The Iron Age 1914-12-10: Vol 94 Iss 24

TOUULEUEDOO EERE: —— sss a —— HUNADUEVUADELONDODONEDADSUAVOOSUSUOOEOEEDOOEDEVSUEUEVIVANEVE0UOUOUEDEOEUOURNEDELOVEAEOUODOUOQEDEDELEUELOOEADEDEDED AT OPOUEDEUEDODEDEOOUADEOEAAUCOEGEUUULOEAUULS TOUCH HOEY Established 1855 New York, H)NVGEOEDEDADOEVOVADURDOUUELOOVEDEDDOVOOVEUOOVOLODOELADIOOEOOELADUEOODOEDEDOODUTUELODESUOOODUEDADEAD OLDS NOUEUADEAERED EDEL EDADAUUEEETUEDEL EDAD EEEUETTELAD LEED ADA EAU ED EEA PEE EEE December 10, ia) sy = 1914 Machinery Hall Cranes, Panama Exposition Means for Transporting Exhibits and Han- dling Heavy Materials in Machinery Demon- strations at the San Francisco World’s Fair For handling and installing the various exhibits Machinery Hall at the Panama-Pacific Interna- 11 Exposition, four cranes of the electric travel- bridge type have been put in use. Machinery Hall, which is said to be the largest timber frame building ever constructed, is traversed from north south, its greatest dimension, by three aisles, ach 75 ft. wide. Owing to the great hight of the roof, it was possible to place the cranes at a con- siderable distance from the floor. The aisles are 937 ft. in length and the cranes operate the entire distance. In the central aisle two 30-ton cranes have been installed. These may be operated separately or in unison. When operated together, they represent a lifting and carrying capacity of 60 tons. The two cranes are equipped with four alternating- current motors and have an auxiliary hoisting One of the Four Electric Traveling Cranes in the Monumental Timber 1333 drum. <A 20-ton crane is and is equipped with three alternating-current motors. All the cranes have the control, the cab to be suspended at one end of the crane. cranes are of the box girder type, and were col structed and installed by the Cyclops Iron Works, San Francisco. The steel rails on which the cranes run ars on timber trusses of the Howe type, as in the accompanying illustration. rhe which run up to 9 ft. in depth, are designed strong enough to carry any load which the will handle. The rails are 50 ft. 8 in. from the floor an unusual hight. The posts which support the roof and are spaced 26 ft. apart, carry The timbers used in the truss girders run from 12 to 18 in. in thickness. The posts rest on pil footings designed to carry 20 tons each iseaq in @acn side aisit ( ab indicate trusses cranes the trusses. Structure for Machine Exhibits The Elimination of Seams in Steel Rails’ Increased weight of rolling stock and speed of traffic have necessitated increas- ing the size of the rail sections, and _ hence their weight; and as many of the details of rail manufacture have been changed with such alterations, it is not surprising that new and unexpected phys- ical weaknesses. de- veloped in the heavier rails. One of the most notable failure through _— crescent- shaped pieces. break- ing out of the rail Hanges, followed by at least one, and in many cases several, ruptures the whole section of the rail. Investigation showed that in practically every instance of such failure there was a more or less pronounced seam running longitudinally in the bottom of the rail near its center, and thus imme diately under its web. This seam occurs at the top was across of the curve of the crescent shaped break and t is undoubtedly the point at which the frac- ture starts. It is true that rails with actual flaws in their flanges have been rejected as first quality ones and that a very pronounced seamy condition of the bottom of the rail would also cause its rejection. Such rejections were the cause of frequent dis- putes between the mill operatives and the in- *Paper, substantially full, read before the Amer Society of Mechanical Engineers, New York, December 3 Partly-Formed Rolled Products Milled at Lackawanna Steel Works to Remove Seam-Forming Apertures and Decar- burized Ingot Surfaces BY ROBERT W. HUNT spectors, the point be- | ing as to how far the inspectors were war- ranted incarrying their condemnation; | but, as already said, it | was not felt that a single seam, unless | very pronounced, would | be dangerous. The crescent-shaped breaks were of such frequent occurrence that they indicated a very serious condition and led rail makers to experiment with the de- sign of their rolli E ' " Ge rig. 2—After Heating, Ad- passes with a view to hering Scale Removed obviating the forma- tion of the bottom seams. It was found that fewer seams were produced by such changes, but they were not entirely eliminated. While more or less successful in preventing the formation of seams through lapping on the bottom of the rails, the formation of seams in other parts of the section was not particularly affected. T. H. Mathias, assistant general superintendent of the Lackawanna Steel Company, determined that the most certain way of getting rid of seams was to remove that portion of the metal which con- tained them, and, as applied to steel rails, thus to eliminate them from both the base and head of the rail. This was a reasonable assumption, but its execution, I think, would have seemed very impractical to most metallurgical engineers. Mr. Mathias reasoned that the primary causes of seams LL vower Carbon Skin of Ingot ty t ber 10, 1914 previous to any rolling of the steel, in fact, cident to the casting of the molten metal ngots. He knew that disk-like apertures rmed on the sides of ingots while the molten was being cast and were probably caused ir being entrapped against the sides of the olds by the hot steel as it rose in the molds, dition which was not controlled in regular acturing routine. This condition illus- by Figs. 1 and 2, which are photographs of me face of an ingot, Fig. 1 showing the side would appear before heating, while Fig. 2 it after heating, with the adhering scale ed. 3 represents the actual size of a is Fig. oO of a face of such an ingot, and gives an ration of how serious such apertures may be. tched longitudinally and thus be formed into Mi be appreciated that, as the section of the is reduced and elongated in the rolling of course, will the apertures So, be Mathias demonstrated that there is another THE IRON AGE 135: ~~ to remove mechanically the parts of the enveloping steel which would form the top of the