Welding Tungsten (parts made from it)

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Does anybody have experience welding tungsten sheet? We got a new job at work, its a little box for a mammogram machine. Its made from tungsten to keep the radiation in.I have already made a couple but the main production run has not started yet. .005 tolerance What filler did you use? Did you have any problems with the material itself being "inconsistent" I dont know if thats really the word. Sometimes it welds fine, others it pops and spits a little, an heats differently in that area.I will take some pics when I get a yes or no from the customerYup
Reply:This is all new to me..Tungsten to hold radiation "In" Grind some.....and let it out..I can not see welding Tungsten with itself.Whatever happens be sure to take pics.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Yeah...  I'm all eyes & ears on this subject too!Wouldn't tig welding tungsten really be... like.... MIG ?The best things in life all come on a stick!
Reply:Originally Posted by RabidfishYeah...  I'm all eyes & ears on this subject too!Wouldn't tig welding tungsten really be... like.... MIG ?
Reply:In many cases, a company will call for very tight tolerances on weldments, as a way of scaring a lot of shops away from bidding on the job.  In conversation with the customer, you may want to NICELY ask them how the part is used, and why the tolerances are so critical.  You may find that they're fine with even 1/16" out of spec...which could save you a lot of material, rework cost, and labor time.
Reply:They have shown us the part that fits into it, and its a tight squeeze. The first one I did was .003 under the low end and it didnt even come close to fitting. It seemed ridiculous til thay showed up with the other parts, Im thinkin, ".005 on a weldment? these guys are friggen nuts!" but the stuff barely moves when its welded.You've never welded this stuff engloid? I figured you might be one of the people I would hear from on thisYup
Reply:Hmmm, me-thinks .005 is a "machine after welding" deal.Pure tungsten CTE is 2.44 µin/in-°F (@Temperature 68.0 °F) and 2.61 µin/in-°F (@Temperature 68.0 - 3630 °F).  For reference, low-alloy steel has CTE in the range 5.61 - 8.28 µin/in-°F, plain carbon steel is in the range 6.11 - 9.22 µin/in-°F.  Aluminum is 15.2 µin/in-°F (pure, alloys vary from 4.44 - 15.2 µin/in-°F).Even though its CTE is pretty low, that still works out to 15 thou over an inch of weld from melting point back to room temp.  Itty-bitty welds and parts would have smaller expansion amounts, just because they are smaller.
Reply:Originally Posted by zapsterThis is all new to me..Tungsten to hold radiation "In" Grind some.....and let it out..I can not see welding Tungsten with itself.Whatever happens be sure to take pics.....zap!
Reply:Someone is confused.Lead is used as a sheild from radioactive materials. Not tungsten..005 thousandths? or .005mm?AWS certified welding inspectorAWS certified welder
Reply:I didn't think I was going to be working on this today, but the fixture showed up so I did one box to try it out. I didn't have my -ahem- her camera with me so I took pictures with my phone kinda crappy but you can see what it looks like. After I weld it, the welds get blended in and they powder coat it. The .005" thou tolerance is not for machining. That is the finished part when we are done. And now that we have this fixture it comes out within tolerance. Before, I was doing it with 1-2-3 blocks, clamps and four letter words, and I got close, but not close enough.Tungsten is indeed used for radiation shielding, nobody is confused.Here go the pics, I will bring the camera in and get some decent ones on Monday. Attached ImagesLast edited by Burnit; 07-11-2008 at 07:20 PM.Yup
Reply:This stuff is thin. Attached ImagesYup
Reply:The box on the fixture tacked up. The hole is where the X-ray comes out apparently. Attached ImagesYup
Reply:Still workin on getting the beads how I like em, but I blend them out right away anyway. Attached ImagesYup
Reply:Originally Posted by EngloidIn many cases, a company will call for very tight tolerances on weldments, as a way of scaring a lot of shops away from bidding on the job.  In conversation with the customer, you may want to NICELY ask them how the part is used, and why the tolerances are so critical.  You may find that they're fine with even 1/16" out of spec...which could save you a lot of material, rework cost, and labor time.
Reply:Originally Posted by zapsterThis is all new to me..Tungsten to hold radiation "In" Grind some.....and let it out..I can not see welding Tungsten with itself.Whatever happens be sure to take pics.....zap!
Reply:Thanks for the photos.I have a couple of questions.Do you absolutely for certain know what the material is that you are welding?Is the person that is having this made an engineer or just a messenger?AWS certified welding inspectorAWS certified welder
Reply:Originally Posted by BurnitThis stuff is thin.
