Literature on autogeneous welds for sheet metal

Date 05-21-2008 20:59 Edited 05-21-2008 21:41

Hello, I'll just mention it briefly. I'm a welding engineering intern. Right now my job detail is to create welding procedures and design guide documents for welders and engineers respectively. The large majority of our products are austenitic stainless steels primarily 304 although I've seen some other types as well. Most of are products are mild steel frames with stainless steel liners. However we have some rather complex Stainless steel sheet sub assemblies that are formed than welded together.

as of right now the shop doesn't have any sort of standard. If two pieces of sheet are to be tacked together in a lap joint. one welder may do 1/4" GTAW "hot tack" (generally with no filler) with 6 inch spacing, another will do 2 inch spacing Resistance spot welds.
I'm trying to develop a more formal standard for things like spacing, stitch technique, anti distortion practices. For the engineers I'm trying to complie some reference information in regards to GTAW autogenous weld strength and resistance spot weld strength as well as design theory so I can back up a uniform standard with numbers, and so that engineers designing new parts won't leave it up for the welders and test department to determine joint design.

Never before have I worked in a weld shop where the welders picked the process they used!

Anyways can anyone reccommend some reference material on standard joint design for mostly thin guage (12-20) stainless steel for the GTAW process, and welding joint design books in general. I would really like to be better be able to put numbers to welds and not revise prints off of obvious errors and personal experience. We aren't using a code so what ever I reference I'm probably going to end up boiling it down to simple one liners for the welders and engineers. "For X pounds of force use spot welds every X", "for horizontal shelfs use resistance spot welds if possible as lap joints have poor performance in shear strength" etc etc.

any reference would be useful. right now everyone is in the dark (including me) on how to design autogeneous welds, and when they should be applied

By Larry D Morey Date 05-22-2008 16:06 Edited 05-22-2008 16:22

I also work with thin gauge Stainless Steel and depending on my purposes thin gauge to thin gauge or thin gauge to structural steel and i find it necessary to use several code books in conjunction and they are C1.1-66 (Recomendations for Resistance Welding) D1.3-98 (Sheet Metal Code) and D1.6-99 (Stainless Steel Structural Code).These are older editions but are what is required at present by contract specifications; consult yours to be sure of which code book you might need to follow. D1.6 covers thickness down to 1/16'' and above. This is helpful specifically for welding thin gauge to heavy and you must write a procedure for each type of weld and don't for get to look at your perameters in sec.3 & sec.4 when you write the wps.(AWS does have code for writting wps's) but I'm not in my office to give you the number. If you use the code to support your work you won't have to defend your wps's only qoute the sec. of the book on the wps where you found the information. If you have done the job correctly and they disagree with the code there is nothing you can do because when it's in BLACK and WHITE and they disagree ;what is there source of referrence?
Autogenous welds may be made with a TIG torch using no filler wire (tack welding not requiring any face reinforcement) or a hand held TIG Gun which only produces a spot
weld of a certain size and spacing as specified in C1.1 and D1.3
Welders do not pick there wps's; either stated in contract requirements/as directed by the company welding engineer or the lead CWI will determine the most correct wps.
In some cases spacing is not to exceed 3'' and spots may only be 5/32'' in diameter and you need perameters for RSW and the machines are normally qualified on a daily basis using test specimens and tension pull.
You mentioned you also use "Mild Steel" (Carbon Steel) you may need to consult D1.1-? on some isues such as filler material 309 not 308.
Using the wps's will keep your welders consistent (same weld length, same spacing, same quality of work when you inspect and if not repair work begins and that's not cost effective. Don't forget this (Thichkness of the thinner part being joined) I will get the number for the code book for writting a wps unless someone gets to you first.

By Metarinka (****)

Date 05-23-2008 16:55

Thank you larry, that was extremely helpful, D1.3 and D1.6 look like they will contain the information I need.
As we all know there is a large spectrum of welding quality from the backyard and small shops with "Design by experience" up to Pressure vessels flight critical and nuclear code that call for procedure qualification, NDT, etc etc. Most shops fall somewhere in between. right now I would say we are definately pointing towards the "design by experience" type of philosophy. The engineers and fab shop actually seem pretty receptive to change and improvements in welding design and communication. However I don't think they are ready to make the jump to code quality work. I mentioned it in another post but I am the only engineer with any practical welding experience and welding design experience, there is no CWI, and none of our work is certified or specified by our customers.

We definately are to the point where our volume and quality are high enough that we could benefit from even very general procedures and codes to follow. I'll be pushing the approval of those code books hard on my boss, but I'm just an intern. I'm also going to try to create a general WPS for our GMAW and GTAW processes so that welders are using higher heat, faster travel and correct penetration and buildup.

Thanks for the help, I just got a weldment print on my desk about 20 minutes ago that has no welding symbols (ha!) a note from the welders asking to clarify welding order (or there's interference issues later on). Also they have a question asking 'fuse welded how? 1" @6" ctr-ctr or 1" @4" ctr-ctr'
The shop is definately ready for some correctly designed joints