ENT 244 Quiz 1 (GROUP 1) Question 1 Design a heat-treating cycle for carbon steel, including temperature and exposure times, to produce (a) Pearlite – martensite steels (b) Bainite – martensite steels Question 2 A load of 85,000 N is applied to a cylindrical specimen of a steel alloy (displaying the stress–strain behavior shown in Figure below) that has a cross-sectional diameter of 20 mm. (a) Will the specimen experience elastic and/or plastic deformation? Why? (b) If the original specimen length is 260 mm, how much will it increase in length when this load is applied?
Design a heat-treating cycle for carbon steel, including
temperature and exposure times, to produce
(a) Pearlite martensite steels
(b) Bainite martensite steels
Question 2
A load of 85,000 N is applied to a cylindrical specimen of a
steel alloy (displaying the stressstrain
behavior shown in Figure below) that has a cross-sectional
diameter of 20 mm.
(a) Will the specimen experience elastic and/or plastic
deformation? Why?
(b) If the original specimen length is 260 mm, how much will it
increase in length when this load is
applied?
ENT 244 ANSWER Q 1) The heat-treat cycle for these conditions
can be obtained from Fig. 4.17c. For part (a), it is desired to
produce a pearlite-martensite steel, so it is important that the
cooling rate be maintained between 140_ and 35_C/s when cooling the
material from the eutectoid temperature. Such a cooling rate can be
achieved with a salt or oil quench, where the bath temperature will
determine the cooling rate and the ultimate percentage of pearlite
and martensite. For part (b), it is desired to have bainite, which
forms under very rapid cooling (see the discussion on p. 112). Thus
the two heat-treat cycles desired can be sketched as shown
below.
