1. Forging new generations of engineers
Heat Treating Metals
Principles of EngineeringTM
Lesson 6.3 – Production Processes
Forging new generations of engineers
Project Lead The Way, Inc.
Copyright 2007

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
Heat Treating Metals
Principles of EngineeringTM
Lesson 6.3 – Production Processes
Furnace Temperature Control
Celsius Degrees On Inside
Scale
Fahrenheit Degrees
On Outside
Project Lead The Way, Inc.
Copyright 2007

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 No Heat Treating
Medium-carbon Some Hardening
High-carbon 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 Steps For 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 Steps For 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 Steps To Case-harden
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.