# 316L vs submarine steel?



## veleno

So which are the differences between the 316L and the submarine steel (not tegimented)?

Is the submarine steel really better?


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## CMSgt Bo

veleno said:


> So which are the differences between the 316L and the submarine steel (not tegimented)?
> 
> Is the submarine steel really better?


In a word, yes.

In many words assembled by fellow Sinner, Majj, a couple years ago:

The normal annealed austenitic stainless steels, 316L and 316L VM, have 150 - 190 HV on a Vickers Hardness scale. They can achieve 250 - 300 HV, when they are cold hardened (note: Ice hardened 316L & 316VM tool steels may achieve 600 - 700 HV; these are very expensive). The hardened austenitic stainless steel used in watches' cases (316L or 316L VM) has 200 - 240 HV.

The super annealed austenitic stainless steel 904L has circa 150 - 190 HV and the cold hardened super austenitic stainless steel 904L can achieve 250 - 300 HV (note: Ice hardened 904L tool steels may achieve 600 - 700 HV; these are very expensive). The hardened super austenitic stainless steel used in watches' cases has 200 - 240 HV. There are no differences in hardness between 316L, 316L VM and 904L stainless steels used in watches.

The SUG's patented special non-magnetic U-boat HY-100 high yield low-alloy Ni-Cr-Mo submarine steel for Sinn watches (contains C, Mn, P, S, Cu, Si, Ni, Cr, Mo, V and Ti and the MIL-S-16216K and MIL-S-16216 specifications set certain material composition, "weight % plus additional material if needed", requirements for it; but the exact composition of it is classified information) has 300 - 400 HV, usually around 350 HV. The U-boat steel used Sinn watches' cases have circa 350 HV.

Vickers hardness (HV) of steel and coatings simplified:

CrNiMo 316L & 316L VM austenitic steels aka normal stainless steels (chromium nickel molybdenum) 150 - 190 HV

CrNiMo 316L & 316L VM hardened austenitic steels aka hardened normal stainless steels (chromium nickel molybdenum) 250 - 300 HV

Ø *CrNiMo 316L & 316L VM watches usually have 200 - 240 HV*

NiCrMoCu 904L super austenitic steel aka super stainless steel (nickel chromium molybdenum copper) 150 - 190 HV

NiCrMoCu 904L hardened super austenitic steel aka super stainless steel (nickel chromium molybdenum copper) 250 - 300 HV

Ø *NiCrMoCu 904L used in Rolex watches usually have 200 - 240 HV*

CrMoN ice hardened martensitic steel aka ice hardened, e.g. 440A stainless steel, (chromium molybdenum nitrogen) 600 - 700 HV

CrNiMo 316L/316L VM & NiCrMoCu 904L steels Tegimented/Kolsterized 1,000 - 1,200 HV

Ni-Cr-Mo HY-100 steel - (submarine steel contains contains C, Mn, P, S, Cu, Si, Ni, Cr, Mo, V and Ti) has 300 - 400 HV

Ø *Ni-Cr-Mo HY-100 steel **used in Sinn watches usually have circa 350 HV*

HY-100 steel - Tegimented/Kolsterized (submarine steel contains C, Mn, P, S, Cu, Si, Ni, Cr, Mo, V and Ti) 1,500 HV

HY-100 steel PVD hardened & Tegimented/Kolsterized (submarine steel contains C, Mn, P, S, Cu, Si, Ni, Cr, Mo, V and Ti) 2,000 HV

I hope this helped. :-d


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## apeogre

What Bo said. And in a real world test, I wear a uniform with lots of zippers on it. I have marks on all of my Omegas from reaching into pockets and rubbing on the zippers. My U1 has none, and I wear it the most in uniform. Other than my suunto.


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## dukerules

I firmly believe that U-boat steel is the real deal, from a scratch resistance standpoint. I base that on personal experience to a degree, but more than that from pictures people post all the time of their well-used U-series watch cases looking essentially brand new. One of the main reasons I think that the U1 is one of the most amazing deals available in dive watches.


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## Janne

Can the U-boat steel be easily polished?


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## rationaltime

Janne said:


> Can the U-boat steel be easily polished?


While I have not tried it. I would say yes, it can be polished about as
easily as other steel alloys. You should be able to polish the mat surface
and see the change pretty quickly, though it may take a while to achieve
a finish that gives a specular reflection. Restoring the mat finish may be
more challenging than the polishing unless you have access to grit blasting
equipment.

If you decide to polish your U1 case, please post before and after photos.

Thanks,
rationaltime


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## mebiuspower

dukerules said:


> I firmly believe that U-boat steel is the real deal, from a scratch resistance standpoint. I base that on personal experience to a degree, but more than that from pictures people post all the time of their well-used U-series watch cases looking essentially brand new. One of the main reasons I think that the U1 is one of the most amazing deals available in dive watches.


Yeah no kidding. Few days ago I lightly bumped my bezel on another metal surface, and there's no scratches on it at all. I'm not going to try to do that again, but it certainly gave me confidence in wearing the watch more often than I thought!


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## Janne

I think a polished case and a Matt bezel would be quite cool. Alternat. the Black bezel.
I have to send my U2 to Germany to fix a strange leak betwee the crystal and the case.


