Mig welding hints and tips

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metiz
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Mig welding hints and tips

Post by metiz » Sat Jan 16, 2010 5:18 pm

Hey all

I've recently bought myself a big tank of welding gas. I think it's 90% c02 and 10% argon or something like that. Before, I just welded without gas. The welds were realy shitty and oxidised but did not penetrate the thin steel and the oxidation was superficial. recently I thought it'd be a good idea to start using gas since I want to start selling engines and I don't want to have to grind all engines down.

But the welds WITH gas are by chance even shittier then the welds without gas. I make all my sheet welds by making one spot weld after the other. With a contious weld, I blast through the steel, even at the lowest setting. But the wire CONSTANTLY sticks to the weld tip and after almost every spot, I have to force the wire out of the gun again by holding it against my vice (with the ground connected to it) and blast the wire of like that. The welds are not oxidised but are realy shitty non the less. If there's a seem, and there usually is one of about 1/4mm due to slight cutting and grinding mistakes, The weld wants to go either to the left or right, leaving a burned out hole at the edge. when I try to fix this, the weld blob wil either adhere to the left or right, leaving the hole open. This is REALY anoying.

Because my welding cap is pretty much shit, I use it as following: I put it on my head and push the cap down so it partially covers my face. At this point I can still look underneath it at my project. i position the welding gun and tilt my head down so that the plastic of the mask covers my line of sight. I then make a spot weld and check the results. Rince repeat

All in all it's a very labout intensive part of construction and with these welds, It's going to take even longer

Here's my question: can anyone give me some advice on how to get acceptable welds on 1mm 304 stainless steel? another welding tip, techique or whatever.

I've heard about some sort of welding flux (solar flux?) that you can smear on the bottom side of your to-be weld so that any acces heat can be channeled away and you won't end up with blobs on the underside. With that, a continues weld should be possible. Is this true? where can I get it? Any other tips maybe on how I can achieve a continues weld without blobs on the underside of the material?

Thanks.
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Re: Mig welding hints and tips

Post by Viv » Sat Jan 16, 2010 7:33 pm

Hi Metiz

Preparation preparation and preparation! make this your new mantra! to get a good weld you have to do some good preparation work first, the fit and line up of the parts to be welded must be as near perfect as you can manage, shitty line up equals shitty finished weld, very thin work can be direclty butted together, thicker work 1mm up needs a "root" gap.

Just before you begin welding you must clean the weld area first with an abrasive to remove the oxide layer from the stainless steel, that shiny stainless steel is shiny because it grew an oxide layer of chromium oxide to protect itself (304 grade Chromium, titanium oxide for 321 grade), the oxide melts at a higher temperature than the base steel so you end up setting the welder for too much heat, that's why you burn through or end up with seagull shit all over the weld ;-)

In a nut shell "Clean the oxide layer off or fail!"

Gas, if you have brown shitty deposits on the weld area then you may simply have the gas turned up to high, if you hold the torch up it should just be audible, a slight hiss, if you can hear a lot of hissing then its too high, a high flow of gas will entrain air in to your weld and the oxygen will oxidize your weld! the opposite of what you want the shield gas to do ;-)

Flux, the back side of the weld (root) is exposed to air, normally we back flush with shield gas to protect it from air, the weld heat will cause atmospheric oxygen to react with the molten metal and cause oxide (bad) a layer of flux (solar flux) or shield gas will keep the air away and stop the problem, for flat sheet you can weld against a chiller bar (lump of metal) and this will keep the air away too (not so well as gas)

Basics,
Do a test fit up of the parts and clamp them properly and firmly for welding.
clean the surface of oxide and oil contamination.
Test the gas regulator works! cheap shit regulators are a known cause of bad welds!
Keep the gas flow low to cover the weld area and push the air away, do not turn it too high and add air to the weld area.
Do not weld in an area with fans blowing across the weld or the door open with a wind blowing around the workshop, it bows the shield gas away.!

