Heat%20Treatig%20Metals

1
Forging new generations of engineers
2
Heat Treating Metals
3
Heat Treating
Heat Treatment - Is The Heating And Cooling Of
Metals In Their Solid States For The Purpose Of
Changing Their Properties.
4
Principle Kinds Of Heat Treatment

• Hardening
• Tempering
• Annealing
• Normalizing
• Case-hardening
• Flame Hardening
• Induction Hardening

5
Heat-treatment Processes
All Heat-treatment Processes Involve Heating And
Cooling Metals According To A Time-temperature
Cycle Listed Below

• Heating The Metal To A Predetermined Temperature.
• Holding The Metal At This Elevated Temperature
  For A Certain Period Of Time.
• Cooling The Metal At A Certain Rate Of Time.

6
Heat Treating Furnace

• Electric
• Or
• Gas

7
Furnace Temperature Control

• Celsius Degrees On Inside
• Scale
• Fahrenheit Degrees
• On Outside
• Scale

8
Temperature Indicating Materials That Melt At
Exact Temperatures
Pellets
Crayons
Liquid
9
Effects Of Temperature On Hardness Of Steel

• Higher Rockwell Number The Harder The Steel

10
Effects Of Carbon Content On Hardening Of Steel

• Low-carbon .05-.30 No Heat Treating
• Medium-carbon .30-.60 Some Hardening
• High-carbon .60-1.5 Can Be Made Extremely Hard

11
Steps For Hardening

• Check Carbon Content Of Steel It Must Be Above
  .30 Percent To Harden
• Heat Furnace To The Upper Critical Temperature
  1400 To 1700 Degrees (F) Check Heat Treating And
  Carbon Graph To Determine This Value.
• Allow Steel Time To Completely Heat Through Out.
  
• Cool Or Quench Heated Steel As Rapidly As
  Possible In Water, Brine Or Oil. Steel Should
  Now Be Very Hard, Brittle And Ready To Temper.

12
Graph Of Temperature Ranges And Carbon Content
For Heat Treating Plain Carbon Steel

• Line ac3 shows upper critical temperature
• Line ac1 shows lower critical temperature
• Line ac2 shows point at which steel looses its
  magnetism

13
Tempering
Tempering Is A Heat Treating Process That Reduces
Some Of The Hardness In Steel To Gain Toughness
And Strength

• Steps For Tempering
• Steel Must First Be Hardened
• Reheat Steel To The Tempering Temperature
  Determined By Chart In Next Slide.
• Quench Or Cool Steel Quickly After It Reaches Its
  Tempering Temperature

14
Tempering Temperature Chart
15
Annealing
Annealing Is A Heat Treatment Process To Soften
Steel To Remove Internal Stress

• Steps For Annealing
• Heat Steel Up To The Upper Critical Temperature
  (Ac3 Chart)
• Hold Steel At This Temperature And Heat
  Thoroughly Through Out. This Is Called Soaking.
• Cool Steel Very Slowly By Removing It From The
  Furnace And Packing It In Sand Until It Reaches
  Room Temperature.

16
Case-Hardening
Case-hardening Is A Surface Only Hardening
Process. This Combines Hardness With Strength
Toughness

• Steps To Case-harden
• Usually Done With Lower Carbon Steels.
• Pack Steel In Powered Carbon
• Carburize By Heating In A Furnace At The Required
  Temperature For 8 To 12 Hours.
• Now Harden Steel With The Normal Hardening
  Method.

17
Heat Treating Review

• Why is heat treatment done?
• How is carbon content in steel related to
  hardening?
• List steps to follow for hardening.
• What is tempering why is it done?
• List the steps to follow for tempering.
• What is annealing and why is it done?
• List the steps to follow for annealing.
• What is case-hardening why is it done?
• List the steps for case-hardening.
• List 3 ways temperature is determined.