The Iron Age 1924-02-07: Vol 113 Iss 6

YY WY WY % bh ~ a Y Li tp Sy Y bir VOL. 113, No. 6 Deep-Hole Drilling in Large Lathe Success in Drilling Printing Machine Rolls Attributed to Boring Bar—Machining of Rolls Described Special Milling Attachments Developed been satisfactorily worked out at the plant of Walter Scott & Co., Plainfield, N. J., manufacturers of printing machinery, in the drilling of forged steel [tes problem of drilling parallel deep holes has Fig. 1. (Above) Rolls of 0.40 Carbon Steel Are Drilled To Depth of 45 In. The lower right hand roll shows one side finished, two holes having been drilled, a slot planed, and the remaining material between holes removed with an end mill Fig. 2. (At Upper Right) A Special Boring Bar With Two Oil Tubes and Chip Clearance Is Used Fig. 3. After Drilling and Planing Operations, the End Mill With Guide Shoe Is Used to Remove Metal Between Holes Hunenaronennnaannsaaoncianensoneene nena sens rolls 80 in. long, and ranging from 13% in. to 16% in. in diameter. The rolls, an end view of which may be seen in Fig. 1, are of 0.40 per cent carbon steel. Drilling is of 2% in. from the solid at the rate of % in. per min. and the two holes must register parallel within 3/32 in, at a depth of 45 in., as the finished rolls are required to be in balance. The work is held in the carriage of a large lathe in a V-block cradle, and fed against the boring bar. The latter-is held in the lathe spindle with a draw bar, and has a stuffing box at each side of a groove around the bar at the fast end for admission of lubri- cant. The design and construction of the bar, the end of which is shown in Fig. 2, are of interest. Two %-in. holes lead from the groove through the bar to the cutter end and serve to deliver lubricant under pressure, in- troducing it immediately: behind the cutter. These oil channels are produced from slots milled lengthwise of the bar after it has been rough turned. Steel cover plates are then set into the bar over the slots and oxy- acetylene welded in place, after which the bar is finish turned to 1/64 in. under size, allowing for lubricating clearance. Next, two chip clearance slots are milled in the bar. The cutter set in the end of the bar is full diameter 419 To vba dey nap Bie. 5 ey ee eR NNO te te rk nwt thes) ne on orem ibaa gape re on gic Mes eh atest ; ey SONI OIE 6 A mo > AAP IG Se My, tt i lam te i oro oe ny Sats; } bi i iy | { | He 420 THE IRON and is ground with a special undercut at the center to produce a thin point. It is pinned in place. The back of the cutter is supported by the bar to within 5/32 in. of the edge. The bar is cut back % in. from the top or cutting edge of the cutter to allow room for chips to feed into the chip clearance slot. The cutter edge is nicked to break chips. A special bracket for setting the bar is mounted pn the lathe carriage. This bracket was bored in the lathe while set close to the headstock. The bracket with! a bushing holds the end of the bar parallel with the lathe bed while the hole is being started, after which the guide bushing is removed. Oil pressure for removing chips and lubricating the bar is secured from a pump designed and built by the company. This pump is 4 in. outside diameter and has a chamber 3 in. in diameter by:2 in. In the chamber revolves a collar attached to the 1 in. pump shaft. Transversely through this collar is a slot in which the pump vanes or blades work. The shaft is set in the pump body in an eccentric position leaving % in. space as the greatest distance between the chamber interior and the periphery of the collar. The blades are L- Fig. 5. \ Relieved Area To Permit Removal of Dogs From T-Slots Is Produced By Ar Air Operated Milling Attachment AGE February 7, 1924 Fig. 4 An Ongine Lath« Has Been Equipped With Two Milling Attachments O1 Carriages to Mi| T-Slots in Opposite End of Rolli shaped and when assembled with springs between ar¢ placed in the slot in the collar. The springs serve to hold the blades tight against the chamber diameter thereby providing against leakage under driving pres- sure. Oil flows from a storage tank through a %-in. intake pipe to the pump and fills the chamber behind one blade before the other blade passes the intake orifice, which is placed close to the position of minimym clearance between body and collar. As the second blade passes the intake opening it starts to force the oil in front of it into a smaller space. The outlet is placed at the point of smallest area on that side of the pump body and leads to two %-in. pipes for delivery to the groove in the boring bar. The action serves to deliver oil under heavy pressure at the rate of 10 to 15 gal. per min. After:the two holes are drilled in the roll a slot is planed centrally between and parallel with the holes, as shown in the upper roll, Fig. 1. In addition to ful- filling a specific function when the roll is in operation on the machine on which it is employed, this planed slot is used to guide a pilot block for the next machining operation, the block sliding along under a clamping ruary 7, 1924 The piloting is to steady the end of a boring bar ar to that previously described, but which carries id mill, as shown in Fig. 3. With this end mill the left between the two drilled holes is removed. the end of the operation, the pilot is taken out , guide bushing inserted to finish. Oiling in this ition is through the slot in the roll. lhe roll is next transferred to a planer which ma- ; six slots 30 in. long equally spaced around the it the end opposite the slots just described. Fol- ng this the six slots are undercut for T-slots two : time, as shown in Fig. 4 in a double carriage lathe. roll does not turn in the lathe but is placed in a Fig. 6.