Structural Steel Slection
Structural Steel Slection
(OP)
I have a question for the forum! We are about to do a new project, and the question has come up, regarding the minimum temperature that A36 structural steel may be used. I have looked all through the AISC manual and found nothing. The only thing I have found was relative to fire protection and elevated temperatures.
The project we are about to start has a design temperature requirement of -20F. Does anyone know of a document or standard that recommends changing from A-36 material to some other materail?
The project we are about to start has a design temperature requirement of -20F. Does anyone know of a document or standard that recommends changing from A-36 material to some other materail?
RE: Structural Steel Slection
RE: Structural Steel Slection
I cannot refer you to a standard but can give you a few pointers in case you have to (and are indeed allowed to!) make up your own mind:
You surely need to be concerned about the ductile-to-brittle transition temperature of your steel (or, NDT - nil ductility transition). And, I would say it also depends on the application and your load specifics (impact and fatigue loading might pose a problem). Fracture toughness or impact energy vs temperature might be useful if you could lay your hands on it.
Using thinner sections are better from a fracture toughness point of view (not exceeding required stress levels).
I do not know the details of your project but I think there is a chance that your A-36 might just do the job. Probably more expensive but I do know that aluminium and stainless steel are better suited for cryogenic service.
Gert
RE: Structural Steel Slection
RE: Structural Steel Slection
Eurocode 3 for structural steel has an entire section dedicated to this problem. Variables to be considered are the test temperature of Charpy-V impact test for material, level of stress in concerned elements and operating reference temperature: the calculated value per code is the maximum thickness allowed for different materials under those conditions.
As an example a material with 275 MPa (40ksi) minimum yield in low thickness products, when loaded close to the allowable stress, will have a maximum design thickness of 25 mm for a reference temperature of -30°C when tested for a minimum impact energy of 27J at 20°C, and a maximum thickness of 55 mm if impact tested for the same energy at -20°C.
So there is no simple answer to your question: you should definitely find the applicable code.
prex
http://www.xcalcs.com
Online tools for structural design
RE: Structural Steel Slection
http://ww
About the cold weather requirement, no steel in the AISC manual is really suitable for use at -20F. May be best to get specific material recommendations. This may be one place to begin looking
http://www.crrel.usace.army.mil/
Here is general information on cold weather use of structural steel (near the bottom of the page)
http:
www.SlideRuleEra.net
RE: Structural Steel Slection
RE: Structural Steel Slection
Zone Lowest anticipated service temperature
1 0°F and above
2 Below 0° to -30°F
3 Below -30°F to -60°F
ASTM A 709 Gr. 36 is equivalent to A 36 with CVN testing, and A 709 Gr. 50S is equivalent to A 992. If you specify the CVN toughness requirements given in A 709 for Zone 3 or even 2, and also take a look at the AWS D1.5 Bridge Welding Code for their Zone 3 (or 2) requirements (if you're going to weld), you should be okay, or at least as okay as the bridge designers are.
Hg
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RE: Structural Steel Slection
For reallly realllly cold structures (e.g. vessels for holding liquid oxygen etc), steels with higher nickel content can be used - see the bottom of:
http://ww
RE: Structural Steel Slection
Hg
Eng-Tips policies: FAQ731-376