Titanium TIG welding advice

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I just tried welding titanium for the first time tonight. I have a Lincoln precision TIG 185.I am welding 2 piece of 3AL 2.5V tubing at a 90 deg angle with 6AL 4V as filler.My welds are shinny and I get a lot of coloration, nice shiny hues of blue, yellow, light red and orange!!!My welds also show some surface cracking much like a spider web. (don't know if it is just surface craking or deeper).I want to make a motorcycle frame and some brackets, no aerospace or aircraft thing here...I tried a flat pass on top of the tubing with bigger filler wire and I only got discoloration at the end of my pass... So is it simply a shielding issue? Would those welds be acceptable for a motorcycle?Thanks in advance for your reply(ies)Eb
Reply:http://www.thefabricator.com/arcweld...cle.cfm?ID=878http://www.millerwelds.com/resources...tanium-weldingLincoln precision TIG 275Millermatic 140 MIG
Reply:Pictures would help
Reply:Thanks for the links.Brian, sorry I do not know how to post pictures, one of those things that should be simple but are not...This may kill my project, I don't know how much of my problems could be related to my argon quality but I know it is hard to keep a good shield around tubing because of the shape. I was able to get a good weld on the top of the tubing with limited coloring at the end of my pass. I'll call my supplier and see what they can provide... I live in a remote area so it takes time and money to get anything.Thanks again
Reply:You can use a bigger cup, turn up the gas to 20 cfh, but no more; after 20, you actually whirlwind the gas, and it brings in outside air. Ti is similar to SS, if you have a little rainbowing, it's usually a close to ideal weld. Obviously, a perfect weld will be no discoloration at all, but not too likely in most circumstances. If the weld is too hot, you'll see black sooting, and lots of heavy bluing. Be sure you get good at keeping that torch pointed at your weld after you shut down to post flow cover your welds with argon until critical cooling is over. I highly doubt your argon is bad unless you see bad results on SS and regular steel also. CLEAN that tungsten, and the cup.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Thanks Rojodiablo,I am not giving up yet, I might have been too hot and my argon flow may have been too high, I'll keep on trying with the sample that I have but I find it harder than I thought. I have no problem with SS. I wonder how much imperfection I could live with, given that I am not working on airplane parts although I would not like my frame to crack and break on the road, even at 60 mph...Thanks for your help
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Reply:Originally Posted by ebhdI just tried welding titanium for the first time tonight. I have a Lincoln precision TIG 185.I am welding 2 piece of 3AL 2.5V tubing at a 90 deg angle with 6AL 4V as filler.My welds are shinny and I get a lot of coloration, nice shiny hues of blue, yellow, light red and orange!!!My welds also show some surface cracking much like a spider web. (don't know if it is just surface craking or deeper).I want to make a motorcycle frame and some brackets, no aerospace or aircraft thing here...I tried a flat pass on top of the tubing with bigger filler wire and I only got discoloration at the end of my pass... So is it simply a shielding issue? Would those welds be acceptable for a motorcycle?Thanks in advance for your reply(ies)Eb
Reply:Originally Posted by RojodiabloYou can use a bigger cup, turn up the gas to 20 cfh, but no more; after 20, you actually whirlwind the gas, and it brings in outside air. Ti is similar to SS, if you have a little rainbowing, it's usually a close to ideal weld. Obviously, a perfect weld will be no discoloration at all, but not too likely in most circumstances. If the weld is too hot, you'll see black sooting, and lots of heavy bluing. Be sure you get good at keeping that torch pointed at your weld after you shut down to post flow cover your welds with argon until critical cooling is over. I highly doubt your argon is bad unless you see bad results on SS and regular steel also. CLEAN that tungsten, and the cup.
