TIG on Damascus High Carbon Steel application, Advice Needed

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I have been tasked to weld damascus steel comprised of 15n20 and 1084 steels. I am only puddling in some inclusions but ideally would not have the aid of filler material so as not to distort the pattern. If forced to use it, the filler could be ER70S-#. I really feel that I will probably have to use some sort of filler to give a convex weld (1/32 -1/16 circle spot welds ) since the piece can not be surfaced to get down to the level of the puddle floor. The piece is approx. 3/16" thick. I am planning on using 2% thoriated 0.020 or 0.040 tungsten with a gas lens and #4 cup. Any ideas on filler material and how this might behave? I have welded high carbon steel like this before but I have always had problems with porosity and blow outs because of the high carbon content. I usually use 3/32 tungsten though and I am hoping that the smaller tungsten will give me a tighter heat footprint and not blow out as bad.Any and all ideas are welcome. Thanks. This will be done on my Sync 250DX.Miller 250DXTD Cutmaster 100Duct TapeBFH
Reply:Just what are you trying to weld together?As soon as you melt the damascus section, the pattern will be distorted.  Because you melted it.  Whether you add filler or not.In general, welding on high-carbon means high preheat and then weld and then post-heat and then s-l-o-w controlled cooling.You are trying to "puddle in some inclusions", as in you have inclusions in the pattern-welded work (blade?) and are trying to 'erase' them?Nope, if you have inclusions then you have a bad blade/blank.  Scrap it and try again. IMHO.  The best laid schemes ... Gang oft agley ...
Reply:Is the item you're welding on structural, or decorative?  In other words, is it load-bearing and functional, or not?Smaller tungsten definitely sounds like a good idea if all you're attempting is to erase some surface imperfections.The patterns in damascus steel come about through precipitation of carbides during hot-working, subsequent cooling, and then etching with acid.  I'd expect that the heat of welding would redisolve some of those carbides.  This would alter the pattern and/or cause the region around the weld to lose any pattern entirely.  I gather you're trying to avoid this at all costs...I'd suggest preheating the piece, but I'm concerned about deterioration to the surface appearance if this is a decorative item.  I infer from your comment about surfacing that it is....Still, the right preheat and controlled cooling might help....Given the carbon content of the alloys you're dealing with, you might consider using a filler suited for cast iron....I see from a little research that the 15N20 alloy is a bandsaw blade material, and a Nickel Alloy.  I'm also guessing at this point that we're talking about a knife blade.  Bob Warner is a knife maker who posts on this website, and I know he's worked with Damascus steel.  Wait and see if he responds or send him a PM.  A little digging reveals the 15N20 is .75C, .75Mn, 2.0% Ni.  A nickel-based filler, like those used for cast iron might be a viable choice.  So would a tool steel alloy with a few % nickel.  Nickel promotes the formation and retention of Austenite.  This is the form that iron takes on when it's heated above the A1 critical temperature(when it loses it's magnetism).  When iron cools usually changes structure back to Ferrite, or in your case mixture of Ferrite and Cementite.  Using a high nickel filler metal would tend to force the material to remain austenite.  The steel microstructure changes volume when it makes these transitions from one phase to another.  This volume change is one of the contributing factors that causes quench cracks in high carbon steels.If you've got the money, you might contact a company that makes filler metals for repairing tool steels; someone like Weld Mold Company.  They may have a tool steel or low alloy steel  filler metal with similiar manganese and nickel content.Either way, you've got a tough nut to crack here....Given the spot size, this sounds like a project best handled by a specialized welder, like a tool & die repair shop.  Someone with micro-TIG or laser welding equipment.  That said, I'm not trying to suggest you can't do it.  Just a thought that occurred to me while I was mulling over your post.  I know somebody local who does this kind of work, if you get in a bind you might find someone similar in your neck of the woods to consult with...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Thanks for the replies, sound advice all around. I have decent knowledge about the stages of steel crystallization, and this is not a structural item. This is a mosaic piece and the pattern will not be discernibly faulted by welding it as long as I can keep the puddle small. Especially since it will be etched afterward. This really isn't even necessary but my client is interested in the process and would like to test it. My biggest concern is taking the steel past critical and having a blow out. I have a paragon oven that I can program for any preheat or post heat cycle, but I need it low enough to not form scale. There is a man that does this regularly (and successfully) but he is not of the internet inclined. I may try to contact him and ask about fillers and heat cycling. As long as he is willing to share. I'll do some more digging and see what I can find out about specialty fillers. Unfortunately the smallest ER70S-2 I can get locally is 1/16. I can grind it smaller but then I have to worry about disturbing the deoxidizers in it.  Thanks again and have a good one.Miller 250DXTD Cutmaster 100Duct TapeBFH
