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Up Topic Welding Industry / Inspection & Qualification / Bend radiuses for certain steels.
- - By Kix (****) Date 11-20-2007 13:47
In D1.1 2006 if gives you a list of bend radiuses for steels under 50ksi and over 50ksi as well as over 90ksi.  Anyway, my question is if i'm doing a bend test on a A572 gr-50 = 50ksi or 345 MPa welded with ER80S-d2 wire what bend radius should i use?  ER80S-D2 is rated in the as welded condition for 95,000 psi yield strength and with dilution will take the bend radius area well over 50ksi. So i'm wondering if i should go to a 2'' radius instead of the 1 1/2" radius.  How do you all aproach this situation?

Thanks, Ray C.
Parent - - By js55 (*****) Date 11-20-2007 14:26
To my knowledge D1.1 does not address that contingency. It specifically addresses "Specified or Minimum Base Metal Yield Strength".
So essentially your stuck with either a radius that is perhaps too stringent for your filler or you have to violate the code.
And I think it may even be worse than that. If you do transverse bends you're going to have a region at the fusion zone that takes the brunt of the bend since the filler is stronger than the base metal. Your elongation right at the fusion line just on the base metal side will most likely be greater than at any other point as the base metal stretches more to accomodate the resistance of the filler to achieve a 180.
I've never done that particular combination but you may have to go to longitudinal bends.
Parent - - By Kix (****) Date 11-20-2007 14:32
Well, the 2" bend radius ranges from 50ksi to 90ksi so i'm reading that I will still be legal with a 2" bend radius.  Do you agree?
Parent - - By js55 (*****) Date 11-20-2007 14:38
I agree that a 2" radius may be used with BM yields from >50ksi to 90ksi.
Parent - By js55 (*****) Date 11-20-2007 14:40
EH!!!!
Nix that!
Its a 2" diameter - Dimension A
As opposed to a 1" radius - Dimension B
Parent - - By swnorris (****) Date 11-20-2007 14:47 Edited 11-20-2007 14:51
The only thing I can think of, is typically, for undermatching weld metal, the weld metal controls the strength of a joint.  For matching weld metal, such as those in Table 3.1, the allowable load on both the weld and the base metal are the same.  For overmatching weld metal, the base metal is the controlling variable. 
Your situation of 80xx to A572 Grade 50 is not in Table 3.1 for filler metal matching strength, so to me, it would fall into the overmatching category, in which the base metal is the controlling variable.  That being said, I would think that you'd have to use the 1 1/2" for the "specified" 50 ksi and under, since the criteria for a bend test is based on either the specified base metal strength OR the actual base metal strength, which can be taken from the MTR.  However, the actual MTR yield value will most likely put the base metal into the 'over 50 ksi" criteria, which would then require the 2".  As far as I know, the bend test criteria is without regard for the weld metal strength.    
Parent - - By js55 (*****) Date 11-20-2007 14:53
Scott,
Let me ask though, if you use actuals from the MTR in order to boost the radius, how do you justify the possibility of using that PQR/WPS for materials that may not achieve the higher yield of that particualr heat and should therefore fall under the lesser radius?
Parent - - By swnorris (****) Date 11-20-2007 15:34
I assume that the original post is in regard to bending test coupons for welder qualifications.  As you know, there's always going to be a difference between the minimum specified yield value and the actual yield value of a base metals, but as long as they fall under ASTM A572 Grade 50 criteria, the base metal can't be anything more, or anything less.  So, to me, the justification would be that the base metal still falls under ASTM A572 Grade 50 criteria.
The thing that's not clear to me as far as the bend test is, when should the specified yield be used and when should the actual yield be used? It makes more sense to use the actual yield.
Parent - By js55 (*****) Date 11-20-2007 15:52
Scott,
Yeah, I was just assuming PQR quals.
As for taking advantage of the larger radii with greater yields, if materials governed by the then ligitimately established PQR do not demonstrate the higher yield, this seems to run counter to the intent of the code. Or simply, it appears to be taking advantage of a loophole.
Parent - - By MBSims (****) Date 11-20-2007 15:57
In the 2006 edition of D1.1, Figure 4.15 the column heading says "Specified or Actual Base Metal Yield Strength".  So, if you have actual "base metal" yield strengths over 50 ksi then it is acceptable to use the 1" bend radius specified for base metals "over 50 ksi to 90 ksi".  Since the bend radius is based on "base metal" yield strength and there is no mention of weld metal yield strength, I would say a 1" bend radius is permitted.
Parent - - By js55 (*****) Date 11-20-2007 16:09
Marty,
I think the 1" bend radius is permitted, but if the actual criteria is used, is that representative of the what then may be permitted in production? Since, per Table 3.1 base metals are qualed per Group numbers would not the larger radius PQR be able to be used on materials that a larger radius could not be justified?
Don't get me wrong, I do believe this is all acceptable under the code, but is it justifiable from and engineering standpoint?
Isn't it a loophole?
Parent - By MBSims (****) Date 11-20-2007 17:52 Edited 11-20-2007 18:01
Yes, it is justifiable.  The guided bend radii specified for different yield strength levels are intended to produce at least 20% strain in the outer radius of the specimen.  This is the same criteria regardless of the yield strength.  Obviously, it is not exact and has been broken up into 3 yield strength ranges that may have some overlap.
Parent - - By CWI555 (*****) Date 11-20-2007 17:03 Edited 11-20-2007 17:09
C-4.8.3.3 Acceptance Criteria for Bend Tests. The
new, more definitive wording for bend test acceptance
was added to aid the interpretation of the test results. The
purpose of the bend test is to prove the soundness of the
weld. The statement regarding the total quantity of indications
was added to restrict the accumulative amount of
discontinuities.