—A Combined Milling Operation to Mill Keyways ind Square the Ends Is Accomplished in a Standard Horizontal Milling Machine Equipped With Vertical At- tachment fixture between the two carriages, one of which is nounted on the front of the lathe and one on the back. [he carriages are provided with heads having back geared milling spindles individually motor driven, and these milling heads are traversed along the roll to pro- vide the milling feed to produce the T-slots. The mill- ng cutters are guided by blocks sliding in the planed slots. The milling heads were designed and built at this factory. The next operation on the roll consists of milling clearance midway of the T-slot to widen it sufficiently ) permit the dog to be removed from the slot without ‘aking it all the way to the open end. The device with which this operation is accomplished is a special ver- tical milling head built by the company, shown in Fig. The head has longitudinal adjustment and cross and ertical feeds. It is driven through a universal shaft rom an air motor. The whole device is mounted on a : which clamps to the roll by means of a bolt in T-slot. \nother vertical milling attachment designed and ed by Walter Scott & Co. is that shown in Fig. 6, which employed for squaring out the ends of keyways in ifting and is made to fit an ordinary horizontal mill- machine. Multiple V-blocks are mounted on the mill- machine table to hold several shafts at once, and rresponding number of milling cutters is ganged on arbor and serve to mill the keyways. The vertical ‘tachment is driven by a chain from the milling ma- e spindle. It is adjustable horizontally on the over- and may be pinned in place by a spring plunger ioles in the overarm, an arrangement intended to the vertical cutter in position corresponding to the THE IRON AGE i keyways. The cutter is adjustable vertically for depth of cut. This attachment permits the key slots to be milled and squared at the closed end in one setting of the work. At this plant the handling of large castings which require drilling is simplified and the removal of chips facilitated by the arrangement illustrated in Fig. 7. A special iron platform has been built on which is mounted a radial drill, as shown. Large work instead of having to be lowered into a pit is bolted to the side of the platform within reach of the radial drill; the chips fall to the floor, being thereby much more easily removed than were they in a pit. Fig. 7.—Mounting a Radial Drill on a Special Stand Avoids Dropping Latge Work into a Pit for Drilling and Also Facilitates Chip Removal Bethlehem Steel Corporation’s Savings Plan for Employees President Eugene G. Grace of the Bethlehem Steel Corporation announced the inauguration of an em- ployee’s saving and stock ownership plan at the annual meeting of employees’ representatives at the Lacka- wanna plant last week. He stated that the corporation will assist its employees to purchase 7 per cent cumu- lative stock on easy terms. This comes as the result of repeated requests to the management for a plan that will help workers to save systematically and, at the same time, to become part owners in the business. By the recent extension of properties and readjustment of the financial structure, Mr. Grace said, the offering was made possible. Employees will be permitted to subscribe for one share of stock for each $400 of annual earnings under the plan. The offering price for the first year has been fixed at $94 per share, with credits for dividends and interest charges reducing the net cost. Special bonus payments on the stock, ranging from $1 to $5 per share over five years, will be made as an added incen- tive to employees. Pressed metal engineering is to be discussed at a meeting of the machine shop section of the Providence Engineering Society at the rooms of that society on the evening of Feb. 12, by Douglas P. Cook, president Boston Pressed Metal Co., Worcester, Mass. ' I dca PENARTH rip eM ae en 4 x rt is re 2 . a hep tine we alae aetna ee ee NP ated AN apt Tega PT, 2 ath 5 mw ot ans A am CI ee a ae mn . ane A mac dete gueennetin 1 case ata tle incall cams tipi cata line Seapine . . * ow iol he Removing Dust from Blast Furnace Gases Electrolytic Process Installed by Colorado Fuel & Iron Co. —Corona Discharge Produces Ionized Field Which Precipitates the Dust BY N. H IVE years ago there was not an electrical blast K furnace gas cleaner in the world. Today three installations are running successfully in the United States, two having been in more or less con- tinuous operation for the last four years and one started lately at the plant of the Colorado Fuel & Iron Co. In Addition, several of these cleaners are operat- ing in Europe. Blast furnace gas presented, to those interested in cleaning gas by electricity, a problem a great deal dif- ferent from that of those pioneers who, in the early days of precipitation, undertook to clean gases from smelters and cement plants. Their problem was one of dust, while that of blast furnace gas is one of gas. To them the dust content of the gas was important because in the dust lay their greatest values. We clean to get rid of the dust, for in the gas lie our values. They could condition their gas so as to create the best pos- sible operating conditions by changing the gas and its content, while we must leave the gas severely alone so . GELLERT* cent with a wet-cleaned gas. This was before the time of dry cleaners. To recognize what actual saving may be accomplished by the use of a dry cleaned gas as com. pared with a wet cleaned gas, it is necessary to examine the composition of blast furnace gases and determine what it is possible to do with these gases by wet clean- ing and dry cleaning. If blast furnace gas of the average composition shown in Table I is used for our purposes of discussion, it will be found that there is available as latent heat 5,447,200 B.t.u. in the 59,000 cu. ft. of gas which comes off from an average 500-ton blast furnace in one minute. It will be noticed that the greater part of this gas is inert and has no latent heat of combustion. Al] gases, however, have a thermal capacity for carrying heat, due to the input of energy caused by the ¢ombus- tion of the gas itself and the consequent temperature to which these inert gases are raised. If we compute the sensible heat existing in these gases between the limits of 0 deg. and 400 deg. Fahr., Table I.—Latent Heat of Combustion of Blast Furnace Gas Weight per Per Cent Cu. Ft. at 62 by Cu. Ft. Deg. Fahr. Constituent Volume per Min. ( Lb.) Carbon dioxide... 12.5 7,375 0.1163 Carbon monoxide 25.4 14,986 0.0736 Hydrogen ....... 