head and bottom of the flange of the rail, and experimente: accordingly. He designed and his company installed as an addition to their rail train, a milling, or a hot sawing machine, as I believe Mr. Mathias designates it, to cut off hot metal without retard ing the regular operation or thus interfering wit! the production of the mill. This illustrated b Fig. 5, which is a photograph of the machine operation. The machine located in relation to the rest of the rail train. The ingot is reduced in the blooming rolls to az 8 x 8 in. cross-section and after cropping the ends the bloom is further reduced in the roughing o1 shaping stand of rolls by five passes When it leaves these rolls, it is approximately 75 per cent finished and at this period it is carried to the right and entered between two pinch rolls with its | or flange side up. A bar which will make four 33-ft. rails is at this point in the rolling operation about 60 ft. in length; therefore, the is echelot I is i St area ol Fig Hot Sawing or Milling Machine in Operatior condition present in the rolling of large metal to be cut off or removed in the milling ngots, in the formation of a decarburized machine is approximately % in. deep, 7 in. wide e on all of their four faces, about 5/16 in. and 60 ft. long. It is driven through the pinch roll and containing from 8 to 10 points lower than the metal immediately under it, the burized envelope undoubtedly being produced rh the oxidizing conditions to which ingots jected in the soaking pits where they are preparatory to rolling. A thick oxide scale ivs formed on the surface of ingots in the that conditions are invariably present for duction of such a layer of lower carbon n their outside faces. Fig. 4 illustrates the ce of this lower carbon envelope or skin. ws a polished and etched cross-section of a ' an ingot which has been heated to a rolling rature in the soaking pits but not rolled, which it will be realized that ingots of large have both disk-like apertures on their four and a decarburized envelope in which they ntained. Mathias oT ? was convinced that during the rolling ingots into rails it was practical at a rate of 60 ft. in 30 The pinch rolls have a draft of about *¢ in. and thus force the bar between the two milling saws, which ar ranged in the housing that they may lowered desired. From 1/32 to 3/64 in. of metal milled from the head and base the bar, the front end of which, immediately on pass ing from between the rolls, is caught by a second set of pinch rolls which have a draft of about 1/1 in. These pinch rolls force the bar between the tools, pull it from between them, and also hold it in practically perfect line for the milling operatior The milling apparatus driven electrically requires about 600 hp. for its operation. Fig. 6 shows an etched cross-section of the piec: preparatory to its entering the milling machine and on it is clearly shown the enveloping layer of lower carbon seconds are =i) be raised o1 as IS of is and steel. As stated, it is treated witl the wider, or flange side up. As the milled dust or particles of steel ar 1336 thrown out, they are hit Vy watel inder pressure which forces them into a chute and also prevent the material from adhering together. By the chute they are carried below the mill and caught in boxes or receptacles suitable for charging as scrap nto the open-hearth furnaces. Fig. 7 shows the umulated ma maition or ti act terial which, will be seen, is in regular open-hearth furnace harging boxes. It is 5 face and re- per minute, 100,000 milling tools. ft. in diameter with an 8-in. width of volves at a peripheral speed of 2500 ft. thus Fig. 8 shows one of the causing an engagement ot about teeth per minute on the hot rail bar of 0.80 carbon steel, and it that they will mill at without requiring dressing. milled about 15,000 tons. The teeth are has been demonstrated 30.000 tons of least material The one shown had Fig. 9 presents the shape of the bar after it eaves the milling machine preparatory to further reduction in the regular rail rolls. It will be noticed that the milling on the flange has not reached the extreme edges of the bar, and on the affected the corners, and it Fig. 8 showed the 1 head side has not will ve recalled that straight nodification of illing tool with apparent that either by a the shape of the piece as presented in the face. It is for treatment what will pre bal ly be milling machine or, more practical, changing the face of the tool, the milling can be extended to the extreme the flange portion of the bar and what around the corners of This will undoubtedly be eage ol some- the top or head side. perfecth practical at d THE IRON December 10, 1914 AGE Milling Mach thereby eliminate the seams which may be located in those parts of the bar. Such elimination is not accomplished at present, and perhaps it may The primary object was to elir inate the seams from the central portion of thé bottom of the rail which had been the starting point of the moonshaped failures, and to rem them from the top or bearing surface of the head of the rail. Personally I think it will be desirable to extend the milling by the use of convex-faced pe necessary. + tools. The work of rolling which the steel receives after the removal of the more or less laminated metal must produce a better product than if such elimination had not taken place, and, in the cass it should not only make them less breakage on account of seams in their flanges, but also enable them better to resist the abrasive effects of traffic. During the many years of my connection with rail making I have examined a great many etched specimens of rails, not only directly in connection with the process under consideration, but for vari- ous other reasons. From such experience I can fully appreciate what Mr. Mathias has accom- plished. The surfaces of practically all rails, wher etched, show some seams on both base head, and very frequently the extent of such defects will not be appreciable if the scale has not been removed. Even then, it is not always an easy or certain matter to estimate the depth of the seams. When the rails have been subjected to the Mathias milling operation and still show pronounced seams, ot steel ralis, liable