WWOED? IE: What would other engineers do?

[CELinOttawa]

If you have a material you know to be produced to both ASTM A307 Grade A (no Fy specified, Fu >= 60ksi) as well as SAE J429 Grade 2 (Fy >= 57ksi, Fu >= 74ksi), would you be comfortable using the Fy = 57 ksi for the purpose of structural design?

It is really bothering me, and I want other Engineers' opinions on whether or not that would be acceptable practice. Sorry for the double thread, but I really want to know your opinions.

 

[jayrod12]

Yes, only because to meet the SAE standard it must be minimum 57ksi

 

[SlideRuleEra]

I would use the internet to gather more information before making an assumption on yield strength:

Note that Portland Bolt has SAE J429 Grade 2 with a yield strength of 57 ksi for diameters of 3/4", or less. For diameters over 3/4", yield strength is 36 ksi. You did not mention the diameter being considered. Typical applications of SAE J429 are listed as automotive and related industrial (no mention of structural use).

From Atlanta Rod there once was a Grade C of ASTM 307 (now superseded by another spec). Tensile strength is shown as 58 to 80 ksi, yield strength is 36 ksi. ASTM 307 is commonly used for structural purposes.

Based on this (circumstantial) information I would assume a yield strength of 36 ksi.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[CELinOttawa]

The bars is a stem bolt, or all threaded rod, and 5/8" dia. As to the lower Fy of 36 ksi, A307 C hasn't been produced in years, and was pulled from the spec in 2007. A307 B is a specialised product which is more expensive. This will be Grade A.

I know the product, and I know it to be cograded A307 A and SAE J429 Gr 2. The question is whether you would rely on the Fy = 57ksi when you know it is present, but comes from the automotive side of the cograding.

 

[racookpe1978]

So, test it.

But the result is good for only that run of that particular heat cycle for that particular mill.

Why do you want to save a few pennies of material cost by jury-rigging a specification up higher than it could be? How do YOU guarantee ALL of the rest of the steel bought from anybody else is as good as 57K yield and not 36K yield? (Hell, for that matter, how can you assure yourself that ANY steel purchased from an unknown re-melted mill in China is even 36K yield? )

 

[P1ENG]

I don't get the debate. If SAE J429 is an accepted automotive standard and requires quality control, why not use the yield and ultimate strength? There is more to a standard than material strength so I wouldn't expect both standards to list the same strengths. There is also composition (corrosion resistance), dimensions, testing methods, etc. I would also assume fatigue (cyclical loading) would play a major role in automotive standards, but if in doubt don't use it if fatigue needs to be considered.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[wannabeSE]

As a general rule, I would not specify something that needs to be dual-certified. If for some reason dual-certification is the best (or only) option, the requirements need to be clearly stated on the drawings. EG: 5/8" threaded rod, dual certified ASTM A307 Gr A/ SAE J429 Gr 2, Fy = 57 ksi min. If it needs to welded, then I would consider adding a note about low hydrogen welding rod. I'd also require the material certificates be submitted (with special inspection of certs) similar to high strength bolts and anchor rods.

My preference would be another material like ASTM F1554 Gr. 55 if it is available in the length needed. There are other materials that might work like A572, except don't think this specification covers the thread dimensions, so the pedantic may want to specify the appropriate standard for the threads. Another choice might be A193 gr B7 except the standard may not include a minimum yield strength.

 

[Lomarandil]

A193 does specify minimum yield strengths.

It's an unusual situation, and I'd take the extra steps required to make sure the client understands what he needs to procure -- but that said, once you have it, I'm certainly comfortable with using the higher of the two minimum strengths.

We have this happen all the time with Korean or Japanese fabrication -- material dual certified to ASTM and JIS specs. Sometimes it turns out to be really handy to have an extra 10ksi of capacity in the back pocket, when the client changes something down the road.