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Stainless or Stainless Steel?


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I went with a friend to drop off some scrap at a scrap yard and learned something. He had a bunch of old mirror brackets off of vehicles and some other stuff in the load. When they examined the load they had him put that stuff in the non-ferrous pile and weighed it up different and paid him a pretty high price for it.  I asked about this a the yard guy said that "Stainless" refers to the decorative stuff and is considered a non-ferrous metal as it has almost no iron in it, "Stainless Steel" However he said is the ferrous stuff that is used for Knives, Rifle barrels, ect. He said that when searching for metals around folks that know what they are doing don't confuse the two. In other words he said if your looking for "Stainless Steel" Don't say you are looking for "Stainless".

Live and learn.

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It may well be how the scrap trade distinguish it,  but as far as I am aware it is all stainless steel and all ferrous. The iron content is around 70% for the 300 series and 85/90% for most of the 400 series. Most of the 400 series has more carbon and is therefore hardenable.

The distinction between the two is usually made with a magnet. The 300 series is non-magnetic and most of the 400 series is.

Alan

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I have found out that for some reason they do not require a metalurgical degree ( or even a HS diploma)  to work for Min wage at a scrap yard, most of them think if a magnet does not stick it is non ferrous, and if you ask them to define what the term non ferrous means,  many cant answer any other way. We even have members here that post stainless questions in the non ferrous section of the forum.

Edited by Steve Sells
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Curious really.  I have just looked up that the definition of stainless steel is that it is an alloy of iron with a minimum of 10.5% Chromium. The Austenitic, 300 series is often referred to as "18/8 non magnetic" so it is only a bit more chrome than the rest  which is all more-than 10.5%.

I suppose it must be the 8% nickel content that makes it more valuable to the scrappies rather than the chromium.

Alan

Edited by Alan Evans
trying to make the point clearer
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you may wish to check you definition, its 12.5% FREE chrome. not 10.5%. and the key wording there is free chrome, meaning it is not bound up in carbides. If it were only 10.5% then D2 and a few others steels would be stainless and they are not,  Also most of the chrome in D2 is bound as carbide.

Edited by Steve Sells
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you may wish to check you definition, its 12.5% FREE chrome. not 10.5%. and the key wording there is free chrome, meaning it is not bound up in carbides. If it were only 10.5% then D2 and a few others steels would be stainless and they are not,  Also most of the chrome in D2 is bound as carbide.

​I did wish and I re-checked where I quoted from...British Stainless Steel Association Web site:-

What Is Stainless Steel?

Stainless steel is an alloy of Iron with a minimum of 10.5% Chromium. Chromium produces a thin layer of oxide on the surface of the steel known as the 'passive layer'. This prevents any further corrosion of the surface. Increasing the amount of Chromium gives an increased resistance to corrosion.

They also list five main types Duplex and Precipitation hardening (PH) plus the three listed by Crazy Ivan. But what do they know? :)

​Interesting the different levels of metallurgical knowledge and the necessary simplified descriptions. Maybe the scrappies had it right all along!

Alan

Edited by Alan Evans
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I think, with respect, you will have to argue it out with them!

I am just looking at the some of the documentation available from the Euro Inox site and they also refer to "at least 10.5%". definitely not typos, maybe they both used the same source of info.

As I indicated above, maybe any difference is brought about by simplification for a perceived audience. The sources I am looking at are primarily geared towards end users and specifiers rather than metallurgists.

I am not a metallurgist and know nothing of the D-2  to which you refer, I have only bought and forged 316L for architectural and sculptural pieces…but as it contains more than 10.5% Chromium why can it not be considered a stainless steel? Looking at the history of the stainless development getting the carbon low enough was one of the main difficulties.

Alan

p.s. I have just looked up a couple of spec sheets for 409L and that has a chromium level of between 10.5 and 11.7% so the 10.5% definition does look fairly sound to me.

Edited by Alan Evans
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Steve have you discovered any further information regarding your 12.5% and D-2 point?

The only thing I have found is from a description of D-2 on one supplier's site, the last line may be part of the answer:-

D2 Steel Properties

D2 steel is an air hardening, high-carbon, high-chromium tool steel. It has high wear and abrasion resistant properties. It is heat treatable and will offer a hardness in the range 55-62 HRC, and is machinable in the annealed condition. D2 steel shows little distortion on correct hardening. D2 steel’s high chromium content gives it mild corrosion resisting properties in the hardened condition.

 

Alan

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I guess the other thing is that the two statements are not mutually exclusive or incompatible…

"All Stainless Steels are an alloy of iron with at least 10.5% Chromium"

Does not necessarily equal "All alloys with at least 10.5% Chromium are Stainless Steels"….

