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UNTVERSHTC USRARIES
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^T 100 pi'
z^ndrews, E. E. ^
Investigation of Special m_
Steels m\
For Use In Ubranf Only
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A Thesis ProsontbU lo the Presiiient and Faculty of ^\mour Insti\-U'ce of Technology for ^'".le degree of Bachelor of Science in Chemical J'ngiiiaoring
Subraitted by
L. Z. Andrev;s and F-oy A. '/inser.
Juno 1908;.
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ILLINOIS iNSl II U 1 1 Uh f ECHNOLCXiy PAUL V GALVIN LIBRARY 35WEST33RDSTREr
An Investigation of SPECIAL STEELS
By E. E. Andre-js and Roy A '^Tinser.
Ol3TLIi>IE II©EX TO THESIS.
I. Object
II Method
(A) Clieiaical Analysis
(a) Preparation for Analysis
(b) Aiialysis for
(1) Sulphur
(2) Silicon
(3) Tungsten
(4) Ilaiiganeee
(5) Cliromium
(6) Phosphorus
(7) Carbon (3) Kick el (9) Vanadium
(10) Uolybdenum
(B) PlT/sical Testa
(a) Tensile Strength
(1) By Pulling
(2) By Bending
(C) l&chanical Teste ni Data
(a) Cheiaical
(B) Physical
(C) Mechanical IV Discussion
(a) Gheoical
(a) Influence of constituents on steels
(b) He:hod of Lianufacture
(1) Crucible
(2) EleCwrical Ihirnace
(B) Physical
(C) Mechanical (Curves)
(D) History
(a) Crucible
(b) Elect:i.cal Kethod
(E) Bibliography. 20*76*7
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I. OBJECT.
The object of this thosis la to obtaii^ several sa^plos of special L.cals
put on the market by the beat finuB in the country and to make a coaiplate
chemical, physical Eind mechanical aaalyees of each; and to thoroughly discuss
each head.
II. llethod.
(A)
Chenical Analysis of Special Steels.
(a) The samples of steel &Te usually too hard to be drilled so the sample is broken iq) in a steel mortar to the size of small rice grains, and thoroughly mixed before the sample is taken for analysis.
(b) Determination of Sulphur, Silicon, Tungsten, Maiiganese, Chromium, Phosphorus and Carbon.
Weigh 5'0 grams of the sample into a 500 cc. evolution flask, so arrangeci that the gases evolved on tlw addition of 30 cc. hox ^ater and 50 cc. concen- trated hydrochloric acid, shall be absorbed in an ammoniac al cadmium chloride solution contained in an absorption flask.
The solution is mads as rapidly as possible by the addition of heat. When the steel Ixae dissolved the solution is boiled for a minute or two so that stric i nay expel alx the hydrogen sulphide. The sulphur is th^n determined by tixid- tion v/ith iodine solution in the usual manner.
Tlie solution in the evolution flaJk is transferred to a 5 ^' evaporating dish. Ten cubic centimeters of concentrated nitric acid are added and the solu- tion evapoiated to dryness on the hot plate; taken up -iirith 15 cc. concentra+.«d HCl and again evaporated to dryness, u^en up \?ith 20 cc. concentratci HCl, di'^ lutr'd to about 100 cc. vith distilled water, boiled and filtered. All the Bil'":a ard tungatin acid will be on the filler paper, after washing thoroughly with : 5'/« nitric acid solution the residue is ignited in a weigh-id platinum crucibi'^ ds
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YIO'T * SiOo a:id ^yeighed. A few drops of Ir.droiluoric acid ai'e now adaf rnd the criicibla is heated slowly uiiuil content? is dry, then to a bright r?-' for minutes to volatilize Si02. The leas is Si02 and is calculated to S: : th& residue in the crucible is tungstic acid v/hich is calculated to tungsten. Th:,- residue generEilly contains a trace of iron \Aich can easily be determined by fusing tha residue, after the T/eight loas been taken, v/ith sodium carbonate, a2id fitting off the oxide of iron after solution in hot water.
The filtrate froci the tungstic acid and silica is placed in an evaporat- ing dish and again evaporated to small builk. Fifty cc. of concentrated ffiiOj are added iuid the solution boiled until no mere fumes coae off, shoeing ■tiiat eUl hydrochloric acid has been expelled. Enough concentrated HIJO- is now added to bring the volume up to 200 cc. and the solution again heated. TTnen it hae reached the boiling point, 10 grains of KCIOt are added and the solution evaporated dov,-i to 75 cc. in order to remove all chlorine. The manganese vrill no\7 be completely precipitated as oangaiiese dioxide and the chromiiiin \Till be converted to cliroiaic acid. The solution is filtered on asbestos, vhile hot and vashed a fe^v times -..ith freshly boiled concentrated nitric acid. Tne oanganese is then dissolved ',7ith hot HCl and a small ODOuiit of potassium nitrate. It is brought to a boil to drive off chlorine and the traces of iron are precipr.tati-:". by aiffi-Dnia and aLinoaium acetate; the basic precipitate is dissolved av.d rupio- cipitatdd to free it from -craces of manganese. In the filtrate the manganese is precipitated by adding one gram of sodimn phospliate then -ma king the solution sZightly alkaline. The solution is boiled and stirred until the precipitate as^ur,es itb characteristic appearsmce, then filtered, washed, igr.itod and ^-'.ghed as lJrS'2^ i. In the filtrate from the iirst precipitation of tiie ran^oiiese, the chri^'.aiuia is determined by titration "7ith ferrous su1.p;-=ite aiid poiassiua per- m£-nganat6 according to -_ie following reactions ; 2Cr20-T ♦ 6FeO v 3^6203 * ^^2^
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For the determination of pjiosphorus 5 grams are weighed into a";iporcelain dish and 60 cc . of dilute nitris acid added. If more thaji 1% of chromium is present some HCl will also have to be used to aid in dissolving. Solution must be conqjlete before allowing the evaporating to go too far, or it vdll be hard to dissolve all the steel. The residue is baked as used in phosphorus determinations, 20 cc. HCl added and the solution again taken to dryness, takei:i up in 20 cc. hydrochloric acid, again diluted and filtered to free from silicon Euttl tungsten.
To the HCl solution, J>1} cc. ammonia are added, then sufficient HJJO-i to redissolve the f«rric hjrdroxide. Due hiuidred cc. of molybdate solution are added and the flask shaken for a fev' minutes. After standing for one hour the yellow precipitate is filtered through a weighed Gooch crvicible washed with 1'/. nitric acid, dried for an hour at 80° and weighed as acmonium phosphomolybdate which contains l.b5''. phosphorus.
For carbin, 1.5 grams are dissolved in 100 cc. of a 331' copper and potu.::- sium chloride solution. After standing half an hour 5 cc. hydrochlorine acid ese added to hasten solution. When all the precipitated copper has been re- dissolved, the solution is filtered through ignited asbestos in a platinum filter tube, uriihg suction to hasten filtration. The carbon is waehed a fev tirr.dS with hot water, then dried, ignited in a combustion tube ahd the f.v:' ac. CO-, abborbed in 'Weighed KOH bulbs.
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(8) Determination of llickel. Two graos-^f tiie sampla are dissolved in 55 cc. concentrated HCl and 1 cc. HNO, and evaporated to 10 cc. Transfer to a 250 cc. separating funnel and use as little warm hydrochloric acid (2:1) as possible in rinsing the caterial into the funnel. Cool and add 40 cc. of pure ether which has been previously agitated with 5 cc. of HCl. Shake vigorously, cooling from tiiao to time. Allow to stand and run off the aqueous solution, ^ash the ether by shaking with t>70 portions of 5 cc. each of hydrochloric acid (sp.gr. 1.15) Boil out the ether, precipi- tate the iron with aiamonia, adding a little bromine water to precipitate the nan- ganese. Evaporate the excess of aomonia obtaining about 100 cc. of oolirtion containing 1 cc. ammonia. Precipxtate the nickel by hydrogensulphide, filter, wash \jith hydrogen sulphide water, and '-yeigh as Ni2S contedning 0.7855 nickel.
