Joining CrMo to CS 4

[nnlpba]

We are joining Cabon Steel P1 material, A106 Gr Bto CrMo P5B, 9 Cr 1 Mo. Should we use E-XXXX-B2L or E-XXXX-B8 or E-7018-1 elctrode. The operating temperature is 300 to 700 deg F. The weld will be preheated to 350 F and PWHT at 1350F.
What would be the affect of each of the electodes with the base metal as far as:
Oxidization
Creep
corossion etc.???

Which electrode is recommended?? Reason??

 

[metengr]

The operating temperature range you have stated should not result in any appreciable creep deformation for the Cr-Mo material, and for the carbon steel you are right at the transition to time dependent effects on strength properties (creep deformation).

Regarding your weld joint, I would suggest using a B3 filler metal for the dissimilar metal weld joint. I would increase your preheat to 400 deg F, and your PWHT temperature is too high. For P-No 5 B Grade 1 material, I would use a 1300 deg F PWHT, this is below the lower transition temperature for the P-No 1 material (CS).

 

[banaeian]

Recently we had a same case and we used B6 electrode. Considering the high temperature services the resistance of filler metal is more than the base metal P1.
In case of using E7018 as carbon steel filler metal it can not work at high temperature considering the properties of weld metal comparing to base metal which is normally wrought steel.
It is recommended to use the higher material class for joining dissimilar metals.

 

[metengr]

banaeian;

In case of using E7018 as carbon steel filler metal it can not work at high temperature considering the properties of weld metal comparing to base metal which is normally wrought steel.

This is not really an accurate statement. The strength of the weld joint is limited by the strength of either of the two base metals being joined provided a weld filler metal matches either of the two base materials. In this case for the stated operating temperature, even an E7018 filler metal would be suitable for this weld joint because it matches the CS base metal that is being joined.

 

[attilon]

Normaly I would use an austenitical electrode with
10%Ni,18%Cr, maybe with 1-3%Mn.
The only problem is that after welding, you must use controlled cooling time. This should be such long that to not to let form martensite in the t8/5 cooling periode. In these cases martensite is public enemy no.1. But for this there are standard diagramms and you can easily choose this cooling diagramm.

http://www.heavyplate.com/heavyplate/servlet/basis.Dispatcher?Masken_NR=7305&Session_ID=25ktjzmtUeN

Good luck!