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  • #16
    I know its been a awhile and I have not reread the full thread, but I have a few more questions regarding titanium.

    I am still looking to do build a Ti exhaust system, a few questions I have are in regards to the welding atmosphere and temperature/application.

    On the welding atmosphere, I was thinking of trying to use a sandblasting cabinet, add extra sealing and ad a port for vacuum or argon. The other option I was thinking of was to cap the ends and back purge the inside with argon, and sure a larger cup and/or build a trailing cup to shield the fresh weld. The welds are not going to see mechanical stress, but will see thermal, and need to seal (ie no leaks). Not sure what you guys would think on the couple options... Or if just welding it the same a stainless steel would suffice.

    Next question I have is on the propteries of Ti, from some research the melting temperture of Ti is 3200F while SS is 2500F, and the thermal expansion is of Ti is 8.5 while SS/steel is 17.4, if I were to use Ti in a high heat application, turbo downpipe, exhaust manifold, turbo manifold how do you think it would hold up to the heat cycling?

    In the case of building a Ti exhaust I know most exhausts systems (post cat) are .035, some full exhaust from a turbo downpipe or manifold are the same .035 wall thickness. If I were to build a turbo downpipe, turbo manifold, or N/A exhaust manifold what thickness would you suggest/recommend?

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    • #17
      You have lots of good advice on welding titanium but I would like to offer a few suggestions from my own experience on building a purge chamber. Once you have it all sealed up I found the most important thing was a decent one way valve. Once you start moving your arms around inside the chamber the gloves work like bellows and if you don't have a good one way valve everytime you pull your arms out you're sucking air back into the chamber contaminating your environment.
      I found the best one way valve was to cut up a 3M half mask and use the port that is used for exhailing. I built a little enclosure and siliconed it in to seal it. I've attached a couple pics so that you may see how it was done.
      I've built a few chambers, this was the first one to work out any bugs, the next was a 60" diameter one to accomodate a large aerospace part that we weld. I use a cold wire feed system from Arc Zone to feed wire, I changed it to use a foot pedal to activate it and it is all sealed from the wire feeder to the chamber using a mig gun cable and liner.
      Regards
      Jim
      Attached Files

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      • #18
        Aircraft welding

        Originally posted by FullFusion View Post
        You have lots of good advice on welding titanium but I would like to offer a few suggestions from my own experience on building a purge chamber. Once you have it all sealed up I found the most important thing was a decent one way valve. Once you start moving your arms around inside the chamber the gloves work like bellows and if you don't have a good one way valve everytime you pull your arms out you're sucking air back into the chamber contaminating your environment.
        I found the best one way valve was to cut up a 3M half mask and use the port that is used for exhailing. I built a little enclosure and siliconed it in to seal it. I've attached a couple pics so that you may see how it was done.
        I've built a few chambers, this was the first one to work out any bugs, the next was a 60" diameter one to accomodate a large aerospace part that we weld. I use a cold wire feed system from Arc Zone to feed wire, I changed it to use a foot pedal to activate it and it is all sealed from the wire feeder to the chamber using a mig gun cable and liner.
        Regards
        Jim
        I'm just learning tig welding & on aircraft parts. I work in the aircraft industry and know the level of quality it must be done at. The cabinet you show looks great, could you tell me other than the argon supply, a connection for evacuating the cabinet, the tig torch connection what other connections to the cabinet do I need? Also after pulling a vacuum and introducing argon can I just vent the cabinet at the top based upon argon being heavier than normal air? thank you

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        • #19
          I don't use any vacuum at all, as you mentioned I depend on the difference in weights between the gases, so the purge vent is located at the top of the cabinet. I use an oxygen sensor from Huntingdon Fusion to verify the environment prior to welding, for this chamber it takes approximately 20 minutes to reach .002% oxygen. This is with the flow meter set at 40cfh.
          I'll take more detailed pics if you're interested in making one yourself, it's not costly and works quite well. For the torch entry it's a simple rubber stopper (3" diameter I believe) with holes drilled for the 3 lines and cut and split to allow insertion and then sealed with silicon. The rubber stopper fits into a piece of 3"ss tube snugly that's welded to the cabinet. I have all the part numbers for pieces used, the only piece that requires machining is the connection for the mig gun cable to the cabinet if you are using a wire feed system.
          Regards
          Jim

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          • #20
            pictures

            Originally posted by FullFusion View Post
            I don't use any vacuum at all, as you mentioned I depend on the difference in weights between the gases, so the purge vent is located at the top of the cabinet. I use an oxygen sensor from Huntingdon Fusion to verify the environment prior to welding, for this chamber it takes approximately 20 minutes to reach .002% oxygen. This is with the flow meter set at 40cfh.
            I'll take more detailed pics if you're interested in making one yourself, it's not costly and works quite well. For the torch entry it's a simple rubber stopper (3" diameter I believe) with holes drilled for the 3 lines and cut and split to allow insertion and then sealed with silicon. The rubber stopper fits into a piece of 3"ss tube snugly that's welded to the cabinet. I have all the part numbers for pieces used, the only piece that requires machining is the connection for the mig gun cable to the cabinet if you are using a wire feed system.
            Regards
            Jim
            Yes if you don't mind more pictures. Also is the oxygen sensor mandatory or could I use a time factor (time at which the argon is allowed to flow into the cabinet)? thanks again

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            • #21
              I'll take some pics and start a seperate thread on the purge chamber, I don't want to hi jack this one. An oxygen sensor is not necesessary, a strike test coupon to run a bead on to verify that it stays silver during welding is just as good, you just tend to wait longer then necessary at times waiting for the purge.
              Regards
              Jim

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              • #22
                Originally posted by Burnt hands View Post
                Hi Dave reynolds,

                Thanks for the great tidbit of information in your post.
                I too have noticed that my wire would tend to "stick" to the weld pool on occasion when tigging titanium and I figured it was something I was doing wrong. I have not had the same problem with stainless so I thought it was me. Thanks for the help.