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## rationaltime

Janne,

It could be interesting to hear the chronology of the symptoms and how
you diagnosed the leak. I wonder whether the desiccant capsule served
as a useful indicator that a problem existed. It seems it should be useful,
but here you are with real life experience.

Thanks,
rationaltime


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## Janne

The capsule is still pale blue. It was in fact a fellow Wusser that discovered the discoloration on a pic. I took the bezel out, and discovered that on several areas between the crystal and the case, there is a brownish (rust colour) staining.
I have not babyied the watch, it has been in saltwater ranging from freezing point, to being baked here in the tropics, and then dipped in the sea.
But, no rusting whatsoever enywhere else.


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## rationaltime

Janne,

Salt water is a pretty good conductor. I wonder if salt water stayed under
the bezel and caused galvanic corrosion between the case and the spring
which retains the bezel. I guess that spring is bronze. Perhaps there has
been lint or dust trapped under the bezel which retains the salt and moisture.
I suppose this is the reason it is recommended to rinse with fresh water after
salt exposure. Did you find a stain on the spring in a place corresponding to 
the stain on the case? 

I guess the leak of your watch has not reached inside the case. If you
cleaned under the bezel I expect the corrosion has stopped and you won't
see the stain with the bezel in place. Unless you see some other problem
I think it would not be worth the trouble of sending the watch to Sinn.

Thanks,
rationaltime


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## Janne

Well, I took the bezel out from the watch. The stain between the crystal & case can not be removed, and it stil shows in the edge-reflection.
Also, the bezel is funny. Sometimes it is quite loose, sometimes very difficult to turn.
I tried to clean every part, but thoste little "studs" are stuck in the case.
There was some green oxide under the bezel. Your explanation about the bronze has explained that part.
My other problem is that the colour on the bezel markers have disappeared.

I am toying with the idea of having them install a new black bezel, if the watch goes all the way to Germany.


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## George01161

*Remove U2 bezel*

Hello Janne,
I was hoping you could tell me if you used a special type of screwdriver to remove your U2 bezel?

The size seems a bit unusual and with the threadlocker, they screws on my U2 are difficult to undo.

regards,
george


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## CMSgt Bo

*Re: Remove U2 bezel*



George01161 said:


> Hello Janne,
> I was hoping you could tell me if you used a special type of screwdriver to remove your U2 bezel?
> 
> The size seems a bit unusual and with the threadlocker, they screws on my U2 are difficult to undo.
> 
> regards,
> george


Heat the links up with hot water or a hair dryer first to soften up the LocTite. ;-)


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## George01161

CMSgt Bo,
Thanks for the suggestion.

I removed the bezel successfully and saw a residue like what Janne mentions. 
In a Sinn U2 review, it mentions they use a glue between the crystal and case to secure the crystal in place.

Maybe that glue is the material in question and it is what has been discoloured...

regards,
george


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## Janne

I did not know that. Maybe!

I have very strong fingers, so I can easily conquer the threadlock.


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## TrickTock

Actually the Sinn U-series are made of ThyssenKrupp VDM 1.3964 steel, not HY-100. 

Here is a quote from the Sinn UX owners manual: "This is precisely the steel used by Howaldtswerke-Deutsche Werft GmbH and Nordseewerke GmbH for the external hulls of the U31 and U32 of the German Navy." 
The U31 and U32 hull materials are not classified. The hull constructions of these two vessels are described in great detail in several sources including:

Naval Institute Guide to Combat Fleets, E. Wertheim, Naval Institute Press 2007, p.243-244.
Reduction of Ships Magnetic Field Signatures, J. Holmes, Morgan & Claypool 2008, p. 13.

The 1.3964 steel is fully austenitic, thereby compatible with the tegimenting process. (Kolsterizing is only for austenitic steels).

As a side note, before this hull information was released, there was initial speculation that Alloy HY-100 was used for the U32. This alloy is martensitic and imcompatible with the tegimenting process. 

More evidence on the use of 1.3964, from an article from Germanischer Lloyd: 
www.gl-group.com/pdf/bravo_zulu_2006-01_E.pdf

"We wanted to build a diving watch that would set a new standard through absolute sea water resistance", says Dr Wolfgang Schonefeld, R&D manager at Sinn. The stainless steel type AISI 316L commonly used in watch making simply doesn't cut it. At 25 points, its PRE value is clearly below the PRE 32 level required for sea-water resistant steel. Submarine steel, however, boasts 36 points. 

PRE is Pitting Resistance Equivalent. Alloy VDM 1.3964 has a PRE number of 36.

Other suppliers provide this alloy, it is also known as XM19 and Nitronic 50.

Definitely it is better than 316L for mechanical properties and corrosion resistance!


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## CMSgt Bo

Hi TrickTock,

Welcome to WatchUSeek and the finest Sinn Forum on the web. Great first post and I can't wait to see your future contributions. ;-) 

If Sinn is indeed using 1.3964 that would make Rolex's 904L denser prior to the Tegimenting process. :think:


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## TrickTock

Thanks for the welcome, I'm glad to be here after lurking too long. Good idea to compare Sinn steel to Rolex steel. Sinn's U-boot stahl (Alloy 1.3964) has a slight performance edge on Rolex 904L.

