Discussion debtate TIG welding 6061 and 7005 (together)

[ggodwin]

I was discussing materials with another bicyle frame fabricator. He told me that has welded 6061 and 7005 tubes together in the past. I told him that I didn't think it was a good idea. However, I couldnt give him a good reason. All i could give him was that I did'nt think the puddle would bond/blend so well and it may not be as strong.

I went home and didn't have any problems getting them to weld. Actually, after doing a couple beads I really couln't tell any difference.

What are your thoughts and comments?

Thank you

[ja baudin]

The two alloys are easily welded together using common 5356 alloy filler, 4043 not so much.. Check out AlocTec Wire Corp. www.alcotec.com and reference the Aluminum Filler Alloy Chart. It will show you which filler alloy is best for any combo of materials.

JA

[Hobart Aluminum]

Here is a snippet from the Hobart Aluminum Filler Metal Selection Chart which is located here:

http://www.hobartbrothers.com/downloads/aluminum_selecti_TtqVG.pdf

You can see that 5356 is a good option based on the criteria in the chart. 5356 and 4043 are the two most common alloys and the only place where 4043 out performs 5356 is in an elevated temperature service (above 150F) application. If high temp service was important 5554 would be the better choice.

In most welding scenarios where the base metal is thicker and the fillet weld is appropriately sized the weld typically fails through the throat of the weld. Since the tubing on bicycle frames is relatively thin the fillet welds are usually larger than normal proportional to the base metal. This usually results a failure in the HAZ rather than the weld metal (providing the correct filler metal was used).

7005 is an aluminum-zinc-magnesium alloy with no copper added and is considered weldable by most arc welding processes. Other 7XXX series alloys are not considered arc weldable such as 7075, 7178, 7050, and 7150.

From the Hobart Guide for Aluminum Welding:

"These types of base metals can be susceptible to stress corrosion cracking and premature failure if arc welded. In the heat affected zone of the non-weldable 2xxx and 7xxx series alloys, low melting point elements are preferentially precipitated into the grain boundaries which lowers and widens the solidification temperature range of the grain boundary. Consequently, when arc welding these types of base metals, the grain boundaries become the last to solidify and can easily crack due to solidification shrinkage stresses. In addition, the difference in galvanic potential between the grain boundaries and the remainder of the grain structure in these alloys is increased, making them more susceptible to stress corrosion cracking. These base metals are typically mechanically fastened rather than arc welded."

Due to the low copper content in 7005 it is readily welded to itself and to 6061 as well as many other alloy.

Hope this helps.

[H80N]

From the Hobart Guide for Aluminum Welding:

"These types of base metals can be susceptible to stress corrosion cracking and premature failure if arc welded. In the heat affected zone of the non-weldable 2xxx and 7xxx series alloys, low melting point elements are preferentially precipitated into the grain boundaries which lowers and widens the solidification temperature range of the grain boundary. Consequently, when arc welding these types of base metals, the grain boundaries become the last to solidify and can easily crack due to solidification shrinkage stresses. In addition, the difference in galvanic potential between the grain boundaries and the remainder of the grain structure in these alloys is increased, making them more susceptible to stress corrosion cracking. These base metals are typically mechanically fastened rather than arc welded."

Due to the low copper content in 7005 it is readily welded to itself and to 6061 as well as many other alloy.

Hope this helps.

Thanks Galen....

For those that have not already downloaded the Hobart Guide for Aluminum Welding

Here is the link

http://maxal.com/files/QuickSiteImages/Maxal_Guide_for_Aluminum_Wldg_9-12_doc.pdf

[Ironken]

I stole your links.......always looking for reference materials. Thanks guys.

[H80N]

I stole your links.......always looking for reference materials. Thanks guys.

That is exactly why we post them................

[coxey2]

Well here is a prime example of why this profession should demand a premium wage. Here is westerm KY employers are offering and getting people to weld these materials; and with the 10-12/hr wage (with 90 day probation) the employer gets the free knowledge that comes with the new employee. Similar to what we read here on this forum.

[ryanjones2150]

That doesn't sound free.