Black spots on DSS Weld Joints.

[Vasantharao]

Dear Experts,

We observe Dark spots on Welding of Duplex Stainless Welds.  

Material is : UNS S31803 ,  Filler Wire for root - ER2594, rest ER2209.

Sample pictures are attached for reference.

Oxygen level in shielding / Purging maintained well below 0.2%.

Interpass <150 Deg.C

Pl. share your valuable information.

Thank you.

P.Rao

[Bharat Kumar]

It looks like slag inclusion.

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Thanks & Regards,

A Bharat Kumar

+91 9989717650

[prem_nautiyal26]

How you can get slag inclusion in TIG ????

Regards 

Prem Nautiyal

Sent from Samsung Mobile

[Julio Magalhães Jesus]

Dear,

about process the welding don't have SLAG only SILICA.

Magalhães Júlio


Welding and Inspection Around the world

[Ramin Kondori]

Dear Rao:

What gas have you used...?

Have you supplied your shielding gas from a reputed supplier (certificate etc.)...?

Shielding gas with low quality can cause such black spots.

Regards

Ramin Kondori

Sr. QA/QC Engineer

SINOPEC

r.ko...@petroyada.com
+98-2123592322
+98-9132150320

[pgoswami]

Hi Mr.. Rao,

 

These black spots are essentially the products of contamination in the weld metal.There may not be a single reason towards this .It may happen as follows:-

• Welding Fillers :- The drawing lubricants e.g graphite could contaminate the welds and cause  these spots to be formed. Through acetone cleaning of all the fillers should be done before welding. Also fillers with oxidized tips should be used following  removal of the oxidized tip(by cutting).

 

• Shielding gas: check the purity of the gas, it should be 99.95% or more.  Premixed gases say Ar+N2 may contain traces of moisture , which  may increase the oxygen potential and the resultant oxidation of the puddle. As you said  earlier the "O2" content was  well below 0.2%.. Assuming the fact that  for shielding gas everything was under control it would be always advisable to check the right purity of the shielding and purging gas, prior to welding.

 

• The condition of the pipes:- Duplex pipes should always be pickled  and cleaned at the mill. If not done at the mill, it's preferred to pickle the pipes and remove the excess scale or oxides in the fabrication shop. Usually such oxides could be very microscopic and very difficult to remove by grinding. Excess oxides may introduce contamination in the weld.Also cross contamination during grinding could harm the welds.

 

The dark spots are bad , with potential for pitting during procedure qualification testing or while put in service.

 

Let me know if it helps.

 

Thanks

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Specialist

Ontario, Canada

pgos...@quickclic.net

pgos...@sympatico.ca

 

 

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From: Vasantharao [mailto:vasan...@yahoo.in]
Sent: Wednesday, February 12, 2014 11:57 PM
To: pgoswami
Subject: Fw: Black spots on DSS Weld Joints.

Dear sir,

Can you give you suggestions on DSS dark spots as group member are not responding.

Is there any problem with dark spots. Why it forms. 

regards

P.Rao

[Roy Joseph]

please clean the filler wire using cleaner.

[Vasantharao]

Dear Sir,

We use Pure Argan  - 99.998%  with moisture <5PPM, Oxygen <5 PPM as per Gas MTC.

We use separate shop for DSS welding for avoiding contamination from CS welds/ grinding.

Welders aware of Acetone cleaning of joint, filler wires etc.

Purging gas  O2 level continuously monitored with instruments till completion of welding  (maintained <0.03%).

Random checks during welding  observed inter pass temp. some time more than 150 Deg.C  but <200 Deg.C

Some time we preheat to 50 Deg.C  to remove moisture.

This problem typically we observe in 6" & 8" Pipes, others are satisfactory (lower dia).

Is it dark spots are any inter metallics? ( As per leterature it forms at 300-700 Deg.C, generally during welding, this range not encountered).

Pickling & Passivation will be costlier, management may reluctant to go for it.

Is there any effect of TIG nozzle sizes, Moisture condensation at regulators?.

Some of the Pipes are received from China, is there any material chance?.

This problem typically we obseve in 6" & 8" Pipes.

Your suggestions noted, i will work on those.