to 17 } Will and been found that breaking tests will practi- always develop the fact that the suspicious ng is an actual seam. , illustrate the appearance of many ordinary rails of commerce when etched, Figs. 10 and w the surfaces of both heads and flanges. specimens were taken from rails made by -overal different makers, including the Lackawanna Stee! Company. These illustrations not only clearly show the field for such an operation as I have de- ed, but also the extent to which Mr. Mathias een able to accomplish it. Bottom Surface Fig. 10—Untreated Rail Vhile I have confined myself to the matter of rails, it is patent that the process will be of value in the preparation of blooms for axles all other kinds of forgings. As is well known, practically the universal custom to endeavor move the seams developed in rolling axle billets hipping them out through the use of pneu- hammers, and for some of the higher char- acters of forgings, notably for automobile parts, the endeavor to eliminate the seams is carried to the extent of turning off the whole surface of the billets. I am confident that by the Mathias plan the greater part, if not all, of such work can be superseded, and I regard the invention and its practical installation as a notable achievement in the art. The Discussion The paper was discussed by Henry D. Hibbard, Plainfield, N. J., who characterized the Mathias Top Surface Bottom Surface Fig 11 Milled Rail procedure, not unfavorably in itself, as curing some- thing which ought not to exist; by James E. Howard, engineer-physicist of the Interstate Commerce Com- mission; by Max H. Wickhorst, engineer of tests of the rail committee of the American Railway Engineering Association, and by Dr. P. H. Dudley, consulting engineer for the New York Central Lines. In concluding his presentation of the paper, Cap- 1338 tain Hunt mentioned that the percentage of second- class rails had been so much reduced by the use of the milling machine that the Lackawanna Steel Company does not regard it as costing anything to do the additional work on the rails. An ab- stract of the discussion follows: BY JAMES E. HOWARD Mr. Mathias has set out to remove by a me- chanical process defects attributed to the primitive condition of the surface of the ingot, and in so doing incidentally effects the removal of some par- tially decarburized steel which would finally be found on the running surface of the head and the lower surface of the base, the two important sur- faces in the use of the rail. The unfavorable influence which attends the presence of soft surface metal, when located over a hard steel core, and exposed to wheel pressures at the running surface of the head, is manifest, par- ticularly when interior streaks or seaminess is pres- ent. Such metal by reason of its low resistance against lateral flow promotes the formation of longitudinal seams in the rail. It augments the wedging and splitting tendency of the wheel loads when their effects, in penetrating the metal of the head, shall have encountered interior streaks or lamination. Occasion was taken in a report issued by the {Interstate Commerce Commission under date of May 8, 1912, pertaining to a derailment on the Great Northern Railway, to refer to a difference of 16 points in carbon between the center of the head and the metal near the running surface in the rail which was responsible for that derailment. Still earlier, Tests of Metals, 1909, showed a dif ference of 28 points in carbon between the center and the sides of the head of a 75-lb. rail. Such occurrences are common and their fre quency constitutes a sufficient basis for the claim advanced by Mr. Mathias that one of the features of his process consists of the removal of partly de- carburized metal, in cases where it exists on the surfaces of the ingots. However, less anxiety at- taches to the presence of decarburized surface metal at the base than at the head of the rail. In fact, the evidence furnished by rails in service does not make it conclusive that soft steel at the immediate surface of the base is at that place necessaril) disadvantageous. Soft steel may display the func- tions of a deterrent against the detrimental influ- ence of seaminess in such places. The mechanical removal of surface defects is a step in the direction of furnishing safer rails, and as such is com- mendable. Prevalence of Interior Streaks in Rails It is appropriate, however, at this time, to men- tion the prevalence of interior streaks in some rails. Such streaks are the cause of many rail failures, and they should be eliminated if it is feasible to do so. The examination of the metal of a 100-lb. rail of recent manufacture, an A rail, showed the presence of 22 seams in the metal of the head, ranging in length from ‘'% to 5% in. and at various depths up to *4 in. Some were at the surface, but generally they were most preva- lent at depths of % to *%g in. below the running surface. Those of the base were found at depths up to 9/16 in. measured from the lower surface, lengths from % to 7‘ in., and in from the edge of the flange 1 to 234 in. Twenty-three of tnese base seams were disclosed in this rail. Other rails from other heats and other parts of the ingot were free from interior streaks, so far as disclosed THE IRON AGE December 10, 1914 by the examination that was made of By milling the metal from the rail bar, int - defects are necessarily brought nearer the r: surfaces of the finished rails, a circumstance y may to advantage be observed when the rails r. the track, in order to note whether or not t! are any attending disadvantages resulting fron removal of some parts of the primitive cross-sec} BY DR. P. H. DUDLEY The design of the hot-milling machine by \; Mathias is one of the indications of the growi: co-operation between the manufacturer and « sumer to remove minor surface defects in stee| rails, which defects a few years ago under lighte; wheel loads were of less significance. The consumers of steel rails in the past six to eight years, by the adoption of basic open-hearth steel for rails, have reduced the breakages and fai! ures to a marked extent. This has increased the cost to the railway companies over 7 per cent. to replace Bessemer steel rails