Heat Treating: The How and Why of Quenching Metal Parts


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Quenching is a vital part of the heat treating process in manufacturing. This presentation by Houghton International will show you how to master the process for the most efficient quenching and heat treating operations.

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Heat Treating: The How and Why of Quenching Metal Parts

  1. 1. Quenching – Mastering the Process D. Scott MacKenzie, PhD, FASM December 2011 The How and Why of Quenching Metal Parts
  2. 2. Quenching – Mastering the Process
  3. 3. Quenching – Mastering the Process <ul><li>Mechanism of Quenching </li></ul><ul><ul><li>Quenching occurs in three stages </li></ul></ul><ul><ul><ul><li>Vapor Phase </li></ul></ul></ul><ul><ul><ul><ul><li>Formation of vapor film around the part </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Heat transfer is slow </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Heat transfer occurs primarily through radiation and conduction through vapor </li></ul></ul></ul></ul><ul><ul><ul><li>Nucleate Boiling Phase </li></ul></ul></ul><ul><ul><ul><ul><li>High heat extraction rates </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Heat removal by bubble formation and contact of cool quenchant on part surface </li></ul></ul></ul></ul><ul><ul><ul><li>Convection Phase </li></ul></ul></ul><ul><ul><ul><ul><li>Starts at below boiling temperature of quenchant </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Slow heat transfer </li></ul></ul></ul></ul><ul><ul><li>Governs Properties and Distortion </li></ul></ul>
  4. 4. Quenching – Mastering the Process Vapor Phase Nucleate Boiling Phase Convection Phase
  5. 5. Quenching – Mastering the Process
  6. 6. Quenching – Mastering the Process <ul><li>Moment of immersion – vapor film around probe </li></ul><ul><li>After 5 seconds – boiling commences at corners </li></ul><ul><li>After 10 seconds – boiling front moves along the probe </li></ul><ul><li>After 15 seconds – showing vapor. Boiling and convection phases </li></ul><ul><li>After 30 seconds – convection phase </li></ul>
  7. 7. Quenching – Mastering the Process <ul><li>Metallurgical Effects </li></ul><ul><ul><li>Carbon Content and Hardenability </li></ul></ul><ul><ul><ul><li>Avoid the nose or knee of the TTT curve </li></ul></ul></ul><ul><ul><ul><li>Cooling rate depends on hardenability of steel </li></ul></ul></ul><ul><ul><ul><li>Maximum hardness attainable is dependant on % Carbon present </li></ul></ul></ul><ul><ul><li>Cooling Rates </li></ul></ul><ul><ul><ul><li>Cooling rate is limited by thickness of part </li></ul></ul></ul><ul><ul><ul><ul><li>Limited by thermal diffusivity </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Excessive cooling rates may cause cracking or distortion </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Higher cooling rates yield higher thermal gradients </li></ul></ul></ul></ul>
  8. 8. Quenching – Mastering the Process <ul><li>Austenite will transform if held at a lower constant temperature </li></ul><ul><ul><li>Lower than austenite stability temperature </li></ul></ul><ul><ul><li>Percent transformation plotted by time versus temperature </li></ul></ul><ul><ul><li>Performed at many temperatures </li></ul></ul><ul><ul><li>Summarized in a single diagram </li></ul></ul><ul><ul><li>Called TTT (Time-Temperature-Transformation) Diagram </li></ul></ul><ul><li>A “map” that charts austenite transformation as a function of time and temperature </li></ul>