/kn49)' Vanadium. Vamadium is occasionally found in pig iron, and nay be determined with great accuracy by the foUorfiiig roethod. Tread 5 graunes of the drillings -jith 50 cc. nitric acid (1.2 ap.gr.) in a No. 4 beaker. ^Ihen all action has ceased, transfer the liquid to a porcelain dish, evaporate to dryness, and hant at a gradually increasing temperature over a Bunsen burner until the nitrates are nearly all decomposed and the mass separates easily from the bottom and sides of the dish. Transfer the cooled mass to a porcelain or agate mortar, and grind it thoroughly vith 30 gramaes of dry sodium carbonate and 5 gramues of sodium nitrate. Tranaf«r to a large platinum crucible, and fuse rmll for about an hour at a high temperature. Run the fused msws well up on the sides of the crucible, allov it to cool, dissolve in hot water, smd filter. Dilute x .c fil- trate to about 600 cc, and add ni+ric acid carefully to get rid of th? cru. i^onir acid. Boil off the latter, but be careful to keep the solution always sliglvbiv alkaline. Filter, Buid to the filtrate add a few drops of nitric acid to mat--^ i'
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faintly acid, when the appeararce cf a ye'lcjish coloration is an indica'' on of tlie presence of vanadic acid. Add to the solution a fe'Ti cc. of nercurous nitrate, and then an excess of nercuric oxide in :7ater, to render the solution neuti^al and insure the complete precipitation of all the mercurous canadate. 'Jith the mercurous vanadate are precipitated also all the phosphoric, chromic, turgstic, and molybdate acids as oercurouB salts. Heat to boiling, filter and VTash the prscipi^'^ate. Dry it, separate "che paper, burn it in a platinum crucible, add the piv-cipitate, heat carefully xo expel the uercury, anc' finally heat to full redness. Fuse tlie broi/nisn-red mass remaining in tlie crucible vriXh a little sodiiiia ca-'bonate raid a pinch of eoditun nitrate, dissolve the cooled mass i in vuter, p-id filter into a 3-9II beai:ar. Add to the solirtion pure anmonium chloride in e::c933 (a.bout 3«5 gianmes to each 10 cc. of solution), and al!lo'j it to st&Jid for soiiatias, stirring occasionally. Ammoaiuin vanadate, innc!I.-'.b1e in a saturated solution of annsoniur: chloride, separates ou" aa a ■•hit? pc./der- It is necessary to keep the solution decidadly alkaline, ?nd a drop or ti/o of ammonium ijust be added from tine tO tiiua. The appearaiice of th? faintest yello'-lsh tint to th:- soluxion is ^3vidence that it lias b'^come slightly acid, and this must be correcxed or the result vill be too lov. Filter on a small ashless filter, wash first "ith a saturated solution of amnonium chloride con- tai.ning a drop or t^70 of eiamonj-a, and 'chen with alcohol. BiY, ignite, •.loiF-.ten with a drop or t\ro of nitric acid, ignite, and veigh as vaimdic acid, \7hich con tains 56.22 porcent of vaiiadiv'n.
(10) Detenuination of iIolybdent,im. In irons aiic steels oontai^ujif: from 1 to 10 percent of molybdemar i roat 1 granre of the drillings in a bea'cer 'vith from 50 cc. to 100 cc. nitric acid (1.2 sr-gr.) and lieat on hot plate r.-:tdl all action has ceased, evaporate to dryness in aii air-bath, take up with hydrochloric acid and heat until all fTr'-.r,^
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oxide is disscJ.Vod evaporate to dryness, take up '.vith dil\da hycrochlTric ac^d and filter froai sir.:-c?. ; treat this residue \7ith sulphuric and hydrofj v.orio r/.-.i/it. weighing if silicon is to be determined, and after weighing the second Hclls tv.'-.c the residue -.rith sodium carboaiate and a littla sodium nitra,te, dis?olve i';:.. "K.io::. filter, aiad add filtrate to the ijuia solution. Fu3duce xho ferric ch].orJ.as ryith au-monium bisulphite as in the determination pi phOLphorus and aftir ha/ing '■^.riv;" off the sulphurous acid, pass hydrogen nuJphide gas into the solution fur a"! hu-- keeping ix at about 80° Co At the eiic of thir; tiae, liiakd the eolation z::ir-y/n\a.- cal, then acidulate '..'ith hydrochloric aoid and pass hydrogen sulphide agaJ.n for =-. fev; Liinutos; staiid the taea}:ar tdidc- and alio-,; the precipitate to settle until tho supernatant liquid in clear, filter on paper, and rrash -.vith liydrcgcn su]ph.i-e water. Treat the filtrate again in the scmo -.ray, and if aiiy precipitate fo-^s, filter on another paper, Vash the precipitates fron the pcpera into a fce:.I:.or v/ith hot anooniuu sulphide r5olution, turn the pd.pers in a porcelain c:-ucible, cover the residue in the crucible '.dth flo-./ors of auZphiu- am heat gently until the sulphur is nelted, thr-.n add a little sodium carbonate, covar the crucible vith a lid and heat ujitil liquid; cool, dissolve in hot \-:'ater, filter, and add the filtra'-e to xhe laaiii solution- "arm the culphide solution for an hour or 80 and filter, --a^jhiiig 'jith aiasioniuu sulphide v/ater from any sulphides that he// be insoluble in the aiiiaonium sulphide, but ■..•hich should be soluble in hydrochlor- ic acid, ujilssB soma copper has dissolved in tlie previous treatment; otherjise the treatment \'ith aiauoni":a sulphide has been insufficient.
Heat the filtrate, v/hich shovad be yellou in color, almost to boiliiig, and acidulate carefiJ.ly mth hydrochloric acid; ^hen the acid is in excess, ail tlie molybden-jm suJ.hide v;ill be procipitatod, but hydrogen sulphide may be passed for a shorx time if necesscury. Keat zhe solution gently until all smell of hy drogen suljhide is driven off, and filter on a weighed Gooch crucible, washing
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with hot 'Jatei-. Dry at 100'^ or 120° C. and ignite in a stroazi of hycl;'og--.-'._ until \;eight is constELiit^ by placing "che bov,'l of a clay toiiacco-pipe in t\v- crucible and passing the hydrogen into the stem. The hydrogen ras must h^vs replaced the air in the pipe and crucible before the heat is applied. lic-^.t to dull redness for one hour, remove the heat, and alZo\7 to cool vc.th th^ hydrogen passing. "'eigh, and repeat the ignition J the second veight 'ii'..'}'.'. rarely differ nucn from the f:U-3t. The precipitate is molybdonura difur:P';.;d';. ,. v;hich contaiii^ jO percent of mulybder/jia.
II 3, (a) PHTSICAL TESTS.
An attempt '^as ciade to deteraine some of the ph^sicaJ. propertios ox the Steele. One of tlis laoet noticeable properties in a qualitative way '-/as the slow ratd of corrosion of the saniple by HCl, HSIOt and aqua regia. The most importaiit physical cl:aracteristic being the tensile strength. 7a endeavored to obtain ii«i:cii.-:r:i3ii<ijcx this quality with the testing machine of the kechanical Laboratory. Tv/o metliods, tliat of p^olling and of bending the test bar wore usic".
For the first method the Oisen tension aachine was onployed, te^t beirg carried out as follows :-
Test piece, square in section, va.3 fitted into tho ja\7s of tho uiarhins which was then operated until the wedges clamped the piece. A slov £,yped was th-^n used izi separating the moving heads cai'rying the jawc, the scaie at the same time being kept balaiiced until the piece broke when the breaking atroes TTaa read directly from scale beaia. This stress divided by original araa ol piece gives tensile strength at fracture. Thp reduction of area is deterr^ine 1 by measuring the reduced area at tho point of fracture and e .ongat: on by mea.;."-- ing tlie .'.ncrsEiont of length of xjie bar bet^7v>en tvo iiailco originally 8" apar': c... opposite sides of the point of fracture.
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Til© saae maclixiie v/as used for the tension tect by lianding but a diifsrent
method eciployed. -v/o knife edfjes were laid on the bottom plate .^f the Ea>-:h.inQ
8" apart and the test piece laid accoss. A knife edge fastened to the movin<T
plate, was brought down to touch the piece in the centre, direction of edge be.' iig
parallel to Jat of the other two ai:d perpendicular to axis of piece. The
machine '.Tas now run at slov/ speed deflectiiig the piece until fracture occrrred.
According to the tlieory of uo;:ientc fracture ^'ill occur in a speciment under
these conditions when tho tension in the outer fibre under the load equalc th-
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inertia, e the distance from centre to outer fibre the equation holds
A X s 1/4 PI. v/here T is the ultiaate tensile e strength in ;;7o" Hence T - l/4 PI e.
II C. Lip:CHAI''IICAL ffiSTiJ.
The mdthod adopted for mechanical test was a practical ahop test consisting of aal:iiig tools of the steels, tempering then according to rakers instructions aixi running cuts with the tools on cast iron and steel pioces in a lathe under standard conditions to detex'mine life of each tool under cut. It was mcer.ssury of course in order to interpret the results that the sliape, cutting argles .;.-i heat treatment of each tool should be identical ajid that the feed, depth of cut. and cutting speed should also bo the sane or if not bo that some methci bo available of reducing these eloiuonts if nariabl© to expression in terms of standard conditions. As our tost pieces \yere not large enough to allov/ as to satisfy theoe last conditions we Y/ere forced to use formulae give^ V./ Iv'r, Taylor of inc American Liechanical Society on the effect of the variaMe, c tti"; speed, in o.'der to compare otjr results.
