na A ~ ROSH ai iM OF a CARBON ae NS OF TH SU sty eS COA NTS Clie atl) Oh ae OF 1919 =) be << = 1 T 3 E DE May PE BY ar: Nyaa 8 amas 3 red a ‘ 7 ek teins Prerdeinata crium, but if the variation of one of the conditions causes a change, then the system is said to be in unstable equil- ibrium. Often a system will fail to underso a transformation when tne change is due, in this case it is said to be in a metasteble condition of equilibdriun. Third- By degrees of freedom, we mean the number of tne tnree variables, temnerature,pressure and concentration, which ay be cnanged witnout disturbing the equilibriun. If the systena has no degrees of freedom it is said to be "umvariant", and if it has one desree of freedom it is said to be Bunivariant", while if it has two desrecs of freedom it is said to be"bivariant? Fourth By phase is meant the homogenous physically disting- uisheble and :nechanically separable constituents of a systen. Fifth- By components, we mean thoseconstituents, the concentre- tion of which can undergo indevendent variation in the different phases. Howe gives a clearer definition,"those free elements and compounds which in the nature of the case are undecomposable under the conditions, and thus play the part of elements. It is some- times difficult to determine the number of components in a system » unless the following rule is aoplied. As the components of a system, there are to be taken the smallest nuaber of independently variable constituents, by ineans of wnich the composition of each phase participating in the sutee of equil- ibriun can be expressed in the form of a chemical ecuation, In ° the caseof alloys, such difficulty does not arise, as the co:mon-= ents are always the constituent metals, or some simple compound. Wnen cealing with alloys, the influence of pressure is gener- ally neglected, because of the fact that they are so feebly volat- tle, and are thus subject to atmospheric pressure. If the press- ure i186 eliminated, we necessarily reduce by one the degre:. 0: freedom, so that tne rule becones- PeOt+t-P This limits tne number of vossible pheses, for an alloy in equil- ibrium, made uo of X metals cannot have more than X pheses. If it uic “41 pheses, the rule becomes- Fe X¥+T1- (X¥-1) = 0 and tne alloy would not be in stable eyuilibrium, on the other ham if the alloy had X-1 vhases' then- F2e=X+1- (X-1) = 2 and the alloy would have the maximum number of degrees of freedom. PHASE RULE APPLIED TO ALLOYS In general tne inetallic elements way exist in either a liquid or solid state, and the study of what occurs as they pass from one state to another, brings in the application of the phase rule. We know that if a pure metal in the liquid state is gradually cooled to a solid state, at the temperature at wnich the change takes plece there is an evolution of neat. If we are ::easuring the dropa in temperature by :neans of a suitable pyrometer and plotting a curve, usin;; time and temperature as the coordinates, the curve would look lixe that +iven in Fiyure 1, Plate 1. The portion BC of the curve shows where the change of stcte occup there being an evolution of heat. As there is only one neteal, there can be only one co-:zponent, but three phases are nossible, (1) liquid metal, (2) solid metal, (3) alotronic forms of the se solid metal. In Figure 1, Plate 1, above the point T, we have all licuid, therefor one phcse and the rule becomes— Fe2-t%1#s1 That is the system is univariant, therefore we can alter its tem teuperature within wide limits without disturbing ites equilib- rium, At the teuperature T, we find crystals foraing in the liquid, thus we nave two phases present and the rule reads~ Fe2-220 and the system is unvariant. If we either raise or lower tne te:verature, we will cause the disanpnearance of one phese of the other. Pelow T, the system is entirely solid, that is the number of phases is again one, and we have- Feo2-1# 1 tne systen being univariant. Now let us turn to binary alloys. That is, those alloys which are made un of two metals. In this case we have two components and the phase rule reads- Fe2+t1-+P orjZ-P First let us exanine the cooling curves of a binary elloy. Here we have three cases- (1) = Alloys soluble in each other when both hot and cold. ! } : ' tt? tit . . it i geek tt ; ear ae : aces it Sea { elie Cone ‘ oe aes Vhs : ‘ lene re as i 2 + r ; ry ae ee le NB ea aga . | ca wee ja aae . : oa : tt es t % Qiae { Leechs = Ww Td Migcedtemess ¢ tit 4 ' at : nk : ii ; ies : ra ly hesew ; fer + : iy bp ts wh uly thretete tt ‘ : i - ‘ pe pedy : pbia pt * deere gE -++— 1 + ; ees} shy lt deae bee inde beet ane : : ‘ : me ; i abs ‘ sees ees een Rien eae ee ra + ' ‘ meee theta pe + , . + babes doe ue i ai rebge ‘ vie >, ra te beeeye staaee eege bee ee ad a4 ' ty ee + ite ‘ 4 =i sit Eat ' ee ar EEX. eg peirr , if hia ag OND treet tae a4 ¢ rept ide te \ peed ar ‘ thre titees oe ee 1 Vie ees preter te on epee ’ ye t ere ° Sybase e s te 2 agree a eee ‘ - - ~ ‘ ‘ é wt Loe eke 10 (2) - Alloys soluble in each other when hot, but insoluble in each other when solid. (3) - Alloys soluble in each other when hot, and partially soluble in each other when cold. Let us breéfly exauine case 1. A typicel cooling curve of such an alloy is shown in Figure 2. Plate 1. As the alloy cools from A to B, we have a steady drop in the curve, When the point B is reached at a temperature T, instead of getting an evolution of heat enough to hold the temperature constant, there is a slowing up only, the alloy graduelly becoming solid, but not entirley so till C is reached at a temperature T'. From C to D we nave a normal cooling curve, From this it is shown that between C and B, there is a gradual: precipitation of crystals and not € succen one as in the case of a pure metal. Fijure 7,Plete 1, we have the cooling . curves of a series of alloys of the same two metals, varying from 100 4 of A to 100 % of B. At a, the curve is similar to the one in 1, a',a",a'", are similar to thht in Figure 2, and at a"" the same as Figure 1. If we connect b,b',b",b'",b"", and b,c',c®,c"", b"", we will get a curve that can be used for any alloy of the metals A and B. However in this case we are attempting to pot both time and composition along the same line. Let us eliminate the thme factor, ploting b's and c's directly under each other. Our curve then is show by Figure 4, Plate 2. From this curve we can study the mechanism of solidification. Above acb everything is liquid and below adb ewerything is solid, while within the area acbd we have the transformation of one state to the other. If everything above acb is liquid we have but one phase and FP=xe35Z-12 2 V1 Which sisaply mesns that both the concentration cad the tenanerature of the liquid nay be changed within wide limits without disturbing the equilibrium of the systea, or which in this case means solid- ificetion. The sane rule apvlies below adb, excent that here both teanerature and concentration may be cnanged without causing the alloy to melt. Witnin the area acbd, we have two phases present, Liquid and solid and tne system ie univariant, that is only the temper- ‘ature or the concentration may be varied arbitrarily. In Figure 4, plate 2, let us consider an alloy of the composition R. As the alloy cools to tne poin y! crystals begin to precipitatite out, the comp- osition of which at the teuperature y", is shown by the point x’. If the point x' does not show the composition of the crystcl, then sone other point on the line y'x' must show it. Let us suppose that