1. On the practice exam from last year, question 6 relating to the Jominy curves. The problem states 0.45" hardening depth. In your solution, you used a distance of 6/16" (0.375 inch). I don't understand why.
After about 6/16" in Jominy bar, 8645 is no longer completely MAR. In problem want completely MAR to 0.45" depth.
2. Homework problem set 2, number one. What is the temperature that AUS first begins to transform in an Fe-0.35C alloy? Is it 25 degrees above the A3 line, which we use for making AUS, or would it be the A3 line which separates the AUS and AUS + FE range?
What phase or phases are present at 25 degrees above the A3? If you answer only AUS, then there is no FE. 25 degrees above the A3 would be a good austenitizing temperature, though, because it keeps you far enough away from the A3 where ........ starts to form.
3. Homework problem set 2, number three. The required transformation temperature for a eutectoid steel to attain hardness of : RC 38. Do we just find RC 38 on the chart and read across to find the temperature on the other side of the chart?
Yes. The hardness of the transformation product is dependent upon the transformation temperature.
4. Homework problem set 2, number four. The problem states that the metal has been heated to 800 degrees for one hour. Is this one hour used to find the end result, or do we disregard this "one hour" and argue that the hour was used to make sure the metal was being prepared for the heat treatment process that follows?
Yes to the latter. You are to assume that 1 hr is the time necessary to completely austenitize the piece.