Welding red iron steel

[Codyboy]

I have some left over red iron material from the shop build.
The guys that welded up the steel were using a big truck mounted arc welder.
They did not grind off the red oxide or whatever that is on the steel. Just cut it to size and weld it up.

Can I weld this stuff with a mig welder using flux core wire and not have to clean off the red oxide?
I only have flox core wire and im not set up with gas .

 

[MJD1]

Yes

 

[The Cobbler]

yes, you can... but you probably will get better welds if you grind it off

 

[LXCam]

As MJ said normally yes. But if you start to have porosity issues then I’d clean it up. No matter what, get good clean metal for your ground.

 

[MoonRise]

There are few absolutes in life, besides death and taxes.

But another one is that you ALWAYS get a better weld when you are welding clean, bright, shiny metal.

Sometimes you can get away with some small amount of 'crud' and still get an OK weld. Crud is a technical term for anything that is NOT clean bright shiny metal.

Some kinds of crud include dirt, oil, grease, paint, primer, marker, black oxide, mill scale, red oxide, rust, anodizing, blood, water, squirrels, etc. This list is not all inclusive, as there are many more types of crud.

A big engine drive welder using stick electrodes (aka SMAW) is one of the processes that can sometimes tolerate the most amount of crud. Sometimes.

But you ALWAYS get a better weld with no crud in the way. Can't weld non-metal.

Even though fux core welding is kind of like a stick welding electrode turned inside out, it's not exactly the same.

Kind of like a Yugo and a Koenigsegg are both cars, they are not exactly the same thing. Lol

More importantly though, is the question of how THICK is this red iron and what welder do you have.

1/2" thick steel and a 120v 140A max wire feed welder running 0.035" Lincoln NR211MP wire? Hard NOPE, no matter how much you clean the metal. You would be exceeding the wire's workpiece thickness limit and you don't have enough amps to weld 1/2" thick steel.

Clean the metal and use enough amps from a big enough machine and an appropriate electrode and process for the task.

 

[LopezBart]

If you must weld steel through rust, mill scale, paint, etc. my experience is that 6011 rod works better than anything else I've tried. Regular MIG (75/25 Ar/CO2) welding really doesn't like anything but clean metal; I've never used flux core.

 

[Rusted Nut]

I just retired from commercial construction, no welding inspector would pass structural welds if paint was not removed.

 

[strutaeng]

Good points from previous posts...

I'm assuming OP is welding some gadgetry for his shop, picture frames, or the like...NOT x-ray, UT inspected critical welds, etc., otherwise he wouldn't be asking the question...probably doesn't have or know SMAW, or welding procedures specificatioms, (or even cares about them...)

So...Maybe we should get some clarification...? @Codyboy

 

[NUTTSGT]

I was always taught that stick is more forgiving than MIG when it comes to dirt, rust, paint and such.

 

[dr_clyde]

I was always taught that stick is more forgiving than MIG when it comes to dirt, rust, paint and such.

Fluxed processes can float out some contaminants in the slag, but it's much much better to weld on clean metal.

Any code work will require the metal to be cleaned free of oils, dirt, paint, scale or other contaminants before welding.

Sometimes in the field for repairs or non critical features guys will weld over scale or paint, but it's really never a good idea.

Stick welding being a fluxed process will tolerate a bit of scale or paint, but if you cut the weld cross section you will see anything the slag couldn't float out as porosity bubbles. Will it hold? Probably. Is it right? No.

 

[Codyboy]

Good points from previous posts...

I'm assuming OP is welding some gadgetry for his shop, picture frames, or the like...NOT x-ray, UT inspected critical welds, etc., otherwise he wouldn't be asking the question...probably doesn't have or know SMAW, or welding procedures specificatioms, (or even cares about them...)

So...Maybe we should get some clarification...? @Codyboy

I'm welding up a workbench with some scrap material from my shop build.
So yeah, nothing critical.
I'm using a 120v Hobart 140.
It seems to be doing a decent job so far.

 

[Codyboy]

Making progress!
It will be 3x5 overall including a 2" overhang lip.
Planning either 3/8" or 1/2" steel top.

 

[Jacko264]

I would say for a few minute with a sander / grinder you will get better results
also clean where the earth return lead is going to be clipped on

 

[Codyboy]

I would say for a few minute with a sander / grinder you will get better results
also clean where the earth return lead is going to be clipped on

Yes, I did grind to bare metal where I put the ground clamp.
Ive made that mistake before. WTH is wrong with this POS welder? !!
Ahh. Oh uh nevermind. Lol
Or even worse forgetting to put the ground on at all and spewing out a foot of wire.

I have the legs and top of frame tacked up. I'll clean off the slag and gunk and run some longer beads . Well for me its just a lot of smaller tacks.
I have some bed angle that im going to weld in for a shelf and support. Although its pretty rigid already and sits flat.

Some of my cuts on the purlin material wasn't great as im having to use an angle grinder.
Not as bad as I thought though. Out of curiosity I broke out the feeler gauge and the largest gap was only .020 .

 

[MoonRise]

About 1/8" thick material?

A 140 amp class wire feed welder running. 035" FCAW wire can usually do that ok.

Btw, what specific wire are you running? Brand and wire 'model' and wire size/diameter?

But you WILL get better weld results if you clean the rust and crud off first. Where the weld will go and about a 1/2" back from the joint (for a little fudge factor).

A couple of minutes with an angle grinder helps with getting better welds.

And a wipe or spray with some cleaner/solvent to get rid of grease/oil/grime type crud.

I usually try the solvent-abrasives-solvent procedure before welding.

And as you mentioned, the work clamp (aka 'ground' clamp) has to have clean metal to contact in order for the 'juice' to flow. Lol

Clean, bright, shiny metal ALWAYS gives better welds.

