Mill Scale

[Tim]

Whats this thing called Mill Scale? I went out back to the scrape heap to get some metal to run lapping beads and the instructor told me that I should take the metal to the grinding room to get the mill scale off. He said you can weld with it on there but it can mess the weld up.
Thanks
Tim

[Jerry]

What I usually call scale is found on all hot rolled metal, angle iron and on pipe, in fact some pipe will come with a varnish look and this has to come off. Angle iron I do not grind it away for it is not as thick as say hot rolled flat stock will be, which for better penetration and a more cosmetic weld I will usually grind away.

J P Streets Welding

[mikeb]

mill scale

If you're welding on steel that only has millscale then you're lucky. At my job, time is money and we do no prep on rust or scale. I notice major defects in welds from paint and oils, but rust and scale seem to flux off well with a normal bead. I MIG millscaled plates at high speed with no problem. Millscale is iron oxide and should not be viewed as a threat or impurity in my opine.

[Guest]

Mill scale...Mill rust

The following taken from Ed Craig's website...a very impressive welding engineer...not my opinion, however.

Weld Question: Which should be the greater concern rust or mill scale.
Answer: Mill scale causes much more weld issues than m rust. Mill scale can effect [1] the weld fusion potential, [2] the weld travel rates attained, [3] the weld appearance, [4] the weld mode and arc stability and [5] weld spatter formation.

When I want to do a good looking job, I take it off...when I'm in a hurry...I don't.

[mikeb]

skill conquers all

I work with all sorts of Latinos (Mexicans, Central Americans, South Americans) and some of them are superb welders, producing textbook perfect welds on any material in any position using few tools and preparation. I really believe welding is a skill much more than a science.