The tools Y;ere forged into small tools of the shape and dinenr-ions gr/v o".
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1; -' INSTIXtriE OP lEOHMOIfOCOr
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in fig. 2 aiid v/.^:> in use wers fitted into p tool holder aa.de of tool steel in the shape am dJ„K'ntior.t; of fig. 3. The aiigles v;hen the tool Y/as cuttijig were then as icIIov/j: ref. fig. 1.
AngJe above horizontal thru cinter of tool piece at which tool point touches work 10° (about)
Angle bdtJeen horizontal and portion of tool in holder 24"
Angle of cl.'araoce flc^il: vrith tool axis 40°
A:igle of top of cutting edge v/ioh tool ax.ie 30°
Clearance argle between clearanco flank and work 1d° - Back slope 4C Side slope lo© , : ■
The lip ang^e T7as 70*^ ^fhich is about right for C. I and slightly too ■ blunt for icsdi-ja stasl.
The heat treatment vas tliat kno-.7n as self ha^'dening arid consisted in heating -^.he tools to a bright yellow (1790" F.) and cooD.ing theo in oil or air, fish oil being used in our case. Each tool was then ground to the above smgle in a Gisholt Automatic Grinder r/hich left the tool in the fona of a "diamond nose" yflth a tcp angle of 74°; the tip of the nose was then rounded with 1/16" radius giv; og a ro.vT.d n:se of the desired form. In grinding we at first UEod water cooling but it seeiiod to vc±e the tools brittle on the edge 2nd irregular in their working, probably due to the harden.ing effect of sudden cooling as lii. th-^ stool becazae nonentarily heated and svddcnly cooled. In our later tests then the grinding vras done dry and just before f jjiishing each tool was held quiet against the wneel long enough to heat its edg'is to bright yellow vrtien It Tsao reno/ad and allo%7ed zo "air liai-den ' by coolir-jg in the air.
The xest pieces ';7Gre a 3 1/2" diam. cast iron cylinder 28" in length and t 2 1/2" Sueel shafo Ic" in length. The t-jialysis of tlia cylinder was:-
t:-
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|
Combined c |
:arbon |
.5+ |
|
Staphitic |
carbon |
3.17 |
|
Silicon |
2.02 |
|
|
Sulphur |
.07 |
|
|
Phosphorus |
i |
.+5 |
The laetal was treated in the ladle beforo cJaating \ri.th ferromanganese vhich explains the lo-ir S but ub the charge was chiefly old iron etc., the casting was nevertheless a very hard one. '^e started a roughing cut on the scale but it was so uneven that no satisfactory results could be obtained so turned this off before continuing our tects.
As the piece was not a large one it was necessary to adopt a feed, cut and speed such that the tools would wear out rapidly in order that all our testa could be made on work of the same diameter and at the saia© cutting speed.
On the preliminary test with cut of l/S" fised 1/36" and speed 54'/min (gauged
Warner with a ' - cut meter) the tool lasted 40 sec. only on C.I. so we changed the
cut to 1/16" with 1/36" Hxfck feed and 54'/°^"- ^^ ^^*«^ *° l/32" »ith 1/18"
feed and 547nin. for C.I. and 1/16" cut with 1/18" feed and l60'/min. for steel
which gave a life of about 2-15 min. on C.I. and 10 - 60 sec. on steel.
The tools were nui under these conditions in & ilarshall and Huschart I8"
Pat. Head Lathe driven by a Northern Variable speed. 4 pole, 110 v. 20 a.mp. 2.5
H.P. motor running at 500 - 1000 r.p.m. In order to oeaffure the power used a
0-50 Weston amneter was connected in series with the armature and a 0 - 150
Weston voltmeter in parallel the power output in watts being:- if R » armature
resistance. P v i3i - PJ2 * EI (1-.52I) R being obtained by passing a curre-^
when the armature was stationary aa
2 volts f 3.85 amperes » .52 ohms. The quantities roted xrore
(a) Power Input at different portions of cut
(b) Feed, Cat, cont+ant
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(c) Diameter of iSbfk and cutting speed.
(d) Condition of tool to detertiine life.
The tools, unless they broke iEsnediately on touching the work, generally ^^^^ pretty well with low power input to the lathe for eome time. Then as the edge became dulled the power input gradually increased, work be- coiaing slightly rougher until suddenly the edge of the tool ^ould soften, power input increases very much and the work ajtid tool push slightly apart the dia:aeter of the work increased. This phenomena generally took about 4-10 seconds ?r.d on stopping the t--ork the tool vrould be found to have lost its edge completely the appearance being as if ii^were fused at the cutting point by the fiiction. This point of cooplete ruination of the tool was judged the end of its life.
in. B. PHYSICAL TESTS.
Tlie data obtained in the physicaJL tests was very meagre. In the test of tensile strength by direct pulling the test jaws of the machine were broken on our tliird speciment and ve gave up this method of attack as too expensive and tried instead the method of breaking th© piece by flexxire. The first piece tested in this way scattered all over the laboratory on fracture ar.d gave em indicated tensile strength of 229,000 j^/T" wliich showed that this method did not give reliable results. Hence we did not make any more tests by tills method. The data obtained on the first two specimens is given on p. Ho.iuitther data was obtained.
in. C. lasCHANICAL TESTS.
The data observed, as noted in II C, were feed, depth of cut, speed, power input to lathe, and life as measured from start of cut to miming poin* of to ".. In cutting the C I piece we could not get all our cuts on one diaoete" c.r vorV: with the result that t\TO cutting speeds were obtained 5* 7 oi'i* ^^'^ ^X /Tjin. ard the only way to reduce the cuts to standard was to correct one {^X' f'o'n.) to life when cutting at $A-' /mxn. uj a formula of Mr. Taylor
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— . (,..,) T]^ aiid T„ being life ajid V-i and V^ being cutting speeds. In
several cases the tools broke almost imniediately on touching the rapidly running lyork aiid the residts in these cases were not considered worth keeping. In another case a tool gave ouch shorter life when the iron was interrupted and thon started again tlion when on a continuous run, but this rxm was not thought t7orth keeping as beiiig exceptional. The dimensions of the test pieces viare r.ot such as '.rould aUo^ more than one tost of each piece and the only duplicate ru , obtained vere those on C.I. at the two different conditions. For purposes of con;„ij.i3on the run on C.I. at l/^b" out x 1/18" feed and $1 ft. speed is re- duced to 54' spetid, l/lc" cut a:id 1/36" feed b;r Taylor's forraula for l/2" round
nose teal ^ 4-
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giving the velocity for same life at feed tvice the cut and 1/2 the feed and
then iigui'ing the life at V - 5^' by Ti (Y )
_.,- . (»-) The data obtsiined and figure:. T^ (Vi)
in this 'Jay is given on table P. and further consideration of it is reserved for part IV. As the power varied so nuch and so erratically that accurate read- ings were not possible the iapu» is not tabulated, it being noted ho'.7ever that the power input into the lathe was increased from 15 - 25f<> when the tool gave cut.
r/ A. (a) DISCUSSION A!!D CONCLUSIONS - CHEIilCAL. The cheoical constitution is of the greatest importance in all steel? sine a thie fciCtor to^et'ifar v;ith the heat treatiaont is what aries one steel different f-.-osi 3r.o-;.he:-. Tne nost iinportant constituents of ordinai'y carl on feool steel
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■'.3. are silicon, carbon, aanganese, pJiosphoroun a."d sixl.phur. In special stas" there app an othar oleiai&Jits such as Cr, Ki, '.7, Mo, .11, X'ci, Ti, H, M 6c 0.
Si ie present usually in small quantities except in special silicon steols and v;hen ^resent up to 1~4> decreaoes the solubilit-»- of C. Up to 2'/. it increases the ductility and slightly lovers the melting point and increaseo the fluidity of the molten nxeel, "lu in snail quantities (1-2'';) layers the nelting point and increauec the fluidity h'A\^ing alc^o the property of coubiuin,'; \7ith arjd aliiai v.:; t- iiig S aa Ku S. P cauoes stael to be brittle ana easily broken by shock as doos aljo S both of vhich elemants chould be as low as possible in a good steel.
Carbon is the rnqst important eleiaent in stcol becauae it givos the ciaximi-un amount of tensile strength and harciiiees vith least decroess in ductility each.Olf, increar^ing tcneile strength 800 - lOOO;'- up to nbout 1% C. Phosphorous has cji equal of feet up to about .l2'/o bux ti-B oteel is mucl-j nore brittle when hardened with P.
