Macro-etch, Grain Flow, Surface Condition, Macrostructure and More
Macroscopic examination, also called macro test or macro examination, is an extension of visual examination and evaluates quality and homogeneity of the test sample indicating the flow of material during the forming or welding process. Information on macrostructural features can be used to assess internal quality, presence of hydrogen flakes, chemical segregation, hard cases, flow lines and welds. A common macro test is weld cross section examination to reveal internal discontinuities, weld profile, weld passes and sequence, extent of penetration and the quality of weld. The macrostructural properties of a weldament can then be used as a component of weld procedure qualification or welder qualification.
The Test Process
After receipt of the sample, macroscopic examination begins with the cutting, grinding and etching of the test sample. Etching is a chemical reaction on the surface of the test sample that allows viewing of the flow properties of the material. The samples can be ingots, castings, plates, bars, sheets or finished products. The macro examination is performed on the cross section, longitudinal section or through the thickness (‘Z’ direction) of the test sample. The sample is viewed with the unaided eye or at low magnification, usually no greater than 10 times. Macro-etch to ASTM E340 is the controlled surface etching of a metal or alloy sample to reveal a structure such as grain flow lines and ingot patterns that are visible at the low magnification. Grain flow lines are the resulting fiber pattern observed in a hot or cold worked material, showing the manner in which the metal flowed during the forming process.
During macroscopic examination, findings can be documented with digital imaging to provide the customer with a visual image contained in the Certified Test Report or with a digital image that can be emailed.
- Macro-etch (ASTM E340)
- Grain Flow
- Weld Qualification
- Surface Condition