Questions cover material science, heat treatment, failure analysis, welding metallurgy, corrosion, and quality control of metal components in manufacturing.
Ferrous: iron-based (steel, cast iron) for structural components, shafts, gears. Non-ferrous: aluminum, copper, titanium for lightweight structures, electrical conductors, corrosion-resistant parts. Show you know when weight, conductivity, or corrosion drives the choice.
Annealing: soften for machining. Quenching: rapid cooling to harden. Tempering: reheat after quenching to reduce brittleness. The goal is a specific hardness-toughness balance for the application.
Steps: visual inspection, fracture surface analysis (brittle vs ductile), hardness testing, chemical composition verification, microstructure examination (metallography), comparison to design spec, root cause identification. Use terms like fractography, SEM, inclusion content.
Processes: MIG, TIG, stick (SMAW), flux-core, spot welding. Different heat inputs create different HAZ (heat-affected zone) widths and microstructures. TIG is precise with low heat input; MIG is faster with more spatter. Show awareness of post-weld heat treatment needs.
Types: uniform, galvanic, pitting, crevice, stress corrosion cracking. Protection: coatings (paint, galvanizing, epoxy), cathodic protection, corrosion-resistant alloys, environmental control. Galvanic corrosion happens when two dissimilar metals contact in an electrolyte, a common design mistake.
Collect: service history, load conditions, environment, material certifications (MTRs), manufacturing records. Then proceed to physical analysis. Show you treat it as a forensic investigation: gather facts before drawing conclusions.
Methods: ultrasonic testing (UT), magnetic particle (MT), dye penetrant (PT), radiography (RT), visual (VT). Be specific: "I used UT to detect internal porosity in a weld that wasn't visible externally." NDT protects lives, so show you take it seriously.
Check: chemical composition vs spec, tensile and yield strength, elongation, Charpy impact (for toughness), hardness, heat number traceability. Show you don't just accept material: you verify it meets the design requirement before it enters production.
Common standards: ASTM A36 (structural steel), ASTM A516 (pressure vessel), SAE 4140 (alloy steel), ASTM B209 (aluminum sheet). Show you can navigate the standard to find allowable properties and testing requirements, not just name it.
Document: an NCR (Non-Conformance Report) with part number, heat number, the specific failure, test data, and a corrective action request (8D or CAPA). Clear, fact-based communication protects the company and improves supplier quality over time.
Fatigue is crack initiation and propagation under cyclic loading, below the yield strength. Prevention: remove stress concentrations (sharp corners become radii), improve surface finish, shot peening, reduce mean stress, use a material with good fatigue resistance.
A QMS means documented processes, controlled records, calibrated equipment, and a formal corrective action process. Show you see it as a tool for consistent quality, not just paperwork. IATF 16949 is critical for automotive supply chains in the U.S.