Here is a comparison of the steels on the Brinell hardness scale (HB). 

316L = 217 HB Most stainless steel watches
904L = 150 HB Rolex
1.3964 = 290 HB Sinn U series

(Usually the Vickers hardness scale is only used for much harder materials, so it's not typically quoted for these austenitic steels. That's why I compare Brinell hardness here instead.)

So the Rolex 904L steel is softer and easier to scratch vs. 316L. But it has a very unique coloring which looks great when highly polished. And there is an advantage in marketing psychology for Rolex. To a layman, 904L sounds three times better and more luxurious than 316L.

The Rolex and Sinn steels are equivalent in corrosion resistance in seawater. Both have a Pitting Resistance Equivalent of 36 points. This is great for seawater exposure, though they still should be washed after exiting the ocean.

The Sinn steel has a lower magnetic signature than 904L - which is critical for a submarine in a mine field. But that doesn't really matter for a watch case. It's great marketing psychology for Sinn to associate their watch with a state-of-the-art submarine.

The Sinn 1.3964 is a stronger steel. Yield strength (0.2% offset) is

316L = 170 MPa
904L = 220 MPa
1.3964 = 560 MPa

Yield strength is an important mechanical property to consider for making a submarine that can go deep, but less important for a watch as the depth rating is usually limited by the sapphire glass. Rolex says they need special equipment to stamp their watch cases. That's a true statement, but the investment in special equipment is not because of the 904L alloy. It's a higher capital investment to stamp vs. machine the case. Stamping gives them a lower operating cost and that pays off when spread over their large production volumes.

According to Dr. Schonefeld, R&D manager at Sinn, it takes 560 grams of submarine steel to make a 75 gram case (scrap is created from machining the bezel, and two pieces of the case). 

Now my cost calculations: The current 316L transaction price is around $4000/tonne. 904L is four times the cost of 316L. Alloy 1.3964 is about 8 times the cost of 316L. So the total alloy cost for a Sinn U case is just under $20.

If someone wants to send me a Daytona and a U2 I can do some more comparison testing...


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## CMSgt Bo

TrickTock said:


> If someone wants to send me a Daytona and a U2 I can do some more comparison testing...


I bet you could. ;-)

This is truly fascinating information, but I've got to ask...did you stay at a Holiday Inn Express last night? :-d

Now that the properties of the alloys has been explained, how do the hardening processes differ between manufactures. I understand Tegimenting is nothing more than a Sinn trade name for Klosterizing. Marketing aside, how does that _really_ differ from Damasko's "ice-hardened, nickel-free stainless steel"? We all know what Damasko says, but is it true or mostly marketing hype?


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## TrickTock

CMSgt Bo said:


> This is truly fascinating information, but I've got to ask...did you stay at a Holiday Inn Express last night? :-d
> 
> Now that the properties of the alloys has been explained, how do the hardening processes differ between manufactures. I understand Tegimenting is nothing more than a Sinn trade name for Klosterizing. Marketing aside, how does that _really_ differ from Damasko's "ice-hardened, nickel-free stainless steel"? We all know what Damasko says, but is it true or mostly marketing hype?


I wish I had known about the "holiday inn express" learning method. Instead I wasted my time getting a PhD. I work in the petrochemical industry and have spent many years specifying alloys and fabrication methods for process equipment. And my family owns a large metal fabricating business that serves automotive and aerospace industries. So I get my dose of metallurgy talk at family gatherings too. 

I think the discussion comparing Sinn's tegimenting (very hard shell on a soft core) to Damasko's ice-hardening (medium hardness all the way through) has been well covered on the watch forums. Some damage scenarios will mess up a Sinn, but not a Damasko -- and vice versa. It just depends on the nature of the unfortunate watch accident. Both are great watch cases that can look new for many years if there are no severe accidents.

Damasko was smart to patent their choice of steel alloy for all watch case applications. They use Cronidur 30 (X30CrMoN15 1). They did not invent this steel, nor did they develop its ice hardening process. But they were brilliant in finding novelty in order to secure a patent. Here is their explanation of novelty from their US patent:

_"these materials have heretofore been regarded by experts as unsuitable for the manufacture of wrist watches, due to the fact that such steels are highly magnetizable, especially by external magnetic fields, so that they function as permanent magnets whose magnetic field strongly impairs the highly sensitive clockwork of a wrist watch. The invention is based on the realization that the aforementioned hardenable steel surprisingly is suitable for wrist watch cases, and especially if in the interior of the case a ring or plate enclosing the clockwork is made of a diamagnetic metal."_

So Damasko is saying that nobody thought to use this type of steel because it can become magnetic and screw up the movement. They solve this problem by putting in a diamagnetic inner cage around the movement. This might seem obvious to a WIS in hindsight, but probably was quite impressive to the patent examiner.