the composition lies somewhere to the left of x', then it lies within the area acbd and the crystal itself must be a nart Liquid which is impossible, while if it lies to the right of x' it must have become solid at a higher temperature than y'. Therefore it must have a composition shom by the voint x'. As the te:aperature slowly drops the composition of the crystals chenge froa x', to x*", while the composition of the liquid bath shifts from y’ to y'", and the last drop to solidify has the composition y'",. If the alloy is zradually cooled below adb, difusion will gradually takes place in the solid solution, 80 that all the crystals will have the composition R', In other words within the area ac bd, if we vary the temperature, the concentration will vary accordingly, or if the concentration be varied the temp- erature will change. Case 2- If we have a molten alloy falling under this case and THESIS or HAP PLATE @. TEMPERATURE FIGURE 4 TEMPERATURE COMPOS/TIOLY EO FIaViE F ros ZB 5 FUSIGILITY CURVE: OF A MARY i ALLOY WHaSE- COMPONENTS ‘HARE SOLUBLE Ii) FACH OTHE L TIME COOLING CURVE OF A PUINARY ALLOY WHOSE COMPONENT S| HAE INSOLUBLE | 1 EACH OTHER WHEN SOLID. <4 soe R Se LUD fFi- 24/-1=2 * i oe > RQ Hee 4 wae 97 Y ‘ Hp Ly ie ~ NS FH RW oO, 3 wf ty * iz e i te Mee 7 F22t-2 2+ 4 ; Ast * re fs ganas ne eee / A te Ped R SOLID eat f ft fe | : Gane Sb bY 3 G 4. “hk ff. FU OSLT IO, ide ceca eae WHOSE: oor NTS Ae PARYIALY SOLUBLE V4 ERCH eee SHOW TL PUBS, THE RF PPLICATION OF (THE 4 frit $4 Mls 4h . -* "4 cs . yt . Ly ‘ a. .7 --A SL , " . - 8 o . at . . ” * aoe . -, a a re an - Ls : . oy . Vo. wo ‘ eek er ee me ee ee fe tee ee em me ee ae oo . it _ ie wee = ere emwes Be = 3-w- eo - em ee Tg hte teh ere oe 7 7. j ’ ate ‘ “~~ . ‘ » j : ' 1 om - - i i “- 7 = we . ‘ vo, . . : aX or - ? { ‘ ‘, ees Sem, - ° f i ‘ ate “y oe } { . Te. - - ! ¢ Me ~ ° 7 7 ! : moe has . _ \ ' - “os wee, et . “ 2 . ‘, ta - } | : hs . . ‘ mo ! fo | : : ' " : . 4 } . ! ‘ . ) , ' ‘ he ' . ‘ ’ \ e ' . i . ' ’ . : . : . i ‘ ’ ' “ so } - - ee ‘ » . ’ . - . . : . , . ‘ : a | “wh : > 17 ! > * ' , 1 . . | ' - . a =e 2 6 + -@! ; Rovere ee welt wae le | , ' - ‘ - , ' a ‘ - J , : 7 . ’ N \ . 4 1 , * $ , . . + ‘ . . ‘ _ 7 ' ‘ - . 5 . ‘ ‘ : ‘ . . woe ee oe - ee ’ ‘ . * \ ‘ “> \ ' . . . , j ' ss , wo. ‘ 1 ‘ ! t \ wy Py t » - : \ . . ' I ~ | : 1 ' ‘ ; . i ( + ‘ : I -:N : to . a : . 1 4 Co OO . an ‘ ‘ 4 ' ; { . . \ t - N ; ; } \e ' { \ 1 t | . - : ( : ’ 1 ' ‘ ~ . ‘ ' ’ . d ”~ \ ' . \ . . ‘ a { , . ' . . . / o ; ~ ‘ 4 : “ ‘ . , : 1 . . , - » . ” f- ‘ ‘ - { , . ‘ ‘ ‘ . , ~ ‘ + oe a ; ' . ty \ oe a 1 ros , \ iv 4 , - . - ’ f 1 ‘ - . ’ ’ ‘ ( . aa . " . =~ ' - g 7 : . ‘ ¢ : ’ ro: p! ' : 7 . : . cos ' ¢ \ . “s € - - * | . 7 . - “4 - - e } © . . - 7 ' : . , . , —— oe. , “ . * ue ‘ . é e . - a : : 4 . . we -* \ ‘ - 7 “ ' ' “ . ’ “ j ; . } , “ af ° 1 , ‘ { a“ { : . - + o - 1 o wr’ 7 e ' , ° - ‘ : . ~ , . - * a * ' : . , : ‘| + ; . t ' , - ‘ ° 2 , . oe ‘ v - t . r _~ 1 . . ' ‘ » 4 : - . . : , . ~ of | * —~ os new ~ aoe - = com —~ -- = . , | ~ , ; wey “ : rs “ ‘ * , -* ba’ ; . a . . Xn ' r - . . a . a 7 somos ” 7 ~ . as a . a” a ‘ : ‘ \ a ‘ : : “ - , f - at - a ome ey ee * we ee ee ee ‘ ~ “ bees 4 f . r ’ -” = - . =" . , “ , , aie ef mo t- . “4. ee eee tee mee eee ee 13 vlot the cooling curve, it will taxe the form given in Figure 5, Piate 2. Here we havetwo perts to the curve where solidification takes place, namely BC and CD. Also we find thet no matter what the percentaze of each constituent the line CD always falls at the same temperature, Case 3- This is simply a combination of case 1? and 2. That is metal A will nold some of metal B in solution and B will hold some of A in solution. If we plot the cooling curves of a series of alloys of both A and B, omitting the time factor, we get Figure 6, Plate 2. It will be seen that at the point b, or the eutectic we have a percentage of each metal where soligification takes place instantly. At this point we have two phases in the solid state, consisting of two solid solutions, and also one liquid pnase, Taxing an alloy of a composition R, above a be, we have all liquid, therefore one pnase and 2 degrees of freedom. When the temperature L is reached, solidification begins. This means two phases within the area a be, and the system is univar- ient. The first crystals that form are solid solutions of A and B having a composition 8. If we shift the temperature to S'L', the composition of the crystals change to 8', and the comvosition of tne liquid bath becomes L'. If we lower tne temperature to eb the composition of the lighid becomes b, but below eb, everytning is solid, therefore we get sudden precipitation of the liquid whose composition is denoted by the point b. The structural composition of the solid material would consist of crystals of the solid solution of B in A, these being well formed, if the cooling tooK place slowly, and an aggregate of finely divided sol- 14 utions of B in A and A in B, the coupositions of each being shown by point G and H. However we still have just two phases, therefore the system is univariant. As the iron-carbon alloys belong to the class of binary alloys, the constituents of which are partially soluble in each other when cold, let us examine their fusibility curves, and anoply the phase rule to then, In this case we have several allo- tropic changes as well as changes of state. These forus can be zrouped under nine heads as follows- (1) - Liquid iron (2) - Liquid Fesc (3) = Solid solution of FezC in Gamma iron (4) - Solid gamma iron (5) - Solid beta iron (6) - Solid alpha iron (ferrtie) (7) = Solid solution of C or Fe x0 in beta iron (8) - Solid Feo ( cementite) (9) - Graphite Figure 7, Plate 3, gives the cooling curves of the iron-carbon alloys as far as ° 4%0C. Let us apply the phase rule to it. Above the liquidus, we have only one liquid pvhese, and consequently 2 degrecs of freedom for Fs 3-1 = 2 Within the area LSE, we have two phases, namely liquid solution plus solid solution (austenite) and therefore only one degree of freedon, Within the area LAHDS, we heve but one phase, a solid solution and here the system is bivariant. As we reacn the point the point D, the system becomes non-variant, for nere we have a ee ee oo se oe ee eee eo ee -awe we me ——-> 5 ‘ we ee es .. . “ Tm ee . hoe 1 > a on wee . nee we ee ao. — ee ee wt we awe 04 we ee mee. See nme es - were - ‘ ame ee ee -- : 4 ~ . . . r . - ~ oo - wR ‘ eet ‘ ‘ ye ae 4 ae ee ee wee owe amen en em A ~ Meee ne ~ tT ae a ‘ 7 ‘ wf , : ty . : : 2 _— . I - + : *% ‘ + y ceo -, ' . 4 ‘ t _ { ty eee ee Bet ‘ a ~~ t ay | . . ¢ | arty} \ y ‘ . 