The hai'dness of steel also depanda to some extont on the physical conatitu^i tion of the iron. 1i«i nolten steel containing 0 - 2% C solidifies the C ap- psars to be present first aa a oolid solution of iron carbide in pure iron of a crystalline form kno'jn aa "gaama" iron. In tliis fora the steel is knoi/n as austinite. As the cteel cools the iron changes to a aecoad, "beta" condition, tho steel passiug thru the forus knocn as mnxteunite and troostite as'A fina]..''.y changes to the ordinary naguetic vai'iety or "alpha" iron, '"^ijen in this condi- tion aod before the iron carbide Ims separated from solid solution the substance is known aa osiaondit©. If osuondixe contains more than .9^ C the carbide now separates from solution in flat ccaly crystals kno\m as cementito containing i),bi<, C. and if less than .9^ is present pure "alpha" iron or ferrite separates un.51 in either case residual part containing .97'' '^ is left. The .9'/- alloy con- sinting of 12fo cementite ar.d 88"/;, ferrite now precipitates out in the crystalP.ine form known as pearlite. The svibstance during the teraxsa-js-j-trmxi-ii transition 6'-?go
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is called sorbite and the final cool steel wiii bs either ferrdt© or cementita mixed with pearlite. xhe caange from osncndite to pearli.te occurs at 9OO - 6yO° in steel with leae ohan .9'y= C and at 690° - 1140° in steel containing .9 - 2.1'.'^ C The other changes take place between these touperatures aiid the raelting point of the oteel.-
Gaiaaa and oeta Fe are non magnetic and are harder than alpha iron. In iron, free from all inyuritiee the change froa on© variety to another takes place al'.- moet inetantaniously at the critical temperature during cooling but the presence of certain constituaati seems to retard this action. Tlie hardening of ordinajry cexbon tools is based oa the retarding effect of carbon on the chamgo in Fe to ths alpha variety. If the steel be suddenly cooled when at a temperature above its critical point for pearlit* formation a large part of the steel is left as mar- tensite which is the hardest variety, scratching even austenite. Ordinsiry carbon steel, however, is left too brittle by this process aiid hence must be partially reduced to pearlite in order to cake it tough. This is accomplished by heating "i:- the steel to 200 - 300° C, when a very gradi^al change occurs yielding pearlite to some extent and rendering the steel tough. Soiae other elements, notably tungsten or molybdenum together v/ith mangaiiese or chromium so delay the change that quanching is not necessary and tiie steel is called "self or air hardening", being when cold a mixture of aartensite and austenite trtiich is tougher than or'^inar; carbon steel. The Taylor Tiiite heat treatment of cooling the steel slov/ly from a white heat in certain i^pecial steels leaves the steel in the verj-- tough auctenite condition and th» alloys present prevent tlie change to pearlite until the steel has been subsequently heatod to o^O C.
Practically all the alloy steels depend largely upon this action c' uie metals ufon the critical temperatures of iron for their properties. Herre thr y usually contain a small amount (.6 - T/L ) of C to giva the hardness aid a ratier high /o of tlie alloy metal. ,Cr (2 - 4^) lovers the critical tenperat.re for
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pearlite below ordincxy toaporc-ti'-res ajid yields a very hard tough cteej usod for projectiles, etc. Ni also lov/ers tlie critical temperature which vath 25/c is belo^r orc.inary ten; erat-jres no tliat the iron is in the beta condition c:id non magnetic, Wi steel has a iiigh elastic liniit and great resilience, being uced for tension menibers ca bridge work, etc. IJu also lowers the critical tecpera- ture but Tyhen present froa 1 - 3 '5% makes the steel very brittle. Above this point it yiolcs a steel v/hich on being quanchei from 1000° C is mostly austenit'- aiad is vory h^rd oj^d difficult to machirie but so tough that it is used for very heavy duty svch p.s r'-^ils for curves, crusher jaws, etc. Certain steels low in V. and with 1 - 5"> Si have higher magnetic periaeability and electrical resistance then pure ir^'-i a;.d are very useful in trajisfonaer construction.
Soap n.otj.1^ ars addad to counteract the effect or eliiainate absorbed gases such as H, N, 0 & CO which cause the steel to have blow holes or to be coarse ground by r3a"3:i of F-O. Si aiid Liu in amall quantities renove O2 to some extent and assist in giving a quiet pour. Al is now much used to remove O2 and give a "dead" meT-t. Va haii probably the sane action as Al but cleanses so thoroughly that the tensile strength of Va steels ie nearly double that of ordinajry steel altho the actual /, Va be alsiost zero. Tlie life under bending sti^ains is also much greater in Va steel. Ti lias been proposed to remove N but not much is kno;??- as yet of its action. Uost of ohe alloy tool steels, ho\7ever, utilize "aore l.i;n one listal aiid the resultti.t properties are extremely various. Thua tlis use of special alloys for tools steels commenced only a few years ago with the Mushet "self hardening" tools which are an alloy of 4 - 12f, 17, 2 - 4*^ Uu and 1.5 - 2.5"/'» C w th ?e. This ail'^y steel may be alloY/ed to cool iii the air from the heat nec- essary for tempering withou^c becoming soft since the change occvurs too s^ov/ly to hr.ppen ciurliij tliis cooling. Later it tras found that 1-2"^ Cr could replace
V-XX altho Cr or I'u alone wo'ild not yield a self -hardening steel, liu also oay replace ?/ 1/2 as much only being needed to produce the same effect but this meted
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-.b«^ a- -tandanfT i''^ fij&itp ^b*- ato^l fixe crock on forging and such steals a""- not 80 rsliable &s the "'. steels. The Taylor 'iWiite process of tempering special steels is distinctive in that it gives a tool which will work at much higher temperatures tlian the carbon or self-hardening steels vithout softening. This property is obtained by cooling a special alloy of iron, carbon, tungsten or nolybdenuai and chroaiua froa a heat near the settinc point either slov.'ly or rap: • ly to ordinary t e rope rt\ tu re b. The high first heat ie the distinctive point ,'f the treatment Aai does not turn tJie steel as it jould a carbon steel but renders it hard both at ordinary'- tenperatures and up to a red heat. 'lolybdeinun is not 3c suitable as tungsten in thece steels, caking thea liable to aiil more
brittle but it may be used. A etosl as lo\7 as T/. ^ and 1/2 'j. Cr cay be treated by this process but the beet tools contain about l8f. tujigsten and 55f» Cr. with Carbon .6 - »7^» while ordinary carbon tool steels usually contain about 1% C .2'/. ii'u and .2';. Si, The > of ttsigsten in all the steels tested was sufficient v/ith proper '^ Cr. to rondor the^a self hardeniiig and suitable to the Taylor "iliite process. The high '^. Liu in xhe Internatioi;al steel ^70uld tend to aake it diffi- cult to forge and in fact it did develop sous fire'.forks. The Cr in the Vulcan is too lo'.,- to make as good self 'oardening tool or one vith lower cesrbon .6 - .TI' all of tlaese steels would probably be less brittle aiiy very nearly as hard. The very high '1^ Cr. a::d ^< iui zh& Bethlehea stesl probably re.idaro it a little Jiaro .r aiid nore brictlo than it should be»
16.
T: (a) Ilethod of Ilanufactura. (b) (1) Crucible Stsel.
Cast or crucible stasl 'Jac first p; oJucad upon ;■. v/orlciiig scale and iiitro- duced into Sheffield by HiJiitsiaan in 1740, when he succeeded in effecting the entire fusion of the uetal placed in crucibles standing upon the bars of an air furnace './hich was heated by a coke fire surrouiiding the crucible and final, y he cast or poiireJ the moulten jteel into cast iron movJLds for the production of homogeneous ingots. The practice as then introduced is still pursued prac- tically without modification in Sheffield and other crucible steel producing works on a large scale, for the i^^anufacturs of special steels.
Cast, crucible, or homogeneous steel, as the same product is variously called, is hence largely produced by the melting of blister steel in crucibles or pots J \/hilst har iron, carbon, Eanganese ores, or Spiegelaisen are one or more of them frequently added to the charge of blister steel, accoi-ding to the temper and quality of metal to be obtaiiied in the cast ingot. But cast crucibx-; steel is also very largely produced by the fusion in crucibles of bar iron or puddled BZQsl along vn-th carbon black oxide of manganese, or spiegeleisen in small proportions.
'^h® steel melting house or "fiirioace" as the part of tho vz-orks devoted to the melting and casting if steel is called, is soaevhat variously arra' ged ac- cording to the class and ;/eight of ■'vork intended to be carried on therein; but as arranged for casting zhe usual run of small iiigots required for the very ex- tensive light trade of S'lef field, the furnace or melting house consists of various numbers of "melting holes," or "fires," arranged along 03 both sider of the melting house. The construction of the melting holes is the sane, e:-'o ot as to size, for both the light and heavy trades, but the general arra-'igomsn "s 0' the melti-ig department are Bome\7hat modified. In the itdddle of the floor of the melting house are the "teeming holes" or small pits of about 3 feet in length
. 1 - n. ,'•
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17^ and 2 feat in width, \/ith a depth varying vrith thexkKigk±k le;:gth of th? ngotc, to be cast. The teeuiiig holes are covered over v;.ith iron plates placed l-i^vol ■with the general floor except during the period of cac-ting or teenuiig, jr the preparation for the saas. The bottom of the pits are prepared T.dth a layer of small coke, upon which the several moulds stand for the reception of the metal froa tine crucibles.
