Introducing nitrogen into steel affects it by___________________?
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Answer: A. Makes it brittle
Explanation
Interstitial nitrogen atoms pin dislocation movement within the iron crystal lattice of the steel. This restriction of plastic flow causes strain aging, which significantly increases hardness and tensile strength. Consequently, the restricted dislocation motion robs the steel of its ability to deform, making it brittle. Nitrogen can dissolve interstitially in ferrite, leading to precipitation hardening over time at room temperature. Strain aging results in increased yield strength, reduced ductility, and pronounced notch sensitivity. Steelmaking processes generally aim to control and minimize harmful dissolved nitrogen concentrations.
Structural steels must avoid excessive nitrogen pickup during melting to prevent unexpected brittle failures. Brittle materials fracture suddenly without significant plastic deformation when subjected to impact loads. Controlled nitriding is sometimes used intentionally on component surfaces, but bulk nitrogen embrittlement is avoided. Making steel brittle is an accurate effect, but dismissing it as entirely desirable is dangerously incorrect. While strength increases, the accompanying loss of ductility makes nitrogen contamination undesirable for most uses. Stating that nitrogen is universally beneficial ignores its severe embrittlement drawbacks in bulk steel.
- Subject
- Engineering
- Category
- Chemical Engineering
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- —
- Difficulty
- medium
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