  9. 9. Quenching – Mastering the Process <ul><li>TTT Diagrams </li></ul><ul><ul><li>Time-Temperature-Transformation </li></ul></ul><ul><ul><li>Also called Isothermal Transformation (IT) diagrams </li></ul></ul><ul><ul><li>Shows the time required for transformation </li></ul></ul><ul><ul><ul><li>Start and finish times </li></ul></ul></ul><ul><li>Diagram created </li></ul><ul><ul><li>Small specimens austenitized in molten salt </li></ul></ul><ul><ul><li>Quenched into molten salt at different temperature for a specific time </li></ul></ul><ul><ul><li>Quenched in water </li></ul></ul><ul><ul><li>Metallographically examined and volume fraction of constituents are determined. </li></ul></ul><ul><li>Curves widely available </li></ul><ul><li>Permits estimates of microstructure for times and temperature </li></ul>
  10. 10. Quenching – Mastering the Process <ul><li>Diagram is simplified </li></ul><ul><ul><li>Really a mixture of curves </li></ul></ul><ul><ul><ul><li>Bainite, pearlite curves are usually shown as one curve </li></ul></ul></ul><ul><ul><ul><li>Really overlapping several curves should be shown </li></ul></ul></ul><ul><ul><li>Sufficient to understand microstructures </li></ul></ul><ul><ul><ul><li>Isothermal transformations are understood </li></ul></ul></ul><ul><ul><ul><li>Pearlite, upper Bainite, lower Bainite and martensite transformation fractions can be estimated. </li></ul></ul></ul><ul><ul><ul><li>Allows estimated times and temperatures to be estimated for heat treatment </li></ul></ul></ul>
  11. 11. Quenching – Mastering the Process <ul><li>TTT Diagram for plain carbon eutectoid steel </li></ul><ul><ul><li>A - 0.01 volume fraction Pearlite </li></ul></ul><ul><ul><li>B – 0.99 volume fraction Pearlite </li></ul></ul><ul><ul><li>C – 0.01 volume fraction upper Bainite </li></ul></ul><ul><ul><li>D – 0.99 volume fraction upper Bainite </li></ul></ul><ul><ul><li>E – 0.01 volume fraction lower Bainite </li></ul></ul><ul><ul><li>F – 0.99 volume fraction lower Bainite </li></ul></ul><ul><ul><li>G – 0.01 volume fraction Martensite </li></ul></ul>
  12. 12. Quenching – Mastering the Process <ul><li>Shape and Position of Curves </li></ul><ul><ul><li>Depends on composition, grain size and alloying elements </li></ul></ul><ul><ul><ul><li>Increasing carbon tends to retard transformation </li></ul></ul></ul><ul><ul><ul><li>Increasing alloying elements tends to retard transformation </li></ul></ul></ul><ul><ul><ul><li>Increasing grain size tends to retard transformation </li></ul></ul></ul><ul><ul><li>Retarding transformation shoves “nose” or “knee” to the right </li></ul></ul><ul><ul><ul><li>Greater hardenability or deepen harder </li></ul></ul></ul>
  13. 13. Quenching – Mastering the Process Atlas of Isothermal Transformation and Cooling Transformation Diagrams, ASM, 1977 AISI1020 AISI1050 AISI1080 AISI1095
  14. 14. Quenching – Mastering the Process AISI 1060 AISI 5160 C-0.63% Mn–0.87% C-0.61% Mn–0.94% Cr-0.88%
  15. 15. Quenching – Mastering the Process <ul><li>Quenching and Tempering </li></ul><ul><ul><li>Most common method of heat treating </li></ul></ul><ul><ul><ul><li>Heating to Austenite region, then rapidly cooling to miss “knee” to avoid transformation </li></ul></ul></ul><ul><ul><ul><li>Center and surface curves shown </li></ul></ul></ul><ul><ul><ul><li>Transformation of austenite completely to Martensite </li></ul></ul></ul>
  16. 16. Quenching – Mastering the Process <ul><li>Martempering </li></ul><ul><ul><li>Method is used to limit distortion and residual stresses in parts </li></ul></ul><ul><ul><li>Process </li></ul></ul><ul><ul><ul><li>Part is quenched to intermediate temperature at approximately the Martensite (Ms) temperature </li></ul></ul></ul><ul><ul><ul><li>Held until center of piece reaches bath temperature </li></ul></ul></ul><ul><ul><ul><li>Cooled in air or convenient manner </li></ul></ul></ul><ul><ul><ul><li>Determines how long part is held at temperature before formation of Bainite </li></ul></ul></ul><ul><ul><li>Widely used to control distortion in gears and other dimension critical parts </li></ul></ul>
