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Up Topic Welding Industry / Technical Discussions / Titanium,cover gas vs controlled Envirnm
- - By hitronics Date 03-14-2003 14:18
Can anyone help me with my search ? My question is this, we currently weld Titanium in a Glove box environment using Helium and Argon mix ( 25% Helium/75% Argon ) for Implantable Medical Devices. We wanted to know if we can laser weld outside of the glove box using a cover gas ( what would be the cover gas necessary in this case ) ? What would be the difference if any, between welding in the glove box and the cover gas ? If there are any differences are they catastrophic ? Will we be in any way effecting the integrity of the Feedthru weld by converting over to using the cover gas ? Are there any Publishing’s or Procedures that you know of stating that it is possible to do one or the other without any effect on the weld ? Our main concern to consider the weld gasses ? Hopefully the strength/penetration, and leak testing of the weld will remain the same.
Parent - - By TimGary (****) Date 03-14-2003 16:19
Welding grade argon is generally employed for torch sheilding because arc stability is better than with helium. Argon-helium gas mixtures, however, do provide a higher voltage, hotter arc and greater penetration. No other gases (including argon-oxygen mixtures, niyrogen, and CO2) can be used. Therefore, you may use pure argon for fixture sheilding and the mix for your torch sheilding, if you wish to enjoy a cost savings, but it may just be more hassle supplying two separate bottles/gages/manifolds.
I can fax to you some very informative titanium welding data from Titanium Industries Inc, if you will e-mail or post your fax#.
Parent - - By hitronics Date 03-14-2003 16:25
Tim Thank you for your reply. My e-mail is my fax number is 908-979-1824. Thanks again.

However, do you know if I will get any embrittlement by using the cover gas ? Will I basically have the same weld ?
Parent - - By TimGary (****) Date 03-14-2003 17:29
You may use the cover gas and not result in embrittlement. However, this needs to be a very, very controlled situation. You will need to build special backing and trailing fixtures that fit the weldment configuration and allow the even spread of the sheilding gas while not pulling in any oxygen. You will need to test your setup at the beginning of every shift to ensure nothing has gone amiss. You will need to perform detailed visual inspections on the setup prior to welding and for coloration post welding. Additionally, you will need to perform hardness testing post welding and visual inspection to rule out embrittlement entirely.
What it all boils down to is that if your parts can be welded inside an enclosure, that simplifies the task. While welding outside of an enclosure is possible and performed every day, it is not very practical.
I've faxed the info I mentioned.
Let me know if you need any help with backing/trailing fixture design.
Parent - By hitronics Date 03-14-2003 18:31
Hello Tim, I received the cover page and the following pages with the number on the bottom 10, 11, 12, 13, 14, 15. Could you try sending the remaining pages again. Thank you. Jerry Rosario Fax # 908-979-1824 phone number 908-979-9100 Ext 367.

Parent - - By Lawrence (*****) Date 03-14-2003 17:58
My first question would be to ask; why the helium in the first place? Argon is suitable for shield and cover gas for manual or automated GTA joining of Titanium in or out of the glove box. As far as embrittlement goes; contamination will be the only cause. Both argon and helium are inert and with 100% coverage of weld puddle and trailing zone you will not experience embrittlement (assuming the work is clean.) As a secondary thought, too quick cooling is thought to be related to increased crystal size, some welders are alarmed by the visible grain boundaries, However this phenomena is not even addressed in AWS D 17.1 2001 Specification for fusion welding for Aerospace applications.

I guess if you have a laser laying around with nothing to do, it's a good move. But if not, it seems like a big investment for something your doing now adequately but could be enhanced by improved process control.

Here is a link to a consultant with whom I am well acquainted, an expert mettelurgist with experience in automation, process control and materials that I bet would have some specific Ideas for your application

Keep us posted on your very interesting dilemma

Parent - By hitronics Date 03-14-2003 18:33
Thank you Lawrence for your reply. I will try the link that you supplied.
Up Topic Welding Industry / Technical Discussions / Titanium,cover gas vs controlled Envirnm

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