SMAW ELECTRODE FOR P91 MATERIAL

[JOSE SEBASTIAN]

Dear Group Members,

I am having 3 approved WPSs for P91 material.These 3 WPS are using 3
different electrodes.

1)9018-B9 -Iron powder & Low hydrogen potassium coated
2)9016-B9 -Low hydrogen potassium flux coated
3)9015-B9 - Low hydrogen sodium flux coated

My doubts are

1)How we can justify which electrode is better for my use?
2)Any where in code it mentioned the suitable flux coating for
electrode?


Regards

Jose Sebastian
+919687660525

[naveen...@yahoo.com]

Dear Friend,
E9018-B9 and E9016-B9 generally used for tubes or thin pipe welding without root run of GTAW.

Creep rupture data really makes the difference in addition to Mn+Ni %.

I think only 9015-B9 have the creep rupture data. You can use Thermanit Chromo 9V of Bohler Germany make.

Regards

Sent from BlackBerry® on Airtel

--
To post to this group, send email to material...@googlegroups.com
To unsubscribe from this group, send email to materials-weld...@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

[Himangshu Das]

The best choice of the three would be to use 9015-B9, as the others have chances of inclusion
of Sn, Sb, As, P etc as "tramp elements". These elements shall migrate to the grain boundaries
during welding and remain there after welding. These will affect grain bonding, subsequently
decreasing the creep resistance which shall show enhanced effects during high temperature
service leading to premature HAZ failure.
It is also strongly recommended to use non synthetic type electrodes i.e. core wire shall be of
same or equivalent composition of parent metal. Synthetic electrodes use a carbon steel core
wire and alloying elements are added to the flux coating. During welding these alloying
elements are infused into the weld, so that you do get the requisite weld metal chemistry but
the tramp elements are also included in the weld.
Himangshu












On Thu, 08 Sep 2011 10:02:42 +0530 wrote

--

To post to this group, send email to material...@googlegroups.com

To unsubscribe from this group, send email to materials-weld...@googlegroups.com

For more options, visit this group's bolg at http://materials-welding.blogspot.com/

The views expressed/exchnaged in this group are members personel views and meant for
educational purposes only, Users must take their own decisions w.r.t. applicable
code/standard/contract documents.

Treat yourself at a restaurant, spa, resort and much more with Rediff Deal ho jaye!

[pgoswami]

Hi Jose,

This issue was raised earlier in this forum. As per my knowledge base, majority of the SMAW electrodes for this material  conforms either to AWS SFA 5.5,E-9015-B9 or E-9016-B9 or E-9018-B9

As per industry experience greater success has been observed with the “-15” type electrode coatings than  other  varieties. Primary factors influencing this success are enhanced compositional control of tramp elements and better control of bead shape plus interbead tempering during welding.When using iron powder additions, deleterious tramp elements or elevated phosphorous can “come in the weld”.

Thus E-9018-B9, electrodes  require very precise control (on the purity of Iron powder) to control the level of tramp elements/residuals in the weld. Chances are there that impact values of E-9018-B9 electrodes could be less technical requirements are  specified up front and agreed upon by the manufacturers and the end users.

One point of interest  would be specifying in the purchasing spec, ,  X-bar or X-Factor < 15, where ,X-bar = (10P + 5Sb + 4Sn + As) /100, where P, Sb, Sn, and As in ppm. X-Factor is a measure of temper embritltement, which highly influenced by the above tramp elements.

The attached data sheets of Kobelco and Metrode are in E-9015/9016 category ,while Bohler Thyssen have both -9015/9018-B9 type. The product of ADOR is in E-9018-B9 category.Many fabricators would prefer 9018-B9, possibly due to better deposition efficiency. However there could be problems as mentioned above.

If  impact test of weld metal is not a strict design requirements then E-9018-B9 may be used (provided it's purchased from known manufacturers, and the brand is proven, not just by AWS Equivalence). Having said that impact properties are not a requirement of ASME Sec-I or B-31.1 codes on P-91 steel but its advisable to have welding consumable procured with good notch toughness to have  balance of all types of mechanical properties and better service induced creep life, and creep/fatigue life (where thermal cycling is experienced).

Otherwise E-9015/9016-B9 should be the default choice.

I hope this would provide enough information on the above topic.

Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist & Consultant
Ontario,Canada.
Email-p...@sympatico.ca,
pgos...@quickclic.net

N.B:- If you get hold of API-938B- Use of 9Cr-1Mo-V (Grade 91) Steel in the Oil Refining Industry, read that at your leisure. Though this document is not mandatory for powerindustries , but many good design principles on P-91  are in this document.

Thanks.