456A Weld Quality Inspection, Testing & Occupational Safety 2

Question 1

What is a 'guided bend test' and what does it evaluate in a welded joint?

Accepted Answer

A test coupon is bent around a mandrel of specified diameter; evaluates ductility and soundness of the weld and HAZ by exposing internal defects as cracks on the bent surface

Answer

Guided bend tests (face bend, root bend, and side bend) are used for welding procedure qualification and welder performance qualification. The specimen is bent through 180° around a mandrel of diameter specified by the code (e.g., 4× base metal thickness). Any crack or open discontinuity above 3 mm constitutes failure. The test evaluates fusion quality and ductility of the weld/HAZ — defects open up during bending and become visible.

Question 2

What does a 'macro-examination' (macro-etch) of a weld cross-section reveal?

Accepted Answer

The weld cross-sectional profile showing fusion line geometry, pass sequence, HAZ size, root penetration, and any gross discontinuities visible at low magnification after etching

Answer

A macro-examination involves cutting a cross-section of the weld, grinding and polishing the surface, then etching with acid (typically 5–15% nitric in alcohol for steel) to reveal the weld structure. It shows: weld pass sequence and geometry, fusion line shape, HAZ extent, root penetration, and any cracks, porosity clusters, lack of fusion, or slag inclusions visible at low power (up to 10×). It is a required test in many procedure qualifications.

Question 3

What is the acceptance criterion for undercut in structural welds under CSA W59 for statically loaded structures?

Accepted Answer

Undercut depth not exceeding 1 mm (1/32 in.) for welds transverse to the primary stress direction; 2 mm for welds parallel to the primary stress

Answer

CSA W59 (following AWS D1.1) allows limited undercut in statically loaded structures: up to 1 mm depth for welds transverse to tensile stress and up to 2 mm for welds parallel to stress (where the notch is less critical). For dynamically loaded structures (Category C), undercut is more tightly limited. Undercut exceeding limits must be repaired by grinding to a smooth transition or by depositing additional weld metal.

Question 4

What is 'phased array ultrasonic testing' (PAUT) and what advantage does it offer over conventional UT?

Accepted Answer

Uses multiple piezoelectric elements electronically controlled to steer and focus the sound beam, providing real-time cross-sectional imaging (S-scan) and better defect characterization than single-element UT

Answer

PAUT uses an array of small piezoelectric elements that are electronically triggered in timed sequences to electronically steer and focus the beam without moving the probe. This generates sector scans (S-scans) showing a real-time cross-sectional view of the weld. Advantages over conventional UT: faster inspection, better defect detection and sizing, permanent digital record (data file), and the ability to inspect complex geometries. PAUT is now widely accepted by CSA Z662 and other Canadian codes.

Question 5

What is the purpose of a 'weld hardness test' (Vickers, Brinell, or Rockwell) on a procedure qualification record?

Accepted Answer

Verifies that the HAZ hardness does not exceed specified limits (e.g., 350 HV max for most carbon steel), confirming adequate toughness and resistance to hydrogen-induced cracking

Answer

Hardness testing of weld procedure qualification coupons (typically traversing from base metal through HAZ to weld metal) verifies that no excessively hard zones (martensite) were produced by the procedure. Maximum HAZ hardness limits (e.g., 350 HV for carbon steel, 250 HV for sour service per NACE MR0175) ensure adequate toughness and resistance to hydrogen-induced and sulfide stress cracking.

Red Seal Welder 456A Practice Test

Red Seal Welder 456A Practice Test

456A Weld Quality Inspection, Testing & Occupational Safety 2