and better steel. Few realize how close this partnership is. Therefore fitting this issue present picture it. This has been done for and for our readers, and think done very well indeed, group engineers the General Electric Co., each whom has dealt with that division steel equipment electrification with which has been most inti- mately associated. Readers The Age whose activities are steel production will find this series immediate practical value; those who are engaged other occupations will find remarkably interesting modern mechanization. Suede Six authors have contributed this survey. Umansky, Darling, Mohler, and Otis are the industrial the General Electric Co. Schenectady. Rhea with the industrial department the company Pitts- burgh, and Fairman, Jr., associated with the switchgear Philadelphia. All these gentlemen are well known the steel industry. have complete that steel production technique will continue improve accelerating pace. And one reason for this belief the unlimited future its partner, electricity. ; a he hal 2 Sa ia THOSE engineering memory goes back years more very vividly the heated arguments be- tween the proponents steam vs. electric power driving medi- for steel-mill machinery. The issue has been settled. has won the battle. Every single drive in- stalled these years has been driven mills have been electrified. modern rolling mill, such hot cold strip mill, simply could not exist without electric drives. Strip, know now, simply could not produced And would the steel industry with- out strip mills? The field auxiliary drives and cranes was conceded elec- tric power long ago. Progressive steel companies are solving their mill transportation problems with oil-electric locomotives. Whenever the steel product has heat- 34—THE IRON AGE, September 1936 ° UMANSKY treated and quality the product important, electric furnaces are considered. sure, there yet keen competition this field between electricity the one hand and gas and oil fuel the other —just years ago there was competition between electric- ity and steam for driving rolling But the trend seems quite evident: for fine quality product, for the consistency results possible with electric heat, for elimination retreatments, for best all-round economy, there equal the electric method. But electricity did not chase steam out the steel plants; the contrary, has enhanced its value. Electricity itself duced steam. The latter has been merely assigned tralized power-house where can produced and used most effi- ciently. The makers machinery have, the same time, developed steam turbines once unthought-of heights. Steam pres- sures have been raised 1300 lb. per sq. in., 900 deg. F., and the amount coal per kilowatt-hour generated slashed half. The superposed steam cycle brought these econ- omies within the reach even those plants where the existing steam-generating equipment has maintained. Thus uted the modern steel plant know today. Some proc- esses could not exist all without it; others could not eco- analysis, practically the same thing. number years ago elec- tricity and steel were joined to- gether for better for worse; know now that was for the better. | .. “4 SHORTLY September, 1934, meet- ing Cleveland the Association Iron and Steel Electrical Engineers, before steam turbine generators was pre- sented, several steel mills began investigations their steam and power conditions. Since then, least two large steel mills have concluded that, for their condi- tions, they can best served high-pressure bine generators exhausting into the existing steam mains which are usually pressure be- tween 200 and 300 per sq. in. Other plants are interested the possibilities offered the plan and, when business conditions be- come somewhat more favorable, will probably begin active consid- eration superposed turbine gen- erators. What the underlying reason Steam Turbine Gener- ator Plants for the Steel Darling. # UBSTANTIAL savings daily coal consumption are being effected the Rouge plant the Ford Motor Co. through the use this 15,000-kw., noncondensing turbine generator recently placed service. THE IRON AGE, September 17, 1936—35 > get the Weirton Steel Co. this 10,000-kw. noncondensing turbine-aenerator (foreground) has been service long enough justify the expectations held for it. for this evident. interest the part steel mills their steam plants? Surely the advances made the uses electricity have diminished the necessity for steam- driven mills. Agreed. Yet there still remains heavy demand for low-pressure steam for blowing engines and turbines, pumps, etc., which either have not exhausted their durability or, because the nature their service, cannot economically changed electric drive replaced higher-pres- sure designs. the same time, new mills and other services, all requiring electric power, are being installed. What then, using the facilities hand, the economical way meet this dual requirement for low-pressure steam and elec- tric power? The principle using steam more than once, the course its expansion from high low pressure, not new. The double- and triple-expansion engines con- stituted one the first applica- Boiler High-Pressure Non-Condensing Low- Pressure Condensing Steam for Plant and Mechanical Uses tions obtaining multiplicity mechanical services The first engines were noncondens- ing; did not take the mill operators long find that they could advantageously use the heat the exhaust steam for processes and for heating Steam condensers were developed get more mechanical power from the condensation the vapor when there was insufficient de- mand for the utilization the latent heat vapor other mechanical, process, building- heating uses. high-pressure boiler installa- tion not necessarily