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' E 5‘ .‘f ' RM x» F: T \ T't ‘ AN INVESTIGATION OF THE EFFECT OF ANNEALING TEIPERATURES ON COLD—DRAWN STEEL An Investigation of the Effect of Annealing Temperatures on Cold-Drawn Steel Thesis Submitted to the Faculty of Michigan State College In Partial Fulfillment of the Requirements for a Degree of master of Science , '1! /T I. I" \ Roy Al Gezelius M August 1, 1930 THESIS ACKNOV LEDGHENTS The writer wishes to eXpress his appreciation to Prof. H. E. Publow, under whose direction this investigation was carried out, for his assistance and suggestions. He also wishes to eXpress his appreciation to Albert Schweizes and Milton H. Grams of the Motor Wheel Corporation for their assistance in obtaining material and physical tests. 86331 Introduction .Standardization of steel for cold working, deep-drawing, is a field which has as yet received very little attention from the research workers. It is a field which, if properly investi- gated, could do a great deal toward cheaper and better production of cold—drawn articles. There are at present no Specifications for steels used for deep—drawing purposes with the exception of chemical analyses within certain limits. It appears that Specifications of this kind are not sufficient to insure a uniform product or a steel which will withstand the severe strains to which cold drawn steels are subjected. It has been found by commercial concerns that cold—drawing steels of very nearly identical chemical anal- yses have, under the same drawing conditions, reacted quite differently. As this is the case, it is logical to assume that the treatment given to the steel before drawing has a marked effect upon the results obtained. Working upon this assumption, the writer has endeavored to conduct a series of eXperiments upon cold-drawn steel and upon hot—rolled cold-drawing stock to determine the effect of annealing temperatures upon the reaction of such steels to cold work. As this investigation was approached from two angles, the change in hardness and the change in ductility, it would be best to review a few of the theories presented to account for harden- ing. Jeffries and Archer present the following theory: "Hardness - 2 _ is resistance to permanentdsformation. Metals fail under stress— es much below their ultimate strength because they are built up of crystals. Decreasing the size of these crystals will increase the hardness." Katora Honda attributes hardness to two factors; first, "forces acting between molecules of the substance" and second, "the crystalline structure of the metal". He then goes on to add that "for a given substance having a definite molecular force its hardness increases with the fineness and strained state of the structure." W. Geiss and Van Liempt declare that there are "two theo- ries as to the mechanism of transformation of metals worked in the cold: 1st (Due to Tamman) That crystals glide over each other in certain characteristic gliding planes. 2nd (Due to Czochrolski) That the actual shape of the lattice is distorted. Lately these theories have merged to a great extent". In the J. Inst. Hetals (1925) H. J. Angus and P. F. Summers tell of an experiment on annealing pieces cold-rolled CQpper and bronze. "These were annealed at various temperatures up to 10000 ........... In coarse grained cOpper and bronze a large decrease in hardness results from annealing at 300°, a small increase is obtained after annealing at 1500 - 2000." The work which the writer has conducted will in some in- stances bear out and in others contradict the theory