Document V3M3M8X605zrRY4dVqO9GK0Yp

LEAD INDUSTRIES ASSOCIATION asa MADISON AV KNtll NCW YORK 17, N.V. September 3, 19^0 SUBJECT; COnTOmOCS EXTRUSIOH OF LEAD ALLOY CABLE SHEATH To Members of tbe Lead Industries Association; Attached Is a preprint of a paper to be presented at the fall general meeting of the American Institute of Electrical Engineers at the Morrison Hotel, Chicago, Illinois, on October 10, i960. This paper represents the successful conclusion of the research program Initiated by the Coble Sheathing Task Group of the Lead Industries Association several years ago In cooperation vlth the John Robertson Caspany, manufacturer of lead extrusion presses. The purpose of the research vas to develop a continuous extrusion press which could successfully extrude the alloys ccrmonly used for cable sheathing In this country and thus help to produce better and more economical cable. The research project vaa originated by the Lead Industries Asso ciation in Kay, 1958, and carried to conclusion by the LIA Expended Research Program. The LIA has purchased sufficient copies of this preprint to circulate It to the proper engineers onong cable producing and consuming companies. Additional copies may be obtained from LIA by members at 50 cents per copy as long as our supply lasts. Very truly ycurs. RLZtJRH Alt. Secretary *-1^4335 *t*~`l> 11 " n ^ ~ Transactions Paper e (Reviewed and Accepted for Publication) i f m ti DEVELOPMENT OP A CONTINUOUS EXTRUSION MACHINE FOR SHEATHDC CABLE WITH LEAD ALLOTS Schrade F. Radtie Htaber AIEE Lead Industries Association Kev York, H. I. C. J. Snyder Konncaber AXES Anaconda Vire A Cable Co. Hastlng3-on-Hudson, It.Y. C. C. Childress Nomember AIEE John Robertson Co., Inc. Brooklyn, H. Y. r 1 A paper recemended by the AIEE Insulated Conductors Committee and ap proved by the AIEE Technical Operations Department for presentation at the AIEE Fall General Meeting, Chicago, 111., October 9-11*, I960- Manu script submitted June 13, 1900; made available for printing August 26, I960. Prim I JO T Msbn 11.00 T# NAMmbtn (5^ per copy idditiorul if SlT%i due cnsilintf desired) AU Rights Reserved by the Amenetn institute of EJectrical Engineers 33 West 39th Street, New Yori 18, N. Y liiho in USA Ptptr Now 60-1219 Discussion in Duplicate Due October 26. I960. *HJ't 1 niji- rvs!^peMr ^ 2036.01 i-. - t j .av'*WWilwaw<a"Wf un. j nr PMfi1 -w^Biwwiwwwi'.i xp LIA 2433 6 ,jpj wf mw -iw MiwpM jPj w 'i gyw i mym w Schrade F. Rodtke Member AIEE DEVELOPMENT OF A CONTINUDUS EXTRUSION MACHINE FOR SHFATHIHO CABLF. WITH LEAD ALLOYS C. J. Snyder Ron-aenber AIEE C. C. Childress Non-member AIEE f. INTRODUCTION Leed hardly needs an Introduction as cable sheathing material. It has been vldely used as sheathing for overhead and underground cable since veil before the turn of the century. Among the recoeaendatlons for It are cany of the characteristics vhlch are fundamental to good cable performance. While nearly pure lead (alloys containing only a little silver or copper) is vldely used for sheath, better properties are often obtained by alloying It vith other cetals In small percentages. Thus, nearly all of the lead sheath used In telephone service Is an anttmonial alloy; much of the lead sheath used for pover cable is an arsenical alloy. In the conventional methods of producing cable, hovever, there are some problems In pro ducing sheaths of these lead alloys vlth higher percentages of secondary constituents. It) appreciate this, one must look into the methods of fabrication. One ccmon method uses the Intermittent extrusion press. In this press molten alloy is cast Into a vater-Jacketed cylinder and caused to solidify. Then a piston advances Into the cylin der, causing plastic flov. Thus the lead Is forced Into a die cavity and through the annulus between the die and the cable core, vhlch Is drawn through by the extruded lead sheath. This basically simple scheme has a cusber of dravbacks vhlch, while not of major proportions Individually, are often of controlling Importance In specific applications. Screw driven continuous extruders have also been used to sheath cable. Until the machines developed through this research, these have been confined to the softest lead alleys--silver-bearing lead and ease types of copper-bearing lead (though not all types of screw extruders will handle even this). Most of the desirable alloys have a vide melting range (up to about 50 F) dileh cakes attainment of a steady-state ccollngeastlng-extrualcr. balance quite precarious. Moreover, the harder solidified alloy re quires so cuch f----e for extrusion that the screw cannot transmit It smoothly for any practical length of run. Attempts to extrude the alloy on these screw extruders re sulted in stalling and Jerklncss. Even If the sheath vas produced at all It vas usual ly unserviceable. f. * A problem of overvhelxlr^ Importance In extrudlr lead alloys continuously la segregation of the alloying components. As In rone refining such materials, the solid Is purer than the liquid with vhlch