<8) oe] ee) THE WATSON NEST THESIS A STUDY OF THE 7:2ANSFORMATION POINT O" METAIS, A REPORT SUB.LITTED T0 THE PAGULTY OF TER MICHIGAN AGRICULTURE COLLEGE. BY CHARLES ERNLS? WATSON CANDIDATE FOR THE DB@GREE OF BACHELOR OF SCIENCE. JUNE I92T THESIS Acknowledgment is mace ta: W. G. Hiiderg for designing and constructing the furnace. H. he Publier, Asat. Prof. of Chemistry. 404037 The Tronsfermation Point of Metals his report was first started by Mr. Hilder’. The furnace was first designed and constructed by him. He however, (14 not have time to finish it as he wished. He managed to carry on one test with it which oame ous fairly goed but Be sould not heat 1% up to Righ enough temperature Because the heating coil] was plaeed too fag from the sanpie which was to be tested and cheerved. The mada problem that comes up in this experiment is te keep the metal from being @xidined while being heated wy ' - Sae furnaee ag constructed ie in the ferm ef a oylin- der about 7 3/4 inches in diameter and staniing about 5 inches high frou the table. There ts e cover to thie fur nace, with a hole bered thru the center and thru which the motal is obsexved with the miozoseope. This cover is Rollew and has an inlet and an outiet for water which is used for keeping the micrescope ceel and alse making i+ mere eomfartabie for the operator or the obsexves. The hole in the center ef the cover ia tapped and has a brase plug which is threaded and placed in thio sapped hele and may be wameved at will with a special wrench. This plug has a 3/4 inch hele drilled in it and there is a piece of selected mica piaced in this hole and cemented down with alundum cement. In the base ef the furnace there are @no holes driiled for the leads to the heating coil. The leads are, of course insulated from the casing of the furnace. The thermal couple comes inte the furnace -~2= thru a hole in the center of the bottom ef the furnace. “his hole is about an inch in diameter and is threaded and-fitted with an inch plug. This plug is drilled with two heles about 3/8 inch in diameter. These holes are for the thermal couple. The thermal couple projected up thru this plug and inte a wrought igen atand which holds the sample. This stand ‘was at first only supperted by the thermal couple and what little packing happened to be under it. This was one ef the faults ef the furnace, %e give goed resulta the sample ‘should be about an eighth ef an inch from the mica. =| This position aleo protects the miozoscope from the heat. In the way that the furnaes was iret built it was un handy to remeve the sample from the stand as it would get the stand out of pesition and possibly displace it 80 that the sample would be more than an eighth of an inch below the mica. Zhis would cause the glace ¢f the micrescope te become heated up and possibly melt the coment that holds the glass in place. Anosher fault in the first construction of the furnace was, that there were three holes drilled in the bottom for letting out the exygen. These holes were abouts 3/16 inoh in diameter and were much teo large as they let the oxygen in instead of letting i+ out. in the side ef the furnace neax the top was an inlet for nitrogen m % = whieh is te replace the exygen and thus keep the piece from @xidising, The cever to the furnace was fitted fairly close to the tep af the furnace but not quite clese eneughe An oiled gasket wae needed te make the top air tight. Before Z could comdiuct any test or experiment on the furnace I had to everecome these faults and ree arzange the furnace. The holes in the bettom were fixst plugged up and then 7 werked on the construction Of a suitable heating go1) which would bring the heat Clese enough %o the sample. The e244 heating coiid was about two inches in diameter on the inside. With this coil only about 1000 decrease Fahrenheit could be reached. The coil should give a temperature as high as 1800 de- gress. The heabing element in the new coil was made of nievem wire, 20 gage. i tried two types of coils. The firet one was mace by winding this wire om an eighth inch mandrel, About twenty feet of the wire was wound in this way. This eoii was then wound around the stand aa olese to the sample aa possible and held in place by alundum cement. This e011 would not werk because of short circuits which were almost impescible 40 stop. The next e012 made was ef wire wound on a 3/4 inoh mandrel ami then placed inside of a straight porselain orucible, the bottom of which had been sawed off. The inside diameter of this wag about an inch. Qnme coil x & a was placed inside of the arwible and the other ons Was wound about the outside. Both ef these coila were held in place with alundum cement. 1% was found that this coil worked alright, When it was tested it wae found that 1700 degyees Fahrenheit could easily be reached with out the insulation aroumd the coi) and with the opver ef the furnace off. A resistance of about 65 feet of the same wire was wound, and was used to keep the temperature from yunning up too fast and burning out the heating coil. Another plug was made to fit into the hole above the plug (A) thru whieh the thermal couple jeads run. A hole was drilled thru the bottom for the couple. In the top of this plug ware placed two dowel pins which fitted imto she sample stand. These dowel pine held the sample stand rigid and in place so that the sample can easily be examined by the micre- scope. Tho sampha tteclf was a piece of steel about 3/8 inch in diameter and about 1 2/4 inches long. ‘Thewe ts a hole about 2 inch deep drilled in one end fer the thermal, couple. The other end of the sample is polished to be examined. The thermal couple was run up thru the pluge and into place ami held there with alundus cement. This cement also helped to make the furnace air tight around the eouple where it left the furnace.  