of 0.10 per cent. phos phorus and about 0.50 per cent. carbon by a steel of 0.62 to 0.75 per cent. carbon, and under 0.04 per cent. in phosphorus for 100-lb. rails. The check ing of the basic open-hearth ingots in blooming is not nearly so frequent as in Bessemer ingots, and the half-moon, or crescent-shaped breaks, have been reduced in the same sections of rails, nearly in the proportion of one open-hearth to about 50 in the Bessemer product. Mr. Mathias expects to be able, with his hot-milling machine, to reduce even the smaller percentage for the basic open-hearth rails mentioned, and this will be of advantage to the rail- way companies. Less Injurious Rail-Straightening Method Wanted The straightening presses formerly had a verti- cal movement of about 1 in. of the head, and made 18 strokes per minute. Some of those old presses have since been altered for a vertical movement of 2 in. of the head and make the same number of strokes per minute. The injury to the rails is not only greater, but the permanent sets have be- come of such an extent that half-moon breaks have developed from those checks in the base after a short service in the track. Years ago when I could take the time to walk over the track after new rails were laid I found many half-moon breaks between the ties in the bases of rails gagged under the presses with 2-in. head movement, due to the subsequent development of the strains left in the metal to straighten the rails. It has been noticed in new Bessemer steel rails which have been piled 6 to 8 months that many half-moon checks had’ completed their development as fractures, became detached and were found when the rails were loaded for distribution upon the track. It is a misconception of the relations of the wheel contacts on the bearing surface of the rai! heads that as the wheel loads have increased, th« areas of the contacts between each have been re duced by the recent coning and shape of the whee! tread contours. The Pennsylvania Railroad Com pany has made its new 125-lb. rail for trial wit! a head 3 in. wide. The New York Central & Hud son River and the Boston & Albany Railroad com panies have used a rail head 3 in. wide for 22 and 23 years, respectively. The consumers hope there will be soon an in stallation of less injurious methods to straighte! the rails of the stiffer sections than those now 1! use, since Mr. Mathias has introduced his “hot miller” to remove seams from head and base. December 10, 1914 Heavy 30-In. Projectile Turning Lathe Niles-Bement-Pond Company, 111 Broad- New York City, has recently built several and powerful 30-in. lathes. These are by a 35-hp. motor and are intended for g armor piercing projectiles up to a max- diameter of 14 in. They are designed to be n the tough and hard steel forgings entering In. Heavy Motor-Driven Lathe Designed for Turn into the construction of this form of ammunition. Some idea of the construction of these tools can be gathered from the accompanying illustra- tion. The headstock, which is completely inclosed, has been provided with a bearing of 71 in. on the ed, which is relied upon to provide a rigid support the spindle, gearing and the driving motor. he bearings for all of the rotating shafts are with bronze bushings and together with the s are oiled from a tank in the headstock which ept filled by a pump which takes its supply from ond tank in the bed. All of the gearing is of and the motor pinion and the gear that hes with it have herringbone teeth. The spindle bearing is 18% in. long and in. in diameter, and the end thrust the spindle is taken on hardened steel and ze washers. It is pointed out that this rangement eliminates the tendency of the up- d thrust of the tool to lift the spindle in its rings. A direct-connected motor drives the late through gearing at speeds ranging from 152 r.p.m. In all there are 40 speeds avail- which are secured by a 3 to 1 speed variation he motor itself and augmented by a set of nge gears. A handle on the carriage enables faceplate to be started, stopped or reversed one of the various speeds secured without ng necessary for the operator to leave his ing position at the carriage. he carriage, which has a bearing on the bed ts entire length, both front and rear, is gibbed rneath the track, both inside and out. Nine rsible feeds are provided, which range from to 44 in. per revolution of the spindle. Three hese can be secured by a sliding key without ving any gears, and both hand and power feeds are provided. The tool carriage has a pound swiveling rest and the tool slide is pro- d with four large clamping bolts and straps. THE IRON AGE 1339 All the parts upon the carriage proper are of steel. Although the tailstock is of rigid construction, its section is increased considerably toward the end carrying the tailstock center. A crank wrench and gearing engaging the steel feed rack enables it to be traversed rapidly in spite of its weight. A tail brace which engages a rack in the bed near the front track is relied upon to prevent any pos sibility of the tailstock slipping under heavy loads ng Armor Piercing Projectiles Up to a Maximum Diameter of 14 Ir and serves to reinforce the four 145-in. clamping bolts and the steel clamps with which the tailstock is provided. New Line of Magnetic Lock-Out Switches The Cutler-Hammer Mfg. Company, Milwaukee Wis., has developed a new line of magnetic lock-out switches, including one of the series coil operated type and a redesigned form of shunt coil operated switch The line is made in 11 sizes, with capacities ranging from 50 to 3600 amperes, and is intended particularly for use in connection with the automatic starting of motors. One of the features of the switch is that it will remain open when the current passing through its wind ings exceeds a predetermined adjustable value and wher the current falls below this point, the switch closes Formerly the magnetic switches of this company were of the clapper type in the smaller sizes and of the con tactor type in the larger ones, but in developing the new line the clapper type construction has been used throughout. On switches up to 100 amperes the arcing contacts also carry the current, but in the larger sizes, auxiliary arcing contacts are