Dissimilar metal weld
Dissimilar metal weld
(OP)
I have 2 pieces of 24" x 12" long pipe that are are each split longitudinally into to 2 halves.
One pipe is 304 stainless (P8) and the other is 1 1/4Cr1/2Mo (P11).
Each half pipe of each type material half pipes is welded to the other half pipe of the other material (P8 to P11) circumferential weld - P8 pipe is per ASME Section VIII, Div. 1 and P11 pipe is per B31.1 Code - wled is per B31.1 Code.
The he 2 sections are then welded together - 2 longitudinal joints.
How may I best transition from the longitudinal P8 to P8 weld into the longitudinal P11 to P11 weld. Question pertains to weld electrode used and weld procedure qualification.
Design pressure is 50 PSI and temperature is 300F? Material thicknesses are 1/2". Carbon content of (P11 to P11) material will be limited to avoid requirement for PWHT.
Do I need 2 or 3 weld procedure qualifications (P8 to P8), (P8 to P11) and (P11 to P11) or what? and how do I handle the transitionon between Codes and Metals regarding weld electrodes and weld procedure qualifications?
Thanks for any help in advance.
One pipe is 304 stainless (P8) and the other is 1 1/4Cr1/2Mo (P11).
Each half pipe of each type material half pipes is welded to the other half pipe of the other material (P8 to P11) circumferential weld - P8 pipe is per ASME Section VIII, Div. 1 and P11 pipe is per B31.1 Code - wled is per B31.1 Code.
The he 2 sections are then welded together - 2 longitudinal joints.
How may I best transition from the longitudinal P8 to P8 weld into the longitudinal P11 to P11 weld. Question pertains to weld electrode used and weld procedure qualification.
Design pressure is 50 PSI and temperature is 300F? Material thicknesses are 1/2". Carbon content of (P11 to P11) material will be limited to avoid requirement for PWHT.
Do I need 2 or 3 weld procedure qualifications (P8 to P8), (P8 to P11) and (P11 to P11) or what? and how do I handle the transitionon between Codes and Metals regarding weld electrodes and weld procedure qualifications?
Thanks for any help in advance.





RE: Dissimilar metal weld
As far as I know, B31.1 will not permit use of longitudinally welded P11 piping.
If this composite pipe will operate above 800F, then (a) you will need to consider use of a weld creep strength reduction factor of the longitudinal pipe and (b)you would need to use an incolnel weld electrode. The weld should be a very thick weld , and made with an automated welder, to ensure proper weld penetration ( a manual welder would turn down the amps to prevent weld spatter, but that would prevent adequate weld penetration).
RE: Dissimilar metal weld
RE: Dissimilar metal weld
RE: Dissimilar metal weld
RE: Dissimilar metal weld
RE: Dissimilar metal weld
One might approximate the range in stress per startup-shutdown cycle as E(a1Tc-a2Th), E= youngs mod, a1=P11 thermal exp coef, Tc=60F, a2= SS thermal exp coef, Th= 1125F.
It is not pleasant to think of what such a cracking mechanism may mean to transfer pipes in the work space.
For tubine, good ( actually, excellent) availability was found by substituting stainless weld filler with incolnel weld, using the widest weld width feasible, welded with an automaic welder ( to ensure adequate penetration).
RE: Dissimilar metal weld
In the case above, Inconel filler metal is not necessary at 300 deg F.
RE: Dissimilar metal weld
RE: Dissimilar metal weld
RE: Dissimilar metal weld