given above. It has been impossible, in the time allowed, to complete an in- - 3 _ vestigation of this type. The writer therefore sets forth the results obtained and the conclusions made therefrom as mere hy- potheses which may, upon further investigation, prove to be erron— eous. It is hOped, however, that a more intensive study of the subject will bear out these experiments and lead to some concrete specifications for cold—drawing steels. _ h _ Experimental Work I A cold-drawn brake-drum, which had fractured upon drawing, was obtained and a microscopical investigation made to determine the cause of breakage. It appeared that the fracture was due to poor stock, as slug inclusions were found. (Figs. 1 and 2) Pieces of this same drum were then annealed for one—half hour at different temperatures, slow—cooled in the furnace and tested upon an Emerson-Southworth Hydraulic Ductility Machine. A marked increase in the amount of deflection at the maximum load shown by the heat—treated pieces as compared with the "as received" pieces led to further investigation along this line. Four cold-drawn brake drums were selected at random from commercial stock at intervals of approximately two weeks. The braking surface of each drum, which had hardened during the cold— drawing, was removed. This was straightened slowly in a vice to eliminate as much further straining as possible and then cut into test pieces. The Rockwell hardness of each piece was noted and the pieces then annealed at temperatures varying from lOOOOF. to to 19500F. being slow cooled in the furnace. The same furnace, automatically controlled, was used throughout all of the experi- mental work to insure a uniform treatment. After the annealing process the Rockwell hardness was again noted and the pieces then tested for ductility in the Emerson — Southworth machine. In all tests on this machine readings were taken of the maximum load and the deflection, in inches at the maximum load. r9.» - I ;- --.. .: - .I". r .' "‘33:“ ”2-. soft 35“}141" .x" 7 ,_ V _ 5.1"“ . . ' A --4, . :1 Eros taro . ' r. ,1" .'. .~ .. -‘;--1 1' 11,;3. . *kfipf‘wl >~_,-~1;-\.-; ‘..:' "" ”*051? V I Anew ") .A ‘F 'Jl- ~Py f~'a" .- . - J. I. . " - .3 ¢ T) ‘ r ’ ' q .— J . - __. .4 "‘V A "l ..4. Ira] 1'- I \_~ .[ J L. (. qr... L’- . q l" {5710 \ J erudosii or _ 5 - The data obtained by the ductility tests can only be used as an indication of what would happen in actual practice, as the drawing conditions are not the same. In commercial drawing, the steel is pressed between two steel dies to insure the desired shape. In the ductility machine the steel is forced thru a cir— cular hole by a steel ball. 'There is no die above the steel to hold it to any Specified shape. A diagram of the drawing con- ditions found is shown in Fig.3. A microsc0pical investigation was made of the unstrained portions of each piece to determine if there was any relation between the grain size and the hardness or ductility. There appeared to be no difference in micro-structure with the excep- tion of some grain growth at the higher temperatures. (Fig. h) There was, however, no correlation between the grain size and the hardness or ductility. An investigation of the condition of the pearlite was then made at higher magnifications._ Some small differences in coarseness were found but nothing that could be correlated with the change in hardness or ductility. (Figs. 5 - 16). hacrographs taken of the pieces, after drawing, show a comparison as to the depth of draw before breakage at different annealing temperatures. (Figs. 17 - 2M) It should be noticed that the portions under strain, above the ball, show black strain-lines upon etching with sulphuric acid. A Rockwell test of this portion showed an increase in hardness back to the original hardness. FIG. :5 D1egrem.ehowin¢ a portion of the Emeraon- Southworth Ductility Mlchine . t L 1’ 1.» . . ueed ifi‘ébtfifning dataIfor the deflection 6 .31? 