Re: [MW:31136] RE: 31133] Re: 31131] CS with Duplex SS (S31803) clad vessel PWHT?

Hi,

Stress relief temperature at 650 ◦C induced sigma phase precipitation in between delta ferrite and austenite (δ/γ) grain boundaries, resulting in the loss of corrosion resistance in the weld metal.  Post Weld Heat Treatment (PWHT) to solution annealing temperature had shown no weight loss. The ferrite count determination in the region of weld metal cladding increased at hydrogen relief and decreased at stress relief temperatures due to slow cooling, which is more favorable to austenite formation. The amount of ferrite in the weld metals is significantly reduced with the increment of solution anneal temperature to 1050 ◦C because of sufficient time for the formation of austenite and giving optimum equilibrium fraction in the welds.

Thanks

Gigi

On Sunday, 12 July 2020, 07:03:05 EEST, pgoswami@rogers.com <pgoswami@rogers.com> wrote:

Hi ,

A switch to complete duplex stainless teel construction will offer at least
15-20% reduction in thickness and weight .Duplex may be slightly  more
expensive that conventional 304/304L(see the data sheet as attached).The
same holds good when there's comparison between duplex clad vs solid duplex
construction. However cost is not the only factor in choosing DSS as the
material f construction. It's more of technical.

Duplex  (31803) clad carbon steel of > 50mm wall thickness has to subjected
to PWHT , which is commonly stress relieving . A PWHT range of 600-620 Deg C
is highly embrittling range for 31803 DSS due formation of various
intermetallic phases. See the attachment for detailed illustrations. PWHT at
lower  temperature range 400-500 Deg C also causes embrittlement. Thus a
choice of DSS31803 clad+ CS backing  vessels  would be highly problematic .
If DSS is the only material of construction , then advice  would be to go
for full thickness DSS construction.

The question is what's the process design and fluid involved ? Why Duplex
SS is chosen as the material of construction. If one is going  for 31803
clad +CS Backing design then the purpose of DSS is for corrosion resistance
only. There're many materials to choose from. If equivalent pitting  &
crevice corrosion resistance  as well as chloride stress corrosion
resistance is needed then a switch to 254 /654 SMO  as the clad on Carbon
Steel would also be a good option.



If DSS clad is the only option then a simulation test at the mill is a
must, before the final decision. The critical parameters to be evaluated :
hardness, impact, % El, all required corrosion test results for the plates.

Thanks.



P.Goswami.P.Eng, IWE.

Email:pgoswami@rogers.com,pradip.goswami@gmail.com

Cell/Whasapp:1-905-9793232







From: Materials & Welding <materials-welding@googlegroups.com>
Sent: July 11, 2020 12:14 PM
To: Materials & Welding <materials-welding@googlegroups.com>
Subject: [MW:31133] Re: 31131] CS with Duplex SS (S31803) clad vessel PWHT?



its in design stage,  process data  states as solid S31803 -42mm thick(with
an option to use CS+clad), however use of clad plate might be difficult due
to PWHT, as the thickness of backer plate will be >50mm.



On Saturday, 11 July 2020 at 20:53:04 UTC+5:30 pgoswami@rogers.com
<mailto:pgoswami@rogers.com>  wrote:

Hi,

Discussions on the identical issues had taken place in this forum few years
ago. I'm' reposting the discussion and the provided answers. It would be
helpful to get the drawing or the tech specs so as to provide meaningful
answers.

Thanks.



P.Goswami.P.Eng, IWE.

Independent  & Consulting Welding & Metallurgical Specialist

Aramco Approved Designated Project Welding Engineer(DPWR)

Linkedin:  <https://www.linkedin.com/in/pradip-goswami-2999855/>
https://www.linkedin.com/in/pradip-goswami-2999855/

Email:pgos...@rogers.com,pradip....@gmail.com

Cell/Whasapp:1-905-9793232 <tel:(905)%20979-3232>



From: Materials & Welding <material...@googlegroups.com>
Sent: July 11, 2020 6:43 AM
To: Materials & Welding <material...@googlegroups.com>
Subject: [MW:31131] CS with Duplex SS (S31803) clad vessel PWHT?



ASME Sec VIII div1

SA516 Gr 70 - 51mm thickness+S31803 clad



any experience on duplex clad vessel PWHT?



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