Reply:Thanks quasi, I am just starting my homework obviously... I am not getting any sooting (except on the back part which was not protected at all for my first try), just coloration, but fairly intense so definitely some contamination. The thing that worried me most however was the surface cracking that I could see from looking up close, since I only saw those on discolored welds I think I may be OK once I solve that problem. I use a 1/16 tungsten and my tubing is 0.065 thick, at 90 amps I may also have been too hot.I like the tin foil idea a lot, I just ordered a #10 cup with a diffuser nozzle and a Y adapter for back purging. If that does not do it I may have to give up since I cannot weld a motorcycle frame in a chamber because of the size... The welding supply shop told me that there is a guy in the area that does Ti but he is gone for the winter... I'll try talking to him next summer.Building a motorcycle frame requires a lot of welding in tight hard to access areas, a lot of tacking would have to be done on the jig so I will have to be able to do some welding in uneasy positions, hopefully final welding could be done in better positions. Not surprising that there isn't any motorcycle frame made of Ti out there.Thanks for the input
Reply:I hope you can get this to work with Ti but I am wondering if you need it.Will this be a race bike, chopper? Performance or cruising?Would be able to do it quicker and easier with something like chromoly and still get the properties and strength to weight you are looking for?Like I said if you really want Ti I hope you can make it work but there are also other materials that could be good alternatives.I always wanted to do one out of aluminum.When I was building choppers the shop I worked at wouldn't even consider it. They said it was too common for alum chopper frames to fail.On the other hand my CR250 has an al frame and so do a lot of sport bikes.  I know a lot of engineering goes into them but it does show it can be done.Lincoln precision TIG 275Millermatic 140 MIG
Reply:Originally Posted by ebhdBuilding a motorcycle frame requires a lot of welding in tight hard to access areas, a lot of tacking would have to be done on the jig so I will have to be able to do some welding in uneasy positions, hopefully final welding could be done in better positions. Not surprising that there isn't any motorcycle frame made of Ti out there.Thanks for the input
Reply:I have been recommended to use chromemoly quite a few times indeed! My intention is to duplicate a stock frame as much as possible and so chromemoly would not save a whole lot of weight in the end because of the cast pieces which I would duplicate with billet parts. I have been buying Titanium for a while when the price was right so I am not completely out of budget. No racing or performance goal, just trying to come up with the lightest street bike possible. I was considering Titanium cylinders but the poor heat conduction threw that idea away. Aluminum has been done but there seem to be some problems with it. I am now thinking about fork tubes as well but I would think 6AL 4V would be mandatory for that application and very hard to find or expensive to machine in those dimensions.Thanks for the adviceEb
Reply:You need a monster lens and a trailing shield, bare minimum.  You need a 100% argon back purge on EVERYTHING.  I wouldn't trust it in a million years without verifying that with an O2 meter.  Titanium that loses it's purge will snap like a saltine cracker.  Where fatigue is an issue, anything other than a light straw color is unacceptable.  At 90 amps, I highly recommend you look at the backside of your joint.  I will almost guarantee you it has a crusty brown appearance.  Are you making the entire frame out of .065?  Way too thin.  I see road bicycles constructed of Ti alloys with heavier wall thickness than that.  Tubing diameters are often increased when converting a design from steel to Ti.  I'll be completely honest here.  An attempt to recreate a factory designed piece in a completely different material with no real world testing, engineering, or in-depth knowledge of that material's mechanical properties is an absolutely terrifying concept, and in all reality, I see this one ending up in a hospital stay.  I've welded Ti, built 7 second drag cars, and am employed as a welding engineer, and I wouldn't touch this one with a 40 foot pole.  Take a look at the BSA bikes from the 60's and 70's.  They were all titanium.  A designated engineering team redesigned the frame entirely after being asked to just duplicate the steel frame in Ti.  It still broke.  A lot.Last edited by Supe; 01-06-2010 at 09:53 AM.