The Damasko ice-hardening is a complex process. I haven't yet seen it described anywhere on the web, so here it is: First the metal is heated to above 1000°C, then rapidly quenched to room temperature in oil. This is followed by deep freezing at - 80 °C for 1 hr, then tempering for several hours at 160°C to give hardness >710 HV. The Pitting Resistance Equivalant is 30 points which is similar to 316L. The nickel-free composition is great for people with allergies.

So what about Bremont watches? Here is a quote from QP magazine: http://www.jurawatches.co.uk/PDF/bremontrippingyarnQP1.pdf

_"Furthermore, all the cases and buckles are brought back to England to be treated for hardness with B-EBE2000 technology, a process used on the turbine blades of jet engines. The cases are heated to high temperatures and carbon diffusion is used to increase the overall underlying hardness of the case to 1,200 Hv on the Vickers scale (normal watch-grade stainless steel is more like 280 Hv in hardness). Argon electron ions then prepare the surface of the case followed by a metallic ceramic coating at temperature, bringing the case hardness up to 2,000 Hv - the same hardness as sapphire crystal._

Based on this info, Bremont is kolsterizing, then plasma spray coating. Since this is done in England, they are probably using Poeton Apticote 800/24. This is a tungsten carbide and cobalt coating applied with an argon plasma torch. That gives hardness of 2000HV, and is used on jet turbine blades. Poeton does work for Airbus and Rolls Royce.

DLC (Diamond Like Carbon) coating is starting to get used by lots of watch companies in the last couple years, like Glycine, Ball, Bremont, Linde Werdelin, MKII, Perrelet, Richard Mille, Panerai, Montblanc, Citizen, and Casio. The quality of DLC coating is highly dependent on the coating vendor. If done right, these will be >2000HV and will take a beating. I have found these coatings to be highly variable in ultimate hardness. And some have even delaminated around part edges.

If I had my own watch company I would use Nirosta 4565 for the case. It has a Pitting Resistance Equivalent >50 for ultimate corrosion resistance in seawater. I would harden it with the Swagelok SAT12 process (low temperature colossal supersaturation) to get above 1500 HV.

Don't get me started on ceramic cases...


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## andy_s

Very interesting - thanks for posting, fascinating stuff.


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## CMSgt Bo

I appreciate you giving us a "peek under the tent" of horological metallurgy and breaking it down into layman's terms so even a knuckle dragging mechanic like myself can understand.

With your background and assuming you're a WIS too, what do you look for in a watch?


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## Mark McK

Tricktock, Thanks for the informative posts. Very interesting stuff.|>


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## TrickTock

CMSgt Bo said:


> I appreciate you giving us a "peek under the tent" of horological metallurgy and breaking it down into layman's terms so even a knuckle dragging mechanic like myself can understand.
> 
> With your background and assuming you're a WIS too, what do you look for in a watch?


Here is what I'd look for in a watch as far as new technology developments that I'd like to see:

Completely oil-free mechanical movements (many are working toward this and Diapal is a significant step). This is tough considering a typical movement beats just over one billion times in four years. It would be nice to extend service times to >10 year intervals.

Use of steel that won't corrode from sunblock.

Harder and more durable AR coatings for sapphire crystals.

Better microadjust mechanisms on steel bracelets that can be changed on-the-fly as wrist size varies throughout the day.

Better adhesive systems for luminous inserts so they don't jump off the bezel.

Better inks for printing on the bezel's number indentations , that won't delaminate over time.

A quartz watch movement with higher beats per hour -- you could have a smoother second hand travel at the expense of battery life. But with large cases in style, and more room to accommodate battery volume, I'm convinced a 44mm watch could run 2+ years at 28800 bph on lithium. 

Better sealing mechanisms on the crown to avoid the use of delicate threads that wear over time.


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## holdemchamp1225

TrickTock said:


> Here is what I'd look for in a watch as far as new technology developments that I'd like to see:
> 
> Completely oil-free mechanical movements (many are working toward this and Diapal is a significant step). This is tough considering a typical movement beats just over one billion times in four years. It would be nice to extend service times to >10 year intervals.
> 
> *I completely agree with this assessment and there are several companies working towards this already and if I am not mistaken, JLC (which is my favorite manufacturer) already has a couple of their movements (Extreme Lab) which require NO lubrication!!*
> 
> Harder and more durable AR coatings for sapphire crystals.
> 
> *Yes, please!!*
> 
> Better microadjust mechanisms on steel bracelets that can be changed on-the-fly as wrist size varies throughout the day.
> 
> *Absolutely a MUST HAVE. Glashutte Original, Omega, and Rolex have recently come out with some brilliant micro-adjustment buckles that work amazingly! I currently have a U1000S and wish that it had a micro-adjustable buckle such as the one on the GO Sports Evo or Omega Ploprof as it would be infinitely more comfortable throughout the day. As with others, my wrist swells and shrinks throughout the day and with the standard buckle, it is difficult to get a great fit and unnecessarily more hassle to adjust as it requires a tool!*
> 
> Better inks for printing on the bezel's number indentations , that won't delaminate over time.
> 
> *Completely agree.*
> 
> A quartz watch movement with higher beats per hour -- you could have a smoother second hand travel at the expense of battery life. But with large cases in style, and more room to accommodate battery volume, I'm convinced a 44mm watch could run 2+ years at 28800 bph on lithium.
> 
> *Seiko's Spring Drive, although a hybrid movement of quartz and mechanical, has the ABSOLUTE smoothest sweep seconds hand on the market and the technology is FAR superior than anything else I can think of in terms of a quartz regulator with mechanical parts and implementation.*
> 
> Better sealing mechanisms on the crown to avoid the use of delicate threads that wear over time.


