Weld overlaid by flux wire process using a wire TP430.

[0707]

We have an exchanger shell plate A335 P12 15mm thick that was internally weld overlaid by flux wire process using a wire TP430.

After weld the clad deposition of TP 430, the dye penetrant inspection revealed that TP430 weld overlay was found with lots of pores and cracks.

What went wrong in this welding procedure?

Wrong filler wire?
Lack of PWHT?
Will it be beneficial to use of TP410S filler metal instead of TP430?


Thanks

luis

 

[metengr]

0707;
It looks like from your OP you may have missed one critical step for a dissimilar metal weld - where is 309 stainless steel for the 1st pass prior to depositing the 430 wire? You cannot deposit 430 stainless steel filler metal directly on carbon or low alloy steel substrates because of dilution concerns. The cracks are probably the result of an intermediate chromium-containing martensite that has little ductility.

 

[metengr]

2nd comment - why was this particular filler metal even selected as an overlay for this vessel? Normally, 430 stainless exhibits poor weldability because the weld metal structure contains both ferrite and martensite, along with formation of coarse grains. You would need PWHT after welding as a minimum to temper the martensite in the weld deposit.

 

[0707]

The first option was to have a explosion weld plate 2mm thick of TP 410S over the A335P12, 15mm thick plate, but by long time delivery the constructor propose a weld overlay of TP 430. They didn’t submit us their welding procedure and the things went wrong. I totally agree with your replays Metengr.

Thanks for your empathy.


luis

 

[EdStainless]

I wonder what the carbon level of the 430 overlay is. If it is low then it should be fully ferritic and have good ductility. If it is higher then cracking is expected.
A 309 first layer and 439 (the stabilized grade) for the over lay would be my thought.
They probably tired to build it all in one pass. The ended up with a high Cr martensitic weld that has no chance of not cracking.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[SJones]

The API 582 recommended consumable for the first layer is either ENiCrFe-2/-3 or ERNiCr-3. The tubular electrode equivalents can be determined from SFA-5.34.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[DVWE]

SJones,

The version of API 582 that I have doesn't list 430 as a final overlay option without the approval of the end user (B1.9).

 

[SJones]

In essence, yes; but the 405/410 requirement has to be considered as a starting point surely? API 582 hasn't specifically addressed 430 because it's not a usual oil & gas overlay. A Balmforth diagram analysis will show you that you stand a snowball's chance of getting below 60% ferrite anyway because you are starting on the 16 chrome equivalent line with the basic composition of 430 and you wouldn't want to pump it up further on top of a high chrome austenitic weld layer. Strain concentration in this ferrite network is probably a contributory factor in the cracking.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[DVWE]

I'm just saying that there's no reason a 309 butter pass wouldn't work as stated above...

 

[metengr]

API 582 hasn't specifically addressed 430 because it's not a usual oil & gas overlay.

Because it exhibits lower weldability in relation to other stabilized grades of ferritic stainless steels.

The 309 or Ni-base filler metals will work for buttering. The reason for the cracking in the OP is that 430 stainless was deposited directly on carbon steel or low alloy steel base metal with no buffer layer. This resulted in ferrite and most likely an interconnecting network of untempered martensite and subsequent cracking.

 

[SJones]

Makes one wonder how it got through procedure qualification doesn't it!

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04