more effi- cient than one but, when plurality se- quential services can obtained from higher-pressure vapor than practical from lower-pressure vapor, marked economy opera- tion possible since new con- densing equipment with its heavy heat losses involved. This the principle upon which the ap- Plant Electrical load schematic dia- gram illustrates the general principle em- ployed posing turbine pressure plant. Low-Pressure Steam for Plant Process and Building Heat 36—THE IRON AGE, September 1936 plication condensing turbines based. Their application generally most feasi- ble when additional boiler capac- because lack sufficient lower- pressure boilers because the existing boilers’ being inefficient derated aging. The choice the top pressure dependent upon the relation cost noncondensing steam tur- bine stations and the useful energy produced various pressures them are shown the accompanying graph. — a- + - + + 1.4 + + + + | heat usages. electrical power demand large and the exhaust-steam requirement low, the top pressure should high. Conversely, for small electrical de- mand and high exhaust-steam re- quirements, the top pressure should reduced obtain that heat balance which has the least losses. The Weirton Steel Co.’s 10,000- kw. 800-lb.-pressure noncondensing turbine-generator installation has been operation long enough justify the expectations held for it. Requirements for 250-lb. steam the Rouge plant the Ford Motor Co. Detroit were more than sufficient warrant the in- stallation unit, operating 1225-lb. steam pressure and 250-lb. back pres- sure, which recently went into ser- savings coal consumed daily. Youngstown, the Youngstown Sheet Tube Co. making prep- arations for the installation 7500-kilowatt unit. and from the experience made avail- able existing installations, reasonable expect that, the future, mills which added boiler capacity electrical power and have use for mod- erate-pressure steam will give careful consideration the appli- the high-pressure non- condensing turbine exhausting in- their existing steam mains. LECTRIC drives for roughing stands 96-in. hot-strip mill. Each stand driven constant speed 3,000-hp. induction motor equipped with flywheel. Stands set far apart, that slab more than one stand simultaneously. Installed 1936. ° ° UMANSKY ° the several ing built around years the steel industry has concentrated its at- tention flat-rolled products such sheets and tin plate. Better and better product, lower and lower cost, has been the motto. Rolling proc- esses and mill machinery have been undergoing quiet but swift and comprehensive revolution. Its end not sight yet, but the general trend apparent. Continuous semi-continuous hot-strip mills are gradually dis- placing the sheet bar mills and the old-fashioned sheet mills. great extent the new mills are be- equipment. The latter longer merely attached the rolling ma- chinery—it becomes part it. There considerable differ- ence thoughts and designs far arrangement the rough- ing end continuous hot-strip mill concerned. Some favor ‘reversing universal stand with motor-generator set, and reversing control. This arrangement highly flexible, since the number passes can readily adjusted suit the requirements. The me- chanical equipment the least ex- pensive one and requires the min- THE IRON AGE, September | | imum space. the other hand, the electric equipment relatively more expensive and_ elaborate. With this layout the roughing mill usually limits the tonnage. with tilting tables conceivable, but new equipment this type has been proposed and built. were important keep the cost electric drive down, constant- speed induction motor with fly- wheel could applied—just this done for three-high plate mills. the majority cases, several roughing stands arranged tan- dem are used. They may set together, each stand driven This very compact arrange ment but requires expensive electric apparatus. the other hand, the roughing stands may set sufficiently far apart that the same slab never two stands simultaneously. Speed re- lationship the several stands 38—THE IRON AGE, September 1936 Tips room 79-in. hot-strip mill. Finishing stands driven two 4,500-hp., three 3,500-hp., one 2,500-hp., and one 500-hp. d-c. motors. Power furnished 6,000-kw. motor-generators. Stands very closely spaced. Installed 1935. ° ° not contingent upon the draft. Thus each stand may separatel) induction synchronous motor. This usually results the least expensive electric equipment. present the tendency this arrangement, particu- larly for wide mills, where spreading stand with slab turn- arounds common. The arrangement the finish- ing stands and their drives has LECTRIC drives for 38-in. hot- strip mill. All the ten tan- dem stands, roughing and finish- ing, are set close centers and driven d-c. motors totalling 20,000 hp. Installed 1930. taken almost-standard form. The several stands are set tan- dem, rather close centers. Ad- justable-speed drives, one for each stand, are essential. Nothing but d-c. motors can readily answer this purpose. wide mills, say 96-in., drives high 4500 hp. employed. Not less than 2:1 speed range motor field control provided. D-c. power conven- tionally supplied several syn- chronous motor-generator cated close by. The concentration power limited space tremendous. The rating the electric machinery for the finishing stands alone may easily aggregate 75,000 hp. (in- cluding the motor-generator sets). Yet the electric circuits are laid out that single operator the mill pulpit easily holds this power under his control. Speed relation- ship between the several stands changed few seconds suit any conceivable rolling schedule. The flexibility such that even ABOVE equipment built for large reversing