Ferrous and Nonferrous Metallurgy Fundamentals
Core concepts
Candidates should understand the iron-carbon system: carbon content distinguishes steel from cast iron, and carbon plus alloying elements control hardness, strength, and weldability. Know the basic families: carbon steels, alloy steels, stainless (chromium-bearing, corrosion resistant), tool steels, and cast irons. For nonferrous metals, know copper's conductivity and alloying with tin and zinc, aluminum's light weight and oxidation behavior, lead's density and toxicity, zinc's coating role in galvanizing, and nickel's use in stainless and superalloys.
Processing implications
Metallurgy explains why scrap is processed as it is. Copper and aluminum are sorted by alloy to preserve chemistry for remelting. Stainless grades depend on nickel and chromium content, so mixing grades destroys value. Turnings and borings have high surface area and carry oil, so they are handled separately and often briquetted. Galvanized and coated material may require special handling for emissions. Understanding melting points and oxidation helps explain loss rates in furnaces.
Traps to watch
- Assuming all stainless is identical; nickel and chromium content varies widely.
- Confusing cast iron with steel; carbon level and brittleness differ.
- Forgetting that coatings and platings (zinc, tin, paint) affect remelt chemistry.
- Believing "heavier means more valuable" - density matters, but chemistry drives price.
Worked example
Two stainless loads look alike. One is a high-nickel grade, the other a low-nickel ferritic grade. Rule of thumb: stainless value tracks nickel and chromium content, so never blend them; keep grades segregated and confirm with analysis. A blended load is priced as the lowest common grade.