 

[LopezBart]

Having done this sort of thing before, you may want to remove the rust before putting the frame together if you're going to paint this. It's less work to remove the rust, etc. when you can easily flip the pieces, as opposed to flipping the entire frame and clambering over it.

 

[Jacko264]

Good info above about cleaning and grinding
you are doing a great job so far keep it up
G

 

[Wrench97]

Yea those pieces need to be cleaned up, the welding will go faster too with clean metal.

 

[NUTTSGT]

Fluxed processes can float out some contaminants in the slag, but it's much much better to weld on clean metal.

Any code work will require the metal to be cleaned free of oils, dirt, paint, scale or other contaminants before welding.

Sometimes in the field for repairs or non critical features guys will weld over scale or paint, but it's really never a good idea.

Stick welding being a fluxed process will tolerate a bit of scale or paint, but if you cut the weld cross section you will see anything the slag couldn't float out as porosity bubbles. Will it hold? Probably. Is it right? No.

I won't disagree whatsoever Clyde.

I see more "junk" welded together than nice stuff inside an actual shop. . . every farmer here had a Lincoln Tombstone at one time.

 

[Codyboy]

About 1/8" thick material?

A 140 amp class wire feed welder running. 035" FCAW wire can usually do that ok.

Btw, what specific wire are you running? Brand and wire 'model' and wire size/diameter?

But you WILL get better weld results if you clean the rust and crud off first. Where the weld will go and about a 1/2" back from the joint (for a little fudge factor).

A couple of minutes with an angle grinder helps with getting better welds.

And a wipe or spray with some cleaner/solvent to get rid of grease/oil/grime type crud.

I usually try the solvent-abrasives-solvent procedure before welding.

And as you mentioned, the work clamp (aka 'ground' clamp) has to have clean metal to contact in order for the 'juice' to flow. Lol

Clean, bright, shiny metal ALWAYS gives better welds.

I think the wire I'm using is

Hobart 0.035 in. E71T-11 Flux-Core Welding Wire, 2 lb. Spool, 325-850 Deg. F Operating Range​

from TSC.

Yeah I probably should have ground off the gunk but I'm lazy. Even more lazy working on the floor.

 

[Codyboy]

Having done this sort of thing before, you may want to remove the rust before putting the frame together if you're going to paint this. It's less work to remove the rust, etc. when you can easily flip the pieces, as opposed to flipping the entire frame and clambering over it.

I plan to get a knotted wire brush for the grinder and clean it up before painting.

 

[Codyboy]

I'm still undecided on the top.
I think 1/2" steel plate will make it too heavy if I ever have to move it.
Probably go with 1/4" , possibly 3/8".
I want it to be pretty heavy duty to beat on though.

 

[Beerhippie]

Get some of these:



(3M Cubitron II, 36 grit) and the backing plate to go with them. That rust will be gone so fast your head will spin.

Do the grinding outside and wear a dust mask.

I agree whole-heartedly with everything said above about the advantages of clean metal. Many years ago, I had a boss who insisted that I didn't need to clean red-primed steel for MIG welding--until I showed him the difference. A few minutes is time well invested.

 

[Codyboy]

Get some of these:



(3M Cubitron II, 36 grit) and the backing plate to go with them. That rust will be gone so fast your head will spin.

Do the grinding outside and wear a dust mask.

I agree whole-heartedly with everything said above about the advantages of clean metal. Many years ago, I had a boss who insisted that I didn't need to clean red-primed steel for MIG welding--until I showed him the difference. A few minutes is time well invested.

I ended up getting something similar i think.
An abrasive disk about 3/4" thick. Seems to do a good job at removing the rust and dirt. Which is good overall for painting as it still leaves the red primer in place(mostly).
I also bout a knotted wire wheel just to remove the rust and gunk from the larger flat surfaces.
Not sure which i like better. The wire seems less aggressive and leaves more of the primer which is good. It also is a bit more flexible then the abrasive disc. Ill continue with both to see which one seems to do a better and faster job.
I do have some flapper disc's that work better at getting to bare metal though, and will probably use that before welding.

I also picked up a Bauer angle grinder for 35 bucks.
I have 2 porter cable grinders about 15 years old that have held up well but starting to get a little chatter when using a cutoff wheel and very torquey when you pull the trigger.

 

[Beerhippie]

I ended up getting something similar i think.
An abrasive disk about 3/4" thick.

Nope. What I posted is a fiber disk, like heavy sandpaper, used with a backer plate. Try one, you'll be blown away. Nothing removes mill scale like it.

And the Cubitron II disk is the best I've ever used--by far.

 

[BigMike782]

Nope. What I posted is a fiber disk, like heavy sandpaper, used with a backer plate. Try one, you'll be blown away. Nothing removes mill scale like it.

And the Cubitron II disk is the best I've ever used--by far.

No truer words have ever been spoken. I have used Cubitron paper on wood and grinding wheels on steel and 3M has hit a home run.

 

[Beerhippie]

No truer words have ever been spoken. I have used Cubitron paper on wood and grinding wheels on steel and 3M has hit a home run.

Yep. I have Cubitron II Xtract disks for our RA sanders for wood. It's all I buy anymore. I need to get a few belts for the belt sander.

 

[Codyboy]

Nope. What I posted is a fiber disk, like heavy sandpaper, used with a backer plate. Try one, you'll be blown away. Nothing removes mill scale like it.

And the Cubitron II disk is the best I've ever used--by far.

Yep. I have Cubitron II Xtract disks for our RA sanders for wood. It's all I buy anymore. I need to get a few belts for the belt sander.

No truer words have ever been spoken. I have used Cubitron paper on wood and grinding wheels on steel and 3M has hit a home run.

I'll have to try them.