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Question

Difficulty: MediumIdentifying Implied Meanings

Passage:
During the precision case-hardening of steel transmission gears, technicians pack carbonaceous powder around the components inside a sealed furnace before raising the chamber temperature to 900°C. If the furnace door seal fails and admits atmospheric air, oxygen rapidly reacts with the carbon pack, converting it into gaseous carbon dioxide before the carbon can diffuse into the iron matrix. Consequently, batches processed with a compromised door seal exhibit normal core toughness but suffer severe surface wear within the first hundred operating hours.

Statement:
Based on the passage, the presence of atmospheric air during the heating cycle prevents the outer layer of the steel gears from achieving adequate surface hardness.

Answer: Answer

Answer

True. The text logically implies that atmospheric oxygen depletes the carbon necessary for surface hardening, resulting in premature wear.
The passage states that when oxygen reacts with the carbon pack, the carbon cannot diffuse into the steel, resulting in rapid surface wear while the interior core remains unaffected. It can therefore be directly inferred that carbon diffusion is responsible for surface hardening and that oxygen ingress prevents this necessary hardening.

Step-by-Step Solution

1
Analyze the stated sequence of events during a seal failure.
Atmospheric air brings oxygen into the furnace, which reacts with carbon powder to form carbon dioxide before carbon can diffuse into the steel.
Understanding the immediate chemical consequence of air entering the chamber is necessary to trace the root cause of the defect.
2
Examine the resulting condition of the finished gears.
The core retains normal toughness, but the exterior experiences severe surface wear during early operation.
Connecting the physical failure mode specifically to the outer surface establishes what property was compromised.
3
Deduce the unstated relationship between carbon diffusion and surface hardness.
Because preventing carbon diffusion leads directly to surface wear without altering core toughness, carbon diffusion must be the mechanism that hardens the outer layer.
Identifying the implied functional role of carbon diffusion confirms that oxygen prevented proper surface hardening.

Key Concept

Inferring an unstated cause-and-effect relationship regarding material properties from contextual evidence.
Estimated Time:1m 0s
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Identifying Implied Meanings

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