Hope that helps

Viv
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metiz
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Re: Mig welding hints and tips

Post by metiz » Sat Jan 16, 2010 7:43 pm

Hey Viv

Thanks for the imput, Ill give it a try. couple of things though. At the moment I am welding with the lowest possible setting on my (230v) welder and It will still create lumps of crap on the other side of the weld.

Could all the possible errors I make also attribute to the wire sticking to the welding tip?

Oh yeah also something weird, in reply to your "shitty regulator" When I press the button on my gun, first gas comes out and then wire and since I spot, I usually keep the button partly pressed between spots so the gass flow is constant. A strange and loud even noise comes from my regulator: the preasure gage needle is twitching back and forth at break neck speed causing the noise.
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Re: Mig welding hints and tips

Post by ace_fedde » Sat Jan 16, 2010 8:04 pm

Metiz,
metiz wrote: With a contious weld, I blast through the steel, even at the lowest setting.
Unfortunately that's normal when welding sheet with MIG. You all the time have to "move around" the workpiece to keep the weld from collapsing. Unless,... see last comment,
metiz wrote: But the wire CONSTANTLY sticks to the weld tip and after almost every spot,
That might have nothing to do with the gas but with the simple fact that the tips are disposables. When worn out the thread will stick to it. (also there are sprays available to prevent sticking a bit, they work)
metiz wrote: I have to force the wire out of the gun again by holding it against my vice (with the ground connected to it) and blast the wire of like that.
I know an easier trick for that but I can't explain it with words, have to show you.
metiz wrote: I've heard about some sort of welding flux (solar flux?) that you can smear on the bottom side of your to-be weld so that any acces heat can be channeled away and you won't end up with blobs on the underside. With that, a continues weld should be possible. Is this true?
Clamp an aluminium rod under the weld, it will not stick and transport the heat away preventing the weld from collapsing.

Cleaning, like Viv explains, is always important but to my opinion not your problem here. I've been welding a little with your set-up (if you remember) and it worked. So it are your skills mate :lol:

I have to visit you soon to bring the injector lines, and so it seems for some welding instructions, but I still didn't fix my car...

Fedde
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Re: Mig welding hints and tips

Post by Viv » Sat Jan 16, 2010 8:16 pm

Hi Metiz

Yes! ;-)

Ok sorry lets start again, you have to do all the steps to get the finish line, you cant miss any thing out with out suffering consequences.

A weld pool contains the base metal plus the addition of the filler wire plus oxides formed from contamination such as air or oil, the fluidity of the weld pool is governed by these factors and by the addition of elements such as silicon from the filler wire, silicon alters the fluidity and creep (how the pool moves along the root).

All of the above affects the way the wire tip and arc between it and the weld pool behave, imagine dipping a pencil in to cold thick gooey treacle or the same treacle that is hot, make sense?

Next is wire speed and torch cleaning

The torch must be clean and the gas holes clear and free of crap, the shroud must be clean and the wire guide tip must be clean, free from wear, the right fricking size!!! don't doubt for the moment that a worn or incorrect tip will be ok, it wont ;-)

Check the wire runs free and consistently, trigger the torch and run off a few meters of wire, it should run nice and smooth, try moving the torch around while you do, any speed changes in the wire will reflect directly in the weld quality, crappy wire feed equals crappy welding, every time ;-)

You may need to replace the liner in the torch if you cant fix the problem, they do wear out, the wire must be clean and corrosion free.

Wire feed motor and rollers, make sure the rollers grip the wire properly and the motor runs smoothly while feeding out wire.

If the wire speed is not consistent then the arc gap between the wire tip and weld pool will not be consistent! arc gap sets temperature hence penetration, how can you weld if it changing?

What are the settings you have? wire speed, current?

Another test is to set every thing low, lowest wire speed lowest current, set the gas to a very low setting so it just can be heard hissing from the torch, take a peace of clean (grind it with abrasive) flat sheet a 1 or 2mm thick, hold the torch with the shroud 5mm away from the sheet, set your self up so you hand (in a glove) can support the torch steady and run along the sheet, practice so its smooth.

