Steel integrity and gases: The presence of hydrogen in steel primarily causes which detrimental effect during service or post-weld conditions?

Introduction / Context:
Hydrogen is one of the most insidious impurities in steels. Even in very small amounts, atomic hydrogen can diffuse into stressed regions and cause delayed cracking. Recognizing hydrogen embrittlement is vital for welding, heat treatment, plating, and high-strength steel applications.

Given Data / Assumptions:

• Base material: carbon or low-alloy steels.
• Hydrogen can be introduced during welding, pickling, electroplating, or service exposure.
• High-strength steels are particularly susceptible.

Concept / Approach:
Hydrogen embrittlement results from hydrogen atoms accumulating at trap sites (dislocations, inclusions, interfaces) and decohesion ahead of a crack tip. This lowers ductility and fracture toughness, leading to sudden failure under static or cyclic loads, often after a delay. Mitigation includes low-hydrogen welding consumables, preheat/interpass temperature control, and post-weld baking to diffuse hydrogen out.

Step-by-Step Solution:
Identify the key effect of hydrogen: it weakens metallic bonds locally.Correlate with observed failures: delayed cracking, brittle fracture patterns.Select the term that captures this phenomenon: embrittlement.Conclude that option “embrittlement” is correct.

Verification / Alternative check:
Practical evidence: weldments show underbead or toe cracking relieved by hydrogen bake-out or by adopting low-hydrogen procedures.

Why Other Options Are Wrong:
Reduced neutron absorption is irrelevant to mechanical integrity here.

Hydrogen does not improve weldability; it increases cracking risk.

Hydrogen does not enhance corrosion resistance or fatigue limit in steels.

Common Pitfalls:
Confusing hydrogen embrittlement with temper embrittlement (a different phenomenon related to alloy segregation).

Final Answer:
embrittlement