All great ideas and hopefully Sinn and other companies take some hints!!


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## rationaltime

Hello TrickTock,

You mentioned:
"If I had my own watch company I would use Nirosta 4565 for the case. It has a Pitting
Resistance Equivalent >50 for ultimate corrosion resistance in seawater. I would 
harden it with the Swagelok SAT12 process (low temperature colossal supersaturation) 
to get above 1500 HV."

I suppose having a high nickel content improves the corrosion resistance. Did you consider the
possibility of nickel allegeries (if you believe in that)? While I don't consider stainless 316L to be
low nickel, perhaps the finished product does not have nickel homogeneously distributed on the
surface. Do you care to comment on that?

Thanks,
rationaltime


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## Janne

My son has a Nickel allergy, a bad one. He is OK with the watches he wears, Omega, Tissot, and some japanese ones.

Does Sunblock increase the chance of corrosion?

The Sinn US has a batterylife of many years. 7?


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## TrickTock

Some people are genetically predisposed to develop nickel allergies. It is a contact sensitizer, and the prevalence of allergy is 10-15% of women and 1-2% of men (according to the Nickel Institute, June 2009). Those figures correlate with body piercing -- more exposure means that people are more likely to sensitize if they are predisposed. However most of these people with nickel allergies are fine with exposure to 316L, which contains nickel within the alloy, but not free nickel.

The nickel-containing alloys can release small amounts of nickel upon corrosion and wear. Alloy 316L, most commonly used in watches, will release less than 0.2 micrograms per week, per square centimeter of skin contact. But a very small portion of people are super-sensitive and are even allergic to 316L.

Why is nickel in most stainless steels? The main purpose of adding nickel is to stabilize the austenite structure of iron, which makes the steel non-magnetic and less brittle at low temperatures. Chromium, molybdenum, and nitrogen serve the purpose of increasing corrosion resistance.

The Damasko steel, Cronidur 30, is martensitic and has no nickel, so won't bother anyone with nickel allergies.

Nirosta 4565 contains 16-19% nickel, so it could be allergenic to some people with severe nickel allergies.

Yes, sunscreen can speed up discoloration and corrosion of 316L. It has a lot of organic chemicals which vary depending on the brand/formulation. It is common to do environmental testing of plastics, metals, and fabrics for sunblock exposure, and even synthetic human perspiration!


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## TrickTock

Good info Bruce. I hope JLC continues to innovate and get these oil-free movements into the more accessible price range of their "lower end" stuff (below six figures)! They are definitely at the leading edge.


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## vovle

*http://ablogtoread.com/sinn/sinn-900-flieger-watch-the-big-aviator-chronograph/sinn 900 flieger looks more shining than the 756/856, but all of them is tegimenting by Sinn. can I know why?
*


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## CMSgt Bo

vovle said:


> *sinn 900 flieger looks more shining than the 756/856, but all of them is tegimenting by Sinn. can I know why?*


The Flieger has a brushed finish making it more shiny while the others are media blasted, giving them more of a matte finish.


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## CMSgt Bo

Here's a story from the BBC where they're Kolsterizing (Tegimenting) military armor to make its surface 2x stronger than standard armor.

http://news.bbc.co.uk/2/hi/science/nature/7811567.stm


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## andy_s

CMSgt Bo said:


> Here's a story from the BBC where they're Kolsterizing (Tegimenting) military armor to make its surface 2x stronger than standard armor.
> 
> http://news.bbc.co.uk/2/hi/science/nature/7811567.stm


Interesting stuff indeed - this made me chuckle:

"Unexpectedly, the MoD team has given the armour a protective advantage by introducing holes into it. 
According to scientist Professor Peter Brown, these perforations help deflect incoming projectiles. 
"I wouldn't like to have been the first person to have suggested that," said Professor Brown"


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## aikiman44

+1 for this thread.
Great info guys.:-!


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## scm64

One of the best threads in a long time. Great stuff.


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## subseasniper

This why I love this forum, technical information presented in an understandable format and more importantly, without patronising the reader.

Big thumbs up for tricktock.:-!


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## hydrocarbon

Aw nuts - I had a long reply written and my Windows POS work computer crashed.

To briefly recap:
 
 I encounter some specialized alloys in the petroleum processing industry. Many of them have very desirable characteristics for the manufacture of pressure vessels requiring high corrosion resistance. A watch case is an example of this type of device. These "superalloys" offer superior properties to commonly used materials. Take a look at the manufacturer's info on Hastelloy C-22, for instance:
 http://www.haynesintl.com/pdf/h2019.pdf

 Inconel, Monel and others also offer some outstanding characteristics. Plus they look cool. Aside from difficulty of machining, which shouldn't be too much of a hurdle, the only drawback I can see is the high nickel content. As seen earlier in the thread, the increased cost should constitute a negligible or marginal increase in the total price.

