determing grade of steel

[AlpineEngineer]

I have a client who has a steel beam he has had laying around for awhile that he wants to use in a project. Is there anyway to determine if its 30 or 50ksi steel? I couldn't find any stamping on it. Somebody told me that not to long ago everything was grade 30, is this true? I have always speced grade 50 but I'm a young buck.. Maybe its just safe to assume it's grade 30??

 

[Lion06]

I would believe 36, not necessarily 30.

 

[jike]

I think that you are refering to A-36 (36,000 psi), but if it looks older than 40 years, I probably would assume A-7 (33,000 psi).

 

[DonPhillips]

Unless your calcs show you need 50 ksi steel, it would not be worth the hassle to find out the grade. If I remember correctly, A36 was common until the late 80's or so.

Don Phillips

http://worthingtonengineering.com

 

[FLCraneBuilder]

A-36 steel is still very common in hot roll plate, S beams and channels. I am told by the people at one of our Steel Service centers that gr 50 WF beams became prevelant in the late 90's.
I've seen an article on a hand held electrical device that claims to provide the grade of material. I have not tried it. Has anyone else?

 

[MotorVib]

A36 is still used in most industrial settings. I just finished a project that used 30 to 40 tons of A36.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[jike]

Alot of steel was used for a period of time that had dual certification (36 and 50).

 

[HgTX]

I've heard of a portable chemistry tester. You can use hardness as a very rough approximation of strength.

Hg

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[metengr]

Doee your client need the entire beam length or can a sample be strategically removed for chemistry and tensile tests by an independent lab? I would think this is the correct method to certify a beam for use. Hardness is limited to UTS approximation, not YS, and portable alloy analyzers cannot measure carbon, unless you have a portable arc emission spectrograph. Do it right.

 

[MiketheEngineer]

Just assume A36 and you will be safe unless the beam is like 100 years old

 

[jike]

If it is 50 years old, it would be A-7 (33 ksi). If it is 80 years old, it is A-9 (30 ksi). Over 100 years, it might be wrought iron.

 

[HgTX]

I'm not in favor of using scrap for structural purposes anyway...

Hg

Eng-Tips policies: faq731-376

 

[apsix]

....but who mentioned scrap?

 

[ronster]

In response to "A36 is still used in most industrial settings. I just finished a project that used 30 to 40 tons of A36."

You may have specified the W sections as A36 but if you look at the mill certs for the steel supplied then I'm pretty sure you will find it to be grade 50 steel.

 

[PEinc]

If the beam design is based on a maximum allowable deflection, the steel yield strength (36 ksi or 50 ksi) may not be critical. Deflection is based on the Moment of Inertia which is not a function of steel yield strength.

 

[HgTX]

But to know whether deflection or strength controls, you need to know the strength.

If it's been lying around long enough to be unidentifiable, it's scrap.

For the amount it might cost them to have proper testing conducted to determine the relevant properties, they might be able to instead buy a new beam (especially if they sell this one as...scrap).

Hg

Eng-Tips policies: faq731-376

 

[DRC1]

HgTx,
You must not work for a contractor. We reuse a lot of steel.

 

[HgTX]

Do you keep track of what your steel is? Or do you just guess and hope for the best?

Hg

Eng-Tips policies: faq731-376

 

[youngstructural]

Hg: Good question, if a little argumentative...

The first thing is to look at the size of beam (ie your plastic modulus and second moment of inertia) and determine what strength of steel it would need to be to handle the job... After that you can feel out whether or not the beam should be considered scrap as Hg suggests.

Humbly I offer the following: If you need 28ksi, use the beam, 33 ksi, probably still use the beam, 36ksi, maybe don't use the beam unless you know it is only a few decades old... Over 36ksi required steel strength = SCRAP.

*nods head to Hg & DonPhillips*

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[DRC1]

HgTX,

We have started getting H-Piles now in grade 50 and are marking those. Otherwise we assume 36 ksi. Salvaged steel, if it is fairly recent, drawings wwill show if it is gr 50 otherwise we assume A-36 or A-7, Depending on the ageof the structure. We are generally pretty conservative with stresses anyway on old material.