slabbing mill feeding continuous hot-strip mill. Each the horizontal driven separate 5,000-hp. mo- tor; the vertical rolls 2,500- hp. motor. small special orders, each compris- perhaps only few slabs, can economically rolled. Thus large and expensive mill ceases specialized unit. becomes versatile and universal tool eco- nomically covering large range products. Flexibility the elec- tric equipment makes this possible —and the return each dollar invested increases. Substantial yearly tonnage is, strip mill which calls for invest- ment possibly $15,000,000 more. small producer flat- rolled steel facing quite prob- lem. has produce strip stay the field; his potential market may not justify the large mill. Several attempts have been made solve this problem util- izing single-stand reversing hot- strip mill with coiler each side. Since the strip builds the coilers, separate drives for the mill, each coiler, tables, are essential. Yet all these drives must properly synchronized with each other, lest the strip damaged. This calls for precise electric con- trol. some cases only the finishing passes are made such mill, the roughing work being done, for instance, preceding universal plate mill. other instances both the roughing and the finishing work done single stand. Several mills this type are service. ABOVE "nerve and blood system" hot strip mill: the high-interrupt- ing-capacity air circuit breakers and bus located base- ment aisle between the finishing motors and M-G sets. ° ° ° RIGHT PERATING pulpit wide-strip mill. Fin- ishing stands are started, stopped, reversed, and their speed one oper- ator. rolli practical results alone. The drive and suce process would not feasible the electrical machinery and control were not available. cold- strip mill practice the electricians become mill operators. Several years ago tin plate and The commercial this method can measured its control are unqualified ess. Needless say, the whole 7 = sheets were conventionally rolled from sheet bars, and the latter from blooms. Wide hot-strip mills require slabs for the same purpose. Steel plants are checking their blooming-mill capacity and are in- creasing the ratio slab bloom tonnage. For very wide slabs, in. so, universal slabbing mills with separately driven ver- tical rolls are being favorably con- sidered. increased activity this line may expected pres- ently. this respect should mentioned that electric equipment for slabbing mills being further developed and refined, partly for the purpose simplifying the ar- rangement and maintenance mechanical equipment. There definite and healthful change the attitude toward the electrical equipment the part mill operators. was not uncom- mon the past lay out mill without any regard the electric machinery, almost forgetting leave adequate space for it. Now- adays, progressive steel company arranges the motor rooms and substations with much thought and care the building proper. The motors and contingent equipment are properly housed, kept clean, the most certain way keeping the maintenance costs low. This change attitude can readily understood since electrical equipment has become more in- tegral part the mill machinery than ever was before. motor room for large hot- strip mill may 600 ft. long much 100,000 hp. more rotating machinery may easily concentrated this floor area, average about three hp. per sq. ft. the finishing mill this figure rises more than hp. per sq. ft. The losses contingent the transformation power mechanical, small though they are percentage basis, may amount 4000 kw-hr., close 14,000,000 B.t.u. every hour. The heat thus liberated pumped out the motor room. This itself quite engineer- ing problem but modern motor rooms several ways solving this employed. Mention has been already made the tremendous concentration power the finishing stands wide high-speed strip mill. The several d-c. generators and mill 40—THE IRON AGE, September 1936 motors are usually tied com- mon 600-volt bus. For obvious rea- sons the connections between the machines and the bus are made short possible, with practically negligible electrical resistance. emergency short circuit should develop somewhere this 600-volt system, the large ma- chines may into fault sev- eral hundred thousand amperes. protect the equipment against pos- sible damage, special air-circuit breakers are employed which are unusually fast action and very high current-interrupting ca- pacity. The bus best arranged structural shapes, copper ° ° MOHLER THE electric equipment strip mill. forms integral part the mill just much the rolls and bearings. The part the electric equipment will play and its possibilities should carefully borne mind when designing the mill. even more importance, the functioning the electric equipment determines great extent the methods rolling, the rolling practices, the production the mill, and the results obtained. The evolution the skin-pass tempering mill gives good illus- tration the part played elec- tric equipment. The early skin pass mill consisted merely pair rolls which were driven constant speed any motive power available. The strip was cut into sheets and passed through the mill one time. Sometimes the sheets were passed through sev- eral times order get the de- sired result. Then was found that adjust- able speeds were very desirable be- cause some products could rolled faster than others advantage. This necessitated the use the ad- justable-speed d-c. motor. This step not only increased the flex- ibility the mill, but increased its production. The next step was skin-roll strip, allowing fed into the mill from loose coil box, pass through the mill and wound reel drum. Slip clutches and comparatively light tensions were first used, but