3.5 2,065 0.0053 a 0.0 000 0.0841 NEFOGOM on ccces 58.6 34,574 0.0737 BR bss ann 59,000 as not, by conditioning, to interfere with its combusti- bility. They dealt with non-inflammable gases and we deal with gases that burn. Gas Is Worth Cleaning There is no doubt that every blast furnace man, who has gone through all the anguish of recheckering stoves because flue dust with a high alkaline content has burnt out his brick work, is convinced that blast furnace gas is worth cleaning. The value of clean blast furnace gas was discussed by me in a paper read before the Birmingham section of the American Society of Mechanical Engineers in October, 1921. I wish briefly to bring before you a few of the facts there presented to establish the values of clean blast furnace gas as against dirty gas. Mr. Diehl, several years ago, showed that the avail- able heat in raw gas was 77.03 per cent; the available heat in partially cleaned gas was 74.33 per cent, while the available heat in wet cleaned gas was 79.51 per cent. In his 1913 figures, he showed that the savings in increased stove efficiency was nearly 10c. per ton of iron, while the saving in limestone and the value due to increased production gave an additional 6c. per ton of iron made. Here is a total of 16c. per ton of iron in the saving caused by using a wet cleaned gas as against a dry, raw gas. Figures taken from his paper show that the boiler efficiency was 62.3 per cent with dirty gas, and 66.1 per *President Gellert Engineering Co., Philadelphia. abstract of a paper read before the F gineers, Pueblo, Colo., Dec, 17. This is Pueblo Society of En- COVUUEND EDAEDNNRSONEEE EUR EEUDENEDOCONRDDONEEDL /1/HNOMDEEREL OUD SEED ERAADELONNURSULEDERS REREEDEOSogNNNRRDO oe EHEHIONOOERE — —Latent Heat in B.t.u.———, Per Cent pér Cu. Ft. Total y at 62 Total Wt., Lb. Weight Deg. Fahr. Per Lb. per Min. 838.3 18.6 Ter tau | Seba eeses 1,103.2 24.6 318.2 4,325 4,771,100 10.9 0.2 328.0 62,032 676,100 000 000 eeee ‘se 2 28=© a OOO 2,548.3 C6 §= 8 (wees. SRS © Sarwar. 4,500.7 5,447,200 which we may accept as the outlet temperature of the burnt gases, we find that there is an additional quantity of 499,040 B.t.u. in the form of sensible heat. We are thus able to compute the total sensible heat at limits 0 deg. to 62 deg. Fahr. These figures, subtracted from the sensible heat at the limits 0 deg. to 400 deg. Fahr. give sensible heat of gas at 400 deg. Fahr. as 499,040 — 74,390 = 424,650 B.t.u. per min. The total thermal value of the gas which comes from the furnace is 5,772,500 B.t.u. per minute. This is true of dry cleaned gas having a moisture content of 35 grains per cu. ft. at standard conditions of temper ture and pressure. With wet cleaned gas, which it will be assumed is reduced to a temperature of 70 deg. ™ the cleaning, with a moisture content of 7.89 grains Pe! cu. ft., the net latent heat value is of course exactly the same. Adding to this the net sensible heat of the £4, it will be found that there is available 5,425,520 B.tu. per minute. f Now when using a dry cleaned gas, the products combustion as calculated, have a total weight of —* lb. with a volume of 59,000 cu. ft. at 62 deg. Fahr. T , determination of the sensible heat of these products ° combustion at 600 deg. (Table II) shows that the . has a total sensible heat of 1,194,980 B.t.u., from whi! must be deducted 114,380 B.t.u. which were present } the beginning. 5 Then the net sensible heat of the products of ye bustion will be 1,194,980 — 114,380 = 1,080,600 Btu per minute. The total value of the original gas for both oo and sensible heat was 5,772,500 B.t.u. The net sens! 422 of the products of combustion is 1,080,600 B.t.u.; s available heat, 4,691,900 B.t.u., and 10 per cent because of the original loss in gas, 469,190; net able heat per'minute, 4,222,710 B.t.u. rhe gas therefore escapes with a net total of 1,080,- B.t.u., leaving 4,222,710 B.t.u. The net total avail- chee iB 3] ' ' ‘ \ | | VL i 1 | | Wills aed tee a ee ePEsi ri; i ei , | J I Teeter prrhretertrrenpertecterip y= } : rt Header Ee i S Plate | ead 4 a vas | Hammer: ut 2 x, 4 + ‘ Fle - + | | : S i | ui _# ales Ey { | i i | i | PoE TE Yt T : TT 70 | Dine Srac ! p x 7 ~ OIGILILILILIGIGId Pi Tet Ti tid | Bako SN) 10094080000 () | i Weights | i) | ~ _ _ Chair eI Hopper : ' Oo fa Dump Lever: Bell Bees, ee ee 6 s Sectional Elevation and Plan of an Electrolytic Unit for Depositing Blast Furnace Dust and Cleaning the Gas Without Use of Water ible in wet cleaned gas on the other hand is 3,964,995 B.t.u., or a difference of 257,715 B.t.u. per minute. This lifference has been calculated to amount to 15.6c. per ton of iron in the saving of coke alone. Wet cleaners will cost for water alone approxi- mately 3c. per 100,000 cu. ft. of gas. If the labor for both the wet and dry cleaners is assumed to be the Same, and the charge against the dry cleaner is taken -uary 7, 1924 THE IRON AGE 423 at 0.6c. per 100,000 cu. ft. of gas, then, based on the use of 0.3 kw. per 100,000 cu. ft. of gas, there will be a saving of 2.4c. per 100,000 cu. ft. of gas, or 4.lce. per ton of pig iron made, when using electricity instead of water as a cleaning medium. The savings can be tabu- lated in somewhat this fashion: 15.9c. per ton of pig iron made, due to the use of wet cleaned gas in a hot stove as against raw gas. 15.6c. per ton, due to using hot cleaned gas as against wet cleaned gas for thermal value alone. 