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Up Topic Welding Industry / Technical Discussions / correct aluminum tig weld width
- - By wesley lewis Date 03-09-2012 06:25
Does anyone know the correct width for an aluminum weld to be when welding a butt weld on 3.5-5" .065-.083 thick pipe?  I have always been told for 14 years that your weld should be 3X the thickness of the material you are welding and I have this "welding guru) at work that says he use to be a welding teacher, says that it has to be 3X the width of the filler rod you are using. Who is right?  Cause he has the big wigs at the company believing that. For example, if I attempt to weld a drink can together using 1/8" rod ( just saying, cause I know it can't be done with that size) means the "correct" weld would have to be 3/8" thick. In my book that just sounds completely ignorant. By the way, the teacher says I can't weld right and my welded have been to SEMA and to various shows and he can 't hardly weld aluminum. I just want to know the truth and thank you in advance
Parent - - By aevald (*****) Date 03-09-2012 06:53
Hello Wesley, most codes are mum on weld bead width and generally for good reason. Aluminum, by nature, is rather an oddity with regard to heat input, which is generally why there are limitations in many cases for bead size/width as they apply to the majority of the various metals and types. Things such as time at temperature and other variables can influence optimum welding conditions for a given welding scenario. If you progress slowly and dwell in the puddle yet produce a small finished bead size that isn't much different than if you weld at a very high amperage and apply a larger bead and yet travel quickly while doing so. It can be the amount of time and how much "soak" that is present that could adversely affect a particular weld bead. Another consideration could be the alloy that is being worked with. If it is a heat treatable alloy and after the welding is done it will be "normalized/heat treated" then bead size might be a moot point. Some bicycle frame manufacturers are an example of this, they will apply over-sized welds to provide for smooth transitions at weld points/junctures and after completion of the welding the frames will be fully heat-treated, use of particular filler alloys allow for heat-treating of both materials and welds. Thus over-heating or any other issues are dealt with before they become an issue. There are just too many variables that could come into play to make a blanket statement either way in regards to your question. I would however, share your views with regard to thickness having a greater bearing on bead size than diameter of filler used, other variables not withstanding. I hope this makes some sense, there are likely others who could explain this much better than I and should they chime in I am sure that we'll both learn something. Best regards, Allan
Parent - By vagabond (***) Date 03-10-2012 10:19 Edited 03-10-2012 14:15
I don't believe it is in a code anywhere however a popular company specification is that each individual pass should be no larger than 3 times the width of your electrode.  This prevents soak, heat input etc.  That doesn't mean it can't be smaller than your electrode.  I would have trouble with any logic that says it has to be 3 times the thickness of what you are welding on because that just doesn't work out.  When I was a welder I used to make my roots as close to the diameter of one filler wire (or bare electrode if using SMAW) as I could.  I tried to make my hot pass twice the diameter and all the beads after that about twice the diameter as well or more.  There are a lot of variables though as aevald has correctly pointed out.  Some places will still let you lace a big old cap on there with one pass,  uphill.  Doesn't necessarily mean it is a good practice.  It seems to me that carrying any more metal than you have to while welding aluminum pipe would be a real pain in the arse.  But that's just my .02.  Take it for what it's worth. :cool:
Parent - - By MBSims (****) Date 03-10-2012 13:52
For welding aluminum thin-wall tube or pipe, the 3x base metal thickness may work well. For heavier wall thickness, it would not.  That would mean for 3/8" wall pipe the weld would be 1-1/8" wide. But, once you get over 3/16-1/4" thick material, you would want to start beveling the ends instead of using a square groove.  In your case, the 3x bead width is probably ensuring you have good penetration on a square groove butt weld. In cases where 3x the filler wire is used, the typical reason is to limit heat input.  I would say if you should stay with the 3x bead width if it is working well for you on the pipe thickness you are welding, you are getting the required amount of penetration and weld quality, and there are not issues with welds failing due to excessive heat input.
Parent - - By 357max (***) Date 03-12-2012 22:15
Perform a welding procedure qualification with two extreme weld sizes. One super small/narrow and one super wide/large calculating the heat input and perform the mechanical tests. Was there a change in the mechanical strengths that matters to the product? Write up the procedure for the desired mechanical strength. A good test is worth more than a thousand opinions; in my humble opinion.
Parent - - By aevald (*****) Date 03-12-2012 22:49
Gotta agree with you there 357max, I believe that is one of the reasons why many of the codes that deal with aluminum welding/certification/qualification do not have prequalified procedures. I believe they require individual qualifications dependant upon the particular variables and scenarios for a given application. Thank you for chiming in. Best regards, Allan
Parent - By Tommyjoking (****) Date 03-14-2012 17:49
From a simple mechanical standpoint Aluminum is just a different animal because of it's heat dissipation and the way it puddles.  All the variables that affect the heat input necessary to get it to wet properly determine your overall deposit size.  You can make the same exact weld with a 1/16 rod as a 1/8, so that rod vs width "rule" seems pretty arbitrary and useless.  I say do what it takes to make a sound weld and save the calipers for the machine shop.
Parent - - By MoltenMetal Date 05-29-2012 19:17
Hi Guys,
I am a student welder reading through this post as asignment.  After discussing with my instructor and reading the D1.2-83.  We didn't find any definate answer to this question.  We figured that the most important varible that would dictate the size of your weld bead would be heat input.  Its my uderstanding that material thickness and the size of your filler rod both greatly affect heat input to the parent material.  My best answer to your question is that bead size is going to be dictated by how much heat input you need to keep from over heating the base material.
Parent - - By 803056 (*****) Date 05-29-2012 20:26
I am forced to ask the question, "How hot is too hot?"

