What stainless are you talking about? The base metal? The HAZ? The weld metal? They will all have different FN results.
If the WM, don't you want a little ferrite? And wouldn't you expect the chemistry, by dsesign, to provide you with a little ferrite, within reasonable cooling rates?
Mike,
Are you sure the pipe wasn't magnetic before you started...?
Forming and drawing 300 series stainless can cause it to become magnetic....
We spent alot of money once having 0.035 347 filler wire tested because we discovered it was magnetic.... They splained it as being caused by friction in the drawing process.
If you have any unwelded pipe laying about give it a check.
This was just something one of the formen was telling me about. I told him I found that hard to swallow, that the weld would hold a magnet after welding. Well, we dug up a piece of 4"X.25 wall 316 stainless, and a plate, also 316 5" X 5" X.250. we preheated it, welded it, and checked it with a mangnet just after weldiing. I do not have the base material composition or even CMRT's on any of the materieal, just some we found out in the yard. No Lawrence, it would not hold a magnet before welding.
I think any 300 ss can become magnetized under the right conditions....no expert just xperiences talking here
If You heat that part cherry red and quench in water is it still magnetic?
I dont know. The piece had to dissapear after we did this LOL and is in a scrap yard somewhere in NM
Mike
Typically, ferrite in the weld can result in measurable magnetism. Regarding base metal magnetism, excessive cold working in addition to ferrite stringers.
Attraction of a magnet in greater or lesser degrees to stainless is not only possible, but likely. While stainless may be paramagnetic due to the alloying agents, it is far away from being diamagnetic as the Nickel and Ferrite constituents are ferromagnetic. Heat it up enough and let it cool, it will stick a magnet, welded normally, it will stick a magnet a little. The magnetic domains are typically disturbed and prevented in the most part from aligning by the composition of the metal (chromium and others) which is why you won't see it stick a magnet like say A36.
If I placed a guess, you'd either have a high ferrite number, to much heat on the weld, or a little of both.
Regards,
Gerald
I believe Gerald is on the right track with regards to the ferrite. The higher the ferrite number (similar to the % of ferrite) the more magnetic the stainless steel becomes. There are several factors that influence the amount of ferrite present. Operations such as weld, bending, cold working, drawing, etc. can influence the amount of ferrite present, hence the tendency to attract or hold a magnet.
Best regards - Al
Sorry it has taken so long, but I want to thank all of you for your replies. Working 13 hours a day now and driving 1 is not leaving much time for the Forum.
Again, thanks for all the replies
Mike
I remember once when I was doing a dimensional check on a small stainless steel product I was inspecting it on a granite table I took my trusty magnet and fount that it was drawn to the steel. Then I took it off the table, no more magnetism, I guess that the iron in the table cause the magnet to be attracted to the Stainless steel part. If anyone has a more elaborate explanation id love to hear it.
Maybe it's just me, but that sounds bizzare! The iron in a granite surface plate?? Was the magnet attacted to the granite??? Did you place it back on the table and was magnetic again? Or... was it possible that there was a portion of the SS part that was magnetic? Last fall I did run into a batch of 316L SS that the seam welds were magnetic but the rest of the pipe wasn't. Wished I would have been around long enough to see if the magnetism extended into the girth welds or if the girth welds were magnetic after welding. How can you not love this business when stuff like this happens.
That is an odd one...
Granite's main constituent is typically around 72% SiO2 (silicon oxide i.e. quartz), with FeO2 (ferrous oxide) being around 1.6% naturally. If this granite table has been in use for some time, you may want to see if has embedded Fe dust (has anyone been using it for MT?). Might also be a good idea to check the table itself and find out if in fact it is granite. Something would seem amiss with your situation. If you happen to have access to a ferritiscope, use it to check the table for the embedded fe concern.
Regards,
Gerald
I have to comment on Lawrence's post...he is 100% correct. ANY ANY forming of 300 series SS CAN cause it to become magnetized before its welded. I am not capable of laying details for the physics of it.....but pulling those molecules around in fab work can induce magnetic properties. I have seen it. I would assume those mag properties could survive on after the welding process.
May I add that this is O N L Y applicable to 18 / 8 type compositions -
Your 316 and 316 L materials are non magnetic regardless of the degree of cold work
and may have weld nugget magnetism due to relatively low ammounts of delta ferrite -
I would have to disagree due to a couple of odd situations I've crossed over the years. As a matter of course, your absolutely correct. However; there are some factors that can cause 316/304 etc to become magnetized. My guass gage says so anyway.
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