I believe the intent is clearly stated. If you have a higher strength weld metal, you test for that weld, not for the base metal.
Since you have unmatched strength, which is not directly addressed, I believe i'd be going to the larger radius rather than the smaller one. (assuming the 572 is a little above 50k which is usual.)
Parent - - By Kix (****) Date 11-20-2007 17:34 Edited 11-20-2007 17:49
Oh man i screwed up i put radius instead of diameter.  I meant a 1" radius for 50ksi to 90ksi and a 3/4" radius for 50ksi and below.  I'm sorry for the confusion!! (banging head on the keyboard).;-)
  IN the PQR the base metal and filler mentioned above pulled at 76,512 psi and 78,042psi.  Thats why i was wondering if you should go by this for the bend radius.  So if you were to use A500 gr-C (46ksi) and weld it with ER80S-D2 witch would bring the tensile test up over 50 ksi you would still go by just the base metal and use a 3/4" radius.  I'm getting what you guys are putting down.
Parent - By MBSims (****) Date 11-20-2007 18:27
Let's not get tensile and yield strength values mixed up here.  I assume 76,512 psi and 78,042 psi are the "tensile" test results for the PQR.  A500 Gr.C minimum yield strength is 46 ksi and min. tensile strength is 62 ksi.  ER80S-D2 minimum tensile strength is 80 ksi and the minimum yield strength is 60 ksi.  The ranges given in Figures 4.15, 4.16 and 4.17 of AWS D1.1 are solely based on base metal yield strength and weld metal yield strength is not addressed.
Parent - - By MBSims (****) Date 11-20-2007 17:54
I don't see any wording that implies the test should be based on the weld metal yield strength.  Perhaps you could elaborate a little more on that.
Parent - - By js55 (*****) Date 11-20-2007 18:08
And lets not forget that the HAZ is part of the evaluation of the weldment. If you go to a larger radius you are not testing the HAZ at the elongation intended by the code.
Though as I stated, with much greater strength fillers, you are probably overtesting the HAZ immediately adjacent to the fusion line.
Parent - - By MBSims (****) Date 11-20-2007 18:13
I agree.  If failures are observed in the side bends due to the strength mismatch, it would be better to switch to longitudinal bend specimens.  The drawback is the longer test coupon length required to get the required number of longitudinal specimens.  The wrap-around type benders handle the strength mismatch much better than the plunger-type.
Parent - By js55 (*****) Date 11-20-2007 18:48
Done that a few times have ya Marty. :>)
Parent - - By CWI555 (*****) Date 11-20-2007 19:00
The later part of your post is the concern. "overtesting the HAZ". for that reason, and the stated intent in the commentary, I'd be inclined to go to the larger radius.
My opinion for what it's worth.
Parent - - By js55 (*****) Date 11-20-2007 19:06
Gerald,
I don't necessarily oppose going to the larger radius. And of course the 'overtesting' phenomena would certainly factor in an engineering decision. My thought is to just make sure that any who might read or participate in this thread should be aware that even though the code allows this practice it should still be an engineering consideration.
I think this may be one of those threads that has the appearance of a disagreement when there really isn't one.
Parent - By CWI555 (*****) Date 11-20-2007 22:11
I agree with the engineering consideration, and the appearance of a disagreement when there is none.

Regards,
Gerald
Parent - - By CWI555 (*****) Date 11-20-2007 18:35
I am refering to the intent of the test. It's not the intent to test for base metal, but rather for the weld.
Parent - - By MBSims (****) Date 11-20-2007 19:19
I agree, bend tests are intended to demonstrate the soundness of the weld.  But, it is desired that the weld metal properties be at least as good as the base metal.  That's why the bend radius is based on base metal properties instead of weld metal. 
Parent - - By 803056 (*****) Date 11-20-2007 21:23
You could consider using AWS B2.1 as the basis of qualifying the WPS provided the EOR or Owner is agreeable.

The bending requirements in B2.1 may be easier to comply with only because it is written to cover more scenarios and possible base metal combinations.

I have steered my client toward B2.1 on those occasions where the materials being welded were not a match with the base metals or filler metals combinations listed in AWS D1.1.

I like the suggestion of using longitudinal bends for those situations where there is a mismatch between the base metals being joined or the filler metal - base metal combinations. Even with a wrap around fixture, I suggest longitudinal bend tests when there is a mismatch or if there is concern that the properties of the HAZ are different than either the weld or base metal.

Best regards - Al
Parent - - By Kix (****) Date 11-21-2007 14:25
This is not intended for WPS qual, but for Welder qual if this helps any.
Parent - By 803056 (*****) Date 11-21-2007 19:32
B2.1 can be used for welder qualification as well.

Al
Up Topic Welding Industry / Inspection & Qualification / Bend radiuses for certain steels.

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