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Heat Treatment 141 Sudden cooling of tool steel provides thermal stresses due to uneven cooling. It provides unequal specific volume of austenite and its decomposition product. The structural transformations are progressing at different rates in outer layers and central portion of the article. When martensitic transformation takes place in the central portion of the article, due to tension stress produces cracks. The harness depends upon essentially on the cooling rate. The effect of cooling on austenite transformation is given in Fig. 8.11. Austenite ( γ-Fe) above 723°C Water quench Oil quench Air cool Furnace cool 8.13 TTT CURVE Martensite Very fine pearlite Fine pearlite Coarse pearlite Fig. 8.11 Effects of coooling of austenite transformation The hardness depends upon the structure of materials. The different structure through transformation can be obtained using different cooling rates. The effects of cooling of austenite (steel above 723°C) transformation are depicted in Fig. 8.11. It can be nicely represented in a temperature, time and transformation (TTT) curve. It is also known as C or S or Bain’s curve. Fig 8.12 shows TTT diagram for hypo eutectoid steel. Temperature °C 900 800 723 700 600 500 400 300 Nose Stable Austenite Fine Pearlite Troostite (Upper Bainite) Transformation starts A 1 Coarse Pearlite Transformation Ends Accicular Troostite (Lower Bainite) Ms 200 100 M 50 M 80 Martensite 20°C M f 0 10 1 10 2 10 3 10 4 10 5 10 6 Time (Sec.) Fig. 8.12 TTT diagram for hypo eutectoid steel
142 Introduction to Basic Manufacturing Processes and Workshop Technology Fig. 8.13 shows a series of cooling curves which result from different rates of cooling when superimposed on TTT curve. These curves reveal the decomposition of stable austenite existing above critical temperature in various forms during cooling depending upon the cooling rate. The transformation of austenite starts during suitable cooling. The minimum cooling rate required to produce martensite in given steel is determined by the position of the nose of the S curve. The cooling rate required to avoid the nose of the S curve is called the critical cool. Any other cooling rate, faster than to that of the nose of S curve will cause complete transformation of austenite to martensite. Stable austim ite 1333°F Beginning of ferite precipitation A + F Rockwell (R ) C 10 30 40 50 Tem p. 600°F 300°F A (a) (b) 5% (c) 50% (d) 95% (e) (f) Coarse pearlite Medium pearlite Fine pearlite Feathery bainite Acicular bainite 65-60 t min 10 10 2 10 3 Martensite 10 4 Water Oil Air Furnace Cooling Time (min.) Fig. 8.13 Series of different cooling rates curves in TTT diagram Assume a cooling rate ‘a’ achieved in water, this curve does not cut the nose of TTT curve, and the pearlite transformation does not take place. However the resulting structure at room temperature is martensite. Cooling curve ‘c’ reflects that the cooling rate is slower than water and is in oil still lesser than the critical cooling rate, the curve ‘c’ will result in the micro structure composed of martensite. Curve ‘d’ and curve ‘e’ corresponds to the rate of cooling during normalizing and annealing. The parts of austenite transform to fine and coarse pearlite. The intermediate cooling rate curves ‘f ’ and ‘b’ higher than critical cooling rate results in the structure between pearlite and martensite known as feathery bannite and acicular (needles) bannite. Intermediate cooling rate is achieved by quenching or dipping the austenite at two hot oil baths maintained at different temperature such as in case of austempering (f curve) and mar tempering (b curve). Those special cooling rate will form coarse and fine bainite structure according the level of temperature of quenching. Transformation of austenite to pearlite depends upon the temperature, time and transformation curve. It relates the transformation of austenite to the time and temperature conditions to which it is subjected. As metal is heated above the critical point austenite will form in the structure of metal if it is cooled slowly with respect to time. The structure wil1 change to coarse pearlite and cementite placeless in a ferrite matrix due to transformation
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PREFACE Manufacturing and workshop
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1 CHAPTER INTRODUCTION 1.1 INTRODUC
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Introduction 3 material into finish
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1.7.3 Metal Forming Processes Intro
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Introduction 7 security procedures
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Introduction 9 FMS and Computer Int
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Introduction 11 towards economic an
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Introduction 13 capabilities of the
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Introduction 15 particular applicat
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2 CHAPTER PLANT AND SHOP LAYOUT 2.1
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Plant and Shop Layout 19 5. Working
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Plant and Shop Layout 21 according
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Plant and Shop Layout 23 5. Better
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Plant and Shop Layout 25 7. Machine
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28 Introduction to Basic Manufactur
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Non-Ferrous Materials 77 impurities
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Non-Ferrous Materials 79 It is made
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Applications Non-Ferrous Materials
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Non-Ferrous Materials 83 5.3.1.8 Gi
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Non-Ferrous Materials 85 springs, h
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5.4.2 Nickel Alloys Non-Ferrous Mat
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5.5 LEAD Non-Ferrous Materials 89 L
Page 94 and 95: Applications Non-Ferrous Materials
Page 96 and 97: Non-Ferrous Materials 93 (iv) (v) C
Page 98 and 99: Non-Ferrous Materials 95 produced i
Page 100 and 101: Non-Ferrous Materials 97 polymers,
Page 102 and 103: Non-Ferrous Materials 99 vessel mat
Page 104 and 105: Binocular Body Non-Ferrous Material
Page 106 and 107: Melting Furnaces 103 2. Steel (a) E
Page 108 and 109: Melting Furnaces 105 Blower Stove B
Page 110 and 111: 1. Well Melting Furnaces 107 The sp
Page 112 and 113: Melting Furnaces 109 operations. In
Page 114 and 115: Melting Furnaces 111 The chemical c
Page 116 and 117: Melting Furnaces 113 Firing Door Fi
Page 118 and 119: Melting Furnaces 115 20 What is ref
Page 120 and 121: 4. Specific Gravity Porperties and
Page 122 and 123: Porperties and Testing of Metals 11
Page 124 and 125: 12. Creep Porperties and Testing of
Page 132 and 133: 7.5 QUESTIONS Porperties and Testin
Page 134 and 135: Heat Treatment 131 (b) Movable type
Page 136 and 137: Heat Treatment 133 steels, in iron
Page 138 and 139: 8.6.1.2 Ferrite Heat Treatment 135
Page 140 and 141: Heat Treatment 137 1. Normalizing 2