Reply:Hello Eb, you will likely receive a number of suggestions from those who are out there and have had varying experiences with working with titanium. Teledyne Wah Chang is a major supplier of titanium products, I believe another source is Timet or something fairly close to that. Do some googling and research of those topics and you will likely find a lot of information relative to welding and processing of titanium. If my memory serves me correctly there are over 20 different TI alloys, they are not designed to be intermixed and they also require grade specific fillers when welding them, otherwise, you can have issues that could lead to failures. Completely shiny, no color, is the ultimate goal when welding TI, colors indicate contamination and will degrade structural or other characteristics. Clean, clean, clean, proper shielding on both the surface being welded and the other side, or inside if that is the case is very important for successful welding. Alot of TI is welded in glove boxes or similar enclosures, otherwise, as was mentioned by many of the others, special attention to using the largest possible cup, along with a gas lense prefferably and in conjunction with back-purges, trailing cup assemblies and a host of other rather special shielding aids is the way to successfully weld TI. Titanium is not difficult to weld, the difficulty comes in properly shielding and handling the material and selecting and knowing the specific grade of TI to provide the proper alloy matches and other specifics. Good luck on your project and certainly keep us posted on your progress. Best regards, Allanaevald
Reply:Originally Posted by SupeAre you making the entire frame out of .065?  Way too thin.  I see road bicycles constructed of Ti alloys with heavier wall thickness than that.  Tubing diameters are often increased when converting a design from steel to Ti.
Reply:What's up with those 'bikeschool' ceramics? $90 for a weldcraft large diameter gas lens set up (even if it's been bastardised for use back to front)! The CK set up i mentioned in my last post has a larger ID and more importantly the gas lens screen is sized to the nozzle... http://www.ckworldwide.com/gas_saver.htm. Cheaper tooEB, replicating a steel frame with a different material is rarely done because different materials have such different properties. Titanium alloys may have very high UTS and be around half the density of steel BUT Young's modulus fo Ti is around half that of steel i.e. titanium alloys are around half the stiffness of steel alloys. Similar deal with aluminium, around a third the density of steel but 1/3 the stiffness too, hence the difference in frame design with motorcycles and very different ODs and wall thicknesses with bicyclesOh, because you can't typically use a trailing shield due to joint geometry it's fairly typical to weld in short runs- gas nozzle size determining weld length...[ame="http://www.youtube.com/watch?v=RWQYV5tgkKI"]http://www.youtube.com/watch?v=RWQYV5tgkKI[/ame]Last edited by hotrodder; 01-06-2010 at 04:17 PM.
Reply:Very interesting video, I did not think he would be using such a low pulse frequency, I'll try that.About bike frame, a friend of mine who does bicycle racing said he saw a cut Ti bicycle frame and that it was "paper thin".I was planning on using 1.250 dia tubing instead of the stock 1.125. the stock frame is made of very soft mild steel of which I am not sure of the thickness (probably cold rolled type of) some of you might have already guessed by now that I am trying to duplicate a stock HD frame of the '69 to '84 type. I have a hard time to imagine Ti being less stiff than that stuff, but good point and I was not aware of that, I'll have to consider that as well. Which Ti do they use for aircaft landing legs? I was planning of using 3AL 2.5V tubing simply because this is what is easily available, I reckon it is not the strongest type however.Now, the design of the stock frame really puts the tubing in tension, the weight is being supported at the fork neck and the rear shock mounting point, the stress is distributed in between. The motor is a heavy part and the lower mounts puts the down tube in tension, the stress will be at the welding point of the fork neck and the downtubes and at the welding point of the downtubes and the rear casting. The stock frame has been known to break at the joint of the left rear bottom casting and up tubes, the factory corrected that with an additionnal plate...I really appreciate everybody's advice and will have to take all that into account. I do not want to break any bones anymore!Eb