4 Mee 4 ’ \ ‘ ‘ ‘ ‘ ’ ‘ ' j s ' wee eee foes ce od i ‘ ' t é “se on _oo 7 —< er and . “ ” oo a * oy oe. 1 ‘, : ‘ , YN a ‘ ‘ a * a at Q : By . o . % \ . ne = 7 . ‘ . . . wy me - ‘ a rea 16 austen ite ferrite, and cementite as the three phases. In the area DSS'F we have two phases, namely austenite and cementite and the systen is univariant. Within the region ABH we have beta iron and austen ite and the system is univariant, while in the region BODH, there are also two vhases, namely aus- tentte and alvha iron, the system still remaining univariant while finaly below CDF, there are several possible cases. Case 1 - The cementite formed during the solidification and cooling remains unchanged and we have a univariant system the phases being ferrite and cementite. The system is how- ever in a metastable condition. This Le the condition of the slowly cooled steels of commerce. Case 2 = The cementite has been completely changed over to ferrite and «srapnhite, giving a condition of stable equil- ibrium, Case 3 ~ The cementite has been partly decomposed into graphite, thus giving three phases, and therefore a non- variant system, this being the condition of the slowly cooled gray cast iron of commerce, 17 CHAPTER II We find that in dealing with metals, particularly in the solid state, the time factor in cooling plays an important part in our final structure. If we wish to obtain material from which we can pick out the different components, by means of a medium powered microscope, it is necessary that we allow the metal to change its state slow enough, that the differ- ent components have time to adjust their crystals. At tne same time, we cannot allow te long a neriod on account of tne expense involved. As tnis work deals only with carbon steels, I will outline briefly the results produced upon the metal by differant rutes of cooling. Wnen a pe@éce of steel is in the region LSDHA Figure 7, Plate 3, it is composed wholly of austeni.te and is in the solid state. As it passes thru the unper critical ronge, there is a change of state, from one phase to two and at the point D, we have three phases present. @6n account of the material being in the solid state, diffusion takes place much more slowly, thus requiring a longer time for the reaction to complete itself. This means then that we have a change in cyystaline structure, If the steel is allowed to gradually epproach AHD, and gradually pass thru the transformation points sufficient time will elapse so that the new structure will be fairly perfectly formed into its basic structural constituents. On the other hend, if the time is greatly shortened, then the crystals will not have time to reform 18 before the metal becomes so cold that movenent is impossible or at least almost infinitely retarded, and we have a structure from which the components cannot be easily picked. However this may increase the value of the metal from a commercial standpoint for certain uses. I have attempted to show this in Figures 8,9,and 10, Plate 4, Let us take for in:tance a steel whose composition is R, Figure 11, Plate 4a, nemely 0.5 %C. As we cool it to 1, tue first change from the solid solution takes place, ferrite being thrown out from the crystals of austenite, thus making the remaining sucter.ite richer in Fe,C. If these ferrite crystals are allowed to prow pradually, they will get a chance to form a fairly cefinite structure, but if we suddenly stop this growth, by cooling the vhole mass sudden- lv wv ) then they will be toe fine to distinguish cleerly by the usual means. Ont the other nend if the growth proceeds at a normal rete, more ferrite will be thrown down, and segregate in large crystals, till we reach the line CD, when there will be a sudcen precipitation of the ewtectoid mixture of 1 part cementite and 7 parts of ferrite, forming a fine sggregate. Figure 12, Blete 4b, shows this teking vlece in five steps, first eustenite crystals, lastly ferrite and pearlite. As the range of temperature becomes smaller, where precipi- tation can take place, that is ss we approech the eutectoid point from either cirection, the cooling thru this range must be morc gracual if good results are to be obteined. Fowever some pearlite is likely to be caught in very thin films between the ferrite, even with the slowest cooling possible. ° tH t rit TT i ry ! r +444 3 I ti + +4 7 t pio | + _ + +Tt++ | rT +14 THT shea | ort ttt t t + +344 Y rr eee! tot +4 +. saa +444 Ly } ror oi tt ri ao i + Tt ei ty Pat i rh | + + H +4 tit t : i | t 1 Tors | 7 { eee ms + + me ae t q rit 4H ttt do Troha it } } Laat } oe +4 | + +t oo es 44 +34 444 1 i ttt Coe " ny ; iG 1 Ce as Le TTT t +4 ri sae ee j ; } } i+ Hi tae | ra na it +H roe Teas ro soe i ; rot rot saeeee naa eeeee aes ioooe ; hy Seenee' mw seReeee t I } ; { rity wri | : poy my ws 1304 tt I iid : od ++ ; t + + . ‘ | +++ +++ + + + + + toa + . te te + Wo aoa Pry nas tT Tae ttt i : | | | tit Coa i { t ; no SEEee ia i 1 ! 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' car ee — 3 OEE ry Iss tt OM ee OO “GR GY CA ON GAT FRA ; HO LL t ' y ' , € ' i ‘ 5 ; ; F 5 ’ . : - - -_ - eee Sw Stet ome — me et te ee eee ee - - «- 4- ——< a —— = a, ~ v3 -- > - a7 tas or) rig te 273 2 ave S Qa eee NN Las “ WAVE MS —~=\ NOt au ah Vir. ‘, \ Wy « 4 < Pe. qa Y < a? + % 1 oe a ee a © Ege 4 \ Nome Gee ae rea 5 te got he 4 ad 2? te Fee CUGENE DIE TZOEN CO CHICARO EW TORE Noy 350 . a — ——————— eee en ren n wae meee Zoe ve oa . -—~ . - ’ a tty . . ve 4 ” \ “oe we . . . ra - ve x, oer. . aor . te 8 te ae. ' ™ eg WL Ga. ee we aetna = one noes . o ”. ~ . . . s . oe We eee Ne ee tla ee ee . ia a) ot 7 x , a . a wee +4 - -- + -A Soe - ~ ctw "oy - - an, s - 4. ~ : . - ~ 4 7 Tae - a | : ne mee { - sow ~ i? . ot rary ~ ~ y toa vee ~ A - . . - * 4 1 ome oe . 1 . ~ " . . oo - - : . « + . ~ + - . \ we . ~e , : ee ~ vat ee ee eee oe m- ows + » ae eam eee ee oe : ‘ . ‘ ee 69 te a . ' . foe . “ONG te Po ee © . oe meme ae: 2 OR. ee mas oH my ee ee oe ~_— a Pom e-- +e a | co "9 vos ~_ - coe oo ee ~~ wee e —- ~ r - ~ ee eee see - ‘7 = —-- . -- —- - t : ~ > - ce = cote se . ,. - - - - - e- - . | ~— - - - eg. - L oe eee : ’ - - - - - - -~ +e ~ ee - _ oo. , * . i « - ~ wee of motte a3 _— co RE Roe - - 3 : - - - - -- - & =. wee . -<- ~ po “FU. 4 " - - - 2 - - wee : oy oo, SBT Coe bee -. - Mo eee j 3. - soe “5 - “+ oot - ’ ane Oo) eh ee Be etn Wolly wet A ee ee RS ae .- : . ‘ wee - - _ ~ . t ~ we eee - - - - ~ -- 4 - . om - we . 7 gore . “ s+ a . . 4 . , . . . ~ . . woos . ve eee - - +e @ ee -- - mc o-e ry _— -- wee a oe 1 “ . . ate Seo .e Vo - 2. ~ -- - ae . . .@ ST, moa Dee ~ ~- ou -- - os } an . + ™ » - . re 4 ' * . - ~ - “os . ee. le cee Be ee eee! . . _ a” > ‘ a . vy - . . r . . . . ‘ a . eo: -a’ . , ‘ ' cy | 7 7 ‘fs . - . - | oom es "% é -~ > ae , ? -- c ! - ‘ $ : ~ i wor ¢ TG ' ‘ Q) t i i t 4 ‘ ‘ ‘ + eee eet - . see eo 1 Ger new - me me es - 7 ewe ee re me y ‘ ° 1 i , ' \ » . : ’ . - se e . . . : : . wet - 3 - i , . t rt : - ev ' ? . ‘e wos - ’ , . ; ‘ : . - ve 5 q : we ' j ‘ 3 ' 5 . ‘ 6 - ; Le . ‘ 2 . . ’ ' ’ ¢ : ‘ - ‘ { 1 7 , tor ‘ . + . - 7. ‘ : | : . - . - - - - 2 Sarees pire e wot ‘ . ’ . : ‘ » +: . « . » & - . id “.¥ . ~ a x . - . ~ ~ . - . -t , i ~ om tm 4 ‘ . . . ‘ t > ‘ . 7 ¢ mis tl s PUM ENE UE TEOEN CO CHITACO KEM DBE ENO, IEG oo - ' , ~ ” , rot fogs My Qh or awe ak - 4 w\ : AM : ‘ en a - N ‘ Moe ot x oN o af ae 7 ° - “~ * ar X ’ “ ‘9 ‘A , . . ‘ ’ “ if “ * 4 : . 4 . ws > e - . . ys toe 1 : on + “4 "4 om ) 2 . jo . - a? . “7 - -— ‘- Dal - . eee wenm em ee ee en ee nm me es ee eee we we me ee me > ee Stee wee meee atte we fener fnew ee Yr} . { a : : . . . ’ =. 2 ee wee eee a wwe . os . } \ ’ : ; “ . 4 - 4 . “ ‘ ‘ ‘ m sa 1 . ’ \ . 2 , v $ . \ ; % ’ . 1 ; ‘ * ‘ 5 ‘, Yee mee nm - - ea ee Ae rm oe ee - ee ee aw ene sk s+ oe ~ sot . . ‘ . 7. ‘ ‘ 7 . ‘ \ ‘ . . ‘ ‘ \ 2 ‘. . . . r ‘ , ' * : o- sd ~~ = ~~ - ~~. ‘ . ‘ 4K ‘ wr " 4 % iL t \ . ' ‘ . ‘ ‘ - ‘ ; y , . . ” \ i t 4 -° , : a? i . : \ i a ' 4 ‘ . q ‘ . ‘ ’ ‘ . " , : . -. ’ ‘ . , : : ’ ‘ ‘ : , y ‘ ‘ . . ’ ’ 4 ‘ ‘ . . ‘ ' A . = ' . e . -: - .- ~~ nie oe eee wa ay ~ wee ew ue at tet mere wt ne na we we ee aot oe bee ee - wee tw lt ee oa «se . 