 Tanatlum is also sometimes used in the fabrication of watch cases. It has some fascinating properties, and I would love something made of this metal on my wrist.
 http://en.wikipedia.org/wiki/Tantalum

 I really can't complain about the "U-boot-stahl" in my U1, however. I really appreciate that Sinn is focused on technical superiority instead of marketing, aside from the occasional "limited edition" for jewelry shops and that 47mm U-series abomination. I really think that they're the modern equivalent of what Rolex was 60 years ago - technical leaders and innovators. I like them even better because they don't waste resources on advertising campaigns.

 Finally, here's something off-topic, but it may interest the readership of this thread. It's a series of articles that presents math and numerical concepts in an engaging and accessible way, without being pedantic or pandering. I was very surprised to see that there was something worth reading in a mass-market newspaper for a change, and even more surprised that it was about math. They're well worth the time:
 http://opinionator.blogs.nytimes.com/author/steven-strogatz/
 http://opinionator.blogs.nytimes.com/author/steven-strogatz/page/2/


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## hydrocarbon

TrickTock said:


> Don't get me started on ceramic cases...


Thanks for the quality contributions to this thread. It's great to get some information from an expert, instead of the usual trivialities..._Q: Is this watch too big for my wrist?_
_A: If you have to ask, then yes._

_Q: Does this strap look OK? _
_A: It probably does, but you should take at least a fraction of the effort and expense spent worrying about how your watch looks and get some decent shoes if you're worried about appearance._
​There, I just eliminated a significant percentage of the superfluous threads on the forums.

Anyway, how does one go about getting you started on ceramic cases!? I'd be very interested in your insights on that topic...


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## deepcdvr

Janne said:


> Can the U-boat steel be easily polished?


Hey, Janne,

I have polished my U1 on several occasions over the years using a scotcshbrite pad. I work the watch head and bracelet and after a quick soap and water rinse, it looks absolutely brand new.. :-!


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## TrickTock

hydrocarbon said:


> Anyway, how does one go about getting you started on ceramic cases!? I'd be very interested in your insights on that topic...


OK, you got me started on ceramic cases. I'd like to see Sinn make a ceramic case one day.

The low-end "ceramic" watches are PVD coated metal, like the ones you can buy for under $500 at a department store. The PVD coating is in fact a ceramic, but not the entire watch case. Marketing this as a "ceramic watch" is kind of misleading and deceptive, though not an outright lie.

The high-end ceramic watches have cases that are entirely ceramic, for example some models from Panerai, Girard Perregaux, Bell & Ross, IWC, and Rado. Just about every fully ceramic watch case on the market is based on zirconium oxide (zirconia) stabilized with ~5% yttrium oxide. Watch companies are very careful not to call this "zirconia," as the name sounds cheap and fake -- like "cubic zirconia," the same chemical in a different crystalline form.

Zirconium oxide is too hard of a material to fabricate into a watch case by machining, so it is formed by ceramic injection molding. The ceramic powder is micron sized (1/1000 mm), and it is mixed with a plastic binder and compacted into solid pellets. The pellets are melted and extruded into a mold, very similar to traditional plastic injection molding. Pressures are on the order of several tons per square inch. The plastic binder helps the powder flow, and helps to retain the part's shape. The material is soft like a bar of soap when it is released from the mold.

Next the plastic binder is burned away at a low temperature, then the part is cooked for a long time above 1400ºC in order to sinter the ceramic powder into a single non-porous mass. The whole part shrinks by around 20% in all directions. The shrinkage is rather even on a small part, so final dimensional tolerances can be held to +/- 0.3%. That's equal to 0.1 mm on a 40 mm dial -- not that great. So critical dimensions have to be finished with diamond tooling. For example, the crown hole on the Panerai Black Seal takes two hours to drill out. So you can see why a solid ceramic case only goes on high-end watches. Not only the cost of post-machining, but huge initial investment in the mold dies.

Is ceramic appropriate for a tool watch like Sinn? Or is it a fashion statement like the ladies' Chanel J12? The big weakness of a ceramic case is the fracture toughness. Zirconium oxide watches have a fracture toughness of 7 (MPa/m2). The most common steel used for watches, 316L, has a fracture toughness of 200. I would not want to drop the ceramic watch.

But wait&#8230; most decent watches have sapphire crystals. That's still the weak point, with a fracture toughness of only 2. Just don't drop any watch onto cement, or you will have serious problems.

So yes, I think a ceramic case is worthy of a tool watch. The main advantage is hardness. Zirconium oxide composites range from 1300-1900 Vickers, harder than the surface of Sinn's tegimented steel at 1200 Vickers. The ceramic has much better resistance to deep scratches as the underlying substrate is hard all the way through. The ceramic can be adjusted with oxide additives to achieve almost any color - white, black, grey, olive, pink, etc. The color will not fade, and it is consistent throughout the case.

Besides zirconium oxide, only a few other ceramics have been used to form watch cases. Rado has pioneered the use of boron carbide modified with <10% lanthanum hexaboride. For marketing sake, they call this ceramic "high-tech lanthanum material", and it is 3200 Vickers. A few others use tungsten carbide injection molding to achieve 1400-1700 Vickers.

