Improving remanence in magnet steels Residual magnetism (remanence) in steel magnets is most increased by adding which alloying element?

Introduction / Context:
Designing steels for permanent magnets focuses on high remanence and coercivity. Specific alloying elements shift magnetic properties via domain pinning, anisotropy, and saturation magnetization.

Given Data / Assumptions:

• Permanent magnet application.
• Goal: maximize residual magnetism after magnetization.
• Candidate alloying additions: Ni, Co, W, Cr.

Concept / Approach:
Cobalt is the classical addition for increasing remanence and energy product. Alloys like Alnico contain substantial cobalt precisely for this reason. Other elements serve different roles: nickel favors austenite/soft magnetic behavior; chromium aids corrosion resistance; tungsten aids hot hardness.

Step-by-Step Solution:
Match property (remanence) to alloy addition → cobalt.Cross-check against industrial magnet alloy compositions with high Co content.Confirm alternatives do not prioritize remanence to the same degree.

Verification / Alternative check:
Property charts for hard-magnetic alloys list higher Br with increased Co percentages.

Why Other Options Are Wrong:

• Nickel: more aligned with soft magnetic materials and toughness improvements.
• Tungsten: mechanical strength; not a principal factor for remanence.
• Chromium: corrosion resistance; limited effect on remanence.

Common Pitfalls:

• Assuming hardness-enhancing elements also maximize magnetic remanence.

Final Answer:
Cobalt