Ferrite test of stainless steel pipes
Ferrite test of stainless steel pipes
Ferrite measurement is a fast, cheap and accurate method for measuring the content of delta ferrite in austenitic and duplex stainless steel tubes. Proper ferrite content provides a balance between ductility, toughness, corrosion resistance and crack resistance.
Purpose of ferrite test
Heat, pressure and caustic environment require materials and welds with high metallurgical integrity. Correct ferrite measurement is helpful to avoid solidification cracks and corrosion of stainless steel welds, pipes, plates, pressure vessels and petrochemical components.
When ferrite content is too high, stainless steel will lose its ductility, toughness and corrosion resistance, especially at high temperature. If the ferrite content is too low, the weld of stainless steel will be affected by thermal crack or solidification crack.
In the weld of duplex stainless steel, the deficiency of ferrite content will also reduce the weld strength and contribute to the development of stress corrosion cracking.
Ferrite testing process
Baker testing can measure and report the ferrite content of welds and components during manufacturing and in-service using two different testing methods, depending on code or customer requirements. Using magnetic induction, trained BTS technicians can report readings individually or in a range to meet customer requirements through high-precision digital readings and on-site instrument calibration checks. In addition, high sensitivity and low MU permeability standards are used to measure ferrite content among a series of calibration standards. Test measurements can be reported by direct reading or conversion of the amount of ferrite (FN) or percentage of ferrite according to welding procedures, customer drawings and specifications.
