a36 steel

huangyhg

a36 steel
can anyone shed some light on the following?
i have heard that when you specify a36 steel you typically get 50ksi and that a36 is now considered a special order.  is there any truth to this?  is a572 grade 50 a common replacement for a36?
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that is what we did but am not
certain why.  maybe the a572 was
more difinitive.  i think the
a36 had more allowable sulphur
in it.  we had some trouble with
welding because of it, and not
spec out the allowable sulphur
content.  you might want to post
this to the steel engineering
forum or welding forum.
in conversations i have had with steel suppliers a36 for wf sections and a lot of rolled sections are not being produced by some mills anymore.  (however lots of plates seem to still be a36.)  if you ever had any mill testing done on a36 it was coming close to fy=50ksi anyway.  
however i would not just assume that you are getting a572 grade 50 since some shops keep inventory and might have some old a36 lying around.  i also had a problem with a shop not carrying a572 grade 50 plates and needing to special order.  (or increasing plate thickness.)   
in my experience it seems some shops still give you or say
a36 on the shop drawings, however the bigger shops have gone to all a572 grade 50 for rolled sections.
grade a36 is becoming less and less common as grade 50 becomes more common and cheaper.
the critcial difference in steel today is the price difference between grade 50 and hps 70.  also note that there is a considerable difference in a588 grade 50w and hps 50w.  which seems illogical if the interest in only in the tensile strength and not hardness.
last month's structural engineer magazine article may shed some light.
most w shapes are now rolled from a992 steel. it is a 50 ksi yield , but with better chemistry for welding than a572. angles and channels are still being rolled from a36.
i understand that angles are predominantly available in a36 also...
i used to be the construction estimator/expeditor for a steel fabricator.  i currently am performing structural engineering for an architectural firm.
i contacted the primary supplier when i worked for the fabricator, and inquired what i should be specifying for rolled, wide-flange, structural steel if i want to use grade 50?  i was told to specify a992/grade 50.
my experience when purchasing for the fabricator was that there was absolutely no cost difference, to speak of, between grade 50 and a36.  (this is not to say that one should specify grade 50 exclusively.  my reason for stating this is that it has been brought to my attention that there are structural situations where we should not specify grade 50.  i cannot elaborate on this, as this is something i, also, need to research at this time.  i recommend the same.)
furthermore, i recall one project for which i had sold a36 steel, as specified.  the engineer had discovered later, when the wf steel columns had been already delivered to site, that the a36 spec should have been grade 50.  i requested mill tests from the steel supplier for those particular pieces.  fortunately, for the engineer, as craigory28 had suggested, the a36 test results came "close enough" to satisfy the imposed calculated load.  "close enough" was more specifically in the neighborhood or 46-48 ksi.  thus, never assume the a36 will be all of 50 ksi.
hope this helps ...
currently, for wide flange shapes the recommended astm specification is a992 gr 50. it meets all the chemistry and ductility requirements of a36 steel. a572 does not meet all of the requirements of a36.
hi folks,
astm standard a36 has no maximum limit for yield and tensile strength nor does a572 gr 50. indeed the actual yield strengths when you look at the mtr's are around 53 ksi yield, but i have test reports at over 80 ksi yield for a572 gr 50 shapes in the "k" region. a992 has set a maximum yield strength limit of 65 ksi for wide-flanges, which is a good thing, and have also established a ratio between yield strength to tensile strength. this is how columns are all triple certified these days.
hey, and what about the weld filler metal that we calculate at 70 ksi min uts, but comes in at 75 to 86 ksi yield and 84 to 97 ksi uts? what does that do to our moment frame connections? weld filler metal has no maximum limit either and aisc is talking about the suitability for overmatching weld filler in their new manual for steel detailing. fun!!!
koz
koz