9d: lo noilroq s aniwoda msrasid safflosi {JIIIJOUG dirowituoa -noatsmfl aaiiueileh ed: to} sish gwinisido mi been .eevruo . Diagram of a Portion of the Ductility'lachine. Deflection - Indicator Upper clamp Upper clamp W . ¥ lower clamp . ; Iowe 1‘ Ole: mp load Applied fin? A C I": .L V a ‘ : 1’ , f LII 'J C3 1 q Cb: ("x ‘. 1 $1” ("‘1 '7 Cf‘f‘I L \1\4 .oeH 8A “.2 a C) H PI of} is befsanus eeoiefi - I has helsoibni erstreqmeJ .eosxrui sit at befooo E 0691 .r.. . .. r. an 74,... A 3.3?) as! ..Fh kiwi-is ,I ... a! .. . «Wigwamwfiwp 4....” ..valx - .. . L. a . p . I II 'n - e.... . . ~‘ .-. 3‘ “a“.-ab' . flfi‘ 0*” .fi'” t ..A’ . 1303 i As Lee. 1100 F FIG. 5 ' Peices of brake drum annealed at temp- erature indicated for one-half hour and furnace cooled. XIOO “ 125g F 1150 r L 1200 F .“% “at J LLLE %* n r r-' 31 g? 1'». -qmei Js bsfsenns murb eisrd lo 393:3; ' \ C C I t {in has mood lfed—eno Iol bedroibni erudsre (kl A! Ikr a, ; .befooo eosnrul 3&1 f") r“ g a O C).- 3’3 H a- ‘w' A ‘5' ”non. "w”-..- -. . . V "‘3...- Q 1400 F . I ’i . 'O “I" \ _.’ ."‘| .{1’ 3r 0 FIG. 6 Continuation of-Fig. 5 . '\ ‘5. '4'“. h»-.. 1500 F 1600 F 00 u‘ L J *1 'e B.’ by"? .".L l. 'r“ 1113' 3 ‘ IO'HOIJsuniduoD .6. UiGI FIG. & FIG. 8 my Annealed at 1000 F 'As Recieved X 2000 {2% "-u ma"; «N‘ I "'57) ‘ ..- . ;_ 'r 0529‘- N3) \ Annfl饧u at ridd,F’ E\ .5 Blow%00019dvjy I ) «1’2000 ' , “ v - ’UL. " \a ‘r’ 2’ ' I 9 | . ' Slow-cooled x 2000 FIG. 10 . Annealed at 1150 F Slow-cooled X 2000 I" (N (a 1 ‘1" U a.) 'v a. A rr ,j k (“I1 4. V ‘J ?-v Lsfooo-wofa 0008 X I is hefsenaA .. bovoiosfl sA CCCG ’ e .217: CGII 3s befsenaA befooo-onE 0008 X E hefcoaewofa -\ fn 1‘ P 0~s* i 7‘: V‘v‘ can a: .OIE cam; is befsonaA befooo-wofa cos: '1 ‘L l)- f‘~ V GT nub £50.51? 03f is befsendA befooo—wofa 0003 a CI .91? 0031 is befnehnA befooo-wofa 0003 X O 3. +2- H ((52; .: l '1 . ° 3 rm. 1% a ..O 0.. a. Annealed eat-1500 F - ‘, I, Slow-cooled ‘ _X 2000 ‘3» .0 "i‘ “an 90-. 93' E 0501 is hefserxa 'befooo-woid QOOS X . n r- Y1 QUIZ}. r , ’ - rw ‘ DJVOIOOL 8A ,:.-. - .r- , .,rj , ‘ .‘v- r stride. astonfruoo-aoarema no oeissT A K CI .311 E OObI is befsenaA befooo-wofa enidosfl dJIowdduoE-nosism: no beiseT b X b X " ‘-~....‘..,..,.,-' f , \J-lI'JZ'i.LCJ.'&.L [‘0 j x E 038i is betsenaA befooo-wofa enidosfi djrowfitnoe-woaiemi n3 1 b X t 7‘ (.D M- {“0 L) *1‘ c... {a P] m l 9... 5 J‘- ‘. h I I '5 3.1.x) ' .l I 1:) 3 Z)!" I u'l‘ 15X FIG. 24 Comprieon of ductility tests madé"on Emerson180uthworth machine A: Bee. 1150 F 1850 F ‘ f _ r . ‘ "_ ’1‘ . " ~‘ ' r' _ “I- "-:v e v - .‘ r11 Stilllfefi‘. 2.1.1 19.1.01 ‘14“. “'IUE'Idfldi HI 1.3.1331 stoJ glifiioub lo noequmoO ‘ enidoei dJIowdicea-aoaiemd no spam ('1 (13:1 rUL U311: .34.- 8:; ' I. ..fi _ 5 - There was, however, no correlation between the grain size and the hardness or ductility. Data Brake Drum #1 Sample Epckwell Hardness A. R. 90 1000 . 89 1100 '69 1150 70 1200 71 1250 67 1300 63 1350 62 1000 65 Brake Drum #2 A. R. 63 1000 63 1100. 63 1150 60 1200 58 1250 5” 1300 60 luoo 63 1650 65 Def1.@ Max. in inches Load Kax. .190 .196 .3M2 .352 .385 .383 .372 .365 .385 .372 .366 8,250 8,300 Load #[_sq.in. -7- Brake Drum #3 Sample Rockwell Hardness Defl.@ Max. Max. Lo.