22 If a definite relationship can be established between the pvercenteges of these constituents and the percent of Carbon present, we will have a simple and accurate method of determin- ing the vercent of carbon, Commerciel carbon steels are never pure alloys of iron end carbon, and the emount of the imputities affects both the critical points and the position of the eutectoid point. However the amount of impurties is limited by the specifications under which the steel is purchased, and for carbon steele of fair grade, the amount allowed will not introduce enough error to cause any trouble. In the case of hypo-eutectoid steels tne relation-—- Bhip between the structural and chemical composition as re=- gards carbon, may be found as follows- we know that the whole mass is composed of ferrite and pearlite, therefore- re P = Foo Where F = the percent of ferrite and P = the percent of pearlite. Also all the carbon is contained in the pearl- ite, therefore& E/129xP = C Where E = the percent of carbon in the pearlite and © = the percent of carbon in the steel. Also as the carbon is present in the shane of FesC, by molecular weights Pex contains 6.67 % C. We do not however know the exact posit- ion of the eutectic voint, but simply that it lies very close to 0.85 % C, the exact ~osition devending upon the chemical composition and the neat treatment the peéce has received. Assuming that it is 0.85 % C, we have 6.67/100 x “CO = 0.85 2) 2 C = 100/6 67x 0.85 = 12.74 or the ratio of cementite to ferrite in the pearlite is about 1 to 7, which places the eutectoid point at 0.834 %C. From this we can easily calculate the structural composition of a hypo-eutectoid steel. The total cexentite will be = to 15C and there is eignt times es much pearlite as cezentite, we will heve the total veerlite = total cementite time & or P will equal 120 C, Figure 13, Plate 5, gives the results of plotting the percent of pearlite for any percent of carbon. In the case of hyper-eutectoid steels we have only free ceinentite and pearlite and here P + @m = 100 also B/10c P4+6,67/100 Cm = C as all the ferrite is contained in the pearlite, and therefore tne total ferrite = F = 7/& P, or “p= 8/7 PF, but FP» 105 - Cm therefore P = 3/7(100 - total Cm) but Cm = 15 C substituting Pe &/7(100-15C) or P= 114-176, These values are also to be found in Figure 153. Plate 5, as well as the corres»nonding values for cementite, total and free. From Figure 13, we can therefore determine the vercentage of the structural constituents. For instance, a steel containing 1.2% C, contains $2 % P and 13 % Cm, while a steel containing 0.5% C, has 42% F ane 60 $P. On the other hand we can reverse the use of the diagram. That is if we know the nercentaze of the structural Cconetituents, we can determine the vercent of Carbon. For Bye NE OPP UB Le ca nee Ome NU 35S sates ae wt ee ee — = ene Ow wre em ee “eo wom “ene news ee a ed — eek 2) example, a steel containinz 30 % of p and 7) st of !F, contains 0.25 0. In order to make the reading of the diazran more Bimple Figure 14, Plate 6, has been drawn, Here the pearlite 1s siven in one continous line, as are aiso the other constituents, in order tnet the reading may be ore easily done. Thus we neve a clearly established relationshinv existing between the structural components and the percent of carbon present. The only renaining difficulty is to me.sure the vercentages of the structural constituents Simdly and accurabety. I? tnis can be done, we will have a .etnod of deter:aining the carbon content, which will be a great aid in checking the chemical commDosition as deter:ined by the combustion method, if indeed it does not tell us far more tnan the latter. . i i. ke ‘oe ww i en a a ~~ a ~- - oe’ : --_ . 7 ot x aoe oO ~ . - — ie x, on“ N _eeen ~~ a _-_—-- q an * aoa -~ar* \ we OT ‘ wee aoe - o_o s oa - ant? . * y ‘ . X ‘ “ > x ' « x ‘ 4K "3 ' . Ks ; oo: * . . . . : ,t ‘ . so ‘ .. ’ No vo a . 1 ‘ se ‘ . us \ - oo * . ? eo . 8 - ' - - . - oa -y an , \ , - : . rt ‘ : . 1 > . . ‘ s ‘ > 2 \ a ass > “ . 1. - ‘ ‘ . \ a. - . . ‘ . oe . x : t ’ \ s ws . 4 5 . ) 3 * ‘ . : . \ . sf .e -do. » s : . ° soa r ., ‘ . . ‘ 1 y ‘ x : . % XN \ *y “ ‘ ne - . cone . . oan 1+ . wa « ” ‘ . Me ’ nn) ‘ * - . e ee . ‘ ’ ve . . tae “.. «- - - - mere . . - - ‘ ‘. - 7 oF . aa : . awe ee - : we . wee vie _ eo, nee : Yo.. “ ce , - . Lo. eon . ' 5 - x . ms ay ‘ - . ow . ‘ . se ~ - . ° Tee ee eo . oo vom sae . . Nee ~ . a -. . « , - “—- rT woe - ten, . oa . - om 8 F . Se ee oe Fo eee 2 ow Com Mm Let ee! O62 aN wees em rem om 6. ww. 0 ehh ben ee a a Pm me am rome Leet ates a Oe we re a ~ e ae - . oom o- . ‘ , \ . - 4 . ' . . : ‘ ? . ‘ - . . ‘ \ : \ : . : c . ‘ . . . ( x + . ,? ae . 1 . - v4 4 { a . ve ‘ ‘ NO: * ‘ ‘ te oe * a ' ‘ of CoAT LK iil In order tnat a clear uncerstanding aay be had of tne methods used in the following work, a snort cescription is ziven below of tne annarstus used, None was used excent sicn as wignt be found in any fairly well ejuipped lasrctory. The saaple to be tested was polisned in the usual manner, using “SF elundum on broad cloth for the final volish- ing. The soeci.sens were etcned with a 5 % solution of HNO ? — in St 0H Two tyves of microscones were used. The first Will bear cescrivtion, as it was reconstructed frome a reculer instrument. In fact this one was used for all the work, the re.cular :netallursical microscone not beinzs delivered till late in tne spring teri, Tnis latter machine was a Bausch and Lomb reszular OCM with a .sechanical stage and all the necessary attacinaents, This was sounted upon a canera made by the saue firm, liznt being furnisned by a new tyne arc, witn an aspheric % coudenser. This outfit is shown in figure 1°,, Plate 27. A picture of the nomemade apparatus is given in Figure 16, Page 27. The microscove was fitted with a Leitz dark field illu: inator, the substazge removed and in its place was substituted an electro naynet, caneble of :novement in two directions by means of slow :iotion screws, Lignt was furnisned by a Leitz Lillivut are lann, fitted with a bulls eye condenser. The lamp and microscove were siounted uvon a board and the imaze thrown ezeinst a clear glass, fitted into a sxetching board, suonorted by «a nickeled rod, the board being cxoavle * THE NEW micnoscope did. net come till May (4, 97. FIGURE 16 | BOTH OVTFITS MOUNTED ON THE SAME BASE. METALLURGICAL LAB. MAC FIGURE 17 SAME AS ABOVE, SHOWING DETAILS. fo \O of movement on the rod, and also horizontally around it. The tracing paper was slioped under suitable clins on tne board and the image traced off, This formed a con- venient and easy meynod of sketching tne structure of the pe@ce. It was found that a magnificetion of between 100 and 200 diameters, was great enoush, if the sample had been given proper treatment, so that the various consti- tuents could be easily distinguished, and the outlines of tie crystals traced with a sharp pencil. There are several factors, which will, if not taken care of, produce results far from right. Case l- Improver heat treatuent. (A) Too rapid cooling. (B) The temperature not being carried above the unver critical voint. Case 2 - Improver etching and polishing of the surface. (A) Over etching (B) Spoiled etching solution (C) Improper drying of the specimen (D) Poor polishing Case 1 — (A) If we cool too rapidly, we will get a structure i which shows that the ferrite, if it is a low carbon steel, and the cementite, if it is a high carbon steel, are tnrown out suddenly, witn the result that the crystals become jagged and sharp and poorly formed. Tnis is shown in Figure 18,Paze 30 and in Figure 19,Page 30. These pictures show 3s medium and a low carbon steel. Bothwere cooled, by simply 30 removing the pieces from the furnace and allowing them to cool in air. The temperature of the furnace being About 