What do you all think - would you be interested to see Sinn make a model with a ceramic case?


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## smcx

Ok, I admit that this is anecdotal - and I don't own a watch with submarine steel to compare to, but...

My Rolex Submariner (supposedly softer 904L) scratches WAY less than any other stainless watch I own. Bracelet and clasp included even though I have seen other people post that they think the bracelet and clasp are 316. I know other Rolex owners that have had the same experience. Rolex 904L does not get marked up nearly as easily as regular 316 SS.


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## hydrocarbon

TrickTock said:


> OK, you got me started on ceramic cases. [...]
> What do you all think - would you be interested to see Sinn make a model with a ceramic case?


Thank you very much for the fascinating and informative reply. I definitely appreciate a technical explanation of manufacturing methods, rather than repetition of meaningless marketing terms. I had always assumed that ceramic cases were machined from bar stock; I had no idea that it was a complex molding and sintering process. Neat!

Yes, I would be very interested to see Sinn explore the use of ceramics. It would certainly suit their style, even if the benefits are mainly cosmetic. However, the Kolsterizing process currently used seems to offer very good scratch resistance already. Just compare the non-hardened cases to the tegimented ones if you ever visit their showroom - the difference in surface condition is dramatic.

I would like to see Sinn experiment with other materials as well. Any thoughts on the practicality of materials such as Hastelloy C-22 or tantalum? I can see the high nickel content of the "superalloys" being a problem, though it could be mitigated by using a caseback or layer on the back of the watch of a biologically inert material with a compatible thermal expansion coefficient. Tantalum seems particularly suitable for dressier or higher-end watches, and it would be great to see it used in something other than a Panerai, Hublot or Montblanc.


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## Janne

smcx said:


> Ok, I admit that this is anecdotal - and I don't own a watch with submarine steel to compare to, but...
> 
> My Rolex Submariner (supposedly softer 904L) scratches WAY less than any other stainless watch I own. Bracelet and clasp included even though I have seen other people post that they think the bracelet and clasp are 316. I know other Rolex owners that have had the same experience. Rolex 904L does not get marked up nearly as easily as regular 316 SS.


I think maybe you are subconciously protecting your Rolex more than your other watches? 

I believe Rolex have changed to 316L steel? I read it somewhere.


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## everose

Janne said:


> I think maybe you are subconciously protecting your Rolex more than your other watches?
> 
> I believe Rolex have changed to 316L steel? I read it somewhere.


Rolex have not changed back to 316L.

Although some of the bracelets are still made from 316L.

The new 116610 Sub bracelet is made of 904L as is the SDDS.

Rolex use of 904L has more to do with markeing than any significant, practical benefit,IMHO.

:-!


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## smcx

I use my Sub just like any other watch. I do not baby it. I think people are spouting off about how everything Rolex is marketing without really knowing. Has anyone actually tested the hardness of Rolex 904L rather than rhyming off the minimum hardness for the steel?


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## CMSgt Bo

Janne said:


> I believe Rolex have changed to 316L steel? I read it somewhere.


You forgot the :-d.


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## Janne

YES, SIR!

Corrected now.
But truly, I did read it somewhere they did it (or maybe are planning to do it?)


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## TrickTock

smcx said:


> I use my Sub just like any other watch. I do not baby it. I think people are spouting off about how everything Rolex is marketing without really knowing. Has anyone actually tested the hardness of Rolex 904L rather than rhyming off the minimum hardness for the steel?


904L is not as hard as 316L, though they are quite close. These hardness values are measured, and are included in sales specifications.

I agree, rhyming off hardness values does not tell the whole story on wear resistance. Two different steel alloys with the same hardness may have different wear resistance in a given application. Hardness is just one measure that roughly correlates to wear resistance. Even the value of hardness depends on the method you use to measure it. For example, the Rockwell B test uses a different geometry and force than the Vickers test to indent the surface. You can't directly convert between these two scales as the difference depends on the alloy being tested.

Wear resistance is very specific to the circumstances creating the wear. There are several different types of wear. "Abrasive wear" is erosion from rubbing on a softer material. Like the swirly scratches on your watch bracelet from rubbing against a wood desk. "Adhesive wear" is tearing the metal at points of high pressure contact due to friction. Like rubbing a car key against your watch case. "Impact wear" is denting a material without a sliding motion. Like banging your wrist into a door frame and denting the bezel.

There are all kinds of other factors to consider: Is it unidirectional sliding, or repetitive reciprocating sliding, or a rolling motion? What material is it moving against? What speed? Is it dry or wet sliding? There is no single number to quantify wear resistance. But there are a few standardized tests, including:

ASTM G132 - basically this is a pin sliding on a rotating disk. Material loss is measured over time.

ASTM G174 - contacting the material with a continuous sanding belt. Measure material loss over time.

Both tests show 316L and 904L in the same ballpark, with 316L having a trivial advantage in wear resistance. For example, by ASTM G132, the wear rate is 6.1E-04 mm3/Nm for 316L, and 6.5E-04 mm3/Nm for 904L.