It Is In contact. Action of the screw advances the purer solid, leaving behind a liquid containing more of the alloy component than the solid contains. Under extreme conditions regions have been found vhlch are more than ten times richer In this component than the starting material. Even fairly short runs have produced droas-llkc or metallic accumulations on the screv and other parts of con * ventional screw extruders used to make some alloy sheaths. i f l VMM* w1 < ni MW j I <i a <mw ip fmmr Mae "W" mm*: LIA24337 .. ... -2 - Thus It can be seen that there is rocn for Improvement In the process of producing o lead sheath. It is also obvious that vhile a continuous screw extruder would seem to overcome the drawbacks of the Intermittent press, until now It has had shortcomings of its own which have made It altogether impractical for producing the most desirable lead alloy sheaths. This paper Is concerned with the research which resulted In a successful continuous extrusion machine for these lead alloys. DEFINING THE PROBLEM Aa early as five years ago a task group was formed within the Lead Industries Asso ciation to look Into ways of Improving lead sheathed cable. It vaa apparent that alloys existed which would provide better creep strength and high tensile strength. Jut It was also evident that none of these alloys was entirely suitable for continuous or Inter mittent extrusion. Therefore, the task group undertook two types of research: First, to find better alloys and alternate lead materials for such uses. Four pro jects In this direction are still active or already successfully coexisted. Second, research to develop a continuous extrusion machine capable of working existing higher alloys of lead. A program similar to this had been under consideration by the John Robertson Company of Brooklyn, H. T. Vork on the development, therefore, was undertaken as a Joint effort of LIA and Robertson. DEVTIMPING TOE EXTRUDER 4 There are two principal types of continuous screw extrusion machines. They are conveniently described as horizontal and vertical screw machines. The vertical screw machine was selected as the most promising for this research. The conventional vertical screw extruder has this general plan (Fig. 1): Lead alloy Is melted la a kettle which will hold 9.000 pounds of lead. In the kettle It passes two baffle plates which prevent dross from passing through the connection pipe which feeds the extruier proper. Molten lead flows through the horizontal connection pipe and enters the lower end of the screw chamber. Just above the entrance the lead alloy solidifies. Vertical grooves or flutes In the inner wall of the screw chamber prevent the solid lead tube from rotating while the flight of the screw causes It to move upwards (In plastic flow) as the screw Is rotated. Qoerglng from the top of the screw chamber the lead flows Into a die head where the stream Is split to flow past both sides of a zauxlrel to rejoin at the top, forming a continuous tube. At this point the configuration of the die head forces the lead alloy to make a right angle turn, flowing now horizontally. The cable core is surrounded by the lead tube and carried along by It. Electric beaters and cooling water passages hold the desired temperatures at critical points along the route of the lead flow. As has been pointed out, this t)pe of extrusion machine Is capable of producing good quality sheath from silver-bearing lead and sooe grades of copper-bearing lead. As early as 1951 It was tried on F-3 arsenical alloy but after a short run slippage and stalling occurred, due, probably, to segregation. In order to do a smooth Job with F-3 and the other desirable alloys a complete revision of the temperature control ystam was made. Not only waa a great deal of heat ing and cooling capacity added to that of the conventional machine, but It was arranged LIA24338 XT -3- to that each anil surfaca area along the rout* of lead flow waa brought under more accurate control. Temperature Controls of the Extruder Starting at the melting kettle there are two groups of electric heaters with a total heating capacity of 90 kw under the control of two thermocouples. One couple la located at and controls heat to the Input end of the kettle. The second, located near the outlet, controls heating there. The outflow temperature at the kettle la confined to a narrow range by means of a'temperature control Instrument which switches the heat ing elements from delta to wye connections. Leaving the kettle, lead flows through a connection pipe with a 2 kw bayonet heat er under control of a thermocouple near the exit end of the pipe. This pipe delivers the lead to the lower end of the vertical screw chamber -- an Inherently safe design since In the unlikely eveat of failure of the six autoeatlc temperature controls and seven manually controlled cooling colls from this point on, molten lead could only rise to Its level In the kettle which Is safely below the top of the screw chamber. The screw housing, about three feet