1700 degrees F. Ficure 18 Magnification of each about x 120 The effect of under heating is shown in Figure 20, this being the same sample as Figure 18, but the temperature at which the sample was treated was about 1000 degrees F. It will be noted that the structure of the ptece is the same as that of the specimen when regeived, this being shown in Figure 21. Figure 29 Figure 21 vo Heated to 1000 deg. F As received Magnification x 120 51 Case 2 - (A)(3)(C) If we allow the specimen to remain in the etching batn for a long period of time, as the action of this bath is one ofcerros’ on, the mere outline of the crystals will not snow, but the different crystals tnexselves will be eaten away, causing blacking of the surface in snots end areas will appear nearlitic, which are really ferrite. The actual error introduced will be shown later on. If the etching solution has been used a nuuaber of times, it will contain iron salts in sufficient quanity to produce deposits uvon the surface, which will give a very different structure tnan tne real one. Thnis will also introduce error, Then if tue soecimen is not dried rapidly, films of oxide Will denosit , wnich will spoil the surface for carbon deter:sinations. (D) If just the carbon content is desired, then the surface need not be entirely free from scratches, all tho very few should be present. If we desire to keep a ver& menant record of the sauple in tne for:n of a photograph , then the surface must be free from scratcnes. In some of tn&B work we wished to know tne actual size of tne crystals, and also the distance covered by tne drawing. The method used, while not the most accurate, gave good results and wes very simple. The draw slide frou a slide rule was inserted under the microscope, instead of the snecimen, and tne instrument focused on the log seale. As tne divisions cane to a sharp point, even at 200 diametes the distance could be accuratly :.easured between points, and this distance measured a--inst the actuel aceale. Tne nuuber of times »reater,the cistance between points ther D2 one division of the log scale would give tne mugnification. If this was found to be 160, then by a simple calculation one inch of screen represents 1/162 of an inch on the sxecimen or 8.0062". One square incn of the screen then ne@ans 0.000050 sq.in. of svecizien surface. The cross section paner usec contains 20 lines ver inch, therefore 490 areas ver sq.in. If a crystal covers 50 areas on the section peper, the actual crystal covers 0,7 00356 times 0.125 = 0.0000043 sq.in of surface. Or! \N ChActin IV xeeping in mind the errors which can ecsily occur, I wished to formulate a i:ethod if possible, by which the carbon content of a given sample might be determined by an exemination of its structure thru the microscope. This 1etnod must be simple enough to be used by the students, and at tne seme time the results obtained must check combus- tions run on tne s-me ssmole. First six ty»ical sammles were selected. These were of Carnenter steel of very good cuality, and gave a range of carbon from low to 1.2 %, The samples were nunbered as follows- A,D.E,F,G,H. The above samples were analysed by cirect combustion. The absorbing medium being Bakers Soda Li:ne for Compustions and consisting of Nace = 37 % Ca(OH), 2 45 5: 90 2 15 % Filings were taken frou several bars at various places a.id well mixed, s0 that the results obtained would be general as far e353 nossib.s. The results obtained are show in Table 1, Page 34, ™:4a@ pnelysis falls within the limits usually required, Then by tie methods vreviously described the carbon percentage was ceter-zined. Accordingly a .1l@cze was cut et random fron onB of the bars, marked sample A, treated and tested. XN Table 1 No. of % C ~ ¢C % C Sample Trial 1 Trial 2 Average A 0.16 0.18 I.17 D 0.28 0.31 0.30 E 0.64 O 67 0.65 F 0.78 0.80 0.75 G 0.85 0.90 0 69 H 1.19 1.21 1.20 The average percent of carbon was taken as the standard value for checking the microscopicel analysis, oD, Three ps@ces were cut from A anc marked A=1,A-2,A-3. A-1 and A-2, were heated to 1700 degrees F. A-2 wes co-t*0 in the air A-f, slowly cooled in the furnace tiru a period of 24 hours. During the first 6 hours the temperature dropved from 1700 to i200, during the remainder of the time to 75 degrees, The sample wes then cut in Llo,:. so that the «nterjor might be workec with, where no cecarcurizing effects had taken place. After cutting A~-1, the surface wes filed and enouyh filings obteined to run a combustion. This giving the chemical composition of the steel as close to the stru- cture examined as possible. The snecimens were polished, etched with 5 % HNO, and examined. The structure of A-2 was sketched upon cross section paper, within a two inch circle. Three different voints upon the surfece were taken , average structure being selected. Plate 7, Page 36, gives the original drewings under figures A-1-1,A-1-2,A-1-3. In table II will be found the results of the three dettérminations to- gether with the results obtained by the combustion method. Figure 22 Page 37, gives a photogrenh of the specimen. After polishing and etching, Sample A-2, was exaniinec and e photogrenh is giveh under Figure 25, Page 3/. It will be seen that the crystals are distorted, and overé lap eachother in such a manner that it would be impossible to sketch them accuratly. The method of determining any given area of crystels wes as follows. The number of squeres within the area were counted, and as each square was@ passed, a slight mark was placed upon it with tne »-ensil. The counts were mede in series of 100 at a ti.ce. SUG ENE DIEZTZGEN CO_Ch , 1 - tok, - ie 4 ee Y : . -; . * a . = se . ° 4 Sy : toe “a ” - , . ~ -!@& as a - . : . ‘ ’ . mo » ! y . oe ta . . -- . a - - , . , . « ’ - . 3 he ees aa . ? , r + ‘ . . : . . ty, : ‘ - a lgli a +3 4 f . ~ : coe me tee. ade TAA ST. i . ' ews ~ oe : . om . - ~ - . { . . ee ‘ . , . , re - . a . . ‘ \ : ' . ~ . 8 t = po . \ . = . . . . ‘ 1 r * ‘ ~. ‘ d » ‘ ot - me . . ; 7 ' «- , ne! . : - . - ae . s , ‘ Nar . te ‘ aa ’ » a y ’ ‘ wee fon +. eer : oc 4- -——— at Figure 22 Fighre 25 Sample A-2 Heated to 1700 F Cooled in air. Sample A-1 Heated to 1700 F Cooled in the furnace Figure 23 Figure 24 Sample A~3 Semple C-1 Heated to 1530 PF Heated to 1700 F Cooled in the Cooled in air, furnece 38 TABLE II Semple Heated Cooled Aree of Area of %P %&%0C “ ¢ No. to in Pearlite Circle Combus, TI-T2-Av A-1-1 1700 Furnace 221 1259 18 0.15 A-1-2 1700 nom 198 1250 16 0,18 .16=.18=.17 A-1-3 1790 "oN 204 1250 16 0,13 From the above table it can be seen thet the arees hed a maxium variation of 23 areas out of 221 or about 10 %, But for 0.1 % GC it requires about 150 areas, and in the 150 there would be a maxiun variation of 15, or this would be equivalent to 0,01 “ C. Our chemical anelysis ceme only within 0.02 %, giving an average of 0.17 %, while the average by the physicel method was 0. 