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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.

MACRO SECTION


Reporting Results:
  1. Material.
  2. Welding process.
  3. Specimen identification.
  4. Sentencing standard.
  5. Thickness.
  6. Geometric flaws - type, size and location.
  7. Internal flaws - type, size and location.
  8. Parent metal flaws - type, size and location.
  9. Accept or reject, to standard, for each flaw.   
Comparison of macro section and micro section:

                                                                       MACRO                                            MICRO

Magnification                                                  x 10                                                 x 1000

Finish                                                            600 grit                                    1 micron (high level polish)

Features/ defects                                     cracks, slag, LOF, etc.                        inter granular structure

Uses                                                   procedure/welder qualification              research/failure analysis

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