long. Is divided Into three controlled heat ing zones. Electric heaters with a total capacity of 20 to 27 kw are carried In machined spiral grooves surrounding the housing and are controlled by three of the eight thermocouples mounted in a vertical row. In addition, there are five water cool ing channels machined Into the housing wall. The water flow la controlled manually according to a preset schedule by means of rotameters. Such elaborate provisions for temperature control bespeak a difficult heat pro blem. Indeed, thla la the case. Consider first that this extrusion machine must operate with a variety of alloys of varying melting ranges whose metallurgical proper ties are controlled. In part, by their cooling and solidification rates. Furthermore, the solid alloy Is forced to flow past the screw and screw housing wall surfaces (approximately 5 sq. ft. In all) solely by the force exerted by the screw. Under such conditions a large part of the applied 50 hp Is converted to heat by friction. Con trol of temperature In the screw chamber Is the most critical requirement for a success ful operation. how the lead is forced to flow Into the die head itself. Here again there are two water cooling circuits and two of the three thermocouples In the head control heatera at the top and bottom of tbe assembly. First the lead flows over a cocplex man drel which forma the inner surface of the sheath. Emerging from the end of the man drel It passes over a core where the pipe It formed and then through a water-cooled die which regulates the thickness of the sheath. Most of the' cooling In the die block Is accomplished by the two lover water cooling colls under rotameter control. These remove the heat generated by friction In the die block and hold the temperature to about k50 T. without this cooling tbe die block temperature would rise to about 560 r. The die block and mandrel used In this nrchlne are quite similar to tboss used la the Intermittent press, although they lie In at Inverted positloa since lead Is fed from beneath rather than from above. Alternate Pleheadc Alternate die blocks cf the sizes shown can be used interchangeably on the machine to meet any maximum cable diameter up to S In. Required beating capacity la the die head for tesgwrature control there depends on the site of cable to be sheathed! rh l i o 1 *7* i . - i n I Si l i snai Hi L IA24339 Ht mmlrnTim flip fcgt--<V h<' Yl-| 'fT1! 1 - *>irifca ' 9 .V. Schedule of die block sites and heating requirement* Cable site Die block site Heating required up to 2 in. OD 7 In. 20 kv Up to 3 up to a up to 5 9 11 12 30 UO ao Specifications of the Machine Development work on tbit extrusion machine vat carried oo with a JO hp 1750 rpa motor. Uhlle this was workable, experience hat shown the desirability of more power and a 75 hp motor vat Installed on the prototype. Proposed larger units will be powered by 100 hp motors. In steady operation, the combination of heating and driving power for extrusion of sheath on 2 In. cable will average about 120 kv. The motor It mounted vertically beside the screw housing (rig. 2) and drives the tcrev through a 70 to 1 gear reduction train. Both gears and thrust bearing are force lubricated and cooled by oil. The prototype's tcrev housing vas drilled and piped with water cooling circuits and flexible hose connections (Fig. 3) to permit 35 cooling combinations. As a result of this research, present commercial units are equipped with six cooling combinations which provide all of the flexibility necessary. The housing carries a liner with from 21 to U2 vertical flutes to prevent rotation of the lead by the screw. There are eight thermo* couple locations In the housing and three electric heaters to be controlled from three of the thermocouples. In addition there are heating elements in the base of the housing which are also to be controlled by the thrust bearing area thermocouple. Cooling of the screw housing Is controlled by five rotameters calibrated to the nearest 0.01 gpa with a maximum flow of 0.11 gpa to govern flow of cooling water through the five cooling circuits within the housing well. Die head and die cooling are achieved by slailar cooling water passages and rotameter coatrol. Instrumentation Is divided Into three parts. All temperature Indicators and con trollers are located on a main panel (Fig. U). These Include the following: 1. lead melting kettle -- two off-on controllers svltchlng the heat circuits frcn delta to wye (90 kv capacity) 2. connection pipe -- ooe off-on controller for 2 kv bayonet heater 3. screw housing -- four off-on controllers with Individual control of four heat ing zones starting below the point of Introduction of the lead and extending to the top of the bilng (20 to 27 kv combined) k. die block -- two proportional controllers for separate control of top and bottom teaqperati're of the block (capacity varies with site) In addition there Is a seven-point scanning switch for checking the te^wrature at other thermocouple points. -jM"r USJW-M*'.' I .U III* 'll LI A2A3A0 yktrtbi -5 - The second group of Instruments Is the cooling control section. This Is mode up of seven rotameters, each with a range of 0.01 to 0.11 gpm. Ihe third group of Instruments measures a variety of other operating variables: 1. cable speed record*-, -- 0 to 150 fpsi 2. motor load -- Indicating and recording ammeter 3. motor speed -- Indicating and recording tachometer U. running time recorder 5. vatt-bour meter 6. associated oil and vater pressure gages PROVISO TOE METHOD After the new extrusion machine had been designed and built. It was first tested with common desilverized lead (ASTM Spec B-29 -* Pig Lead), the material commonly ex truded by existing "continuous" machines. In addition to allowing the mechanical opera tion to be checked, this provided a test of the temperature control system. Since the operation and efficiency of this type of machine Is dependent on differ ential cooling. In somewhat the same vay as any continuous casting of metals operation, small temperature adjustments at various points can have lncocraensurately large effects. Continuous extrusion recembles any continuous casting of metals except that. In addi tion to the casting of a solid continuous ribbon, the casting must finish at a suitable hot working temperature and sufficient force must be applied to the ribbon to extrude It through a die Into a tube. When operations were adjusted to a point where common lead was extruded Into 2 In. diameter pipe at the comparatively rapid rate of 85 lb per minute, the machine was considered operational and the experimental work on lead alloys was cocnenced. Extrusion of Arsenical (F-3) Alloy F-3 alloy arsenical lead was the first alloy tried In the new press. Considerable experimental development of operating techniques was needed, because extrusion of the alloy was slow, erratic, and unsuccessful through the first two months. Eventually, however, a favorable combination of heating and cooling circuits was found to overcome the solidification range of the alloy, as contrasted with the sharp melting point of desllverlted lead. After this progress was rapid. Refinement of controls and experience In operation finally made It possible to stop and start the extruder at will and rapidly bring it to a steady extrusion rate of about 35 lb per minute. Faster operation was obtained at times -- as, for exasqple, one run of 5-1/2 hours where a steady output of 52 lb per minute was recorded. Factors limiting output appeared to be roughness or checking of the sheath sur face from excessive temperature of the alloy as It came through the die. High speed* also caused slippage or momentary hesitation of the output. The excessive temperature problem was similar to the difficulty in extruding arsenical lead too fast la a hydrau lic press. Thus It Is not a difficulty solely attributable to the sc rev-type extruder*. L IA2434 1 -6 . Means of lovering of the die block tenqperature and development of a vater cooled die had been vorked out by the end of this phase. These, In turn, increased the force needed for extrusion, and increased the occurrence of slippage vhlch overloaded the 50 bp motor drive. To check this difficulty, the press vas dismantled during the experiments and the screw vas examined for segregation, alloying, or pitting. Its surface vas found to be clean and smooth except for one 6mall area at about the middle of its length where a lump of alloy adhered for no apparent reason. The slippage vas, therefore, Judged to be caused by friction. Provision vas then made for Injection of sodium stearate Into the lead feed pipe where It would be carried Into the screw flight as a lubricant. Injecting of a few grams of sodium stearate every 2 or 3 hours stopped the slippage. This required halting the extrusion for 10 to 15 minutes each time, however, and often resulted In the production of tiny flakes of dross*llke inclusions scattered along the surface of the next $0 ft of pipe extruded, (it is possible that injection of a gram every 15 minutes without stop* ping could be arranged for non-stop operation.) Extrusion of F-3 alloy vas started about November 1, 1958* After almost constant ex* truslon up to about April fl, 1959, during which time the metal had been extruded and remelted cany hundreds of times, It vas thought that the metal might be dirty, so the kettle vas drained and refilled with new metal. The new metal had no effect on the opera tion and control of the extrusion. Samples of pipe were selected from extrusion on 12/18/58, and again on 1/30/59* analyses of which are shown in Table I. Dip samples of alloy from the 3 compartments of the electric melting kettle feeding the extruder were taken on 1/30/59* Although the kettle had not been skimmed from 11/1/58 to 1/30/59* there vas no appreciable dross accu mulation except about l/l6 in. on the outlet compartment, which was also sailed. Table I F-3 ALLOT - CHEMICAL ANALYSES Required 0.10 to 0.20 Arienlc, % Pipe Sample of 12/18/58 Pipe Semple of i/3Q/?9 0.127 o.Uo .05 to .15 Tin, .0$ to .IS B1south, % .097 .06 .109 .06 Kettle Samples of 1/30/59 Melting Middle Outlet Compartment Compartment Compartment 0.132 0.133 0.130 .110 .116 .105 .06 .06 .06 .01 Max. .01 Max. Antimony, f <.005 Copper, % <.005 <005 <.005 4005 <,005 <,005 4.00} <005 <.005 1 MIJI "mm Fm-wjaw wwi i UJJ'W LIA24342 W -7- Wl II r-3 ALLOT - TEWSILK k BgTO PBOPgmiS Sample! of 12/18/58 Tentlit Strength P1 Elong. In 2.15 In. i No. of 90 Benda rPCEA Bender 53 Ib/mln 2260 30.0 - 30 Ib/mln 2305 36.6 - 35 lb/mln 2270 29.0 - 35 lb/mln 2330 33-k - (vlth alight water cooling on die) U2 lb/mln 2265 39-9 39 to 55 Sample! of 1/30/59 6. Pipe cut after .36 minute* extrudoa 36 lb/mln 36 lb/mln 2263 2240 27.1 27.4 45 to 51 41 to 51 36 lb/mln 2160 34.4 41 to 51 NOTE: Tensile specimens were machined ring* which were pulled over oval shaped pins for gripping with a cross head speed of 0.5 In. per minute. lhe grain structure of ring-shaped cross sections of all the various P-3 alloy pipe samples appeared similar to that of any lead sample produced oa a screw-type extruder, except for a smaller grain size. There were shadowy patterns of flow lines present la the sides of the tube vail, ending In "tongues" near the top and bottom of the section. These flow lines appear to be produced by the Joining of successive flights of cast ribbon as It leaves the screw and Is compressed Into a solid mass In the die block. Tiny particles of oxides, which fora on the surface of the ribbon ae It slides up the screw, are found in some of the flow lines. (The tongue-shaped pattern Is produced by flow of the lead In the die block, as It splits over the bridge and core tube and velda together again to fora a pipe.) The flow lines are never severe enough to restrict grain growth across them and, therefore, should be haralecs to mechanical performance of a cable sheath. Less noticeable were the die veldt caused by the die block. Streaks of patterns that could be attributed to alloy segregation In the structure were absent. Examples of r-3 alloy pipe grain structure are shown In the micrograph*. Figure 5 shows the general structure of sample fl (Table II). The ring In the center ehovt * whole cross sectloo and the micrographs show the areas to which they are o mjm1  iyww- ml < w -. iMgwwwimi'sssmsmui LIA2A3A3 -a . tangentially mounted, at a magnification of 20 diameter*. The section was etched rather deeply to bring out the flov lines and the surface got a little rough, but It shows the o rather uniform grain and the lack of segregation. Figure 6 shove the general structure of sarple #9. Both these samples exhibit a high contrast veil defined grain characteristic of air cooled soft F-3'alloy. Figure 7 shov* the structure of sample #5 at 250 diameters. The surface was mlcrotoaed and llgitly etched for this examination, and shows the rather fine, almost India* tlnct grain boundaries characteristic of arsenical lead, vlth no film of oxide or other segregation In the grain boundaries. The scattered small black particles are some form of arsenic precipitated from solution by the slow cooling. Figure 8 ahovs sample <8 after laboratory heat treatment. The appearance of the flov lines became more noticeable after heat treatment. This 1* not a segregation of alloying elements, but rather an agglomeration of the tiny oxide particles. All these samples were collected before the use of sodium stearate was begun. After about 5 months of experimenting and over 150 hours of actual extrusion, dur ing which there were some all day runs of pipe. It vaa felt that all difficulties were pretty veil overcome. It appeared that the continuous extrusion of F-3 alloy In the new extruder was under control and would be coemerolally feasible. Discovery of the use of 60dlum stearate In tests during the latter part of this vork appeared to be a big step In keeping the screw clean and maintaining steady operation. On April 8, 1959, two tO-ft lengths of 3/C 500 MCM 15 kv solid type paper cables were sheathed. Sodium stearate was Injected Into the extruder, vhleh was then brought up to a speed of 9 fpn for 8/6U In. wall 2.31 In. O.D. sheaths (32 lb/mln), and the cable* fed Into the die block one after the otner. The die block was held at k}0 F and o a small amount of water cooling was used on the die, but no water cooling oo the cable. The extruder ran without hesitation and a smooth tight sheath was obtained. Oie opera tion appeared routine. Results of chemical and mechanical tests on this sample are listed In Table III. Table III F-3 ALLOY CABLE ShZATH Chemical An&lyals Tcnille Properties After Heat As Extruded Treating Arsenic, % 0.150 Tin, % .101 Ultimate Strength, pel elongation, % in $.10 In. 2,**75 2e.2 2,820 Vl.J Bismuth, i .10 *o. of 905 Bend* (vlth IPCEA Bend Tester) 35 to 1.7 17 to 33 ' Copper, % .00 Concentricity, f 96.8 - Tensile strength of the sheath vas a little higher than that of the pipe, but the water cooled die did not have a quenching effect on the alloy. The sheath material re sponded veil, hovever, when