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Hardness of steel depends upon the amount of
- a)Pearlite
- b)Ferrite
- c)Cementite
- d)Martensite
Correct answer is option 'D'. Can you explain this answer?
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Hardness of steel depends upon the amount ofa)Pearliteb)Ferritec)Ceme...
The maximum hardness of a steel is a function of its Carbon content. It increases as the percentage of carbon increases.
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Cementite: Cementite or Iron Carbide has the chemical formula Fe3C and contains 6.67% carbon by weight. It is the hardest structure that appears in the iron-carbon equilibrium diagram. Cementite has an orthorhombic crystal structure and is extremely hard and brittle as compared to austenite and ferrite.
Martensite: It is a metastable phase of steel formed by the transformation of austenite below 320°C. Martensite is an interstitial supersaturated solid carbon solution in α – Iron and has a body-centred tetragonal lattice. It has a carbon content of up to 2% and is extremely hard and brittle. It is a product of rapid cooling (quenching) and possesses an acicular or needle-like structure.
The hardness of steel depends upon the amount of cementite. Martensite was obtained after hardening treatment of steel.
Steels with low carbon content do not respond appreciably to hardening treatment because the main constituent is soft ferrite. If hypo-eutectoid steel is cooled rapidly, martensite is formed.
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Hardness of steel depends upon the amount ofa)Pearliteb)Ferritec)Ceme...
Hardness of steel depends upon the amount of Martensite
Steel is an alloy of iron and carbon, and its hardness is primarily determined by the amount of martensite present in the microstructure. Martensite is a hard, brittle phase that forms when steel is rapidly cooled from a high temperature.
Explanation:
When steel is heated to a high temperature and then cooled slowly, the carbon atoms have enough time to diffuse and form a softer phase called ferrite. Ferrite has a relatively low carbon content and is relatively soft compared to other phases in steel.
On the other hand, when steel is rapidly cooled, the carbon atoms do not have enough time to diffuse and form ferrite. Instead, they become trapped in the crystal lattice of the iron, causing the formation of martensite. Martensite has a high carbon content and is extremely hard and brittle.
The presence of martensite in the microstructure of steel increases its hardness. The greater the amount of martensite, the harder the steel will be. This is because the high carbon content of martensite leads to a distortion of the crystal lattice, making it more difficult for dislocations to move through the material. As a result, martensitic steel is more resistant to deformation and has a higher hardness.
Other Phases:
While martensite is the primary phase that determines the hardness of steel, other phases can also have an impact. For example:
- Pearlite: When steel is cooled slowly, pearlite forms. It consists of alternating layers of ferrite and cementite. Pearlite is relatively soft and does not contribute significantly to the hardness of steel.
- Cementite: Cementite is a hard and brittle phase that contains a high concentration of carbon. It forms during the cooling of steel, but its presence is typically limited. Therefore, it does not have a significant effect on the overall hardness of steel.
Overall, the amount of martensite present in the microstructure of steel is the primary factor that determines its hardness. Other phases such as pearlite and cementite may be present, but their contribution to hardness is minimal compared to martensite.
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Hardness of steel depends upon the amount ofa)Pearliteb)Ferritec)Cementited)MartensiteCorrect answer is option 'D'. Can you explain this answer?
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Hardness of steel depends upon the amount ofa)Pearliteb)Ferritec)Cementited)MartensiteCorrect answer is option 'D'. Can you explain this answer? for SSC 2024 is part of SSC preparation. The Question and answers have been prepared according to the SSC exam syllabus. Information about Hardness of steel depends upon the amount ofa)Pearliteb)Ferritec)Cementited)MartensiteCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for SSC 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Hardness of steel depends upon the amount ofa)Pearliteb)Ferritec)Cementited)MartensiteCorrect answer is option 'D'. Can you explain this answer?.
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