Hey guys. I'm pretty new to welding. Only been doing it for about once a week for about 3 months. I'm using 1/8 inch mild steel flat plates with the edges beveled and I'm just doing a simple butt joint. I'm starting to get good looking beads, a few minor problems but overall good looking beads. I have the machine set at 60 amps, maybe a little less. My biggest problem is the metal always seems to warp, sometimes a lot, sometimes very little, but always somewhat warped. Before I weld I place a tack in the beginning, end and middle hoping to prevent warping, but yet it still does. However, most of the time I'm on the foot pedal almost at its max to keep the puddle flowing it seems if i let up on the peddle it seems the metal gets to cold. Is it wrong to keep the petal almost on it max ? Could it be my table? due to the slots that car cut into the table for clamping purposes I have a Nomad welding table I got from cyberweld.com. Here is how my beads look overall not bad in my eyes for the amount of time i actually weld. Other than the warping some times I get little pin holes in my beads not sure what there from. This isnt my best but the only picture i have heres an example of what there starting to look like you can also see the hole in the picture. So if anyone can give me some advise on the warping that would be great

Thanks
Brian

 

When you heat metal and cool it, it warps. You need to either compensate for the warp, or you need to weld with a heat sink (or both).

As for the pinholes, that would be impurities that you are getting caught up in your weld. Whether the impurities are getting imbedded by your grinder or you're using low quality metal etc.

 

Ok heat sink meaning get a big thick peice of metal to put under my flat plate to weld on much like people do when head flanges when making manifolds. what do you mean by compensate how exactly would I do that ? As for the pinholes what should I try first getting a new grinder wheel or trying to get better grade metal/ clean the metal better

Thanks for the info hopfully you will have some more for me. Thanks again
Brian

 

Heat sink is a metal which you lie under sheet metal you weld and it pulls out heat of the metal you're welding, so minimizes warpage. The best metal to conduct heat is copper, then second best is aluminium, so if you can't get your hands on a piece of copper, get aluminium!

Good luck

 

Even a bigger table will help with sheet metal. That small little table you have doesn't help to pull heat out. At the very least, you can get yourself a big steel C channel to weld on.

You can compensate by "prebending" the material in the opposite direction that it's going to warp. If you do it right, it'll warp back to straight.

Looks like you are grinding with abrasive wheels. Try a flap disc and then cleaning it a lot. The abrasive discs will embed material in the metal, the flap wheel won't be as bad.

 

I have to say that IMO it is impossible to prebend sheet metal, cause distortion is quite unpridictable...

Also you should try and use back stepping technique, which helps with distortion.

Cheers

 

Thanks guys I really appreciate all the info SovXietday yes I am useing an abrasive disc I will try and flap disc on the next bunch of metal I have. I also have some pretty thick aluminium lying around so i will also throw that under my metal and give it a try. If I have an aluminium heat sink and I'm welding mild steel do i need to move my ground clamp or is it ok having my ground clamp still clamped on the table. And RadekSkylark what meathods can you even use to preheat metal ? and you mentioned back stepping i'm unformilliar with that technique can you explane.

Thanks again for all your guys help
Brian

 

Yes, you can still clamp it to your table.

Why would you want to preheat metal??? Are you talking about aluminium?

You can see backstepping in this video starting from 10:51 -

http://www.youtube.com/watch?v=mzJR_qkO9wo

Good luck!

 

Just to add to this.

Metal warps no matter what. Whether it warps by a thou of an inch, or looks completely mangled. It warps to some degree.

The impurities are, as was once explained to me, bits of silica that are embedded with carbon steel. It'll be there no matter what. I could be wrong, but it makes sense to me.


Often you'll hear people tell you to weld in "stitches". I have found more often than not, this to be terrible advice.
When you weld in stitches, each weld section heats up, expands, cools down and contracts at different rates compared to the surrounding areas. Then what you end up with are a bunch of stitch welds that have expanded and contracted at very different rates.
I will actually weld thin stuff in a single pass if permissible. Usually resulting in minimal distortion.

That said, this will not always be the case and may not work for you or your situation.

I didn't read the OP's post. I don't read posts that are bunched out and a pain in the *** to read. So I may have said something already stated.

 

So the backstepping is just the "stitch" style welding basically?

 

No. Back stepping is when you weld, lets say and inch, and then you more the torch an inch ahead of the previous weld. And then weld into the start of the previous weld. If that makes sense...

 

Ok, that makes a bit more sense, thanks!

 

I found that copper works very well as long as you can get to the back of whatever you're welding. It's hard to find just a piece of copper unless it's pipe. But copper is pretty soft. I found that if you get a thin walled pipe, slice it vertically one one side, then slice it horizontally across the same side and then separate the section along the vertical seam you can make a heatsink tool. Its hard to imagine but basically it ends up being a flat end with the uncut section of pipe making a round handle on the other end.

 

Check the video I posted earlier at 10:51 and you'll see backstepping!

Cheers

 

i would say use a heat sink, clamp your metal down to help it from worping and above all read your puddle, you can pre set your machin but as your moving foward you shoul be using a little less heat cuz your plate is already hot, just keep your eye on the puddle learn how to read it. hope this helps it helped me when i started tig welding