Any tips for a surefire way to MIG (FCAW) thin metal welding ?

grumpy.i.m · Dec 5, 2020

A question from hobbyst, so please be lenient.

I am trying to learn how to MIG weld. Actually
FCAW, as I am using flex core wire and do not
have gas connected. I've been watching Youtube
videos, and that helped quite a lot, but still
can't nail the settings / technique to not blow
holes in thin metal.

Decreasing power only works to some point below
which can't make a clean weld.

I already worked out settings for 1.2 mm thick
metal sheet that give acceptable results most
of the time, but still manage to blow through
and have a hard time fixing it. Btw, any easy
way to fix a hole in but weld ?

What is safest torch angle to start to avoid
burning the hole through ?

I am using 0.8mm flux core wire on MIG 350
amp welder which can only adjust voltage and
wire speed.

Any helpful answers will be appreciated.

Steven-Canada · Dec 5, 2020

Start watching the welding tips and tricks youtube channel

Backing bar, chill bar,

A bar of metal clamped onto the weld back.

Copper, brass, aluminum, will absorb extra heat, form the weld puddle, won't stick to the weld.

Flash Tacks & Chill Bars on 18 Gauge Steel | Welding Tips & Tricks #Welding #TIG #WeldingTechniques - YouTube

and fix your country

mjr6550 · Dec 5, 2020

I'm not an expert with mig, but I do have quite a bit of experience on thicker steel. 1.2 mm is about the thickness of automobile sheet metal. That is typically welded by spot welding with mig about 1 inch (25mm) on center. Then spot weld half way between spots and continue until you have touching spots.
Welding continuous will typically burn through or be too cold.
If you are just learning mig I would work with steel about 3 to 6 mm thick until you get some experience.

DDoug · Dec 5, 2020

Hook up the gas fitting, use 100% CO2.
.023 solid wire.

Newman109 · Dec 5, 2020

digger doug said:
Hook up the gas fitting, use 100% CO2.
.023 solid wire.

Good way to go. I have a Miller 252. I run 100% CO2 with an occasional dab of weld gel. It gives nice welds and it's relatively inexpensive - about half the price of Argon-CO2.

I also agree with the spot-welding technique for thin sheet metal. It's often done that way initially in body shops when replacing floors and filling in panels. Once the weld area is filled in they grind to finish up.

metalmagpie · Dec 5, 2020

You do have your polarity correct, right? Fluxcore requires the reverse of hardwire MIG. MIG -> DCEP and FCAW -> DCEN.

1.2mm sheet steel is equivalent to 18 gauge which is what nearly all 55 gallon steel drums are made of. I've done a fair amount of welding on those drums. Like all thin metal, you are damn careful to hold your arc length and travel very consistent. I generally weld something like 1/2" (12.7mm) at a time, then move ahead and weld somewhere else, then come back and weld some more. This is called backstepping.

If you could move to hardwire MIG with gas, you could move down to .023" wire (0.58mm) which would let you turn down the current more.

Make sure your parts are clean, on thin stuff you can't be burning through paint or anything.

metalmagpie

idacal · Dec 5, 2020

Here is a thread on attwmpting to do it with flux core Flux core ok for auto patch panels? -

Weld Talk Message Boards .if you have a 350 amppower sorce getting set up is cheap. Ihave an LN 25 set up with 23 wire for that thin stuff and still burn through if not carefull. Also talk to your welding supply about what your trying to do the standard flux core most places sell is designed for welding thicker product withless amps for starter machines, ther may be some low penatrating wire available but will need to be orderd in. At 5 bucks a pound

Strostkovy · Dec 7, 2020

I have a squirt welder that runs on 115V that I use for repairs.

Thin metal is easier to weld if you are welding it to something thicker, because then you can keep the heat and puddle mostly on the thicker stuff.

For thin to thin you just have to move fast and steady.

BT Fabrication · Dec 7, 2020

flux core inputs more heat into the weld pool then solid wire does.

id suggest 0.030" wire and 75/25 gas. then its just multiple spot welds just hot enough to melt it in and not too hot that you have a hole.

in my opinion, tig is better for anything like that under 18Ga or about 1.2MM thick. mig always blows holes without any heat sink

cyanidekid · Dec 7, 2020

BT Fabrication said:
flux core inputs more heat into the weld pool then solid wire does.

id suggest 0.030" wire and 75/25 gas. then its just multiple spot welds just hot enough to melt it in and not too hot that you have a hole.

in my opinion, tig is better for anything like that under 18Ga or about 1.2MM thick. mig always blows holes without any heat sink

yeh, but... the OP doesn't have a GTAW welder...

. I second to go to .023 solid wire and 75/25, or 90/10 IF you can.the higher argon mix has a little less penetration.

one thing that hasn't been mentioned, any (ANY!) rust or paint will really make things harder.

the backing up of the weld with a copper heatsink will really help, as will the "spot" or intermittent technique.

use a clean torch liner, the right drive rolls,(textured grooves for fluxcore), clean tips, a good ground, all that stuff helps too.

Arclight · Dec 7, 2020

Also, nothing beats an Acetylene torch and a #00 or #0 tip for filling holes. You heat the edges to cherry red, then start dipping the filler rod and it magically skins over from surface tension as you play the torch across it. Bigger gaps can be bridged with pieces of filler rod until the gaps are small enough to skin it over.

Scottl · Dec 7, 2020

Copper backer behind weld.

it doesn't have to be very thick or very large. I buy small sheets of 0.050" from McMaster and use about a 2" x 6" piece. In the past I've even used pieces of copper water pipe hammered flat when welding on automotive panels.

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Any tips for a surefire way to MIG (FCAW) thin metal welding ?

grumpy.i.m

Plastic

Steven-Canada

Hot Rolled

mjr6550

Aluminum

DDoug

Diamond

Newman109

Diamond

metalmagpie

Titanium

idacal

Hot Rolled

Strostkovy

Titanium

BT Fabrication

Titanium

cyanidekid

Titanium

Arclight

Aluminum

Scottl

Diamond

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