Manganese build up in weld deposit

[Dhananjay_Lahane]

Hello,

I had a A516 Gr 60 plate to build A671 CC60 CL 32 pipe by SMAW process.

Mn % in electrode is 1,4 % and that of plate is 1.12%

After doing normalzing , we found Mn% in weld deposit as 1.7%
What are the possible reasons for higher Mn percentage in weld .
It is currently not meeting A1 chemistry per weld procedure as % Man allowed is 1.6% max.

please suggest ways to control Mn %

Regards,

Dhananjay

 

First off, 'matching' filler metal to base metal does not mean your composition will match very closely. With carbon steel you are matching for strength, and testing (PQR and AWS A5.xx filler metal qualification) gives the validation. Welds tend to have lower carbon and higher manganese than the base metals they match. 1.6% max. Mn applies to the AWS test, not your finished weld.

Second, you can't control all elements that end up in a final weld, especially with processes using slag, which alter the deposit composition chemically. Different slag systems (i.e., different AWS classifications) have different effects on composition. For this reason some SAW fluxes are suitable for single-pass welds and not multipass, and vice versa.

Third, why are you normalizing a carbon steel weld? (Which does not affect composition anyway.)

Fourth, weld deposits and base metal are both carbon steel, but that is where the processing similarity ends. Each arrives at its final state through differnet routes, necessitating different starting compositions.

Conclusion: don't worry about the manganese.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[VQ35]

What type of electrode coating? How many passes to complete a joint? I've experienced similar results with SA516-70N but using SAW process and the flux played a significant role. Base metal was 1.4%, wire was <1.25% as per AWS A5.17 EM12K, but we had results as high as 1.95% in our deposited weld metal. Our joint was 3" thick so we had many passes for this effect to be compounded. We switch wire/flux combination and got much better results, around 1.3%.

 

[VQ35]

ironic, I'm curious why you conclude "don't worry about the manganese". I expect you'd agree that there are more important properties that could be measured from the completed weld metal. In our application we did find a crude correlation between toughness and Manganese content. That said, I do understand that correlation does not equal causation.

 

[weldstan]

How did you detrmine the 1.4% Mn content of the electrode? And which electrode did you use?

 

[Dhananjay_Lahane]

pipe required is of CL 32 hence Normalizing done
joint was 10 mm thick done by E7018-1 electrode.
1.4% Mn is reported in electrode MTC.
Is 1.7% Mn acceptable in weld deposit to meet A671 CC 60 CL 32? per my interpretation it is exceeding 1.6% per sec IX.
appreciate experts view.
Thank you .

 

Does A671 tell you to analyze the weld deposit?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Dhananjay_Lahane]

Yes, weld deposit analysis is required as per 7.2 of A671

 

[weldstan]

I suggest that you contact your electrode supplier. I tend to doubt the accuracy of the 1.4% Mn on the MTC. How did you analyze the Mn content? Cap pass only? Drillings? XFR? OES?