The geltin;- holes or fires form a series of rectangular chambers arraij^-Dt" along the sides of the building and v/hich measure about three feet from tne center of one hole to the center of the next, a single brick rjall separating the holes from each other; but each hole is lined v;ith a refractory lining of some 6 inches in thickness, fonneu of fire brick tiles or of ganister, so that the melting hole vhen finished ready for the reception of the crucibles, ."is a^j oval chamber measuring about 26 inches in its major diameter by 19 ir.ches in its minor diameter, suid about 5 feet in depth from the level of the floor to the top of the fire bars. Vfhen ganister, as is usual, forms ths lining material, it is rami-ied in posi.,ion by first placing upon the grate bars a vrooden model of the internal form of ths fire, and upon the top of which the workman stands aaid rams in, with a light iron rammer, the moistened ganister placed around the model, thus leaving, on the VTithdraual of the modal, a cavity of the djmensi'/.is above mentioned and capable of holding tivo pots or cruciblo^s. Tlie top; arcu.,, the mouth of th© fire is formed by an iron plate placed but very little above the level oi ihe floor. Th© grate bars are carried upon bearers, built in the masonry, isliile beneath the grate bars is the ash pit, the bars and the ash pit being readily accessible from an underground cellar or vault, which runs pare"! lei with and in front of the firea, thus giving access to tiie bottoms of the ninning pots aiad the like during the working of the fires, since by withdra-Jing a fire bar or two, enough fuel falls into the ash pit to enable the workman to examine
r^.l,t• •
18.
auid, maybe, to stop the hole in the running pot, etc. The cover of th; fire
ie formed by a eqnare fire brick, tilo, quari'y or slab, about 3 inches in t! ick-
iron nes6, held in a v/rought frane provided with a projecting bar or handle for movi-ig
the cover from over the hole. Each fire is provided with its own flue in the
fora of a bqelLI rectangular passage of considerably less sectional area than tlu-
furnace itself; this flue leads into a flat vertical chiianej'' or stack of about
40 ft. in height which is continued do'.Tiwards belovr the flue to the ach pit
into which it opens and by the insertion of a brick into this opening and also
into the flue, the draft of each fire can be regulated so an to either urge or
to keep back the fires as may be necessary when oaking large ingots, in order
that all the metal may be melted and in proper condition for teeming at the sane
tine. Five or six of the vertical or chimney flues are carried up together, forri
ing one block or stack for as many holes as there are flues, the adjoining batca
of holes to the sane number having their flues carried up together in the saniQ
or manner. Each fire hole a£ thus described holds tv70 pots or crucibles, each
supported upon its oi;m stool or staiid of about 4 inches in thickness, to which
height the crucible is raised above the bars.
Around the sides of the malting house are fixed shelves upon v;hich the fresh or green crtzciblas are placed for diT^ing before use; while outside the welLIs of the melting house it is uauaJ. to place the shade in which the clay for the manufacture of the crucibles or pots is stored for di^ying and tempering by the heat of the \7all8 of the melting house.
The crucibles employed in steel laelting are usually from 16 - 18 inches high and 6 or 7 inches in diameter at tlie mouth but special crucibles of Ipr^^r eizee are no\7 f^bqvently used. These pets are mads of mixt-jres of fire clv.:-o U.j:a the coal maas'orcrs, with pot sheds, coke dust, graphite, etC; and ore c:<.-ered by ^.idr eiuring the fusion of the charge of metal, the lids being al-o ma-J/^ -rom fire cl-ys,
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but of an inferior class to those eiaployed for the crucit'es. The cruclc!j.es are each annealed before used; tliey are usi^ally placed in the annea.iing over.s in the afternoon or evening and left there uiitil the following morning, when they are at a black red h6at and are removed by tongs for conveyaiice to the melting holes into which each is inserted and placed upon its own stand in the fire.
The pots having been thus placed in the melting holes, into vhich a sxmi?.'. quantity of live coals lias been previously introduced, the fires are no'j fiLlsd up with coke to the level of the top of the crucibles and the whole is pJlowed tu burn up slowly, co that in from twenty to thirty ninutes, the potc are at a red heat and charging of the metal into them comes.
The charge of blister steel, which has been previoucly assorted and broken up into nmall pieces, and weighed up into the crucible charges of from 40 to 60 lbs. each, is no\/ introduced into the cruciblec through a '.rrought iron funnol sliaped charger, placed by one man over the mouth, whilst aiiother empties the charge of metal from the pans into the mouth of the cliarger, a little black oxic".. of manganese being also Bonetimes added along with the charge. The cover of each crucible is noa replaced and the fires are made up with hard coke to s2ight ly above the level of the flue when the cover is placed over the melting h::-, and in from 45 to ^S minutes this first fire -./ill have burnt off. The workman introduces his bar and potters down the fuel hanging about the bottom and sidec of the pots, 30 that in the next firing the coke gets down to the bottom of the pots, for othsrwiae, whilst the top of the pot would be red hot, the lower end woald be con5)aratively cold, and the meteLL probably set in the cruciblo owing to the fire drawing in cold ait at the bars, whiihtwould not meet with ccmbjs- tibie coke for some disteuice i?> the pots and hence the surface of the fire &r i top of the cxoicible vould be at the highest temperature. Although the bottom might be cold. VJhen the second fire has burnt off, the charges will have bcjun
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20. to malt, aiii the lids of the crucibir- are then tr.rned off, v,'h3n "^.he ne?+er goes round vrith an iron bar aiid introduces it ii'ito each pet, by which he c.:'. feci whether the mrtaJ. is ail fused, or \7hether tmy liraips of uiir'^elted uet?.! ctiJi re- mains, and he gives instructions accoi"dlngly as to the cJiount of fuel to be added to each hole in ^his third and last firing, so that the whole n'jLiber of crucil-'.;s may be reedy at the Scoae tiae. YTnen the third fire has burnt off, the charge? ill the sevo.ol pots ou,^ht to ba in a complete state of fusion and ready for tecaiiig. The neltinj- thus oi-cv.pies froxa 4 to 5 hours according to tho ten-pr/r etc., of tJie stscl.
The crucibles T/ith its coiitents of fluid metal is withdravrn from the fire with tongs and landed on the floor by the "p'ollsi- out." Before teeming the met-^.' in the crucible is first s\f:mi:-36. or cl'sared of the sla^ floating on its surface, whereupon the clean surface of the raetal presents itself and the teemer judges of the best heat at r;hich to ca^t the motal, allcTring it to stand in the crucih,'.-o for a minute or tvo, if he judges it to be too hot.
ATtor teezung is completed, the pots, if in good condition, are again received in the barro'.Ts aivd returned to th-e pullers out at tlie fires, wlio, after detaching adhering slag and clxukar from the bottom of the pots, replaces them in the fires for the reception of a second chai*ge.
IV. (A) b-2. TliE HE?i>.ULT FUiaiACi: A:?D PIOCESSiJS.
LL-. r-.ul He---oult, the French inventor of the process for extracting aluminlj frf.m i-cj ufiC 33 by electrolysis, 'jas born in Thury Harcoui't, NormEuidy, in I863 a-." '7-'d ec.vCr.tid local.ly as a mining engineer. He was only 23 years of age i^her he pa.ton-'. ju his procei^s for al'jminium extraction and in I88'' ho "sas r; . L.". rg i:.j xechni'ci ;^.neger of the first erected aluaniiiium -Torks in Europe at 1''. : i-.v.v.in. As staced abov© II. Heroult turned hf.s attention in 18>9 to the production cf ferro ch 'ome ferrO silicon aiid ferro tungsten in a ^aciified fori c; the alectrai-
furnace used for aluninjua production ai-;d i-^ 'vas the success of xhebo ■ jnpts that suggested to him the ut,e of elect:'rxQ hori'siit- in tha iron and yteel :'n:' Tt-/, Two distinct furnaces and two distinct methods of 'jorJr hu^c resulted i.-om theso experiments. The one a tilting electric crucible furnace for steel icanuft.c- ture, the other a laodified form of the blast furnace, Trith electric heating for pig iron naiiufacttire. These will now be described in the order naned.
(l) The Keroult electrically heated crucible furnace.
