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How to identify a stainless steel ? [metallurgy]


Externet
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Good day.

A spring of stainless steel appearance is attracted to a magnet.  As there is diamagnetic and paramagnetic stainless steels, I would like to find out.   Half submerged in salt water for a day now; am supposed to see if corrodes.  What is a way to find what metal is it made of ?  The manufacturer did not want to reveal when asked. 😒

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1 hour ago, Externet said:

Good day.

A spring of stainless steel appearance is attracted to a magnet.  As there is diamagnetic and paramagnetic stainless steels, I would like to find out.   Half submerged in salt water for a day now; am supposed to see if corrodes.  What is a way to find what metal is it made of ?  The manufacturer did not want to reveal when asked. 😒

According to this source there are both magnetic and non-magnetic grades of stainless steel and the magnetic grades have poorer corrosion resistance:

https://www.eclipsemagnetics.com/resources/are-all-stainless-steels-magnetic/

 

 

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I like Forged in Fire also, and have always wanted to try to forge a knife.

This article gives several test, including the spark test, for identifying various steels

Learn to Identify and Scrap Stainless Steel | Public & Commercial Scrap Metal Buyer and Container Service. Public Cash for Scrap Metal Recycling in Westport, MA. Highest Scrap Metal Prices Paid (midcityscrap.com)

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1 hour ago, exchemist said:

According to this source there are both magnetic and non-magnetic grades of stainless steel and the magnetic grades have poorer corrosion resistance:

https://www.eclipsemagnetics.com/resources/are-all-stainless-steels-magnetic/

 

 

Yes martensitic stainles steels are usually magnetic, other types less so because they are usually low carbon and softer.

Quote

Thyssen- Krupp

Stainless steel grades 410, 420 and 440 – martensitic stainless steels. This type of stainless steel is magnetic primarily because it contains large quantities of ferrite in its chemical composition, which is a compound of iron and other elements

High carbon martensitic stainless steel is high tensile, brittle and can take a keen edge.

Normal stainless steel is of lower tensile strength and softer (more ductile) unless there are additional alloying elements such as molybdenum or manganese.

The stainless part comes from having sufficient nickel and chrome in the alloy.

But whilst chrome-moly alloy steels can be used for springs, they are often chrome-vanadium, with even some cobalt and or copper.

https://www.coilingtech.com/chrome-vanadium-springs/

Edited by studiot
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1 hour ago, MigL said:

I like Forged in Fire also, and have always wanted to try to forge a knife.

I've made knives, but I've never forged my own blade. That part seems like I'd need a teacher, a ton of materials, and a lot of trial and error. It looks like a whole bunch of fun, sweat, and tears.

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24 minutes ago, Phi for All said:

That part seems like I'd need a teacher, a ton of materials, and a lot of trial and error. It looks like a whole bunch of fun, sweat, and tears.

Seems like a medieval attitude to learning. Surely, in this age of information, research and study replaces trial, error, sweat and tears? Having said that, I agree that it can be theraputic doing it the hard way. And bladed articles seem to wake sleeping instincts in (mostly) men. It's hardly surprising, the quality of a weapon probably played a big part in the survival of our ancestors, ever since the first stone weapons. Maybe even long before that, as wooden weapons would have come long before stone ones. 

Personally, I LOVE stainless steel, I always did.

When I was little, sixty five years ago, we had spoons that had to be regularly polished. I don't know what they were, it wouldn't have been silver. But there was one spoon in the drawer that alway looked clean, never needed a polish, and we kids would fight like cats over it. It was engraved with the letter N on the handle, we called it the "N spoon". We always felt great, if we won the argument, and managed to bag the "N spoon" at dinner time.

We grew up thinking it was special, and only found out years and years later, that the N stood for NAAFI   !   It was probably filched from the Air Force mess !!

Wish I still had it. 

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16 hours ago, mistermack said:

Seems like a medieval attitude to learning. Surely, in this age of information, research and study replaces trial, error, sweat and tears?

I know there's a lot to learn about the color of the metal, since different processes require different temperatures. I could probably watch a bladesmith in a video and get most of it, but colors are often different in videos under varying lights. Even veteran master smiths have trouble forging outside in sunlight. It just seems like I could learn more faster by apprenticing, in this particular case.

I just saw an episode where this color-blind smith used table salt to tell him when his blade reached the proper temperature for quenching, since he has trouble seeing reds. All of the judges seemed like they'd never seen this done before, and were amazed. I get the feeling the learning under talented smiths is endless.

13 hours ago, iNow said:

Bladesmiths! Your time starts… NOW!

"It will cut!"

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16 hours ago, Bufofrog said:

I would use a handheld XRF Spectrometer.  It gives you an instant qualitative and quantitative results of the alloy.  Quite impressive instruments; I used one for a while a few years back.

I think you've nailed it. I did not know there was such a thing, but here is one commercial range of them: https://www.olympus-ims.com/en/xrf-xrd/xrf-handheld/ 

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On 8/6/2022 at 3:52 AM, zapatos said:

Exactly. That is why everyone is a great painter after taking an art class and watching a bunch of Youtube videos.

Anyone can be a great painter these days. 

Talking about blades, I thought that stainless steel was second class, compared to carbon steel, when it comes to fine knives and swords? Or has that changed? 

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At my old scrap yard they just used magnets. If something was attracted by a magnet, they classified it as non-stainless (3 times lower price than stainless). I told them it wasn't enough to classify, and they replied "we're not a lab"....

Edited by Sensei
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