Ferrite Testing (FT)
Ferrite content analysis is a non-destructive testing method which provides critical data for austenitic stainless steel and duplex materials. The delta ferrite percentage or number allows a technical assessment of material corrosion susceptibility, mechanical properties, service suitability, and service reliability. To perform properly ferrite testing, both a minimum material thickness and a minimum specimen size are required.Test results are interpreted in accordance with current specifications and/or customer requirements. Reports issued are accompanied when necessary by drawings to identify locations tested.
An effective nondestructive testing technique for duplex and austenitic stainless steel materials is ferrite content analysis. The delta ferrite percentage or number enables a technical evaluation of a material’s mechanical properties, suitability for use, and reliability of use. Both a minimum material thickness and a minimum specimen size are necessary for successful ferrite testing. According to current specifications and/or customer requirements, test findings are interpreted. Drawings were included in reports when it was required to identify the test areas.Ferrite testing equipment shall be suitable for the range of 10–80% ferrite and in the range of surface curvatures and orientations to be encountered such as welds and small bore fittings etc.This NDT Equipment shall be sufficiently portable to gain access to each checkpoint under evaluation and be suitable for work within limited spaces and be capable of providing ‘direct read-out’ quantative results. Equipment shall have Calibration Blocks that cover the ferrite range 10-80% with relevant certification and ferrite measurements may be influenced when material thickness is less than 2.5mm. In such cases a correction factor given in the operating manual of the equipment may be used.
Whenever Surface Preparation is necessary to obtain a proper measurement surface, the finishing
Preparation shall be with a minimum 400 grit wheel, belt sander (or equivalent).Ferrite measurement shall not be employed directly on angle ground surface. In case of an angle ground surface, a minimum of 0.124mm further grinding shall be performed with grinding wheels up to 400 grit to free the measurement surface of any pre existing angle grinding marks.
Calibration of Ferrite Equipment:
Calibration of ferrite equipment shall be necessary while normalization of thin and curved materials, corrective calibration wherever the probe changed and master calibration if memory loss or re calibration due.