Answer:
<u>Option-(A)</u>
Explanation:
<u>Typical applications for the high carbon steels includes the following;</u>
It is heat treatable, relatively large combinations of mechanical characteristics. Typical applications: railway wheels and tracks, gears, crankshafts, and machine parts.
Answer:
86 mm
Explanation:
From the attached thermal circuit diagram, equation for i-nodes will be
Equation 1
Similarly, the equation for outer node “o” will be
Equation 2
The conventive thermal resistance in i-node will be
Equation 3
The conventive hermal resistance per unit area is
Equation 4
The conductive thermal resistance per unit area is
Equation 5
Since
is given as 100,
is 40
is 300
is 25
Substituting the values in equations 3,4 and 5 into equations 1 and 2 we obtain
Equation 6
Equation 7
From equation 6 we can substitute wherever there’s
with 3000L+40 as seen in equation 7 hence we obtain
The above can be simplified to be
-3000L=1.665-260
Therefore, insulation thickness is 86mm
This question is incomplete, the complete question is;
For a steel alloy it has been determined that a carburizing heat treatment of 11.3 h duration at Temperature T1 will raise the carbon concentration to 0.44 wt% at a point 1.8 mm from the surface. A separate experiment is performed at T2 that doubles the diffusion coefficient for carbon in steel.
Estimate the time necessary to achieve the same concentration at a 4.9 mm position for an identical steel and at the same carburizing temperature T2.
Answer:
the required time to achieve the same concentration at a 4.9 is 83.733 hrs
Explanation:
Given the data in the question;
treatment time t₁ = 11.3 hours
Carbon concentration = 0.444 wt%
thickness at surface x₁ = 1.8 mm = 0.0018 m
thickness at identical steel x₂ = 4.9 mm = 0.0049 m
Now, Using Fick's second law inform of diffusion
/ Dt = constant
where D is constant
then
/ t = constant
/ t₁ =
/ t₂
t₂ = t₁
t₂ = t₁
/ 
t₂ = (
/
)t₁
t₂ =
/
× t₁
so we substitute
t₂ =
0.0049 / 0.0018
× 11.3 hrs
t₂ = 7.41 × 11.3 hrs
t₂ = 83.733 hrs
Therefore, the required time to achieve the same concentration at a 4.9 is 83.733 hrs
Answer:
(a) Surface energy is greater than grain boundary energy due to the fact that the bonds of the atoms on the surface are lower than those of the atoms at the grain boundary. The energy is also directly proportional to the number of bonds created.
(b) The energy of a high-angle grain boundary is higher than that of a small-angle grain boundary because the high-angle grain boundary has a higher misalignment and smaller number of bonds than a small-angle grain boundary.
Explanation:
(a) Surface energy is greater than grain boundary energy due to the fact that the bonds of the atoms on the surface are lower than those of the atoms at the grain boundary. The energy is also directly proportional to the number of bonds created.
(b) The energy of a high-angle grain boundary is higher than that of a small-angle grain boundary because the high-angle grain boundary has a higher misalignment and smaller number of bonds than a small-angle grain boundary.