(a) The hardness of a steel is often used interchangeably with its tensile strength. Why is this practice used and what is the relationship between hardness and tensile strength?
(b) In a hardenable steel, what does ‘limiting ruling section' mean?
(c) In Case Study 3 in this chapter, the microstructure of the pin, even near the surface, was mainly bainite with some ferrite. Use the continuous cooling transformation (CCT) diagram for the steel to explain the transformation kinetics it had undergone, assuming an oil quench.
(d) In (c) above, using a water quench would very likely eliminate the soft and undesirable ferrite phase, and further, water quenching would be much cheaper than an oil quench. What are the disadvantages of a water quench?