Shelf-life on AKDQ Steel Tube ??? 3

[ornerynorsk]

Has anyone had extensive experience with AKDQ carbon steel tubing ~ I was wondering if this material age hardens or becomes less workable with time, IE: is there a "shelf-life? We have a vendor that started having problems doing a bend that we've been doing for years. No other variables except metallurgy. Same machinery, same dies, same setups, same operator, same material suppliers (except for lots and heats), etc etc. Certs do not show any inconsistencies with prior runs. Thanks.

 

[metengr]

ornerynorsk

We have a vendor that started having problems doing a bend that we've been doing for years. No other variables except metallurgy.

What kind of problems? Cracking or increased forces needed to make the bend or ovality?

 

[ornerynorsk]

Cracking through in the bend due to excessive thinning and/or brittle fracture. 1-1/2 OD x 16 Gauge @ 124 degrees bend. We're seeing material reduction to about 0.020 wall on the outside of the bend. This is a mandrel bend with wiper die. Roundness is excellent.

 

[ornerynorsk]

1-1/2 centerline radius. There, I think that's everything.

 

[metengr]

You might find this article enlightening

http://archive.metalformingmagazine.com/2005/05/Science.pdf

 

[EdStainless]

Either the lubricant or the mandrel are wrong. A slight error in mandrel position can be serious. If the tubes are very round then I am guessing that the mandrel is not retracting enough during the bend.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[ornerynorsk]

Thanks everyone. I appreciate the input.

 

[TVP]

on,

The answer to your question is no, Al-killed steels do not age harden, provided that there is sufficient Al. This is usually a minimum of 0.020 % by mass. Even at high N concentration (say > 0.015%) there should be no problem as long as there is a 3:1 ratio of Al to N.