Hi Tommy,
Please allow me to give you my advice paragraph by paragraph. Again, this is just my advice, or recommendation.
Since you are using 316L as your metal of choice, any of the melts with FN=5, 5, and 7 are fine. Naturally, the higher the FN the higher the magnitism, if that is a concern. WRC 1992 is the most accurate and most recomended way to determine FN. These should not be a concern, in my opinion.
Without doing any calculations, I believe the sulfur content is so low that it would not be a concern even if you used an autogenous process with the TIG process, which you would probably not want to do.
For your thicknesses, naturally a low heat input and 300F.maximum interpass temp should be observed. A full thickness, stringer bead is recommended for virtually ay stainless steel weld process, but weaving is necessary in some processess like TIG, MIG, and SMAW. It just should be kept to a minimum. The most important in any stainless weld is cleanliness, and a dedicated clean SS wire brush. Preheating for moisture removal is correct.
Being that the rudder is probably going to be exposed to salt water (I assume) virtuall all the time, there are better choices than 316L. There are even better choices than a HTLA steel. 2205 Duplex is a reasonably priced choice.
Again, stringer beads with a 316 material is not as critical as if you were using another type metal such as a nickel alloy or a duplex. The 316, if that is what you plan on using, can withstand higher heat inputs than some other stainless steel alloys. Equally important is the interpass temp, which should be in the range of 300-325F.
As far as shielding gas is concerned, I like the 98%Ar/2%O2 as a shielding. If you decide to use an AR/CO2 mixture, keep the CO2 to less than 3%. Your tri-mix is O, but much more expensive and will not give you better shielding. The Atomic weight of Argon is 40, while the Atomic weight of Helium is 4.
One last thing, and it is very important. I recommend you take the time to pickle the welds. Removing the chromium depleted oxide layer, both on the surface and immediately below the surface is critical to corrosion resistance, especially in this environment.
Chuck
Chuck
Hello, Chuck,
Many thanks for your characteristically thoughtful response. Reading in this board is quite an education. Particularly thanks for the perspective concerning interpass temps and shielding gasses.
Also thankyou for mentioning the more suitable alloys for chloride resistance, both here and the response to the post concerning intermittent use of towing bridle chains. I confess to plotting another question , regarding alloy suitability , which must await further background research on my part.
Finally, thanks for taking the time to mention post-weld pickling. This had been my plan earlier, and will be going forward, although i was temporarily disuaded. I believe i have read a reference on this forum to a proprietary paste that would be apt.
What filler would you suggest if attempting to weld 316L parts with Ferrite Number less than 4, per WRC-1992? One of the melts involved here does have FN , by WRC-1992 , of 3 . I'm learning toward ignoring this number since when computed by the "FNN-1999" method, the FN is 5.
This (FNN-1999) is apparently an advanced statistical method employing regression, Bayes and , Monte Carlo theory and neural networks....essentially using a computer to compare inputs to results, based on the same experimental data that was collected for the WRC-1992 study. The authors claim better predictions because their math model takes better account of the interactions of the differing alloying elements in the melt. The research was sponsored by Oak Ridge National Labs, which desires high rel welds for the SS cannisters in which to store waste <http://www.aws.org/wj/supplement/vitek.pdf> and
<http://www.aws.org/wj/supplement/vitek.pdf>. A flurry (blizzard) of research has been sparked by these math model techniques here, and at WRC. The latest models incorporate process information on the job, to allow cooling rate inputs. If somebody combines a new set of data with these new models , probably a new standard FN would be accepted.
Tom m
Hey Tommy,
Personally, I use the FERRITEPREDICTOR, Version 3.21, American Welding Institute for my computerized calculations. There are many impherical diagrams, but I like the computerized version. I seem to think this is as close to the most sophisticated other computerized versions.
In any FN calculation, this is only a "prediction". The only true way to accurately determine the ferrite is to do an expensive lab test, as you already know. Realizing that it is only a prediction, but a close prediction, I would feel very comfortable with using the filler with the FN of 3 per WRC-1992. I'm not familiar with this FNN-1999 version, but the WRC-1992 version is determined to be the closest to actual FN calculations. The FN of a filler metal is calculated from the actual chemistry of each melt, so both of these versions should be very close to matching. A new standard for closer prediction of FN would be interesting.
Avesta Welding Products, my employer, is the only stainless steel manufacturer in the world that produces pickling paste. There are some chemical manufacturers that produce a form of pickling products, but we are the only SS manufacturer that does. I can send you info on this if you like.
