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VISUAL INSPECTION OF WELDING

VISUAL  INSPECTION OF WELDING

INTRODUCTION
Inspection starts with examination of the material prior to fabrication, scabs, seams, scale or other harmful surface conditions may be detected in visual inspection.

The inspector should check the following :
  • Weld preparation, dimensions and finish. 
  • Clearance dimensions of backing strips. 
  • Alignment and fit up to the pieces being welded. 
  • Verification of cleanliness. 

Visual Inspection During Welding
Visual inspection checks details of the work while welding is in progress. Among the details to be checked are :
  • Welding process. 
  • Cleaning. 
  • Preheat and inter pass temperature. 
  • Joint preparation. 
  • Filler metal. 
  • Flux or shielding gas. 
  • Chipping, grinding, or gouging. 
  • Post heating temperature and time. 
Visual Inspection After Welding
Visual inspection is useful for finished-product verification of such items as :
  • Profile irregularities of the weldment. 
  • Conformity to drawing requirements. 
  • Acceptability of welds with regard to appearance (eg: surface roughness). 
  • The presence of unfilled undercut, overlaps and cracks. 
  • Evidence of mishandling from center punch or other inspection markings or excessive grinding. 

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MACRO SECTION

MACRO SECTION Object: To examine a cross section of a weld for internal defects and soundness. Method:  A transverse section of the weld is cut out. The cross section is then visually inspected. The section is filed down from rough to smooth, then emery or wet/dry papered down to a surface finish of 600 grit. The surface is then etched in NITAL (5% - 10% nitric acid in alcohol), washed off, rinsed and dried. (Possibly a final clean with acetone and mount in Bakelite) The specimen is then inspected at up to 10-x magnification. Reporting Results: Material. Welding process. Specimen identification. Sentencing standard. Thickness. Geometric flaws - type, size and location. Internal flaws - type, size and location. Parent metal flaws - type, size and location. Accept or reject, to standard, for each flaw.    Comparison of macro section and micro section:                             ...