Millscale

[Raul]

So what are other differences between HRS and CRS?

Hot roll is rolled out red hot. It's often got carbides and carbon and inclusions in it from the rolling. This is why machine operations on hot roll are often remarked upon with negative sentiment. There are tough spots hard spots and other things that make machining an unpleasant experience. It is also almost never square. IT moves around rather a hot under the force of rolling out. So the dramatic trapezoid is the norm not the exception.

Hot Roll has more carbon than cold roll and it is not standardized, so black-smithing the stuff can be tedious.

Hot roll can come scale free if it was acid pickled and oiled to prevent rust the finishing process is often abbreviated as P&O.
In that state it is hard to distinguish from coll roll

Cold roll is rolled out cold, it is buttery to machine, but it also gets a skin on the outsides that can cause all manner of problems when that skin is machined away. The stress on one side with the skin versus that where it was removed can cause a part to turn bananna shaped.

So if you are going to machine the skin off your stock hot roll may be the better choice. If you are just going to drill it full of holes cold roll might be better, but cold roll is more expensive because the process is more energy intensive.

[MagicHat]

Excuse me Stick-man, do you feel that "Tiger Paw is the best disk? Thanks, MagicHat.

[Stick-man]

Excuse me Stick-man, do you feel that "Tiger Paw is the best disk? Thanks, MagicHat.

I can't compare it to anything but horrible frieght. I really just started using them for this, because I didn't realize how fast they actually remove material.

[MagicHat]

Thank you! I was surprised to hear about the material removal too. MagicHat

[Br@ndoM@n]

What I have noticed is if the end product is gonna be outside in the elements the mill scale resists rusts. I have some bbg grates I have made and i have ground it all to shiny metal but even a small amount of humidity will have alot of surface rust within hours. if I just grid down the parts needed welded and leave mill scale on the rest it doesnt rust if left out a week or so.

If I grind everything shiny then use it the same day over a fire the black coating will also protect it from rust a bit to unlesss its raining decent and it washs off.

[padronanniversary]

Do you also get more spatter with mill scale on ?

[Br@ndoM@n]

I havent noticed a difference in spatter but I use flux core at home so theres a bit of spatter anyways. The mill scale around the area being welded peels off from the heat.

[Dr.Weld]

Surfaces on which weld metal is to be deposited shall
be smooth, uniform, and free from fins, tears, cracks, and
other discontinuities which would adversely affect the
quality or strength of the weld. Surfaces to be welded,
and surfaces adjacent to a weld, shall also be free from
loose or thick scale, slag, rust, moisture, grease, and
other foreign material that would prevent proper welding
or produce objectionable fumes. Mill scale that can withstand
vigorous wire brushing, a thin rust-inhibitive coating,
or antispatter compound may remain with the
following exception: for girders in cyclically loaded
structures, all mill scale shall be removed from the surfaces
on which flange-to-web welds are to be made.
The source of this information is AWS D1.1 so I would say yes it should be removed.

[Nick_Reno]

First time posting Pics, hope it works. I got some scrap steel from a friend that has a gray coating on it. I used a 80 grit wheel and cleaned both sides, but when I ran some TIG beads on it, it smelled bad and on the back side (on my table) it left a white residue. I assume this is not good to breath? Does anyone know what it is?

[Grady_Fab._&_Forge]

I have used concrete cleaning acid to remove mill scale. It is fairly quick acting but very dangerous. I have looked for other means other than grinding and did an experiment. I took some scrap pieces of hot rolled and put them in a plastic coffee can and covered it with 5% acid white vinegar and left for about 2 days. I took steel wool and rubbed the mill scale and it had dissolved and came off easily. I bought some 2 1/2 inch pvc pipe 9ft. long and glued a cap on one end. I degreased 3 8ft. sticks of handrail cap and 2 8ft. sticks of 1 inch punched channel. I was able to put all this in the pipe and poured in the vinegar.It only took 1 and a half gallons to cover the steel by a couple of inches. I plan on pickeling the steel for 48 hours and then pour off the vinegar and wipe the steel with steel wool and see how this works. I will post the results!

[Justme]

I use vinegar as well. It works great. Usually 48 hours does it, and I can just hose the dissolved scale off. Cheap and green!

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[Justme]

It also strips rust really well.

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[Grady_Fab._&_Forge]

Pix of handrail cap pickled in venegar

[lotechman]

I toured a large manufacturing plant making backhoes and they had minimal ventilation and none localized. They used hard wire (GMAW). I asked the guy taking us around and he said the major amount of smoke is caused by oxide scale on the plate. Since all their material was cut, formed and sand blasted/wheelabraded before delivery they had no smoke problem. I seemed to have some truth to the statement because there was no smoke evident even around the robotic arm that welded on one piece for over a shift.

[richy.tig.stick]

Is Acetone safe to weld on after....like I know its ok if you get it all off but lets say u miss a spot and tig weld on it, can it affect u the fumes from the acetone?

[Robert Hall]

If you let a spark get into the trash can where you tossed the tag you might get a surprise. (Don't ask how I know)

[Willie B]

Zap, was the grinder in the picture the one that bit you? I have its little pygmy twin brother. the barrel is just big enough a gloved hand (I got stubby fingers) doesn't get a real good grip. Once it got me on the other hand with a hard disc so white knuckle bone was visible. A few days ago on start up it leaped from my hand and skittered across the floor ruining a Norton Blaze disc. I have a newer DeWalt 4.5 higher powered version with soft start. Its behavior is much better.

[RodJ]

Is Acetone safe to weld on after....like I know its ok if you get it all off but lets say u miss a spot and tig weld on it, can it affect u the fumes from the acetone?

Acetone not sure. But chlorinated compounds (some brake cleaners, TCE, etc.) can generate phosgene gas in a welding arc. One whiff can kill you and that is no joke or urban myth.

[MISSING LINK]

mill scale, oxides, surface trash, whether it be HRS CRS SST or Alum, if you are welding on it, grind it off. can't count how many times I have watched guys fight with a weld, then grind it clean and say "ohh, that is much better".. 5 minutes with a grinder is better that every day looking at a poor weld because of lazy prep.... just my $0.02

[WWOW]

Hi Fellow Sparks.. When evr I TIG on hot rolled 1" sqr tub, I get a weld puddle that looks like a has bubles just under the flwoing hot metal and when they break surface it loks like a worm pile sometimes. Very weird, tried to just boil the bubbles out and that did not work

any suggestions ?? i alsu just use 100% argon gas and 2% thoriaed


Keep Sparkin..... WWoW (Whild Welder own Wheels)

[steel]

U tell them ae

[Oscar]

Hi Fellow Sparks.. When evr I TIG on hot rolled 1" sqr tub, I get a weld puddle that looks like a has bubles just under the flwoing hot metal and when they break surface it loks like a worm pile sometimes. Very weird, tried to just boil the bubbles out and that did not work

any suggestions ?? i alsu just use 100% argon gas and 2% thoriaed


Keep Sparkin..... WWoW (Whild Welder own Wheels)

Well first of all, have you properly ground off/removed the millscale?

If you have, then you have a gas shielding issue. You cannot "run over" the wormholes with the tig torch that is carrying contaminated shielding gas, or otherwise suffering from improper gas shielding. You need to find the gas issue first----check every single fitting from the argon bottle all the way to the tig torch connector under the handle to the torch head and consumables.

[filo]

ive seen people do a vinegar bath with big pieces instead of wasting abrasives.

[Willie B]

Acetone not sure. But chlorinated compounds (some brake cleaners, TCE, etc.) can generate phosgene gas in a welding arc. One whiff can kill you and that is no joke or urban myth.

I buy non chlorinated brake cleaner. I like acetone, but using a wire brush or paper towel to wipe leaves bits of lint, so last thing is a squirt of non chlorinated brake cleaner. I've considered one of those refillable spray cans you use with compressed air, & acetone.

Willie

[quititman]

First time posting Pics, hope it works. I got some scrap steel from a friend that has a gray coating on it. I used a 80 grit wheel and cleaned both sides, but when I ran some TIG beads on it, it smelled bad and on the back side (on my table) it left a white residue. I assume this is not good to breath? Does anyone know what it is?

That coating looks like cold galvanizing or zinc that was sprayed on? Try grinding it off.