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Up Topic Welding Industry / Technical Discussions / Normalize 4130 After Weld - Can We Do It This Way?
- - By tom cooper (**) Date 04-15-2007 16:30
We have a GTAW WPS and a SMAW WPS for 4130, both specifically identify it as applicable to "Normalized" material. Typical post weld stress relief is required (1100 deg F for 1-hour/inch thickness).

Material was mistakenly delivered in annealed condition and cut to size then turned over to us for weld/assembly.  QA stepped in and stopped production as they insisted we normalize the material first, then weld, then stress relieve.   

I claimed we could and should weld in as-received annealed condition then let the heat treaters normalize afterwards, actually saving time and money by avoiding sending  same materials to the heat treaters twice.   I lost the argument and we did it their way.

Question #1:  From a metallurgical point of view, why could we not weld annealed material then normalize?

Question #2:   QA could not explain why I couldn't do it my way other than to say " the WPS didn't allow it".   So upon reviewing the Codes (D1.1 and Sect IX)  concerning Essential Variables,   I assume my idea is prohibited from welding annealed then normalizing because the PWHT temperature to normalize is a bit higher than PWHT to stress relieve.  Is this about right or is there another reason?

Please advise and thanks,
Tom
Parent - By Joseph P. Kane (****) Date 04-15-2007 17:43
I agree that you should weld in the anealed condition first.  Your 1100 deg temperature is wrong for normalizing 4130, and the rate should not be 1100 deg f per hour per inch. 100 deg per hour per inch would be more like it.  Parts should be stress releived also.  D1.1 does not cover 4130 material, although I once had a 4340 job that was to be done in accordance with the welding rules in D1.1, other than the material rules.  Procedure qualification was performed using D2.2 as the guideline.
Parent - By MBSims (****) Date 04-15-2007 18:08
As far as welding, performing the weld on material in the annealed condition vs. normalized would not be a problem.  The initial heat treatment condition of the base metal when performing the weld is not a variable (essential or nonessential) of ASME IX.  But, if you want to normalize after welding instead of performing the 1100 F stress relief, then that change would not be permitted without requalifying the WPS.  Normalizing temperature is above the lower critical temperature and the 1100 F stress relief is below the lower critical temperature.  This change would require requalification by QW-407.1.  Metallurgically this would have been acceptable, but as far as complying with ASME IX would not be acceptable.  So, the QA folks were basically correct in not allowing the work to proceed in a manner different than specified in the WPS.
Parent - - By Fredspoppy (**) Date 04-16-2007 13:10
Technically, the materials should be qualified in the heat treat condition that will be seen in production.  Welding on annealed 4130 and normalizing afterward is, in no way, representative of what will be seen in production.  The recommended normalizing temperature for 4130 is 1600F, followed by air cool.  This is a true "heat treatment", causing microstructural change both upon heating/holding at 1600F and air cooling back to room temperature.  PWHT of a weldment in 4130 is done at a temperature below that which will cause microstructural changes.

Something, not mentioned, is the possible adverse affects on the weld metal selected, during the normalizing treatment.

