Sigma Phase is a brittle, nonmagnetic phase of tetragonal structure occurring in many transition metal alloys; frequently encountered in high chromium stainless steels. It results from a transformation of Delta ferrite in the alloy, creating carbides at the grain boundaries, which reduces the carbon and chromium content that normally provides strength and corrosion resistance in the metal matrix. Because the condition has significant length and is not a single point type defect, the standard, which is provided by the customer, is measured as a percent of the cross section of the tube wall or bar, using micrographic techniques. The test consists of a 2 channel MultiMac® coil eddy current tester. 1 channel is used for the detection of typical defects, while the other channel is used for finding sigma phase; a condition caused from improper or extensive heat treatment.The second channel on the MultiMac is an absolute tester using two Varimac® coils. One coil is balanced on air and used to calibrate the equipment with a reference standard.
features :
specification :
- 2507 Duplex Stainless Steel Tube
- 80 FT Cut Lengths
- 3/4″ OD with .083″ Wall Thickness
- Detects Sigma Phase as Small as 2.6% of Tube Wall Cross Section
- 2 Channel MultiMac® Eddy Current Tester- Offline
- 2 Varimac® Comparator Coils
