|
|
I bought some 2" wide 3/16" thick flat bar from McMaster to finish up a project. Everything else was hot rolled and I had already ground off all the mill scale where I was going to weld with a hard disc and roloc abrasive pad. So, since it was an 11th hour add, I thought I would buy cold rolled material so I would not have to do more grinding.I read the McMaster description of "Cold Drawn" as meaning there would not be any mill scale. (Was I wrong here?) The steel showed up and as expected was coated in oil. I thought this was a good sign that since it didn't have mill scale to protect it from further oxidation, it had been covered in oil.I cut it into pieces on the bandsaw, drilled holes in the pieces on the mill, filed down the edges, wiped clean with solvent, abraded weld areas with scrotch brite, wiped clean again, further brushed with TIG-steel-dedicated stainless bristled brush, etc etc and tacked in place. One some pieces I did some final weld prep with a die grinder (followed up solvent wipe to get any sprayed oil from the die grinder off, then wire brush to make sure there was no shop towel lint on the rough area, etc) to help with fitting.When it came time to TIG the tabs onto the frame, I started getting contamination in the welds and it became harder to control the puddle. Having just welded a lot of freshly prepped hot rolled square tube on the same piece and having excellent results with easy to control puddles and no contamination, I was surprised and confused by what was happening. Then as I finished a few beads, flipped up my hood and stared in real close, I saw that the surface of the new "cold drawn" tabs was flaking off like a bad paint job, or like scale, right along the edge of the weld / heat affected zone.http://www.mcmaster.com/#8910k533/=vfnt5eNext time I can save myself the frustration by just lighting sanding off the top layer regardless but I thought I would not have to do grinding since it was "cold rolled." It wasn't like it was a loose top layer. It stood up to hard scotch brite (3M maroon colored industrial surface prep pads) and hand wire brushing. It would come off with a grinder though.So question for you folks is do I misunderstand what being cold-rolled means for grinding/weld prep requirements? Could that flaking into the weld puddle have been predicted before hand? I'm used to having to grind off mill scale from hot rolled and am getting pretty quick at it. I thought that I wouldn't have to do so on this "cold drawn" flat bar.Maybe you guys can set me straight and add some clarity? Thanks for reading.
Reply:Either you had hot scaling from an over heated weld or the material had delaminated from bad rolling. If you see splitting and can bend the scalings that is delamination. If the flakes crack, that is just surface scale from a hot weld.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:I have used quite a bit of 1018 cold rolled from McMaster-Carr and have not experienced what you describe.
Reply:Shovelon, metalman21, thanks. First time I had used cold rolled for a project like this so I didn't get it. After grinding hot rolled, I have not had any issues like this to date. Sounds like from your feedback if I had not overheated the weld I would not have had an issue with the cold rolled either. I'll have to work on that.I'll get the new pictures off the camera. For now all I have is a picture of the same material on the little brother of the same project (slightly smaller version of same design). Unfortunately I didn't take any pictures of the surface before I wire brushed it. I'm fairly certain on the second build I did take those photos as the contamination was affecting the tab welds more.This picture is of the tab once a lap joint weld was done on the underside to attach a weld retainer nut (floating nut) underneath. The photo was taken after I tried to wire brush off the flaking (?) surface.Shovelon I'll try and see if there are any spots I didn't already wire brush off to see if I can bend the parts coming off. I was surprised by them and in a hurry so I went after them with a wire brush when they started coming up.
Reply:Is it possible that you got pickled&oiled mild steel that looks like cold rolled. It will still boil out scale yet has the same appearance.I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:That is pretty normal to what I get. The surface could be a result of the pickling process which has left it with a residue. Hot rolled has that scale which is the protective barrier but welds like crap. So you remove the scale and you end up with virgin steel. Looks fine to me.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:That looks to me like scale formed from getting hot. If the backside is getting red hot, it will form scale unless shielded by gas.My name's not Jim....
Reply:One feature of cold rolled vs. hot rolled mild is that the corners on mild are always slightly rounded instead of very sharp. Hard to tell in your pic, but are they sharp tight corners, or were they slightly rounded?I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Originally Posted by weldermikeOne feature of cold rolled vs. hot rolled mild is that the corners on mild are always slightly rounded instead of very sharp. Hard to tell in your pic, but are they sharp tight corners, or were they slightly rounded?
Reply:Mild steel will have slightly rounded corners. Cold rolled on the other hand are very sharp 90's.I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Thanks30+ yrs Army Infantry & Field Artillery, 25 yrs agoMiller 350LX Tig Runner TA 210, spool gunLincoln 250/250 IdealArcESAB PCM 500i PlasmaKazoo 30" vert BSKazoo 9x16 horiz BSClausing 12x24 lathe20T Air Press
Reply:Weldermike, I'm not sure how to describe it but I do have a picture from after the filing work.
Reply:Here are the photos for the work described specifically in the first post.First photo is the underside of one tab showing the stitch welds done after tacking but before welding out the top side. The welds shown here were the heat input that preceded the bubbling showing the second photo.This is the second photo of the top side after those bottom-side welds.Third and fourth photos are the same shot just different crop/zoom. Not sure if this counts as delamination but the photo makes it stand out.Fourth photo.
Reply:Weldermike, after re-reading your question, the corners were slightly rounded and were not tight sharp 90's.
Reply:You're getting the material waay to hot outside of the gas shielded area, and it's reacting with the atmosphere and forming a scale.That is an enormous HAZ, try moving like 2x faster and using as much heat as is required to do so.Last edited by MikeGyver; 01-12-2015 at 10:55 PM.Welding/Fab Pics: www.UtahWeld.com
Reply:It is normal for the back side of the steel to scale like that unless you keep it shielded. If you can reduce heat input on the bottom side you may be able to prevent the scaling on top side. Usually unless you clean the scale off the arc will want to wander a bit.Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power) Hobart MIG
Reply:Boostinjdm, MikeGyver, SquirmyPlug, thank you for the heads up on forming scale on the opposite side without gas coverage.Here's an example of one of the tube to tube Tee joints. These were ground down hot rolled steel square tube.Looking at my other pictures from the build, if the third picture of post 13 is a "huge HAZ" then I got a lot of huge HAZ's and I'll have to work on that.
Reply:It's worth noting that even materials that have had the millscale removed or whatever still may have a very light amount of oxidation on them and could be more prone to scaling than freshly ground material.Welding/Fab Pics: www.UtahWeld.com |
|
发表于 2021-8-31 22:10:48