provided, the current be ing carried by laminated brush contacts. Among the advantages claimed for the clapper type constructior are greater capacity for rupturing of the arc, longer life of contacts, more rapid operation, interchange ability of parts and easier access to parts requiring it spection and repairs. A 14-in. x 6-ft. engine lathe with 12 spindle speed secured by means of 13 gears, has been brought out by the Springfield Machine Tool Company, Springfield Ohio. It is arranged for direct drive from the line shaft to a single friction-clutch pulley or for a direct connected motor drive. The headstock mechanism is entirely inclosed, and the gears run in an oil bath. The clutch pulley is located on the rear of the head and the clutch is operated by a push rod that allows the lathe to be started and stopped instantly, in addition to do away with a countershaft. Factors in Hardening Tool Steel’ Important Discussion of the Ef- fect of the Time of Heating, the Speed of Quenching and the Mass BY JOHN A. MATHEWS The phenomena of carburizing iron and of hard- ening it by quenching have been known for many centuries, yet the explanation of hardening steel has not yet been given to the satisfaction of all. Many theories have been advanced and each has its ad- herents, but one can scarcely say that any gener- ally accepted theory or explanation exists. As re- cently as this year, two very interesting new theo- ries were advanced at the May meeting of the Iron and Steel Institute of Great Britain. ln what follows we are not so much interested in the theories as in the practice of the art of hardening and tempering tool steel, and we shall confine our attentions to carbon steels, together with some consideration of so-called special steels containing various alloys, usually below 3 per cent. We shall not discuss high-speed steels, nor the many low-carbon alloy steels, primarily of value on a ‘ount of their tensile qualities, but also, in many * limited value for tools, especially those used for hot work. We shall consider the subject, also, from the basis of sound well-worked materials cases ol fluence of and shall not consider the it defects, such laps, burning, etc. The hardening operation itself will give sufficient scope for our thought and attention. Tool steels are included within the range of 0.60 to 1.50 per cent. carbon, but not less than 90 per cent. of them fall within carbon limits of 0.75 to 1.35 per cent. They are usually crucible process or the very as pipes, seams, bursts made by new processes, and just now there is considerable discussion as to the relative merits of these methods. As the writ ers are among the few men in the world who have had practical experience with both processes, we will ) the very old } electric refrain from discussing their respective merits at the present time to leave a free field for partisans. It is hardly necessary to remark that no mere process a guarantee of quality takes brain plus a process, to succeed in almost any line of manufacture. which operations between the melting and the selling stage. This is particularly true of tool steel, is subjected to so many EXPANSION AND CONTRACTION WITH HEATING Of great practical importance to the hardener are the volume changes, both expansion and con- traction, which occur during the critical ranges of *F ron pa per presented at the annual meeting in Né i of the American Society of Mechanical Engineer December 1 to 4 Doctor Mathews is gener nanag of t Halcomb Steel Company, Syracuse, N. Y., i Mr. St z ssociated with hin AND HOWARD J. STAGG, JR. temperature. The permanent changes in d sions which steel undergoes in hardening are . utmost interest to the hardener, and associated these changes is the problem of hardening cr: Le Chatelier has studied the phenomena ot pansion or dilatation by accurate scientific met} and has divided the changes into three zones of t perature: (a) changes at temperatures below at which allotropic transformation begins; changes at temperatures above those at which a tropic transformation occurs; and (c) changes curring within the critical range itself. During t! first of these periods from 0 to 700 deg. C., i: and steel expand nearly equally, the amount of « bon exerting little influence. For any iron or ste however, the amount or rate of dilatation incre: with the temperature. Below 100 deg. C. the d tation is about 0.000011 in., while between 600 700 deg. C. it increases to 0.0000165 in. per deg Above the critical range, however, the coefficient dilatation varies directly with the carbon and nearly twice as great for a 1.20 carbon steel as for »< »3” “4 4 e & a 0.05 carbon iron. The changes taking place AC, and AR, Le Chatelier has not been able t study so satisfactorily. He has found, however, that the dilatation, which increases directly with the temperature up to AC., suddenly stops and that in stead of an expansion, a marked contraction takes place. On cooling steel from high temperatures, these changes in dimensions are reversed, although the are not quantitatively equal, nor do they occur at the temperatures. It is an axiom that heat expands and that cold contracts; but with steel there certain critical temperature at which an ab- normal behavior is noticed, namely, a sudden shrink age on heating and an expansion on cooling. The expansion of steel in heating to 750 deg. C s in. per same i 2" i> a . is ab foot, and when we recall that, in quench ing, a corresponding contraction attempts to take uddenly, it is little wonder that strains art set up that may exceed the ultimate strength of the steel. What is the relation of the above to overheating, or heating above that temperature at which it }s necessary to harden? After passing through thé critical range, the expansion takes place at its maximum rate. When steel is heated in such manner it assumes the shape corresponding to the maximum temperature and on cooling the whole piece tends to return to, or near, its original size. In so doing, the outer, or first cooled, portion 1s hardened first and forms a hard, brittle, unyielding 340 2 iber 10, 1914 THE Effect of Mass 4 : , ; | C.049 5 a0 | 4.510/4 Criis { Mn 074 V Ov P 0007 ; i po reer petits by doen — 4 4 he strains set the