Question about welds - beginner...

[200T]

Hi!

I've just registered to ask you for some advice. The tutorial on the main page has been very helpfull, however, I'm a bit unsure and some questions remain.

I hope you can understand everything, I'm trying my best. I'm from germany so my english is not the very best and my grammar might be a bit weird. Appologies for that!

I've been practicing a lot lately.

So basically, my question is, is this OK?

Steel is 1mm sheet. Welder is a Güde MIG190 (30-200A, 230V). 0.6mm wire and Argon gas with 18% CO². Current was set to level 2 (of 8), wire speed to 15 (digital range from 5 to 99). I set a tack every 2cm and then used the 'step back'/'pilgrim step' technique to form a continuous seam and keep distortion at bay (one spot after the other, as far apart as possible).

When ground back, there are no light leaks, the seam is solid and through. However, I'm in doubt of the back side of the seam, showing only punctual burn through. The spots however sit in the middle of the sheet.

As you can see, there are still some 'cold' welds. I've solved that problem with using a higher power setting for the last joining spot (when joining the seam sections). Or grinding the weld back and then set the last joining spots. Which worked.

So; does this look OK for a non-continuous butt weld? Can I attack a car with my current skills?

Next the plug-welds. Again 1mm sheet, power setting at 3, wire speed at 17. 5mm holes.

I'm quite happy with those. Do you agree? When pulled apart, the weld doesn't separate and rather rips a hole in the sheet.

Thank you for taking the time & awnsering my questions!!

Best regards,
Jan

 

[keith19]

Hi Jan, welcome to the forum

For 1 mm sheet, your work looks pretty good to me. Although we try to get the tack welds touching and joined up, it can be seen in your first picture that when ground flat your welds are close enough to form a continuous seam, so that is okay, too.

On our Ministry of Transport Test, (MOT), if the welds are left rough, or not dressed down with the grinder, they must be seen to form a continuous seam. So here in the left-hand side of your picture you would need to make your tacks blend into one another all along the seam, or they might not pass. But if you ground them down, as in the right-hand side of your picture, the welds would pass!

Don't worry about perfection with the penetration too much in 1 mm steel. It is not usually under great stress, so it is not necessary to always have complete penetration. The difference in complete penetration at that thickness, and blowing a hole, is very small.

The plug welds look very good, considering you are using 1 mm thickness. Some look a little high, but they can be ground down, so I think you can feel happy with them. Most people blow through when plugging 1 mm; the settings on the machine have to be just right, and you have to move quickly!

So, all is good! But check with a vehicle testing station about if they require a continuous seam weld on repair panels, before you repair your car.
By the way, your English is excellent, too!
Regards,
Keith.

 

[200T]

Hi Keith!

Thanks a lot for your reply! Great! So I'm on the right way...

I've actually started with 1mm - I'm having more trouble with the thicker stuff

Our TÜV doesn't like joining welds on the edges on stressed panels. Butt welding patches is OK, stressed parts have to be overlaping and plug welded. That's about it. They do like well dressed up welds

Thanks again!

Regards,
Jan

 

[mrcheese]

Hello Jan,

Your first attempt at plug welding looks way better than my first go!

For dressing the welds can I suggest that you use flap discs.

http://www.weldequip.com/ceramic-flap-discs-115mm.htm

Much better than a standard grinding disc. You can get almost invisible results.

Paul.

 

[penetrator]

Going well try a 10 mm step back, and your Australian is very good, practice makes perfect.

 

[200T]

Hi!

@Paul: well, it's not my first attempt in those pictures - rather my latest after a few hours of practicing

I'm using a flap disc, theo ne I use in the picture was just badly worn so the result isn't great. Normaly I use these lethal looking discs, they appear transparent when spinning and you can see through the disc where you grind.

They'r just a bit expensive (pay more for less - awesome! )

@penetrator: I'm giving 10mm steps a try, thanks!

Regards,
Jan

 

[mrcheese]

I have been using the same type of disc. At first I was worried that the gaps would cause the disc to jam if caught on an edge, but I have not had a problem so far.

I pay about £3.50 from my local tool shop. I used about 8 of them when I repaired my Discovery.

 

[200T]

Hi!

To keep this updated:

Had a first go on the car

Improvised sheet folder:

To get the contour of the fold right, I quickly welded a Mini head stud to the folder...

That's done the job quite good. With a bit of cutting, bending, bashing and swearing I got the bend to make a slight kurve:

Cut off too much...

I improvised by folding a bit of copper sheet and put it behind the gap. This worked a lot better than I thought it would, and I got the gap closed quite easily Bit of a surprise, I didn't think it would work that well...