La , wosyopn hg uMig a20UdNY 0 M I!/f\ PIC ' t in| 7 = Ys - C1 EEL,  o § = Next, the heating coil was set on the stand and the leads to it were attached to the brass screws pasa= ing thru the bottem ef the furnace. ‘The furnace — around this coli was packed with magnesia to hold the heat in. About the o012 was placed some fine carbon for taking up some of the oxygen that might otherwise go tovarde oxidizing the sampie. An oiled gaske§ was made for the top of the furnace and placed on the top end then the cover of the furnace was sorewed inte place, meking an almost air-tight conneotion, Before ary test could be run on the furnsce the Brown Heat Meter had to be calibrated against that ther~ med couple, A Hoskins pyrometer was used ap a standards Both pyrometore were connected to the sume couple with sa double pole double threw switch. Reading were taken on the pyrometers at the same time and then a curve veg plotted. It was found that the Brown Heat Meter read about 150 degrees low. By the curve the teuperature could be found from the Brewn reading. The heat meter wae thémeamneeted up with the couple as chewn in the Wiring diagrams ‘fhe tapped plug (C) wae roxnowed from the cover and the sample of metal to be examined was slipped inte place in the stand and the cover then sorewed downs Bafore putting this sample into the furnuce, it was @6e Calibration of Brown Heat Meter. Date; ; “ oe ee eee CC oc Of C8 SF 2e ce OF OF FH FF HF FH OF ©F © OH EF Oe we Oe ©O Om ©O ©6 oe ©e FO fe Of OF Ge be 68 Oe ©e £6 ©8 oe oe O86 we ef se es ce ce 4 Et Of © © F Ot BI WI OF OF OF OC} BIO Of wi © mi St et Et St R Bl 3; Si gi Sy St Et St St Si Bi SH gt gS: Si Sto ry St St Rs oe t a tie or P2hae safes SF fee Sees eofee Sefer Ce hee Sefer SF fee 88 hen cofee cofer coffer cof" fee coffee coffee coffee cofee eofee 4 Average Readings Hoskins 20 310 400 530 600 | 700 750 00 00 960 960 000 1050 TI00 150 1200 1250 33 1300 350 1400 : 1450 1500 1540 . . * ? sae * . . . 7 ¢ . 3 $ 2 $ 2 joo 82 cofoe SF G oe GF °° Go ve FJ © Ge *e Ge ©* Ge oF Ge oe Ge oe GF Ff Ge we ge He Ge oe ge ae Ge & ei mtOtro +o ° SISio!ioiotBiniF isis SiSiSiStSiB SSS ZS ssi ais : F Spey ie rorcgr ey cect tate tetetere tote tt tt 210 2 2ID!igietoc $ F18is APSRIBIS SB SiS iBisiSiSiSiStnisiSiSiBigy y je Of oo jo 92 Qe ee og ef og eo of we © of eg of Resistance amen 7 8 72 aL aL of Furnace Orawn by CE. LR Aek ae =F « etched with nitris doid after polishing, ‘The water was turned on so that 4¢ xan thru the cower of the furnece in the manner indicated in the figure. The microscope wae set over the sample and focused and Lighted. Tha resistance wag connected in ag shown in the wiring diagvem and the apparatus was then ready for conducting the fiiet test. No nitrogen of ether gas wae ueed to keep the metal from oxidizing. The — current was turned om and the sample watched thru the microscope. Nothing happened until about 700 degrees ona then the pigas began gradually so darken ever as if oxidized. the grain structure entirely disappeared and nething could be agen on the surface of the metal. Zt was easily seen that thie method would not werk. In the next test run on the furn:ce, a low carbon atecl was used. In addito to this a hole was drilied in the side of the furnace and a tank of nitrogen was conneoted fo the furnace and rua into it thru this hele. The teat} was again repeated end with suagh better xesults og the metal did not start to oxidise $421 about 800 degrees. At thie point ther@ was some cext of a choage in the motel. Tha picce oy scanple appeared to oxidise ovey entirely at ebout $00 degrece. At &4O decrees the structure wag beck in sight egain and was very moh mere in sight then 1% was originally. The piace oxidized at » § » aheut $50 degroes without any chenge being noticeable. The next test was run the same way except thet a sHeAL hole aout cn eighth of en inch in diameter wag vxdiled in the bottom to let out the air thet was al~ ready in the furnace. Witrogen is slightly li:hter in weighs than oxygen, therefore it would be almost pure nitrogen at the top of the furnace while the oxygen would gradually work out the bettom. This would loave only & small percart ef oxygen in the furnece te oxidise the metal. This teat oame out nearly the same as the othor one before. The metal appeared to oxidise at 800 degres@ and then came back into sight again at 850 degrees. The metal exidiged at about 1000 degrees this time and still there was not any change to be seen in the sample. In the third test xrun on the furnace the hele in the bottom ef the furncce was plugged up, ami then by meana of a Y tube, and oil-sealed aixhpup vas atteohed to the furnaces The air was at first exheusted es far 20 possible and then the mitrogen was run into the furnace The resulting mixuure of nitrogen and air was then pumped out of the furnace snd then more nitrogen we Jet ine This wos repeated several times before the teat was started and in this wey nearly all the oxygen was tien out amd replaced with nitrogen. The current vag then turned on and the sample watahed agnine -§- Ze was found that the riret change took place