ferrite number at SS 300 series
ferrite number at SS 300 series
(OP)
Dear experts,
I wanna know that what parameters cause the ferrite number goes up or down at SS 300 series?
and in clad with material of SS 309 and then 308 what would be predictable? could it be in the range of 5 to 12 percent?
I wanna know that what parameters cause the ferrite number goes up or down at SS 300 series?
and in clad with material of SS 309 and then 308 what would be predictable? could it be in the range of 5 to 12 percent?





RE: ferrite number at SS 300 series
RE: ferrite number at SS 300 series
Alloys such as 309 and 310 are often very stable and have zero ferrite formation. While this helps their performance at long term elevated temperatures it can make welding difficult. Specialty alloys (Nitronic xx, alloy 20, AL-6XN) are also zero ferrite grades.
If you are welding thin material and it is not highly constrained you can get away with welding with low or no ferrite. In thicker more rigid systems I agree, at least FN 4 is needed, and values up to 10 usually don't hurt.
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P.E. Metallurgy, Plymouth Tube
RE: ferrite number at SS 300 series
Attempting to measure the percentage of Ferrite in the weld is difficult because it is not uniformly dispersed in the weld. When several labs evaluate the same sample, the results can have considerable variation because the field of view of an optical microscope is rather small. It is like looking at an elephant in the dark with a flashlight. Depending on where you happen to be looking, you will see a different feature; a leg, an eye, the trunk, etc. Thus several people, each seeing just a small portion of the elephant will form different conclusions.
Where as determining the percentage of Ferrite with an optical microscope provides a very limited view, the instruments used to determine Ferrite Numbers looks are a much larger area which tends to average the amount of Ferrite present and provides more consistent, reproducible results when a sample is evaluated by several individuals.
Best regards - Al
RE: ferrite number at SS 300 series
RE: ferrite number at SS 300 series
What is the calculated value for your fillers? It is not uncommon to have the actual welds lower than the calculated value, it is the upper limit.
A value of 1 does not sound unreasonable for these alloys. Did you get good welds (they passed PT)?
Why last pass with 308? It is weld filler (there are no other product forms) and it has less corrosion resistance than the 309...
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P.E. Metallurgy, Plymouth Tube
RE: ferrite number at SS 300 series
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: ferrite number at SS 300 series
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P.E. Metallurgy, Plymouth Tube
RE: ferrite number at SS 300 series