Then put on some lead

And then some spray filler and the base coat

And painted. Not 100% even, next time I'll invest more time in sanding down the lead and probbably going to use a fine coat of filler. The glossy paint reveals any slight indentation - much more than I thought it would. Once more a lesson well learned

Cheers,
Jan

 

[Chickenjohn]

Great Job! repair is almost invisible. Nice to see someone else using body solder (lead loading) for car repair finishing! :-)

 

[keith19]

Excellent first job, Jan! Looks good, and nicely welded. Shows careful work, and attention to detail. Well done!

 

[200T]

Ok, dragging this up once more... My welds are getting better and better, and I'm almost satisfied with them. And I rarely have insufficient penetration. I'd guess 90% of my welds penetrate OK.

However I still have some questions...

- First; the brown residue after welding... Is this normal or can it be avoided? For example here: http://img809.imageshack.us/img809/4026/ht7u.jpg

- Second: Does this sound about right? I know, it's hard to hear especially with a bad microfone. But perhaps someone's able to at least tell me it's not totaly wrong

http://www.youtube.com/watch?v=VYVSUfTVqjo
(what happend here is... I burned a hole which I had to close)

http://www.youtube.com/watch?v=9XoInhtA8-k

- and last one: my spots always have that dimple on top (like in my first post). Could this be down to too much gas or too much 'burn back'? A mate told me he never gets them... And if my observation is right, thedimple forms after I release the trigger. So is this normal or can/should it be avoided? And how?

Thanks again you guys! I've learned so much here - I hope I can give something back at some point

Regards,
Jan

 

[keith19]

Hi Jan,
don't worry about the bit of brown residue, it seems to affect some metals more than others. Whether it's due to tiny surface oil particles or other residues I'm not sure, but you will get more of it if the gas is turned down too low.

Re the crackle on your first youtube movie, it sounds just a little harsh to me, I like it sounding a little softer than that, but hey, that's maybe just my personal preference. It sounds slightly softer on the second movie, but that might be just because the microphone is outdoors.
I think maybe you could try turning up the wire speed a fraction too; try turning it up until it starts pushing the torch back at you, then gradually turn it down. Your movies show it burning back into the shroud after only a second or two of tack welding.

What size wire are you using there? Sometimes if you are using 0.6 and it burns back too quick, you can try 0.8 instead, although you will need to turn the wire speed down accordingly.

Re the dimple on top, sometimes these are impurities or gases boiling their way to the top of the weld. Do they only occur at the end of your run, where you lift the torch off the job? If so try moving the torch back over the run slightly before you lift off.

 

[200T]

Hi Jan,
don't worry about the bit of brown residue, it seems to affect some metals more than others. Whether it's due to tiny surface oil particles or other residues I'm not sure, but you will get more of it if the gas is turned down too low.

Ok, thanks.

Re the crackle on your first youtube movie, it sounds just a little harsh to me, I like it sounding a little softer than that, but hey, that's maybe just my personal preference. It sounds slightly softer on the second movie, but that might be just because the microphone is outdoors.
I think maybe you could try turning up the wire speed a fraction too; try turning it up until it starts pushing the torch back at you, then gradually turn it down. Your movies show it burning back into the shroud after only a second or two of tack welding.

I'm curently using a wire speed of 14 (digital scale from 05 to 99) and power setting 2 - for 1mm sheet. At 15 it sounds 'smoother' but I have a lot more trouble with burning holes... 14 seems just about right. But I might go backto 15 then and reduce welding time

What size wire are you using there? Sometimes if you are using 0.6 and it burns back too quick, you can try 0.8 instead, although you will need to turn the wire speed down accordingly.

I'm using 0.8mm wire.

Re the dimple on top, sometimes these are impurities or gases boiling their way to the top of the weld. Do they only occur at the end of your run, where you lift the torch off the job? If so try moving the torch back over the run slightly before you lift off.

I hardly make long moves, I'm actually just doing one point after the other with the 'step back' method. I've not yet welded anythin else but 1mm sheet. Though I made some continuos weld with 2mm stuff and the problem wasn't present there at the end of the run.

When grinding back the welds I very rarely have cavities/bubbles in them, so at least that seems to be fine.

Or could be related to the fact I'm welding outside? It's hardly 100% windless outside...

Thanks for your help!

regards,
Jan

 

[keith19]

"When grinding back the welds I very rarely have cavities/bubbles in them, so at least that seems to be fine.

Or could be related to the fact I'm welding outside? It's hardly 100% windless outside..."

It's good to hear there's rarely cavities or bubbles, so maybe not too much to worry about. But a bit annoying!

One theory about these dimples is that the weld is not cooling quick enough, hence the boiling up, which could be due to a strong breeze blowing the cooling gas away. Only way to test this is to do the same job inside, somewhere out of the wind, and see what results you get.

 

[200T]

Thanks again, Keith!

I'll try that as soon as possible. But if it's not a major issue, I'm reliefed I'll report back...

Re: the brown residues; I turned up the gas a bit which made things better, I get way less of that stuff now. So that was that

Thanks again!

Regards,
Jan