1 / 10

Heat Treatment of Plain Carbon Steels

Heat Treatment of Plain Carbon Steels. Isothermal Temperature-time Transformation Diagram. Let us do an experiment Choose an eutectoid steel Heat it to the austenite phase region (800˚ C) Quench to 727 ˚ C Observe transformation g a + Fe 3 C Note time when 1% pearlite has formed

kimn
Download Presentation

Heat Treatment of Plain Carbon Steels

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. Heat Treatment of Plain Carbon Steels

  2. Isothermal Temperature-time Transformation Diagram • Let us do an experiment • Choose an eutectoid steel • Heat it to the austenite phase region (800˚ C) • Quench to 727 ˚ C • Observe transformation ga + Fe3C • Note time when 1% pearlite has formed • Note time when 99% pearlite has formed • Plot on Temp.-time transformation diagram

  3. 727ºC x x x x Pearlite Temp g+P x x x x g x x Bainite Nose g+B x x x x x x Ms g+a’ Mf a’(marteniste) time

  4. 727ºC coarse Temp g+P Pearlite fine g upper g+B Bainite lower Ms g+a’ Mf a’(martensite) time

  5. Properties of phases • Properties of pearlite • Fairly tough • Fairly ductile • Depends on size of lamellae • Properties of bainite • Tough • Structure between pearlite • and marteniste (a + Fe3C) • Properties of marteniste • Very hard HRC 45-55 • Brittle • bc tetragonal structure • Supersaturated solution of C in Fe • High residual stresses • Metastable

  6. Microstructures Coarse pearlite Fine pearlite

  7. Microstructures Upper Bainite Lower Bainite

  8. Microstructure Martensite

  9. Continuous cooling transformation diagram 727ºC Coarse:annealing (1ºC/min) in furnace Temp g+P Pearlite g Fine:normalizing(10º C/min) I air upper g+B Bainite isothermal lower Ms g+a’ Mf a’(martensite):quenching (100º C/min) in oil or water time

  10. Tempering of martensitic steels • Martensite is too brittle to serve engineering purpose • Tempering carried out to increase toughness of martensite • Carried out by reheating martenistic steel between 150-500º C • 1st stage 150-200º C a’ a”(low C martensite) + e carbide (Fe2.3C) • 2nd stage 200-350º C g bainite • 3rd stage 350-500º C a”+ e carbide a + Fe3C(tempered martensite)

More Related