Clad pipe to Clad pipe Welding.

[bmoorthy]

Hello All

When access from both sides are not possible, like welding clad pipe to clad pipe, generally the full joint is welded with the high alloy. (Clad pipe is CS + Incoloy 825). In this case ENi CR Mo-3 is used. This has been my experience.

Now a contractor is suggesting to use the following weld sequence(And is willing to support with a PQRT)

1) Weld the root with Er Ni Cr Mo-3
2) Second Run with E Ni Cr Mo-3
3) Next pass with carbon free Iron (Electrode/filler wire classification?)
4) Complete the joint with 7018-1

A)Is the above a common practice. Are there any flip side to the above suggestions?
B)What is the filler wire/electrode classification (AWS or SFA in Sec 2 c of ASME) for Iron electrode/Filler?

c)Is the above a stable weldment.

d)Somebody suggested welding Pure Nickel instead of Iron, is it true that Ni barrier instead of Iron will give a better weldment?

e)Can we permit above joints(Alloy + Iron + Cs) in a pressure vessel or Pressure plant piping or line pipe?

Thanks in adance


Moorthy

 

[metengr]

Here are some answers to your questions;

a). No, this is not a common practice for clad pipe butt weld joints for service temperatures above 650 deg F. What is the application – and service temperature??

b). Never heard of carbon free iron filler metal. I would NOT recommend it for this application - I would presume low strength at ambient and creep strength elevated temperature. ASME B31 Piping Codes prohibit low carbon filler metals due to lower creep strength (lower carbon content)..


c). No, as discussed in b).

d). I would use E NiCrMo-3 (Inconel) for the entire butt weld joint if this is exposed to service temperatures above 800 deg F or switch to E309 after the root and hot pass are completed with Inconel.

e). ASME Codes do not address or endorse the specific use of filler metals in weld joints. Backing up the butt weld joint with a PQR is fine - one could use coat hanger wire to weld a joint as long as the PQR meets Section IX requirements for procedure qualification. The designer is responsible for proper selection of filler metals.

 

[stanweld]

There are a number of manufacturers (domestic and foreign) who use the carbon free (<.010% C)iron filler metal approach for joining clad materials from one side without backing. From a logistical standpoint for field welding, I prefer the standard approach welding out the carbon or low alloy steel side with the Nickel base filler metal; there is simply too much room for error in the field using the other approach.

 

[bmoorthy]

Thankyou Stanweld

Could you please let me know using which welding process the Iron deposit is made and some of the brand names will help.

Regards

B.Moorthy

 

[EdStainless]

I have seen pure Ni used as a 'carbon barrier' in clad welds. I doubt that it works any better than simply using the Ni alloy for the entire weld.
I am with Stan, I hate the risk of using three different fillers in the field.

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[unclesyd]

I have seen this procedure used on large clad vessels but not on piping. One of the largest and most respected fabricators, now defunct, in the Midwest used this method on some large clad vessels made for us.
I've been checking to see who made a iron electrode we used and the only reference I have mentions Oxford. They don't list anything now.

We accomplished a lot of welding using "pure iron" electrodes. This wasn't for piping or vessels. For electrodes we used ARMCO IRON wire, a nail wire from US Steel and strips from material used to make flux core alloy electrodes, from Mckay. I can't recall having seen any pure iron electrodes meeting any specs.

 

[metengr]

unclesyd hit the nail on the head!

 

[weldtek]

In the first and third paragraphs.

 

[sayee1]

Kardo-Lincoln and Esab-I vaguely remember it as Ok53.xx

In any case these free iron buffers have been used in the past only for ss and experience on inconel is limited. The welding of three different layers needs a lot of skill especially to minimise dilution when depositing the buffer layer. Considerations have also to be given to the strength of the buffer layer, PWHT before such an approach could be deemed acceptable.

Moorthy

Could you give me a call on 00447930651683 if possible?

Thanks and regards
Sayee Prasad R CEng MWeldI MIOMMM


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