Question

11.35 briefly describe the simplest heat treatment procedure that would be used in converting a 0.76 wt% c steel from one microstructure to the other, as follows: (a) martensite to spheroidite (b) spheroidite to martensite (c) bainite to pearlite (d) pearlite to bainite (e) spheroidite to pearlite (f) pearlite to spheroidite (g) tempered martensite to martensite (h) bainite to spheroidite

Answer 1

The simplest heat treatment procedures for converting a 0.76 wt% C steel from one microstructure to another involve heating and cooling the steel under specific conditions. Each conversion requires different temperatures and holding times to achieve the desired microstructure. For example, to convert martensite to spheroidite, the steel is heated slightly below the eutectoid temperature and held for a specific time. On the other hand, to convert spheroidite to martensite, the steel is rapidly cooled through quenching.

Step-by-step explanation:

The simplest heat treatment procedures for converting a 0.76 wt% C steel from one microstructure to another are as follows:

1. (a) To convert martensite to spheroidite, the steel is heated to a temperature slightly below the eutectoid temperature and held for a specific time. This allows carbon diffusion and the formation of spheroidite.
2. (b) To convert spheroidite to martensite, the steel is rapidly cooled by quenching in a suitable medium, such as water or oil. This suppresses carbon diffusion, leading to the formation of martensite.
3. (c) To convert bainite to pearlite, the steel is heated to a temperature slightly above the eutectoid temperature and held until the transformation is complete. This allows the decomposition of bainite into ferrite and cementite.
4. (d) To convert pearlite to bainite, the steel is heated to a temperature below the eutectoid temperature and held for a specific time. This allows the transformation of pearlite into bainite.
5. (e) To convert spheroidite to pearlite, the steel is heated to a temperature slightly below the eutectoid temperature and held for a specific time. This allows the decomposition of spheroidite into ferrite and cementite.
6. (f) To convert pearlite to spheroidite, the steel is heated to a temperature slightly above the eutectoid temperature and held until the transformation is complete. This allows the formation of spheroidite from pearlite.
7. (g) To convert tempered martensite to martensite, the steel is heated to a temperature slightly below the martensite start temperature and held for a specific time. This eliminates the tempering effect and allows the reformation of martensite.
8. (h) To convert bainite to spheroidite, the steel is heated to a temperature slightly below the eutectoid temperature and held for a specific time. This allows the decomposition of bainite into ferrite and cementite, followed by the formation of spheroidite.