Question

4.) a.) What is the cooling rate from 800°C to 500°C for a steel part with 20 % bainite? Method of MCQuoid-Ehn 9%V b.S.-M 10.43 0.41 082 0041 0.015 1.22 004 0.14 0.11 Austenitizing temp. - 880°C Grain size (AS 10-11 800 Acs (0.25° min) 700 600 500 Hardness HR 200 90 100 104 10 60 102 min 1 2 468 1624 1 2 34 6 10 b.) What is the room temperature hardness of this steel part? c.) Which microstructure do you expect (in percentage) in a steel part with 41 HRC? d.) How fast do you need to cool a steel part below Ms in order to achieve a 100 % martensitic microstructure?

Answer 1

Method of MCQuoid-Ehr 96V For 20% bainite DeltaT 800-500 Delta s 14-0 1043 041 082 0.041 0.015 1.22 004 0.14 0.11 b.S.-M 300 C 14 sec Austenitizing temp. 880°C Grain size (AS -10-11 Cooling rate 300/1421.43 Deg C/sec Aca (0.25 min) 25 B) Room temperature hardness53 HRC 80% Bain ite, 20% pearlite @ 41 HRC For 100% Martensite below Ms, cooling rate is approx 76 D) 3.676 Deg C/ sec approx (300-50)/(80-12)- Hardness HRC 10 20 30 40303 ite 90 101 60 102