Weldin and corrosion of AW7003

[JB2001]

Hi!
I have heard that welding of the aluminium alloy AW7003 could give corrosion problems. The person that stated this could not however specify which type of corrosion problem welding could lead to. Does anyone know?
I know that the 7xxx generally is said to be prone to stress corrosion cracking. Is this of some reason worse in welded AW7003 or is there any other mechanism that could be suspected?

 

[metengr]

I don’t have specifics on A7003. However, for any of the 7XXX series aluminum alloys they are heat treatable, and in general, are not recommended for welding. From the information I have, the 7XXX series (both Al-Zn-Mg and the Al-Zn-Mg-Cu) alloys are prone to stress corrosion cracking and hot cracking problems in the weld joints.

For AW7003, I would be more concerned about cracks in the weld joint and reduced mechanical properties.

 

[weldtek]

For more info try this site;

http://www.alcotec.com

They have a page on 7000 series aluminum, explaining why you don't want to attempt welding it.

 

[JB2001]

Thanks for the suggestion, but I have been to Alcotecs site and I can not find the page you are referring to. Can you please guide me more precisely how to reach the page? The only information I find at Alcotec's site about the 7000 series is the same as also is stated at Lincolns site, which is that the majority of the 7000 alloys are as you say considered not weldable, but that there are a few exceptions from that, e.g. 7003(Lincoln) and 7005.

 

[metengr]

Excerpt from AlcoTec web site, from the page Understanding the Alloys of Aluminum

"7XXX Series Alloys – (heat treatable – with ultimate tensile strength of 32 to 88 ksi) These are the aluminum / zinc alloys (zinc additions ranging from 0.8 to 12.0%) and comprise some of the highest strength aluminum alloys. These alloys are often used in high performance applications such as aircraft, aerospace, and competitive sporting equipment. Like the 2xxx series of alloys, this series incorporates alloys which are considered unsuitable candidates for arc welding, and others, which are often arc welded successfully. The commonly welded alloys in this series, such as 7005, are predominantly welded with the 5xxx series filler alloys."

As stated above, several of these 7XXX series may indeed be welded without hot cracks in the weld deposit, but you will degrade base metal mechanical properties without re-heat treatment. If you need more information, contact AlcoTec directly.