                And to everyone, if you look at my welds, they may be pretty with the "rainbow" effect but strictly speaking they would fail the AWS standards.

                I make titanium sculptures but would never attempt to do any aircraft quality welds as this is way beyond my expertise.

                I do not have a weld chamber so I made a poor substitute out of plexiglas. Looks like a glass bead box or the baby incubators for premature babies.

                I have learned the hard way that argon is a lot cheaper that titanium.

                The more I learn, the more I strive to make my welds better and I'm sure this is why everyone is here also.

                thanks,
                I held a Ti ticket a few years back and it's not extremely hard to weld but very easily contaminated. We used purging shoes with a guy under air in the pipe following me around with the trailing shoe. I had a big (#20 i think gas lense) with a trailing shield. Anything other than a mirror finish on the weld and a slight straw color in the heat affected zone were a failure. This line had wet chlorine gas running through it. If the moisture content went to low they said it would spontainiously combust and the only way to fight the fire would be to run out of one or the other. If you are planning on welding Ti make dam sure you store your filings and grinding dust in oil otherwise they will spontainiously combust and it burns white hot. DO YOUR REASEARCH before you do anything with Ti. Jef

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                • #23
                  Jim, thanks for the pics on the chamber, when you start your thread please post a link in mine.

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                  • #24
                    More info on Titanium

                    Like many of the others have said, Titanium is not really hard to weld, but is embrittled by oxidation. If you get anything but a light straw color (yellow tint) on your welds you may have to check for gas leaks. Also keep in mind that with TIG welding sometimes lower gas flows work better, so you may need to work to get your shielding gas flow rates set just right. Want to use the largest gas cup that you can so keep as much of the material shielded as you weld.

                    Also, if you are welding tubing, make sure that you purge the inside. A rule of thumb for purge time is 6 volume changes of gas before the start of welding. That means that if you look at a pipe that has a volume of 10 cubic feet, that at a flow rate of 10 cubic feet/ min that you would need to purge that pipe for at least 6 minutes before you start welding.

                    Make sure that the flow rates for purging are kept relatively low and that there is no pressure buildup inside the pipes. If there is pressure buildup in side the pipes it can cause suck-back on the root of the weld and concavity on the inside of the pipe or tube.

                    Since argon is heavier than air, it is a good idea to use a vent opening that is on the top of the pipe or tube. This way the argon will push out any other gases and keep the tube purged well.

                    Purging doesnt need to be really exotic and can be as simple as taping a gas hose to one end of the pipe or tube, with the other end taped with a small vent hole. The vent hole doesnt need to be really large, just enough to allow some gas to escape to prevent pressure buildup.

                    If you get into welding titanium you may find that the material is very fluid, especially compared to stainless steels. If your machine has the ability to pulse the current that may work well for welding titanium. Its very expensive, but is really a nice material to weld.

                    Make sure that you clean all of your filler metal before welding. A good solvent wipe might be a good idea to get rid of any foreign material.

                    Comment


                    • #25
                      Originally posted by FullFusion View Post
                      You have lots of good advice on welding titanium but I would like to offer a few suggestions from my own experience on building a purge chamber. Once you have it all sealed up I found the most important thing was a decent one way valve. Once you start moving your arms around inside the chamber the gloves work like bellows and if you don't have a good one way valve everytime you pull your arms out you're sucking air back into the chamber contaminating your environment.
                      I found the best one way valve was to cut up a 3M half mask and use the port that is used for exhailing. I built a little enclosure and siliconed it in to seal it. I've attached a couple pics so that you may see how it was done.
                      I've built a few chambers, this was the first one to work out any bugs, the next was a 60" diameter one to accomodate a large aerospace part that we weld. I use a cold wire feed system from Arc Zone to feed wire, I changed it to use a foot pedal to activate it and it is all sealed from the wire feeder to the chamber using a mig gun cable and liner.
                      Regards
                      Jim

                      I have a question on the the chamber, did you use glass, pelxi-glass, lexan, other? Pleas give me more details (materials list) on the chamber you built, I think the best route would be building my own chamber rather than modify a sandblasting cabinet.

                      Once you have the camber purged, do you still purge the chamber while welding, or does the purge hold using the check valve?




                      Anyone now were I could get a trailing cup, or details on building one? I ask because there are case were I will need to tack it up or weld it in place.

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                      • #26
                        Check this out, it may fit your needs:

                        http://www.hgrindustrialsurplus.com Search 21-519-062
                        Miller Syncrowave 200
                        Homemade Water Cooler
                        130XP MIG
                        Spectrum 375
                        60 year old Logan Lathe
                        Select Machine and Tool Mill
                        More stuff than I can keep track of..

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