Reply:Very interesting subject by the way.I looked up tungsten sheet on Google and learned a lot The tungsten is used to reduce weight and it has a high copper content to protect with heat issues as well.Each company seems to have a propietery metal that they are trying to market.AWS certified welding inspectorAWS certified welder
Reply:Wow hearing about tungsten being used for something else for a change.   We use tungsten wires to create a corotron used in xerographics.  I guess there is life for tungsten other than light bulbs and welding.   weld it like you own it
Reply:The customer that comes to our shop is the engineer. And the first thing I said without trying to sound stupid was "Why is this made from tungsten" It is alloyed with nickle and copper.The caliper is .100" per revolution, yup around .042" thou.I have been reading about it too. They use it for some wild stuff! Ordinance, armor, radiation shielding, all types of stuff.The tolerance is for the inside dimensions, I think its ridiculous, its getting changed.Yup
Reply:Originally Posted by BurnitI am really starting to think that is the case. All this thing does is sit over something that emits X-rays. It gets three countersunk holes in each side for the cover plate screws.They are swingin by Monday to check this one out. I will ask. We have already requested a deviation allowing us .010" Because we found out that the people cutting the material get .010" and we get .005" How does that work?
Reply:Wait a minute.It's a 19 gauge (0.04375 inch thick) 5-sided sheet metal box, made of tungsten alloy sheet, and the customer wants the tolerances held to 5 thou?And you are TIG welding 5 sheets of metal to make up the box.  They didn't even brake form at least one sheet into shape to take the place of 3 current sheets and reduce two complete seams having to be welded.  Or brake form the entire box and then just have to weld 4 seams instead of 8 seams.This is a demo, prototype, proof, or other small production item.  Otherwise they'd probably stamp it or HIP it or some other production method.Now that you have a jig/fixture, it should be a little easier to do the job.  But 5 thou is still a pretty tight tolerance for a thin gauge sheet metal box.I'd probably say to make the box on the 'big' side, and then squeeze/press/swage it down to finished size.re: the pictures.  You were too close for the camera to focus.  Next time, pull back until the area of interest is in focus, and then zoom/crop the image afterward.  But it looks like you got some decent pictures (lighting, holding still, no glare, no shake/motion blur) except for being too close for the camera to focus.And it is totally ridiculous for the material cut dimensions to have a 10 thou size tolerance and then to want a 5 thou assembled tolerance!  With tolerance stack-ups, if the material is being sized to +/- 10 thou, you are looking at 10-30 thou finished tolerance stack-up depending on where the sizes and dimensions and tolerances are.  Unless the cut tolerance is 10 thou on length/width of the sheets and they are relying on holding the sheets flat against the jig/fixture and the 5 thou finish dimension tolerance is for the 'ID' (inside dimensions) of the box and the outside dimensions can run 'wild'.  That I can sort of see.Do you have to do the welding in a glove-box like when you do titanium things?
Reply:It would be interesting to find out if indeed it is the radiation shielding, or in fact the radiation source.  While tungsten, due to it's density, can be used as radiation shielding, it's cost prohibitive when compared to lead.  And given the particularly tight manufacturing tolerances, I'm thinking this might be part of the emitter.  Most x-ray machines use an electron gun configuration to generate an electron stream at high velocity, and direct it at a tungsten target.  The kinetic energy transfer of the electrons to the target results in1.  Heat2.  X-rays.While almost all materials will produce x-rays under an electron stream, tungsten is the preferred material because of it's high density, it generates high energy x-rays when bombarded with electrons (bremsstrahlung is the technical term for it). It also deals very well with the heat generated by the kinetic energy transfer.I use tungsten targets to set the power levels on my electron beam welding machines, which are really nothing more than an x-ray machine on steroids, and I have better than 1/2 inch of lead on the exterior of the chamber to deal with the x-rays produced.Last edited by kbnit; 07-14-2008 at 04:59 PM.Reason: typoI r 2 a perfessional
Reply:Originally Posted by MoonRiseWait a minute.It's a 19 gauge (0.04375 inch thick) 5-sided sheet metal box, made of tungsten alloy sheet, and the customer wants the tolerances held to 5 thou?And you are TIG welding 5 sheets of metal to make up the box.  They didn't even brake form at least one sheet into shape to take the place of 3 current sheets and reduce two complete seams having to be welded.  Or brake form the entire box and then just have to weld 4 seams instead of 8 seams.This is a demo, prototype, proof, or other small production item.  Otherwise they'd probably stamp it or HIP it or some other production method.Now that you have a jig/fixture, it should be a little easier to do the job.  But 5 thou is still a pretty tight tolerance for a thin gauge sheet metal box.I'd probably say to make the box on the 'big' side, and then squeeze/press/swage it down to finished size.re: the pictures.  You were too close for the camera to focus.  Next time, pull back until the area of interest is in focus, and then zoom/crop the image afterward.  But it looks like you got some decent pictures (lighting, holding still, no glare, no shake/motion blur) except for being too close for the camera to focus.And it is totally ridiculous for the material cut dimensions to have a 10 thou size tolerance and then to want a 5 thou assembled tolerance!  With tolerance stack-ups, if the material is being sized to +/- 10 thou, you are looking at 10-30 thou finished tolerance stack-up depending on where the sizes and dimensions and tolerances are.  Unless the cut tolerance is 10 thou on length/width of the sheets and they are relying on holding the sheets flat against the jig/fixture and the 5 thou finish dimension tolerance is for the 'ID' (inside dimensions) of the box and the outside dimensions can run 'wild'.  That I can sort of see.Do you have to do the welding in a glove-box like when you do titanium things?