Tliis furnace consists of a low shallow iron tank thickly lined ^rith a refractory material which will stand the high temperature attained within the furnace without undue softening or corrosion by the slag. This lining con- sists of doloaite brick, with magnesite brick aroimd the openings. The hearth is formed of crushed dolcjlte, rammad on top of the dolomite brick lining of the bottom of the funiace. The funaace is mounted on two curved and cogged bars, which permit of its baing tipped side'A'ays and held at aiiy desired anglo for discharging pva-poses. At the opposite side from the discharge lip there is an i:ilet for the air blast, and also an insulaced supporting frane work for caxryiiig the tyo masbive solid carbons, 1.7 metres in length, and 3^0 mm. square, which convey the electric current. These can be moved either in a vertical or horizontal direction by use of gearing. Openings ore provided :"n the top cf tha furnace cover for charging, for inserting the two elect: 'itz. and al?o for the escape of xhe gases pi-x>duced on heatiiig the charge. This - atter can be effectod either by arc or resistance heating. In the fonuar csfa, the electrodes are allowed to touch the surface of the blag or metal, an.'l a.i-j thon ra:'.j3d upv&rds to the limi-u of distaiice which the axe wir.l strikD, with the ouri-ent and the voltage at coiLTand. Two arcs will ba fonaerl vr-'V^- "hes;? conditior;^ one as the current enttrs the charge o-f olag or isetdl, a'ld ore
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as it leaves the same vmile in between thsEe tvo points the cm-ront ^i."'. traverse the sla^, a'i i produce resistance boating.
Y^en r=si'jtance heating only is desired the twc electrodes are lowered until they dip jenc-ath ■c>ie surface of the charge and the current in this case pasnes froa one to the other entii'ely by the materials forming tlie same.
The nethod of producing steel in this furnace is aa follow i:- A charge of steel scrap, pi^ iron, iron ore and line - in the requisite proportions aid quantities - ±5 placed in tlie furnace, ejid this is raised to the melting point by combined arc aiid reeietance heating. The slag formed by the lime and sili- cates of the ore now rise and float on the surface of the molten laetal and the further heating of the charge occurs by allowing the electrodes to aip just beneath the slag, but not into the metal beneath it. An air blast is new allowed to enter the furnace at some suitable point, and under these conditions the impurities of the iron and steel scrap become oxidized and enter the slag. By pouring off tliis slag, therefore, and by renewing the materials which form it once or twice, a vary pure product can be obtained. The process is in reality a washing out process, in wliich the slag acts as solvont. The fact that all the heating with this type of furnace occurs without any actnaJt con- tact between the carbon electrodes and the metal also coiiduces to purity of the products, siive no silicon or carbon can enter into tlie iron or st^-al from the elflotrodes. '^.Tlien the iron in the crucible has been raised to the requisite de- gr^a o-f purity by this washing out process, a calculatadgajaount of an iron alloy high in csrton is added, and the resultant steel • of known carbon contents - is tipped irto "utie casting ladle.
A similar method is followed when making ferro alloys, the requisite weight of alloy, high in the percentage of the mstaJ. or element desired, being added to the contents of the crucible just before tipping. The crucible fumar.o
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usually employed for ch.Ls pz-ocess produce "^hrae tons of finished stee.. ar cliarr: and tvro charges per day of 20 lioura, the cio-rent required being 4000 ai^rarcs at 120 volte pressui'o, or 480 K."'. Tlie following t^b-t shows the average com- poaition of this steel:-
Iron over 99'/, Silicon .03^.
Carbon .6% Phosphorous .0057,
Uanganese .15% Sulphur .007'f.
One of the test runs madti by the Caimdian Cotsoission of experts at LaPraz with the Heroult steel fiu-nace gave the following results :-
The charge v.-as uiade of 3, 307;." of iron scr ap, 330?," of iron ore, and 246;-;/ of lime, being purposely made iiaall to reduce the time requisite for finish- ing the charge. when the charge had arrived at a tranquil nolten state the slag \7as poured off and ovary care yas taken to remove all of this from the Eietal left in the crucible. A neTT olag was no'J fcnaad by adding the following naterials, lime 55;-;, sand 15 l/2;;' and fluor apar 15 l/2;;. -"/lien tliis slag had been aelted it was likevrise poured off and a uey cliarge of slag forming material similar in weight and constitution was placed in the furnace. This formed the finished slag, and after its removal 1 l/2j^-' of ferro manganese v^as added to the molten mass said the crucible vms 'cipped for discharge. The total time required for fu;-mishixig the charge was 4 1/2 hours and 2,829;,'' of steel of the follo?;ing chemical constitution were obtained:-
Ilanganese .230'/, Arsenic .09^?.
Copner trace "/l
The physical properties of th&s steel were good. The s'^.ec ':r: .^al ener;.^ required for its production was 1,410 K.-''. hours equal to ,153 E.'-' P. yea"/toi of finished s:;eel.
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VI.
ARMOTTB
iNSTia-D'i'E OF •nscHNOi.oai
At LaPraz eiglit grades of steel are made van/ing froa tool steel of excep- tional hardAass, seiiinc at fe 72 12 s per ton of 2000 j7 to tough laild steel, selling at t 24 12 a. per ton. The cost of a 2500 kg. tipping furnace with all tlie accessories is given by Heroult as h 2000 v/hile another & 1000 would be re- quired for the electrode making plant. The electrodes are laade from retort coke using tai' as a binder ,
(2) The Heroult Smelting Furnace a.id Process.
The original foru of this fiu-nace is shovm in sectional elevation in 72.-^.\i__ Tile principii of the furnace is the continuous supply of the half fused ore and fluxing naterials to a colunn of coke, oaintEiined at a red heatby Feans of ai-i s.± an electric curi*ent and resistance heating. A, in the figure, is the channel
by v/hich the ore and fluxing materials are supplied to tlie vertical reducing zone of tlie furnace, while H is the shai't by vrliich the coke is charged. The gases passing aA^ay from the hot zone pass up A and thus heat the ore and fluxes before these arrive at the vertical shaft. G, ? and B are solid carbon blocks 'Jhich function as electrodes, the current tenoinals being placed I and J. The electric cur- rent passing from B to G through the coke main- tains this at a red heat, and as the pasty inass of ore and lime passes bet\7een the carbon blocks 7 and G it is like^Tise heated by the current and rendered more fluid. The liquid chai'ge of ore and lioe in its latter descent through the hottest zone of the furnace (Z) spreads out and during its passage thrciigh the hot coke tre iron o.ide is reduced to metal3_ic iron which collects in thb hearth and is
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run off by the tapping 'hole D.
This experimental furnace heuB been sone uhat sinplified in the light of more extended experience and the smelting furnace used in the trial runs for tbi Canadian Cocainis si oners at LaPraz, consisted only of an iron box of square crosi- section, lined v/ith refractory and open at the top. The bottoc of the casing i7as provided ••Tiih a carbon plate, which acted as one electrode of the circuit, the other being a novable block o^ carbon of square cross-section, 3 ft. in length aind placed vertically in the open top of the furnace. The distance be- tween the electrodes was varied by hand regulation. The charge consijting of finely divided ore and coke, was placed in t}ie square bet'./een the tv/o electrodes and also around the upper electrode and fresh ore ■?ras added as that in tlie lo-'-^ir part of the f'rnjxe was reduced. The follot/ing are the details of the runs laals '.yith this furnace:-
3,230 k.T7. hours, equal to O.50 r..H.P. year. The total output of pig iron \7as 2l30j' a-nd the po\.'er used 'jas, therefore, 0.47 E.K.P. year per ton (2C'.iC of pig iron. At fc 2 per electrical horse -povrer year, -che cost of the ©lectrica" energy required for the snelting operation v/as therefore 18 s lOd per ton of pig iron produced.
Let us novi look ax the yields and costs of the Heroult furnace.
Yield:- (a) (Steel fron Pig Iron and scrap charged cold into crucible fur nace vith C. elect.)
Trial ;1 — 882 k.w. h<.s./iaetric ton of 2204^;^ " ,-'-2 —1000 k.\T.hrs./ short ton of 2000f/ " -y3 --1000 k.w-hrs./ short Canadian Coimiasion)
" r:4r 653 k.-Ef.hrs./ short ton ( Caiiadiaji Cjciuission)
Qvality of steel of trial f/l was not stated, in y2 a dead soft steel v&b produced in ^i^Z a Lc^^ci tocl s :oel and in jU a steel adapted for structiural purposes.
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(b) Steel Produced Trom scrap melted over oxidized ii: an opon heart., iiai-nace.
Trial 7,^1 3>^0 ':,vir.hr3 ./laetric ton of 2204 /,-. This trial was uade at tl.3 Rem- shied r/orks in Ceir-s-ny and the quality of the steel \7a3 iio^ stated.
(c) Fig Iron Production.
Trial ;-,-l - 3^080 k.v.hrt;,/fahort ton
" ;'2 - 2,3o0 k,v/,hr3./ bhort ton
" //-J " 2,3't-2 I:.\7.ii.-s./shorG ton
No. JL gsve a close grainid iirey pig
No. 2 gave a gray iron high in C w Si and No. 3 trial a sinilar iron with 3 - 4;. Mi.
