Welding procedures - NACE MR01-75/API16A approved

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Hello All, a colleague of mine has a problem on his hands regarding the timely development and qualification of welding procedures. Firstly the materials that require welding are as follows:AISI4130 to API 5L X65 andAISI8630 to API 5L X65.The welds submerged metal arc tubular Butt welds 24"OD x 21"ID and need to be in compliance with API16A whilst also satisfying the requirements of NACE MR01-75 for Hardness. its is the post weld hardness that's causing us problems - being too hard and not complying with NACE limitation. Plus the post weld heat treatment has its limitations as certain parameters may be suitable for the AISI material to bring down the post weld hardness but this may in turn have a detrimental effect to the pipe API X65 material properties.Does anyone have/know of approved weld procedures for such materials & standards that they would be prepared to correspond further on? ideally UK based as our material is in the UK required for the Oil & Gas industry.Look forward to hearing from you.RegardsChris
Reply:Heck if I know. Linkedin Professional has groups that discuss exactly your question.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Good luck with that. Linkedin groups are infested with "professionals" that do not know their right from their left. Occasionally some great welding engineers like Gene Mathers may comment but they are rare and few.As far as your problem is concerned, where are you getting the high hardness? Weld metal or AISI side?Root or cap? Can you take advantage of the different values allowed for root and cap? Can you provide more info? Welding consumables used, heat input etc?X65 is thermomechanically treated so you are correct that PWHT in the temperatures required by 4130 and 8630 will lower its mechanical properties.I have not performed a PQR for these particular combinations so cannot give you a tried and tested solution but in other similar problems there are basically three solutions.1. Butter the 4130 or 8630 side, PWHT and then weld without PWHT.2. Find a temperature in between that gives you acceptable hardness and mechanical properties.3. Use a temper bead technique (usually performed on Q+T steels)
Reply:OK thanks I'll have a look.
Reply:Thanks Taz, the excess hardness is found throughout the whole HAZ both sides, for the weld metal I'd need to confirm. We have the welding institute (UK) looking at developing both procedures (buttering for the 8630) but fear it may take longer than the most conservative timelines. There is an allowance for hardness increase in the transition from root to cap as I understand it. I'll obtain more detail from my colleague and post. Another constraint we have right now is one of the 8630 material has been procured already and it is on the limit of hardness before welding. its about 245Vickers HV10. We're allowed 250 Vickers! That said we'll most likely replace the 8630 with 4130 and lower hardness values and hope this procedure comes to fruition...
Reply:If you have TWI working on the matter there is nothing more I can add. They have some of the best welding engineers.
Reply:Chris,I have some experience working with welding procedures for 4130 and other Cr-Mo steels. Disclaimer:  I am familiar with NACE requirements, but not with API16A. So I can't say for certain if my recommendations will meet all the requirements for the application.  I agree with Taz00's commendations, but will add a couple more things to consider.I think that your colleague's welding procedure will have the greatest chance of success if he tailors the pre-heat and inter-pass temperatures to suit the problem.  If I understand correctly from your first posting, the application is a weld on material 3" thick, joining Cr-Mo to API 5L grade X65.  Excessive hardness in one or both HAZs.  Cr-Mo steels have moderate to high hardenability and this effect is controlled by how quickly the HAZ cools during and after welding.  Increasing pre-heat and inter-pass temperatures retards cooling and allows more time for the material to transform from the brittle structures that initially form into softer, tougher microstructures.  In the welding I've done in the past, 4130 for the most part, pre-heat and interpass temperatures were in the vicinity of 500-650F.  The higher the pre-heat and interpass the better, generally speaking.Unfortunately, the slower cooling created by these high interpass temperatures will tend to degrade the properties of the X65 material; as Taz pointed out.  The high hardness in the 8630 base material may be a dealbreaker; but I agree that you may have better success with 4130.  I've not checked TTT curves, but my gut say the 4130 will have lower hardness to start and less hardenability than the 8630.  You mentioned buttering the 8630 as a possible remedy.  Sounds like a good avenue to explore to me...Temper beads on the weld cap will help reduce the hardness near the outer surface, but I believe you mentioned that the hardness is too high all the way through the joint.  In this situation, and on material as thick as this, I think you'll have to find another means to address the hardness.It's a bit of a wild experiment, but talk with your colleague and consultants about using induction heat  or resistance heat to provide the high pre-heating and interpass temperature control. I'm a fan of induction heating and Miller Electric makes equipment for just this sort of situation.  There may be other induction heating equipment companies in Europe that could also assist with the problem.  I suspect the ultimate solution to your problem will involve applying more heat to the Cr-Mo side of the joint and less to the API X65 side.  Resistance or Induction heating can do this.  Higher temps on the Cr-Mo side to slow the cooling and thereby reduce the rise in HAZ hardness, and lower temps on the X65 to minimize any degradation in the base metal properties.  THis combined with some adjustment of the PWHT time and temperature and I think you'll get where you need to be.All in all, I don't envy the position you and your colleague are in.  There are a lot of ways for this kind of work to go wrong; even if you develop the right recipe to do the work.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Folks, once again thanks for your inputs... having had result back from the test house, our optimised weld procedure has has failed again on hardness, this time on the 4130 side in the HAZ only. The highest reading was 314HV10 and as I understand it on average post weld hardness worsened this time round. But from what I'm now hearing is one of our Carbon equivalent is too high around 0.7 and we need to get it down to less than 0.67 as we've come across a company whom has an approved (API16A & NACE) 4130 to X65 procedure but the CE needs to be 0.67 or less. so we have two options at present, back the mills to see what forged tube can be produced...(cost and lead time) versus the generation of a suitable WPS - probably not quite so costly but long lead time... Rock and Hard place springs to mind.BTW DAB, I'm hoping the next procedure run will utilise Induction heating if we can get hold of it and people to operate in time.
Reply:thanks for the update Chris.  Your Carbon Equivalency problems are not surprising; and something that teams I've worked with in the past have worried about.  Not to be all doom and gloom, but this is something you really need to pay attention to looking into the future.  IF these parts you're working on will be reproduced in future jobs, or if the set you're making now will ever be removed and replaced, you need to take a minute to figure out how to ensure that those following in your footsteps understand just how critical the base metal chemistry is."If I'm preaching at the choir" I apologize.  But I've seen too many instances of problems that arise because the person who knew "how everything works" quit, retired, or died.  Hopefully your company or customer has a way to document the material specifications.  Or a way to amend welding or maintenance procedures to ensure that the chemistry required for these parts is known to anyone that touches the parts going forward.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Thanks to all for your input. its been a challenge.Last edited by Chris Kyson; 08-16-2015 at 07:34 AM.
Reply:@ Kris Kyson - did your WPS achieve a CE <0.67?  Intetesting thread.Last edited by ManoKai; 08-16-2015 at 08:46 AM.Reason: spelling"Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi