1 / 18

Hardenability

Hardenability. center cools slowly. surface cools rapidly. Problem: Suppose want to full harden a shaft – i.e., make MAR all the way through shaft. Hardenability. So - this could happen:. Hardenability. Solution to problem: increase quench rate.

Download Presentation

Hardenability

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Hardenability center cools slowly surface cools rapidly Problem: Suppose want to full harden a shaft – i.e., make MAR all the way through shaft

  2. Hardenability So - this could happen:

  3. Hardenability Solution to problem: increase quench rate But rapid quenching leads to distortion & cracking Generally quench as gently as possible

  4. Hardenability So….is there a solution?? OK, how to do that? What controls position of TTT curves?

  5. Hardenability So….is there a solution?? OK, how to do that? What controls position of TTT curves? a. % C – more C to move…slower P growth b. add alloy elements…slows C diffusion c. increase AUS grain size. P nucleates on AUS grain boundaries. Increases diffusion distance

  6. Hardenability

  7. Hardenability

  8. Hardenability Shift curves to right: Mn Mo Cr V Nb Si Ni W

  9. Tempering Fresh MAR too brittle - infrequently used Brittle materials can be used in compression Ex: fresh MAR in ball bearings

  10. Martensite (MAR)

  11. Tempering Tempering conditions 200°C < T < 700°C days sec What happens? carbide formation starts - very fine closely spaced (makes material harder) carbon depletion in MAR (makes material softer) net change about 0

  12. Tempering Tempering does not form P - get discontinuous particles

  13. Tempering • What else can happen? stress relief carbide formation transition Fe carbides (not Fe3C) alloy carbides (ex: Cr7C3, Mo6C, VC) • start FE formation

  14. Austenitizing • Hypoeutectoid steels: about 25°C above a3 • no FE

  15. Austenitizing • Hypereutectoid steels: betwn a3 & acm • undissolved carbides present - not • particularly detrimental

  16. Tempering temperature/time • Depend upon desired props, application Low T gives high hardness, low toughness - wear resistance Hi T gives high toughness, reduced hardness

  17. Types of steels Plain carbon steels alloy steels Low carbon steels high carbon steels Stainless steels 420 13Cr-0.15C 440A 17Cr-0.5Ni-0.7C 440C 17Cr-0.5Ni-1.2C 405 13Cr-0.5Ni-0.08C 430 16Cr-0.5Ni-0.12C 304 19Cr-10Ni-0.08C 304L 19Cr-10Ni-0.03C 316 17Cr-12Ni-0.08C 420 440A 440C 405 430 304 304L 316 420 13Cr-0.15C cutlery 440A 17Cr-0.5Ni-0.7C cutlery 440C 17Cr-0.5Ni-1.2C ball bearings 405 13Cr-0.5Ni-0.08C machine parts 430 16Cr-0.5Ni-0.12C acid tanks 304 19Cr-10Ni-0.08C food equipment 304L 19Cr-10Ni-0.03C food equipment 316 17Cr-12Ni-0.08C chemical tanks 420 13Cr-0.15C 230ksi(ht treated) 440A 17Cr-0.5Ni-0.7C 260ksi(ht treated) 440C 17Cr-0.5Ni-1.2C 285ksi(ht treated) 405 13Cr-0.5Ni-0.08C 60ksi(annealed) 430 16Cr-0.5Ni-0.12C 65ksi(annealed) 304 19Cr-10Ni-0.08C 85ksi(annealed) 304L 19Cr-10Ni-0.03C 80ksi(annealed) 316 17Cr-12Ni-0.08C 85ksi(annealed)

  18. Types of steels Stainless steels

More Related