Reply:You probably know this but MIG wire is ER70S. So that gets you down to .023 and available at Lowe's or Home Depot in 2 pound rolls (I think ).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:Actually, I am MIGnorant ( I call dibs on that for a signature ). Thanks for that tidbit, I had no idea what it was. But I can get my hands on some of that tomorrow if needed.Miller 250DXTD Cutmaster 100Duct TapeBFH
Reply:If you've got a small furnace, look to see if it's got a port, a compression fitting of some kind.  Some small units, particularly those sold for laboratory use, have a gas port.  IF yours does, you could flow Argon into the furnace and prevent any scaling from your PWHT.  You might also be able to just drill a hole and install a swagelok fitting of your own.  You might need to make some trial runs in order to determine just how much gas flow you need to purge the furnace chamber.Just another quick idea...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:along the lines of early discussion...Esab makes 2 MIG filler metals... Spoolarc 95 and Spoolarc 120 that have chemistries that include similar Mn and Ni contents to your damascus steel alloy.  Both should come in small diameters, although I'm not sure you could get a MIG spool in less than 11lbs.Both alloys also have some Cr and Mo, but in small amounts.  Carbon contents are much lower as well... But I don't think these would have a negative impact on the results you're trying to achieve.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Note:You are actually refering to a pattern-welded object, and not a 'true' Damascus steel object.Although the original production materials and methods of 'true' Damascus steel have been lost to history, scientists and such have determined that the pattern in "Damascus steel" is NOT formed from forging alternating materials together (that process is more correctly called "pattern welding") but from the non-homogeneous metallurgical structure of the steel alloy itself with the various carbides and other alloying elements/structures swirling and varying in the steel itself.  See also Wootz steel and Bulat steel.A pattern-welded blade (or object) could have 300-512 (or more!) layers of alternating materials.  The ABS Master smith test requires the forging of a 300-layer blade and starting with two layers and folding over just 8 more times yields 512 layers (2^9 = 512).If the blade/object is 1/8 inch thick and 300 layers, then each layer is nominally 0.00041667 inches thick.  That's less than half a thou thick per layer!  Make the blade/blank/object 1/4 inch thick and 300 layers and each layer is then nominally 0.00083 inch thick.Then you have to identify which material the layer you are trying to 'touch-up' actually is, and then control the fusion/penetration depth to -that- layer only (somewhere about 1 thou or so).  If you add filler and/or intermix layers, you will have a 'witches brew' of metal which in addition to the HAZ itself will most likely show up pretty visibly once the etch/polish/blue/etc steps are done.Can you weld such an object?  Probably, with some care and special treatment.Would such a weld be visible? Probably (most likely IMO).  The best laid schemes ... Gang oft agley ...
Reply:they make 0.020  tungsten?
Reply:MIGnorant.  Originally Posted by weldbeadthey make 0.020  tungsten?
Reply:I just stumbled upon this thread. I know it is pretty old now and am wondering what happened with this.I am unsure exactly what the goal was originally. Was it to take the two steels and make a usable piece of damascus (I know MoonRise) or was it to take a piece of damascus and weld something to it?If you finished what you were doing can you post a photo?Bob
Reply:Bob,The OP was trying to repair some small surface pits or imperfections in a piece of damascus or pattern welded steel.  I'm curious to know what the end result was as well... Originally Posted by Bob WarnerI just stumbled upon this thread. I know it is pretty old now and am wondering what happened with this.I am unsure exactly what the goal was originally. Was it to take the two steels and make a usable piece of damascus (I know MoonRise) or was it to take a piece of damascus and weld something to it?If you finished what you were doing can you post a photo?Bob
Reply:OK, makes sense now.If the steel was already made into something like a knife and he welded on it, he ruined it due to heat. The piece would have to be re done and re-heat treated. The pattern would be disturbed and the piece would look awkward.The way it sounds to me "Puddling in some inclusions" means he had some bad forge welds and got garbage in the steel.  If there were several locations, there are probably more that are not seen. I would have pitched the piece and started over.Wonder what he did.