Special steels — name of the 36% nickel iron alloy with ultra-low thermal expansion A steel alloy containing approximately 36% nickel is commonly known as:

Introduction / Context:
Certain iron–nickel alloys exhibit near-zero thermal expansion over a wide temperature range. These are critical for precision instruments, clocks, measuring tapes, and bimetallic thermostats. The most famous composition is around 36% nickel.

Given Data / Assumptions:

• Composition is about 36% Ni with balance iron and minor additions.
• Application requires dimensional stability under temperature changes.

Concept / Approach:
The 36% nickel iron alloy is known as Invar. Its exceptionally low coefficient of thermal expansion arises from magneto-volume effects that counter normal lattice expansion. This property differentiates it from stainless steels (which are corrosion-resistant), high-speed steels (tool steels), and generic heat-resisting steels.

Step-by-Step Solution:
Associate 36% Ni with the trade name: Invar.Recall characteristic: ultra-low thermal expansion, used in precision components.Select the correct option: invar.

Verification / Alternative check:
Materials handbooks list Invar 36 with linear thermal expansion roughly one tenth that of carbon steel over room-to-moderate temperature ranges.

Why Other Options Are Wrong:

• Stainless steel: identified by chromium content for corrosion resistance, not low expansion.
• High-speed steel: tool steel class for cutting tools.
• Heat-resisting steel: a broad category, not the specific low-expansion alloy.
• Hadfield steel: high-manganese austenitic steel, unrelated to low expansion.

Common Pitfalls:
Confusing corrosion-resistant stainless grades with low-expansion alloys; they serve very different engineering purposes.

Final Answer:
invar