New Welding Thread ?'s for beginners...MIG

[parsonsj]

Josh,



Yes ... that's how I do it.

One other thing to keep in mind about warpage: it is caused by heat from welding, but is also caused by the metal getting pulled in place. If you have a gap between the pieces of metal when you start welding, the molten puddle between them will shrink as it solidifies. That stress causes warping. That's why you want to get even spaced tacks all the way around and progressively close it so that the metal pieces don't move (as much) from the solidifying puddle.

jp

[Matt@RFR]

Key:

...so that the metal pieces don't move (as much) from the solidifying puddle.

For terminology, please see the attached drawing. It represents a section view of a fillet weld, also called inside corner weld.

Undercutting would happen, most likely, at the toe of the vertical leg of a fillet weld. It's when some of the base metal is pulled or washed into the weld, leaving a step at the toe of the weld. It's caused by lots of things...too hot, too fast, too shaky, etc.

Are the stringers the welds that go north-south in the pic? That is what I used on my cart before laying the circles (well, more like bloby puddles) on top of them.

The very same.

What you're talking about is a root pass, and a cover pass. You would probably have been fine running that in one pass, as long as you moved ahead and buried the arc in the root before filling up the rest of the joint, but it's hard to say without seeing your weld prep.

(EDIT): On that drawing, the 'fusion' arrow should be pointing at where the toe meets the base metal. I also wanted to mention that welds are sized by the length of the shortest leg, NOT the throat.

A good rule to live by is the weld should be as big (leg length) as the base metal is thick (thinnest member).

[Camaro Zach]

you can butt each tack up against one another but unless you get each tack right ontop of the other and get alot of heat on it you wont get 100% penetration inbetween each tack. here are some pics of what im talking about.

[JoshStratton]

Josh,
That's why you want to get even spaced tacks all the way around and progressively close it so that the metal pieces don't move (as much) from the solidifying puddle.

jp

Oh boy. Now that is something I would have never thought of. No wonder body shop guys make 50+ bucks an hour.

A good rule to live by is the weld should be as big (leg length) as the base metal is thick (thinnest member).

This rule would not work for sheetmetal, would it?....god I hope not. Something like 18 gauge would be pretty hard for me to do.

After seeing your definitions, I totally realize how ugly my welds are. They are too wide and have a lot of undercutting. Is this something that could possibly lead to a dangerous situation? I plan on using my cart so I can get under it and work. I had the whole car on it, minus the front sub, at one point. It has only gotten MUCH lighter since.

[JoshStratton]

you can butt each tack up against one another but unless you get each tack right ontop of the other and get alot of heat on it you wont get 100% penetration inbetween each tack. here are some pics of what im talking about.

Zach,

Thanks for the examples. I have actually been able to get a few sheetmetal welds to look like those! woohoo! I think my biggest issue is how I apply them to what I am doing and where to put them.

Am I seeing these correctly?

On the first pic, it looks like you bent the metal down and tacked the end so it would stick. That second pic looks like you did the rest of the tacking on the underside. Did you also lay a weld on the other side (which appears to be the outside of the piece)? What kind of weld did you lay down on the outside if you did weld that side? In that last pic, is that what it looked like when it was all grinded down and finished?

[parsonsj]

Hey Matt,

After looking at your picture, it seems the penetration in the diagram is shallow. Do I have that right? Is that enough penetration for a structurally sound weld?

Just curious, as I always want to learn more more more about this art/science called welding ...

jp

[Matt@RFR]

This rule would not work for sheetmetal, would it?....god I hope not. Something like 18 gauge would be pretty hard for me to do.

After seeing your definitions, I totally realize how ugly my welds are. They are too wide and have a lot of undercutting. Is this something that could possibly lead to a dangerous situation? I plan on using my cart so I can get under it and work. I had the whole car on it, minus the front sub, at one point. It has only gotten MUCH lighter since.

No, that rule of thumb pertains to any joint besides a butt joint. Butt welds don't have legs, so you're left judging the weld "size" solely by penetration.

There's two downsides to undercutting. 1) It creates a stress riser. Stress risers usually only fail when under cyclic loading/vibration. 2) At the deepest part of the undercut, if you can picture this, the metal is thinner there. So basically, if the weldment is over engineered with material selection, it will probably be fine.

I'll leave the decision up to you, as to whether it's safe or not. Too much liability involved for anyone but you to make that call.

John, that's a tough question to answer, since it depends so much on the end use of the weldment, and how it was engineered (additional gusseting, supporting elements of the weldment, etc.). But, generally speaking, my quickie drawing depicts good penetration.

You can test your own welds: Section the weld, polish to a semi-shine or so, and etch it with muratic acid, or equivelant. That will show you exactly what's in my drawing.

[parsonsj]

generally speaking, my quickie drawing depicts good penetration.

Very interesting. Thanks!

jp

[Camaro Zach]

Zach,

Thanks for the examples. I have actually been able to get a few sheetmetal welds to look like those! woohoo! I think my biggest issue is how I apply them to what I am doing and where to put them.

Am I seeing these correctly?

On the first pic, it looks like you bent the metal down and tacked the end so it would stick. That second pic looks like you did the rest of the tacking on the underside. Did you also lay a weld on the other side (which appears to be the outside of the piece)? What kind of weld did you lay down on the outside if you did weld that side? In that last pic, is that what it looked like when it was all grinded down and finished?

the pics got thrown out of order when i posted them. But the first pic shows an outside corner weld. basically i just cut all the way down the piece but left that 1/4 or 3/8" at the end to hold the 2 pieces together when i bent them, then i tacked the other side so the pieces wouldnt spread apart. The second pic shows the uneven penetration on the corner weld and the butt joint. the third pic shows the top of the butt weld before it was finished. and the last pic shows what they look like ground down (although i didnt finish the butt joint because someone needed the extension cord)

[JoshStratton]

What are your thoughts on using an auto darkening helmet? I had a chance to try one out for a few minutes a while back. It was some Swiss made brand that was not battery operated...i think it was Solar? I really like the way it worked, but didnt know if it protected enough to justify spending 350 bucks on one. I think it was called an optima Sattellite.