Page 142 and 143: Annealing is of two types (a) (b) P
Page 146 and 147: Heat Treatment 143 of temperature a
Page 148 and 149: Advantages of Aus-Tempering Heat Tr
Page 150 and 151: Heat Treatment 147 carbon steel is
Page 152 and 153: Heat Treatment 149 In the induction
Page 154 and 155: Heat Treatment 151 6. Write short n
Page 156 and 157: Carpentry 153 heartwood, sapwood, p
Page 158 and 159: Carpentry 155 The proper time of cu
Page 160 and 161: Carpentry 157 9.5 DEFECTS IN TIMBER
Page 162 and 163: 9.8 FACTORS INFLUENCING TIMBER SELE
Page 164 and 165: Albumen glue Carpentry 161 It is pr
Page 166 and 167: Carpentry 163 The steel blade and m
Page 168 and 169: Carpentry 165 Jaw Clamp Trigger for
Page 170 and 171: Crosscut Saw Carpentry 167 Cross cu
Page 172 and 173: Jointer Plane Carpentry 169 When a
Page 174 and 175: Carpentry 171 pattern making and wh
Page 176 and 177: Forstner bits These are used for bo
Page 178 and 179: Pincer Carpentry 175 Pincers are co
Page 180 and 181: Carpentry 177 2. Circular Saw A cir
Page 182 and 183: 10 CHAPTER PATTERN AND CORE MAKING
Page 184 and 185: Pattern and Core Making 181 quality
Page 186 and 187: Pattern and Core Making 183 Disadva
Page 188 and 189: 3. Cope and drag pattern Pattern an
Page 190 and 191: Pattern and Core Making 187 11. Seg
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Pattern and Core Making 191 Core bo
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5. Back saw 6. Panel saw 7. Miter s
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Pattern and Core Making 195 16. Pro
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11 CHAPTER FOUNDRY TOOLS AND EQUIPM
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Strike off bar Foundry Tools and Eq
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Foundry Tools and Equipments 201 Fi
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Foundry Tools and Equipments 203 re
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11.4.2 Classification of Moulding M
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Foundry Tools and Equipments 207 5.
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12.3 CONSTITUENTS OF MOLDING SAND M
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Mold and Core Making 211 some speci
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12.4.7 Parting sand Mold and Core M
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Mold and Core Making 215 increased
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12.6. 5 Strength Test Mold and Core
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Mold and Core Making 219 Balanced t
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Mold and Core Making 221 mixture we
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Mold and Core Making 223 Molding sa
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5. Runner Mold and Core Making 225
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12.12 ROLE OF RISER IN SAND CASTING
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12.15 CORE SAND Mold and Core Makin
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12.16.2.2 Core ramming machines Mol
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12.20.1 Bench Molding Mold and Core
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Mold and Core Making 235 This hard
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Mold and Core Making 237 Stirrer Pl
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Mold and Core Making 239 11. What i
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13 CHAPTER CASTING 13.1 INTRODUNCTI
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Casting 243 gravity only and no ext
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Casting 245 (iv) (v) Opening the di
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Casting 247 Applications 1. Carbure
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Casting 249 containing a mixture of
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Semi-Centrifugal Casting Casting 25
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Casting 253 Table 13.1: Probable Ca
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16. Swells 1. Too soft ramming of m
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13.12 QUESTIONS Casting 257 1. Desc
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51. Explain the causes and remedies
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Advantages of forging Some common a
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Forging 263 on it. Forgeable metals
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14.4.6 Open fire and stock fire fur
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Forging 267 10. The place of the me
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Forging 269 pickling in acid, shot
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Hand hammers Forging 271 There are
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Shovel Forging 273 Shovel generally
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Forging 275 opposite to drawing and
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Forging 277 Spring hammers may be m
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14.12 REMOVAL OF DEFECTS IN FORGING
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Forging 281 7. Pneumatic riveting m
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Hot Working of Metals 283 between a
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Hot Working of Metals 285 4. Porosi
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Hot Working of Metals 287 type of t
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Hot Working of Metals 289 Hot pirci
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Hot Working of Metals 291 the punch
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16 CHAPTER COLD WORKING 16.1 INTROD
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16.5 ADVANTAGES OF COLD WORKING Col
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Cold Working 297 Cold working proce
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Cold Working 299 steels are used in
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Cold Working 301 seaming and spinni
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Cold Working 303 Each section must
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Cold Working 305 12. What is impact
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Welding 307 Toe Fusion zone Weld fa
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Welding 309 2. Horizontal position
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Welding 311 5. Gas Metal Arc Weldin
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Welding 313 2. Carburizing welding
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Welding 315 could occur if the cyli
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Welding 317 8. For repairs, calibra
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Welding 319 mains electricity suppl
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Welding 321 6. Chipping hammer Chip
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Welding 323 2. Shielded metal arc w
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Electric power source Welding 325 B