4.1c. saving in the operating of a dry cleaner as against the wet cleaner, making a total saving of 35.6c. in the use of hot cleaned gas over dirty gas. It has been estimated that about 5c. a ton of iron is saved in using dry cleaned gas as against wet cleaned gas in boilers. It is also estimated that at least 6c. is saved in the preservation of boiler brick, hot stove brick and linings, due to the use of a cleaned gas as against a dirty gas, which gives an additional llc. saving per ton of pig iron or a total saving of 46.6c. per ton of pig iron. In a year, on a 500-ton furnace, this saving will amount to over $85,000. Many benefits to be derived in cleaning gas electri- cally can be mentioned briefly. Ease of operation, elim- ination of stream pollution, simplicity of plant construc- tion, non-requirement of water, cleanliness of the plant and other matters all are factors which should be con- sidered in a cleaning plant. Principles of Electric Cleaning We are all familiar with the old high school experi- ment where a pith ball was charged and repelled from the charged body. This simple fundamental experiment is really the basic principle of the electrostatic precipi- tation of dust from blast furnace gases. Current at 220 volts is impressed on a transformer especially built for the rugged service required in this kind of work. Here it is stepped up from 220 volts to approximately 35,000 or 40,000 volts. The alternating current at this high voltage is then converted to uni- directional or so-called direct current at the high vol- tage by means of a rectifier. Unidirectional current at a high voltage is secured for precipitation. The precipitator itself is filled with 6-in. steel pipes, each of which has suspended through its center a negative electrode of chain or wire held taut by a 15-lb. cast iron weight. This electrode is properly insulated and is directly connected to the out- put side of the mechanical rectifier. If a mechanical rectifier is not used, kenotrons may be used. These kenotrons are more familiar now to lay- men than they were before the days of radio broad- casting. In principle they act somewhat the same as electrical check valves, allowing electrical impulses to flow in one direction only, by virtue of hot and cold electrodes. Action of Corona Discharge By the impression of voltage in the center of the pipe, a corona discharge takes place between the chain as a negative electrode and the pipe as the positive elec- trode. This corona discharge—easily seen when look- ing through the bottom or top of an open precipitator— gives off a faint bluish light which, under certain con- ditions, looks like a snowstorm in the dark. Any gas which passes through this highly ionized field is bound’ to become ionized of itself, and any particles of dust found in the gas receive an electrical charge from the ionized gas similar to the charge carried by the nega- tive electrode. These charged dust particles are repelled to the sides of the pipe and held there until the electrical cur- rent is shut off. Every particle of dust, therefore, is affected by an oblique force which is the resultant of the force due to the velocity of the gas passing up through the pipe and the horizontal force of the elec- trical impulses, forming a gradient which makes pre- cipitation possible. In the design of a precipitator, therefore, it is necessary to see that the resultant forces acting on each particle of dust are sufficiently near the horizontal so that precipitation may be effected within the pipe during the time that the particle of dust is traveling from bottom to top. The dust, having been deposited on the sides of the + mea ee or he ’ ee eta oar near te a ‘ . . ‘ a te Fy taint 4: “ ERS Ao ite . wens amet se = aa re ame co. = 424 THE pipe, will build up until that point is reached when in- sulation will take place to such an extent that the corona discharge between the negative and positive electrodes is considerably weakened. At this point the precipitator should have the current cut off and the pipes should be rapped by mechanical hammers in- stalled for that purpose. On rapping, the dust drops from the pipes into a hopper at the bottom of the pre- cipitator, and may be discharged at intervals of 12 or 24 hr., depending on the size of the hopper. This in brief is the theory of precipitation. The construction and operation of a precipitator, or more truly an electrical gas cleaner, are as simple as the theory itself. Development of Apparatus When Dr. F. G. Cottrell decided to make use of the fundamental principles of corona discharge, in aiding industry get rid of dirt and dust nuisances, he had before him the problem of finding electrical equipment which could give him continuously, and without too much expenditure, the electrical effects needed for the purposes of precipitation. It was no easy task to de- velop this electrical equipment. Great credit is due the large electrical companies, particularly the General Electric and Westinghouse companies, for the initia- tive, energy and intelligence which they have given to the general problem of precipitation. Without their work in the development of electrical apparatus it would have been impossible for precipitation to have taken the lead in the field of cleaning gases which it now holds. But electrical equipment was not alone required. In J De lea P - I r ( ‘ l l i | by t Weigel \ ! Weight Deg. Fah Li Carbon dioxide é l : 22,361 S Aqueous vapor 8,289 9 Nitroger _ (4.9 66,818 $,.922 a 100.0 17.46% 7.897.] sulators had to be devised to withstand high voltages under conditions of mechanical, electrical and physical stress present in no other kind of service. Having worked out all the problems in connection with the electrical equipment and insulators, there was left only the problem of structural detail to build precipitators which would withstand the rough usage a blast furnace usually gives its auxiliary equipment. First Installations The history of blast furnace precipitation has been interesting. Five years ago it was undertaken at the plant of the American Manganese Mfg. Co., Dunbar, Pa., on a problem far greater than had ever before been approached. This furnace was then making ferro- manganese. The furnaces had top heats as high as 1200 deg. Fahr. The gases were what is known as limey and contained a very high percentage of alkaline and manganese fume. The problem of cleaning these gases was so great that large expenditures of money for all sorts of wet cleaners had been made to no pur- pose. The electrical method was tried because no other method had proved successful. The first electrical blast furnace cleaning plant in the world was then designed and installed at this plant. Shortly thereafter another plant was built to clean the gases from a smaller furnace at Sheridan, Pa. This plant also has been operating during these years with- out difficulties of any sort. Since the electrical cleaning plants were first in- stalled at these two points the furnaces had intermit- tently been making first ferromanganese, then spiegel- eisen and then pig iron. The electrical cleaners