Depending on the welding process and specific alloys being joined, 308L or 309L will work. I have qualified procedures using both of the above electrode/filler metal alloys.
It is an urban legend that 309L is the only alloy used to join these dissimilar materials. The PQR's in my files prove this point more than once.
CWIC
This is the second time in the last couple of months that I have come across competent technical people refuting the "urban legend" of using high alloyed consumables of the 309 type for welding cs to ss. Knowing you, I am sure you are saying this because of your experience(s). But technically speaking are all those metallurgical references, manufactureres of consumables and base materials, the Schaefller/DeLong/WRC diagram predictions totally wrong? I would disagree. What were the tests you carried out on the procedures tested? This surely merits a discussion!!!
Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com The whole of science is nothing more than a refinement of everyday thinking!!!
I agree with you. While I'm sure 308 will make a strong weld, 309 is usally preferred to keep the Cr level up, because of the loss during welding. It all depends on the end use corrosion-wise, and for cladding CS with SS the first layer should be 309/L.
The stainless steel part I was referring to is a 304 series handle that would be attached to a sheet of cold rolled steel. This assembly would be put together in a generic shop, and I do not know what their capabilities are.
In summary, can these items be joined by a welding process that is available to pretty much every shop that does small machine frames?
As discussed above, SMAW with a 309 electrode is pretty idiot resistant (readily available welding machine and consumables, high likelihood of sucess). Certainly there are many other processes and materials, but one would have to question the cost/benefit ratio to purchase and qualify a GTAW unit to weld a handle to a piece of cold rolled steel.
From memory, the stainelss to carbon steel weld is mde all the time on blowdown tanks and flash tanks. I had thought a 310 electrode was used, but am not certain.
If the articles are tubes and they are being heated to 750 F in normal operation, there can be a problem with cracking in the HAZ over time ( after 5 yrs operation) due to an alternating shear stress that is developed in the DMW for each startup / shutdown cycle. The cracks will originate in the mid wall of the HAZ and can only be detected by angle ultrasonics prior to failure. The shear stress is caused by the large difference in coefficient of thermal expansion between CS and SS. For such cases, the use of an incolnel electrode, wide weld pass, made by orbital welder, is preferred.
For the weld under discussion and for high volume production, the short-circuiting transfer mode of the GMAW process using E309 wire is recommended. Filler wire size will depend on material thickness - 0.030" diameter wire seems appropriate.
Tony:
Ours were structural applications. Specifically, one was a tubular space frame structure which also doubled as the fire water system to maintain a "clean" appearance. The other had hydraulic fluid within the tubing.
We performed testing which exceeded the code requirements of the D1.1/D1.6. (I never get any "simple" projects through my office.) We welded 304L to A 500 Gr. B tubing and 304L to A 53 gr. B pipe using SMAW and GMAW respectively. In summary, these commonly used processes are available at most any welding shop.
sayee/Metalguy:
1.) The engineer (metallurgical P.E.) who performed my testing is one of the most respected here in CA, he was somewhat surprised at the choice of filler metals and how well they performed during testing. Testing included NDT, bends, tensiles, macroetching and a sample was submitted for artificial aging which also performed quite well.
2.) One of the engineers at Lincoln Electric (the electrode manufacturer for both applications) also agreed we could use 308L with satisfactory results for our particular applications.
3.) Both 308L and 309L electrodes have a maximum C content of 0.04% for SMAW electrodes, and 0.03% for GMAW electrodes respectively. If the resultant weld metal deposit FN, intergranular carbide precipitation, etc. were an issue, then 309L would be my first choice (particularly if a pressure vessel, cladding, etc. was involved with the end product or service of the weldment.)
4.) Why did I choose the 308L for either application?
a.) Availability of electrodes at the time of fabrication.
b.) $. The 308L could be purchased for slightly less money (at that time.) It resulted in a substantial overall savings for my client. I have to be aware of the clients' costs whenever my services are rendered.
IMHO:
sayee, you mentioned qualification of welds in which slag was not removed between passes in another forum. I would never allow this type of workmanship on my projects with or without a PQR. If this occured, I would specify NDT on 100% of the welds. You also have mentioned using SMAW electrodes w/flux removed for filler metal using GTAW (in another forum). (Why?)
Well, it sounds like you get unusual projects as well.
While these materials may not agree with any text, articles or publications, it has been used with satisfactory results and proven over time and testing for specific applications. One of the structures was disassembled last year to run encapsulted wiring internally and the welds were noted to be performing better than expected.
Many of my projects involve unusual applications, joining methods, etc. That is why my services are requested. If it were easy, then anyone could do it...
CWIC, I agree to the fact that we get unusual projects once in a while. But since you have already done an unusal project, why should I re-invent the wheel if I am convinced on the methodology!!! That was my reason for asking you the questions, remember your asking me those questions on the post to do SMAW welding without interpass cleaning ;-)
For those who are following the discussion:
304 is approximately 18/8 i.e. 18%Cr 8%Ni. CS has 0% of Cr or Ni and typically say 0.25%C. You weld it with a filler wire ER308(18%Cr 8%Ni) and assume 10% dilution from either base metal especially for the root pass. You theoritically get a weld metal with chemistry 0.05%C, 16%Cr and 7%Ni and thus end up in a typical Aust+Mart+Ferrite microstructure as against a desired Aust+Ferritic microstructure. However do the same with a 309 filler wire and you will end up in an austeinitc + ferritic microstructure. Remember that cooling rates in stainless steels are not that critical as for CS(where martensitic microstructure can be obtained by very fast cooling rates) and that is why to avoid problems of distortion due to the intrinsic material properties of ss, water cooling during welding especially for thin sheets. CWIC looking at the application, the mechanical properties might have been me, wonder how such a PQR might fare tests like IGC A262, G48 and the likes though.
Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com The whole of science is nothing more than a refinement of everyday thinking!!!
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