Type 316N Stainless Steel

Date 08-31-2007 16:05

IMO, and just my opinion, its good news and bad news. And we could sure use Chuck about now too.
Anyway, N will dilute from the BM reducing ferrite in the weld metal. This will increase the possibility of hot cracking, but will decrease magnetic permeability.
And when qualifying, my guess is your tensiles will break in the WM due to lower N.
Now, since magentic permeability is an issue you may wish to go with a fully austenitic weld metal anyway, and just toss the concerns for lower ferrite out the window. This of course prevents you from going with a higher ferrite filler to compensate.
Just guessing, but perhaps an enhanced 310 if the standard 310 don't meet the strength requirements(I haven't looked up the mins yet, and don't remember them offhand), or even a nickel alloy (NiCr-3 or NiCrMo-3 perhaps-though N diluted from the BM will form NbN with Mo-3-don't know if this is a real problem-I've welded miles of AL6XN with the Mo-3 with nere a problem, though the nitrides are there)(also, NiCrMo 3 will be a stronger WM with plenty of ductility).
I hope this post has raised a few issues that help.
In any case, whether fully austentic or diluted low ferrite, hot cracking will be the primary concern. Run it cool, keep dilution down.
The magnetic permeability allowance can only be determiend by a testing regime established by your engineering.

By CWI555

Date 08-31-2007 17:18 Edited 08-31-2007 19:00

Nickel itself is ferromagetic. A high count of Nickle will be a problem if your concern is for magnatism. NiCrMo 3 will be around 55 percent by weight. This is not something you want to use for concerns of magnatism. It is highly permeable and highly retentive (which while it is ferromagnetic, is why MT is not used on high Ni alloys). The lower percentage as found in 316 may or may not be an issue.

Regards,
Gerald

By js55

Date 08-31-2007 17:37

Gerald,
You got me confused. Since MT relies on the possiblity of a magnetic flux, or essentially magentism, wouldn't MT be then used on nickel?
And why do nickel alloys, or high nickel SS's such a 310, AL6XN, 904L, show no ferrite nor magnetism?
Why is the magnetism of MT ineffectual and yet it would prove problematic for the application in question?

By js55

Date 08-31-2007 17:42

Did a little research. You're right. Nickel is ferromagentic. One of five elements. Cool. Didn't know that.
So then my question would be, why MT is not used on nickel, and how this ineffectualness of MT is different from a magnetic application such as the one in question?

By js55

Date 08-31-2007 17:51

Now this is interesting. Would a nickel alloy such as NiCrMo-3 (~55% Ni) or NiCr-3 (with ~80% Ni) with ferromagnetism be more or less magnetically problematic than a ferrous alloy such as 300 Series SS's (with ~80% ferromagnetic elements), with one of the ferromagnetic elements being iron?
Which element is more problematic ferromagnetically Fe or Ni?

By js55

Date 08-31-2007 17:53

And perhaps I don't understand what permeable and retentive mean. Could you explain that. Hopefully I can keep up.

By CWI555

Date 08-31-2007 18:50

permeability is the the ability for magnetic lines of force (coercivity) to travel through the material.
retentivity is the amount of magnetism (flux density) retained.
http://www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/HysteresisLoop.htm

They hysterisis loop gives a graphical display of this.

The ideal candidate material for Mt is high permeability and low retentivity. Which would give a very narrow band on the loop.
NI will give you a very wide band. The residual magnatism issue for NI or an alloy heavy in NI is why it's not used on those materials.

Regards,
Gerald

By CWI555

Date 08-31-2007 18:58

http://en.wikipedia.org/wiki/Paramagnetism
http://en.wikipedia.org/wiki/Diamagnetic
http://en.wikipedia.org/wiki/Ferromagnetism

I'll leave those links with you. For Performing MT they must be understood. For the question at hand, just look up the hysterisis loop for the material at hand to determine if it can be a problem.

By js55

Date 08-31-2007 20:23

Thanks Gerald. I got some studyin to do. Tuesday maybe.

By chuck meadows (***)

Date 09-10-2007 22:05

I agree with your response strictly due to the magnetism likely to be observed. The Navy people I worked with in the past on an issue almost exactly like this one was solved by using a 310 filler metal. Using a 310 filler metal will still have a very slight amount of ferrite from the BM, but will still also be virtually non-magnetic is using a low heat input. I think the 310m filler is the way to go.