a sample was subsequently quenched from a suitable working 'MM ^ LIA2A3AA -9- temperature In the laboratory. Therefore, quenching vat considered unimportant for the present experiment* as suitable quenching could be provided. If desired. In a commercial Installation. Since high fatigue strength In bending la the moat Important characteristic of arsenical lead sheaths, a length of cable vas Immediately tested In the machine described by Hlckemell, Jones and Snyder with he following results: Movement Inchea 1-1/2 2 Actual Strain i 0.241 390 Cycle* to Failure 21,432 13,6l6 Increase in Edameter * 1.5 These data compare well with the data presented In the above publication, and with subsequent data on file. The "continuously extruded" F-3 alloy cable sheath thus pos sessed fatigue strength similar to F-3 alloy sheath made with a hydraulic press. The grain structure of the sheath sample was not as uniform as that of the pipe, but the same effect 1* experienced with sheathing extruded from a hydraulic press. The flow lines are a bit more prominent than In the pipe, perhaps because of the sodium stearate lubrication added Just prior to extruding the sample. No mechanical weakness was appar ent. Although no creep test data are available. It certainly appeared that this cable sheath had the characteristic chemical, metallurgical and mechanical properties of F-3 alloy cable sheath and was a satisfactory commercial product. Extrusion of "Hnblrloy* Arsenical Alloy "Hnblrloy" arsenical lead alloy was then extruded Into pipe with the new extruder. Since the machine operated well with nearly the same control settings as used previously vlth F-3 alloy, no difficulties vere experienced. Both the sodium stearate lubrication and the water cooled die and die block were used during extrusion. Extrusion speed was similar to that for F-3 alloy, with perhaps slightly less power required. A tangle of pipe from this material was analyzed with the results listed In Table IV. Table IV HABIKLOT PIPE DATA Chemical Analysis Tensile Properties Arsenic, % 0.12 Ultimate Strength, psl 2250 Tin, i 09 Elongation, In 3.03 In. 36.0 Bismuth, % .01 No. of 90 Bend* (with ETCEA Bender) 39 to 47 Copper, % .025 Concentricity, Jl 93-J The grain structure of a cross section of this pipe had a characteristic appearance similar to that of F-3 alloy. W'WjJp SUP- miwsuati. 'mil LIA2A3A5 V rtT fn 'rfcfaM^ai.a-l^to,,lki. i.iu -------------------------------------------------------------------- .>. ... u,_._.-^._ . --x --^ --. >... 10 - Although only about 17 hours of actual extrusion tine were devoted to this alloy, the ease of operation Indicated that commercial extrusion should be practical. Extrusion of Tellurium Alloy "Tellurlun Lead" arsenical lead alloy vaa next extruded. The machine started easily under the same control settings as used for the other arsenical lead alloys, but more force appeared necessary to maintain extrusion and the output vss not as steady as that of previous runs. A sample of pipe from this material vaa analyzed, vlth the results listed In Table V. Table V ` l t TELLUBIUH LEAD PIPE DATA Chemical Analysis Tensile Properties Arsenic, % 0.105 Ultimate Strength, psl Tin, % .12 Elongation, % In 3<09 In. Tellurium, $ .00 Ho. of 90 Bends (with IPCEA Bender) 2435 M..5 33 to 49 Bismuth, 1> .12 Copper, $ .00 Concentricity, % 97.3 The grain structure of a cress section of this pipe appeared different from those of the other arsenical leads. Various methods of etching were tried but the result vaa the sane. In addition to the usual pattern of flow lines, certain areas In the sides of the - section always became pitted and darker, and dark radial bands showed at the top end bottoe die welds. i It was noted that these dark areas gave somewhat lower bend test results than the lighter areas, although the average elongation on a tensile test was very good. Eased on about 30 hours of actual extrusion, the snchlne should be able to extrude this alloy. Sctruslon of Antloonlal Alloy Antimony lead alloy was then extruded. The machine started very easily with the die block at 450 r, and Its operation was very steady, but the output vas lower than for the arsenical alloys with the power available. Here power was definitely required for this alloy. The pipe extruded at only 35 to 30 lb per min was noticeably smoother. Whether this alloy would have given trouble with roughness at the die when extruded at 3$ to 4$ lb per min, as the arsenical# did, Is uncertain. ( A sanple of pipe from this material vat analyzed vlth the results listed In Table VI. ppm LIA24346 -n- Table VI AHTTHCTTf LEAD PIPE DAT* Chemical Analysis Tensile Properties Antimony, 0.99 Tensile Strength, pal 3155 Copper, % 0U Elongation, in 2.67 in. 38.1 Blemith, % .068 Ho. of 90 Bends 17 to 29 Arsenic, $ .00 Concentricity 95-8 1 Tbe grain structure of a eroaa section of tbl* pipe appeared different froa those of the arsenical leads because of the different etching characteristics of antimony lead. It appeared that the pipe had a rather