Terry Keeley
Titanium
- Joined
- Oct 18, 2005
- Location
- Toronto, Canada eh!
I see 6Al4V is OK to laser weld but can small gaps be bridged? I have a part with a hole drilled in it that broke through the surface, tried JB weld but it didn't hold.
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Gap fill laser weld in Ti?
- Thread starter Terry Keeley
- Start date
- Replies 7
- Views 1,079
mhajicek
Diamond
- Joined
- May 11, 2017
- Location
- Maple Grove, MN, USA
With filler wire of the same alloy it might be ok, depending on your requirements. I'd start the part over.
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Good morning Terry Keeley:
I laser weld a lot of titanium in my shop, and here's what I've found.
First thing to know is that there are two kinds of laser welders out there...the most common uses a burst of energy repeated very quickly and makes discrete spots that you overlap to make your weld.
The second is "continuous wave", which functions exactly like the name implies and works much like a TIG torch
Moving on to your question...it depends on what you are calling a "small" gap
I try to aim for a very good joint fitup...0.001" gap or better.
The reason is that with my pulsed machine, the pulse duration is so short (milliseconds) if I have a significant gap, the puddle never has time to coalesce into one and I get two melt puddles, one on either side of the joint gap.
Continuous wave lasers don't do this...there is no pulse, so the beam is on all the time and you can hit the same spot for long enough to let the metal flow into one melt pool, and then just feed in filler wire...just like with TIG.
As you can imagine, with a beam diameter that only goes up to 0.020" wide, any kind of significant hole is a nightmare to plug weld with a pulsed laser of the kind that are sold for jewelery making and dental lab work and fine assembly like medical devices.
You have to use filler wire to fill a gap, and for me a telephone-pole sized wire is 0.015" diameter.
The blob it will deposit from a single laser pulse is maybe 0.007" tall and 0.020" wide.
So a scar 10 mm long and 2 mm wide takes hours to bridge with filler wire alone.
That means a properly shaped patch to do it in any reasonable amount of time, and the patch has to fit super well, so it's not trivial to make.
In addition, specifically for titanium and its alloys, the exclusion of oxygen from the weld zone is critically important, so your argon coverage has to be very good, and cover both sides of the weld.
That means some sort of back purging setup which you also have to make and mount to the job, and plumb for argon.
As you can see, this is all getting very complicated, and makes laser welding look less and less attractive compared to TIG.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
I laser weld a lot of titanium in my shop, and here's what I've found.
First thing to know is that there are two kinds of laser welders out there...the most common uses a burst of energy repeated very quickly and makes discrete spots that you overlap to make your weld.
The second is "continuous wave", which functions exactly like the name implies and works much like a TIG torch
Moving on to your question...it depends on what you are calling a "small" gap
I try to aim for a very good joint fitup...0.001" gap or better.
The reason is that with my pulsed machine, the pulse duration is so short (milliseconds) if I have a significant gap, the puddle never has time to coalesce into one and I get two melt puddles, one on either side of the joint gap.
Continuous wave lasers don't do this...there is no pulse, so the beam is on all the time and you can hit the same spot for long enough to let the metal flow into one melt pool, and then just feed in filler wire...just like with TIG.
As you can imagine, with a beam diameter that only goes up to 0.020" wide, any kind of significant hole is a nightmare to plug weld with a pulsed laser of the kind that are sold for jewelery making and dental lab work and fine assembly like medical devices.
You have to use filler wire to fill a gap, and for me a telephone-pole sized wire is 0.015" diameter.
The blob it will deposit from a single laser pulse is maybe 0.007" tall and 0.020" wide.
So a scar 10 mm long and 2 mm wide takes hours to bridge with filler wire alone.
That means a properly shaped patch to do it in any reasonable amount of time, and the patch has to fit super well, so it's not trivial to make.
In addition, specifically for titanium and its alloys, the exclusion of oxygen from the weld zone is critically important, so your argon coverage has to be very good, and cover both sides of the weld.
That means some sort of back purging setup which you also have to make and mount to the job, and plumb for argon.
As you can see, this is all getting very complicated, and makes laser welding look less and less attractive compared to TIG.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
EmGo
Diamond
- Joined
- Apr 14, 2018
Tried various methods on some race car stuff, the only one that really worked was done in a vacuum.
Terry Keeley
Titanium
- Joined
- Oct 18, 2005
- Location
- Toronto, Canada eh!
Thanks for taking time to reply, figured if anyone knew you would.
I know I should really just scrap this part (I have others that are good) but was hoping to salvage it as a backup. Here's another pic with the JB weld removed, that's a 1/16" drill in the hole.
I think this shop has continuous wave machines as they are quite large and they do a lot of mold work. Even tho it's probably not worth their time and I might not even ask, the owner has been very good to me over the years with small cash jobs and I don't want to wear out my welcome.
Think of any other ideas about how to repair it?
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi again Terry:
If you don't need the hole to be round, and if you don't need it to be super strong, you can patch it with the laser welder just fine.
The way to do it is to mill a shallow pocket around the drill hole, mill up a patch that fits into the pocket and laser weld it in, then kiss the surface of the patch until it blends in.
Your cost is the time it takes to do all that...you get to decide if it's going to be less bother to just scrap your existing part and make a new one.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
If you don't need the hole to be round, and if you don't need it to be super strong, you can patch it with the laser welder just fine.
The way to do it is to mill a shallow pocket around the drill hole, mill up a patch that fits into the pocket and laser weld it in, then kiss the surface of the patch until it blends in.
Your cost is the time it takes to do all that...you get to decide if it's going to be less bother to just scrap your existing part and make a new one.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
Marcus is on the right track. Adding filler manually puts a lot of responsibility for the part on the one doing it. It’s best to have good machine set-up and weld autogenous. Shielding is critical when welding Ti but for one part it doesn’t have to be fancy like in a vacuum or glove box. A large TIG gas lens with the center hole plugged works just fine on this size of part. Mount the lens off axis from the laser beam. Another inexpensive method is to construct a clear plastic bag using double sided tape that encloses the laser weld head and part. Purge this with argon. Fine tune your shield strategy on some sample material before you weld the real item.
gary-sc
Aluminum
- Joined
- Aug 20, 2010
- Location
- Santa Cruz, CA USA
Have you though about a .065" or, a bit larger, Ti rod inserted in the existing hole and then weld up the outside?