143 “, or 0.027 % below that obtained by thie cherictl 1) ess, This result checked very well with the seneral analysis made, and given in table 1, The next ps@:se A-5, was treated as follows, "xf eated to 1900 F and cooled ta the furnace, This treataent took the neece only a little way above the critical point. The staple wag polished and etched in the srsze man:er as A-1, end the results are xivena in Plate 7, Pave 36. The aress ares A-§-1, A-3-2, ‘a o of the differeit points are given in Fi om - Cc ry _ i NX oe - . ’ y, 7 s ve - ” and A-5-%., Fisure 24%, Pase 37, gives & photogrs, 2? From the pnotosranhs of the different saanles taken fro bar A, it can be seen thet slow furnace coolinzg is necesurry, and that for low carmon stecl3s the meximum teanerabure snould be above tne upner critical point. That tenderatures between 1500 and 1700 F, will give good results iP the cooling be slow enough. Next sa anples D,E,G,H were given the sane trealinent ag oar A, and the resulta are shown in Table 3. The sys tea of awabering the different viéces is the same as given for sumple A. Theat is the letter stands for the bar number, the first fizure for the pe@cre taxen from the bar, and the second number for the ares of the a@ce, It will be noted on examining this date, that in b neorly every case the % pf carbon by this method fell a Little below that obtained by the combustion method. Also that this di*rerence was very neerly constant except around tne eutectic point. At this noint, and for a little way on each side of it, it is impossible, even witn the slowest treatment, whnicn could be economically given, to distinzuisna eitner free ferrite or free ceaentite. I believe tne reason tnat the nicroscovial anslysis ran a little below the cheraical was due to the fact, that in the mechaniam of solidification some of the nenrlite is caught between the ferrite grains and thus lies in such fine films that it can not be measured at the neznifisation used, In tne case of high car0a steels, the ceuentite areas were courted, and the sane held true here. If we sive each sample the sane heat treatuent, for like carbon content, we will get about tne same error. TABLE Samvle Heated Cooled Area of No. to in Pearlite A-1-1 1790 Furnace 221 Aet-2 1790 "oR 198 Ae1-3 9 1750 #" ° 204 Averase A-3-1 15090 Furnace 222 Am3-2 = 159 nn 233 A-3-5 = =1500 oon 218 Avera,e D-1-1 1700 Furnece 452 Det-2 1720 "4 415 De1-3 1700 on 458 PVeCre e EFe1-1 1750 Furnace 975 Eet-2 1720 mR G78 Ee1-3—= 1720 "oon G68 AVELrEA OC Fe1-1 1720 Furnace 1141 Fel-2 17C0 rn 1144 F-1-% 1770 m4 1151 Avernve Ill Area of S%ircle 12590 1290 1259 ret ‘7 P 18 16 16 18 19 16 36 2? 78 738 TT 7 3 © 9.15 0.30 cf (2 & Combus, mo + 7 , 17 17 SN 7) oVé, 1? yee és ~ > en. - VEYe xe <3 Sample A,- Sample D,- Sample E,-= Sample F,- Sample G,- Sanple A,- 1790 Furnace 1700 "oA 7oo 202€«©ZL Cin 1720 Furnece 1700 4 1720 "oR The original tracings Plate Plate Plate Plate Plate ‘Plate Table 3, con't, all all ell 1174 1184 1172 nay be found on the following Plates. 7, Page 1) Page 11,Page 11,Page 41 36 42 4 43 4d Ad 199 100 100 od G9 94 IAN Derr EN Ce cHicaae mew -ORe NG 390 pwacens sn or Ao kan obrol “ GC eo . . fa e v a Ay a AY ra Ny 3 aN : Ss AA me RENN an. ol a Yaa an Dy ante wet pre ee eee an ce 1 - oe ~ ay: # : Ra? NE Ns S x2, PA 2 f i a 7 eT “7 ‘ Se : r ore a as het ee ; sea ee ee ae, Dae: cords a <9 a tape ee 2 E : : ; ‘ $ t 2 a 7 z ‘ 2 1 t . 2 ’ . j : ; ' i 4 a Dens 25 é a, Ses tS “ ia tay Cae) Hg ae Selo DAY, VOSA AD VAL Pk SN FLQENE © Ta SECO cn cacs iw rere ee. sou 3! “ Aan o 1 : : a eT ie no +. a ag 4 in . if ee eee | SAA TSS etmenh seem : ’ 1 oi Sy taro: o hate | ee ae ee ee AAT OR BWA AQ WAR Ne ee os eo aes 1 : 4 1 ' i : TAMARA AD + ' i ' : vn ASARAWSA HG BARI awe S . ' ARRAN WL Woe & x * nay Sass eune hey hy) Rey a » ee ee ee eee a - -- 4 ney Hts An Tee KR WS a YAMAZ SN) & ASAE ay Vriwne vee =i ee esd ee . ee w G oe nee tCLORN CT OH CASO VE ORE ONG ‘ . bets . j ‘ ‘ ; ; ; } | | | | ' : ‘ os ; i ' . , ‘ ' : —_— - ar ee =? Mas = > hy ss ee x SO ihe ad eee 3 ; ss “i a . a oe Shae am eid Bae Gas ie ahr ae Cu we ANE 4 b: wee by +t eas tid AER Ce : ,* = oS u¢ Je z , ens ss a * : oa wes ! ‘ ' Sag ‘as wie e - ae. gash Dhl a ¢ & ‘ $i. oie : L Fi z - ee co » - * : 5 - at 5. uae ee on : Fs io wv? A WG LVDS 1 . ‘ .< - oth ow pan gi “ Pa ft oo a “ 3 ee z : ! 4 a | es a” - Pd ' ¢ gh z é ‘ 4 . < te ov See oh 2 ” Cad ‘ : 2? is s e a r © 2 e : 1 « - ‘A z cha ays ax = od ' ' ; f ve oi , a a. ; "ay 8 a : . | $e Sng - me wee 8 ee te et wee eos een - -——- we eee ee i ee ee ee ee ee ee ae mee ee Si - 45 The results given in Teble 3, I have plotted on Plate 12,Page 46. Not using the aversge value for the difference, but the maximum and minimun, for each sample. and tnus obtaining a curve which broadens out at tne pnoints where error occurs. The true pearlite curve is also given, as taken from Plates 4 and 5. It will be noticed in table 3, that sample H was heated to 1-CO F instead of 179) F. This was so it could be taken above tne Acm line in order to set complete precivitation of the cementite. On Pages 47 and 48, may be found vhotogranvhs of tne various samples, showing the incresse in the amount of vearlite present uo to the eutectoid point and the cementite surrounding tne grains in the high carbon steel. In orcer to use the curve given in Plate 12, vroc proceed as follows- Determine the area of pearlite at tnree different points on the surface of the metal. Two values for the percent of carbon will be found for each percent of stru& ctural constituents. This will give sx values in all. Take the average of tne six. If the percent of vearlite runs over 595, count the other constituent and subtract from 1250, or whatever tne total area of the drawing ha»pens to be. Now the reverse of what has been given was tried. The cardon content of several senvles was determined in this manner, and the result checked by the combustion netnod. The results are viven in table 4. Page 49. Each of tne saanles will be taken un in detail. eta > em ie ct te tu GENE DIETZOEN CO. CHICAGOWEW YORK NO. 350 _ Oe od - ~ at ~ - . ~ “Na . wy “ toe - ‘ Me ‘ ‘ i t ‘ ‘ ° ‘ . - . at . an , . 1 - f, ‘ ‘ . . . . ~~ ‘ ‘ x ~ . 4 . . ! > N ~ - - . . , a . a > * , bo, é . . ‘ . ° 2 ON ‘ tie Teel ~ ~ ‘ eoNty ved TA Ue ™N *, . a. ‘ . wet i, - SNA “NA . a ees . a 4 Ma Os fos “hs te me San. be ‘ } aN 5 ~ AN “ENON ’ ‘ $l 4 . Ct en ne 1 SNR ae NA VN. ." as . oe ws wo, Mia " nN _ ‘ 8 . ‘\ ‘ + \ ‘ + 7 a . ° Moy o ®. g. . Um a . .. . ® . ‘ . oA . aw a wae ee ee - -- - +e wee ee fee ee ee ee mr meme em mee ee eee as eee ee wee 5 . . LL. . cee ee ml we eee oY . ~, " ¥ . ’ eo oe ¥ Lae xa wd+ . “ . i : a ve Low carbon Steel, about 0.2 % X 200 Heated to 1700 F, and cooled in the furnace, Medium Carbon steel, about 0.5 %. J 170 Heated to 1700 F, cooled in the furnace 48 Eutectoid Steel, about 0.88 % Cc, X 150 Heated to 1700 F, cooled in‘ the Furnace High Carbon Steel, about 1.2 %, X 150 Heated to 1900 F, cooled in the furnace. 49 TASLE IV Sample Heated Area of Area of % P % C % C bifferenee No, to Circle P Min. MAX.Ave. Bele? 1709 1259 37630 26 27 S27 26 eg 90 Be1-2 1722 8 1250 367 29 25.26 Be1l-3 1700 159 185 15 14 16 Aree on ede of seugole BaJ-1 1520 1250 22) 28. 624 .25 SAME AS pB-! 4 . 02 Ban 2 TX 125) 545 a? 023 625 Ba5-p VWJOQ a PD 14 13. 16 frea on ecie of stiaole Cx1-1 #1729 1250 692 55 47 .48 .48 EFS 8 12 C-1-2 1700 1259 541 Ady 238 1349 C-1-3 17200 1250 552 Ad 37 .29 Sele1 61790 1250 168 13 14-415 S-1-2 1790 1250 1620 1513-15 1H S-1-5 1750 1250 166 13 13-415 ATe4-1 1720 1250 4o7 34 = 28 1350 AT#1-2 1790 129) 335 51 27 .28 .27) Bdeow of cnse nercaened smiaole Bun. osced to AT=1=% 1700 1250 495 32 226° 29 be 1.2 50 50 Case (1) Samole B The sanmnle wes heated to 1700 F and cooled in the furnace for 24 hours. The s»ecimen was then sawed in two and tne tnterior examined, The structure is shown in Plate 6, Page 5] Figures B-1-1 end B-1!