was soon dis- covered that greater reductions, flatter strip and gage could obtained using relatively high and constant ten- sion. This lead the development regulator which would control adjustable- speed d-c. motor that approx- imately constant tension was main- tained irrespective the changing diameter the coil. Further- more, because the variety products rolled wide range tension adjustment was found de- sirable and provided. Soon the loose coil box was re- placed with feed reel consisting two cones, each equipped with electric drag generator, for maintaining constant back tension. Again was possible increase the percentage reduction mill. Here again regulators were required maintain the tension constant. When coil strip wound under tension, each additional wrap places the inside turns under greater compression. Thus was found that when the desired ten- sion was used skin temper rolling very thin strip, such tinplate, the coil would collapse soon was kicked off the reel | ax ° ° ° | aluminum, and sturdily braced against the disturbing mechanical stresses resulting from high short- circuit current. The bus, breakers, contingent equipment are usually located the basement tween the foundations the fin- ishing-mill motors and motor-gen- drum. This led the addition pair tension rolls between the mill and the winding reel. rela- tively low tension was then main- tained between the tension reel and tension rolls, and much higher tension between the mill and ten- sion rolls. Each these tensions had independently adjustable over wide range and then main- tained constant. annealed coil usually rather loosely wound and too much back tension causes slippage and scratching. order relieve this and yet employ higher back ten- sions, tension rolls have lately been added between the unwinding feed reel and the mill. These func- tion similarly those the de- livery side the mill. Thus skin-pass mill has devel- oped from simple pair rolls, mill consisting pair work- ing rolls, tension reel, set delivery tension rolls, set entry tension rolls, and feed reel each adjustable-speed d-c. motor, except the case the feed reel which requires two generators. Four regulators are required for maintaining tension between the various units. addition the mill must ac- celerated and decelerated the beginning and end each coil and approximately maintained. Exact synchronism must maintained between all five motors during this time; other- wise the strip would either break become sleck between them. erator sets. casual visitor to-a strip mill motor room may not even suspect that immediately be- neath his feet are located the “blood and nerve system” the whole mill. might seem some that the hot strip mills and their electrical equipment have reached their ulti- Smooth acceleration and decelera- tion obtained using separate motor-generator set ing and decreasing the d-c. voltage applied simultaneously all drives HREE-STAND 54-in. tandem cold mill, each stand driven motor and tension reel 400-hp. motor. Strip tension between stands automatically con- mate development—for few years least. Possibly this so. But more probable—as has been the case most other indus- tries—that progress this field will continue unabated, spurring mill operators and equipment man- ufacturers towards even greater achievements. means motor-operated rheo- stat. Compensation for the inertia each machine the mill auto- matically applied during accelera- tion and deceleration that ap- trolled tensiometers. THE IRON AGE, September proximately constant tension maintained. The roller operator must also provided with means for jogging inching each drive individually and independently, either forward reverse, when threading and clearing the mill. struments, control switches and rheostats must not only provided for controlling the numerous individual and collec- tive operations but must con- hand when the operation should performed. other words the de- signer the electric equipment must have complete and thorough knowledge the complete rolling practice and know every motion the roller goes through while oper- ating the mill. Skin-pass mills are usually con- sidered the simplest mills from electrical standpoint, the single tandem mill next complication, and the reversing mill the most these latter mills. well, the various units must driven motors, supplied with adjusta voltage, and the various units must controlled independently collectively Tension must likewise main- tained between all units and the for automatically controlling tension between stands tandem cold- strip mills. 42—THE IRON AGE, September 1936 OTOR room for 28-in. revers- ing cold-strip Visible are 800- hp. mill motor, one two 150-hp. reel motors, motor-gen- erator set, and con- trol board. same care and consideration must given the location control switches, instruments and tension- adjusting rheostats. Reference the accompanying illustration which show several the typical control panels required for these various mills will give some conception the number control functions required and the important part they must neces- sity play the manipulation the mill. They form the “brain and nervous system” the mill and when they cease function, the mill stops producing. must more science than “rule thumb” determined the skill and intuition the roller. has been found that the physical properties, finish and accuracy gage cold-rolled strip are con- trollable, least large extent. Rules and laws may discovered that, when applied scientifically, may broaden the field applica- tions for cold-rolled strip un- known limits. photomicrographs, and many other tests the results rolling can determined. However, order determine the laws rolling which produce these results, the