You are just concentrating on mechanicals I think. An ASTM specification contains a whole host of specifications other than the mechanicals. Chemistry for example:
C 0.26, Cu 0.2, Mn 0.8 - 1.2, Si 0.40, P 0.04 max, S 0.05 max for A36, C 0.23, Mn 1.35, Si 0.4, V 0.01-0.05, Cb 0.005-0.05, P 0.04, S 0.05 for A572 gr 50. Some specs specify the furnace method, some specify the heat treat. Some specs stipulate that the material shall be UT'd. Some specify hot roll, some cold roll, ect., ect. There is dual certified material, usually made by dropping the max chemistry of the more highly alloyed material into the range of the less alloyed. Here for example the mill would have to drop the 1.35 max Mn of A572 to below the 1.2 max of A36. You might pull your A572 MTR's and see if it *can* be dual certified. The long and short of it is that one specification is not the same as another and its beyond the kin of the CWI to decide what's acceptable as a substitution, that's an engineering decision. You customer's engineering staff specified A36 for what ever reasons, good or poor, and your company said (contracted) they would supply fabrications of that material, not A572. Making engineering decisions or changing the terms of the contract are both beyond the scope of a CWI's responsibilities. As for making a statement on the MTR, the A572 most definitely does not meet the requirements of A36 unless the melt chemistry was adjusted to make the material capable of being dual certified. If it can be dual certified, contact your vendor and ask them to have the mill supply a MTR stating the dual certification.
The mill, and only the mill, certifies that the material meets ASTM whatever. You don't, and your CWI stamp (Certified WELDING inspector) doesn't give you that power either. Your job as an inspector is yes it meets the contract, no it doesn't meet the contract. Technically, if the contract calls for A 36 and you have A 572, the contract requirement is not met. (The print doesn't give the physicals, chemicals, steelmaking process, etc.; it says ASTM A 36.) Your job is not to decide what can be done in case the material does not meet the contract requirements, no matter how obvious the solution may be.
The "engineer" (whoever that is on your particular project) has the right to override contract provisions, based on sound technical reasoning. The inspector does not, though the inspector can certainly offer information and opinions to help the engineer produce the sound technical reasoning. Deciding that the A 572 Gr.50 material is satisfactory on the basis of the MTR showing that all the requirements of A 36 are met is an engineering decision. However, even the engineer can't just declare the material to *be* A 36, only equivalent to A 36. No one but the mill can *certify* the material to meet a particular ASTM spec.
Hg
Strongarc,
The yield and tensile properties for A36 are 36 ksi and 58-80 ksi. The yield and tensile properties for A572 grade 50 are 50 ksi and 65 ksi.... so the mechanical properties for A572 grade 50 meets and/or exceeds that of A36. Solid documentation of this can be supplied to the EOR with a copy of each ASTM standard, though, I can't believe an EOR wouldn't already know this. To me, this is absolutely ridiculous for anyone with any common sense at all to reject this material. The bottom line is that the EOR would still have to approve the substitution. The only issue that would be a problem is that if A572 grade 50 is used, and there is any shop or field welding to be done, low hydrogen electrodes would be required.
There's always the possiblity that the client was counting on the max 80 ksi of the A 36...but I'm guessing this particular client wasn't. (And strongarc's company orders the material to meet both.)
Lesson for strongarc's company, though--if you're going pay the premium to order material to meet both standards, you might as well have that reflected on the cert.
Hg
Strongarc,
Fabricator's purchasing agents and various other "amateaur engineers" are always wanting to substitute materials/consumables for their own convienience (ie. prices, stock on hand, familiarity with the product, etc.). There is no MAGIC STEEL that does it all. Just because a given material meets or exceeds another in one or more categories does not necessasarily make it superior or even an acceptable substitute. If so, there would only be a couple of different alloys available from the Mills. Cast Iron xcells in vibration dampening applications, but to view it only from it's ductility, A36 is far better choice right?
Be careful of those who would assign responsibilities beyond your paygrade concerning the CWI stamp. Many times we are asked to make judgement calls for engineers, erectors and other disciplines. QC and CWI's have very limited responsibilities and one must be extremely careful to not cross boundaries.
swnorris brought up an xlnt point on the lo-hi requirement.
Engineers have an advantage over the rest of us mere mortals...we make mistakes, they make revisions!!! Take full advantage of their status!
Thanks guys! I appreciate the comments, keepem coming. Everyone here seems to definitely agree that a CWI does not have the authority to recertify the ASTM A572 Grade 50 material. Would everyone also agree that a CWI couldn't sign and stamp the mill cert stating that the material meets the mechanical and chemical specs of ASTM A36? How can I get a 100% actual answer to this to make sure that it's not just an opinion?
Thanks
Justin
The way I have dealt with this type of issue is to get an engineering ruling for each instance. Sometimes an engineer calls out a specific material for a reason; other times the requirement is there because that's what the engineer figured would work well enough without having to do a bunch of research(unfortunately, no, I am not kidding about my experiences here). I would never go out on a limb and say that 572 is equal to or better than 36; obviously they have some different properties which may make one more suitable than the other. However for me to say, as an inspector, that the 572 is acceptable in lieu of the 36 would be overstepping the limits of my authority. Get it written up as a deviation request and get the customer's engineer to sign it off. My $.02
Justin,
Your asking for trouble getting involved in this, and appear to be missing the forrest due to looking at a single tree.
The 100 percent answer is for the mill to provide you appropriate documentation. You can throw all the what ifs and buts you wish into it, that will not change.
The 80 percent answer is to get the client to buy off as is, but I doubt they would be willing to take that risk given the potential black eye they could get if something failed.
Strongly suggest you give up any other idea, and pursue one of those two options.
If the client has a clue, they'll buy off on it. If they weren't counting on the upper limit on strength for A 36, then A 572 Gr. 50 meets all the requirements of A 36.
If the client *doesn't* have a clue, then they probably won't be able to buy off on it, unless you present them with the data and they do have enough of a clue to evaluate it.
The inspector can help with the decision by presenting the data in an easy-to-understand format--for example, a table (or set of tables) showing the A 36 requirements, the A 572 Gr. 50 requirements, and the MTR results, with a copy of the ASTM standards so that they can verify for themselves that you didn't leave any requirements out. But there is nothing you can sign to make any of this legal. Only the client/EOR--or the mill--can do that.
Hg
Justin,
You need to listen to the previous two posts. They are your 100% answer.
We have an engineer that we hire at times like this to help pursuad others that there thinking is off track. It shows that an indepent third party can give another opion. Remember, if the material "meets or exceeds" the required" minimum requirement. Use that as your defense.
The only issue that would be a problem is that if A572 grade 50 is used, and there is any shop or field welding to be done, low hydrogen electrodes would be required.
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This is the point. If previous parts were made from A36, and future parts are to be made from A36 ther will be THIS BATCH that require a different weld specification [Low Hi] from all the others if modification or repair needs to be done down the road. While this isn't a problem for whoever fabricated the parts in the first place, it will be for the customer & end user.
What's the thickness of the A 36? If over 3/4", it's in the same group in D1.1 as the A 572 Gr. 50.
Just an update for everyone, our company ended up submitting engineering deviations for all the sample parts that were on hold because of the material issue. They approved all of the one-time deviations until our new dual certified material starts hitting the floor.
Thanks for the help guys.
Justin
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