about 790 instead ef 800 degrees as in the others. The structure disappeared again aad when + cane back inte sight there was a darker redish coler to it. There Was no change 6411 nearly 1200 and thon a very slow change started. Tt was se slow that 44 wae hardly noticeabls, but fast enough to know that there was something going on in the sample. The ferrite or the lighter mailemed structure of the sample seomed to be getting amaller while the darker strusture oF the pearlite seamed to be cotting larger all the time. This change scatinued t4111 about 1300 degrees and then there did not seem to be any more chance. In order to sae wheat happened when the piece was cooled, the current vas turned off. Hothing was scen because the metal inmmed= Zately began to oxidigo, ‘This wae probably because of the nitrogen being cirauloted while the sample woe being heated. This nitrogen would tend to for & sort af « film ecout the senple which would keep the oxygen away from 43. Ap goon as the heat was teken away the movee ment of nitrogen would stop and the 2iim be broken wu and let the oxygen in the furnass to the matal and thus oxidise it, In preparation for the next teat a piece cf lew carbon steel was obtained and turned into a standard yeet bar. This was pulled with a lead of 10,000 pounds. a ad ae - 4 se A ploture of the patoma used to make the furnace end also the core box used to make the core end the core thet is used in the mking of the cover to the furnace. 7h The purpese of this is te get a piece of metal that has been stzensed and sae the effect ef heating on it. Zt ie eaid that a piece of metal that has been streased has a large grain growth at low temperatures. Tf is alee said that low carbon steel will act oxidise ae genily an dees the higher carbon stecig. Some very queer things happened in this test. The piece did not exactly oxidise at the temperature the ethers have deen doing, but it 414 change goler. At about 750 degrees the gurface ef the metal to the eye appeared to be turned & deep red color, Thsm the micrescope the eumlace of the matali darkened slightly with a redish tings. At about 760 degrece the surface ef the metal began to tum te a biw. in the micrescope, the binkah toler was notise- able. The ight persion between the osyatala turned biw and had the appearance of water. Tho darker portions dooked like little islands in tue waters, Qn cxhausting — the alz the metal turned back to its original color and semained there until the metal became red hot and then the metal essmed a rediah colar. At 1200 degrees and a little evox there wae another change which 400k place very slowly. The surface ef the sanple ioaked vary much like little globals ef fat on water. The outlinca of the crystals wong still in eight and remained in sight $11] about 130° degrees where i oxidised over. The oxystals appeared to be getting a little Jarger but they aid not grow as was expected. When the piece was taken = 12 « out of the furnace and polished and etched and then examined under a microscope it was found that the arystais had changed shape somewhat and were a littie Larger es qn the segond test that was run on this same piece of metal nearly the same results were obtained. At about 1100 degrees another strange change took place, The cryaetals did not change but there was another change in. the coler ef the sample. The surface of the metal | Leoked very much as though a drop of water had been dropped upon it and 1% flewed around ameng the crystals, There Was & Dluish coler which ran around amoung the crystals very mach the same as water would do. This kept up @4hi | the entire surface of the steel was of thie colez. This blue coler was fringed with red and purple. Nothing further was observed because at this peing the mica cracked and spoiled the view of the sample. the next test was again run on the piece ef uedium garbon steel. This piece again appeared to oxidise af 750 degrees and then came back into sight. Where the metal firat appeared white under the microscope it new appears blue and the surface of the netal was blue te the eye alse. At about 850 degrees, the metal cam back to its original coler again and remained there +111 4% oxidised at about 1350 degrees. dust before it did oxidise there was a slow change in the sine ef the exystals. » 13 @ Just befere the cutlines of the crystals began to disappear it was sasily noticed that the arystals were growing larger. At this point the metal began to oxidize and nothing mere could be seen of the change, The metal was polished and etched when 1% was 000) ent then examined unfer a microscop#:in oxrdex te make sure that there had been a change. %1 was found that the crystals had very nearly doubled in gjse. They were so lerge that they could be distinguished with the eye. This was the last of the teste that I ran on the two kinds of metals. Zn conclusion I will say that I think better results could have been obtained if the furncce could have been made more nearly aix tight. ‘The air pump needs to be connected to the furnace with metal connections. Tf this had been done a higher vactmm gould have been obtained. Another thing that was a source of trouble was the piece of mica which waa over the sample. JZ too mach air was exhausted from the furnace, the mica would break on account of the air pressure on the outside. Aise the mica would sometines orack and spoil the view of the sample when a high temperature was reached. A good quality of mioa has to be used.