Calculate of microstructure in a steel sample with a carbon

Calculate % of microstructure in a steel sample with a carbon content of 0.6% at 600 degree C. The A copper wire is cold drawn from an 18 mm to 13.94 mm diameter. (a) Calculate % cold work that the wire undergoes. (b) Estimate the wire\'s tensile Strength.

Solution

8) The microstructure at 600⁰ C will consists of proeutectoid ferrite(0.022% C) and perlite (0.8%C (ferrite(0.022%C) + cementite,Fe₃C(6.67%C))).

Using lever rule with a tie line on the diagram

% microstructure of proeutectoid ferrite=( 0.8 - 0.6)*100/(0.8-0.022) = 25.7%

% microstructure of pearlite = (0.6 - 0.022)*100/(0.8-.022) = 74.3%

We can also find the % total ferrite and cemntite because the ferrite is in two forms one proeutectoid ferrote and the ferrite of pearlite.

% of total ferrite = (6.67-0.6)*100/(6.67-.022) = 91.3%

% of cementite = (0.6-0.022)*100/(6.67-.022)= 8.7%

(9) Original area of cross section A_o= pi * D_o²/4 = (22/7)*18²/4=254.47 mm²

  Final area of cross section, A_f = (22/7) (13.94)²/4 = 152.62 mm²

(a) % Cold Work = (A_o - A_f)*100/A_o = (254.47-152.62)*100/254.47 = 40%

(b) from the given graph, The tensile strength of wire corresponding to 40% cold work is 325 N/mm² approx.