Can u tell one SS from another?

[Handy560]

I was just wondering if there is a way to differentiate one type of stainless steel from another? I think some types will be attracted by a magnet...

I found a nice scrap today and I grabbed it thinking I could use it to try to tig weld on it.

I have some ss rod; long day and too lazy to go look but 308 seems to ring a bell...

I thought I read something here that this was for welding ss to mild steel, but this seems to be what the lws has for ss.

I was thinking I would first try to cut some small scraps and fuse them with no filler. If I do that should they be backed up with something or suspended? Then maybe lay a bead with filler on top of a piece then move to a joint... Does that sound like a good plan?

The material is maybe 22g or a hair heavier, but not 16g I don't think. I'm thinking 1/16 tungsten with a 1/16 rod when I get to that.

Maxstar 150 STL - do I crank it up - hot and fast?

Thanks in advance, you guys are the best...

[kcstott]

300 series is non magnetic (unless you have a very strong magnet)
400 series is magnetic.
Most sheet SS is 304, very common stuff
304 is non magnetic, non hardenable, high chromium stainless
Keep in mind this covers only the most common stuff welders run in to.
There are many other series sets of stainless out there.

[kcstott]

BTW
this IS welding so use what you got. I've used 308L on mild steel, tool steel (A2, D2, 4130, P20, Nak 80, etc) It will work but as with everything the end product determines your process. So for dinking around it's fine but if it's for anything structural well you know you have to do it by the book because someone WILL inspect it.
If you have the correct rod on hand use it, it will make life easy for you.

And to add to Handy560's post in the tool room we would use nitric acid on a ground and polished piece of unknown steel this would etch the surface enough so that under a microscope you could determine the type of steel it was.
Two warnings though: 1 nitric acid is very volatile. It's just plain nasty stuff. probably the worst acid you would ever be exposed to.
2 It takes a very good micro scope and a experienced eye to figure out what alloy the steel is. and even then it's a educated guess.

I know this is way more detail then you need. and when we did need to do something that had to be correct there was no guessing at what alloy the steel was. We ordered the correct grade with certs and called it good.
Kerry

[journeyman]

ss/ms

I'm not sure how to tell the diff of ss other than the mag test but if your going to join ss/ms then your best choice of filler is going to be 309L. The reason is that the 309L was specifically designed for the joining of the two materials by the addition of extra nickel and chromium. They do this to account for the burn off in the weld proccess.

Theres no reason at all why 308, 316,etc won't work but for the best results, whether molecular or corrosive then 309L if the way to go.

[Bodybagger]

This is what I use:

I used "EDAX" (energy dispersive x-ray spectroscopy), or AAS (atomic absorption spectroscopy). But I'm going to assume you don't have access to these instruments. If I had no lab and no nitric acid, I'd do this clever test using the Electromotive Potentials of metals:

Take KNOWN piece of 316 stainless, a KNOWN piece of 304 stainless, your UNKNOWN piece of stainless, and a chunk of ZINC (or aluminum or magnesium, etc.) and make sure they are all very clean by sanding with fresh sandpaper for each peice. Then, throw them all in a bucket of nasty salt water and vinegar, or another acid. Make SURE THEY ARE NOT TOUCHING EACH OTHER. After they have sat in there for a few hours, take a sensitive voltmeter (reading millivolts) and hook your ground to the piece of zinc (without letting the crome plated part of the probe touch the electrolyte solution), then probe the voltage on 316. Write it down. Probe the voltage on the 304. Write it down. Probe the voltage on your unknown. If it is almost exactly the same voltage as one of the known metals, you have identified it with pretty good certainty. If it's halfway between, it may be a different alloy, and the test is inconclusive.

Oh, BTW use a PLASTIC bucket or tray.

[Anti-GMAW]

I used "EDAX" (energy dispersive x-ray spectroscopy), or AAS (atomic absorption spectroscopy). But I'm going to assume you don't have access to these instruments. If I had no lab and no nitric acid, I'd do this clever test using the Electromotive Potentials of metals:

Take KNOWN piece of 316 stainless, a KNOWN piece of 304 stainless, your UNKNOWN piece of stainless, and a chunk of ZINC (or aluminum or magnesium, etc.) and make sure they are all very clean by sanding with fresh sandpaper for each peice. Then, throw them all in a bucket of nasty salt water and vinegar, or another acid. Make SURE THEY ARE NOT TOUCHING EACH OTHER. After they have sat in there for a few hours, take a sensitive voltmeter (reading millivolts) and hook your ground to the piece of zinc (without letting the crome plated part of the probe touch the electrolyte solution), then probe the voltage on 316. Write it down. Probe the voltage on the 304. Write it down. Probe the voltage on your unknown. If it is almost exactly the same voltage as one of the known metals, you have identified it with pretty good certainty. If it's halfway between, it may be a different alloy, and the test is inconclusive.

Oh, BTW use a PLASTIC bucket or tray.

Wow, Thanks for the tip! Thats an easy enough test as long as you have the voltmeter. Will this work on other steels as well? We have maspectrometers at work and these handheld X-ray defraction devices at work for identifying materials. QC walks around the shop with there X-ray gun checking boiller linings on a regular basis to make sure it matches the print. Different zones of different boiler systems get lined with varying stainless alloys depending on the corrosivnes of the gasses flowing through it and the temp. in certain regions of the boiller. SS. alloys range from 308L to any many of the 400 series.