Ferrite number exceeds
Ferrite number exceeds
(OP)
Good evening all,
My client has specified a Ferrite number of 3-8 for weldments on a 316LSS pipe.
Most of the welds fall into this range except for 2 welds. Hence I would like to know is there an allowance as I've read through ISO 8249 and there is no mention of this.
My client has specified a Ferrite number of 3-8 for weldments on a 316LSS pipe.
Most of the welds fall into this range except for 2 welds. Hence I would like to know is there an allowance as I've read through ISO 8249 and there is no mention of this.





RE: Ferrite number exceeds
RE: Ferrite number exceeds
Sounds like you are cutting out welds and re-welding.
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P.E. Metallurgy, Plymouth Tube
RE: Ferrite number exceeds
RE: Ferrite number exceeds
We have readings of 8.1 and 8.2 on each weld respectively. And we will grind out the weld and re-weld them.
As there is no definite procedures to prevent high ferrite count upon searching engineering literature, most of them explaining control is dependent on the cooling rates and passing temperatures.
However, does anyone here know any specific causation for high ferrite numbers?
RE: Ferrite number exceeds
You also need to know the exact composition of the metal that is being welded.
You need to also work hard to control dilution rates.
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P.E. Metallurgy, Plymouth Tube
RE: Ferrite number exceeds
RE: Ferrite number exceeds
RE: Ferrite number exceeds
you can check this:
check metal base
Welding process (recomended GTAW)
gas protection (can use mixture with nitrogen)
Heat imput (you can increase the travel speed and control the amperage machine welding.
interpass temperature less 150° C
RE: Ferrite number exceeds
I would not assume FN 3-8 is a requirement for -320F service. At FN 8 and SMAW process I doubt it would pass Charpy testing.
Some of these ferrite specs just get passed down from generation to generation.
Rework sounds extreme IMHO. The variance (+0.1 and +0.2) is smaller than the instrument precision. Given the normal variation within any weld I would just move the probe away a quarter inch or so. I always report the mean of 5-10 readings at each location to eliminate the effect of occasional rogue readings.
BTW is this at the root or the cap? With piping it should only be the root that matters. Are you using a reputable electrode supplier? Because in my experience 316L falls within FN 5~6 pretty consistently.
"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 exceeds
Most of our welds were actually made with the GTAW process with ER308L filler metals. We will be qualifying thick welds (up to 3") with FCAW filler metals purchased with 3 - 8% ferrite in the near future. Our last qualification using similar filler metals on 3/8" thick materials easily met lateral expansion requirements. Whereas trade name is mandated as an essential variable, I will qualify two different manufacturer's cryo 308L fillers. One has a stated 5% ferrite.