[Sethmark]

Working on welding up a number of quarter inch DOM to solid stock stems. Currently running between 225 and 250amps, 1/8" tungsten, gas lens and #8 cup. Around 15cfh argon.

I'm running a root pass with 3/32 er70s-2, then a 5/32 s-2 rod cap.

Any suggestions on better settings or processes?

[Sandow]

If you are running flat out at those amp settings you are probably too hot unless you are really trucking. Beyond that, post a pic and we'll tell you what if anything seems off.

-Sandow

[Poland308]

If you bump down to 1/8 or 3/32 and run 130-150 you should be fine. You can make the 5/32 work aven at these amp ranges. Just don't try to single pass it.

[Diesel]

250 amps!... On 1/4"??! I would say cut it in half. Most of my roots at zero land 1/8 gap are 100-110 and most fills are 130-150 on 3/8 to 3/4 plate. Pipe runs the same. I'm not sure what you're doing to need it that hot but from words only, ID say it's too hot.

[MinnesotaDave]

You're question leaves a lot out. Couple pics would be handy.

Amps seems fine I guess - as long as you can keep up.

I run 180-190 amps on 3/16 plate fillet welds and lately have been making short runs at 230+ amps so I can pick up speed.
(Puddle starts immediately and welds quickly)

[Sethmark]

I should elaborate. I'm sorry for the lack of detail, I've had a head cold and I'm just a little spacey. The machine is set to 225. I use a footpedal and I'm not it wide open. So my assumption is I'm probably in the 175-ish amp range. Welds are typically fairly shiny when I'm done... Not grey from over cooking. Once in a while I notice the puddle gets a little plasticky. I'm assuming at that point I'm cold?

I haven't welded that much 1/4 via tig. Getting the heat and flow right is important to me.

This isn't a picture of the job I referenced. Just a representation of the heat on material thickness.

image.jpeg (40.98 KiB) Viewed 1054 times

[Diesel]

Knowing that you are using a foot pedal and the material makes me think you are less crazy. As long as the puddle flows and you don't have to wait for it to catch up. I also usually weave which takes less amps. Setup seems fine for what youre doing. I might run 20cfh but if you're in a controlled shop with clean consumables it should work.

[Sethmark]

It works. What I'm concerned about is making sure I'm using best practices. Best combo of consumables and settings.

[Sandow]

It works. What I'm concerned about is making sure I'm using best practices. Best combo of consumables and settings.

So this will probably generate some dissenting opinions but my understanding of the metallurgy is that in mild steel, slow progression ends up with a stronger weld. High heat input from slow progression ends up with a larger visible HAZ but the transition of the melt pool to solid is slower and thus less brittle. Since that is usually the weakest point of a weld, allowing for a slower transition would seem to be best practice. For non-mechanical joints like pipe, progression rate probably doesn't matter as long as your not leaving porosity or cavities. For junctions that will see high load, it might make enough of a difference to matter.

-Sandow

[Oscar]

It works. What I'm concerned about is making sure I'm using best practices. Best combo of consumables and settings.

So this will probably generate some dissenting opinions but my understanding of the metallurgy is that in mild steel, slow progression ends up with a stronger weld. High heat input from slow progression ends up with a larger visible HAZ but the transition of the melt pool to solid is slower and thus less brittle. Since that is usually the weakest point of a weld, allowing for a slower transition would seem to be best practice. For non-mechanical joints like pipe, progression rate probably doesn't matter as long as your not leaving porosity or cavities. For junctions that will see high load, it might make enough of a difference to matter.

-Sandow

My question is, since when does mild steel have enough carbon such that the cooling rate would [presumably] cause martensite formation and the accompanying brittleness upon air-cooling?

[Sandow]

Well, first I'd say it doesn't take much to form martensite. since this is only .35% carbon:

.35% C rapid quench

Steel_035_water_quenched.png (396.03 KiB) Viewed 909 times

But beyond that, anything with a tendency to form a crystalline structure will form small crystals if the transition is fast and large crystals if transitioned slowly. Since the only things that don't form crystalline matrices are amorphous solids like glass, I'd wager even chemically pure iron would form a fine crystalline transition at a weld junction.

Google "Super Quench" and you will find that even the knife making guys will admit that it will harden mild steel even if they can't adequately explain why.

-Sandow

[Sethmark]

What is my take away from the science?

[MinnesotaDave]

It works. What I'm concerned about is making sure I'm using best practices. Best combo of consumables and settings.

You can drop down to a 3/32" tungsten if you like - 1/8" tungsten isn't required at the amps you're using on DC.

I've currently got a #7 cup on mine but some people go smaller on fillet welds.
#6 cup seems to work well for me too but I like a decent length stickout so I can see better - so larger is good for me

[exnailpounder]

What is my take away from the science?

LOL nothing that matters in any world other than industrial. You have to understand...this forum attracts the cream of the crop and they want nothing more than to help you excel at your craft. Us lowly repairmen are constantly amazed by guys that don't have to powerwash grass and dogshit off of a mower deck so we can fix all the rust Nothing smells better than 1300 degree dogshit...ask me how I know.

[MinnesotaDave]

What is my take away from the science?

LOL nothing that matters in any world other than industrial. You have to understand...this forum attracts the cream of the crop and they want nothing more than to help you excel at your craft. Us lowly repairmen are constantly amazed by guys that don't have to powerwash grass and dogshit off of a mower deck so we can fix all the rust Nothing smells better than 1300 degree dogshit...ask me how I know.

Hahaha! On point

[Sethmark]

What is my take away from the science?

LOL nothing that matters in any world other than industrial. You have to understand...this forum attracts the cream of the crop and they want nothing more than to help you excel at your craft. Us lowly repairmen are constantly amazed by guys that don't have to powerwash grass and dogshit off of a mower deck so we can fix all the rust Nothing smells better than 1300 degree dogshit...ask me how I know.

I'm here to excel at my craft. I'm functional and knowledgeable for a field level guy. But I would love to understand the what's and the whys better. I've done a number of semesters of welding at a college level, but that rarely gets you more than a text book and a lot of hands on welding coupons.

[Sandow]

Nothing smells better than 1300 degree dogshit...ask me how I know.

LMAO...

What is my take away from the science?

Yeah, this stuff is a marginal concern for most applications. Your weld looked good and while most people would run colder, as long as you aren't leaving cavities at the corner, you'll still have a stronger outcome then MIG. If you are doing critical applications where a few percent yield strength really makes a difference then I'd say slower is better. You have way more time spent in clean up and fitting than you will have in welding no matter what.

-Sandow

[Sethmark]

Ain't that the truth. Between spinning the barrel on the lathe and grinding to shiny metal prep is king.

[Poland308]

I have two kinds of welding. One where I prep and measure and level. The other where I don't pick up a grinder, I level by eye and if it melts it can be welded.