By Bob Garner (***)

Date 09-11-2007 18:22

Thank you all for your replies.

We will require welding procedures qualification and will get our client's (the Navy) requirements for magnetic permeability testing. There are some iron parts in this thing (ball bearings, etc.) so I can't say how critical the magnetics of this thing are, but from everybody's input, it all sounds feasible.

Thanks again.

Bob

By ssbn727 (*****)

Date 09-11-2007 18:55 Edited 09-11-2007 19:41

Hi Bob!

I believe you've got the right idea about what to do... The only questions I have for you is:

1) What do the contract requirements call for with respect to the Base/Filler Metal, welding process, etc.?

2)Does the USN/Contract requirements want this trolley assembly to conform to AWS D1.6 or, are they requiring you to follow NAVSEA/NAVSHIPS specifications??? I would definitely seek to clarify this before you start so it does'nt come back to bite you in the you know where - Capish???

On a personal note: I never heard of the USN use AWS codes. My experience has always been their exclusivity of using NAVSEA/NAVSHIP Specifications but then again, things inevitably change although in the USN's case, I highly doubt it! Who knows, I've been wrong before but, unless they already have women on Submarines, no offense to the females but until then, Submarines will be built according to the specifications championed by the Late, Great Admiral Hyman Rickover, and the rules of maintaining them will more than likely remain the same also. Still, I could be wrong on this since it's been awhile. ;)
The only exception to the rule would be to build something that will not become part of the Submarine itself, and that's what this trolley assembly is categorized as such so, then one could specify AWS D1.6 in this case. Hmmm, I guess I already answered question #2. ;)

I would also agree with Chuck's suggestion of using 310 ss filler because that is what we used to use on almost anything stainless external of the pressure hull, and in some locations/applications thoughout many of the SSN's (Sub Ship Nuclear - usually Attack submarines) and FBM's (Fleet Ballistic Missile submarines otherwise affectionately named "Boomer's" or designated SSBN's = Sub Ship Ballistic Nuclear) I worked on while serving in the USN and afterwards while employed at General Dynamics Electric Boat Shipyard Facility in "Rotten" Groton, CT.

They'll probably require the same but then again. the only way to know for sure is to clarify it with the USN folks, or else they'll turn around and bite you in the you know where for not doing so in the first place! :)

Finally, the way they (USN) Degauss these babies is pretty "NEATO" to say the least so, I do'nt think there is going to be too much of concern unless there is enough potential for the trolley assembly to transfer any leftover residual magnetism back to the Submarine hull once the degaussing is completed which is probably your own concern, and would be appropriate in this case.

Respectfully,
Henry

By ssbn727 (*****)

Date 09-11-2007 19:55

Hi Bob!
Could you please elborate a bit further when you mentioned "(A-thru tube weld will penetrate the box corner weld.) Any special advice here?"

Do you mean that the circumferential welds on the tubes OD's mate or are to be attached the longitudinal axis of the corner welds of the box members thus requiring depositing welds at those locations???

In other words, are the tubes attaching to the box member corner welds perpendicular to the axis of the corner welds or are the tubes going to be attached or connected parallel to the corner welds on the box members? I need clarification in order to give you an appropriate suggestion to your situation buddy. ;)

Respectfully,
Henry

By Bob Garner (***)

Date 09-12-2007 14:30

The trolley I'm designing is one of those trolleys that rides on the rails on either side of the degaussing wharf and is used to guide the sub into place. We're in the design phase here and when we get this finished up, it will go out to bid to a Contractor. This one is in Hawaii so we're doing the design for the Pacific Division. Since the wharf is a civil works project, we can specify welding per AWS.

The trolleys are roped to the sub and should never come into contact with the sub so there should be no transfer of any residual magnetism. If the trolley does come into contact with the sub, someone's career is gone.

I'm not sure what it's like to degauss a sub, but I had a Sailor over at North Island Naval Sation tell me that it will lift the quarters right out of your pocket. I think he was B.S.'ing me but it makes a cool story.