slower cooling ip b a) fracture the shell, produc- ternal cracks, especially if the shell be un- t or (b) burst the~piece at the if the shell is of even thickness and strength. atter occurrence is accompanied by a peculiar of the fracture and frequently alled pipe. may either nicKNness , ance and TIME OF HEATING ich stress cannot be laid on the fact that a correct length of time for heating and > ime of heating is as important as the ture to which heated. There are at least ers which must be avoided. f the heating be too fast, a uniform ten does not exist throughout the mass being For example, a die block heated too quick! the following conditions: The AC, and expanding be above at 2 | Pd 2 73 SIZE IN INCHES H s < Test P s Afte Qu z outer the in the transformat the What wonder that aXl IRON AGE o | } } r mum } ‘ inner expanding ditions? eecond, able time above AC. If that the piece S under long time, extent that + h«t 1341 Effec af | t ‘ 9 oe Mr 67 N + ‘ + + ———x—gi — ————— >... - ‘ — te; the intermediate portions may be ion range and contracting; while portion, which is below AC, is slowly at the characteristic rate below At‘ steel fractures under sucl grain size depends among other vari a) temperature above AC,, and (b neating be ¢ uch a cnaracter is held above AC,, for an abnormally he crystals may have grown to such an on quenching, abnormal grain e is d the result is a weak, if not cracked, ting in a turnace w! n considerabl\ the correct hardening temperature bad practice. The difficulty s that the corners and edges are liable to attain ed temperature before the larger por piece attain tne rrect hardening tem re om <s H ‘ : } ' £ ot 1342 THE IRON AGE perature, and this overheating of the thin parts pro- duces large grain size, abnormal expansion and tends to produce cracks. SPEED OF QUENCHING if a sample of steel be cooled slowly from above AC,, the solid solution which has been formed breaks up and precipitates its cementite and ferrite and we have then an annealed steel. If the cooling, on the contrary, be rapid, the solid solution is not given the time necessary to permit the complete dissociation into cementite and pearlite, and we find formed the intermediate breakdown of austenite, known as martensite. If the cooling be intermediate in its speed between extremely slow and extremely fast, we find intermediate microconstituents, troos- 1400 DEGREES, FAHRENHEIT 1380 Fig. #6---Temperature-Size Curve fi Hardening Tools tite or sorbite. The correct constituent, however, in a hardened steel is martensite, and to form this martensite the material must be cooled quickly. There are several degrees of “quickness” which at once suggest themselves. There is, however, a critical rate of coolipg through the range which must be attained before the piece will be hardened. On quenching it is clear that the surfaces of the section are cooled and hardened first. If the mass being cooled is of considerable size, different de- grees of hardness are noticed from the outside to the middle. This can be illustrated by the two examples in the fable, which, however, are not tool steels. Bars of the analysis shown, 314 in. sq. x 18 in. long, were quenched from indicated tempera- tures. A transverse section 4» in. thick was sawed from the middle and Brinell hardness tests made at equidistant points on its surface. It will be noted that in each instance the corners, or thinnest portions, were the hardest. Next in hardness were the edges, and the decrease in hardness was quite uniform to the center of the bar. The cooling medium used, its temperature and condition also affect the rate of cooling. Benedicks has investigated this subject and arrived at con clusions of extreme interest. He found that in order that a liquid present in large bulk may ex- hibit a good quenching power it is necessary: that it should possess a high latent heat of vaporization; that it be maintained at a temperature low enough to avoid too abundant formation of vapor. High specific heat, low viscosity and large heat conduc- tivity all act, it is true, in the direction of quick cooling, but the influence of the two factors last mentioned appears to be of a different and lesser grade than the heat of vapor formation. The authors have devoted considerable time to investigating numerous commercial media which December 10, 1514 are in use in typical hardening plants of the try at the present time. The results given ar: Table of Penetration of Hardness 2 3 4 5 6 7 411 359 321 314 $11 3% in Sq. by 2 359 316 297 2381 400 water, 1500 deg 3 337 283 283 280 » 340 in. * transverse i 0 283 280 280 335 from middle of 5 7 278 283 280 340 C, 0.29; Si, 0.0 f ) 301 297 281 380 0.65 P, 0.01: S j 359 337 317 120 Ni, 3.47 l 2 3 4 5 6 7 l 9 353 337 317 337 3: 3% in. sq. by 18 j 2 50 335 325 320 323 3: 1675 deg. F. 2 28 330 320 320 320 3: transverse section { 1 25 320 316 314 316 3: middle of lengt} ) 28 325 320 317 320 3 0.49 ; Si,0.14; Mn, 6 0 7 2 319 323 32 P, 0.015; S, 0.014 i } 90 328 325 328 359 362 LBS <> We Wade a small portion of those actually obtained, but the are typical. In attacking the problem, the following method was adopted: A test piece of the dimensions show in Fig. 1 was machined from a solid bar, and a hol drilled through the neck to within an equal distance from each side and bottom of the test piece. Int: this hole a calibrated, platinum-rhodium couple wa inserted and the leads connected to a calibrated ga! vanometer. The test piece was then immersed in ; lead pot, also containing a thermo-couple to th« point A, and the lead pot was maintained at a tem perature of 1200 deg. F. When the couple insid« the test piece was at 1200 deg. F., and the couple in the lead pot read 1200 deg F., the test piece was removed and quenched to the point B in 25 gal. of the quenching medium under consideration. At the start the quenching medium was maintained at room temperature. The time in seconds that it took the test piece to fall from a temperature of 1200 deg. F. to a temperature of 700 deg. F. was noted by the aid of a stop-watch. It is clear that im- mersing the test piece in the quenching mediun raised the temperature of the medium. The test piece was then replaced in the lead, heated to 1200 