In general, you can do almost anything in weld procedure qualification that you want, but the resulting WPS must then be written to duplicate, in production, exactly what was done in qualification, e.g., to do what you propose would require welding on annealed materials and then normalizing the entire weldment.  Not very practical, especially from a size, potential distortion viewpoint.
Parent - - By js55 (*****) Date 04-16-2007 14:33
In general, the reason as manufactured heat treament is not considered a variable, even by ASME Section III, is because the HAZ changes everything. And whether or not the unnaffected base metal is viable for the service intended is not a qualification issue.
However, it is certainly the responsible engineering thing to do to at least consider this issue.
With some alloys the as manufactured BM will influence the HAZ to a certain extent( as with precipitations and grain growth), with others it is irrelevent.
Parent - - By Fredspoppy (**) Date 04-16-2007 15:30
Although you are technically correct regarding as-manufactured heat treatment, of the base metal used for qualification, any heat treatment done as a part of the weld procedure qualification is clearly covered by ASME Section IX, essential and supplementary essential variables (407.1, .2 and .4).  407.1(3) specifically references our subject here.
Parent - - By js55 (*****) Date 04-16-2007 16:02
Fredspoppy,
I agree. As was mentioned the normalize could not take place after the weld without requal, as Marty mentioned. Regardless of what properties you would end up with. And this is for good reaosn since the HAZ and weld metal will be affected too. However, the as received normalize could simply be dropped from the WPS without requal. Per engineering approval for an alloy such as 4130.
Parent - By tom cooper (**) Date 04-16-2007 23:41
Hi Joe, Marty Fred and JS,
This was a valuable experience for me and I appreciate your knowledge and interest.
Best to all and regards,
Tom
Parent - - By GRoberts (***) Date 04-21-2007 04:55
js55,
While you make some valid points, there as some catches as well.  On a lot of materials, if the ASTM/ASME material specification calls for a particular heat treatment, and the material is not processed in that manner, then it is technically not the same material.  Also, sometimes different heat treatments will put the material into a different grade.  One example would be ASTM A487.  Grade 4 can be heat treated to grade 4A, 4B, 4C, 4D, all depending on the strength level obtained by the heat treatment.   I also believe that ASME Section VIII has some requriements as to weld qualification and having the base metal being in the same pre-weld heat treat condition, but it has been a while since I looked at it, and would probably be no help in finding it.
Parent - - By Joseph P. Kane (****) Date 04-21-2007 11:31
This is a really good point.  It makes me wonder how really thick parts, that were welded with perhaps 350 degree preheat for a week, while they are being welded, can still be considered tha same material.  The extended time at the 350 degree temperature constitutes "Artificial Aging".  So, in addition to the thermo-mechanical changes due to welding, there probably is a change due to the effect of prolonged preheat in the artificial aging range, or the combination of the two.  None of the prescribed welding procedure qualification tests require testing further out beyond the HAZ range where the prolonged temperature may have some effect on the base metal.  This has the effect of "Processing", and perhaps, it is "technically" and maybe "actually" not the same material any more.

I am involved with some ASTM A913 Gr 65 Quenched and Self Tempered Steel, that is being fabricated to AWS D 1.1 Structural Welding Code - Steel.  Unlike the D 1.5 Bridge Code, the D 1.1 Code has no maximum Interpass temperature limit.  The contractor is heating it up to temperatures above 600 to 700 degrees F., ( I've actually measured 975 degrees in one short length), so that he can make two or three SAW passes without going back to maintain the required 300 degree minimum interpass temperature. (The material is 5 inch thick W14X730 column flanges, joined longitudinally by SAW welding to three inch thick A572 Gr 65 "MOD" plate material. These are columns for the new Freedom Tower at the World Trade Center in NYC.)
Parent - By js55 (*****) Date 04-23-2007 14:38
Joe,
I would agree that this is a very important and often overlooked phenomena.
And we are actually talking about two different things. Heat treat in manufacture and heat treatments in fabrication. Some codes address heat treat in fabrication by requiring the qual represent a certain percentage of the PWHT, but "aging" effects are often overlooked, except for the applicability of X and J factor requirements.
But it doesn't even take precipitation of X/J factor elements to cause a change in material, as you say. Carbides will not only continue to precipitate they will often enlarge and even evolve through differing carbides in many alloys.
I think to have a full understanding of a materials response to these intermediate heat regimes you need material specific C curves. Although, as a guess, I think you will always violate the C curve for carbides with jumbo vessels simply becasue they are iin the heat regime for so long.
Parent - By js55 (*****) Date 04-23-2007 14:26
Greg,
No disagreement. I am actually surprised that more codes have not addressed this issue. It shouldn't be addressed in ASME IX, in my opinion because varying heat treats seldom reduce properties (in tensile andbend regimes)to below a common chemistry minimum. For example CS's will maintain a strength and ductility min regardless of whether they are hot rolled or normalized and tempered, or fine grain or large grained. These are issues to be dealt with in service, and therefore to be addressed in codes of construction or engineering specs.
Up Topic Welding Industry / Technical Discussions / Normalize 4130 After Weld - Can We Do It This Way?

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