uniform grain except for the die veld areas. The flov line pattern vas similar to that found In the other alloy pipes, lhe dark areas around the tips of the flow lines probably Indicate some precipitation of antimony rather than segregation. This drastically affects the etching properties of the alloy. It may be that faster extrusion or readjustment of the cooling circuits would have overcome this. i vas noted from the bend test data that these dark area* vere not as plastic as the lighter areas although the average elongation In a tensile test vas good. The lover aver* age number of bends vas to be expected, of course, because of the higher strength (and hardness) of this alloy. Although only about 10 hours actual extrusion time vas spent because of lack of paver, it appeared that vlth a 7$ hp motor, this machine should be able to extrude this alloy satisfactorily In commercial operation. Extrusion of Other Alloys Chemical lead vas then extruded vlth the special machine. Although this type of lead Is reputedly more difficult to extrude vlth this type of machine than the acid-copper lead. It vas extruded freely under the same operating conditions as used for the arsenical alloys. With the use of sodium stearate Injections, no build-up of copper on the screw vas noted In the short time of operation. A saaple of pipe from this material vas analyzed vlth tbe results listed la Tbhlc VII. Tsble vn CHEMICAL LEAD PIPE DATA Chemical Analyels Copper, % B1 smith, % 0.057 .000 Silver, f .005 Rlckel-Cobalt, $ .00]k Tensile Propertlee Tensile Strength, psl 1930 Elocgatlon, $ in 3.11 la. 304 Ho. cf 90 Bends M to 51 Concentricity, $ 964 PS iwwwiiwpg> tmmemmnif WSgMMIIiUJ.il LIA24347 - 12 - The grata (tructure of a croaa section of this plpa vaa rather uniform and ahoved only faintly the usual pattern of flow line* formed by the extruder. ) lhe grata elze v b* larger than would be expected of the alloya. Acid copper lead vae not extruded with the new nachlne becauae tt te eatlefactorlly extruded by eeveral cable makers with a similar vertical ecrew machine of conventtonal design In regular cceiaerclal operation. Since It was obvious that the new machine would extrude this lead alloy satisfactorily. It was not tested. A san5>le of the cable sheath was analyzed, however, for caparison with the other saterlals. These data are listed in Table VIII. Table VIII DATA TOM AKALYSIS Of ACID-COPPER LEAP CABLE SHEATH Chemical Analysis Tensile Properties Copper, f 0.065 Tensile Strength, pel 1605 Bleauth, % .01 Elongation, In 2.5 1n. 35 r Antlmoay, f .00 Bo. of 90 Benda 39 to *3 -- S )[>l) |Hl il i i u . i iJ Wi Tin, % .00 Concentricity, f 96A The grain structure of a cross section of this cable sheath was very uniform, but the typical pattern of flow lines formed by a screw-type extruder were present. In fact. It appeared that the flow lines were more numerous, which of course might be expected from our explanation of the cause of these markings on an etched metallographlc specimen. The standard vertical screw extruder has a 12 flight screw as compared to the 9*1/2 flight screw In the special experimental machine. The Joining of successive flight! of cast ribbon as it leaves the screv and Is compressed Into a solid mass In the die block leaves welds that can be disclosed by polishing and deep etching. When these velds are free from oxides and segregation or second poase materials, they appear to have no effect on the mechanical properties of the sheath, as shown by the very uniform bend values end good elongation In tension for most of the samples. concmsiows 'W W |W w h iw i h ii, i| npip; The formal testing and development work on a continuous extrusion machine for a11 desirable lead alloys for cable sheath has been completed. The results have been satis factory and the machine Is now in coezaerclal use. It Is believed that all the funda mental problems have been adequately solved and that any future changes In the design or methods of operation will be concerned only with marginal areas such as reduction of maintenance or reducing the Investment needed for continuous sheath extrusion. In reviewing the previous difficulties of producing superior lead cable aheath the most obvious conclusion to be drawn from this work la that it la now possible to con tinuously extrude cable theath of any lead alloy coesaonly used. Since operation la con tinuous, It requires a minimum of setting up and supervision. And within the normal range of Industrial usage, the equipment le safe and convenient. Since the cable le produced continuously there are r.o press welds or periodic changes In the sheath. Indeed, the 'heath 'hows a remarkable uniformity both in lte gross aipecte and under close metal'.examination. Of primary importance la the >- *33 # I,fl" * ' "I^ , ii|iii^ ^ W iwairawHipw LIA24348 mnU inali'i - 13 - fact that thla is true of the concentricity of sheath and core. Production runt of cable to have 0.090 in. sheath have consistently tested 0.090 to 0.093 In.; in runs where a minimum of 