Reply:Eb, the Ti can be heat treated after welding, and that is how much of the parts used in structural applications gets it's stiffness. The key benefits of Ti are: Weight, heat resistance, and corrosion resistance. The landing gear on jets is a mixture of many parts; we used to have Ti springs on our racebikes. They were throw away items at the end of a season. The shop who revalved our shocks was doing some jet stuff; much was high tensile alloys, inconel and others. There were parts that were Ti, but none were the actual shock housing; there was a large casting that was Ti on one assembly; but that's a whole different ballgame than tubular fabrications.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Yeah, bicycles use real thin wall tube. Reynolds grade 9 (3Al2.5V) are around 0.9mm for chain/seat stays and the thicker butted sections. Away from the butted ends 0.7mm. Grade 5 (6Al4V) lighten the butted areas and stays to 0.8 - 0.85mm. Reduce those wall thicknesses by a 1/3 to 1/2 for high end steel alloy tubsets though, Reynolds 953 is/was available with 0.3mm wall in places!With regards to stiffness, within a material group different alloys and heat treatments DO NOT make things stiffer by any realworld amount. Big changes in yield and UTS numbers but 4130 is no stiffer than low carbon mild steel for exampledatasheet for  grade 9 Tidatasheet for grade 5 TiLast edited by hotrodder; 01-06-2010 at 08:24 PM.Reason: a couple of links
Reply:Originally Posted by hotrodderYeah, bicycles use real thin wall tube. Reynolds grade 9 (3Al2.5V) are around 0.9mm for chain/seat stays and the thicker butted sections. Away from the butted ends 0.7mm. Grade 5 (6Al4V) lighten the butted areas and stays to 0.8 - 0.85mm. Reduce those wall thicknesses by a 1/3 to 1/2 for high end steel alloy tubsets though, Reynolds 953 is/was available with 0.3mm wall in places!With regards to stiffness, within a material group different alloys and heat treatments DO NOT make things stiffer by any realworld amount. Big changes in yield and UTS numbers but 4130 is no stiffer than low carbon mild steel for exampledatasheet for  grade 9 Tidatasheet for grade 5 Ti
Reply:I know nothing about To welding. However I do know about MTB frames. I used to import Boulder Bikes into the UK. In the line up was a frame called the Defiant Available in Steel, Al and Ti. Now before I started to import the bikes I had a Steel Defiant and it was (still is a mate has it now)  a very nice bike to ride, solid. When I became the Importer I sold a Ti frame to a friend of mine, The frame was beautiful. Brushed naked Ti (Homer stylie drule). The tube Dia was almost the same as the Steel version, and it rode Soooo differently, it truly was a bike to behold. In the 18+yrs Martin has owned that bike I had it repaired 4x, only tiny cracks, nothing major but none the less requiring welding. If it wasn't for the fact he licks it clean after each ride, they would not have been found until it was too late.I've seen other makes just fail, without warning. So the idea sound nice, but in truth you are playing with fire, unless you do a LOT of R&DLast edited by Shox Dr; 01-07-2010 at 04:04 AM.
Reply:Rojo,We're talking about different things. That HREW bumper that got dented... it yielded i.e. was subjected to forces which exceeded it's yield strength permantly changing it's shape. 4130 has a higher yield strength and so takes more force to permantly change it's shape. Within the elastic range (where a chassis hopefully spends it's life!) there is next to no difference between low carbon steel, annealed, normalized or hardened 4130 or any other steel alloy. Chart of Young's modulus for various metal alloys (note the units, differences between alloys within a metal group are so small they're insignificant)... http://www.engineeringtoolbox.com/young-modulus-d_773.htmlScroll down to 'stiffness' if you don't want to read the whole article... http://www.netwelding.com/Heat_Treated_4130.htm
Reply:Interesting project, I wish you success.A couple of guys I know are also building a frame (actually a whole bike), here's some details that may help you with your project.http://forums.dragbike.com/forum_pos...?TID=10903&KW=Regards to all.Working on cars and bikes is my hobby, learning to weld the pieces together is my quest.
Reply:"it's not an airplane, just a motorcycle"hey, roadrash and guardrails is a bad way to die.   I think I'd PREFFER augering in to a feild."I cant imagine it not being as stiff"physics does not care about your imagination.  nor does material science.  you need some more education.Thanks for your input dsergisonEb