various contributing factors must mea- sured. When they are measure- able, they are controllable. Electric equipment this means measuring. Electric strain gages measure and record the roll screw pressure; electric limit gages, the strip thickness; | re electric draft indicators, the per- centage draft; thermo- couples, the temperature the rolls and the rolling liquid; electric ammeters, voltmeters meters, the input the various machines; tensionmeters, the actual tension the strip and the level the mill. The last item, the tensionmeter, the newest addition. refer- ring the accompanying illustra- tion, will noted that consists primarily accurately ground roll supported anti-friction, self- alining bearings resilient bear- ing standards. Any motion the formers such manner that voltage obtained which di- rectly proportional the pressure the roll. Such slight move- ment the roll required give full range voltage that the inertia moving the roll can considered negligible. The voltage obtained can used both oper- ate instrument calibrated di- rectly pounds and operate regulator for maintaining the de- sired tension constant. brating instrument read the difference between the pressures each end the roll, the difference tension the two edges the strip can read directly. the difference zero, the mill rolls are level and the strip the same thickness both edges. believed that this device has tremendous possibilities, be- cause for the first time pos- ONTROL board for the 2,500-hp. and drives 84-in. tandem cold-strip cluding provision for tension control be- the stands. drag generator used for holding back tension feed reel. Unit complete with built-in speed reducer. Two such generators are usually applied feed reel. sible actually measure the ten- sion strip accurately; there- fore can controlled. Little known about the tensile strength steel “in flow” and this may the means making study this subject. There may critical optimum tension which steel should rolled that would revolutionize rolling practice and mill design. For instance experiment was tried both skin pass and reversing reduction mill which gave rather interesting results. The strip both cases was approx- imately .010 inches thick. The rolling load the mill motor was checked. Then the strip was re- moved and the load the mill motor checked again. The load both cases was approximately the same. This meant that practically all the work was being done the rolls themselves. This the major cause “spalling.” Next the front and back tension were increased enormously, yet not the breaking point. obtaining the same percentage reduction, the mill motor load was cut half. Obviously the working the rolls themselves and the strain the mill housing had been decreased. tensions can measured and controlled accurately, tensions can used nearer the critical limits. conclusion, believed that the instances cited the foregoing discussion will serve indicate, least some extent, how the elec- tric equipment has become indis- pensable part the cold-strip mill itself. THE IRON AGE, September 1936—43 4 3 RHEA every steel man knows, the motor and control equipment for auxiliary forms functions which are im- portant, relatively, the drive. The control functions re- quired for auxiliaries may indeed more complicated than the con- trol functions required for main drives. Space will permit the discussion only very few the auxiliary equipments which are already operation. Shears large number flying shears strip mills, sheet-bar mills, rod mills and the like have been suc- cessfully electrified. one case, electrically driven and controlled shear lo- cated immediately following the fin- ishing stand 43-in. hot-strip mill whose speed over 2000 fpm. the duty the shear drive auto- matically start from rest, cut off the front end adjustable defi- nite amount and continue cutting length. After the piece through the mill, the shear comes rest with the knives definite posi- tion ready for the next piece. The shear also arranged cut the front end only and then shut down without making additional cuts. the operator wishes crop the rear end only, this function can also performed. This particular flying shear 44—THE IRON AGE, September 17, 1936 geared the last finishing stand through adjustable gear ratio. The shear drum can discon- nected from the gear drive through knives are directly connected pair accelerating motors. The shear knives can thus remain rest, lying wait for the approach- ing strip, and then accelerated and clutched-in time take off the front end and continue cut length. somewhat similar flying shear operation 38-in. hot strip mill. Because the shear located some distance from the last finish- ing stand, gears and clutch the last stand are impractical. Likewise, occasionally desir- able drive this shear also from the next last finishing stand. ations, synchronous generator was geared each the finishing stands. motor drives the shear through the usual adjustable gear. This synchronous motor can thus geared electri- cally either the finishing stands. The electrical connection positive mechanical gear- ing. Furthermore, since the gen- erator connected the last stand has different number poles from the generator driven the next last stand, change electrical gear ratio effected the same time. interesting runout-table mo- tor application has been made this same mill which will de- scribed briefly later. entirely different type shear the bloom shear. this type shear, the metal rest the proper position between the blades. The blades are initially rest the raised position and are brought together, cutting the metal, and then separated means crank. This crank geared driving motor. Thus sary for the motor make one start and stop