×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Ferrite number exceeds

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.



RE: Ferrite number exceeds

This is strictly a Client requirement. One assume that the requirement is made for -320 design condition; in which case, it has become pretty much the industry standard.

RE: Ferrite number exceeds

You might be able to beg forgiveness if you had some 2's, but high values I doubt it.
Sounds like you are cutting out welds and re-welding.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Ferrite number exceeds

If you can, and if the weld has excess external reinforcement, grind away any excess weld metal and grind/polish the weld metal into a smooth flat profile with the base metal. Test again for FN. If this doesnt help, ie provide higher FNs, do as EdStainless mentioned.

RE: Ferrite number exceeds

(OP)
Thank you all very much for your help!

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

The first action is selection of filler.
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.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Ferrite number exceeds

If the requirement was not 8.0, the 8.1 and 8.2 numbers would be acceptable.

RE: Ferrite number exceeds

I think Stan is saying your ferrite numbers are acceptable if the client specifies range as "3 - 8" but not if they are specified as "3.0 - 8.0". Precision of the spec determines this.

RE: Ferrite number exceeds

hello

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

weldstan,
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

We impact test qualified at -320 F with E308L-15 forty years ago with ferrite content slightly greater than 10% and easily met B31.3 lateral expansion requirements. Back then it was almost impossible to order 8% max ferrite filler metals. We last qualified with the 3%-8% filler metal requirement when constructing an LNG gasification plant in 2005. Ferrite contents in the deposited metal generally ran 4% to 8%.
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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources