[Chips O'Toole]

I was tired of practicing on angle iron with heavy black scale that had to be ground off, and I didn't get out of the house early enough to get to a real metal supplier, so I went to Home Depot and bought a bar of plain steel 2" wide and 1/8" deep. I didn't look too closely at it, but because it looked so much nicer than the angle iron, I figured it was cold-rolled. Am I living in a fool's paradise?

I hit part of it with a 60-grit flap disk, and it looks clean, but it's not what I would call "bright."

[Farmwelding]

As the metal black or a dulling grey when you got it?

[Chips O'Toole]

It's light grey but it doesn't seem to yield too well to a Steel Demon flap disk. The disk cleaned it up, but it doesn't have that super-shiny bare metal look. I guess it's hot-rolled, and I am in for a lot of grinding.

[Farmwelding]

The layer of mill scale isn't that thick on hot rolled, but put some pics to look at so we can see better

[LtBadd]

It's been awhile since I've looked at the box store metal rack, but if the surface is smooth it's probably cold roll. If they provide the material type on the sticker, 1018 is CR and A36 is HR.

HERE is a good short write up (with pics ) on the difference between HR and CR, google if you're hungry for more.

Welding is more then just establishing an arc, your frustration between HR and CR and why you dislike HR can be a stepping stone to in depth knowledge you'll be able to flood others with one day, ok starting to get a little deep here, I gotta go.

[Chips O'Toole]

Whatever it is, it turned out I didn't have to grind the surface perfectly shiny in order to practice. I decided to experiment, since I have to learn what works and what doesn't. I ground it down to where it looked clean, and I tried to weld. I figured if it didn't work, it would tell me Home Depot metal has to be ground more, and that would be useful. If not, I saved some unnecessary work. The beads came out okay, without obvious porosity or anything.

I got cocky and tried a short fillet weld. It went pretty well for a short distance, but then I had trouble getting the right balance between heating the upright part and the flat part, and things went south. I should have tried a lap weld instead, but I guess it's all useful.

This week I'm going to the metal place and get metal that comes with a name.

[exnailpounder]

I grabbed some aluminum strip from Lowes in a pinch once. There is no designation as to what alloy it is but it was soft as warm taffy but it welded ok...probably pure....at precious metal prices. Can't go wrong at a good metal supplier. At least you're not getting mystery metal.

[Oscar]

Just keep in mind, mild or worn flap disks can create the illusion of "grinding off" millscale, when in reality all they do is polish it. You need a very aggressive grit (<80) to make it worthwhile. Otherwise you end up with either polished millscale, or having to push the grinder really hard into the metal, wearing out the motor un-necessarily. I highly recommend either a coarse grit sanding pad with a backing pad (3M cubitron II work awesome), or a regular ol' black hard grinding disk.

[mpete53]

I find when grinding off mill scale, the sparks tell the story. When I start on the scale there are very few sparks coming of the grinding/sanding disk. After a bit, sparks become more numerous. When all the scale is off, any place I touch the grinder I get a continuous stream of sparks.

Mark

[Chips O'Toole]

I feel like I should go ahead and practice on aluminum. Easy to cut, easy to prep, and no scale. Even if it's harder to weld, I would get an extra 40 minutes of welding time per session.

[Farmwelding]

I feel like I should go ahead and practice on aluminum. Easy to cut, easy to prep, and no scale. Even if it's harder to weld, I would get an extra 40 minutes of welding time per session.

There is a point in a beginners tig welding adventures when you should start aluminum. You probably would benefit now. Helps you feed rod better on steel and reading the puddle and foot controlling.