‘ in inches £1 sq. ' A. a. 91 .240 7,600 1000 90 .250 6,350 1100 67 .360 10,700 1150 62 .310 11,200 1200 63 .320 11,100 1250 64 .369 12,600 1300 59 .355 12,000 1400 59 .366 10,600 1500 65 .360 11,700 1600 69 .350 11,950 1650 62 .365 12,100 1950 65 .205 u,9oo Brake Drum #4 A. R. 90 .160 9,200 1000 69 .160 9,300 1100 ‘ 72 .323 11,100 1150 67 .329 12,300 1200 60 .360 11,900 1250 59 .395 12,300 1300 56 .370 10,600 1400 56 .370 11,600 1500 ' 62 .360 11,600 1600 62 .325 10,900 1650 65 .360 11,300 1950 66 .230 12,100 -3- Brake Drum #5 Sample Rockwell Hardness Defl.@_;px.1oad fiax. Load A. R. 65 .170 9,000 1000__ 62 .160 10,000 1100 65 .210 6,500 1150 59 .360 11,400 1200 60 .230 6,000 1250 57 .365 11,250 1300 55 .240 7,900 1400 60 .230 7,500 1500 62 .235 7,30 1600 66 .170 5,600 1650 66 .200 7,000 1950 65 .205 5,500 - 9 - Experimental Work II A study of the effect of annealing temperatures upon the cold-drawing properties of hot—rolled stock was also made. The Rockwell hardness of several pieces was noted and the pieces annealed for one-half hour at temperatures varying from IOOOOF. to 19500F. and slow—cooled in the furnace. The Rockwell hardness was then again noted. Considerable difficulty was encountered in getting conparable Rockwell readings in this eXperiment, due to irregularities in the stock used. This difficulty was overcome in the following manner. Two pieces were run in each heat and the change in hardness of each noted. An average "original hardness" was computed and the average change in hardness for each heat added, or subtracted, to this to obtain a value which could be plotted. The same care was exercised in obtaining deflection read- ings, the average deflection for each heat being used. In this case, as well as in the previous one, care was taken that the heating—rate, cooling rate and all other conditions should be identical for each run. The shape of the draw obtained in the ductility machine seemed to depend a great deal upon the annealing temperature. The "as received" pieces drew out very thin and became balloon- shaped. This continued until an annealing temperature of 5000F. ~6000F. was reached when a smooth draw with very little decrease in thickness was obtained. This type of draw continued thru the remainder of the range of annealing temperature. Date Sample A. R. H. T. Diff. 13 Average Plotted Hardness Hardness Hardness Difference Value A. R. 60 -- __ _-_ 61 __ —- —— 60 200 64.25 64.625 - 4 .375 63.0 63.5 4 .5 4 .4275 60.4 300 63.0 63.675 4 .675 62.75 4.375 41.625 41.25 61.25 400 62.1 61.5 - .6 60.0 62.5 42.5 4 .95 60.95 500 60.0 62.125 42.125 57.0 60.675 43.675 43.0 63 600 62.0 64.0 42.0 60.5 65.75 45.25 43.625 63.625 700 61.0 63.0 42.0 55.0 63.0 +8.0 +5.0 65 600 63.0 69.0 46.0 56.0 . 63.625 45.6 45.6 65.6 900 63.0 67.25 44.25 46.0 61.5 45.5 44.675 64.675 10005 59.0 65.0 46.0 59.0 63.0 - 144.5 45.0 65 1100 56.0 61.5 +5.5 55.0 62.0 47.0 46.25 66.25 1150 56.0 62.0 44.0 56.0 62.0 44.0 44.0 64 1200 61.0 65.0 47.0 62.0 66.0 44.0 44.0 64 - 11 _ Sample A. R. H. T. Diff. in Average . Plotted Hardness Hardness Hardness Difference Value 1250 59.0 62.0 43.0 56.0 62.0 46.0 44.5 64.5 1300 56.0 59.5 43.5 59.0 62.5 43.5 43.: 63.5 1400 57.0 60.6 43.6 62.0 63.0 41.0 42.4 62.4 1500 62.0 62.5 4 .5 56.0 57.0 41.0 — .75 60.75 1600 56.0 57. 41.0 59.0 37-25 -l-75 -3-75 59.625 1650 60.0 62.0 42 56.0 57.75 4 .25 - .675 60.675 1950 5 .9 56.0 -3. 54.0 57.25 43.25 41.25 61.25 _ 12 _ Draw Tests Hot—Rolled Stock Sample Max.Load Defl.@ Hax.Load Aver. so.in. in inches A. a 11,900 .327 A. R. 11,950 .316 .321 200 11,650 .322 11,750 .315 .316 300 11,700 .316 11,650 .322 .320 400 11,650 .324 11,600 .315 .319 500 - V 11,600 .320 11,900 .322 .321 600 11,900 .325 12,600 .365 .345 700 . 