Now push the torch away from you so you go over the top of the weld bead, IE the wire is fed in to the top of the weld pool and the weld pool is under the torch, do not pull the torch away from the weld bead so the weld pool is following the torch! your weld bead should not have to chase you around the work peace ;-) you should push the weld bead were you want it to go.

You should be able to get a clean bead in this practice run because we have cut out the other variables, oxides, gas problems, fit up, ect

If you have variable wire speed try altering it with one hand while the other continues to run a weld bead, see what happens '-)

Viv
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Re: Mig welding hints and tips

Post by Viv » Sat Jan 16, 2010 8:25 pm

metiz wrote:Hey Viv

Oh yeah also something weird, in reply to your "shitty regulator" When I press the button on my gun, first gas comes out and then wire and since I spot, I usually keep the button partly pressed between spots so the gass flow is constant. A strange and loud even noise comes from my regulator: the preasure gage needle is twitching back and forth at break neck speed causing the noise.
Hi Metiz

Sorry I just read your post properly after answering, my bad ;-)

Yes your regulator is shitty and more than that totally f*cked going by the noise it makes ;-) it should all be noise free and smooth, I had a cheap 100 euro regulator that caused months of heart ache before i found out what was going on, replacing it with a new one fixed the problem, the difference was like night and day!

The first rush of gas or pulse shall we say is to clear the weld area of air IE purge the oxygen, next it settles to a steady flow for shielding the area ready for the wire feed to start and strike the arc.

Keeping the gas flowing between spot welds is bad and stops the gas purge working properly, use the trigger button on off to spot weld, don't hold it partially on.

If the weld area still contains air when the arc strikes the wire will probably stick as the arc is not struck properly and the plasma is not formed correctly

Viv
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Re: Mig welding hints and tips

Post by Viv » Sat Jan 16, 2010 8:49 pm

Hi Metiz

Here is a link to Lincoln welding web site http://www.lincolnelectric.com/knowledg ... weldss.asp you may find some of the articles in their knowledge section useful to you.

A question, what does your welding arc sound like? at these low settings it should be a nice continuous bzzzzzz with an occasional spark and bit of spatter thrown off as a contaminant gets burnt off, very intermittent arcing with lots of arc explosions are a bad sign

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Re: Mig welding hints and tips

Post by metiz » Sat Jan 16, 2010 9:28 pm

Hey Viv, Ace.

ok some info

First the max amp my welder can output. I'm looking at a diagram here with the 4 switches I have on my welder to control amps but they do not make a whole lot of sense.

L2 max (A) (2 buttons, 4 power settings)
80A----------55A--------60A--------70A----------80A(max 100A)
105A---------50A--------65A---------85A---------105A(max 120A)
115A---------30A--------55A---------85A---------115A(max 145A)

There's another diagram under that but I think that covers 400V (I use 230)
I usually use the lowest setting
When welding, There is a distinctivly low sound level. Not the "frying bacon" kind of sound but a very silent "continious short circuit" sound. I think that's the sound it makes when the welding blob starts to accumilate on the wire (see pic)
This regulator is brand spanking new btw :S (so is the weld tip btw)

Wire speed is variable from 0 to 10. I usually have it set at about 2/3 (.8mm 316LSI wire btw)

When welding on a flat piece of steel (regardless of leak throughs) I can get a pretty good "scale" welding line (if I say so myself)

There must be a bunch I've forgotten, please remind me if I have
Oh yeah, I have the welder hooked up to a free fuse: 230V 16A 3680 Watt max output

Oh yeah, Fedde, the alu pipe works a treat usually but only on straight welds. Mighty hard to get it bend inside the pipe :P
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Re: Mig welding hints and tips

