Fastener Materials & Manufacturing Flashcards

Which heat treatment process increases the surface hardness of a steel fastener while maintaining a tough core?

Answer: Case hardening

Case hardening (carburizing or nitriding) hardens only the outer layer, leaving the core ductile and tough.

What is the primary alloying element in 18-8 stainless steel fasteners?

Answer: Chromium and nickel

18-8 stainless steel contains approximately 18% chromium and 8% nickel, providing corrosion resistance.

Which fastener manufacturing process involves forcing wire through a die to reduce its diameter?

Answer: Drawing

Drawing pulls wire through a die to reduce cross-sectional area and produce the correct diameter for fastener blanks.

A Grade 8 hex bolt is made from which type of steel?

Answer: Medium-carbon alloy steel, quenched and tempered

SAE Grade 8 bolts are made from medium-carbon alloy steel that is quenched and tempered to achieve high strength.

What manufacturing defect occurs when the grain flow in a fastener head is not continuous with the shank?

Answer: Cold shut

A cold shut occurs when two metal streams meet without fully fusing during forming, creating a discontinuity in the grain flow.

Which process is used to produce threads on hardened fasteners where rolling cannot achieve the required surface hardness?

Answer: Thread grinding

Thread grinding uses abrasive wheels to cut precise threads in very hard materials where rolling or cutting would be impractical.

What is the purpose of the phosphate coating commonly applied to steel fasteners?

Answer: Improve paint adhesion and temporary corrosion protection

Phosphate coatings create a porous crystalline layer that improves paint adhesion and provides temporary corrosion protection.