0.062 in. vat the specification, the results were 0.C62 to O.O63I In. While the continuous extrusion machine has not yet been extensively used for sheath ing cable employing polyethylene and other insulation which degrades at high temperature, the very fact that this unit keeps the cable moving continuously it a step towards a foolproof method of doing this. Beyond the original goals of the program It has been found that the alloy of the sheath is much cleaner and much more free of oxides than that produced on any convention al sheathing equipment. Ibis should mean that cable produced by this method will have an unusually good sex-vice life since there are no weak points Tor physical or corrosive attack. It will be several decades before sufficient data accuoulite to prove this point. CAPTIONS FOR ILLUSTRATIONS Figure 1 -- An overall schematic of the continuous lead alloy cable sheath extrusion machine. In general plan it Is similar to conventional horizontal screw machines. The principal changes have been a modified screv and screw bousing, increased power, and the tesperature measuring and control equipment. (The die head has been rotated through 90 in this schematic. Actually, the cable core Is fed from behind the plane of the Illustra tion and the sheathed cable emerges toward the reader.) Figure 2 -- The continuous lead alloy sheath machine Installed at the Yonkers plant of Phelps Dodge. Melting kettles are at left, the screv housing at center and the drive motor Is at right. Figure 3 -- This was the experimental set up for temperature control of the screw housing. Connections for heating, cooling, and monitoring temperature are shown. Though this elaborate control system was necessary for the reseax-ch, production equipment has been considerably simplified (bee Figure 2). Figure 4 -- The control panel. At left, all temperature controllers and Indicators. Rotameters and water and oil gages at center. Recorders of temperature, production rate and associated motor control equipment are at right. Figure 5 -- A sample (#3--see text) of F-3 alloy extruded by the machine. A whole cross section of the sheath Is shown with micrographs of the wall adlacent to the sections of the sheath from which they caxae. Note the rather uniform grain structure and absence of segregation. Actual sheath diameter Is 2 In. Figure 6 -- Another sample (#8--see text) of F-3 alloy sheath produced by the machine. Compare this vith Figure 8. Figure 7 -- A much enlarged micrograph of F-3 alloy sbeath produced by the machine. The actual dimensions of the area shown are 0.013 x 0.017 In. (the micrograph was made at X2J0). Crain boundaries are rather fine and almost Indistinct as Is characteristic of arsenical lead. No oxide film or segregation It evident at these boundaries. The scattered black particles sxre some form of arsenic precipitated by the slow cooling. Figure 8 -- The saxse sample (#0) of F-3 alloy shown In Figure 6 after laboratory beat treatment to bring out the flow lines. These lines are not due to segregation of the alloying elexeenta but to agglomeration of oxide particles. i '.IMP lt-IsJM.J t*r*m*m EUUIIW 1 wm G LIA 2 A3 49 - Ik - ACKROVLEPG EXERTS o Hie work reported In this paper wi a Joint effort of the Cable Sheathing Talk Group of the Lead Industrie! Association and the John Robertson Coopany, Inc. The members of the task group vere: Chairman A. A. Smith, Jr. Research Laboratories American Smelting A Refining Coapany South Plainfield, Hew Jersey Members Irving L. Barker Cerro de Pasco Corporation 300 Park Avenue Rev fork 22, Hev York Edwin J. Harrell Hablrshav Cable A Wire Division Phelps Dodge Copper Products Corporation Yonkers, Rev York G. M. Bouton Bell ^telephone Laboratories Murray Hill, Hev Jersey C. J. Snyder The Anaconda Wire A Cable Company Rastlngs-on-Hudson, Rev York H. A. Hoover John A. Roebllng's Sons Corporation Trenton 2, Rev Jersey Robert J. Wit The Okoolte Company Passaic, Rev Jersey W. T. Isbell St. Joseph Lead Company 250 Park Avenue Hev York 17, Rev York Finally, the authors wish to acknowledge the assistance of Mr. Bruce Fader, Lead In dustries Association, In the preparation and editing of this paper. a awtas-w--s is1- PUJiPBUIMUm.l AI A* mu j E ufti in 'iw jMjqwynqi LIA24350 THlRMOCOUPlE CONTROUmC IHUMOCOUFU TOf SPlWi HUTU MlDDU SWMl HUTU LOMU SPIRAL HUTU THRUST SCARING AJtU y.RM HUTU Continuous Lead Extrusion Machine O msm- myjts&p m ***** LIA24351 rI<*! i^Uh Fig. 3. Cooling and I nstrusentation of Screv Housing on Pilot Unit 4 0 WHIT Fig. I*. Master Control Panel for Extruder .fJf'WIHM1 i {i i' I * 6' t "M r LI A24352 "Is Fig. 5# Crain Structure of F-3 Alloy 2" I.D. Pipe Sample Ho. 3 Fig. 6* Grain Structure of F-3 Alloy Pipe Sample Ko. 3 ^...H'UI'^ I..UULJWI1 iiijiii.n i j i ip'iwau' -V --- *- - o ----- _--- -- L IA2 4353 Fig. 7* Micrograph F-3 Alloy Sheath Sample Ho. 5 250 X f' i Fig. 8* Crain Structure of F-3 Sheath Sample Ho. 9 After Laboratory Heat Treatment r i mem** J 'P I! iiipwi ' "-T'-r >- n i i "lllli- j u j u 1 'i LIA24354