11,600 .340 11,600 .330 335 600 12,400 .360 12,200 .340 .350 900 12,250 .360 13,700 .365 .362 1000 12,600 .345 12,200 .340 342 1100 13,350 .360 13,200 .353 356 1150 13,100 .360 12,600 .350 355 1200 14,700 .383 14,400 .370 ‘ .376 Sample Hax.Load Defl.@ Hax.Load Aver. é] so. in. In inches 1250 13,700 .365 13,000 .374 369 1300 12,900 .365 12,400 .351 353 1400 11,400 .346 11,000 344 .315 1500 12,300 .356 11,500 .344 .351 1600 12,000 .357 11,700 .352 354 1650 10,900 ‘ .329 11,600 .330 329 1950 11,600 .356 10,400 .355 .356 / _ 1h _ r0 An examination of the hardness curves (Fits. 6-30) ob— tained Shows that the reaction of all of the hardened steels to heat—treatment is apparently the same. All of the curves have about the same general shape. The annealing temperatures for the first two drums were only carried to what was considered a full annealing temperature. It was only by experimenting that it was found that changes occurred aboce this point and that the temperatures should be carried higher. The strains due to cold—working are, to all appearances, removed just above 10000F. as there is a marked softening at this point. The steel continues to soften thru 11500F. - 12000 F. and then hardens. A second softening reaction follows with a maximum softness being reached at 13000 F. and then a hardening effect again takes place. The variation in hardness is not great, being about five points Rockwell, but is consistent and found in all pieces exam- ined at about the same points. The first change in hardness could not be due to trans- formation at the critical point but the rehardening effect began in the neighborhood of the AC point. In the deflection curves (Figs. 31-34) the same trend is found with a marked increase in ductility above lOOOOF, A maximum deflection is reached at ll50°F. - 12000F. with a sub— sequent falling off and then an increase as in the hardness curves. The curves did not exactly coincide for temperature, but if the mean hardness and mean deflection curves are compared (Fig.35) it will be noted that there is a great deal of correlation. The IIiFIGS. 26-30 inclusive 1 -~i~.t‘.“- aw'.’ a havE—Curves showing the relation between lp' annealing temperatures and Rockwell hardness. .c‘p'o— yum. M ..‘(Ihfiu' .Mgn—fl ‘ u | . valid-vi "- ' -—-.—... r-‘ .- . a..u—..-—--w-.-nn~.u ,'.A_m—.-’.J~-..., .¢ i -——-— —--—4~..—-a‘n. \nu—‘a I . , . k‘R-" —~-_~._aN-—- ”.- . i. r 3 .4 $ M +11 ‘ r 0 r '5‘ 4‘ . “1.. .a- L..- ‘J 1 I V . \s . v LID ' as '1 [er 911 gnrwoda '4 Us, . _‘ "31%: HO {IVJ'EI .— p _‘ I E: - f '- E . | I ‘ ‘ ¥ JALS LL ,1 ‘ IL \ 0“:- '- A ’~ 'IUJ ~ I q -- I .1 f” .3; ' J L \I ’3 g‘Jfljv-‘J Itt 9i i) 1.! f- i; 2000 I800 Icon E Tempera/are I); f h 8 ff/‘ecf of Aryan/in! Emperafares on h’ardness flra/(c Drum '7 ,LI11111I!11 90 80 7o 60 5'0 floclwcfl flan/7725.3 3"5ca/c "1’ An"! 2000? IOOO [‘00 3 O O Tempera fa re l); /' i} 8 3 800 Iffecf of Apnea/I'hg fenperaturc: on liardneas flrqle Drum *z IJIlfiLI..llll 90 60 70 W JD 'fiocku’efl flare/peas B‘Sca/c 8000 ICOO [.00 i 7": piper afar: [/7 f 1‘. o 0 M00 — ff/ecf of Apnea/1'77, few/erafares on Hardness brake Drum *3 90 90 70 00 3'0 Racine” f/a ra’77e33 3 ' jock. [ffeof o f Aamea/ing ’0 Ten/cratereJ on flardness flrake drum "‘ y [800 .- laoo L. Ritz/men: fire 1'): F 4‘. 8 l 1.— moo— soo_. L. __A L l l l I J l | | '0 80 70 60 to flatly!” l/drdpeas ,3 5c a/c £000 ’800 ’6” \ t 6 I200 % O § fern/zero fare /'77 f“ 800 Effect of Annealing rein/crarures on flat-dues: 52-041 Drum ”I lllllllll 00 80 70 so .ro flee/we” flordpess 29 'Sca/c 411..