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During heat treatment of steel, the hardness of various structures in increasing order is
- a)martensite, fine pearlite, coarse pearlite, spheroidite
- b)fine pearlite, coarse pearlite, spheroidite, martensite
- c)spheroidite, coarse pearlite, fine pearlite, martensite
- d)martensite, coarse pearlite, fine pearlite, spheroidite
Correct answer is option 'C'. Can you explain this answer?
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Most Upvoted Answer
During heat treatment of steel, the hardness of various structures in ...
The correct answer is option 'C': spheroidite, coarse pearlite, fine pearlite, martensite.
Heat treatment of steel involves a series of controlled heating and cooling processes to alter the microstructure and properties of the material. One of the key aspects affected by heat treatment is the hardness of the steel. Different microstructures formed during heat treatment exhibit varying levels of hardness.
Now, let's discuss the hardness of various structures in increasing order during heat treatment of steel:
Spheroidite:
- Spheroidite is a microstructure formed when steel is heated to a temperature just below the eutectoid point and held at that temperature for a prolonged period of time.
- It consists of rounded or spheroid-shaped carbides embedded in a ferrite matrix.
- Spheroidite has the lowest hardness among the structures formed during heat treatment.
Coarse Pearlite:
- Coarse pearlite is a microstructure formed when steel is slowly cooled from the austenitic phase to a temperature just below the eutectoid point.
- It consists of alternating layers of ferrite and cementite.
- Coarse pearlite has a higher hardness compared to spheroidite.
Fine Pearlite:
- Fine pearlite is a microstructure formed when steel is rapidly cooled from the austenitic phase to a temperature just below the eutectoid point.
- It has a finer lamellar structure compared to coarse pearlite, with smaller ferrite and cementite layers.
- Fine pearlite has a higher hardness compared to coarse pearlite.
Martensite:
- Martensite is a microstructure formed when steel is rapidly cooled from the austenitic phase to a temperature below the martensite start temperature.
- It has a highly distorted and supersaturated structure, which gives it extremely high hardness.
- Martensite has the highest hardness among the structures formed during heat treatment.
In summary, the correct order of hardness for the structures formed during heat treatment of steel is: spheroidite (lowest hardness), coarse pearlite, fine pearlite, martensite (highest hardness). Option 'C' correctly represents this order.
Heat treatment of steel involves a series of controlled heating and cooling processes to alter the microstructure and properties of the material. One of the key aspects affected by heat treatment is the hardness of the steel. Different microstructures formed during heat treatment exhibit varying levels of hardness.
Now, let's discuss the hardness of various structures in increasing order during heat treatment of steel:
Spheroidite:
- Spheroidite is a microstructure formed when steel is heated to a temperature just below the eutectoid point and held at that temperature for a prolonged period of time.
- It consists of rounded or spheroid-shaped carbides embedded in a ferrite matrix.
- Spheroidite has the lowest hardness among the structures formed during heat treatment.
Coarse Pearlite:
- Coarse pearlite is a microstructure formed when steel is slowly cooled from the austenitic phase to a temperature just below the eutectoid point.
- It consists of alternating layers of ferrite and cementite.
- Coarse pearlite has a higher hardness compared to spheroidite.
Fine Pearlite:
- Fine pearlite is a microstructure formed when steel is rapidly cooled from the austenitic phase to a temperature just below the eutectoid point.
- It has a finer lamellar structure compared to coarse pearlite, with smaller ferrite and cementite layers.
- Fine pearlite has a higher hardness compared to coarse pearlite.
Martensite:
- Martensite is a microstructure formed when steel is rapidly cooled from the austenitic phase to a temperature below the martensite start temperature.
- It has a highly distorted and supersaturated structure, which gives it extremely high hardness.
- Martensite has the highest hardness among the structures formed during heat treatment.
In summary, the correct order of hardness for the structures formed during heat treatment of steel is: spheroidite (lowest hardness), coarse pearlite, fine pearlite, martensite (highest hardness). Option 'C' correctly represents this order.
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During heat treatment of steel, the hardness of various structures in ...
Steel can be cooled from the high temperature region at a rate so high that the austenite does not have sufficient time to decompose into sorbite or troostite.
In this case, austenite is transformed into martensite. Martensite is ferromagnetic, very hard and brittle.
So, the hardness of various structures in increasing order is:
Spheroidite → Coarse pearlite → Fine pearlite → Martensite
In this case, austenite is transformed into martensite. Martensite is ferromagnetic, very hard and brittle.
So, the hardness of various structures in increasing order is:
Spheroidite → Coarse pearlite → Fine pearlite → Martensite
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During heat treatment of steel, the hardness of various structures in increasing order isa)martensite, fine pearlite, coarse pearlite, spheroiditeb)fine pearlite, coarse pearlite, spheroidite, martensitec)spheroidite, coarse pearlite, fine pearlite, martensited)martensite, coarse pearlite, fine pearlite, spheroiditeCorrect answer is option 'C'. Can you explain this answer?
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