1. Heat Treatment

2. Heat TreatmentThe controlled heating &cooling of metals for thepurpose of altering theirproperties 3. Heat TreatmentIt is used in manufacturing,providing simple and low-costmeans of obtainingdesired properties 4. Processing Heat Treatmentsthermal processes designed toincrease strength-preparingmaterials for fabrication 5. which includes:improving machiningcharacteristics reducing forming forces andenergy consumption restoring ductility for furtherdeformation 6. Equilibrium Diagram as Aidto Heat Treatment It indicates the temperaturesthat must be attained to achievea desired product and changethat will occur upon subsequentcooling 7. Simplified Iron-carbon diagram 8. ProcessingHeat Treatmentsfor Steel 9. Annealing a number of processheating operations 10. Annealingreducing hardness removing residual stresses improving toughness restoring ductility altering mechanical , physicalmagnetic properties 11. Full AnnealingHypoeutectoid steels are heated to30-60 C above the A3 to convert tohomogeneous single-phaseaustenite of uniform compositionand temperature then slowly cooledto below A1 temperature 12. Full Annealingit is time consumingrequire considerable energy tomaintain the elevated temperatureGen. Rule: 1hr at temperature/inchof thickness of largest section 13. Normalizingmetal is heated to 60C (100F)above the A3 or Acm, soakedto obtain uniform austenite,then removed and cooledin still air 14. Process Annealmetal is heated below A1,held long enoughto achieve softening,then cooled in air 15. Advantages of Process Annealcheapermore rapidtends to produce less scaling 16. Stress-Relief Annealemployed to remove residualstresses in large steel castingsand welded structures 17. Stress-Relief Anneal parts are heated below A1(550-660C;1000-1200F),held for period of time,then slowly cooled 18. Spheroidizationemployed when high-carbonsteels must be prepared formachining and formingrequired for above 0.6% carbon 19. Graphical Summary 20. Heat TreatmentsforNonferrous Metals 21. Purpose for Nonferrous Metalsto be heat-treated:obtaining uniform structureproviding stress reliefbringing about recrystallization 22. 6 Major Mechanisms:Solid Solution HardeningStrain HardeningGrain Size RefinementPrecipitation HardeningDispersion HardeningPhase TransformationNext 23. Solid Solution Hardeninga base metal dissolves other atomsin solid solution either assubstantial solutionsor as interstitial solutionsBack 24. Strain Hardeningincreases strength by plasticdeformation undercold-working conditionsBack 25. Grain Size Refinement used to increase strength,except at elevated temperatureswhere failure is by grain-boundarydiffusion-controlled creepmechanismBack 26. Precipitation/Age Hardeningis a method whereby strengthis obtained from a nonequilibriumstructure produced by a three step( solution treat-quench and age)heat treatmentBack 27. Dispersion Hardeningstrength is obtained fromdistinct second-phase particlesin a base matrixBack 28. Phase Transformationsstrengthening involves alloysw/c can be heated to form asingle high-temperature phase,transformed to one or morelow-temperature phase uponcoolingBack 29. Strengthening Heat Treatmentsfor Nonferrous MetalsAging - a continuous processwhich begins by the clusteringof solute atoms on distinctplanes of the parent lattice 30. Precipitation-hardening materialscan be classified:Naturally Aging - the req. diffusionat unstable to the stable 2-phasestructure at room temperatureArtificially Aging - require elevatedtemperature 31. Silver- Copper Equilibrium Diagram 32. Enlargement of Copper 33. Aids to understanding thenonequilibrium processesIsothermal transformation (IT) ortime-temperature-transformation(T-T-T) diagram 34. BainiteElectron microscopy mayberequired for to resolve the carbidesin the resulting structureMartensiteExceptionally strong, hard & brittle 35. Martensite 36. TemperingSubsequent cooling required torestore some desired degree oftoughness at the expense of adecrease in strength & hardness 37. Continuous Cooling Transformation(C-C-T) DiagramThese diagrams are used torepresent which types of phasechanges will occur in a materialas it is cooled at different rates. 38. Jominy Test for HardenabilityUsed to assist understanding ofnonequilibrium heat treatment 39. Hardness - a mechanicalproperty related to strengthand is strong function of thecarbon content of a metal 40. Hardenability - a measure of thedepth to which full hardness canbe attained under a normalhardening cycle and is relatedprimarily to amounts and typesof alloying elements. 41. Adding alloy to steelThe primary reason for addingalloy elements to commercialsteel is to increase thehardenability , not to improvethe strength properties 42. Quench MediaStages of quenchingFirst Stage (Vapor Jacket Stage)Second Stage of QuenchingThird Stage 43. Wateris fairly good quenchingmedium because of its highheat of vaporization. is cheap, but the bubbles maycause soft spots in metal 44. Brine (Salt) more severe quenchingmedium than water becausesalt creates bubbles , forcing amore rapid transition throughthe vapor jacket stage 45. The Role of Designin the Heat Treatmentof Steel 46. Design Details &Material SelectionProper consideration of it leads: more simple, more economical more reliable products 47. Undesirable Design FeaturesNonuniform sections orthicknessSharp Interior CornersSharp Exterior Corners 48. Residual Stressesare often-complex results ofthe various dimensionalchanges that occur duringheat treatment 49. AustemperingThe process called if the pieceis held at this temperaturelong enough, the austenite willtransform to bainite. 50. Martempering/MarquenchingThe process called if the piece isstabilized and then slowlycooled through the martensitetransformation 51. Ausforming a treatment used to strengthenmetals and improve its wearproperties 52. Surface Steel HardeningSelective Heating of the SurfaceAltered Surface ChemistryDeposition of Additional Layer 53. Selective Heating TechniquesSelective HeatingFlame HardeningInduction HeatingLaser beam hardeningElectron beam hardening 54. Altered Surface ChemistryPack CarburizingGas CarburizingLiquid Carburizing/CyanidingNitridingIonitriding 55. Heat Treatment EquipmentBatch FurnacesContinuous Furnaces 56. Box-Type Furnace 57. Car-Bottom Box-Type Furnace 58. Vertical Pit Furnace 59. Bell-Type Pit Furnace 60. Elevator-Type Furnace 61. Continuous Furnace 62. Thank You!Sario , Pamela MayReporter