CFS Fastener Materials & Manufacturing 2 — Questions and Answers
Question 1: Which heat treatment process increases the surface hardness of a steel fastener while maintaining a tough core?
- Annealing
- Case hardening (Correct answer)
- Normalizing
- Stress relieving
Correct answer: Case hardening
Case hardening (carburizing or nitriding) hardens only the outer layer, leaving the core ductile and tough.
Question 2: What is the primary alloying element in 18-8 stainless steel fasteners?
- Molybdenum and copper
- Chromium and nickel (Correct answer)
- Titanium and vanadium
- Manganese and silicon
Correct answer: Chromium and nickel
18-8 stainless steel contains approximately 18% chromium and 8% nickel, providing corrosion resistance.
Question 3: Which fastener manufacturing process involves forcing wire through a die to reduce its diameter?
- Rolling
- Drawing (Correct answer)
- Forging
- Extrusion
Correct answer: Drawing
Drawing pulls wire through a die to reduce cross-sectional area and produce the correct diameter for fastener blanks.
Question 4: A Grade 8 hex bolt is made from which type of steel?
- Low-carbon steel
- Medium-carbon alloy steel, quenched and tempered (Correct answer)
- Austenitic stainless steel
- Martensitic stainless steel
Correct 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.
Question 5: What manufacturing defect occurs when the grain flow in a fastener head is not continuous with the shank?
- Seam
- Lap
- Cold shut (Correct answer)
- Burst
Correct answer: Cold shut
A cold shut occurs when two metal streams meet without fully fusing during forming, creating a discontinuity in the grain flow.
Question 6: Which process is used to produce threads on hardened fasteners where rolling cannot achieve the required surface hardness?
- Thread chasing
- Thread milling
- Thread grinding (Correct answer)
- Thread tapping
Correct answer: Thread grinding
Thread grinding uses abrasive wheels to cut precise threads in very hard materials where rolling or cutting would be impractical.
Question 7: What is the purpose of the phosphate coating commonly applied to steel fasteners?
- Increase tensile strength
- Improve paint adhesion and temporary corrosion protection (Correct answer)
- Increase hardness
- Reduce friction during torquing only when combined with oil
Correct answer: Improve paint adhesion and temporary corrosion protection
Phosphate coatings create a porous crystalline layer that improves paint adhesion and provides temporary corrosion protection.
CFS Fastener Materials & Manufacturing 2
Which heat treatment process increases the surface hardness of a steel fastener while maintaining a tough core?