# 904 vs. 316L



## daddycool (Sep 11, 2007)

What's the difference between these two marks of steel? :-s


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## croolis (Jan 15, 2007)

the number, apparently, and 316 has an L


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## lysanderxiii (Oct 4, 2006)

*904L Stainless Steel: *

<0.02% C, 19-23% Cr, 23-28% Ni, 4-5% Mo, <2.0% Mn, <1.0% Si, <0.045% P, <0.035% S, 1.0-2.0% Cu

904L is a non-stabilised low carbon high alloy austenitic stainless steel. The addition of copper to this grade gives it greatly improved resistance to strong reducing acids, particularly sulphuric acid. It is also highly resistant to chloride attack - both pitting / crevice corrosion and stress corrosion cracking. This grade is non-magnetic in all conditions and has excellent weldability and formability. The austenitic structure also gives this grade excellent toughness, even down to cryogenic temperatures. 
904L does have very substantial contents of the high cost ingredients nickel and molybdenum. Many of the applications in which this grade has previously performed well can now be fulfilled at lower cost by duplex stainless steel 2205 (S31803 or S32205), so it is used less commonly than in the past.

* 316L Stainless Steel
* 
<0.03% C, 16-18.5% Cr, 10-14% Ni, 2-3% Mo, <2% Mn, <1% Si, <0.045% P, <0.03% S

Grade 316 is the standard molybdenum-bearing grade, second in importance to 304 amongst the austenitic stainless steels. The molybdenum gives 316 better overall corrosion resistant properties than Grade 304, particularly higher resistance to pitting and crevice corrosion in chloride environments. 
Grade 316L, the low carbon version of 316 and is immune from sensitisation (grain boundary carbide precipitation). Thus it is extensively used in heavy gauge welded components (over about 6mm). There is commonly no appreciable price difference between 316 and 316L stainless steel.
The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures.
Compared to chromium-nickel austenitic stainless steels, 316L stainless steel offers higher creep, stress to rupture and tensile strength at elevated temperatures.


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## daddycool (Sep 11, 2007)

@lysanderxiii:

thank you very much for the details you sent, you were really kind. :thanks
As fas as I could notice the 316L is widely used these days, of course excepting Rolex who replaced it with the 904.


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## dadp2 (Sep 20, 2006)

I believe that I read somewhere that one of the reasons 316 is used in watches is because of the low nickel content. Many people have allergic reactions to nickel.


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## lysanderxiii (Oct 4, 2006)

It is also rather cheap, as far as stainless steel goes.


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## scrook (Dec 7, 2007)

lysanderxiii said:


> It is also rather cheap, as far as stainless steel goes.


316 is an extremely common corrosion resistant grade, 11-13% Ni, 16-18% Cr and 2-3% Mo, balance Fe. 904 is a specialty grade, primarily used for better sulfuric acid resistance, e.g. oil boiler/furnace chimney flue liners.


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## tony20009 (Sep 25, 2013)

lysanderxiii said:


> *904L Stainless Steel: *
> 
> [entry from Stainless Steel - Grade 904L (UNS N08904) deleted]


I was going to offer the same thing.

Whatever the reason is that Rolex uses it -- just to be different and have something to talk about would be the main reason in my cynical mind -- to me it's just stainless steel and no better or worse than any other as far as my watch wearing needs are concerned. IMO, it doesn't pass the "so what?" test, as in:Okay, it's made from 904L steel. What difference does that make to me? Why should I care? Why should I want to pay more for it?​I have to say, a lot of things about watches don't pass the "so what?" test, but if a maker is going to tout this or that feature as being special and/or important, it better be special in a way that matters rather than merely being a characteristic that makes their watch different from someone else's.



scrook said:


> 316 is an extremely common corrosion resistant grade, 11-13% Ni, 16-18% Cr and 2-3% Mo, balance Fe. 904 is a specialty grade, primarily used for better sulfuric acid resistance, e.g. oil boiler/furnace chimney flue liners.


I will accept that that is so. Not being of Latin descent, my blood doesn't get as hot as chimneys and furnaces. I'm not sticking my arm into one that's operating and I'm certainly not tossing my watch into one. So I'm okay with plain old 316 steel or whatever other steel a maker chooses to use. That's exactly the point of the "so what?" test.

All the best.

Some ties are red. Some are blue. Now show me what that difference will do.
- tony20009


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## LCheapo (Jul 14, 2010)

This is an old thread...
But anyways: I once read an argument somewhere ( homage forum?) that the sea and chlorinated water resistance of the standard 316(L) leaves something to be desired. So 904 might be better for those applications.