Thank you for your valuable suggestions.

regards

P.Rao.

+968 93883351

[pgoswami]

Mr. Rao,

 

Please see my answers to your queries.

 

Thanks

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Specialist

Ontario, Canada

pgos...@quickclic.net

pgos...@sympatico.ca

 

 

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From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Vasantharao
Sent: Saturday, February 15, 2014 1:46 AM
To: material...@googlegroups.com
Subject: Re: [MW:20108] RE: Black spots on DSS Weld Joints.

Dear Sir,

We use Pure Argan  - 99.998%  with moisture <5PPM, Oxygen <5 PPM as per Gas MTC.-- That's fine.

We use separate shop for DSS welding for avoiding contamination from CS welds/ grinding. --That's fine 

Welders aware of Acetone cleaning of joint, filler wires etc. -- That's fine, and should be done.

Purging gas  O2 level continuously monitored with instruments till completion of welding  (maintained <0.03%).--This is good but still try to keep lower, (<0.02%). 

Random checks during welding  observed inter pass temp. some time more than 150 Deg.C  but <200 Deg.C -- That's fine.

Some time we preheat to 50 Deg.C  to remove moisture. - That's fine.

This problem typically we observe in 6" & 8" Pipes, others are satisfactory (lower dia). --This tells me that there're issue with some pipes, assuming that same welding filler (brand, batch and through cleaning  as mentioned above) is used for welding.

Is it dark spots are any inter metallics? ( As per leterature it forms at 300-700 Deg.C, generally during welding, this range not encountered). -- Intermetallics are detected only under microscope, they can not be interpreted by visual inspection alone.  2209 is a relatively lean filler metal (wrt ER 2593 and 2594 filler). Hence I would not suspect much intermetallic. However as a cross check you may take replicas or put one small section of the welds with dark indications under the microscope to see if it contains intermetallics. Note to get  to the  intermetallics, you have to do the grinding , polishing and micro etching, which will remove the dark spots. A better approach is to see the section under SEM & EDAX, which may be done on as it is condition. EDAX will tell what the contaminant is , if metallic or hydrocarbon

Pickling & Passivation will be costlier, management may reluctant to go for it. --There's no other way if the steel is grossly contaminated with any chemicals  

Is there any effect of TIG nozzle sizes, Moisture condensation at regulators?. --I do not think so. 

Some of the Pipes are received from China, is there any material chance?. --I do not want to be prejudiced.But where's there's bulk purchase/ trading, such mishandling  would happen and  would  produce bad results while welding. If the products are directly purchased from the mill, post this problem directly to the manufacturer. Otherwise if it's purchased through dealers( with many sub-agents)  you may have a hard time to get the correct answer.

 

This problem typically we obseve in 6" & 8" Pipes. --If the quantity is not much get them replaced with products from some reputed mill 

[Rui....@pt.linde-gas.com]

Mr. Rao

is there spots or inclusions?
when you will weld 6" or more diameters the thickness is higher and you shall increase the amperage. Can you check if TIG electrode is correct for newer this parameters?


Cumprimentos

Rui Fernandes Pinho
Divisão de Gases Industriais
Desenvolvimento de Aplicação de Gases

Linde Portugal, Lda.
Travessa Joaquim Dias Salgueiro, Nº 44
4470-416 Vila Nova da Telha, Portugal
Phone + 351 22 999 8380, Fax: + 351 22 996 4039
Mobile + 351 91 473 9197
rui....@pt.linde-gas.com, www.linde.pt

For more options, visit https://groups.google.com/groups/opt_out.[attachment "Black Spots on DSS Welds.pdf" deleted by Rui Pinho/PT/LG/LindeGroup] [attachment "Chris Baxter IOM paper.pdf" deleted by Rui Pinho/PT/LG/LindeGroup]

[Ramin Kondori]

Mr. Rao:

Chinese products shall be tested and inspected carefully...

In our project, we are dealing with this "Chinese material quality" issue almost on daily basis.

Each day we receive a new material at site, we know that it will turn to another headache...
Most of the samples (which client has taken) have failed in mechanical tests.

