304 to OFHC Copper

By Niekie3 (***)

Date 04-15-2003 19:37

Hi

I would use a Nickel or possibly a Monel filler.

Regards
Niekie Jooste

By man soo Date 04-16-2003 02:30

Thanks for your infomation Niekie.
But I was failed.
I used the Nickel base and Monel base filler metal.
then I met crack in HAZ.
so I need your welding process if possble.

Thanks agine.

Regards
mansoo.

By Niekie3 (***)

Date 04-16-2003 19:04

Hi Mansoo

Because the cracking was in the HAZ and not the weld metal, the filler metal used should not be the problem. In addition, HAZ cracking in 304 is unusual, unless the 304 was already in service and picked up some other form of degradation, such as stress corrosion cracking or intergranular corrosion due to sensitization. Assuming that none of this is the case, then I would guess that the cracking was in the copper HAZ.

This too is unusual for oxygen free copper, as OF copper is relatively easy to weld. This leaves me with the possibility that either the copper is NOT OF copper, or that the OF copper was held at a very high temperature for a long time resulting in oxygen pick-up. This will result in difficulties during welding.

Can you tell me:

1) In which metal's HAZ the cracking was.
2) If the materials being welded are new, or have been in service for a long time. If so, what service?
3) Was the copper exposed to excessively high temperatures.
4) How sure are you that the material you have is oxygen free copper.

Regards
Niekie Jooste

By brande

Date 04-18-2003 05:45

This is a strange one, to be sure.

When in this position, I find aluminum bronze can often do the trick.

Aluminum bronze, AB A-2 or as it is commonly known, Ampco 10, works very well on dissimilar applications.

Give it a try-let us know how you make out!!

Good Luck

brande

By man soo Date 04-18-2003 07:43

Thank you all.

Niekie,
I send an answer for your question.
1) The crack is bead.(filler metal : Nicu)
2) It's first test for vacuum component.
4) Well, It may be true.

Brande,
Thanks for your information.
I will try it.

mansoo

By Niekie3 (***)

Date 04-19-2003 13:15

Hi

Are you saying that the cracking was actually in the weld bead, not the HAZ?

Regards
Niekie

By man soo Date 04-21-2003 00:43

Hi Niekie

Yes.
The welding crack was actually in the weld bead.
This welding type was T-joint.

Welding metal was Stainless steel(Pipe : thickness 2mm, Diametar 35mm)
and OFHC Copper(plate : thickness 3mm).

Regards
mansoo

By Niekie3 (***)

Date 04-21-2003 08:05

Hi Mansoo

This obviously changes the picture!

From what you are saying, it sound like you have hot cracking taking place. If you used Monel filler, hot cracking problems become typical when you have 6% or more Cr in your weld bead. Assuming a 20% dilution from the 304, you should end up with around 4% of Cr in your weld pool. This should be OK. If however you have a much higher dilution, say 30%, then you will be at the limit. This may be the problem if you are using Monel filler. This problem will go away if you use a Nickel filler.

With Ni fillers, hot cracking can be a problem if you have relatively high levels of S or P contamination. It is possible that the Cu has P as an alloying element. This may be another reason for cracking.

I would proceed as follows:

1) Weld a "buttering" layer of Ni onto the Cu plate. (Use low dilution welding techniques.) If you experience cracking, then you know that the problem is P contamination.
2) If you have no cracking problem, weld the 304 tube onto the buttering layer, again with Ni filler.
3) If you had cracking problems following step 1, grind the affected area till the cracks are out, and again follow step 1. Following 2 or 3 times of repeating this step, the cracking should cease because you will gradually be removing the P from the weld pool.

Hope this helps.

Regards
Niekie Jooste

By man soo Date 04-21-2003 09:37

Hi Niekie

I agree with you.
so I would try it.

Thanks again.

Regards
mansoo.