  17. 17. Quenching – Mastering the Process <ul><li>Austempering </li></ul><ul><ul><li>Process of isothermal transformation of Austenite to Bainite </li></ul></ul><ul><ul><li>For this process, TTT diagram is indispensable </li></ul></ul><ul><ul><li>Shows the minimum time for Austenite to Bainite transformation </li></ul></ul><ul><ul><li>Used for planning austempering heat treatments, and determining time at temperature </li></ul></ul><ul><ul><li>Method used for austempering ductile irons and similar </li></ul></ul>
  18. 18. Quenching – Mastering the Process <ul><li>TTT Diagrams cover isothermal transformations </li></ul><ul><ul><li>Real heat treat processes cover a range of temperatures </li></ul></ul><ul><ul><li>Mixture of isothermal transformation products </li></ul></ul><ul><ul><li>Useful in planning heat treatments </li></ul></ul><ul><ul><li>Can not be used to accurately predict course of transformation during cooling </li></ul></ul><ul><li>CT (Continuous Cooling Transformation) Curves </li></ul><ul><ul><li>Austenite transformations shifted lower and to the right </li></ul></ul><ul><ul><li>Determined primarily by empirical data </li></ul></ul>
  19. 19. Quenching – Mastering the Process <ul><li>Derivation of CCT Diagrams </li></ul><ul><ul><li>Early attempts were unsuccessful. </li></ul></ul><ul><ul><li>Originally superimposed end-quench data on TTT diagram to show downward shift. </li></ul></ul><ul><ul><li>Now determined by hardness and metallographic data from Jominy End Quench </li></ul></ul><ul><ul><li>Dilatometer and Metallography used extensively </li></ul></ul><ul><ul><li>Instrumented rounds of material also used </li></ul></ul><ul><ul><li>Designed to estimate hardness of round bars </li></ul></ul>
  20. 20. Quenching – Mastering the Process
  21. 21. Quenching – Mastering the Process <ul><li>Alternatively </li></ul><ul><ul><li>Time versus temperature plot used. </li></ul></ul><ul><ul><ul><li>Hardness is displayed at the end of cooling curve </li></ul></ul></ul><ul><ul><ul><li>Difficult to predict time effect of higher austenitizing temperatures </li></ul></ul></ul><ul><ul><li>Cooling rate at 1300°F (704°C) used </li></ul></ul><ul><ul><ul><li>Based on Jominy </li></ul></ul></ul><ul><ul><ul><li>Good for pearlite transformations </li></ul></ul></ul><ul><ul><ul><li>Not as good for Bainitic transformations </li></ul></ul></ul>
  22. 22. Quenching – Mastering the Process <ul><li>Martensitic microstructures are the hardest in any carbon steel </li></ul><ul><ul><li>Only produced if ferrite and cementite is avoided </li></ul></ul><ul><li>Section discusses </li></ul><ul><ul><li>Relationship of carbon to martensite hardness </li></ul></ul><ul><ul><li>Discusses hardness can be achieved throughout a part </li></ul></ul><ul><ul><li>Hardenability term intoduced </li></ul></ul><ul><ul><ul><li>Ease of martensite formation </li></ul></ul></ul><ul><ul><ul><li>Effect of section size, cooling rates and composition </li></ul></ul></ul>
  23. 23. Quenching – Mastering the Process <ul><li>Hardness </li></ul><ul><ul><li>Function of Martensite content </li></ul></ul><ul><ul><ul><li>Hardness of martensite much higher than Pearlitic structure </li></ul></ul></ul><ul><ul><ul><li>High hardness and high strength is reason why Martensitic structures are preferred </li></ul></ul></ul><ul><ul><li>Retained Austenite formed at high carbon contents </li></ul></ul><ul><ul><ul><li>Ms temperatures drop below room temperature </li></ul></ul></ul><ul><ul><ul><li>Low temperature treatments to force transformation is done </li></ul></ul></ul>
  24. 24. Quenching – Mastering the Process
  25. 25. Quenching – Mastering the Process <ul><li>Grain size effects attainable hardness </li></ul><ul><ul><li>Smaller grain size increases hardness </li></ul></ul><ul><ul><li>Associated with carbon segregation making yielding more difficult </li></ul></ul><ul><ul><ul><li>Finer structures have shorter differences </li></ul></ul></ul><ul><ul><ul><li>Less ability to yield </li></ul></ul></ul>
  26. 26. Quenching – Mastering the Process <ul><li>Hardenability </li></ul><ul><ul><li>“ Ability to harden deeply” not “Ability to Harden” </li></ul></ul><ul><ul><li>The depth and distribution of hardness produced by quenching </li></ul></ul><ul><ul><li>Official Definition: </li></ul></ul><ul><ul><ul><li>“ The capacity of a steel to transform partially or completely from Austenite to some percentage of Martensite at a given depth when cooled under some given conditions. </li></ul></ul></ul><ul><ul><li>Affected by cooling rates, composition and grain size </li></ul></ul>
  27. 27. Quenching – Mastering the Process
  28. 28. Quenching – Mastering the Process <ul><li>Factors Affecting Cooling Rates </li></ul><ul><ul><li>Two factors </li></ul></ul><ul><ul><ul><li>Ability to diffuse heat out of the part (thermal diffusivity) </li></ul></ul></ul><ul><ul><ul><li>Ability of the quenching medium to remove heat. </li></ul></ul></ul><ul><ul><li>Thermal Diffusivity </li></ul></ul><ul><ul><ul><li>Ability of steel to transfer heat </li></ul></ul></ul><ul><ul><ul><li>Changes as a function of temperature </li></ul></ul></ul><ul><ul><ul><li>Very little change as a function of composition </li></ul></ul></ul><ul><ul><li>Quenchant </li></ul></ul><ul><ul><ul><li>Most important control over cooling rate </li></ul></ul></ul><ul><ul><ul><li>Complex process </li></ul></ul></ul><ul><ul><ul><ul><li>Depends on radiation, boiling and forced and unforced convection </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Agitation, quenchant temperature and concentration (if polymer quenchant) primary factors </li></ul></ul></ul></ul><ul><ul><ul><li>Important practical considerations </li></ul></ul></ul>
  29. 29. Quenching – Mastering the Process <ul><li>Severity of Quench </li></ul><ul><ul><li>Effectiveness of quenchant ranked by parameter called “Severity of Quench” </li></ul></ul><ul><ul><ul><li>Measure identified by “H” </li></ul></ul></ul><ul><ul><ul><li>Determined experimentally by quenching a series of round bars </li></ul></ul></ul><ul><ul><ul><li>50% Martensite region determined (dark/light etch transition) </li></ul></ul></ul><ul><ul><li>Determination of “Severity of quench” makes possible: </li></ul></ul><ul><ul><ul><li>Calculation of critical size in terms of standardized quench; </li></ul></ul></ul><ul><ul><ul><li>Calculation of critical size from a single test </li></ul></ul></ul><ul><ul><ul><li>Predicting how a know steel would behave under different severity of quench </li></ul></ul></ul><ul><ul><ul><li>Predicting hardness distribution </li></ul></ul></ul><ul><ul><li>How to do it? </li></ul></ul><ul><ul><ul><li>Quenching varies more than suspected </li></ul></ul></ul><ul><ul><ul><li>No way to translate results from laboratory to field, or to other quench. </li></ul></ul></ul>
  30. 30. Quenching – Mastering the Process <ul><li>Different bar diameters quenched in different quenchants </li></ul><ul><ul><li>Unhardened diameter to bar diameter determined (Du/D) </li></ul></ul><ul><ul><li>Ratios plotted as a function of bar diameter </li></ul></ul><ul><ul><li>H-Value determined </li></ul></ul><ul><li>Water quenching generally is given as H=1 </li></ul>
  31. 31. Quenching – Mastering the Process Severity of Quench (H) for Various Quenching Media