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## tony20009 (Sep 25, 2013)

LCheapo said:


> This is an old thread...
> But anyways: I once read an argument somewhere ( homage forum?) that the sea and chlorinated water resistance of the standard 316(L) leaves something to be desired. So 904 might be better for those applications.


I have read that too. I decided to ignore it as my hand isn't often in the sea or chlorinated water long enough for me to care.

All the best.


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## lysanderxiii (Oct 4, 2006)

tony20009 said:


> LCheapo said:
> 
> 
> > This is an old thread...
> ...


More from AZOM:

904


> Corrosion Resistance Although originally developed for its resistance to sulphuric acid it also has a very high resistance to a wide range of environments. A PRE of 35 indicates that the material has good resistance to warm sea water and other high chloride environments. High nickel content results in a much better resistance to stress corrosion cracking than the standard austenitic grades. Copper adds resistance to sulphuric and other reducing acids, particularly in the very aggressive "mid concentration" range.
> In most environments 904L has a corrosion performance intermediate between the standard austenitic grade 316L and the very highly alloyed 6% molybdenum and similar "super austenitic" grades.
> In aggressive nitric acid 904L has less resistance than molybdenum-free grades such as 304L and 310L.
> For maximum stress corrosion cracking resistance in critical environments the steel should be solution treated after cold work.
> Heat Resistance Good resistance to oxidation, but like other highly alloyed grades suffers from structural instability (precipitation of brittle phases such as sigma) at elevated temperatures. 904L should not be used above about 400°C.


316 and 316L:



> Corrosion Resistance Excellent in a range of atmospheric environments and many corrosive media - generally more resistant than 304. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 1000mg/L chlorides at ambient temperatures, reducing to about 500mg/L at 60°C.
> 316 is usually regarded as the standard "marine grade stainless steel", but it is not resistant to warm sea water. In many marine environments 316 does exhibit surface corrosion, usually visible as brown staining. This is particularly associated with crevices and rough surface finish.
> 
> Heat Resistance Good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of 316 in the 425-860°C range is not recommended if subsequent aqueous corrosion resistance is important. Grade 316L is more resistant to carbide precipitation and can be used in the above temperature range. Grade 316H has higher strength at elevated temperatures and is sometimes used for structural and pressure-containing applications at temperatures above about 500°C.


If you read carefully, 904L is better in warm sea water than 316 or 316L, and slightly better resisting stress corrosion, but not quite as good in elevated temperatures.

The real reason Rolex prefers 904L to 316 or 316L is probably this snippet: _*"...*__*In many marine environments 316 does exhibit surface corrosion, usually visible as brown staining...."*_

316 and 316L alloys do not turn orange and flake away in salty water like mild steel, but turn dark grey or brown, I have noticed this in several vintage watches. Rolex just needs them to stay pretty.


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## tony20009 (Sep 25, 2013)

lysanderxiii said:


> ...
> 
> If you read carefully, *904L is better in warm sea water than 316 or 316L*, and slightly better resisting stress corrosion, *but not quite as good in elevated temperatures*.
> 
> ...


The world is full of problems that don't need to be solved.
- tony20009

Good summary. TY.

Seeing as even the cheapest steel watches I have haven't had a problem, woe be to any watch maker/seller whose sole distinguishing factor is the steel they made it from. If that's all they have to show as to why I should prefer their watch over their competitors', their watch better look better than Helen of Troy if they expect me to buy it.

I'm much the same way about many things in that there is always the "so what?" factor to consider. I wanted to buy some loose gems to have them made into a bauble for her. The seller pressed hard extolling the virtues of this stone over that stone and why it was worth the extra money. I chose the cheaper one because I couldn't see any difference except under a loupe, and even then the guy had to tell me where at and what for to look.

Now am I going to tell her I bought the cheaper stone(s)? Hell no! I'm going to say, "I hope you like it." LOL It's kinda like that with the steel in watch bracelets. The differences could just as well be classified "Top Secret" because for my purpose, I don't need to know. For folks who spend a lot of time in salt water or in pools, well, maybe that's why so many dive watches also come with rubber straps???

All the best.

"And does Alan have a last name?" I asked. 
"Probably," said Curtis, "but we have a 'if you have to ask, you don't need to know because I don't want to friend you on Facebook' policy."
- Aldous Mercer, _The Prince and the Program

_


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## Throttle (Apr 11, 2014)

tony20009 said:


> The world is full of problems that don't need to be solved.
> - tony20009
> 
> Good summary. TY.
> ...


yup tony and its a two way traffic.
they dont need you as their customer either.
cheers


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