deg. F., quenched into the medium at this higher temperature and the time again taken with the stop watch. These operations were continued until the quenching media, in the case of oils, had attained : temperature of about 250 deg F. A consideration of the results is interesting Pure water has a fairly constant quenching rate up to a temperature of 100 deg. F., where it begins to fall off. At 125 deg. F. the slope is very marked. Brine solutions have both a quicker rate of cooling and are more effective at higher temperatures than water. The curve does not begin to fall off seri ously until a temperature in the neighborhood of 150 deg. F. is reached. Where water at 70 deg. F. cooled the test piece in 60 sec., the brine solutions cooled it in 55 see. As is well known the oils are slower in their quenching powers than water or brine solutions, but the majority of them have a much more constant rate of cooling at higher tem peratures than water or brine. HARDNESS AS AFFECTED BY MASS It has been known for some time that different masses of the same material on being ‘quenched under like conditions gave varying physical proper ties, but it is only within recent years that the quantitative effect has been measured. The au thors give below a few results which, although ob tained several years ago, are printed for the first time. Test pieces 4 in. long were made from the samé¢ ingot in sizes increasing ¥ in. in both breadth and thickness. The smallest was °4 in. square and th« largest 31, in. square. Three ingots of different type analyses were chosen and a series of test pieces December 10, 1914 from each. The test pieces were heated in a uffie furnace to a constant temperature for type of material, quenched, and the Brinell ss test made. Each series was then drawn to s00 deg. F. in a salt bath and Brinell tests again and then reheated to 1200 deg. F. in a salt and Brinell hardness tests again run. The ts are graphically shown, Brinell hardness ed against test piece size in Figs. 2 to 5, in- t will be noted that the smaller the sample the ter the figure of hardness, indicating that the ler sections are cooled with greater rapidity the larger, and hence more hardness is devel- The same agencies are at work in tool steel. larger the mass the smaller the depth of hard- when quenched unde: similar conditions. Benedicks has shown that for steel of constant mass, the higher the temperature, the greater the rate of ng. Two of his results will be sufficient to cite: t of specimen Deg. C. quench- Cooling time, n grams ing temperature seconds 12.3 845 4.43 2.3 703 5.73 [hese results confirm our experience that in rder to produce the same amount of hardness in a small and large section it is necessary to heat the irger section hotter than the smaller. A commer- ial application of this phenomenon will perhaps be interesting. The authors were recently con- fronted with the problem of finding out the correct temperature for hardening tools made from the same steel in sizes varying from 1/16 in. diameter to %, in. diameter. The temperature-size curve shown was finally adopted (Fig. 6). In other words, a 3/16-in. round will harden at 1395 deg. F., while a %4-in. round bar should be heated to 1450 deg. F.—a difference of 55 deg F. TIME AND DEGREE OF DRAWING TEMPER After the hardening operation has been safely performed, the next important step is that of draw- ng the temper. This operation is necessary for two important reasons: The relieving of abnormal ns set up due to the quick contraction or ex- nsion; the breaking down of the extremely hard nd brittle structure of the quenched steel. The ithors have seen expensive tools such as broaches, lies, ete., actually burst and fly apart due to the that the strains set up in hardening were not relieved by drawing the temper soon enough after hardening operation. If this paper can im- ss upon its readers the absolute importance and ecessity of drawing the temper immediately after rdening, the authors feet it will not have been in In a properly quenched and hardened steel the rdening carbon, that up to 0.90 carbon, exists in form of carbide of iron, Fe,C, dissolved in iron, the solution is known as martensite. If the teel is hyper-eutectoid, i.e., higher than 0.90 car- all that up to 0.90 is dissolved and the re- iinder exists as globules of undissolved cementite attered throughout the matrix. The drawing of temper begins to break down the true marten- structure and as the temperature increases re are formed intermediate micro-structures be- en martensite and pearlite, first troostite, then ite, and finally pearlite. Professor Heyn has ished some valuable results on the decrease of dness on tempering. The results are expressed er cent. of the original hardness: C 2.5 per cent. 400 deg. C.. 70.0 per cent. gy C 14.0 per cent. 500 deg. C. 87.5 per cent ( 41.0 per cent 600 deg. C.. 97.5 per cent. Regarding the effect of time on drawing the THE IRON AGE 1343 temper we submit the following: Standard 1}. in. round A.S.T.M. test pieces were quenched from con- stant temperature into the same medium, and the temper drawn in the same salt bath at constant temperature for five minutes, fifteen minutes, etc.: Maxi- te- Elastic mum Elonga- duc- Bri- limit strength tion tion nell Remarks 228,750 260,137 2 --+» 425 1550-o0i1-800 deg. F. 8 mi 201,125 214,562 11.6 45.4 390 1550-oi1-800 deg. F. 20 min 175,000 183,187 12 19.35 340 1550-oi1-800 deg. F. 40 min Each of these results is the average of four closely agreeing checks. A study of the above table shows that time at the drawing temperature has a marked effect. The act of breaking down the mar- tensite is progressive and not sharply defined. Both time and temperature have their effects. The greater the initial hardness of the piece, the more marked is the effect of drawing the temper. By referring to Figs. 2 to 5, inclusive, the actual values in Brinell hardness are shown. The piece of 0.25 carbon nickel, 5 in. sq., quenched in oil, shows a Brinell of 360; drawn to 1200, a Brinell of 223. The per cent. decrease in hardness is 61. The piece 314 in. sq., quenched, shows a Brinell of 208; drawn to 1200 deg F., Brinell 183, showing a decrease in hardness of only 13 per cent. CHANGES