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Q91
(NDA-II/2023)
Science & Technology › Basic Science (Physics, Chemistry, Biology)
Official Key
Which one of the following metal is NOT an essential component in stainless steel ?
Explanation
Stainless steel is a corrosion-resistant alloy where Iron serves as the base metal. The most critical alloying element is Chromium (minimum 10.5%), which forms a passive layer of chromium oxide on the surface, preventing rust and corrosion. Nickel is also a common essential component used to enhance corrosion resistance, ductility, and the alloy's crystalline structure.
- Iron: The primary constituent of steel.
- Chromium: Essential for the "stainless" property.
- Nickel: Essential for specific grades (like 300 series) to improve stability and resistance.
Tin (Option D) is NOT an essential component. In metallurgy, tin is generally considered an impurity or residual element in steel production because it can cause "hot shortness" (brittleness during high-temperature processing). Therefore, it is intentionally kept at very low levels and is not part of the standard stainless steel composition.
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