have *See page 329. Tur Iron AGE, Aug. 11 192] IRON ~ AGE February 7, | 924 worked as effectively on one gas as on anothe; he results obtained in cleaning have been unifory ch tests as have been made at various times }\ tal measurement indicate that cleaners are remo, il] the dirt from the gas down to a point where ony 9.2 and down to less than 0.2, grain of dust per cu. ft. re. main in it. The greatest measurement, howe as been that of the increased stove heats and of le. creased losses in brick work throughout the pla In addition, there has been a physical demonstra: by means of the large amounts of flue dust collect: Colorado Equipment The latest installation which has been made hat now running at the Colorado Fuel & Iron Co., Pueblo. This small unit is the culmination of the five years of experience obtained in the operation of the plants at Dunbar and Sheridan. Not only does it contain many improvements that the other installations naturally could not have, but it has been built on the new stand- ardized plan whereby several small units take the place of a few large ones, and whereby these units may be fabricated in the shop and erected there ready to be set up without any considerable field erection. Precipita- tion has become so standardized that these unit pre- cipitators may be used at any blast furnace operating under any conditions, with similar results. The unit which has been constructed here contains 90 pipes each 6 in. in diameter and 10 ft. long. Each pipe has through its center a chain which is charged with the electrical current of the precipitator. All of these chains are hung from a top frame and steadied by a rigid bottom frame so that no swaying can take Is Combustion of Hot Gas at 600 Deg. Fahr. DASIS. ) At 600 Deg. Fahr —At 62 Deg. Fahr.— Total B.t.u. Total Specific B.t.u B.t.u. Sen- Specific per B.t.u. Sen- Heat per Lb. sible Heat Heat Lb. sible Heat 0.2260 135.60 350,020 0.1937 12.0 31.000 0.4818 289.08 113,640 0.4264 25.4 9,980 0.247¢ 148.56 731,320 0.2412 14.9 73,400 0.2522 1,194,980 0.2841 114,380 place. The gas, entering under a header at the top, envelops all the pipes, heating them up to an even tem- perature, so that, when the gas enters at the bottom of the pipes, the distribution is proper. The inspection of these pipes time after time has shown such an even distribution of dust as to prove conclusively that the distribution of gases has never been a problem in this type of an electrical cleaner. The gases with their burden pass partly up the pipes, when the electrostatic field begins its action and the dust is precipitated. The gas then passes from the top of the pipes and above the header outlet into the main. Intermittently, perhaps every 30 or 60 minutes, depending on the dirt contained in the gas, the precip!- tator is shut down and the pipes rapped. This is 4 matter of one or two minutes, when the precipitator is again put into operation. With an installation of six or eight to a blast furnace, one precipitator is off while the other five or seven are operating. As these precipitators are designed to handle a safe overload, there is practically no loss in efficiency during the cleaning periods. Precipitators are designed to handle gas flowing through them with velocities ranging from 10 to 15 ft. per sec., depending on the nature of the gas. The more we deal with precipitators the more we realize that blast furnace gases act the same at all plants and that precipitators which will work well between 10 and 10 ft. velocity will work well anywhere. When precipitators are installed in groups they may be placed in a long line or put in couples. With the most modern type two of the 90 pipe units are installed together on one electrical unit, with a capacity rated at nearly twice the consumption of current of both pre- February 7, 1924 cipitators. The reason for this is that, during an arcing period, a momentary overload may be twice the actual capacity and the equipment for precipitation must stand the terrific blows which occur at rare intervals. Action During Slips During slips the dust content is naturally greater and the velocity of the gas is somewhat greater. This point, however, must be borne in mind, that the dust content of the gas increases in a great degree during the slip while the velocity of the gas increases to a small degree. The precipitator is designed to operate at certain velocities and, unless these velocities become excessive, it will function properly, irrespective of the dust content of the gas. For this reason the precipita- tor will remove a large amount of the dust during a slip, while wet cleaners will fall down under the same conditions. Cost of Operation The operating cost of a precipitator is small, as one Malleable Casting Production WASHINGTON, Feb. 1.—The Department of Com- merce announces statistics on the production of malle- able castings manufactured for sale by months. The returns include only those castings manufactured for sale as such and do not include those used in the plant or finished and sold as other products. . Figures are also shown comparatively for June, July, August, September, October, November and December, covering the operations of 107 identical plants for which reports were received each month. Monthly Plants Total Total Capac- Per Cent Re- Produc- Ship- Orders ity of of Total porting tion ments Booked Plants Capacity Month (Number) (Tons) (Tons) (Tons) (Tons) Operated May ...« “S8 64,726 62,806 52,898 91,174 71.0 June .... 109 65,168 64,648 12.067 96,240 67.7 July ‘a 57,881 60,102 41,723 98,241 58.9 August .. 116 68,069 65,405 39,830 103,068 66.0 September 116 60,930 59.396 38,636 101,750 59.9 October .. 116 62,238 59,129 48,621 103,837 59.9 November 125 53,727 $9,426 37,231 107,350 49.1 December 126 49,72 16,664 $5,012 106,825 46.5 Comparative Summary for 107 Identical Plants Monthly Plants Total Total Capac- Per Cent Re- Produc- Ship- Orders ity of of Total porting tion ments Booked Plants Capacity Month (Number) (Tons) (Tons) (Tons) (Tons) Operated June “. ae 63,298 62,888 39,814 94,840 66.7 July .... 107 54,483 55,922 39,131 94,826 57.4 August .. 107 63,038 60,207 36,753 94,858 66.5 September 107 56,024 54,378 35,452 93,565 59.9 October .. 