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PREFACE This report was prepared by L. C. Schroeder and D. R. Poirier of the Department of Metallurgical Engineering, The University of Arizona. The technical monitor was Mr. James Morris of the Transportation Systems Center in Cambridge, Massachusetts. Dr. Roger K. Steele, then of the Federal Railroad Administration, Transportation Test Center in Pueblo, Colorado graciously arranged for the thermite-welding at the FAST facility in Pueblo. Messrs. Morris and Steele generously made themselves available for technical consultation for the duration of the project. Their assistance is gratefully acknowledged. Preceding page blank iii METRIC CONVERSION fACTORS App•••I.... c••"••a1... •• M••rlc M....... .. - ~ A" IC••"I••• ,... M"rlc M . s--:: I,.,., •••• ,.. •••• ...111,1, " T. I'.... I,.... •... ,••_ ........, " ,. ,... I'.... = .. fl.. - .. - ~ .. LENGTH a LENGTH -- _ ..iUi_'... .... iRc.... I. :: an e...U...... 0.. inc.... i. - .. _,... 2.2 .... h .. "2.' -,~,.. COlI - == :=.... _,... 1.1 ,.nt. yd II :Ill CIft'O""1II _.. =- .. ki_... •.• mile. .1 .,. ,ant. 0.' _.... "'-=- _ • ";1.. 1.1 ki........... iiL- ::: == AREA AREA _ = :I I • = rJ _ .......,...... '.11 __ .. ..I _ ••• _'" clllti...... rJ = ..1 _ ••_I... 1.2 aq ,ant. .,; "I _. .... _.. .........2 _ ..2 _ .. kil....'.. •.• aq i1.. ",2 .,.,a _-,..... ••• _........ .". • loa hac.....,0.000 .11 2.. •. roil _ .,.. 2.' ell"'" lIil__ ".". _ ... _.. •.• ......... ... - = .. .. ;:;.. MASS (w.I"'1 ...<" MASS (w.i,··1 -::: !2 =-- • .._ 1.031 ounc" .. .. _. 21 .-. e= kt kilogr_ 2.2 pound. .. .. 0." kilogr_ kl ::, _.11000 ktI 1.1 _ '0.. ......, 0.' _... "'-'i:---- IZOOO", • = 0 VOLUME _ a- .. VOLUME = • • onillUiI..... g-.. .milil.. 1.'2 ".dld _. II 01 .... ..._. ,. 2 1 pont. III Tbap "b' 11 Illillilit.....1 - = ... II... .1 01 'Iu':=~ :Ill ..iUili.... "".. ~ I Ii'... 1.111 _rt. ... c c.... 0.2' 'i'... I '-.. 1 10,... 0.2' lIlOlI.on. ~' pi pin,. 0.'7 lit... 1 ;;;;;- ..) cubic l1li'.. 3. cub~c ,... h ) II' "".... 0.95 II,..., -....) cubic 1111'.' 1.2 cubiC ,ani. yd ';' lIlOlIon. U Ill... ') _ ~ .. c.... ~c '"' 0.02 cUb~C 11111.. '" .. TEMPERATURE (IIIC" , ..) cuboc ,lid. 0.1' cubIC mI'''. ",2.. =- _. TEMPERATURE (•••c" - .'c C.,.Iu. .111_ ' ..........1' ", _ ,__ _ 221 '_'.'- " ' ..........1. iI'.1". C.I.iu. 'c __ .. • temper.lUre I""'r.cliot l.mpera'WI .... -- , 221 __ .. I, 22 .... 212 -40 0 !40 .0 l 120 1.0 aoa J con\l'''kJ~ ~.;;; 'ai~ ,~ ,.~I -, In • 2.54 tel&llcllvl. f ... 01"-' ...e' Mtd PlUf. dilla.led '.-bIn. seo NBS MISC. "ubi. 2N. i· =... _I' it '.' l' I 'I' (;0' '. • ' ••' ',' Ito Unl" of ".,ghe. and ....SUf••• 'uc.I2.25. ~ C."IOQ No. Cll.IO.2So. ! _! ~g 31 C Ill. TABLE OF CONTENTS Section 1. I NTRODUCT I ON ••••••••••••••••••••••••••••••••••••• 1 1.1 Statement of the Problem.................... 1 1.2 Objective of this Study..................... 2 2. REVIEW OF RELATED STUDIES •••••••••••••••••••••••• 4 2.1 Application of the Aluminothermic Process... 4 2.2 Alternative Reductants to Aluminum.......... 4 2.3 Additives that Affect the Aluminothermic Process. .................................... 5 2.4 Thermite Rail-Welds......................... 