TOMMY,
If you are still considering having the weldment made for you, I would like to quote it for you. I work for a leading exhaust manufacture OEM and Tier 1, and 2. We specialize in automotive, watercraft and heavy highway diesel exhaust and other SS fabrications. We use 307, 308, 309, 312, 316, and 347 as well as some Inco alloys like Inco 625 and 864. I am surly not as versed in SS as Chuck and would heed any advise that he gives for any SS application, but 300 and 400 series we know Very Well. Getting into the duplex is not really in our wheelhouse, but we are doing many R&D projects to determine their place in water-cooled marine exhaust. Judging by your research you are ready to weld this on your own, but if not maybe I can help.
Chuck,
I would like to know more about your pickling paste. I found the types in the Avesta Welding book. Light, Med, and Heavy, I have always used a very light compound for 316, is that right?? What makes your paste better than the other products available??
MDG
mdgwelding@yahoo.com
By tmmny
Date 07-28-2005 18:29
Mark, I've emailed you from hotmail... 'tbhp~".
By -
Date 07-28-2005 21:16
Mark, let me know if you would like some more pickling information on application, strengths, and importance of pickling ALL stainless steel welds and HAZ.
Chuck
Chuck,
(Again) thanks for setting me straight with regard to the FN.
Guided by a thread here last April, i snooped around the Avesta Finishing Chemicals pickling pages. The first thing that i noticed was the advice to begin with a phosphoric acid wash....which i think is also routinely suggested before applying a protective coating/paint. The next thing i noticed was the minimum product size for the Passivating Agent601 was 28KG. Oops, on another page i see that Pickling Pastes 101,123,130, and 140 seem to be available in 2,6 Kg (roughly gallon) containers! A litre would be about right for my project, even a gallon would be cumbersome. I expect to need about a linear meter of weld. Should the paste be applied to the entire structure, or only the weld and a margin??
Actually, i wouldn't know whether #101, #120, or # 601 would be better??
If you could tell me how to find a distributor in the LI, NY area [or NY,NY metro area, which includes No NJ, and Western CT] that would be helpful. I see there is a warehouse in Orchard Park, NY! Name(s) of job shop(s) employing the passivating paste in my area might be even better.
Of course i welcome any further info...i think i missed parts of the site; your response to MDG will probably help.
Thankyou, Tom m
MGD and Tommy,
Since both of your queries are similar, I will answer both in this thread. MDG, what makes our pickling paste very good is the fact that one cannot "over-pickle" with the Avesta paste. Also, it is made by a stainless steel producer, which tends to have more R&D work than just a chemical manufacturer. Since we make the stainless, it is reasonably certain that we know how to formulate the pickliing products rather than someone that doesn't deal in stainless, but only in chemicals. Hope that makes sense.
Tommy, Mills Welding Supply in Buffalo NY is a distributor. Tell you what, e-mail me at chuck.meadows@outokumpu.com and I will give you names and phone numbers of the inside sales people who can tell you the distributors nearest to your area. A phosphoric wash prior to pickling is suggested, but always necessary. The phosphoric wash is a very mild form of pickling that removes the free iron form the surface, which is necessary for corrosion protection. The real pickling chemical is a mixture of nitric and hydrofluoric acids. This removes the color (chromium depleted oxide layer) from the weld and HAZ. This is absolutely necessary for maximum corossion protection. It also removes the oxide immediately below the surface. Once the product removes the oxide and is washed off of the surface, the oxidation in the air allows the stainless steel to "heal" itself, or re-form the chromium layer that is necessary for corrosion protection. I have written a couple of papers on this exac subject and if you like, I will e-mail them to you if you will give me your e-mail address. Usually, pickling of a complete surface is not necessary unless the pipe, or plate, has surface damage or carbon impregnation. Usually, it is only the weld and the HAZ. The 2 types you should be interested in, as far as the pickling paste is concerned, is the RedOne or the BlueOne. RedOne is a little more potent than the BlueOne. Of course there is pickling paste for the weld and HAZ, a spray pickling gel for large vessels and the such, and a pickling bath for dipping small parts into a tub or vat. E-mail me and I give you a lot more documentation via e-mail. There is no need for me to bore everyone in this forum with things that they might not be interested in. Oh yeah, the products come in smaller containers than the gallon size.
Chuck
Chuck,
I don't think that one can have too much information!! Anything that you could send about pickling would be of great intrest.
Thanks in advance,
Mark
By -
Date 07-29-2005 16:57
Mark,
You've got mail..Ding.. :)
Chuck
