AME 2 Q6

C. Hardening to increase wear resistance, followed by tempering to improve toughness.

A crankshaft undergoes a two-step heat treatment process:

1. Hardening: This increases the surface hardness of the crankshaft, making it resistant to wear and tear from high loads and friction.
2. Tempering: This process follows hardening to reduce brittleness and improve toughness, preventing the crankshaft from fracturing under stress.

This combination of hardening and tempering provides the optimal balance of hardness, strength, and toughness required for a crankshaft.

A. Annealing to improve machinability, followed by hardening to increase strength.

This sequence is incorrect because annealing softens the metal, which is counterproductive to the goal of increasing strength for a crankshaft.

B. Normalizing to refine grain structure, followed by tempering to improve toughness. Normalizing is a step in the right direction, but tempering is typically done after hardening, not normalizing.  

1. Tempering (metallurgy) - Wikipedia

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D. Carburizing to increase surface hardness, followed by quenching to improve core strength. Carburizing increases surface hardness, but quenching is done immediately after heating to achieve the hard surface, not after carburizing.

The correct sequence is hardening followed by tempering to achieve the desired combination of surface hardness and core toughness for a crankshaft.

A. Annealing to relieve stresses and improve ductility.  

1. Annealing vs. Stress Relieving Heat Treatment: What's the Difference? - Paulo

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A used copper washer would likely have internal stresses from being deformed during installation and removal. Annealing would soften the copper, relieving these stresses and making it more pliable for reuse.

Why the other answers are incorrect:

• B. Hardening to increase strength and wear resistance. Hardening is not suitable for a used copper washer as it would make it brittle and prone to cracking.
• C. Carburizing to increase surface hardness. Carburizing is a process for steel, not copper.  
  1. Carburizing - Wikipedia

  

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• D. No heat treatment is necessary. While a new copper washer might not require heat treatment, a used one often has internal stresses which can be relieved through annealing.

Annealing is the most suitable process for a used copper washer to restore its ductility and remove internal stresses.

A. Annealing to improve ductility, followed by hardening to increase strength.

Valve springs undergo a two-step heat treatment process:

1. Annealing: This softens the wire material, making it easier to coil into the desired spring shape.  
   1. Understanding the Difference Between Annealing and Tempering

   

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2. Hardening: This increases the strength and elasticity of the spring, enabling it to withstand repeated cycles of compression and extension.

This combination of processes ensures the spring has the necessary properties to perform its function effectively.

Why the other answers are incorrect:

• B. Normalizing to refine grain structure, followed by tempering to improve toughness. While normalizing is a heat treatment process, it's not typically used for valve springs. The focus is on annealing and hardening for these components.
• C. Hardening to increase wear resistance, followed by tempering to improve toughness. This sequence is correct for many components, but not for valve springs. Valve springs require high ductility to withstand repeated cycles.
• D. Patenting to increase ductility, followed by cold working to increase strength. Patenting is a specific heat treatment process not typically used for valve springs. Cold working would increase strength but decrease ductility, which is undesirable for a valve spring.  
  1. Annealing to Increase Metal Ductility - Industrial Metallurgists

  

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Annealing improves ductility for coiling, and hardening provides the necessary strength and elasticity for spring action.