7 2.5 Weld Integrity.............................. 10 2.6 Residual Stresses in Welds.................. 16 3. EXPERIMENTAL PROCEDURES •••••••••••••.•••••••••••• 19 4. RESULTS AND DISCUSSIONS •••.••••••••••.•.••••••••• 23 4.1 Mechanical Properties....................... 23 4.1.1 Hardness Profiles••••••••••••.••••••• 23 4.1.2 Impact Properties ••.••••••••••••••••• 24 4.1.3 Tensile Properties •.••••••••••••••••• 25 4.1. 4 Fractography of Impact and Tensile Specimens .•••.•••.••••••••••. 26 4.1.4.1 Charpy V-Notch Specimens in the HAZ.................. 27 4.1.4.2 Charpy V-Notch Specimens in the Weld Metal........... 28 4.1.4.3 Tensile Specimens in the HAZ 29 4.1.4.4 Tensile Specimens in the Weld Metal.................. 30 4.2 Structural Analyses......................... 31 4.2.1 Macrostructures •••••.•••••.•••••••••• 31 4.2.2 Microstructures •••••••••••••••••••••• 33 4.2.3 Inclusion Evaluation••••••••••••••••• 34 4.3 Thermal Measurements........................ 36 4.4 Residual Stresses........................... 39 v TABLE OF CONTENTS (CONT.) Section Page 5. CONCLUSIONS.................................... 43 6 • REFERENCES. ••••••••••••••••••••••••••••••• .• •••• 47 APPENDIX - THERMITE WELDING (FIELD WELDING).............. 55 vi LIST OF ILLUSTRATIONS Figure 1 RESIDUAL STRESSES IN A NONREINFORCED THERMITE RAIL-WELD.......................................... 59 2 MOLD CONFIGURATION AND FLOW PATTERN OF THE MOLTEN STEEL FOR THE THERMITE RAIL-WELDS •••••••••••••••••• 60 3 THERMOCOUPLE LOCATIONS FOR WELDS 1, 2 AND 4 •••••••• 61 4 LOCATIONS OF THERMOCOUPLES IN THE WELD METAL OF WELD 9.......................................... 62 5 LOCATIONS OF TENSILE AND IMPACT SPECIMENS, HARDNESS PROFILES AND MICROSTRUCTURE SPECIMENS IN WELDS................................. 63 6 LOCATIONS OF STRAIN GAUGE ROSETTES FOR RESIDUAL STRESS MEASUREMENTS................................ 64 7 HARDNESS PROFILES OF WELDS 1, 4 AND 7 ..•••.•..••.•• 65 8 HARDNESS VARIATIONS IN THE HAZs OF ALLOY RAILS RELATIVE TO THE HARDNESS OF PARENT RAIL •••••••••••• 66 9 HARDNESS VARIATIONS IN THE HAZs OF STANDARD AND OF HEAD-HARDENED RAIL RELATIVE TO THE HARDNESS OF PARENT RAIL........................................ 67 10 HARDNESS OF THE WELD METAL AS A FUNCTION OF PREHEAT TIME AND DISTANCE FROM THE WELD CENTERLINE ••••••••• 68 11 FRACTURE OF IMPACT SPECIMEN THROUGH THE REGION OF MINIMUM HARDNESS IN THE HEAT-AFFECTED ZONE ••••••••• 69 12 FRACTURE SURFACE OF FIGURE 11: (a) ORIGINAL RAIL SIDE; (b) HAZ SIDE ...•.••••••••••••••.••••••••••.• 70 13 FRACTURE OF IMPACT SPECIMEN THROUGH THE REGION OF MINIMUM HARDNESS IN THE HAZ OF THE HEAD-HARDENED RAIL OF WELD 8. (a) ORIGINAL RAIL SIDE; (b) HAZ SIDE........................................... 71 14 REGION OF EASY SEPARATION OF THE HAZ SIDE (REGION OF MINIMUM HARDNESS) OF THE IMPACT SPECIMEN FROM THE CrV RAIL OF WELD 4 ..•..•.....•......••.•.. 72 vii LIST OF ILLUSTRATIONS (CONT.) Figure 15 FRACTURES OF IMPACT SPECIMENS FROM THE WELD METAL. (a) WELD 1: ALLOY WELD METAL, (b) WELD 8: STANDARD WELD METAL ••••••••••••••••••••••••••••••• 73 16 LOW DUCTILITY FRACTURES OF TENSILE SPECIMENS IN THE REGION OF MINIMUM HARDNESS. (a) FROM WELD 1 IN THE Cr RAIL, (b) FROM WELD 4 IN THE STANDARD RAIL................................................. 74 17 "CUP AND CONE" FRACTURES OF TENSILE SPECIMENS IN THE REGION OF MINIMUM HARDNESS. (a) FROM WELD 1 IN THE CrMo RAIL: (b) FROM W~~D 8 IN THE HEAD- HARDENED RAIL . 