The last time I tried to weld, I had to heat the base metal above it's melting temperature. Is that too hot?

Al :eek:
Parent - - By jwright650 (*****) Date 05-30-2012 12:21
Too hot is when it falls out onto the floor and you can see your feet while welding. :twisted:
Parent - - By 803056 (*****) Date 05-31-2012 02:59
Now that is a response I can relate to.

Al :eek:
Parent - - By jwright650 (*****) Date 05-31-2012 13:06
so.....you've welded aluminum before:razz: It just gets shiny when hot, and doesn't really change colors like steels do.
Parent - - By welderbrent (*****) Date 05-31-2012 13:12
The most fun is when I swing into the shop because they took in an "aluminum" repair job while I was out.  Without even a close look you fire everything up and almost right away have this huge hole... WHAT ON EARTH??  Oh, this isn't Aluminum.. pot metal, junk... Sorry, your part is in even worse condition now. 

Sometimes, depending upon what it is, I can fix them.  But those metals are not my expertise.  Alum is bad enough for me but pot metal is more than a little difficult.

Have a Great Day,  Brent
Parent - - By jwright650 (*****) Date 05-31-2012 13:14
I always wondered why they called that stuff "pot metal", but then I realized they must throw whatever they have on hand that day into the pot and cast the part.
Parent - By welderbrent (*****) Date 05-31-2012 14:43
:lol:  :lol: 

Actually, I think someone was smoking, and INHALING, while making it so didn't care what went in the pot.  (I'll let you decide what they were smoking)

They messed up a batch and then had to find something to do with it so as not to lose money.  YEAH, see what we invented.  We can save money using this cheap junk stuff instead of the good stuff on these automotive parts.  No one will ever know the difference.  :sad:

Have a Great Day,  Brent
Parent - - By WeldorJoe (*) Date 06-06-2012 18:09
One quick way to identify those materials is the color/hue of the arc when GTAWelding.  Aluminum is white, "pot metal" is purple, and magnesium is bright green.  Before preparing the joint I would run this test.  Then I could determine the extent of hot shortness and if I had to support the weld area.
Parent - By welderbrent (*****) Date 06-06-2012 20:38
Yes, there are color differences.  But sometimes I get in too big a hurry and if the material is somewhat thin I have a hole before I know what happened.

Have a Great Day,  Brent
- - By 803056 (*****) Date 05-31-2012 15:51
Pot metal is typically zinc alloyed with other metals such as aluminum. The composition varies from pour to pour, company to company. The pot metal is die cast into various parts that are not subject to much stress.

A common example of a use for pot metal is carburetors bodies used in the older model cars. As a matter of fact, an older, much wiser welder that I used to consult with used to break up old carburetors’ and cast them into rods. The rods would be used to torch weld other broken pot metal castings. 

Best regards - Al
Parent - - By jwright650 (*****) Date 05-31-2012 17:27
Interesting "pot metal" welding procedure Al...wonder if that would require a PQR or is it prequalified in FC2002....Bwhahaha :yell:
Parent - By DaveBoyer (*****) Date 06-02-2012 05:54
Those aluminum solder rods You see at car shows will work on Zamak [zinc/aluminum/magnesium/copper] die cast parts and some  "pot metal" depending on the pot metal.

Pot metal is a lower grade of zinc alloy, in the old days including lead,tin & cadmium, it has generally poor qualities, some old parts just crumble. There are no real specifications for "pot metal"

The aluminum solder melts at about 730f [depending on brand] about the same as Zamac.
Up Topic Welding Industry / Technical Discussions / correct aluminum tig weld width

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