107 56,798 54,221 43,978 95,652 59.4 November 107 47,112 44,215 34,817 95,801 49.2 December 107 44,580 41,328 40,800 94,751 47.1 Kalman Steel Co., Chicago, Buys Corrugated Bar Co., Buffalo Purchase of the Corrugated Bar Co., Buffalo, by the Kalman Steel Co., Chicago, has just been announced by Paul J. Kalman, president of the latter organization. Acquisition of the Buffalo company is expected to put the Kalman Steel Co. in first place among distributors of reinforcing steel bars in the United States. Both the Kalman Steel Co. and the Corrugated company are fabricators of building materials and reinforcing bars. The merged organizations will be operated under the name of the Kalman Steel Co., with capital stock of approximately $2,000,000. The Kalman company will take possession of the Corrugated Bar Co. plants at once, but the actual operation of the Corrugated com- pany by the Kalman organization will not begin for about 30 days. Plants of the Corrugated Bar Co. are located at Hammond, Ind., Buffalo, Boston, Philadelphia and At- lanta, while the Kalman company already has plants at Chicago, New York, Youngstown, St. Paul and Minne- apolis. The Corrugated Bar Co. was organized in 1892 and the Kalman company in 1901. Now located at 22 West Monroe Street, Chicago, the Kalman Steel Co. will re- THE IRON AGE 425 man can handle the plant which will c’ean the gas coming from one, two or three furnaces. The dust which accumulates in the hopper will have to be han- dled by other men but, since the hoppers need be cleaned but once in 12 or 24 hr., this is a small matter. As the hoppers are self-dumping, one man can dis- charge all the dust accumulated under these conditions. A 500-ton furnace will furnish anywhere from 20 to 30 tons of flue dust in 24 hours. The damage which such a large tonnage of dirt shoved into the boilers and hot stoves can do is easily pictured. Electrical cleaners consume but small amounts of current. It is figured, from experiments obtained at the operating plants, that about 0.3 kw. is consumed in the cleaning of every 100,000 cu. ft. of gas. Since there are no big operating parts, the only moving part being a small 2-hp. motor operating the rectifier, main- tenance and repairs are small. I do not believe that the bill for maintenance of the plant at Dunbar in four years has amounted to $500. move its main offices, March 22, to the Wrigley Build- ing, where it will occupy the entire fourteenth floor. Paul J. Kalman, who will become president of the new organization, is also chairman of the board of di- rectors, Globe Steel Tubes Co., Milwaukee, Wis., presi- dent Bliss & Laughlin, Inc., Chicago, and president Hudson Motor Co. of Illinois, Chicago. The Globe Steel Tubes Co. manufactures steel tubing and the Bliss & Laughlin company cold drawn steel. George E. Routh, Jr., who with Mr. Kalman founded the Kalman Steel Co., will be vice-president. Other officers of the reorganized company will be as follows: J. A. Cathcart, assistant vice-president; A. E. Pinard, treasurer; A. P. Clark, general manager of sales. Mr. Clark held the same position with the Corrugated Bar Co. prior to its purchase. W. S. Thomson, chief en- gineer Corrugated Bar Co., will have the same position with the Kalman Steel Co. L. O. Helgesen will be Eastern sales manager with headquarters in New York. The Kalman Steel Co. started business in a small way in St. Paul in 1901 and established its main offices in Chicago in 1920. Economics for Employees Under the above title the American Management Association, 20 Vesey Street, New York, has published a 20-page pamphlet covering the report of its com- mittee on economics. Fifteen concerns or institutions are listed as having a known system of imparting economic knowledge to their men. These include the Brooklyn Edison Co., Bridgeport Brass Co., Cambria Steel Co., American Steel & Wire Co. and American Rolling Mill Co., besides a number of insurance com- panies, banks, etc. The committee worked out a list of topics frequently recurring in discussions with em- ployees, as a suggested basis for talks on the subject, and briefly discusses some of the methods used by com- panies which have taken up this work. One recommendation is to keep the groups or classes small—10 or 12 individuals. In some cases, however, where the work has been carried on by means of definite papers with lantern slides, moving picture projections and other visual means of carrying the message, the groups have been large and have participated, after the paper, in lively discussion of the points brought out. The Krupp Co. of Germany will take over Spain’s oldest engineering works, La Maquinista Terrestre y Maritima, and also the Cardona dockyard, according to a dispatch from Barcelona. It is understood that the Germans will supply technicians, and Spanish banks the capital for extensions and that large orders will be placed for work proscribed in Germany by the Treaty of Versailles. Steamers will be built at the plant for German and South American lines and locomotives for Spanish railroads. 7 LO NO GEREN O aot 4 “ = % i : : ; ‘ prercretarrs * ee mae ee dso ee a ee) Conical [lumination in Metallography ”% New Method of Illuminating Opaque Objects Obliquely —Practical Application and Advantages BY BILITY to distinguish and interpret metal struc- A tures is fundamentally affected by the method of illumination. The methods heretofore in us¢ are of two distinctly different kinds. The distinguish- ing difference is that while in one system, light is ad- mitted to the object through the objective, returning upon itself through the objective and being suitably deflected to the observer; in the other system, light is thrown on the object from some point outside the ob- jective and then is reflected through the objective to the eye. The first system is known as vertical or axial illumination and the second, as oblique illumination. These have become so familiar to metallurgists through long use, that anything radical in the way of imvrove- HARRY Diagrar Patl f Lig iz Metallograp! M duis Waeua A ( ullllun ment or modification will be greeted with at least a degree of curiosity or even doubt. Metallurgists become so familiar with metal struc- tures that they