welding in casting material
welding in casting material
(OP)
what will happen if you weld on a casting material that already has a porosity? can you still have a good weld joint even if the parent material has porosity in it?
Thanks all in advance
Thanks all in advance





RE: welding in casting material
To start with you must grind out all of the porosity. Until a penertrant check comes out clean.
Then you can weld to rebuild the material (provided that the customer allows it)
In some materials you must follow with a heat treatment.
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P.E. Metallurgy, Plymouth Tube
RE: welding in casting material
Is the requirement a cosmetic repair, sealing against through-the-wall leakage, or a structurally sound repair?
Do I interpret correctly that your intended weld repair is "autogenously" welding (simply remelting) the area that is porous?
Generally serious weld repairs require excavating the bad stuff.
A nice high chrome abrasion resistant iron may crack happily if nearly any weld repair is attempted.
Fancy cast irons reverse Alchemically turn into Lesser csst irons when welded, often with a return to such poor ductility that HAZ cracking is likely to result unless stretchy bronze fillers or expensive, stretchy nickel based fillers and heroic measures to reduce thermal stresses upon cooling are practiced.
RE: welding in casting material
RE: welding in casting material
i don't trust the chinese supplier he did any PT or MT to the beveled weld end at least, and the part was dropped shipped to the location where it will be welded.
what are the chances the new weld will come out good in the event there's invisible porosity in the beveled weld end of the fitting? full penetration will be an issue i suppose?
RE: welding in casting material
RE: welding in casting material
Inspect them and just use the good ones.
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P.E. Metallurgy, Plymouth Tube
RE: welding in casting material
RE: welding in casting material
RE: welding in casting material
By "invisible porosity", I'm assuming you mean subsurface porosity with no visible surface indications? If so, you'll need an NDI process capable of detecting subsurface defects (like mag particle) to determine if any exist near the prepared surfaces for your bevel weld. You can always perform a post-weld NDI to locate any discontinuities beyond acceptable limits. But it would seem better to find any defects in the valve material before welding when it is much easier to fix them.
RE: welding in casting material
RE: welding in casting material
It makes sense, why should a weld be subjected to acceptance criteria that is more stringent than that of the base metal? Demanding a weld that is "free of porosity" while the casting being welded is permitted to contain porosity makes little sense. If the casting containing porosity will provide acceptable service, a weld containing the same amount/size of porosity should provide the same level of service.
Best regards - Al
RE: welding in casting material
Some SMAW electrodes are inherently slower "freezing." Welding techniques that slow the travel speed allow time for gas bubbles to boil out of the molten weld before it freezes.
http://www.lincolnelectric.com/en-us/support/weldi...
RE: welding in casting material
The real question is should you repair it at all. If it isn't part of a critical load path, or doesn't cause leakage then maybe leaving it is the best approach. We used to face this issue with pump parts. People wanted them to look better, but for durability reasons leaving visible defects was often the best choice.
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P.E. Metallurgy, Plymouth Tube