  32. 32. Quenching – Mastering the Process <ul><li>Ideal Diameter </li></ul><ul><ul><li>Requires definition of “Ideal Quench” </li></ul></ul><ul><ul><ul><li>Fastest possible quench, where surface of the bar would be cooled instantly to the temperature of the quenchant. </li></ul></ul></ul><ul><ul><ul><li>Handled simply by heat transfer calculations </li></ul></ul></ul><ul><ul><li>Fastest Quench, then the largest size obtainable with a specific hardenability </li></ul></ul><ul><ul><ul><li>Basis of comparison </li></ul></ul></ul><ul><ul><ul><li>Called “Ideal Critical Size”, or DI </li></ul></ul></ul><ul><ul><ul><li>Reliable method and used for hardenability calculations and specification purposes. </li></ul></ul></ul><ul><ul><ul><li>Can be determined experimentally by quenching bars </li></ul></ul></ul><ul><ul><ul><li>Can be determined by composition. </li></ul></ul></ul>
  33. 33. Quenching – Mastering the Process
  34. 34. Quenching – Mastering the Process <ul><li>Jominy End Quench </li></ul><ul><ul><li>Developed by Jominy </li></ul></ul><ul><ul><li>Characterizes hardenability of a steel from a single bar </li></ul></ul><ul><ul><li>Simple test </li></ul></ul><ul><ul><ul><li>Specimen cooled at one end </li></ul></ul></ul><ul><ul><ul><li>Provides cooling rates between water quenching and air cooling </li></ul></ul></ul><ul><ul><ul><li>After quenching, parallel flats are ground on each side </li></ul></ul></ul><ul><ul><ul><li>Hardness readings taken at 1/16 ” intervals </li></ul></ul></ul><ul><ul><li>Hardness differences can be readily compared </li></ul></ul>
  35. 35. Quenching – Mastering the Process <ul><li>Standardized Test </li></ul><ul><ul><li>ASTM A 255 </li></ul></ul><ul><ul><li>SAE J406 </li></ul></ul><ul><li>Each position corresponds to a specific cooling rate </li></ul><ul><ul><li>Cooling rate determines percentage of Martensite </li></ul></ul><ul><ul><li>Data can be used to predict hardness if cooling rates known </li></ul></ul><ul><li>Test is highly accurate and repeatable </li></ul><ul><ul><li>Excellent method for selecting steels </li></ul></ul>
  36. 36. Quenching – Mastering the Process Timken “ Practical Guide for Metallurgists
  37. 37. Quenching – Mastering the Process
  38. 38. Quenching – Mastering the Process
  39. 39. Quenching – Mastering the Process <ul><li>Severity of Quench </li></ul><ul><ul><li>Effectiveness of quenchant ranked by parameter called “Severity of Quench” </li></ul></ul><ul><ul><ul><li>Measure identified by “H” </li></ul></ul></ul><ul><ul><ul><li>Determined experimentally by quenching a series of round bars </li></ul></ul></ul><ul><ul><ul><li>50% Martensite region determined (dark/light etch transition) </li></ul></ul></ul><ul><ul><li>Determination of “Severity of quench” makes possible: </li></ul></ul><ul><ul><ul><li>Calculation of critical size in terms of standardized quench; </li></ul></ul></ul><ul><ul><ul><li>Calculation of critical size from a single test </li></ul></ul></ul><ul><ul><ul><li>Predicting how a know steel would behave under different severity of quench </li></ul></ul></ul><ul><ul><ul><li>Predicting hardness distribution </li></ul></ul></ul><ul><ul><li>How to do it? </li></ul></ul><ul><ul><ul><li>Quenching varies more than suspected </li></ul></ul></ul><ul><ul><ul><li>No way to translate results from laboratory to field, or to other quench. </li></ul></ul></ul>
  40. 40. Quenching – Mastering the Process
  41. 41. Quenching – Mastering the Process From “Practical Data for Metallurgists”, Timken Company, 8 th Edition For ½ ” Bar, the expected values are: Surface: JEQ 1/16 = 62HRC Core: JEQ 2/16 = 59 HRC For 2 ” Bar, the expected values are: Surface: JEQ 2/16 = 59HRC Core: JEQ 7/16 = 31 HRC For 3 ” Bar, the expected values are: Surface: JEQ 4/16 = 38HRC Core: JEQ 12/16 = 21 HRC
  42. 42. Quenching – Mastering the Process <ul><li>Quenching Mediums </li></ul><ul><ul><li>Many different types </li></ul></ul><ul><ul><ul><li>Water </li></ul></ul></ul><ul><ul><ul><li>Brine </li></ul></ul></ul><ul><ul><ul><li>Caustic </li></ul></ul></ul><ul><ul><ul><li>Polymer </li></ul></ul></ul><ul><ul><ul><li>Oils </li></ul></ul></ul><ul><ul><ul><li>Molten Salts </li></ul></ul></ul><ul><ul><ul><li>Gases </li></ul></ul></ul>