---- eviauloni 65-15 .8011 neewied noidsfer ed: sniwode sevruO noiioefleb ediobns aavudsreqmei anilsenns {iffiiomf dirowfliuoE-nosromfi end no benisddo .onidosl ‘ 1.00 K F'" R \ _ U 6 "9%— K h . k — ‘1 gape... k m_ eoo__ ’ (if! of a I Janna/fag 7': Mpg/'4 hint: on Ductility flrale Draw» '8 a,” e ’00 93/7: cf/op i: ipcfies Vi 8009 _ a 8. I \ Temperature in /" o} f/Ieef of dancer/1'»), m; fl'm’acraftres a» 0013’ drake on». #1 n. 02w .’” .400 Def/e c7102; 1': itc/Ies 1000 _ [000 ._ I00 \ 7" 3 mp er aim-e r'n f ’ § § I I ff/eef’ of flawed/l»! Tear/crank” on Ductility Irate fir nn *7 ' .200 .300 .m Def/ec/Ibfi 1'7) I've/5:: EM/aerafure ' in F — [1700f 0f Apnea/1n, fem/erdfyffs a” o'crlllf, IGOO — leoo —- 1m __ ’2‘” L‘ CC: ::.::-::.’_:::::: baa .— 1_. 8 not J1 I I 1 l J l l ./50 .300 .3“ Def/ea 77cm in Inc/tea 1:25?! fifeof o f lumen/i173 Rmferafure: on ”amines: 80°“. drake arena“? 1000 .— IOOO —- 4 Ear/vent fire I}? F ° F. 8 l IOOO .— 800—. iaohr:// fldra’peas 3. 5c a/c Effect of Annealing Ten/aerafures on liar-dues: ‘0‘” _‘ drake 0pm" *4" lean __ I000 -— \ '0 o ! 7: 727,0 I 600 .. era/arc /‘7; f" ! Iooo —— !!!!!!!!! 80 80 70 ‘0 Jo fi’ochrc/l flaro’nes: B 'Sca/c -:-.....J L“ ff! 0 c; o ; 4 fly... . I JwfiigF1031131-34 inclusive 2 001) i—_ ' ' Curves showing the relation between .1 I annealing temperatures andethe deflection obtained on the Emerson-Southworth Enctility f. -_ l-iachine. ’1 . \ \ 1V0" -e- 7 £401. 7?,wprra f are x); l I 1’09“ .. " . If" f.‘ If}: s“ V sviauloni £5- 3 .8311 neewted noiisle: 9d: smiwoda eeVIuO noiiosItob sfiiobns aazujsrsqved anilssnns yiifiivnfi flJrodeuoE-noaromfl ed: no benisido .snidosf Ten/erafure in F' T T (if; of o I A haul/1'»: 7': wiper-a I‘ll/vs on Dec fih'fy Irate Dram '8 .200 .309 ' Def/e cf/op it broke: Temperature I): f 1 T 8009 _ 1 1800 TTT l \ o} 800.... RM/crafare: a» Dvcf Effect of Arne-alt)? [19v drake are». '1 L v Def/e char; in bro/res .8009 _. IOOO __ \ A Tam/acra/are I): f a s 3 § l I § I (”03" of flawed/I773 ‘Tcn craft/re: on Ouch/try arake Iran *7 lljlllll ' .100 .300 .m Ref/e c I70 7: I}; lac/9 e: rem/aerafure ' in F 2000 L I800 F- moo ""' 1m —- 6 00 ./50 fffecf of Anne a/I'n, feMpera/llres on Dach/If] Brake Drumi’f c1-------_..------ --‘ llllllLlJJ .300 .300 'm Def/cc 77.017 in Inches ; FIG.55fE. Curves showing the relation between annealiLg temperatures andtthe mean values of hardness and deflection. L . ‘ ,"I‘§.‘I( ! .2 \ ‘ 1: \ U r'fuo : 151.... 3 I 5‘1 ‘3 5d noiielsr oi: gniwoda esvruO sen sdJans GOTUJBISQHSJ anilsenns .noiioelieb bus eesnbrsd IOOO 33§ fem/acral‘ure in f § 800 [feet 0/ Apnea/1'»; ”nope rafuroa on fiardzzcss and Doc-fill?) Alec» Curre: flan/17:3 s fiac/IY/Q ------ JJ.IQJIIIILI Joe . 300 . foo 1 lDcl‘l/c¢:)l*/'orr 1'); [rm/165' I 50 do 70 ‘ [’0 of we// flara’ re: s 5 15¢ a/e [IF-UQ p...“ Lg'firn-‘I on: aim-OOH M' " 1 ~«';— FIG. 56 3 Curve showing the relation between i l annealing temperatures and the deflestion obtained in hot-rolled stock. The Rockwell hardness is given in the small circles. T\ ' O) 3 .EIT noewisd noitslez 3%: rxiwoia evruO noiiaelleb ad: has aeruisrsqmei guilssnns iEeono; 3i? .iooia beIIor-Jod mi bonisido .esfotio Llama ed: mi nevig ei eesnbrsd 2000 IBOO I600 [900 AZUV 3 Te m/oe rafare [27 f ‘00 200 F e ._ [flaw-fol. Appealing @ fiMfcrd/llre.’ 'on Ouch/(7" .0} Hal-rain! 52% c k. k_ O=iocfiWe// fiardres: L. P— L—. &e//ec}7077 f); lire/has - 1 kn only marked difference between the two curves is that the hardness curve lags behind the deflection curve. Taking these facts into consideration it appears the t in annea lin ng for a subsequent dr w a temperature of llSOOF.