first attempt at think to thin mig welding.

[BeNos]

hey all
here is some pics of my first attempt at welding some 3mm box to a 6mm plate bench top.
i think the later ones were getting fairly good. not to sure on penetration but i could pick up the entire bench with just the benchtop so cant be to bad. the early ones were quite average though. to much heat i think as i was melting the smaller stuff.
any thoughts good or bad appreciated.
and also just a bit of clarification on reading the gauges.
now one i understand is cylinder pressure. as it goes up to like 2000 pounds per inch but the other one is lower is this the flow rate? if so i think mine is up around like 25 pds/in or something like that is that to high a gas rate as i seem to have gone thru a 4m3 bottle of gas in no time at all. like ive weled up 4 legs and a bench top and a few other small odds and ends and im pretty sure im out of gas(pressure on top of smartop bottle head is going well and truely into the red) and this stuff isnt cheap so i dont wanna be wasting it thats for sure.

 

[BeNos]

btw i was basically trying to aim the heat at the thicker plate and just wave the heat into the thinner stuff real quick and wave it back. it seems to look ok but i certainly aint a pro thats for sure.

 

[Chickenjohn]

You got a remarkably neat looking weld considering how rusty the steel is!

Clean the metal till it is shiny with a grinder/wire brush/ shot blast etc and don't leave such big gaps! 1mm at most, ideally the two pieces should be touching.

 

[dai]

in the 4th pic has the weld cracked off??


if i was welding thick to thin i try to point the arc 80/20% towards the thick

 

[pedrobedro]

At 3mm to 6mm neither section is what you call thin for mig. What amperage is your welder ? You want to be at the top end of 200 amp for that.

 

[BeNos]

its a 180amp mig. was using setting 5 of 6 with .9mm wire and the gap wasnt ideal but the steel was a bit off straight. but the metal has rounded corners so thats a bit of the gap.
and yes i should clean them up before welding but i was a bit impatient and running out of time.
and thats what i basically was doing in i aimed the heat into the thick stuff and as i said just sort of waved it into the thinner stuff. as i was very easily blowing holes itno the smaller otherwise. also on top of the bench you can see the hot spots thru the weld so id assume its pretty close to hot enough.
do most of em look like they have pretty good penetration. would you think that if im blowing holes into the thinner stuff so im definately getting good penetration into that just a little concerned about the 6mm stuff. but as i said it seems alright.
but il leave it up to the pros to decide i guess.

 

[Bsmith]

In first pic it looks like the 3mm box has corroded (on the inside of the box?) until its too thin for welding, pic 2 is also almost burning through. Notice how weld in the last pic is much better when using better quality box.
I think you could have your work gas press way down to around 8psi, I have added a flowmeter to the exit of my regulator and have it set to around 10 - 12lpm but you could set the gas flow roughly by listening for a dullish hiss at the torch when the trigger is pressed.

 

[BeNos]

yeah its second hand tube so its a bit up and down. and yeah the later welds look alot better and seem like they have better penetration.
and yeah when i pull the trigger i get a more gushing sound out of the torch. so il wind that down a heap.