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Temperature Time Transformation Diagram (TTT Diagram)
- 1. OmarSiddiqi (MM-004) SaadArif (MM-026) Daniyal Ahmed (MM-033) Moiz Ullah Baig (MM-036 ) Materials Engineering Department
- 5. Homogeneous Nucleation &Energy Effects
- 6. SI-Solid Surface SL-Solid Liquid IL-Liquid Surface
- 9. Salt bath Ifor austenitisation of eutectoid steel Austenitisation temp. of eutectoid is 723 deg. C
- 10. Bath II atlow-temperature salt- bath for isothermal heat treatment. For Pearlite between 705-540 deg. C For Bainite between 540-230 deg. C
- 13. t1 t3t2 t4t5 MF, Martensite finish temperature M50,50% Martensite MS, Martensite start temperature Metastable austenite +martensite Martensite %ofPhase 0 100 Temperature Log time Hardness Ae1 T2 T1 50% T2T1 Pearlite Fine pearlite Upper bainite Lower bainite 50% very fine pearlite + 50% upper bainite At T1, incubation period for pearlite=t2, Pearlite finish time =t4 Minimum incubation period t0 at the nose of the TTT diagram, t0 MS=Martensite start temperature M50=temperature for 50% martensite formation MF= martensite finish temperature
- 14. Ferrite + Cementitein lamellae AA
- 17. MF M50 MS Metastable γ +M M Temperature Log time Hardness Ae1 α+CP α+P FP UB LB FP + UB γ=austenite α=ferrite CP=coarse pearlite P=pearlite FP=fine pearlite UB=upper Bainite LB=lower Bainite M=martensite MS=Martensite start temperature M50=temperature for 50% martensite formation MF= martensite finish temperature Ae3 t0 Metastable γ 17
- 18. M50 MS Metastable γ Metastable γ+ M Temperature Log time Hardness Ae1 Fe3C+CP Fe3C+P Fe3C+FP UB LB very FP +UB Aecm t0 γ=austenite CP=coarse pearlite P=pearlite FP=fine pearlite UB=upper Bainite LB=lower Bainite M=martensite MS=Martensite start temperature M50=temperature for 50% martensite formation 18
- 21. 21 4340 Steel withalloying elements Ni, Cr and Mo
- 22. MF M50 MS Metastable γ +M M Temperature,T Log(time, t) Hardness Ae1 α+CP α+P FP UB LB 50% FP + 50% UB γ=austenite α=ferrite CP=coarse pearlite P=pearlite FP=fine pearlite UB=upper Bainite LB=lower Bainite M=martensite MS=Martensite start temperature M50=temperature at which 50% martensite is obtained MF= martensite finish temperature Ae3 Metastable γ For finer austenite 22
- 23. • IT heattreatment are not the most practically feasible to perform • IT Curves are shifted to longer times and lower temperatures • Bainite will not form through CCT
- 25. CC1: Slow cooling(conventional annealing) CC2: Isothermal annealing CC3: Normalizing CC4: Slow oil quenching CC5: Fast oil quenching CC6: Fast water quenching CC7: Critical cooling Rate CC8: Interrupted quenching