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Welding 327 13. Welders and workers
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Welding 329 Where H = heat generate
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17.7.1.2 Resistance Seam Welding We
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Welding 333 5. Surface of the jobs
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17.8.3 Explosive Welding Welding 33
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Welding 337 be scattered. This scat
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Welding 339 Porosity Fig. 17.31(iii
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Welding 341 (b) (c) Bad welding tec
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Welding 343 exceeding 450°C and be
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Welding 345 7. What effect does wel
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Welding 347 (i) Spot welding (ii) S
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1. Black Iron Sheet Sheet Metal Wor
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Sheet Metal Work 351 (g) Bossing ma
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Sheet Metal Work 353 10. Blow horn
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Sheet Metal Work 355 4. Trammel. Fi
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Sheet Metal Work 357 18.4 FOLDING T
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Sheet Metal Work 359 4. Hem (single
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Sheet Metal Work 361 moveable. When
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Sheet Metal Work 363 4. Blanking. I
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Fitting 365 scriber, semi-circular
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9. Miscellaneous Tools Fitting 367
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19.2.1.11 Surface Gauge or Scribing
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Fitting 371 machined true to keep t
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Fitting 373 the thimble the spindle
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19.2.3.3 Caliper Fitting 375 Calipe
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0 .44 1.5 Fitting 377 12mm 0 5 1015
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Fitting 379 Scriber Spirit-level Sq
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Fitting 381 4. Ring gauge 5. Snap g
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19.2.4.1.3 Universal swivel base ma
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Fitting 385 (A) Type of Cut The mos
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Fitting 387 1. Hand file 2. Flat fi
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Fitting 389 Hand drill Pneumatic dr
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S h a n k D ia Fitting 391 in Fig.
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19.2.7.1 Pliers Fitting 393 Pliers
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Fitting 395 graded from fine to coa
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20 CHAPTER METAL CUTTING 20.1 INTRO
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Metal Cutting 399 turning, facing a
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(vii) Nose radius Metal Cutting 401
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Metal Cutting 403 Continuous chip D
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Metal Cutting 405 20.7 QUESTIONS 1.
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Lathe Machine 407 2. Centre or engi
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Lathe Machine 409 1. Bed 2. Head st
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Lathe Machine 411 1. End of bed gea
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Lathe Machine 413 It is rotated by
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Lathe Machine 415 (b) Operations wh
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Lathe Machine 417 Job Feed lever To
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Lathe Machine 419 longitudinal and
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Lathe Machine 421 22.12 QUESTIONS 1
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Drilling Machine 423 5. Feed handle
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Drilling Machine 425 feeding the dr
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Number sizes Drilling Machine 427 I
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Drilling Machine 429 the main cutti
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Drilling Machine 431 22.5.4 Counter
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22.7 CUTTING SPEED Drilling Machine
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Shaper, Planer and Slotter 435 take
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Shaper, Planer and Slotter 437 the
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Shaper, Planer and Slotter 439 work
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23.8 SHAPER OPERATIONS Shaper, Plan
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Shaper, Planer and Slotter 443 a st
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Shaper, Planer and Slotter 445 Ram
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24 CHAPTER MILLING 24.1 INTRODUCTIO
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24.4 TYPES OF MILLING CUTTERS Milli
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Milling 451 2. Planer milling machi
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Front brace Milling 453 It is an ex
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Face milling Milling 455 Fig. 24.9(
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Milling 457 A B Straddle milling (m
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25.2.1 Production of Metal Powders
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Particle shape Powder Metallurgy 46
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Powder Metallurgy 463 3. The dimens
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25.6 QUESTIONS Powder Metallurgy 46
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Inspection and Quality Control 467
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26.3.7 Fundamental Deviation Inspec
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INDEX A A feeler gauge 381 Abrasive
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Index 477 Cartridge brass 81 Case h
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Index 479 Core sand preparation 230
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Index 481 First aid 30, 39, 41, 49,
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Index 483 High speed steels 62, 66,
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Index 485 Mechanical properties 116
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Index 487 Pattern construction 195
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Index 489 Role of riser 227 Roll fo
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Index 491 Surface cleaning process
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Index 493 W Water seasoning 156 Wax
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