  43. 43. Quenching – Mastering the Process <ul><li>Water </li></ul><ul><ul><li>Approaches maximum cooling rate attainable </li></ul></ul><ul><ul><li>Inexpensive and readily available </li></ul></ul><ul><ul><li>Easily disposed </li></ul></ul><ul><ul><li>Widely used </li></ul></ul><ul><ul><ul><li>Non-ferrous parts </li></ul></ul></ul><ul><ul><ul><li>Stainless steels </li></ul></ul></ul><ul><ul><ul><li>Large forgings </li></ul></ul></ul><ul><ul><li>Agitation important to break up persistent vapor phase </li></ul></ul><ul><ul><li>Contamination can change cooling rate </li></ul></ul><ul><ul><ul><li>Emulsions, oils, soaps decrease speed </li></ul></ul></ul><ul><ul><ul><li>Salts or hard water increase speed </li></ul></ul></ul><ul><ul><li>Disadvantages </li></ul></ul><ul><ul><ul><li>Rapid cooling near typical Ms temperatures </li></ul></ul></ul><ul><ul><ul><li>Usually restricted to small parts </li></ul></ul></ul><ul><ul><ul><li>Large parts when core hardness is important </li></ul></ul></ul>
  44. 44. Quenching – Mastering the Process
  45. 45. Quenching – Mastering the Process <ul><li>Brine </li></ul><ul><ul><li>Applies to water solutions of salt (NaCl, KCl or CaCl2) </li></ul></ul><ul><ul><li>Advantages </li></ul></ul><ul><ul><ul><li>Faster cooling rate than water </li></ul></ul></ul><ul><ul><ul><li>Temperature less critical </li></ul></ul></ul><ul><ul><ul><li>Reduced soft spots from steam pockets </li></ul></ul></ul><ul><ul><ul><li>Equipment is simplier </li></ul></ul></ul><ul><ul><li>Disadvantages </li></ul></ul><ul><ul><ul><li>Corrosive </li></ul></ul></ul><ul><ul><ul><li>Hood required for corrosive fumes </li></ul></ul></ul><ul><ul><ul><li>Increased cost </li></ul></ul></ul><ul><ul><ul><li>Increased testing for concentration </li></ul></ul></ul>From “ Houghton on Quenching ”
  46. 46. Quenching – Mastering the Process
  47. 47. Quenching – Mastering the Process
  48. 48. Quenching – Mastering the Process <ul><li>Quenching Systems </li></ul><ul><ul><li>Equipment varies over a wide range </li></ul></ul><ul><ul><ul><li>Depends on size </li></ul></ul></ul><ul><ul><ul><li>Product requirements </li></ul></ul></ul><ul><ul><li>Typical system consists of: </li></ul></ul><ul><ul><ul><li>Tank </li></ul></ul></ul><ul><ul><ul><li>Agitation equipment </li></ul></ul></ul><ul><ul><ul><li>Fixtures </li></ul></ul></ul><ul><ul><ul><li>Cooling Systems </li></ul></ul></ul><ul><ul><ul><li>Heaters </li></ul></ul></ul><ul><ul><ul><li>Filtration Equipment </li></ul></ul></ul>
  49. 49. Quenching – Mastering the Process <ul><li>Tanks </li></ul><ul><ul><li>Rule of thumb </li></ul></ul><ul><ul><ul><li>“ One pound of parts – one gallon of quenchant” </li></ul></ul></ul><ul><ul><li>Holds the quenchant </li></ul></ul><ul><ul><li>Auxiliary Equipment </li></ul></ul><ul><ul><ul><li>Agitation </li></ul></ul></ul><ul><ul><ul><li>Heaters </li></ul></ul></ul><ul><ul><ul><li>Filtration </li></ul></ul></ul>
  50. 50. Quenching – Mastering the Process
  51. 51. Quenching – Mastering the Process <ul><li>Agitation </li></ul><ul><ul><li>Critical for quenching uniformity </li></ul></ul><ul><ul><li>Reduces surface to surface thermal gradients </li></ul></ul><ul><ul><li>Must provide uniform flow thru-out furnace load </li></ul></ul><ul><ul><li>Wipe vapor blanket from parts to achieve quench uniformity </li></ul></ul><ul><ul><li>Racking and Agitation work together </li></ul></ul>