perhaps do not realize that the mental picture seldom coincides with the physical image in the micrescope. The process of examination has become second nature and tie observer is not always aware that he is not actually seeing physically all that he visualizes mentally. To take a simple illustration, a polishing scratch on a polished metallographic speci- men appears under vertical illumination to be a black line on a bright surface. We interpret this to mean that a hard abrasive particle has plowed a furrow through a yielding metal even though the furrow is not seen. Again, a polygonal configuration of thin black lines on a bright surface is the outlined cross-section of grains of metal although few know the nature of these outlines, whether a grain boundary is a step down from one level to another, or a ditch etched out between grains, or a ridge. The reason why constituents are seen only in outline under vertical illumination is, of course, that they are illuminated by light parallel, or very nearly parallel, to the axis of the lens system, and as this light falls normally upon the surface of the object no shadows are cast and very little shading is manifest. This is an unnatural condition but has become so familiar as to seem natural. It would be desirable, then, to view microscopic objects in a more natural way; to see them in relief, as one sees a man’s facial characteristics. *Abstract of a paper presented at the annual convention of the society in Pittsburgh, October. 1922 The author is as- sociated with the Union Carbide & Research Laboratories, Inc., Long Island City, N. Y S. GEORGE lurthermore, as the trend of practice seems to require examination at higher magnifications, any method im- parting a natural appearance should be adapted to high power lenses. Conical Illumination Described The method described in this paper is applicable to all objectives for it is based on the fact that the objec- tive itself is transmitting oblique as well as axial light to and from the object. Reference to Fig. 1 will make this clear. The arrangement shown is purely diagram- matic, the usual glass reflecting disk, stellite mirror and eyepiece being omitted for simplicity. Also, of course, in actual practice, the light source is not a point Fig. 1—Diagram of Path of Light in Metallographic Mi- Using Illumina- tion croscope, Vertical Tris ey Oo a QU Q a yw ae + nor is it situated at the focal distance from the con- denser. The design of the figure is merely to show clearly the fact that so-called axial illumination is really composed of true axial light and, also, of oblique light. Light traveling approximately parallel to axis AA of the lens system (axial light) falls normally upon the object and masks any relief effect produced by the oblique light. To obtain relief, it is necessary to stop out axial light only. One way of doing this is to place an opaque disk in the illuminating beam perpendicular to the axis AA. (See Fig. 2.) An image of the disk 1s formed near the back lens of the objective, thus pro- ducing a hollow cone of light in the objective, having its apex on the object. Since making this simple discovery, it has been pointed out to the writer that the method is essentially similar to oblique illumination by means of a substage condenser and stop in ordinary microscopic work with transmitted light. With reflected light and vertical illumination, the objective takes the place of the sub- stage condenser and instead of placing a stop at the back lens of the objective, this method virtually places one there by the expedient of locating the image of one at that point. The disk is preferably placed slightly eccentric so that light will fall upon the object from one direction. The particular direction of illumination, as well as te size of the disk, is best determined by trial for each individual subject and purpose. While in some cases a definite, fixed size and post tion of stop is adequate, yet in most instances it 1s de- sirable to be able to rapidly change the size of stop and to rotate the direction of light. For this purpose, the 426 February 7, 1924 iter has had constructed the two devices illustrated Figs. 3 and 4. The contrivance shown in Fig. 3 is simply an assort- nent of stops of different sizes mounted on the spokes fa wheel. As the wheel is rotated, any stop can be wung into position. The arm on which the wheel is mounted is pivoted at its base so that the entire appli- ince can be swung out of the way. Any stop may be otated about the optic axis by a compound rotary and ‘votal motion of the wheel. Fig. 3—Device (in circle) for Obtain- ing Conical Illumi- nation. The disks are mounted with- in a wheel so that they may be readi- ly adjusted in the path of light on the filter affords a convenient means of noting its position. Direction of Light he ‘Scratch .s a Elevated Constituent Fig. 6—Sketch Showing the Profile of Scratch (at AA, Fig. 5) Illustrating Method of Deter- mining Direction of Light Used in Photographing Fig. 5—Photomicrograph of Etched, Complex Alloy Under Conical Illumination. This photomicrograph shows the same field as Fig. 5-R, but in photographing, the direction for illumination for Fig. 5 was from left to right, while for Fig. 5-R it was from right to left. (x 4000, 1.9 mm. objective, 10.0 x eyepiece.) Reduced about one-half from the original THE IRON AGE The shadow of the stop . 