Is spot welder worth it?

[D.A.T.]

Autogenous TIG welding is done everyday industry around the world--including arc spot welds without a hole in the piece were welding initiated on plain carbon low alloy steel sheet metal and 300 series stainless. For modern dual phase or tri-phase ferrite, bainite, martensite automotive steels and the micro-alloyed high strength low allow sheets any welding degrades what was processed into them by the steel mill. The OEM is the entity that controls whatever they have qualified for welding production and what they deem essential to do for repair/rebuilding of their engineered product. But for something made 45, 50. 60 years ago or better with minimally processed carbon steel sheet--that's a differing matter.

I've qualified a couple of weld procedures for differing companies over the years doing exactly what Eastwood shows for 16 to 20 gauge plain jane low carbon steel sheet and stainless. It is a macro etch in a solution of nitic acid and alcohol of a sample weld section and destructive peel test. Most kids in an Ag welding class can pass such a trivial thing and become "certified".

The video after the Eastwood one with the person not having a notched alumina cup and a blunt tungsten is generally regarded as poor industrial practice. The ionizing shielding gas has no escape path (except into the weld) and the end of the small diameter tungsten that is unsharpened will ball dang fast rendering it less useful.


I've used Liburdi Dimetrics orbital TIG equipment with a 150 amp power source and 3/32" diameter tungsten electrodes to weld well over 300,000 2" OD carbon steel boiler tubes with 0.130" wall thickness and perhaps 10,000 in 304/304L stainless. It initiates an arc and melts/ punches through drags itself around the tube in a pre-programed cycles and then tails out on the overlap without adding any filler metal. It creates the circumferential butt weld without the addition of filler metal on tubes butted tight. I routinely radiography them and they are water clear.

AWS Code D8.8M-2007 "Specification for Automotive Weld Quality--Arc Welding Steel" about automotive welding can be viewed on the web for free. You got to buy the 2021 edition. Code acceptable arc spot welds are shown without a hole in the top member and manual TIG is a recognized pre-qualified process. Plug welds with a hole are also shown as an acceptable joint. Either way--only 20% penetration into the bottom sheet is an acceptable depth over the required nugget diameter. Whatever a person chooses to do--if something ends up in an accident failure or wrong death/injury lawsuit about modified cars and welding on them--best to have good back up to support what was done and why.

 

[chevman]

The video after the Eastwood one with the person not having a notched alumina cup and a blunt tungsten is generally regarded as poor industrial practice. The ionizing shielding gas has no escape path (except into the weld) and the end of the small diameter tungsten that is unsharpened will ball dang fast rendering it less useful.

I overlooked that. His spot doesn't look as good as the Eastwood, and when he tries to rip it apart you can see how small the spot is on the second coupon. Thanks for pointing that out, its always in the details.

 

[D.A.T.]

The attached are some pages about what I referenced earlier. It is an American National Standards Institute adopted publication if it helps anyone in making their own decisions about such welding on their older vehicle and in the absence of having any published OEM Body manuals to reference about doing arc spot welding for panel replacements themselves in a manner that the manufacturer specifies. It's not the best copy but someone put a PDF on the web that's pretty easy to find and look at all the 28 pages or so.

Welding codes are not "how to do it" or product engineering documents. They represent a consensus among interested stakeholders typically about acknowledged weld processes, minimum sizing, often matching filler materials and so forth on the making of a new manufactured product. They typically do not comment on say how many spot welds to join something per lineal foot or what loading is assumed. If representatives from GM, Ford, US Steel, Lincoln Electric, BMW and Tower Automotive were involved in its development and approval --that is a positive sign there is sound validity to it as a bare minimum.