Re: [PSUBS-MAILIST] Hatch fabrication dilemma

["Sean T. Stevenson" <cast55@telus.net>]

Re: full penetration - from my understanding of your description, the bevel was
from one side (outside) only, and was full depth, such that the dish edge was
effectively cut on an angle.  Is that correct?

My understanding is that a weld cannot be considered "full penetration"
(according to code) unless you backgouge into your root pass from the opposite
side and complete the weld from that side.  Simple enough with 90 degree T
intersections, which would use a double bevel instead of a single to minimize
the amount of weld material, and also reduce  the weld deformation by welding on
both sides of the plate.

With an acute joint, such as the dish to plate intersection in your project, you
don't have much choice because of the access issue, and hence must deposit your
weld predominately from the one side of the plate, which would use a single
bevel to accomodate that.  To get full penetration in that case entails laying
your root pass on the inside (the difficult access side), backgouging into it
from the outside and depositing the rest of your weld on that side.

Options to control warping as others have mentioned: use a fixture (jig),
preheat (also improves weld quality), and deposit your weld material tactically
to avoid putting too much heat into one side of the joint at once.  For example,
instead of starting at one point and welding continuously around, tack it at a
few strategic locations around the circumference first, alternate laying beads
on either side of the joint, etc.

As for heat treating, a full solution treatment (process anneal) will yield much
better results than a stress relief anneal, but you may be limited as to what
you can do based on the dissimilar metals.  What grade of SS is the plate?







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