427 Fig. 4—Device for Obtaining Conical Illumination Using an Auxiliary Iris Diaphragm Mounted Within a Wheel Whose Center Is at the Optic Axis The device illustrated in Fig. 4 serves the same pur- pose in a different way. It consists of an auxiliary iris diaphragm mounted within a wheel whose center is at the optic axis. The knurled adjusting nut controls the degree of eccentricity of the auxiliary iris. With the microscope nicely adjusted, the latter method is more conveniently operated than the one first described. Moreover, it is the more rugged in construction but has the disadvantages of requiring more accurate adjust- ment of the microscope and of cutting down the amount of light. Terminology and Microscopic Appearances In the following, the term conical oblique illumina- tion or simply conical illumination will be used to des- Fig. 5-R—Photomicrograph of Same Field as Fig. 5. If Fig. 5 and Fig. 5-R are illuminated by a strong light from the left, Fig. 5-R usually presents an illu- sion, making the broad light areas appear depressed, whereas in reality they are elevated as usually appar- ent in Fig. 5. (x 4000, 1.9 mm. objective, 10.0 x eye- piece.) Reduced about one-half ' oe itn ty nag — tn | | 2 net coma 428 ignate the method just described to distinguish it from oblique illumination as ordinarily applied. The terms vertical, normal and axial illumination refer to so-called vertical, that is, mixed axial and oblique illumination, commonly obtained when the object is illuminated through the objective. Oblique light as ordinarily applied is so nearly parallel to the surface of the object that it is not re- flected from a perfectly plane surface through the ob- jective to the eye because the angle of reflection equals the angle of incidence. Consequently, plane surfaces appear dark by ordinary oblique illumination and bright by ordinary vertical illumination. Rough surfaces, de- pressions or elevations, for the same reason, appear Etched Fig. 7—Photomicrograph of Under Conical Illumination. (x 2000, 1.9 mm. objec- Complex Alloy tive, 6.4 x eyepiece.) Reduced about one-third either light or dark, depending on whether they are viewed by ordinary oblique or by ordinary vertical illu- mination. In other words, the view obtained by ordi- nary oblique light is the negative to the positive appear- ance obtained from ordinary vertical illumination. Conical oblique light, on the other hand, does not give this negative appearance. The rays of light in this case are more nearly parallel to the optic axis and, therefore, are reflected back through the objective from plane surfaces, making them appear bright, as with so- called vertical illumination, and imparting a natural relief effect to the appearance. Conical Illumination and High Power Resolution, which is the optical quality of differen- tiating or distinguishing as such two lines which lie side by side, is directly proportional to the numerical aper- ture of the objective. In general, the greater the aper- ture, the more resolution attainable. Also, the greater the aperture, the more oblique are the outer rays in the light cone, between the objective and object. It is also evident that immersion oil will increase the obliquity of the extreme rays because its index of re- fraction is greater than that of air. As the method of conical illumination depends for its effects on the obliquity of the light passing through the objective, it follows from the above optical considerations that it is particularly adapted to high power work. Illustrations and Apparatus The accompanying photomicrographs will illustrate the method in its application to low and high power objectives. They were taken with a Bausch & Lomb inverted metallurgical microscope and camera mounted on a horizontal bed. A Wratten B filter was used in conjunction with a direct current are for illumination. Achromatic objectives and Huygenian eyepieces were THE IRON AGE February 7. | 24 used in all cases. ard orthonon. With few exceptions the photomicrographs here, which were taken by oblique conical illum are orientated the same with respect to the direc f light used in photographing which is, with resp these pages, downward from left to right, at an of 45 deg. The left side of elevations and the righ: s; of depressions will then appear bright. The se of sight is very easily deceived, however, and unles direction of light used in photographing is known. impossible to tell, in the case of unknown structypes whether the appearance is real or an illusion. |} il] aid in avoiding the illusion if the light used in exam; The photographic plates wer, Fig. 8—Photomicrograph of the Same Field as Fig. 7 Under Vertical Illumination. (x 2000, 1.9 mm. objec- tive, 6.4 x eyepiece.) Reduced about one-third Fig. 9—Field Lighted from the Left Shows Angulat Material Deeply Recessed by Etching, Contrasting with the Scratch Running Diagonally Across the Field. The light colored areas, whose west slopes are lighted and Reduced about one-half from an original of 2000 dia., etched whose east slopes are shaded, are plateaus. ing the micrographs be a strong one and have the same direction as that used in photographing. One of the exceptions in orientation mentioned above is Fig. 5R which, when compared with Fig. 5 under 4 strong light from the upper left illustrates the illusion referred to. Under this condition of lighting most ob- servers see Fig. 5R as the inverse of Fig. 5. The reason bruary 7, 1924 this is that while the fields are orientated the same. direction of light was reversed in Fig. 5R. What elevations in one seem to be depressions in the her. Turning the pictures upside down or allowing e light to come from lower right usually inverts the pearance of both pictures. When one is familiar vith a particular structure the illusion rarely occurs respective of the direction of light used in photo- raphing relative to that illuminating the picture. The llusion may also manifest itself while an object is be- g examined through the microscope, but only rarely with known structures or when a known detail such ; a polishing scratch is visible in the field. The point to be emphasized in connection with con- cal illumination is that in interpretation of structure, t is dangerous when examining an unknown structure to rely on appearances. For correct interpretation, the direction of illumination must be known. The facts of ‘elief must then be deduced. If the appearance co- Fig. rite. Fig. incides with the deduction, it is real. If it does not, it is an illusion. When this process has been applied to a view which persists in being an illusion, it will suddenly nvert and present the true appearance. Value of Polishing Scratches Because of the foregoing when examining an un- known structure, if this illusion proves confusing, it is advisable to analyze the structure with reference to a known surface detail such as a polishing scratch. If a scratch is large enough or under sufficient magnifica- tion it serves as a criterion to determine whether the illusion is present. Reference to F