- lEOOOF. should give the best results. The data collected from the eXperimental work on the hot—rolled stock does not show any correlation between hardness and ductility (Fig.36). In this case it appears that the ductility is much more sensitive to irregularities as it varies consideraoly when there is no variation in hardness. It should be noted that the deflection curve of both the cold-work steel and the hot-rolled stock show approximately the same variations. It is ordinarily assumed that no change takes place in an un— quenched steel until the critical point is reached. In this case hardening began about the time oxidation was noticed (#OOOF.) and reached its maximum value at 6000 F. From this point the hard- ness rerm ined at a constant value until the lBOOOF. anneal was reached. At lBOOOF. it began to drOp back to the original hard- ness which was attained at léOOOF. Although oxidation was noticed at aoout the sane time that hardening started it cannot be used to account for it as all of the Rockwell readings were taken upon polished surfaces. A peculiarity noticed was that a piece heated to 600°F. be— came hard. A similar piece heated to l6OOOF., passing thru 6000F. upon heating and again upon cooling, remained at the original hardness. The hardening effect therefore must be due to changes in heating and not che n-es in cooling. A quenched piece he rdened by rapid cooling from above the critical shows the fact micro— SCOpically as well as physically. In these scrap les the chenfes are noticeable physically but no microscopic. . (Firs n-16) change takes place even at high magnifications. Another part noticed was that steel that drew well showed no microsCOpic deformation. Any steel examined that did show micros00pic deformation had been deformed beyond the safe limit for cold—drawing. In Figs. 37-38 are shown examples of steel in which a fracture is beginning. The deformation on the grains can easily be seen. In reviewing the theory given in the introduction we find the following statements which apply to this case. Jeffries and Archer say "Hardness is resistance to perma- nent deformation. hetals fail under stresses below their ulti- mate strength because they are made up of crystals. Decreasing these crystals will increase the hardness". In this case the metal did show micrOSCOpicldeformation before the ultimate strength ,4 vas reached. There vas, however, no change in grain size or the cementite particles and yet there was a change in hardness from 60-90 Rockwell (figs. L—lo). The strain mentioned by Honda should be removed by the anneal. If his statement is trueznmernal strains must be set up by the anneal itself as the annealing t.mperature is 'aried. The statement of Geiss and Van Liempt that crystals glide over each other in cold drawing and that the actual siape of the lattice is distorted does seem to apply to this case. The metal must flow around the die during the drawing operation and as, in safe drawing, no deformation occurs it is logical to se the DJ assume the crystals slip over each other. In this 0 hardness could be accounted for by the distortion of the lattice A x . 3:) t-t ’ 3013; s at griwigad'teut eruiosrfi ‘.Haoia benisrg emf} lo 003 X s, F r. .r _.;. E.) M) . L L '.'.. soieq 5 n1 gainiged Jami eruiosrfi .iooia bedisrg earsoo To 006 X ufo 5r arrA. ’11.. ’v I" -17- structure. Angus and Summers show by their work on copper, and the bronzes that hardening and so eni1r effects exist in those cases very similar to the ones found during this investigation. 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