Max Welding Heat Input For Aluminum

[tc7]

Can anyone suggest a maximum recommended welding heat input, in terms of kiloJoules per inch (or per cm), for aluminum in 5000 and 6000 series alloys such that we will minimize changes in chemistry or increased susceptibility to cracking or potential for stress corrosion.

Purpose is to back into welding variables (volts,amps, travel speed) from the recommended max heat input value and then proceed into a procedure qualification. Typical application will be for "as-welded" condition.

Thanks for any guidance offered.

 

[metengr]

tc7;
I would give these folks a call or email directly, they are most helpful.

http://www.alcotec.com/

 

[civilperson]

American Welding Society, "D1.2 Structural Welding Code Aluminum"

 

[GRoberts]

I don't think you will see a recommended maximum heat input for particular types of aluminum, as the real variable that affects the strength is the cooling rate. So that depends on other things besides the heat input, such as preheat, material thickness, welding process, etc. Regardless of the heat input or cooling rate, it won't affect the chemistry. The heat affects the cold working or heat treatment applied to the base metal before working, and anneals, or over-ages certain regions of the HAZ, but the chemistry will remain the same. Also, cracking in Aluminum is normally related to the chemical composition of the weld (filler plus base metal dilution) or the HAZ in the base metal, so heat input won't affect it other than it can affect the dilution and bead shape, some of which are more susceptable than others.

Anyhow, if you have enough specifics for aluminum experts like Alcotec, they might be able to provide you with some general guidelines or good practices, but I think you would be hard pressed to find any "rules".

 

[tc7]

I am not worried about strength - the underlying point of my question is that I can weld two aluminum plates together, pass all tensiles and bends and be fully qualified by the Code/specication that we may be working to. But is it also possible that in so joining these two plates that excessive heat may have been applied and increase the susceptability for interganular corrosion or stress corrosion?

I've posed my question to Alcotech before I posted here on Eng-Tips but have not heard back from them.

 

[weldtek]

tc7,
The problem with your question is that it is somewhat vague. In most cases, aluminum is pretty forgving, but, you don't specify grade, heat treated condition, thickness, etc. I think you'd be best contacting the folks noted above. Have you tried calling the toll free #?