What primary metallurgical factor controls the hardness of carbon steel _____________________?
Show answer Hide answer
Answer: E. shape of carbides and their distribution in iron
Explanation
Carbon steel hardness is fundamentally determined by the microstructural distribution of iron carbides. Features such as cementite morphology, grain size, and spacing dictate resistance to dislocation movement. Heat treatment alters these carbide structures, directly controlling the final hardness and strength of the steel. Carbon dissolves in iron crystal lattices to form interstitial solid solutions and carbide precipitates. Martensite formation during quenching creates a supersaturated hard microstructure in tool steels. Metallurgists analyze phase diagrams to understand how carbon content affects steel microstructure.
Toolmakers manipulate carbide distribution through hardening and tempering to achieve wear resistance. Structural steels are designed with specific microstructures to balance strength, ductility, and weldability. Microscopic examination of steel samples ensures quality control in industrial manufacturing plants. Option A mentions carbon percentage, but the actual physical hardness depends on carbide shape and distribution. Option B focuses on alloying elements, which modify hardenability rather than acting as the sole control. Option C describes heat treatment processes, which are methods to achieve the underlying carbide structures.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. How does the mean effective pressure of a diesel cycle with a fixed compression ratio respond to a larger cut-off ratio_________________?
Show answer Hide answer
Answer: A. increase
For a diesel cycle operating at a fixed compression ratio, increasing the cut-off ratio increases thermal energy added. Adding more heat during the constant pressure combustion process raises the resulting cycle mean eff...
Q2. In a petrol engine, M.E.P. initially rises with air-fuel ratio before dropping; within what mixture zone does maximum M.E.P. occur________________?
Show answer Hide answer
Answer: C. rich mixture
Mean effective pressure represents the theoretical constant pressure acting during a power stroke to produce measured engine work. As the air-fuel mixture becomes richer, flame propagation speed and combustion pressure i...
Q3. By what means can the machinability rating of steel be improved___________________?
Show answer Hide answer
Answer: B. phosphorous, lead and sulphur
Machinability of steel is enhanced by adding free-machining additives such as sulfur, phosphorus, and lead, which promote chip breakage. These alloy additions form microscopic inclusions that interrupt continuous chip fo...
Q4. What thermodynamic effect accompanies an increase in fluid pressure _________________?
Show answer Hide answer
Answer: B. raises the boiling point of a liquid
Increasing external pressure on a liquid raises its boiling point because higher temperatures are required for vapor pressure to equal ambient pressure. Molecules require more thermal energy to escape into the gas phase...
Q5. Which additive acts as the most effective grain growth inhibitor when mixed in minute amounts__________________?
Show answer Hide answer
Answer: B. vanadium
Vanadium forms extremely stable carbides and nitrides that precipitate out along grain boundaries during steel processing. These finely dispersed precipitates physically pin the grain boundaries, preventing them from mig...
Q6. How does the latent heat of steam at elevated pressures compare to its value at standard atmospheric pressure__________________?
Show answer Hide answer
Answer: A. less
At elevated operating pressures, the latent heat of vaporization of steam is lower than its value at standard atmospheric pressure. As system pressure rises toward the critical point, the energy required to vaporize wate...