IN SIZE AND SHAPE Thallner states that two kinds of strains are pres- ent in hardened steel: (a) those which occur in steel of small cross section which hardens through- out; (b) those which occur in steel of larger cross- section due to unequal change in volume of the sur face and interior. The first of these also occurs in steel of larger cross-section, but to the greatest de- gree on the surface. Thalliner also classifies steels as (a) those which become shorter and (b) those which become longer or shorter in hardening. The two classes are not sharply divided. In pure carbon steels, the line of demarcation is about 0.90 carbon. In steels which lengthen, an increase in both length and width may also occasionally be observed and the larger cooling surfaces usually become convex. Thallner cites five crucible steels which he examined as shortening and eight basic open-hearth steels as lengthening. The tendency of steel is to become spherical by repeated quenchings. Law, working with a square piece of tool steel 314 in. x % in. x ¥% in., quenched it 550 times and at the end of this work the piece was nearly round in cross-section. The ratio of length to diameter had changed from 314:%% to less than 2:1. An equally interesting observation by Mr. Law was that the steel did not lose carbon or change in any way in composition. Many years ago, one of the authors made several hundred hardening experiments and several thou- sand measurements to study the change of shape. The materials used were cylinders of steel and taps. Crucible steel alone was examined and the follow- ing variables were considered: (a) the effect of original form or diameter upon the diameter after hardening; (b) the influence of carbon on change of form; (c) the influence of initial temperatures at quenching; (d) the influence of length of time of heating; (e) the influence of repeated hardenings, and (f) the effect of annealing previously hardened steels, upon change of shape in rehardening. Obvi- ously when plain cylinders of steel are considered there are four possible changes of shape possible, expansion in length and diameter, contraction in length and diameter, expansion in length and con- traction in diameter, and contraction in length with expansion in diameter. 1344 Under the influence of the variable conditions mentioned above, all four changes were actually produced. Steel was also found which expanded in length on first hardening and contracted indefinitely thereafter on repeated hardenings. Another steel expanded in length on two hardenings and con- tracted on the next two. In a variable carbon series of steels from 0.50 to 1.32 per cent. carbon, the magnitude of the change in length after four hardenings increased as the carbon increased. For the same series it was noted that the volume changes were greater when hardening annealed rather than unannealed bars. The increase in length is greater the higher the hardening heat for all carbons. The deta?'s of this work would take us too far from the purpose of our paper. The point we wish to emphasize strongly is that it is variable conditions that give variable results. Hence, it is of vital importance that steel be fur- nished uniform, chemically as well as physically, and it is equally important that the user employ every possible refinement in the handling of his product. It is only under varying conditions of heat, size, time, composition, etc., that the results vary. Constant conditions give constant results. It cannot be overlooked, however, that constant conditions are not always attainable. The maker of steel cannot control conditions in his customer’s shop and the customer cannot control conditions in the steel plant, and the human element must be con- sidered in both. FURNACES AND METHODS OF HEATING Much has been said regarding the superiority of gas furnaces over oil furnaces and vice versa. The fuel used is immaterial for good practice so long as the following points are taken care of: The furnace and hearth should be of sufficient size so as not to be affected materially in temperature by the introduction of the parts to be hardened. The furnace should heat at a uniform rate. The fur- nace should be of uniform temperature over its entire hearth. The furnace should be run under neutral, or reducing, conditions. A good rough test for this is the introduction of a piece of wood or paper upon the hearth. If the paper or wood burn, the atmosphere is oxidizing. If they char, reducing or neutral. The temperature control must be at all times exact and it must be possible of exact dupli- cation on repetition work. A blacksmith’s fire is satisfactory under good handling, but the difficulty is the fact that for con- stant work it is tov exacting on the operator and requires too many manipulations to secure uniform and continuous results. CONCLUSIONS We have endeavored to enumerate the factors which enter into the every-cay operation of hard- ening tool steel. It is the duty of the user of steel to study these influences and through study and experience to properly weigh the many problems presented in what is frequently considered a sim- ple operation. The various factors are not always of equal importance and must be considered in con- nection with the size and nature of the object being hardened: and the duties expected of it after hard- ening. To expect uniformly good and consistent results from a hardener whom you have not pro- vided with adequate or suitable equipment is un- reasonable. When the question of good equipment in the way of furnace, quenching arrangements and media, pyrometers, etc., has been satisfactorily taken care of, your hardener still has plenty of variables to contend with which are beyond his We hope we have made clear what some control. THE IRON December 10, {41 AGE { z of the variables are and have excited some jy: and desire upon the part of those responsib hardening results to study them as they ha studied them before. The hardener’s task is . cult one, and if we have presented here; suggestions of value our efforts will not have in vain. The Discussion The discussion was opened with a contribut writing from Dr. Henry M. Howe. He regarde: paper as a very important contribution to the k: