mild steel filler metal help

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Hey guys-I've been practicing a bit, learning to TIG with my new T/A 185.I've just played with ~0.140 mild steel. If I just run some stringer beads with no filler I can make some nice beads. Once I tried making a fillet weld between 2 pieces at 90 degrees though (while adding filler) I had porosity like there's no tomorrow.I made one real nice lap joint with filler, but when I went back over it trying to "even out" the weld beads (they wandered a touch) it too went porous like the others.I tried gas glow rates ranging from 10-25 CFH using my gas lens, #7 ceramic and 3/32 tungsten all to no avail. I degreased all the metal with acetone and used a 60 grit flap disc to dress the surface before welding too.Given all the trouble seemed to start once I added filler, I'm almost wondering if they gave me the right filler rods? The rods looked almost coppery color and didn't have anything written on them or stamped into them like my stainless and aluminum filler rods do.I will admit I didn't clean or degrease the filler rods - but then again they were bought only a few days before.Anyways, I'm going to pick up some new filler rods tomorrow for practice on the weekend. I'd like a few "recomended" rods or alloys to ask for -- to try and eliminate that variable.Thanks in advance.Last edited by turboguy; 08-29-2008 at 02:09 AM.
Reply:Are you welding forehand?  (push)Dont' go back over your welds.  What you do the first time is what you get.With a gas lenz, 10 cfh or less should be fine.  The electrode should stick out 1/8" to 1/4", maybe a little more with the gas lenz.Arc should be no longer than the diameter of the electrode.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by David RDont' go back over your welds.  What you do the first time is what you get.
Reply:Yeah going over a weld again is bad practice.Generally mild steel filler is stamped with an idenitifcation, copper coating is normal. I have some 1mm filler which isn't marked but the tube it came in and the paperwork with it state it's er70s-2. It's possible you have oxy fuel filler which doesn't contain the necessary deoxidisers required for arc processes. If the invoice or anything has a designation begining with RG you have O/A filler, you want an ER type filler
Reply:Originally Posted by hotrodderIf the invoice or anything has a designation begining with RG you have O/A filler, you want an ER type filler
Reply:Originally Posted by hotrodderYeah going over a weld again is bad practice.Generally mild steel filler is stamped with an idenitifcation, copper coating is normal. I have some 1mm filler which isn't marked but the tube it came in and the paperwork with it state it's er70s-2. It's possible you have oxy fuel filler which doesn't contain the necessary deoxidisers required for arc processes. If the invoice or anything has a designation begining with RG you have O/A filler, you want an ER type filler
Reply:The 3/32" filler I'm using in class is stamped, but it's so small I can hardly see the stamp, let alone read it. If the LWS guys just handed you some filler, that's where I'd start. As the others have said TIG must have the deoxidizers in ERxxS rods.Since it's possible to do multipass TIG welds: if you're going to try to dress welds, get a small rod (.040 or 1/16") and add filler as a second pass. I think what happens is, even on the second pass, the filller adds the deoxidizers that prevent porosity. This will build up your weld size, which may not be desired.9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:Originally Posted by tmorgan4David,Would you mind talking about this a little?  I know it's a fairly common thing amongst "new" TIG welders to go back and make a more presentable weld after some filler has been put down.  I admit that I've done it several times.  Is this something that should be avoided?
Reply:Originally Posted by Craig in DenverSince it's possible to do multipass TIG welds: if you're going to try to dress welds, get a small rod (.040 or 1/16") and add filler as a second pass. I think what happens is, even on the second pass, the filller adds the deoxidizers that prevent porosity. This will build up your weld size, which may not be desired.
Reply:Originally Posted by RojodiabloWe have a WINNER!!!!!!!
Reply:Originally Posted by RojodiabloOkay, what happens here, is every time you lay a bead on metals, you change the base metal. That is why fillers are usually not the same material. A half dozen key words fall in here; martinsite, carbon precipitation, on and on. But what you've done is change the metal at the welded joint. So, when you just go over it again, from a purely strength related point, you can make a weld more brittle, and many times a weld will have a lot of stuff mixed into the weld. Re-heating the weld can bring these things out, and up to the surface. And many of them are not friendly to the weld appearance. Cratering is a very common issue when you go back over a weld with the torch. If you have a bigger weld to do, like on thick material, it is necessary to add more filler with each pass. Otherwise, you can get 2 things- a weld that is not sound/ brittle, or, a weld that has a lot of undercut.If you are going back over a weld, it is better to add a little filler into the mix as you go, critical silicons and other things that burn up on the first pass need to be added back into the weld. If the weld is a bit grumpy, and you want to clean it up, I suggest you grind it a bit, then hit it with a little filler to clean it up properly.If no one is looking, and the part is non strucutral, and only cosmetic, it does not matter. But don't do it on a chopper frame or similar critical part.
Reply:Originally Posted by tmorgan4Thank you for the explanation!  This makes a lot of sense since I have noticed some of the things you pointed out while going over a weld a second time.
Reply:The fact is you can stack beads all day but as far I know you don't gain anything when say a fillet weld eceeds the thickness of the materials being welded. Say a 3/4 inch fillet on a 3/8 plate.'Mike
Reply:i think the practice of going back with the torch and no  filler to fix up a mess  which is ok on o/a welding, because the slightly carburizing flame protects the mtal from oxidation, is not okay in tig for the reasons stated..?
Reply:Originally Posted by weldbeadi think the practice of going back with the torch and no  filler to fix up a mess  which is ok on o/a welding, because the slightly carburizing flame protects the mtal from oxidation, is not okay in tig for the reasons stated..?