for each cut the metal. One such application for 350-ton bloom shear driven 200- hp. motor. This shear de- signed operate the rate cuts per minute. When the oper- ator presses the button, the shear through its cutting position and stops the initial position, dynamic braking. This arrange- equipped fly- 43-in. hot-strip 2,000 fpm. the front and a ing Max into ends ment eliminates the flywheel and mechanical clutch. the same plant, there also 800-ton bloom shear driven two 200 hp. motors, which also capable making cuts per minute. another large plant the midwest, similar shear for slabs driven two 275-hp. motors and supplied with adjustable potential control. This installation will discussed later. Squirrel-cage induction motors have also been applied this type start-and-stop crank shear when the frequency service much less severe—such for shears ing shear the finishing stand Maximum speed over uniform lengths merely crops ends desired. pickler lines where thin cold strip sheared and stitched. such drives, stopping position ef- fected solenoid brakes only and not the motor. Runout Table Drive the runout table following the modern high-speed hot-strip mill means line shaft and gearing because the high maintenance the bevel gears. All the modern high-speed strip mills have runout tables, the individual rolls which are driven individual squirrel- cage induction motors. These in- duction motors are supplied with adjustable frequency order obtain adjustable speed that the table may match the mill speed. the great number runout tables with individual-roll drives, few the types only can dis- cussed. interesting runout table application has been made the 38-in. hot strip mill referred above. The individual roll drives are squirrel cage induction motors built integrally with the roll. The rotating outer shell, which carries the hot metal, also carries the squirrel cage. stationary primary inside the roll. different arrangement run- out table drives applied the 43-in. 2,000-fpm. hot-strip mill pre- viously referred to. Each roll this runout table driven squirrel-cage mo- tor without gears. There total 237 motors this table. One interesting point concerning this application that the prelim- inary engineering stages this table was not supposed require start- ing and stopping with each piece. After the installation was com- pleted, however, was found con- venient start and stop the table for each piece. The motors suc- cessfully met this extra duty. Closely allied with the runout table are the coiler drives, also driven individual squirrel-cage motors each roll each pair rolls the coiler. The coiler for one 60-in. hot strip mill driv- squirrel-cage induction mo- tors which are interesting because their necessarily heavy and sturdy Each coiler driven five such individual motors. Since the coil- ers are subjected great deal water, the motors must totally enclosed and nearly water proof possible build them. Be- cause the motors are already sub- jected much splashing water, fan cooling extra water cooling necessary. has recently become the prac- tice some electrical manufac- turers assemble complete group auxiliary and control panels in- complete factory-assembled units. These units incorporate all the re- sistors, panels, buses and wiring and are assembled self-sup- porting structural steel frame work. The complete units are shipped their destination without disman- tling. Such assembled units save nearly per cent the time and labor that would other- wise required for their erection and wiring the field. Blooming Mill Auxiliary Drives The screwdown, side guards, manipulators and slab shear and live tables blooming slab- bing mill are among the hardest- worked auxiliaries steel mill. These auxiliaries are usually sup- plied with electrical power from the 230-volt shop bus and are con- THE IRON AGE, September 1936—45 & ; BELOW group panels controlling aux- iliary drives strip mill. This board type completely built and assembled with resistors and buses the factory and shipped destination without dismantling, thereby eliminating much per cent time and labor otherwise required for erection field. 46—THE IRON AGE, September 1936 LEFT 350-TON shear driven 200-hp. d-c. motor. Makes cuts per minute. Flywheel and clutch are eliminated. ABOVE EAVY-DUTY motor similar five which drive hot- strip coiler 60-in. mill. be fe | trolled means magnetic con- tactors. The maintenance such control relatively important item, but still more important are the delays which occur due the unavoidable failure this hard- worked control equipment. re- cent installation uses adjustable potential control instead magnetic contactor control for these auxiliaries. Each drive has separate generator. Each gen- erator solidly connected electri- cally with its motor and has inher- ent characteristics built into determined value. All control func- tions are performed the gener- ator fields and require only few very light contactors. One the principal benefits obtainable with this type system, addition greatly reduced maintenance, much higher speed when running light the screwdown—this being very important slabbing work. Generators built with these charac- teristics have been used for number years supply the drive electric shovels where ease and swiftness control reduction high maintenance have been necessary. Pickler and Cleaner Lines Auxiliary drives are often ar- ranged groups for collectively driving machine process. Such drives have interlocked and controlled group. good ex- ample such group auxiliary drives found continuous pickler line for hot-rolled strip. typical installation may consist such individually driven devices uncoiler, leveller and straight- ened, up-cut shear square the end the new