[Travis B]

we have nothing but miller helmets in our shop they are worth there weight in gold! I can't weld without an auto darkening helmet! If you buy one just bite the bullet and get a nice one

[JoshStratton]

They have a good price too.

http://cgi.ebay.com/MILLER-ELITE-AUT...QQcmdZViewItem

[Travis B]

They have a good price too.

http://cgi.ebay.com/MILLER-ELITE-AUT...QQcmdZViewItem

yup thats what I have but with some cool paint that is coming off....lol

[DRJDVM's '69]

This thread is great because... I just had my first welding lesson today !!!

There's a local trade school that does "private, byt the hour" lessons, so I went in today and got started. Today the instructor did a basic run down of MIG welding and then had me practice laying down beads for a "filler weld" (is that right ??). Basically an angle piece of iron where I just layed down bead after bead to build up a section.

There's definitely and art to doing this. Gettting my hand steady and going in a straight line at a consistent rate and distance is gonna take some practice. SOme of my welds looked pretty good for a first timer and other looked like crap.

I'd like to get a book to use as a reference when I have questions. I'm hoping this well also help me learn the vocabulary and some of the basics of what I need to do and why. Also there are some many variables when it comes to what your welding and why etc.

Any recommednations for a beginners book ???

[Matt@RFR]

"filler weld" (is that right ??)

Bead-on-plate weld. It's not a weld, actually. A weld joins two seperate pieces. What he's having you do right now is simply getting used to the sights and sounds of MIG welding. That's really all it's good for.

I don't have any books that I recommend. Too many of the books I read as a beginner have outdated material, personal preferences that the author states as fact, and plain bad advice.

[Texas Bob]

This thread is great because... I just had my first welding lesson today !!!

There's a local trade school that does "private, byt the hour" lessons, so I went in today and got started. Today the instructor did a basic run down of MIG welding and then had me practice laying down beads for a "filler weld" (is that right ??). Basically an angle piece of iron where I just layed down bead after bead to build up a section.

There's definitely and art to doing this. Gettting my hand steady and going in a straight line at a consistent rate and distance is gonna take some practice. SOme of my welds looked pretty good for a first timer and other looked like crap.

I'd like to get a book to use as a reference when I have questions. I'm hoping this well also help me learn the vocabulary and some of the basics of what I need to do and why. Also there are some many variables when it comes to what your welding and why etc.

Any recommednations for a beginners book ???

I just picked up my text book WELDING Principles and Practices 3rd edition by Sacks and Bohnart for about $70 used for an Intro to Welding class at college. 30 chapters and mega thick, I have no idea what I'm getting into but after reading 3 chapters (my wife called me a nerd as school doesn't start till next week) I can follow this thread pretty well and I have zero experience with welding.

Bob

[O&C Racing]

I just thought that I would throw out an opinion on machines. I've been using a Millermatic 185 for over 6 years now. I never really liked the fact that it had 7 settings for voltage. When working on thin sheet metal It needed a setting less than one but sometimes needed something in between one and two. So you would have to get creative with wire speeds to get a good weld.

So over the weekend a friend needed a welder to replace his, so I sold him my 185. I ordered a new Millermatic 251 and it got here today. So I set it up and started welding on some scrap of varying sizes. The only thing I can say is this thing rocks. The arc is much more stable and it welds sheet metal like a champ. It also laid down some nice welds on 1/4" stuff with ease. I would highly recommend this to anyone looking to purchase a new machine. I got it from cyberweld.com for a hair over $1700 with free shipping. None of the local dealers that I deal with would come close to matching the price and not having to pay sales tax was a bonus as well.

Now I just need to do something with this 180 SD Tig Runner I bought last year. I think I'm ready for an upgrade in that department as well. Just need to do some more research on Tig machines.

Curtis

[JoshStratton]

Hey guys. I wanna bring this thread up again if that is ok.

I welded my first body panel last weekend and I think it turned out pretty well. I grinded the welds down so any pics I would get probably wouldnt show much.

However I didnt get any warpage, the penetration is nice and it seems pretty solid.

I wanted to thank you guys for all your help (Matt and John especially while not discounting the help from others).

I still have 2 questions though. I did the spot weld pattern of every 3 inches, then 1.5 inches, then .75 inches, then a finish bead. The finish bead is what I am not sure about. I mean it turned out nice, but I think I could have widened it more. I was welding 18 gauge steel to 20 gauge steel with a half-circle pattern ))))) on an overlap joint. The beads were not even 1/4 inch wide.

With steel that thin, do you think I can widen that or should that be enough?

Also, after grinding it all down, there were still a few small gaps in the weld scattered around. For finishing body work that will be seen, such as this, should I go back and fill those in with spot welds or do body shops just putty over them? Basically, I guess I am asking how to account for these.

Thanks!!


EDIT: Let me correct my language above. The gaps are not in the overlap joint, I am really not sure how to describe them. There are small holes where the weld did not fill in. Man I hope someone knows what I am talking about. LOL

[Camaro Zach]

IMO you should fill them all in, not only does it make it look better but will reduce the number of weak spots and will prevent any moisture from seeping in under the paint/filler

[JoshStratton]

Ok. Will do. Thanks!
I am just glad you knew what I was talking about.