Tak5.ng tlie r^ean of the above vaJ.L-.es for each product ve have the folloxvin^ figures for the Ileioult process eand furnace :-
(1) Stee]. froz. cold pig aiid scrap - '3o4 k.v/.hrs./2000;|.'
(2) Sueel I'rcn rnoulton opsn hearth steel 329 k.w./2000;:: (3} Grey pij- iron fron^ o:-a 2,o9j k.v/.hrs./ 2000 ,r-^
(4) Eerrc nicl-.^a pig from ora 2,34-2 k.u.hrs ./2OOO /f
The costa ol' the process can be averaged up in a f0>.7 figures as follows :- i..(c.) ^-.-egl frci.' scr:?.p. h 2 lo s/ton of 2000-/ e;:cli.tsive of cost oi scre.p (Electrr.c p.-;/5r at L2/i;.H.P. yscj;'.
(b) P:g iron froQ ore:- & 2/ton (ore at 5 s/ton)
The subject just discussed is just one of the raany processes now in opera- tion a-.d If conexderdd the best. Jie subject is a vei^y -.ade one and many books have been ^7rit^en upon ii5« I-,;ontion mi rht be crnde of the other important electric furnac;es. Tliey are as follo\TB:-
The Ke?.ler Furnace
The Kjellin Fuiiia^^e
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The Stassc.iO Furnace The Conley Furnace The Calbraith r-.T;mce Tlie Gin Furnace T}ie Girod Funiace The Harmet Fiirnace The Hiorth Furnace cuid The r.uthanberg Furnace Of all these tlie Heroult ia the best kno-.ni and used tlie most.
lY (3) Physical.
The physical properties of steel coneticute a fairly accurate guide to its cutting speed and these properties are best indicated by the tensile strength and percentage of stretch smd contraction of area obtained from standard tensile test bars cut fron such a position in the body of the forging as to represent its average quality and then broken in a testini^ laachine.
As the above tests depends ,_reatly on the hardeninf; ajid tempering of the steel, these xjo ii^portant factors night be taken up Iiere .
Hardening:* Carbon Steels and ordinary'' tool steels tliat are ciade up into tools or iioplauents are entirely too soft as they cocte from the forges for al- most all cutting purposes. In order to prepare them for cutting, thoy r.'ust be harden&d, and this is done by heating them to tauperatures in accordance -^ith their carbon contents, varying betv/een a dark and a bright cherry red, say, from 1350 degrees Fahr. (735 degrees cent.) up to 155O degrees Falir. (645 degrees CctJ and then by plijiiging thou Ly.'._c;:ly into vater or other s'oitable bath, cooli;ig very . rapidly to a tenperatv.re acS exceeding 392 degrees fahr. (200 ^egrees G^iit-V."' preferably to the normal cemperct-n-e of the air. This operation is called hai-d.C' ing.
Tenipprinp;;- V/lien cooled suddenly in this "..'ay, ixc^pleLsnts aiid tools laade from car- bon tool steel are too brittle for most cuoT.i.ig purpoces. This qur.lity of brittleness is removed or modified by reheating to teuptr:.. .ire rrjiging betv;een 392 degrees Talir. (200 degrees Cent.) and 6OO degrees Fatir. (315 degree?. Cent.) Tie higher the xool is raheated within those ranges of temperature c, the softer it becomes and this reheating for tlie purpose 01 partially softening and at th? same tine toughening the tool is the operation kno-vm as "tempering" the tool.'' In many cr.rses it is not practical to use a pyroaeter and the question ^.rill im- ir:.dia-i:8;y arise - Her.; caia one detemine the temperature of the steel. The foil.- -
ing ta.blo siiTfjlifies the question:-
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Color I:a3ies for High Temperatures.
Dark blood red, black red
Dark red. blood red, lo",'.- red
DcT.i'k cherry red
Kodiua cherr^'' red
Cherry, full red
^r:.£h-o cherry red, scaliiag heat 1550" "
Sa'.ai!cn, f.ee scaling heat
Light sa"'ij!jn
Yelio\7
Light yellai'
"iliite
IV C. Discussion a:-id Conclusion - i.'echaiiical. The data obtained in shop -;est for cast iron are tabulated nox only in actual life as obtained on the lathe but also are figured to life under standard condi- tions according to Taylor's formulas as noted before. Tivylor'a forraulao however V7ere obtained from runs of loi:ger d'oration (20 minutes or more) a«d do not seem to hold for our riuis. The reason probably is this!- '^e prime cause for fail- ure of a tool is the softening of tho cutting edge due to heating by friction witii the work, \7.ien the tool is rt3n:xiiig at such a speed as vdll give 20 min. life or m6re the rate of input of work imto the tool point is so slow that the tool doe" ndt at first becone heated up but only 'after the cutting edge has gradually j:—
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9900 |
ralir |
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10500 |
It |
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1175^ |
II |
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12500 |
11 |
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1375° |
II |
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1550° |
II |
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10500 |
II |
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1725° |
II |
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10250 |
II |
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1975° |
II |
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2200° |
II |
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29 = come bl'imted so that ths pressure 6n tool point has intre::.Pod does the hjat in- put greatly txcoec' the Iogs by radiation from tool. With the speeds which v.? used hoTirever the power input even isrith the tool sharp 3L.ff..o6d to heat up until the edge began to soften when it immediately gave so that our test v/aa really a ts3t more of what temperature the cutting edge would stand that of the liardnsc;' of the cutting edge and the formulae are not accurate statements of tlie conc'v- tions for such a test. The great difference betvesn the last five and first fire values in the last colunui v/hich if -the formula© held rhould be approximatel- squal for each tool sho-./ tlmt tliey do not. The probability is that the l:.f3 is proportional to tlie area of cut aiid cutting speed. TTith this understandirg the ranking for cut on cast iron, primarily a temperature test is taking -ij&th cuts ijito consideration:* "
Poldi, International, Heller, Bethlehem, Vulcan v/ith an aggregate life of 24=5. 23 9, 20.5, 10^5» and 9*2 •minutes respectively.
Vusn tiirri5r-g the steel specimen since \?e had a very aaall piece of B»tal to vor'': on it v/as necessary to cut at extremely high speed and the results r.re prob'',b.ly not ro reliable as tho&a for cast iron. The test, being so short is even core tlian tiiat on C.I. a determination of the strength of the tool at h.Tgh ternperatut-es. The ranking in this test v/as as follo'js:-
Poldi, HeiLler, Bethlehem, Internatiojial, Vulcem.
Tlie higher rate of cutting possible with tlie steal is due to the idCt that the me&al is more ductile than C.I. and so the chip flouvs out over the surface of :-he xool distributing its heat and pressure to the 'Jhole tool point instead oi to ^he cutting edge alone as does the more brittle c:3t iron.
To re^urc- these conclusions a" a measure of their value would be r:.! ir^^^ un- ties to the steels for several reaso'is. In the first p.-ace tools are not r; n ^/ such high cutting speeds as those we used, secondly the heat treattrjnt such ■:".:'. for these steels to get best tlfici-ncy 'should be the T^/lor V.liite which gives a
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tool better capable __staj-iding hitjli xeriipai'atures . The qutJ'.ity of the nu - .1 cut
especia23.y in tre case oi caot iron is liable to groat vs.riation in che di:'-- f ei ent pL:_'ts of the piece aiid the data itself is ra-^her r.vicertain as v/as shov/r. by the Tact tiia.': a nui^ber of 'che tools broke in tlio first fdv; seconds striking the ■'■/ork.