coil, stitcher stitch the front end the new strip the rear end the pre- runout table following 43-in. hot-strip mill, each roller being driven direct-connected induction motor and total 277 motors being used the table. ceding strip, several individually driven pinch rolls feed and pull the strip through the acid and water tanks, another up-cut shear following the acid tanks cut out the stitch, and uncoiler ten- sion reel coil the strip. This in- stallation requires that provision made not only for individual jogging each drive but for con- trol the system whole. The synchronization the various mo- tors driving the metal through the pickler must provided, well dual and permissive control from each end the line. The control stations for this purpose may much 300 ft. apart. IRON AGE, September 17, | = all the electrical equipment ordinarily installed steel plants, there probably single class apparatus that pre- sents more important problem than the selection proper switch- gear. Experienced operators know that obsolete inadequate switch- gear can readily occasion partial total shutdowns. Over period the last five years the steel in- dustry has given increasing de- gree recognition the impor- tance properly coordinated switchgear equipment. Safety the operating personnel has become prime consideration well the necessity for assuring continu- ity production. For powerhouse and heavy-loop substation service voltages be- tween 2200 and 15,000 volts, mod- ern mill practice has indicated distinct preference for heavy-duty oil-circuit breakers mounted roll-out trucks cu- bicles. There distinct trend away from piecemeal assembly this apparatus “home cells and practically universal recognition the obvious advan- tages factory-assembled, test- 48—THE IRON AGE, September 1936 ed, and coordinated equipment en- closed steel. This has resulted saving installation time and expense, well affording maxi- mum safety instead the hazards operators and maintenance men encountered with types installations. For mill substations, such hot strip mills, cold strip mills, bloom- ing mills, the steel industry has indicated strong preference for vertical-lift metal-clad switch- gear involving oil-circuit breakers (with published interrupting ca- pacities from 100,000 kva HIS metal-clad switch- gear hot-strip mill motor room the type shipped from factory completely assembled, with instruments, relays, etc., ready installed and put service minimum time. 500,000 kva inclusive) the type having three phases one tank. The circuit-breaker element—which removable, with like ratings in- terchangeable, this type gear —is mobile and compact unit permitting easy manipulation and therefore facilitating rapid trans- fer breaker elements between the different stationary units the switching structure. This type equipment results maximum operating safety well assur- ance against mill delays. ma- jority the large mill-substation installations (particularly for strip mills) during the last five years have utilized this type gear for high-voltage switching. Various subsidiary units, such turbine-generator neutral-ground- ing circuits, synchronous- induc- tion-motor circuiting equipment, and various small pump circuits, have em- ployed single-tank oil-circuit break- ers mounted steel cubicles, the breakers being stationary. This type gear finds its usual appli- cation where the duty relatively light and the requirements for the rapid interchangeability break- units, provided vertical-lift j ° ° | ° ° ¢ metal-clad gear, has not been indi- cated. Cubicle gear this type has also received wide acceptance the smaller plants for providing switching. Where fewer than five circuits (ultimate) and breaker capacities below 100,- 000 kva are under consideration, this cubicle type gear has met with considerable favor. fundamental importance all applications high-voltage switchgear has been the availabil- ity oil-tight circuit breakers employing dependable, scientific means for controlling and rapidly extinguishing the are. The de- velopment breakers involving these features, coupled with recognition steel- mill requirements regards sturdy contacts, reliable ating mechanism, etc., has resulted more exacting standards for equipments withstand the severe repetitive circuit-breaker duty cy- cles incidental maintaining steel production with minimum chance delay. interesting observe that the modern note high-voltage switching equipment can sum- marized “built with steel.” The steel industry has done much establish this use steel which now rapidly becoming one the distinguishing marks mod- ern switchgear for other indus- tries. For switching service below 1000 volts—as, for example, d-c main-drive circuits, 250-volt d-c auxiliary service, and 440- 220- volt, 3-phase ab ~ EAR view 6,600-volt metal- clad switchgear for hot-strip mill. High interrupting capacity (500,000 kva) essential ac- count large concentration power steel plants. cuit breaker equipment em- ployed. For d-c service, attention has been centered upon extremely heavy-duty, pacity fast-operating mill-type air- circuit breakers. The design prob- lem incidental the finishing end large modern continuous mills with their enormous concen- tration large d-c machines has been the principal factor hasten- ing development and standardiza- tion air-circuit breakers for this application. Breakers are now available with published inter- rupting capacity 250,000 amp. 750 volts d-c, based the standard duty cycle “close- open” plus “open-close-open” with two-minute intervals between shots. The speed interruption not more than three cycles 60- cycle time wave from inception ruption the circuit, even for any current value from per cent 100 per cent normal breaker rating