-2, were portions of the surface, taken on the enterior of the surface, and , and these results cneck the combustion determination very closely. In Figure B-1-4, we have a detersination which does not check, This drawing was made on the very edge of the sample and shows tnat the prolonged neating an an oxidizing atmosphere, caused a decarburization of the exterior of the sample. Case (2) Samnle B This was off the same bar as the above sample, but as will be seen on tiie data sheet, the sample was only heated to 1DOOF instead of 1700 F. In this case the crystaline structure is not as well defined, the crystals not naving had as much time to grow, and are tnerefore somewhat sualler. In the case of B-$-$,and B-3-2, the results check pretty well. Good enough for commercial analysis at least, Figure B-3-3, again shows the effect of prolonged heating on the carbon content. Case (3) Samnle C This sample was taken from the forze shop stock from some :aterial which had been giving trouble. It was su sunnosed to be about 0.6 % C. Some of the bars would harden allright, others would not. Some of the bars seemed to harden better in the center than on the ends. The sanple tested was taken from the end of one of the bars. Figure C-1-2 and C-1-%, show the true content of the bar, C-1-1 aan i ; } TT + wile - J - ‘ ‘ ‘ s ' AUGENE DIETZOEN co. cHICAcO-nEWVORK NO, 350 a of” it i ella aed i el eee LP, cain ah mats Be - » . . 2 3 . . a ? . ? 7 2 . : - Ps — Be asi ‘ : iS . eee Ee, : « $ < an TAL rod e 3 av Pag or Ss +% ” Y eo e a f : = ae * . “ 3 2 ri 2 2 : : 4 a 2 f : a i 5g . 7 “ - Y . “ « Ww - 2 at 3 a Ra 1 4 ¥ - FA ; a? Z r* , , ~ 2 * we “ >is . : ce : ws - c 53 a “ o “a a & ~ ‘ ~ J . a a % e% a e et r ‘ ; 1 Z i A « e % < , ; Bs Z 5 < ‘ > be 4 io 36 4 1 zs z S ‘ e : i t ~ : ¢ Pe % i 3 Sng . : a4 i pe gives a much nigner percentage tnan the other two. This Bar:ple was taxen to snow tie effect of overetchifg, and shows that e mistake in this direction can be made very easily. The ot:er crawinjgs check the carbon content as determined by the combustion method, C-1-1 and C-1-2~2 ere found on Plate 9, Page 4i¢, Case (4) Sanple 8 This sam.le came from the Gier Pressed Steel Co. After prover treetment, the drawinvs of the semnole were made and are given on Plate 13, Page $5, Here care was used in all three ereas exrmined to get characteristic portions of the surface, The results obteined in Fi;ures S-1-1, S-1-2, S-1-%, check very closely with the carbon content found by the combustion method. In this particular test, The actual time consu..ed in the overetion. after the sannle was taken from the furnace was 18 minutes. While the time teken for the combustion was 20 minutes. This shows that the time consumed is just about the seme for either method. Case (5) Semple AT This saunle came from the Feo Notor Co. It was teken on the ecge of a paece of cese hardened material. The case was sunnosecd to be about 1.2 % C, but it would not harden when quenched. On examination, as will be seen from Figures AT-1-1, AT-1-2, AT -1-3, Plate 13, Page 53, the carbon content of the case did not exceed 0.27 %. It wes found that the trouble was cue to faulty pyrometers, and that the temper- ature was not high enough. The semple suggested to the author that here a case mignt vresent it self, where the method of determining the D of C, might be of value. It is impossible NeGescace Fa ORF NG ble a . “/ « « ‘ ¢ ' woe > rc ! ~ . . « ‘ , oy ~S - . “1 . 4 fo of 4, 7. tr "¢ . vt ‘ ‘ . t “+ = 44 cor . ec - a ye te le toe . " ao ow e ‘ vif \. Ne er? : ‘ ON 4 aan . . ‘ - --- - 7 lan . oc e @ fw a ' \ ’ as ’ @ ae Sm ’ ' neon y - ~ 8 o™ ™ ofan i+y% ” s ot. Ne. ‘ os crt “ny ~*~ f a 54 scanple of low carbon steel showing the effect of different rates of cooling on the structure of the specimen, Saaple as received X 170 =’ 1 7 X 150 Quenched in water X 150 22 to determine the carbon content of the case by the combus- tion method. for if it is only 1/16 of and inch deep, we could not be sure that our filings: did not have some of the softer material. Yet if this method worked, the Carbon content could be determined at any depth in the case with eeseand accuracy. Consequently 4 specimens of case hardened material were obtained, these being hereafter designated as samples AT,HT,HS,HR. Sample AT has already been described, Sample HR, was foundto be cased to 0.52 %C. The other two were found to run to eutectoid composition. On Page 56 and 57 are shown photographs of these different svecimens. Plate 14, Page 58, gives a drawing of a section of sample HT. This drawing is a good deal larger than the image thrown upon the screen, and was obtained by care= fully moving the paper and the paéce in unison. Altho this requires very careful work, and takes a little experience, the results justy the effort. Here the specimen was magnified 160 ) and onthe drawing the actual depth of case has been scaled off. It will be seen that the eutectoid composition extends in 0.0103 ". The chart at the bottom of the plate gives the carbon content for each half inch of depth on the drawing or for eash 0.0031" of actual metal. Plate 16, Page 59, shows the case of sample *$ HS-1-1, Great care was used in meking the drewing, and the case had been so put in, that we might heve a gradual 56 Sauple AT X 50 Sample AT X 100 Slowly cooled from 1700 F Outside of case Sample HS X 50 Sample HT X 50 Slowly cooled from 1700 F Slowly cooled from 1700 F. 2URESE FT TIOEN CG CUCARS FEM TORE NO 350 » es a. 3 ses ~~ eek AN Bu inyt ee Ae Ca x yo en- eee -_—_< wee ee ef ee et ey ts eee 2a et pt - nee pa ye se we ’ ’ 1 . t $ ( oe ee eee HI are ae = f : “a 7 mo a A : Pe Lh wowace tase. ee ' a, 5, Seer a “a esis SE bak oer Shoes A ‘ : x 4 ela ; : net) ee + i Ge x aga a“ an og Si gsdhe = Reh SoS Lat = a9 cr. ae Ge 5) Se Mees ent She ' ae ny re a ~ ae SS = oak. SoA Y 48 ¥ - Zz “a % i a ; } ae ' en tt ty bm & oO 27 nk . * wo - bo we og wed “4 Sy Aaa aay a4" ee ee = ee oe ee + ne ee ne ee ee eee = eg + te. ee ne i 1 a4 - x “a * A bef CE Hot we al >- > 60 increase in tne vercent of carbon from the center out. This is also siown in sample JR, nere we again have the effect of cecerturizing action endon firet examin ation it avpeered as if the exterior of the case might run as high as 1.4 %C,. But section i! anc O only had pearlitic sreas of 529 and 443 out of GOC. This would have mede the carbon content run up avove the limit for steel. Yerit . looked as though a very hirh cese hac been obtained, This tyve of exeaninstion sives one a very good clue ab to what hes harnened to the rterte, an wet or the meat to which the rece was carrie? with tore curburizin-: anterial used was oro der, .-. sak 7 4 ’ righ carbon steel, a od The last ssandle tried was a 1 owas supposed to de of sutectoid composition. wile Nowever tho totel arca of pearlite was below 199 ™, and conpideraule cementite snowed uo, This gave anaverace nnaligis for the eee of J6 % vearlite, or 1.2 3 0. The crawings for this sveciuwen will »e found on Plate 17, Tase €2, Figures (U-1-1,'-1-2- "U-1-3. Tall ablee 5 and 6, give the results for saaples HR 5 : : hy om and "5, These will be found on veses ut and ©}. PL OEN® DF ZGEN CO CCAod HEM rom NO 350 * L ~ 1 1 ' ’ ‘ ‘ i . ' ' , ' : \ ; ' { t ‘i ‘ * : : ei tae oe . 2 Sete ‘ og ' ‘ ‘ 3 t h ‘ ‘ | | i ‘ ' f 7 ! i r : i : : 1 ' ; ‘ 4 | 2 ' s , ’ } ' ‘ 7 7 | 1 ’ ' iene aleeieetdnadiitesieatnth eiematedntamentanallt aiianetiadiadatned neterieteaeetiaen tee ssc eee t = i _ : : 7 ' ' i 3 : 1 , ‘ > ; ; ! ; ; ! ‘ $ . e ’ ‘ . : — ae eg Rm th er - Q- +e £ -we 1 Spee wee mee ee ' - | : ee Se ae ae oe i | if) 4 ; “ > ‘ ‘ i ' - eet ee ee VR pate s (¢ re ae —- ee ee ” uf cn t ’ Te nS mi f oO — i ahaSd se aS 2 “OSA SSN 2 or = Zs : & e ' 1 ! Wes Tey: 2 . £ a ‘ a, © at ‘ . ‘ : ‘ x ‘ 4 ‘ i ' SP, : ’ 3 i ' bs ae : 1 ‘ 1 a + e ‘ t Sah) sh Stim) S preyed -Setengdsases” Saiietesmiecaewseas Sisk ea Gece od de. eae 2 ie bs } ' 1 . . ¥ 1 . : ‘ 1 ‘ ‘ ' . ' 1 t ' ' i i ‘ » ’ ’ ‘ . ' { . +” . ‘ ace: ihe . > « ’ H } : e . re . = ‘ : ' ‘ ae + ' ; , ‘ i ; ! ' ¢ 1 : 1 4 = 1 ‘ ‘ siete sie pte Peewee matte Ae paces t Secession, cal hhc ae as Sak eae, ade rato a oa a ae * = mbeen. 