tommy dunlop
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hi been welding a bit of stainless,using 316 rod,buzzed up to pieces of 316 (tig) and a magnet sticks to the weld why is this please,tom
The magnetic properties (permeability) of 3 series stainless steel (austenitics) are determined by phase shifts from martensite and austenite.
http://www.bssa.org.uk/topics.php?sub_category=31
Out of interest... what gas flow rate (lpm) are you using?
edit...
If your weld has cooled quickly then more martensite gets trapped allowing a magnet to become more attracted to the 316 stainless steel. If the molten 316 is allowed to cool slowly, the phase shift can occur, leaving more austenite. Hence magnets have a greater pull on the material.
Greater permeability is often seen in cold-formed (hammered, stamped, etc) 3 series stainless steels. Lesser permeability is often seen in hot-formed.
(I believe that's an old wives tale, langy!)
Al, are the filler wires designed/alloyed to increase the ferrite slightly for increased resistance to solidifaction cracking or something? Autogenous welds certainly show a lower magnetic response than welds made with filler
i've got some cheap stainless here that a magnet sticks to pretty good.
Its probably not 316L then. There is a lot of 3Cr12 about which is strongly magnetic (and cheap)
Thats what i said earlier but was told its a old wives tale Al
Cheers Al. The cheap magnetic sink thing... i'm thinking one of the ferritic alloys, googling '430 stainless sink' will get some hits but no doubt there are other alloys used.
I have often wondered about this one.
I wonder why does SS not stick to a magnet, it is a ferrous metal iron based and all that.
I just accept that it is this way because it is.
Knoba, you know some weird old wives, round here they talk about what was on telly last night.
Chunko'.
Not by me..........was it?
The plain Cr steels are stainless but not austenitic stainless. They are either Ferritic or Martensitic (or a mix of both) which makes them hard. At the low end they are cheap but the higher Cr grades are sometimes called surgical steel. The best knives are made from 440 stainless but you wouldnt want to start bending it or make a sink from it.