amperes and faster for higher current values. For 250-volt direct current, the heavy-duty air-circuit breaker, which reference made above, has also found preference large number installations. There distinct trend standardize the use automatic reclosing feeders for the protection the extremely important crane and auxiliary motor feeders. This type feeder equipment opens the cir- cuits when fault occurs and makes attempt reclose while the fault condition persists. How- ever, soon the fault re- moved the feeder recloses and re- stores service. This operation accomplished “feeling out” the circuit through resistor as- certain whether the fault has been closure. The low-voltage a-c service has tended toward more widespread use 440 volts, 3-phase, instead limiting the voltage 220 volts, 3-phase, was formerly more less ordinary practice. This has resulted better voltage condi- tions feeders and marked economy feeder-line construc- tion. The use 440-volt low- tension a-c has also permitted the elimination intermediate volt- ages below 6600 volts, 3-phase, number modern installations. Inasmuch motors which are too small economically consid- ered for 6600-volt operation may yet sufficient size repre- sent quite problem 220 volts, “no man’s land” thus created between the largest motor that can economically applied 220 volts and the smallest correspond- ing motor 660 volts. This sit- uation has more than once occa- sioned the use intermediate voltage (such volts) which can avoided altogether where 440 volts used for low- voltage power. THE IRON AGE, September 1936—49 . 250-volt switchgear large mill. All feeder breakers automatic reclosing type order minimize effect power interruptions. For this low-voltage a-c service either 220 440 volts, triple- pole air-circuit-breaker equipments have been widely applied. For major distribution points, mini- mum rating 1600 amp. has been generally accepted. Such in- stallations have employed electri- cally operated breakers and large number these feeders are provided with three-shot adjust- able-time automatic lays provide the maximum the way service maintenance important lines. For subsidiary distributions points, hand-operated air-breaker equipments, rated 1200 amp. 600 amp., are generally encountered. 50—THE IRON AGE, September 1936 striking feature all impor- tant d-c a-c construction below 1000 volts has been the trend to- ward the use structural shapes for heavy buses and connections. For all bus supports equipments, standard heavy-duty porcelain insulators are generally required. Accenting safety considerations well practical design require- ments, the disconnecting switches these equipments actually iso- late the entire circuit question from the bus. These disconnects are located back the switch- board, underneath the bus, and are provided with indicating lamps show the position the related air circuit breaker. This arrange- ment has met with wide favor for providing equipment especially suitable for steel-mill service. For high-tension low-tension control boards ment, secondary boards, meters, instruments, control switches, etc.) the use steel panel mate- rial has become versal. Steel for this purpose may used either the straight open panel familiar appearance may take the form so-called “duplex construction.” mentioned type permits indicating instruments and control switches, which must visible the oper- ator all times, mounted one face the board, while the other items, such relays, watthour meters, are located rear row panels. The two rows panels are mounted back back unit construction, thus facilitating completely assembled delivery minimizing unpredictable installation expenses. struction has been required for number power-house main con- trol boards well for the centralized control boards eral large mill substations. The progress that been made mill switchgear has kept pace and pressed forward with the requirements progressive industry. The number modern installations that have been made, during the last three years particular, has shown that alert steel-mill engineers have thorough- quirements and have solved them, particularly with respect switch- gear, manner most creditable their profession and the in- dustry they represent. ARGE station-type circuit breakers mounted cubicles, for service blast-furnace 000-kva. interrupting capacity. ELECTRIC furnaces are finding wide di- versity application steel mills, cially for the heat-treatment high-grade products, such alloy- steel bar stock, bright cold-rolled strip, bright tubes, wire, etc. The rigid specifications which these materials are required meet, not only single lot but from week week and month month, when large lots are ordered periodically specification, de- mand high accuracy the heat- treating operations and the repeti- tion cycles definite schedule. This particularly true ber stock and tubing and the furnaces developed for these purposes are good examples the progress made the heat-treating art tonnage basis. Fig. shows heat-treating plant for bar stock large east- ern steel mill, the equipment con- sisting continuous roller-hearth for normalizing and quenching, two rectangular type furnaces, each taking loads tons bar stock charge, and double-chamber car-type fur- nace for drawing. OTIS The continuous furnace particular interest. The tempera- ture controlled automatically, the time the bars the furnace controlled automatically tim- ing relays, and the bars are run out automatically and transferred automatically crane from the run-out table the quench tank, and the time the quench con- IG. electric furnaces for heat treating bar stock large Eastern steel mill. Automatic furnace for quenching and normalizing shown the foreground. THE IRON AGE, S