r/ (d; (a) Kintory - Crucible Hethod. It '..'ould dou'ctless have been felt by naiiy but a fevs years ago that ths.o T7as little left to be said din tha subject of cri'.cible tool stool and tlmt som- thing ahin to finality nad been arrived at in its nanufacture and genp.^al trea . ment. Protabiy such feeling va<3 justifiable v/Iien it is reueubered that tlie ma!' ing of ::teel in crucibles is by far the oldest nethod knovT.-!, dating back from tine iuj'usGi'a lal, it being indeed impossible to accurately trace ics origin and ear3i6:'t de ve leprae nt, bux it eeens cer-:ain that carbon steal v/as -ijade and used thousands of years ago for cut'ciiig tools. Proof of t]iis laay be seen by the mar\'ollouE carvings and v^orkings on the intensely hard stone "..'ork of the ancient •; for it u'OL:ld be difficult to conceive by ■■./hat raeans, other than v/ivh steel tools, Buch vork could have been executed sind it is wonderful to conteuplate that steel cutting tools should have been used so ''ong ago, whilst the principle of manufac- turing theu thr.t is, by fusion of iron and chc\:coal in crucibles - was then in a measure on the same lines as the work is done at the present tine. Archae- ologists have discovered that the Chinese raade steel in crucibles long before the Cl:-i?;tian era. "^ootz" steel fabricated in Inlia centuries ago '.7as crucible ate.-' uii vao al-.o the C( Vebrated DanascuF steel, produced at the forges of Toledo. I: IS recorded "ciiat tixis 'DaQascua szi-^l contained oe-tain percentages of tungstf nickel, Eisxiganfese, etc., soae of the very elenentt, in fact, contained in the present iaodem high speed steel, so tl-iat a latenx high speed steel may be sai" to have exi^t^i centuries ago, and all that was necessary to bring out its
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3"'-. inherent powers -.vould have been tlie heating of it in a pr. jdoxicafl ;jjcUv:i.. cc to specJc: that is, to such a high degree of tcmpc-ature as was lonp th":'~'-.v would iiipair or destroy the nature of such steel. ""?hin. taureforc, ve iooi: bac": on the period for v/hich crucible steel has been knovm in tiie world's history, some tiay not unnaturalHy thirJc tiat 'chero lias been tiue encigh to l-iavo ful?.y fathomed its mysteries leaving little more to be said on the subject. It i" then all the more rauarha'sle tliat ti discovery, i-oade but a few years b£,u:h, and . '.- which has s.ince revolr.tionized the treatment of crucible tool steel, shoxiid hi^^. reriiined so long a hidden secret.
A very inipor^^ano advance v/as aade thirty or forty years 'go, v/hen "L'ushs;, ' or se-f hai'deniag steel, '.;as introduced. This was the valuable invention of Robert !:'ushet, v,"ho, after a Ion.; series of experinants, loado \7hilst he was maaiager of the 'xlzanLc Steel Co., Buccseded in producing a tungsten steel, and its introduction '.vas a great advancement on the cutting po\7ers of ordinary crucible stcol, and for laany years "L;ushex" steel held a foremost place SEOngst tool steels.
It is no'.7 to America, hor/ever, that all honor oust be given for the next great step in having "set ohe pace" and led the way in the present reiiiarkabl-^ advajicement in special steels antl the greatest credit is due to liessrs. Ta}l - and ■"•hite, -Jho at the Bethlehem Steel "orks of Aiierica, initiated high speed cutting, and at chs ex/iibit of thoir firm in Paris soiae years back, wh;.. were th: concidered to be astonishing results in spaeds of cutting steel were publically iouinstrated. Since then, still grr-ater developrrionts Imve been made by the abov. fir.i in special steels and vith increased experience in its '-ai "factur-. . trc',?.t- ricnt and cpi"lication, results in cittJ-nj^, po-.vers far ""e- ond expe-.t: /'•io-i hc-.vt; "■■ev^ !;,tta^neJ .
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In ths year lo77 "t^ie jate Sir V'J.lliam Zien'-na oi London, patented a crucible t'onn of electric lurnace. In this furnace he v;. 3 able wixh c.oiDpa:3" tive ease to liielt 10 kg. of iron or steel by the aid 01 the electric current in one hour.
Basing his estimate of cost upon the results obtained by e;'.periments rith this furnace, Sir "illiaa Siei^eiiS claiaei that the olectric furnace aetho'. ^':' melting steel might be regarded as eijual in heating efficiency to a regeneratl^.v gas furnace i smca in each case the ton of s-oeol re^^uired the equivalent of one ton of coal or coke.
But the electric furnace h^ other advantages in its favor not shaded by furnacos using solid or gaseous fuel, chief of tliese being that the atmosphere of the furnace V7as uncontauinated with tlie products of combustion, that prac- tically any degree of heat could bo obtained in the charge of steel vichin ths furnace, and that this heat could be easily controlled by regulation of the e."^ trie current. Cn tlieso grounds the designer of this eai'liest form of electric crucible furnace prophesied that electric heating would become of considerable importance in the iron and steel industi'y of tlie future.
T'.Tenty years elapsed before airy progress could be reported in the dircctic. indicated by the late Sir '.'illi.am Siemens. But the mean time much iv ort'i-i.\. woi'k was carried out by the brothers Covels, Hall, "'ilson and Aciiyson in America, by Herould and Girod in France, by Borchers and Kiliano in O^raaiiy and by de Lavel in Sweden, bearing upon the practical application of electric hfe'iti'^g in the ^jroduction of aluminium, calcium carbide, carbonandum, graphite, feL-ro- alloys ejid zinc. Hoissan's res'^eaa-c'.es, althoti^h coniined to the laborat- ory nust also be mentioned in this coru:ection, for th.s Ic-jJious French chemist'- ' vrork vrs.t., the electric furnace lias become of classica- vaj ue and i jportc'r-- o.
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In these laboratory and v/orks trials of xhe electric furr/ice much valu- da infoniation rela'liif to the use of electriciti' for heitirg pujrpocen -jas gc'^nod. The best methods of controlling, the large currontr ucea, a.id of arrjinging the ix£5axi!:uxmciisxiin.'«jx electrodes co as to ainiiuuze xheir loss ai:d destruction during the heatiiig of the cliorge iii the furnace, were also 'rorked out.
In 1899 Horoult - vho had patented and brought into successful operation in Europe the process of aluuiiiiiuu extraccion associated '..Ith his name about the sati'; time tijat Hall paxented and introduced a ninilar process in America ~ turned his attention to the utilization of the electric furnace for tlie prnd'.ic- tion of ::pecial allf^yo of iron anu steel. A large number of trials '."ere Lnde in the works at Troges and LaPrsiz, in Trance, '/ith various forms and designs of furnace.
Success attended this early experimental -/ork of Hei'oult and from the pro- duction of ferro-rJLloys in the electric furiiace to the uaiiufacture af high cla. steels *.'c>.s a natui-al development of his procece. Atcenpts to snelt iron oror c.:' rectly by aid of olectric heac '/ere aade about this date, but v/ere not so suc- cessful, and Heroult from I9OI - I905 co^^fined himself chiefly at La Praz to the production of special rtecls, usiiig scrap and pig iron as the starting poir^ in the procRss. In this saiie period S'iassan in Italy, Keller, HerouJt anc" Cin in France and Kjfllin in Sweden vore '.'orkii-ig along the same line, aiid ijac.i of these electro install-argista had attained soiae degree of success in L'-.e produc-- tion of special steels by the new method of heating. In Aiaerica, Rutherbeig. Conley, Rossi smd ' 'ilson \jero also experioentiiig v.lth the applications of the electric furnace in the iron a.id stoel industry. Early in 190'5- ther.o nothodt. h?jd becone of sufficient importance for the Canadiaui Government to think it v/rrth v/hile to appoint a commission of exp-oi-ts to pr -;oed tn Europe to examJJie t; eir working and the repor'c of this comai^^sion published at the end. of 1904 a"!,t'-~ctei : ch attention irc:j me .li.r gists ir. ''3. r, "luries.
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The Heroult Steel Furnace ic being operated at La Pr?7 and 7rogr,=i ^ i ]7i-ance, at Kortfors in Non/ay, at I-.eianch6id in Gemroiy and at Syricuce in .he 11 '.it I Stater, in each case the plant being designed for the i;rius trial production of steal from pig iron aiid acrap, -/hile at Sault Sainte liarie, in Canada, experi- aents have recently been conducted '..'ith the Heroult f'Oi-nace f^r tlio smelting of iron ore. These expsrimental trials vere carried out at the expense of tJr Canadisji Goven'm".nt under the peraoaal charp;e .^f U. Heroult himself arj the ro • stilts cltoJLned are stated to have been of considerable premise and value as regards the ruiiding up of a nev; center of the iron and steel iadustrieo at Sault Saint ''arie in Canada.
IV. E. Bibliography. The reference chiefly euployed in this vork was an article ', y Mr. F. ". Taylor on "The Art of Cutting ;'etals," Proceedings American Gociety of r.eoh-- ahmcal Engineers, Vol. 28, -;,'3 '•''hich contains nany useful formulae co;anfccting speed, cut, feed &. life in round nosed xools^ partiiig tools, thread tools, and hard nose tools for heavy roughing vcfk, as v/ell r.3 discudsicft '^n chatter nf -cho work, effect of cooling ■^jater, chenical composition and heat treatment of tls i.teel. Other references aret-
Sja rk method of Grading Steel:
Sci. Am. Sup. Vol. 64 p. I96. Experiments r/ith a Lathe Tool Lynamometer
Am. Soc. I-'ech. Engr. V. 25, p. 637 Bulletin ■;/ 2 University of 111. for Mov. 15, 1405. Design of Machine Tools
Eiigineer I9O7 p. HO etc. Teorering & Cutting of High Speed Stee3'-, ■Tc ". Irn^ and Steel lile- J' "'v n06.
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