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Study On Ferrite Measurement Methods For Duplex Stainless Steel, Part 2: Focus On Measurement By Ferrite Scope

Picture for Study On Ferrite Measurement Methods For Duplex Stainless Steel, Part 2: Focus On Measurement By Ferrite Scope
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Product Number: 51321-16772-SG
Author: Nozomi Satake; Mikihiro Sakata
Publication Date: 2021
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When evaluating the ferrite content (%) to assess the quality of industrial products made of duplex stainless steels, two different measurement methods are generally used. One method is a destructive method with metallographic observation to directly determine the volume fraction of ferrite phase (%). The other method is a non-destructive method based on the magnetic properties of ferrite phase which is typically measured with a ferrite scope. Unlike the ferrite measurement by metallographic observation, the ferrite measurement with a ferrite scope cannot determine the volume fraction of ferrite phase (%) directly. Instead, it detects the degree of interaction between magnetic field and ferrite phase and convert it to the volume fractions of ferrite phase (%). Although the ferrite scope is a valuable inspection tool that offers a simple and quick measurement, it has been observed the ferrite content (%) obtained with a ferrite scope is not always equal to the true volume fraction. In the present study, in order to reveal the discrepancy, a round robin test for ferrite scope measurement was conducted by involving institute including industrial NDE companies from around the world who have been regularly assigned in plant construction and maintenance. The test used nine (9) 22% Cr duplex stainless steel samples for which the volume fractions of the ferrite phase had been previously determined by metallographic observation.

When evaluating the ferrite content (%) to assess the quality of industrial products made of duplex stainless steels, two different measurement methods are generally used. One method is a destructive method with metallographic observation to directly determine the volume fraction of ferrite phase (%). The other method is a non-destructive method based on the magnetic properties of ferrite phase which is typically measured with a ferrite scope. Unlike the ferrite measurement by metallographic observation, the ferrite measurement with a ferrite scope cannot determine the volume fraction of ferrite phase (%) directly. Instead, it detects the degree of interaction between magnetic field and ferrite phase and convert it to the volume fractions of ferrite phase (%). Although the ferrite scope is a valuable inspection tool that offers a simple and quick measurement, it has been observed the ferrite content (%) obtained with a ferrite scope is not always equal to the true volume fraction. In the present study, in order to reveal the discrepancy, a round robin test for ferrite scope measurement was conducted by involving institute including industrial NDE companies from around the world who have been regularly assigned in plant construction and maintenance. The test used nine (9) 22% Cr duplex stainless steel samples for which the volume fractions of the ferrite phase had been previously determined by metallographic observation.

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Picture for Study on Ferrite Measurement Methods for Duplex Stainless Steel Welds
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51318-10634-Study on Ferrite Measurement Methods for Duplex Stainless Steel Welds

Product Number: 51318-10634-SG
Author: Nozomi Satake / Mikihiro Sakata / Tomoaki Kiso / Toshiaki Okabe /
Publication Date: 2018
$20.00

Ferrite measurements are used during welding procedures on duplex stainless steel. We studied the effects on the measured ferrite contents of (1) grid size, (2) number of fields and (3) measurement locations.

 
Picture for Ferrite Phase Fraction Quantification in Stress Corrosion Cracked Duplex Welds
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Ferrite Phase Fraction Quantification in Stress Corrosion Cracked Duplex Welds

Product Number: 51319-13263-SG
Author: Majid Abbasi
Publication Date: 2019
$20.00

Recent experiences with duplex 2205 stainless steel welds have shown that stress corrosion cracking can occur which may lead tocatastrophic failures. Known microstructural parameters such as ferrite phase fraction seems to play a significant role in crack propagation. Therefore quantifying ferrite phase fraction is an important step in ensuring weld quality. Several methods such as ASTM E562 point count electro-etching color-etching and optical image analysis as well as electron backscattred diffraction (EBSD) are utilized to quantify the ferrite fraction in duplex welds that have failed in service. Results of quantification by these methods are compared in terms of accuracy versatility and ability to apply in-field. Quantification results in cross-sectional samples indicate that local ferrite phase fraction is more meaningful than average fraction as cracks tend to propagate along high ferrite regions. Investigations on a number of cracked welds reveal that initiated cracks from the root pass reach the high ferrite region in coarse-grained heat affected zone (CGHAZ) and propagate along this region into filling passes. Further detailed microstructural results will be presented and discussed.Keywords: Duplex 2205 Stainless Steel; Welding; Ferrite Fraction; Stress Corrosion Cracking (SCC).
Picture for Ferrite Measurement in Duplex Stainless Steels
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Ferrite Measurement in Duplex Stainless Steels

Product Number: 51319-13437-SG
Author: Kasra Sotoudeh
Publication Date: 2019
$20.00

Duplex stainless steels typically contain 50% austenite and 50% ferrite. Phase balance is important in duplex stainless steels as it helps to impart optimum mechanical properties and corrosion resistance. Welding may alter the phase balance and so it is necessary to assure that phase balance is still within acceptable ranges. Ferrite measurement practice will be reviewed in terms of existing established techniques and recent advances in materials characterisation tools. Measurement precision and accuracy will be discussed.
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