Alloy steels — a common austenitic stainless steel composition widely used in construction hardware and kitchen equipment contains approximately which chromium and nickel percentages?

Introduction / Context:Austenitic stainless steels are prized for corrosion resistance and formability. The most ubiquitous grade family is the “18/8” composition (e.g., AISI 304), referenced by its approximate chromium and nickel content, which stabilizes the austenitic phase and provides robust passivation behavior in atmospheric and many aqueous environments.

Given Data / Assumptions:

• The question targets the iconic “18/8” stainless composition.
• Minor elements (C, Mn, Si, N, Mo) are not central to this identification.
• Percentages are approximate nominal values used in teaching.

Concept / Approach:

Chromium at about 18% forms a stable, self-healing chromium oxide passive film that confers corrosion resistance. Nickel at about 8% stabilizes austenite, improving ductility and toughness, especially at low temperatures, and aiding formability and weldability. This combination is a standard reference point for stainless steels in civil/architectural hardware, food processing equipment, and household applications.

Step-by-Step Solution:

Verification / Alternative check:

Standards and material datasheets consistently list Cr ≈ 18% and Ni ≈ 8% (ranges allowed) for AISI 304-type steels.

Why Other Options Are Wrong:

Other combinations either invert or greatly exaggerate Ni/Cr levels and do not represent the mainstream austenitic grades.

Common Pitfalls:

Confusing 18/8 (304) with molybdenum-bearing 316 (≈18% Cr, 10–12% Ni, 2–3% Mo).

Final Answer:

18% of chromuim and 8% nickel