Make metal shiny before welding it.

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donsrods

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May 11, 2007
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10,476
Location
fort myers florida
One thing that drives me nuts is, I see guys (not only on here, but on other forums) welding parts that are either rusty or still have mill scale (that black coating that comes on new steel) still on it. I can't stress enough how clean you should make the parts before attempting to weld it.

We grind it and sometimes even sandblast it first, to a very shiny appearance, then keep our hands off of the parts without gloves until we are done welding it together. You can't get a good, strong weld unless you spend some time getting the parts prepped properly. We find we spend a lot more time cleaning the parts and getting them clamped properly than we spend on the actual welding.

If you do this you will have stronger welds that also look better.:)

Don
 
Sand blasting before welding is not that good of an idea. Sand is dirt and it embeds in the steel. So you are back to welding on dirt. You could sandblast then grind. You are right in that it has to be clean. Aluminum is even more more particular to be clean. You don't even grind aluminum as the little bit of grinding wheel will contaminate the weld. We use Scotch Brite pads to clean aluminum with, right before it is welded, and yes do not touch where you are going to weld.
 
Good advice but if I had ground all the rust off my Willys before welding anything.........then I'd have a huge pile of ground rust and I'd be looking for a project right now :eek:

I see where you're coming from though and I'll try to do better :)[;)
 
SF, I really had no one in particular in mind when I posted that, just something I see all the time everywhere. :)

Ron, yep, I forgot to clarify that about sandblasting. Sometimes some steel has tougher mill scale than others so I will toss it in the cabinet first to get that off, then grind it shiny after that step. The stuff we welded up last night had mill scale that came off easily with the grinder, so that is all we did.

We used to use brake cleaner to wipe any contaminates off before welding but read so much about the fumes causing neurological problems over time that we quit. I'm goofy enough without any outside influences. :eek::D

Don
 
We forget to mention these simple things, we do automatically, when helping others and I'm glad you posted this [cl :D

Jim
 
Don, there really is a big difference in the mill scale in these sheets of steel. We just bought a Burr King tumbler to deburr and polish the parts we make. Some of the parts will clean up in about 30 minutes while others take 2-3 hours of tumbling to get all of the mill scale off. The next load of sheet will be pickled and oiled, so we just have to deburr, and not clean so much.
 
im a little guilty of this but i usally do grind it shiny but sometimes i cant really get a sander in the places i need to weld
 
I just got some 1" sq tube today and I swear that it was more mill scale than steel... Crazy. Like it was some 3/4" plate or something.

I don't think enough guys are aware of how well flap wheels for your grinder can work. I strongly recommend picking up a variety of grits. I gaurantee you will not be using nearly as many grinder wheels once you do.

Remember, 90% of welding is preparation. Both cleanliness and and the line up count. The gap you are welding should never be wider than your filler. That means 1/32" for most guys on here! [;)

Here's a good link about the brake cleaner:

http://www.brewracingframes.com/id75.htm
 
Yep, there have been reports of serious neurological problems from welding after using brake cleaner to prep the surface. My Son Dan did that for a long time before we heard of the ill effects and he said there were times he was lightheaded after a welding session and it lasted for a while. He no longer uses it ever.

Don
 
And don't forget to prep where the ground clamp goes too. That makes a hell of different on Mig welding when you have a less than brilliant welder.
 
That's a great point. We also find that if we plug the mig straight into the wall vs using our 15 ft extension cord the welds turn out much better.

Don
 
My 250volt SIP 130 mig will weld 3/16" steel IF I get things set up just right, but it is so easy to get a cold lap or just an ugly weld if any of the previously mentioned parameters is out of whack.

And of course the bad weld is always just in that place you can't get a grinder, never right out on a piece of flat bar. [S
 
I have are to ask . I'm from South Texas , where there are alot of pipelines being constructed. And, I've done alot of structural welding myself, and never used cleaners before welding. I always grind and bevel where warrented, but don't think I've ever used brake clean or acetone or anything to wipe down the steel before welding. Is this just something you guys do to make the welds look perty ?
 
No, it's to remove contamination and to help ensure you good a good weld with no slag inclusions or porosity. Remember, all GOOD welds are pretty but not all pretty welds are good.

You can't grind out all contamination all of the time. Using Acetone is a very common practice when TIG welding aluminum, where perfect preparation is a neccesity for a good weld. It's really just about the best bet on that.
 
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