Alan

Edited by Alan Evans
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Well, can you argue? Will you argue? Here 'steel is classed as follows well for scrap anyway ' A grade, heavy, general and sub-grade each with it's own price in descending order.

Cast, is deemed a class of its own be-it steel or iron makes no difference.

Only the sophisticated yards make s/s differentiation greater than 316, 304 and magnetic. Most don't really know how to differentiate between 316 & 304 unless its labeled in some way.

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Is there an easy way to differentiate 304 from 316 apart from labels Ian? I seem to remember it was too much trouble for me so I opted to only have 316 in the workshop and then I could not make a mistake and add a bit of 304 into a 316 job. 

This was prompted years ago by someone I knew in Germany who had a major commission spoilt by including a less resilient type which deteriorated badly. Whether it was his bad housekeeping of that of his suppliers I don't know. It made me very circumspect about it though.

Alan

Edited by Alan Evans
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Alan , yes there is and... it's a magnet believe it or not , hang a magnet on a string(a decent magnet not the on you got in aunt Sadie's Christmas cracker :rolleyes:) and waft(nice word isn't it) your 304/316 in front of it the 316 will get the magnet to move 304 won't.. see loads of useless advice! :D 

You could of course whip down the road(he,he) and get a spectrometry device and use that? Or mix up a mordant of 2 parts Nitric acid and 3 parts hydrochloric acid ,heat to 65deg C and immerse the object (here it helps to have a known sample) this mordant will "eat" 304 at a rate about 40% faster than 316.

But the bit of string and magnet has worked for me for the last 20 odd years.

Edited by ianinsa
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Percentages aside . one think you can be sure of is that a scrappie knows the value of his scrapp. I have been lucky enough to work amidst a few scrap yards and watched the dollars (or pounds ) rolling in and rolling out.

In Se London there are a lot of " independent workers" who pull your dumped scrapp apart and re sell the stainless and copper and motors and Ali  (or ALU) to the yard. the yard doubles up on their paid price  so basically they are getting people with hammers and hand axes to seperate their scrap for them.

 their work is more basic than ours.......

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Ian, It was the acid test that I read about and decided against. I have just been using up a horrible pot of picking paste (hydrofluoric and nitric) on 316L handrails, doubled gloved and in the open air but still terrifying…especially as I read up on the hydrofluoric afterwards and learned that it is the only acid that you should not use Sodium Bicarbonate with…should be lime…hey ho, guess what muggins was using...

But I thought that 304 was non-magnetic like 316, both of them becoming slightly magnetic by work hardening….unconfuse me please...

You're quite right Basher. All the scrappies need to know is how much nickel is in it. During my recent trawling through stainless specifications to reconcile the above discussion I discovered that most of the development of the new alloys over the last 30 or 40 years has been prompted by the volatility of the nickel market. They have been trying to get stainless properties with no (or at least) reduced nickel. 

Alan

Edited by Alan Evans
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Alan, hydrofluoric is the only acid that I have a specific No, No about that stuff is evil. The magnet 'trick' is for as 'sold' product and 304 is non magnetic and 316 is 'slightly ' magnetic.

As to 'worked' product? Even though we try to work iron free, contamination is inevitable in most shops. I've gone as far as to get s/s tops for welding tables but flopped on hammers, vices etc. Oh, and Keating and cooling cycles probably play havoc with the Metallurgy. I do think that using the induction heater is  'better'B)

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We have pins in our spinner that are either 303, or 304. They are moved around by a series of magnets to polish parts. It confused me as I was under the assumption that those were nonmagnetic, but they stick to a magnet really good.  

 

Mass spectrometer may be the new modern way to go.

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Well, you're running into the same old can of worms everybody who goes to the scrap yard for working stock runs into. Those guys are only interested in very broad categories, their interest is selling scrap, not making things.

If you really want to know what you're using just buy it new. Sure it won't be scrap price and you won't have the bragging rights of calling your blade (or whatever) recycled but you'll be able to sell a RELIABLE blade.

And believe me having one of your blades fail catastrophically in use or heavens forbid hurt someone failing will kill your rep dead Dead DEAD.

Once you have some miles as a maker under your belt you'll be able to assess found or scrap material more reliably but that's on YOUR experience and your HEAD. some things are just not worth rushing into.

Frosty The Lucky.

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I guess it won't be long before some chancer comes up with a Mass Spectrometer iPhone app. :)

I was looking at the Flir thermal imaging iPhone accessory the other day with a view to check the temperature of my furnaces and maybe for deer spotting/counting...only £200 once you have the iPhone. Inconclusively I might add I could not find either its range for animals or its temperature range. 

Alan

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