Metallurgy & Quality Control — Welder (456A) Practice Questions

Free Metallurgy & Quality Control practice questions

1. 1.The Heat Affected Zone (HAZ) is:

   • A.The weld itself
   • B.The base metal adjacent to the weld that was heated enough to change its properties but not melted✓
   • C.The filler metal
   • D.The shielding gas area

   Why: HAZ: base metal properties change from welding heat. In carbon steel: can form martensite (hard, brittle) if cooled too fast. Preheat and controlled cooling mitigate HAZ issues.

2. 2.Liquid penetrant inspection (PT) detects:

   • A.Internal defects
   • B.Surface-breaking defects: cracks, porosity, and pin holes open to the surface✓
   • C.Subsurface defects
   • D.Only magnetic defects

   Why: PT: apply penetrant (red/fluorescent), dwell, clean surface, apply developer (white). Penetrant trapped in surface defects bleeds out, creating visible indications. Works on all materials.

3. 3.A fillet weld throat measurement is:

   • A.The leg size
   • B.The shortest distance from the root to the face of the weld✓
   • C.The weld width
   • D.The base metal thickness

   Why: Theoretical throat = 0.707 × leg size (for equal-leg fillet). The throat determines the weld's strength. Measured with fillet weld gauges.

4. 4.Ultrasonic testing (UT) of welds uses:

   • A.X-rays
   • B.High-frequency sound waves that reflect from internal defects✓
   • C.Magnetic fields
   • D.Dye penetrant

   Why: UT: sound waves travel through material and reflect from discontinuities. Portable, no radiation hazards, immediate results. Can measure depth and size of defects. Requires skilled operators.

5. 5.Preheating temperature for welding is measured:

   • A.At the weld joint
   • B.75-100mm (3-4") from the joint edge on the base metal to ensure through-thickness heating✓
   • C.At the electrode
   • D.On the fixture

   Why: Measure preheat 75mm from the joint: ensures the metal is heated through-thickness, not just surface-heated. Use temp sticks, contact pyrometer, or thermocouple.

6. 6.Weld joint types include:

   • A.Only butt joints
   • B.Butt, lap, T-joint, corner, and edge joints — each suited to different applications✓
   • C.Only fillet joints
   • D.Only groove joints

   Why: Five basic joint types: butt (aligned), lap (overlapping), T (perpendicular), corner (90° edge), edge (parallel edges). Each uses different weld types (groove, fillet, etc.).

7. 7.Charpy V-notch testing measures a weld's:

   • A.Tensile strength
   • B.Impact toughness (resistance to sudden fracture) at a specific temperature✓
   • C.Hardness
   • D.Ductility only

   Why: Charpy test: a notched specimen is struck by a pendulum at a specified temperature. Measures energy absorbed before fracture. Critical for low-temperature applications (pipeline, structural).

8. 8.Dilution in a weld refers to:

   • A.Adding water
   • B.The amount of base metal melted into the weld deposit, changing its composition✓
   • C.Reducing filler metal
   • D.Cleaning the joint

   Why: Dilution = % of weld deposit that comes from base metal. Important for: stainless-on-carbon joints, hardfacing, and clad overlays where base metal contamination affects properties.

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