75 18 "CUP AND CONE" FRACTURES WITH RADIAL FEATURES FROM TENSILE SPECIMENS IN THE REGION OF MINIMUM HARDNESS. (a) FROM WELD 4 IN THE CrV RAIL: (b) FROM WELD 8 IN THE erMa RAIL..................................... 76 19 TENSILE FRACTURES OF THE HAZ IN THE REGION OF MINIMUM HARDNESS. (a) FROM WELD 4 IN THE STANDARD RAIL: (b) FROM WELD 4 IN THE CrV RAIL ••••••• 77 20 FRACTURES OF TENSILE SPECIMENS FROM THE WELD METAL. (a) WELD 3, ALLOY WELD METAL: (b) WELD 4, STANDARD WELD METAL •••••••••••••••••••••••••••••••••• 78 21 FRACTURE OF THE TENSILE SPECIMEN FROM THE STANDARD WELD METAL OF WELD 6 •••••••••••••••••••••••• 79 22 MACROSTRUCTURE OF THE HEAD AREA OF WELD 6 •••••••••••• 80 23 TENSILE FRACTURE OF THE ALLOY WELD METAL OF WELD 10 SHOWING MICROPOROSITY ••••••••••••••••••••••••••••• 81 24 MACROSTRUCTURE OF WELD 2, ALLOY WELD METAL ••••••••••• 82 25 MACROSTRUCTURE OF WELD 10 SHOWING THE EFFECT OF A LONG PREHEAT......................................... 83 26 PEARLITIC STRUCTURE (a) AND TRANSITIONAL PEARLITE AND BAINITE (b) IN WELD METAL OF WELD 14 ••••••••••••• 84 27 VERY FINE TRANSITIONAL PEARLITE IN THE HAZ OF THE Cr RAIL OF WELD 1 . 85 viii LIST OF ILLUSTRATIONS Figure 28 PROEUTECTOID FERRITE IN THE WELD METAL OF WELD 6 •••••• 86 29 SPHEROIDITE AND DEGENERATIVE PEARLITE IN THE OUTER EDGE OF THE HAZ OF THE HH RAIL OF WELD 7 •••••••••••••• 87 30 ALUMINA (WITH SILICA) INCLUSIONS IN THE CrV FUSION ZONE OF WELD 6........................................ 88 31 TEMPERATURE AS A FUNCTION OF TIME AND POSITION IN THE RAIL DURING THE WELDING PROCESS FOR WELD 1 ••••• 89 32 TEMPERATURE AS A FUNCTION OF TIME AND POSITION IN THE WELD METAL OF WELD 9.............................. 90 33 RAIL TEMPERATURE DISTRIBUTIONS AT THE END OF PREHEAT •• 91 34 PEAK TEMPERATURES AS A FUNCTION OF DISTANCE FROM THE RAIL END: (a) WELD 1: (b) WELD 2. STANDARD PREHEATS. 92 35 PEAK TEMPERATURES AS A FUNCTION OF DISTANCE FROM THE RAIL END: (a) WELD 4 - STANDARD PREHEAT, (b) WELD 3 - LONG PREHEAT...................................... 93 36 PRINCIPAL RESIDUAL STRESSES IN WELD 11•••••••••••••••• 94 ix LIST OF TABLES Table 1 MECHANICAL PROPERTIES FROM BEND TESTS ON RAIL AND WELDED RAI L. ••••••••••••••••••••••••••••••••••• 95 2 EXPERIMENTAL CONDITIONS FOR WELDS ••••••••••••••.••• 96 3 NOMINAL COMPOSITIONS OF RAILS AND OF WELD METAL •.•• 97 4 HARDNESSES OF THE HEAT-AFFECTED ZONES •••••••••••••. 98 5 IMPACT ENERGIES OF THE WELDS AT 200C ••••••••••.••.• 99 6 TENSILE PROPERTIES OF THE WELDS ..••••..••••...••••• 100 7 FRACTURE CHARACTERISTICS OF TENSILE SPECIMENS OF THE HEAT AFFECTED ZONES ••••••••••••••••••••••••• 103 8 FRACTURE CATEGORIES OF TENSILE SPECIMENS IN THE REGION OF MINIMUM HARDNESS •.••••••••••••••••••••••• 104 9 EDS ANALYSES OF THE SURFACES OF THE AS-CAST COLUMNAR STRUCTURE IN STANDARD WELD METAL ••.•••••.• 105 10 EDS ANALYSES OF THE SURFACES OF DENDRITES IN ALLOY WELD METAL................................... 106 11 INCLUSION CONTENT OF WELD METAL .••••.••.••••.•••••• 107 12 TIME IN THE TRANSFORMATION