I really appreciate the expertise you have all shared with me and I'm talking with our spec writer to include the 310 filler rod spec.

Henry, you are right about the welds betweeen the thru-tube and the welded box beam that it penetrates. The groove welds around the tube will penetrate a portion of the groove weldes at the corners of the box beam. Normally, I try to avoid welding to welds but I can't in this case. Luckily, it's just a short portion of weld and the stresses are low. But since this is stainless steel, I wanted to make sure that this will work.

Once again, thanks to all.

Bob Garner

By ssbn727 (*****)

Date 09-12-2007 16:36

Hi Bob!

Thanks for clarification about using AWS D1.6... I now have a better mental picture as to what you are designing. ;)

The only question that comes to mind now is whether or not these trolleys will be left unpainted or not to protect from corrosion from exposure to the elements especially the close proximity of salt water?
You also mentioned the the ball bearings and other components that will be of different metals which immediately makes me wonder about the considerations one should take in order to prevent potential galvanic, and other types of localised corrosion cells throughout the entire design of these trolleys especially when exposed to that type of environment. I'm sure you folks there will take those issues into consideration during the design process. ;)

Now as far as what that sailor told you, he was pretty close to being correct although, I would'nt be anywhere near the boat while the degaussing is taking place because, the voltage and current they use will be far greater than what is used when one performs a more localised form of degaussing and on a much smaller scale.;)

If the trolley is not ever going to make contact with the trolley then, you basically can use just about any type of 300 series stainless, or even a duplex grade and it's like you said, all a matter of whether or not one wants to go about qualifying the procedure if one is going to use a BM that is'nt listed in D1.6. I mean, if the rails are made of carbon steel then, there's no concern about any residual magnetism coming from them, then the trolley's BM also should'nt have any effect with respect to the same potential... That's just an observation, even though I have'nt seen the layout yet. ;)

Another suggestion is to "overdesign" the trolley when considering it's overall strength as you previously mentioned because, when working with the USN and a prime contractor of the USN, I have personally observed the USN's practice of overdesigning, and I strongly believe that it's part of their overall design philosophy when compared to the civilian world. Just make sure it can be justified in the area's where there is a potential for high stress/strain conditions, whereby premature failure can occur because the ratio was'nt sufficient in the design to prevent it, even under the most unusual scenarios whereby the trolley would more than likely not be subjected to such loads that would result in a catastrophic failure.

Hey Bob, now that I can visualize pretty much what you're designing, I've got some other questions that you may or may not need to consider with respect to the trolley design and yet, I would prefer to discuss this further via PM if you do'nt mind so, I'll be in touch soon! :) :) :)

Respectfully,
Henry

By aevald

Date 09-12-2007 18:38

Hello Henry, I read through your post and this is not to comment on the content of it specifically but more to poke a little fun and make your day and mine a little less serious potentially. You may have already heard this statement, as I believe it has a bit of history, but here goes. You do understand that, "an elephant is in reality a mouse designed to military standards". Your comment in the post regarding "overengineering" for the Navy prompted me to remember this little diddy. Sorry I couldn't resist Henry. Have a stellar day, regards, Allan

By Bob Garner (***)

Date 09-12-2007 18:55

Henry, yes, please pm me, I welcome all suggestions. I really want this thing to be right.

Alan, I love that expression. In our case, were brewing up something that has to serve and service a whole fleet of subs. I don't really have a clue as to the cost of a sub but the cost of our little guide trolleys is a "fart in a windstorm" in comparison. But mainly, these things just have to work well.

Bob Garner

By aevald

Date 09-12-2007 19:37

Hello Bob, I'm glad that you got a bit of fun out of it. Some of my past work history was with a company that did a number of government type contracts, some for the Navy. I used to be astonished when some of the governmental oversight committees would come up with their reports on the costs of certain items and such...., that is until I was involved in the manufacture and documentation of this work. You quickly come to understand how the money racks up once you consider all of the fail-safes and other components that go into this process. Well, have a great day, regards, Allan

By ssbn727 (*****)

Date 09-14-2007 00:38

Hi Bob!
Great! I'll be in touch soon... It's been a really hectic day today, and I'm honestly out of breath so, this weekend for sure. ;)

Respectfully,
Henry