  52. 52. Quenching – Mastering the Process <ul><li>Agitation Equipment </li></ul><ul><ul><li>Pumps </li></ul></ul><ul><ul><ul><li>Often selected </li></ul></ul></ul><ul><ul><ul><li>Simple </li></ul></ul></ul><ul><ul><ul><li>Easy to direct flow </li></ul></ul></ul><ul><ul><li>Propellers </li></ul></ul><ul><ul><ul><li>Most efficient method of moving quenchant </li></ul></ul></ul><ul><ul><ul><li>Compact </li></ul></ul></ul><ul><ul><ul><li>Require little piping </li></ul></ul></ul><ul><ul><li>Velocity Effect </li></ul></ul><ul><ul><ul><li>Recommend 0.5-1.0 m/s </li></ul></ul></ul><ul><ul><ul><li>Dense loads may require up to 2 m/s </li></ul></ul></ul><ul><ul><li>Number of Agitators </li></ul></ul><ul><ul><ul><li>Reduces dead spots </li></ul></ul></ul><ul><ul><ul><li>Provide more uniform agitation </li></ul></ul></ul><ul><ul><ul><li>Baffles improve flow uniformity </li></ul></ul></ul>
  53. 53. Quenching – Mastering the Process <ul><li>Achieving necessary agitation </li></ul><ul><ul><li>Requires adequate horse power to drive agitators </li></ul></ul><ul><ul><li>Most design rules based on marine propellers </li></ul></ul><ul><ul><li>Polymers more sensitive to agitation than oil </li></ul></ul><ul><li>Uniformity of agitation is just as important </li></ul>Volume - Tank Gallons HP per Gallon Oil Water 50-800 0.005 0.004 800-2000 0.006 0.004 2000-3000 0.006 0.005 Greater than 3000 0.007 0.005
  54. 54. Quenching – Mastering the Process <ul><li>Racking </li></ul><ul><ul><li>Very critical to get part properties and low distortion </li></ul></ul><ul><ul><li>Must allow proper flow of quenchant around part </li></ul></ul><ul><ul><ul><li>Minimize oil hot spots </li></ul></ul></ul><ul><ul><ul><li>Uniform heat transfer on all surfaces </li></ul></ul></ul><ul><ul><li>Specialized racks and fixtures often expensive </li></ul></ul><ul><ul><ul><li>Life </li></ul></ul></ul><ul><ul><ul><li>Alloy cost </li></ul></ul></ul><ul><ul><ul><li>Well worth cost of grinding and distortion </li></ul></ul></ul>
  55. 55. Quenching – Mastering the Process <ul><li>Quenchant Heating </li></ul><ul><ul><li>Achieved by several methods: </li></ul></ul><ul><ul><ul><li>Gas </li></ul></ul></ul><ul><ul><ul><li>Electrical </li></ul></ul></ul><ul><ul><li>Maximum rating on heaters should not exceed 10 watts/in2 </li></ul></ul><ul><ul><ul><li>Locally overheat quenchant </li></ul></ul></ul><ul><ul><ul><li>Cause premature failure of quenchant and heating elements </li></ul></ul></ul><ul><ul><ul><li>Good quench oil flow should be maintained around heaters </li></ul></ul></ul>
  56. 56. Quenching – Mastering the Process <ul><li>Quenchant Cooling </li></ul><ul><ul><li>Use of water cooled heat exchangers is not recommended </li></ul></ul><ul><ul><ul><li>Risk of water contamination </li></ul></ul></ul><ul><ul><li>Air-Oil Heat Exchangers recommended </li></ul></ul><ul><ul><ul><li>Recommended to be sized to recover maximum heat load in the time of one heat-treat cycle </li></ul></ul></ul><ul><ul><ul><li>Filtration is suggested prior to heat exchanger </li></ul></ul></ul>
  57. 57. Quenching Products from Houghton Cold Quenching Oils Houghto-Quench K Houghto-Quench G Houghto-Quench 3440 Houghto-Quench 3430 Dasco Quench LPA 15 Dasco Quench LBA 15 Aqueous Quenchants Aqua-Quench 140 Aqua-Quench 145 Aqua-Quench 245 Aqua-Quench 251 Aqua-Quench 260 Aqua-Quench 3699 Aqua-Quench C Email cfaulkner@houghtonintl.com for more information. Hot Quenching Oils Mar-Temp 355 Dasco Quench MPA 60 Below is a sampling of Houghton quenchants. However, you should consult a Houghton expert for the right product for your application.
  58. 58. Your Global Fluid Technology Partner <ul><li>We offer your operation a global network of fluids experts delivering innovative technologies, chemistries, products and services with a single focus on solving your toughest challenges. </li></ul>
  59. 59. Worldwide Coverage… One Company Over 2,000 employees in 31 countries with manufacturing and research facilities in 21 locations. Houghton helps customers around the world save on overall process chemical and disposal costs while improving production and part quality.
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