Materials without identification is the least of our problems (we can easily reject them and move on)...!!!
It's the so called "good quality" Chinese material which causes problems. They have certificates, identification etc. but they usually fail in tests...!!!
 
The most recent one is LTCS flange (A350-LF2) material with 4J absorbed energy (Impact test), who could possibly imagine that...?

Be careful with those Chinese products.

Regards

Ramin Kondori

Sr. QA/QC Engineer

SINOPEC

r.ko...@petroyada.com
+98-2123592322
+98-9132150320

[Tahir Olmez]

Dear Friends ,

We had the same problem for tig (gtaw) , as we realised that all black spots were small slag zones , the solution was grinding before pickling will exactly solve your problem if there aren't any other problems or mistakes

Best Regards

>Tahir Bilge Olmez
>International Welding Eng.
>Met. & Mat Eng.
>Verify Europe & Atlantic Marine Survey
>+90 544 6158801

[c sridhar]

In some of our earlier projects, we have faced similar problem with tig process. The slag line

traces in between the layers were not visible  in radiography, but noticed  in  UT testing in the

form of suspected  LF.

The contamination (even with all the precautions) could be due to quality of material, purity 

of argon gas or due to other unknown reasons.

we could overcome the problems not by grinding but with power brushing of each layer of

welding using SS stringer and cup brushes. 

The welds passed through and slag line traces/spots were not seen any more.

Sridhar.
 

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From: Tahir Olmez <tahir...@gmail.com>
To: material...@googlegroups.com
Sent: Friday, 21 February 2014 3:53 AM
Subject: Re: [MW:20157] RE: Black spots on DSS Weld Joints.

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[Tahir Olmez]

I agree with Sridhar ,

Also we use the power brushing too as Sridhars used , but pls focus on grinding or brushing ; those are the key of your solution

>Tahir Bilge Olmez
>International Welding Eng.
>Met. & Mat Eng.
>Verify Europe  & Atlantic Marine Survey
>+90 544 6158801

[rajesh...@gmail.com]

Hi All,

We are also facing the same issue in SDSS welds on 6" Pipe welded with ER2594.

Can anybody let me know the root cause for this spots and remedy. 

[pgos...@rogers.com]

Hello,

 

Please see my responses to this old post (2104) in materials-welding forum as below.. These spots may occur:-

• Due to wire drawing residues (often very microscopic) in the filler wires. Rubbing with emery papers and acetones may clear some of these residues.
• Traces of cleaning products left on the Duplex base metals, called smuts .
• These dark spots may be removed by power brushing with stainless steel brushes or soft abrasive(Aluminized)  grinding tools.

 

You may see the attachment for additional guidance.

 

Thanks.

 

Pradip Goswami.P.Eng, IWE.

Independent  & Consulting Welding & Metallurgical Specialist

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

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

Cell/Whasapp:1-905-9793232

 

Black spots on DSS Weld Joints. (google.com)

Virus-free. www.avg.com

[sujay shelar]

Good Morning,

1. Rub the wire with Emery paper and clean with acetone.

2.Keep the torch in approx 50 to 65 degree angle through which proper shielding can be created.

3.This will reduce  black spot remaining can be removed by polishing.

Thanks.

On 17-May-2021, at 9:45 AM, pgos...@rogers.com wrote:



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<Pages- BW_Pickling+Handbook_EN_2019_GL_128_Preview-4.pdf>

[Naveen Raj]

Hi,

Use wire brush (SS) rubbing immediately after welding completion it will help you to prevent from oxidation.

Best Regards,

Naveen Raj. R

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[GMT]

Hello

you can also use "Weld Cleaning Gel" for cleaning

Best Regard 

GMT

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[prasanta kumar Sethi]

you can use wire ss brush  rubbing immediately after welding completion & than as soon possible u can clean with Acetone to avoid this type spot   it will help you to prevent oxidation.

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/CAHnLYC%2Bu3S2W2O6%3Dwa331NCjGb9VtLQPn5m_NusRCLjY7Hrpew%40mail.gmail.com.

[Vinay Thattey]

Try cleaning with an SS wire brush .. Followed by cleaning with solvent like acetone .Better to use chloride ( halide ) controlled acetone 

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