mig welding 3x2 box section

[God mode restorations]

evening all...
today i thought i would take a break from the stick..and put down a few mig welds..now i set my machine up on 3mm plate..same wall thickness as the box i am welding...the plate i had set on power number 3 with 3.2 wire speed..but it did not like it on the box..so i adjusted settings to power number 4 with 2.9 wire speed..it flows nice at this setting with good penetration but has under cut..so do i drop down on ampage and up on the wire speed..or just tweek the wire speed..these are just a couple of quick beads i did this evening..but when done properly they must be strength critical.....

 

[Bill Edwards]

I'd try upping the wire speed and see what that does.

 

[God mode restorations]

so drop down on ampage and up the wire speed......

 

[backpurge]

If you drop the wire feed speed you are reducing the amps, it's the wire feed that controls your amperage

 

[God mode restorations]

Hi...
so i should really keep the power setting i am on and reduce wire speed to eliminate the under cut without reducing penetration...

 

[Paul G]

It looks to me in the second pic down that your putting down about an 8mm fillet on 3mm wall box.

Depositing that much molten metal in one run you will always be hovering on the brink of undercut,
unless you weld in the gravity down hand position that is.

I must admit I'm puzzled why it's not fully welded, i.e. missed welding the corners.



A note on settings.

There's a direct relationship between the VOLTAGE setting and the WIRE SPEED.
The balance between these two gives us the setting, often referred to as the frying bacon sound.
When we need more (or less) heat to weld thicker (or thinner) material, or perhaps just need bigger (or smaller)
welds then we adjust both voltage & wire speed to move on to the next (frying bacon) setting.

"Power" isn't a normal welding term. It's the welder input from the socket on the wall, via transformers and
power lines from a power station. (As Al Murry would say, "the clue's in the name")

Cheers,
Paul G

 

[God mode restorations]

thank for the reply Paul..
i did not tack/weld the corners as these were just a couple of pieces of scrap i had kicking about and just mainly concentrating of perfecting my gun angle and setting up machine..i get the bacon frying sound...its 15 years since picking up the mig gun...perfection to me is everything..i ask a lot of questions but i do totally appreciate all of the input i get on hear...
thanks.....spencer

 

[Jan]

As implied; the lack of welding at the corners will see these stitches giving way under any decent level of stress as the corners are where the stresses are concentrated. The usual advice - once you've got your amperage/wire feed going nicely - is to start at the middle of one side and continue around the corner until you reach the middle of the next side. Then you can adjust your position to repeat until you've gone all the way around the box. Any lack of fusion with the previous weld(s) will now be in much lower stress areas and the joint should hold longer than the parent metal in similar conditions.

 

[God mode restorations]

ok cool..i have some more box section so i shall have this afternoon to hopefully get some decent seams going..thanks....

 

[God mode restorations]

just out of interest..is there a prefered method of testing penetration on a fully welded piece of box section..

 

[Steve Gray]

As implied; the lack of welding at the corners will see these stitches giving way under any decent level of stress as the corners are where the stresses are concentrated. The usual advice - once you've got your amperage/wire feed going nicely - is to start at the middle of one side and continue around the corner until you reach the middle of the next side. Then you can adjust your position to repeat until you've gone all the way around the box. Any lack of fusion with the previous weld(s) will now be in much lower stress areas and the joint should hold longer than the parent metal in similar conditions.

didnt know that!, thanks!
I learn something everytime I visit this forum

 

[Paul G]

just out of interest..is there a prefered method of testing penetration on a fully welded piece of box section..

Google " macro etch testing "

Strangely enough when I just tried it I ended up back on this site.
All this going round in circles is making me dizzy.

Paul G

 

[brokenbiker]

i posted a link to jody colliers latest video about home macro etching, that's probably where you ended up. its a good vid and also covers the penetration of uphill and down hill too but that's not relevant here

 

[Paul G]

Wasn't a vid.

It was
www.mig-welding.co.uk/wiki/Macro_etch

 

[brokenbiker]

ah not mine then

 

[brokenbiker]

this was my post with the vid

http://www.mig-welding.co.uk/forum/threads/macro-etching-at-home.47777/#post-533377

 

[Jan]

Testing a pair of fully seam welded box sections requires that they are cut through to expose the weld in cross section. Then you clean up the exposed surfaces with a file followed by finer and finer 'polishing' until the surface is smooth as a baby's bum. After etching with acid - how long depends on the strength of the acid - a final rinse, dry and polish should reveal the grain structure quite plainly with a simple handheld magnifying glass or 'jeweller's loupe' (I have both).
If the welds are very poor you won't have to go that far as any voids or inclusions will show up as soon as you've cut through the joints.

 

[God mode restorations]

afternoon everyone..after a drag race fueled weekend i am finally back with the mig gun..didn't get off to a good start as had the hump...but relaxed and managed to do some half sensible looking beads..and i have not got the nack to weld round corners yet ...
but will.....see pics...all critisizms & comments greatfully taken on board...



let me know what you think...

 

[God mode restorations]

excuse the corners.....outside edge..there is a percific name for this but cant remember .....and vertical down.......