Post by ace_fedde » Sat Jan 16, 2010 9:33 pm

metiz wrote: but a very silent "continious short circuit" sound.
Yes: Short circuit. The tip and the torch end should be isolated from each other. From the description of the sound it seems there are not anymore, probably due to drops of metal that ended up inside the torch.
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Re: Mig welding hints and tips

Post by metiz » Sat Jan 16, 2010 9:38 pm

ace_fedde wrote:
metiz wrote: but a very silent "continious short circuit" sound.
Yes: Short circuit. The tip and the torch end should be isolated from each other. From the description of the sound it seems there are not anymore, probably due to drops of metal that ended up inside the torch.
I'll do a thorough clean-up tomorrow of the gun, gas shield and tip
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Re: Mig welding hints and tips

Post by ace_fedde » Sat Jan 16, 2010 9:42 pm

And probably a higher thread feed, causing the thread to melt on the workpiece, not on the torch.
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Re: Mig welding hints and tips

Post by Viv » Sat Jan 16, 2010 9:59 pm

Hi Metiz and Fedde

Ok my Friend you have two problems, one is gas related, the brown residue is air contamination of your shield gas stream by the looks of it, this could be too high a gas flow, it could be the back of your shroud cup on the torch is not sealing properly and is sucking air in, could be the wrong size? yes they do come in other sizes ;-) look for one designed for welding thin sheet, it will have a smaller hole, if the gas is too high then it will entrain air in to the gas and push it in to the weld pool, the gas should flow smoothly and slowly out of the torch shroud cup so it covers the weld pool area, is the inside of the should cup clean? they fill up with crap pretty quick, is your workshop very drafty? a lot of air movement will displace the shield gas.

Your weld beads are not consistent, this could be caused by a number of things but you should be able to lay down a clean consistent bead on a flat plate, if you cant then you need to fix this before going on to joining pipes! welding two tubes together has its own problems in torch handling and welding skills, if you cant join two flat sheets together how will you ever joint two tubes? obviously you cant, focus on one problem at a time, minimize the variables or you will never fix this!

So I suggest you lay down a bead on a flat sheet and take a picture of it for us to see, then we can suggest fixes, do what I suggested before as a test.

The blobbing on your wire tip suggests you are pulling the torch along in front of the bead with a wire speed to low for the current and torch travel, again do that test I suggested pushing the torch.

Looking at the weld picture you did not clean the area harshly enough before welding, the oxide layer is tough you need to grind it off not just polish it up a bit ;-)

Hope that helps

Viv
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Re: Mig welding hints and tips

Post by Viv » Sat Jan 16, 2010 11:20 pm

Metiz looking at the picture of the welding you posted are you using a rotary wire brush to clean it up? is that the sort of tool you used to do your preparation too?

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Re: Mig welding hints and tips

Post by metiz » Sun Jan 17, 2010 12:31 am

Actually it's just a wire brush. Any preparation is done with some coarse sanding paper. I HAVE at some point started grinding of seems and the welds did get better (without gas) Guess I've forgotten it. I'll get cracking tomorrow
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Re: Mig welding hints and tips

Post by Viv » Sun Jan 17, 2010 1:05 am

metiz wrote:Actually it's just a wire brush. Any preparation is done with some coarse sanding paper. I HAVE at some point started grinding of seems and the welds did get better (without gas) Guess I've forgotten it. I'll get cracking tomorrow
Hi Metiz

Ah Ha! Ok do me a favor mate and throw the wire brush in the garbage bin ;-) your welding stainless steel now not ordinary steels, if you use a wire brush to try and clean up stainless steel ready for welding all you are in fact doing is contaminating the surface with plain steel from the wires used to make the brush.

The above really shows up in TIG work, the people I worked with for the new engines demonstrated that to me but they have a nice welding department too ;-)

The best things for cleaning the oxide layer off stainless steels ready for welding is an abrasive flap wheel of 80 grit or less, another option is an angle grinder with a flap disc not a solid abrasive disc (unless you are pretty good with it), the oxide layer is tough you need some thing brute to get it off ;-)

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