Presented in this report are the results of stress corrosion cracking testing per ASTM G36 (Standard Practice for Performing Stress-Corrosion Cracking Tests in a. austenitic stainless steel was studied in accordance with the ASTM G The samples were unidirectional cold-rolled up to 60 and 90 percent reduction in. Revised ASTM G36 apparatus. This client had been testing stress corrosion- cracking in metal welds by clamping a QVF 2″ glass pipe fitting to his samples.
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Revised ASTM G36 apparatus
Quality Assurance Return to Corrosion Testing. Accompanying paperwork states that both types of tube were fabricated from the same heat lot of material. No preparation other than deburring and degreasing was performed on the test specimens prior to testing. The test specimens were immersed in the boiling solution and supported using the suggested ladder-back cradles. Regular examination periods for test specimen cracking were scheduled.
Both test specimens were taken off test at 8 hours for examination at low magnification.
Cracking of both test specimens was observed, and the tests y36 terminated. On the finned test specimen, cracks extended down the fins from the outer edge to the tube wall in a direction roughly normal to the tube wall; at the tube wall sstm cracks extended in a short arc both longitudinally and circumferentially, the arcs stopping before the next fin was encountered. The weld and HAZ of the finned tube appeared to have more cracks than the base metal, and the cracks appear to nearly connect from fin to fin.
Photographs of typical appearance of the cracks on both tubes are shown in Figures 1 and 2.
ASTM G36 – 94(2013)
It was decided that cracks in the bare tube could be best examined using a longitudinal cross-section, while the cracks in the finned tube could be atsm examined using a transverse cross-section. Microphotographs of the deepest cracks found on the mounted sections are shown in Figures 3 and 4.
Etching both sections did not reveal any additional crack depth as sometimes occurs in metallographic studies of stress-corrosion cracking.
Deepest crack found on longitudinal cross-section of bare tube. Deepest cracks found on transverse cross-section of finned tube. Black lines indicate the approximate location of the outer surface of the tube. Newark, Delaware USA Circumferential cracks with connecting longitudinal crack in awtm metal of bare tube.
Return to Corrosion Testing. Two 2 1-foot long pieces of 0. Test procedures conformed to the referenced ASTM test method. Circumferential cracking of the bare tube test specimen was apparent within the first 8 hours of testing even while the test specimen was on test.
Crack characteristics were investigated by preparing metallographic sections of the test specimens. Corrosion Testing Laboratories, Inc.