Aluminum Alloys 6061-T6 vs 6063-T6 2

[oengineer]

What is the preferred aluminum alloy to be used for handrails in a lift station? 6061-T6 or 6063-T6?

Comments/suggestions are appreciated.

 

[phamENG]

6061-T6 is stronger, but check availability. And don't forget to consider the weld affected zone!

 

[oengineer]

And don't forget to consider the weld affected zone!

Could you please elaborate on what you mean by this regarding aluminum handrails?

Is the highlighted portion in the image what you are referring to?

 

[NorthCivil]

make sure you specify your filler alloys properly too, and make sure you select a filler alloy thats available/common/useable for the fabricator.

i dont know what text you are refering to there. but check the shear stress capacity of your welds too, these will usually be under 100mpa depending on alloy.

 

[phamENG]

Yes, that's what I mean. Make sure you have a copy of the ADM. It has details on how the WAZ/HAZ works, where to consider it, and what the strength of the base metal is in the weld.

Pro tip - you can't weld the base of a typical aluminum guard rail if you use standard sizes. You need a cast base with a bolted/friction connection to the post.

 

[oengineer]

6061-T6 is stronger, but check availability.

If availability is an issue, is either one just as acceptable as the other? Would their be a major difference in quality during the use of the handrail?

 

[dvd]

A classic article on aluminum welding - "Common Mistakes Made in the Design of Aluminum Weldments" published by Lincoln Welding Foundation.

See attached

 

[Aesur]

6061-T6 and 6063-T6 are both common materials used structurally for building finishes. In my experience 6063-T6 is most common due to it's finish ability (holds up a bit better that most aluminum alloys). 6061-T6 is stronger, however once you consider the welds, they are fairly similar and very weak in bending at he welds, which will be your highest moments most likely for hand rails. It may be possible to gain strength by by re-tempering, I have heard of this for bending applications, but suspect it may work with welding as well. When designing with aluminum make sure to use the Aluminum Design Manual as it's not as easy as calculating steel shapes, lots more steps depending on the shape. If you have never done aluminum calculations, I suggest you find a reference or sample calculations.

 

[dvd]

Another point to make on aluminum - it has no endurance limit, i.e., it will fatigue with enough cycles, even at low stress levels.

 

[phamENG]

Aesur - yes, re-tempering will work on welded material. So if the OP is designing a mile or so of handrails, re-tempering a batch might make sense economically. If this is a small platform in a neighborhood pump station, no way.

Some suppliers limit their selection based on shape. Eastern Metal Supply, the shop one of my clients uses and also has a presence in Texas, stocks round tube in 6063. I have another client that keeps a storage rack full of 6061 round tube for industrial handrails. So it just depends. Talk to your client. (For my first client, it's not worth it to them - they'd have to either go get an account with another supplier, or buy one offs from smaller supply houses at inflated rates.)

I also suggest you take a look at the NAAMM manual if you've never used it before. Has some good recommendations on practical railing design.

 

[oengineer]

6063-T6 handrails were initially mentioned in the specification, but a contractor is trying to see if they can use 6061-T6 handrails instead.

Wondering if it would just be best to go with the 6063-T6 handrails as originally mentioned?

 

[phamENG]

Who wrote the spec for 6063?

 

[XR250]

Another point to make on aluminum - it has no endurance limit, i.e., it will fatigue with enough cycles, even at low stress levels

It does, but I can't imagine that being an issue for a guardrail. Millions of bike frames would disagree.

 

[dvd]

A fabricator that I worked with several years ago related the tale of aluminum weldments with fatigued welds arriving on a truck at their customer's location. The components were drawn down tightly for shipping and the flexing of the flatbed during a cross-country trip resulted in enough cycles to cause fatigue failure.

Handrails may not be stressed until bolted, or otherwise deformed during mounting, resulting in a higher stress state. Depending on location and industry, there are handrails that will see enough stress reversals to cause fatigue.

 

[oengineer]

Who wrote the spec for 6063?

Someone else, not sure.

 

[phamENG]

Well you should find out and find out why they spec'd that. Or talk to the EOR and find out what his/her thoughts are. I wouldn't have a problem with the substitution, but if selecting the material is somebody else's job, I wouldn't do it for them unless there were extenuating circumstances.

 

[XR250]

The components were drawn down tightly for shipping and the flexing of the flatbed during a cross-country trip resulted in enough cycles to cause fatigue failure.

Fair, but they may have been flexed to near yield stress. Most guardrails will never see even close to their design load.