1a POrNe - ‘ ETZGEN CG CHICA: O-NEW YORK NO 350 : } ' 5 \ 1 ; ‘ ; \ ‘ ' . : 1 ; ‘ j ¥ > . - -- es eee - 4 - ‘ . . . - : 7 3 Mr cree > ot, : : ; ' ss | i ' ‘ 1 ‘ ; ‘ ¢ 1 ' 1 . | 1 1 . ; i ‘ ‘ ; : : ' ! ; S a . * ; ; | i : : , ; t : : \ : 1 i . _ ee — . 1 erage ected pean eae, sarees eased end eee ee eg ee ee eee Ce ee ap a Tee SSeareawie esa pa ih ess = (wiles re ee * i shies eS Si. Setsee Se i 4 | an: | , 7 . 7 | : | ' ! i é ; ' | | | | 3 i ; | ‘ ' £ ‘ . \ : ' ; GQ. ise: ower al whup tt. 2 ims ius 4 ‘ : ee pe oe ies a4 = Ae A S be) * ey : i t 5 t ’ . t ‘ | 1 ; ‘ { | t m : : . ) . ° “ 1 ‘ : a fe | . ‘ | { a : EGGaibeewiicisetar jeaberGa simaes en Loan@nuaes antecet 3 reins Soe od) (Gee veaeeeni ee scitiaecees eer sabe eben: «al lee : wale - 1 me greeters ee = ! f ‘ ' : a nt : ' ‘ ‘ ; i> soos ‘ a { 5 a P . ’ 4 ’ . < 5 i : 7 ; 5 ' % ‘ : i ; a Twa ae . . eS ” -. z | ; . { an ‘ 1 i ! : , a8 | ' r i rae ‘ - > - ee me te . fc; : i : “7 ; . : a ee 3 : A os : ; *) oo Li 4 i 2S 4 A i a3 : : 7 + 1 peta ade fie a eae ns Coe b&b i i 1 ' | : / ' | : S 3 g : : t “te at . oy S. on if ‘ re K 4 / H 1 : ‘ ; % 4 é : : a ax | : : : ; es ' \ be i 3 : fk: Mramsteades” (amines PSS & Ghee’ Opn Seis We Seam ys Scud cheese wes Stem Winaesae & aa = Sees it SS “me. : . ne ; a : 3 , | ‘ ' : i j ' 2 ’ : : ; i u 35 i e i ; te ‘ "4 : : x a ‘ 4) doce ae heh irae ar . noe Ps ate Oy se e onely ve i - 7 Sy p ; : ; 3 " ral ‘ 4 ' ; a ; ; c : A ; 3 : i ; i ' : 4 ; 4 : : : ; ‘. i ~ ' . ‘ ; ‘ S652 M ko gene oe eh. aI : - al sap Aas ¢ & ingides " mene swe ie ede 4 so see ihe cee eee oe eee wy Sele a i ! ‘t i ae 1 “ > ‘ ‘ a3 ; ‘ ow ; a me sais ig soe tickih (Sa Le pag 39 . ; 1 A 4 ‘ ? os : . ' : ! ‘ ey : , : ! ' : ' ‘ za ‘ mae — ae ————— a me — ~- - ee eh a ete ee ow nee eet eS ee —-ees oo = -_ ° > = * Section td TY a’ TALL Area or Penarlive 64 Arca of Sircle “ vo P 19 14 An Cc... ND XS ee ~~ 74 i . . ' ; : ‘ ae: : ' 1 ‘ ' ; ‘ : > ' t . 5 : ee ‘ ee . . + a ie oe Sb ae . . a . 7 2 ! 1 oe ' : ' 1 : 4 1 ae : 4 : : ' ' : a se 7 ie { i ; ' ‘ “i : ‘ a { : ‘ i 1 : : 2 4 54 ; { ‘ i ! ; : 7 / ' ‘ 1 . ' i . ‘ ¥ | SS. is ~ | ; ‘ | \ ; ‘ ' ‘ ‘ ' * ' : ' ‘ : ! ei ' ‘ i % | i } i r ; 5s cee dae eam ag ten esehe, “thuakitmaiica: so sieeeete lee kage ele Sr PG RUS Sty sek penW comes bnbiee Soi og ee eee oe cate Seok eet ENS Blames aon Bloe - 4° = ’ sha.) oe seri Tey achote 4 | k : a ~ i ‘ : 7 ' : x + S00 ae , ‘ ‘ : F 1 ' : : ss ’ -" : a : : : . \ ' os, Pe ee ee ee Ob eee rr . < : i Be st ; ‘ fe on oe . of ’ o a “9 bits - - Pd ’ t ' , . < : fo 2 ‘ ’ - pean >. «= A weg come wee = , i es ‘ «i! + ‘ as = cs H oF ' « a a s hg vic): Gebes i ' o , $ ‘ 1 St coer Se geem he ‘ = a 1 i . t : « + . : : o ; : 4 ‘ . : ? ' . ‘ a : . ‘ ‘ i Wis 3 8 Soe aaibug F Sixte 3 cLaae oy aor 13 x fi . a 4 : ' + . 7 ~ i . ; ‘ i 4 : rn i ‘ we : . ‘* e ‘ i. . om | ; ! i 4 : A ; : 4 : “A : % is + . , : . ‘ a es ‘e A te a oh. 9 I sat ah igh, GP ia Seas Sky fe) a beta eoSeeee> BES h“ qi Banana e = th oimbege iia, iegeres = Gece eS) od Pr = mi = i Je * ° as . on on it -.. - . ‘ ’ : o ; ! a ’ Z > ss “1 A ! ' , ‘ : : “ : i Eee A “ ae ‘ oe & : : ay i ‘ 4s ; aoe ' ss : a u Se : An * n 3 ‘ ie vs er ee is 4 4s - to: oy - . i re ‘ ts wae eae 7 -—— wee eee oe 4 ' -- =e a et ee wen eee eee me de ee ee 64 TAGUL Y . , - of pt Section Area of Area of 33 P “ C “Oo Mecrline Jircle Min, lax, Avera oe tJ BA EQ) 14 19 IES a oN -° < r D 152 me 2% 6200 22 22 tz ) Oo CU © XS: On XN © WN \ fo o>) \ G p29 650 64 oO, Mi Xl © Cy Ne H 412 60 JX Nf) J CD AN I tr [- . Sh ON © CD Co fo TN _y © ~J C3) XA J Co M 550 690 57 290 6992 9 ~ ) LS) —~d a " B29 690 27 730.75 © = WN CON €) © oJ oo CN iJ Sl Oy XN \ cnx XM 69 TABLE VI Sample HS Section Area of Area of % P 3 @ 20 Pearlite Section Min.-Nax, Average A 53 890 7 080 105 Oo B 63 80.) & 090 .110 215 C 95 800 12 .120 . 135 13 D 132 890 17 6155 165 16 E 165 aad 21 2190 .205 L229 F S44 8090 24 210 .215 Jo G 201 800 25 »220 .230 24 H 273 G29 a4 6290 300 235 I 38 890 4a .360 379 37 K 374 &00 47 400 .410 ae L 417 890 52 AAD L450 AES M 430 B29 54, 460 .470 ‘I N AST G00 65 510 .520 82 66 Samples AT HS HT Showing cases of different carbon content. -—- ——_r— - Photograph showing tne effect of improper 7 polishing and etching of the specimen. 67 Conclusion- The author hones tnat by this work he has given a glimpse into a field of analytical work which at present is almost untrodden. The results obtaimed compare favorably witn those obtained by chemical means. In the case of material such as case hardened we can get results which it would be impossible to get by the combustion met}od. For tne combustion would give only the average carbon content, whicn of course would be useless, The entire work may be suaned up in e few brief peragraphs. We know that the amount of pearlite im a slowly cooled steel is proportio:.al to the carbon content, and as steel is an alloy of iron and carbon, whose cooling curves nave been accurately deter:nined, and als» as it is an alloy, the cooling of which can be easily controlled, it ia possible by proper heat treatuent to cause nearly complete seperation of the ferrite and nearlite in hypo-eutectoid and the pearlite and cementite in hyver-eutectoid steel. This statement does not apply to alloy steels. Also by using prover magnification, these differnet constituents may be fatrrly well traced off and measured. The error introduced is low and fairly constant, so that a correction curve ay be plotted, which will give results that check the carbon determinations ,by the combustion method very closely. 68 In the range from 0.79 to 0.90 4 C, it will be noted that tne constituent of which there is very little present can not be calculated, so that within this range our error amounts to 0.06 ‘4. However tnis gives results as close as most snecifications read within this range. On the wnole a mistake is less likely by this method, for here we bring out vhysical structure, and thus the chemical constituents, while a chemical analysis calls for the commolete destruction of tne sa..ple, and if some constant error should creep in, it is likely that it would not be detected, In order to got good results, the following points should be observed:¢ 41) - The sneciimen should be heated to at least 1700 F, and slowly cooled in the furnace. Steels above 1.0 %, can be heated to 1990 F, witn better results. (2) - The snecimen must be properly polished and etched. For slowly cooled steels, a 5 % 0% in CoHsOH, fives good results, (3) —~ The different areas traced must be repre- sentative of the whole vitece, and not of a varticular voint, unless we wish to examine that particular area, (4) A magnification of between 122 and 290 X high enough for a properly treated sample. 69 (5) - The tracing and measuring of tne constituents must be carefully done, and the correction curve used to determine the percent of carbon- Count the area of the constituent which is less than 50 %. All the negatives used in this work in the making of tne photogr:ohs are on file in the author's labermtory at M.A C. Prefor:aed in the Metallurgical Laboratory at Tne Michigan Agricultural College May 1919,