Question

Season-cracking of brass can be prevented by cold-working at

• A. 15$^\circ$C
• B. 100$^\circ$C
• C. 300$^\circ$C
• D. 550$^\circ$C

Hint:

Season cracking in brass is mainly prevented by removing residual stresses through stress-relief heating at about 300$^\circ$C.

Answer 1

The Correct Option is C

The four choices span a wide temperature range, and picking the right one comes down to matching the temperature to the purpose of the treatment.

1. \( 15^\circ\text{C} \) and \( 100^\circ\text{C} \): both too low, atoms cannot rearrange enough to relax the locked-in residual stress from cold working.
2. \( 300^\circ\text{C} \): right in the stress-relief annealing window for brass, high enough to relax internal stress but low enough to keep the cold-worked strength intact.
3. \( 550^\circ\text{C} \): too high, this recrystallizes the grains and undoes the cold work rather than just relieving stress.

So cold working followed by treatment at \( 300^\circ\text{C} \) prevents season cracking.

Answer 2

Metallurgical heat treatments of cold-worked metals fall into three broad temperature bands, and identifying which band each option belongs to settles the question directly.

1. \( 15^\circ\text{C} \): this is simply ambient temperature, no heat treatment is happening at all, so residual stress is untouched.
2. \( 100^\circ\text{C} \): this sits in the low-temperature aging band, useful for some precipitation effects in certain alloys but not for relieving cold-work stresses in brass.
3. \( 300^\circ\text{C} \): this sits in the stress-relief band, below the recrystallization temperature of brass, where residual stresses dissipate but the cold-worked grain structure and hardness are preserved.
4. \( 550^\circ\text{C} \): this sits in the recrystallization/full-anneal band for brass, where new strain-free grains form and the cold-worked properties are erased.

Since only the stress-relief band actually addresses the cause of season cracking without destroying the cold work, \( 300^\circ\text{C} \) is the correct choice.

Therefore, the correct answer is \( 300^\circ\text{C} \).