I have not seen Rolex ever claim that 904L is more wear resistant than standard alloys used for watches. Their marketing only highlights that it has superior corrosion resistance and they decided to use a high force stamping process to fabricate the case. That's entirely true, so there's no false advertising hype. And 904L has a beautiful and unique color, unlike that of 316L.

The best part is that Rolex does an incredible job of refurbishing the case when you send it in for service. All the scratches disappear. It's like the fountain of youth!


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## TrickTock

hydrocarbon said:


> Any thoughts on the practicality of materials such as Hastelloy C-22 or tantalum? I can see the high nickel content of the "superalloys" being a problem, though it could be mitigated by using a caseback or layer on the back of the watch of a biologically inert material with a compatible thermal expansion coefficient. Tantalum seems particularly suitable for dressier or higher-end watches, and it would be great to see it used in something other than a Panerai, Hublot or Montblanc.


Yes, both those options would provide absolute corrosion resistance for any environment that a watch would be subjected to, and beyond. They can be machined, though it's moderately difficult. And Hastelloy C22 can be Kolsterised (Tegimented). The high nickel content of C22 (>50% nickel) might concern people worried about allergies. But it is bound in the alloy, with very little free nickel. So with respect to allergy, it's not too different from Sinn submarine steel which is 17% nickel.

I do like the heft of a tantalum watch. They are quite heavy, as Tantalum is more than twice the density of 316L.

There's not much point in engineering for corrosion resistance beyond seawater and sweat. But there is a niche market for everything!


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## Mark McK

TrickTock, I find your posts very informative and thank you for the information. I look forward to more of your posts on the WUS forum. It is this kind of information sharing that brings me back on a daily basis to this great watch forum!|> Regards, Mark


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## dukerules

I'm only slightly a Rolex fanboy, and TrickTock spells things out very well re. 316L vs. 904L wear resistance three posts up. That said, my Sea-Dweller bracelet and clasp show remarkably mild wear nearly two years in. I'd compare the degree of wear to that I achieve in three to four months with other bracelets. Now bracelet wear isn't something I'm particularly obsessed with, but it is interesting.


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## CMSgt Bo

In theory I appreciate Rolex using 904L stainless steel but in practice I find the polished areas of the Daytona too bright (blingy) for everyday wear.


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## Janne

I looked through the family's little collection of watches with polished cases, and these look different:
My wife's Rolex, and our JLC's.

The steel has a more yellowy sheen to it. Maybe JLC does not use the 316L steel?

BTW, has anybody seen a polished Substeel case? Has anybody tried to polish one?


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## dukerules

I remember seeing some photos a year back or so of a U1 SDR with polished sides.


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## CMSgt Bo

dukerules said:


> I remember seeing some photos a year back or so of a U1 SDR with polished sides.


I remember that; the poster didn't know anything about the watch because he snagged the pics from someone on Flikr.


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## subseasniper

Is this the pic you are referring to?


__
https://flic.kr/p/3625852106


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## dukerules

It was a similar flickr set, but those case sides don't look polished to me.


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## SSCR

deepcdvr said:


> Hey, Janne,
> 
> I have polished my U1 on several occasions over the years using a scotcshbrite pad. I work the watch head and bracelet and after a quick soap and water rinse, it looks absolutely brand new.. :-!


Sorry to dig up a long dead thread but can you post pics of your U1 deepcvr? Intrsted in what it looks like after the scotchbrite scrubbing.


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## deediver

Cool thread, I've been curious about this very topic since I picked up my Sinn U1000.

So far the finish on the Sinn has held up well. Diving watches tend to take a beating on the boat and in the water and the Sinn looks like it just came out of the box. The Sinn replaces a Suunto D9 that was lost at sea (don't ask) with a titanium finish that may have had a surface treatment of some sort. The Suunto held up well, but did show some scratch marks. I dove with that watch for five years and it looked good after heavy use.

I work as an engineer in the marine field and I've learned quite a bit from this thread about different marine alloys and hardening processes. I tried to do some research, but got lost in trade names and marketing jargon.

Thanks TrikTock for a job well done

Cheryl


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## CMSgt Bo

deediver said:


> Thanks TrikTock for a job well done
> 
> Cheryl


Hi Cheryl!

Thanks for your real-world feedback, and yes, TrikTock has become one of the resident Rocket-Surgeons here.

Has your 6000 Frankfurt chrono come in yet?

Bo


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## andy_s

It'd be good to see some pics of the U1000 Cheryl, it's fairly rare around these parts. 
I was just mentioning it today on another forum with reference to its 60 min chrono totaliser, a great design solution I think.


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## novan3

It would be nice if Sinn made a fully tegimented (including AR coat) U1 made entirely of U-Boot Stahl; bracelet, clasp, crown, screws, and marker hands. |>


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## umarrajs

Wow! Cool summary.


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## Janne

umarrajs said:


> Wow! Cool summary.


You are such a NecroWIS!


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## CMSgt Bo

Janne said:


> You are such a NecroWIS!


My fault, I linked to this thread. If any thread is worthy of being brought back from the dead, it is this one.


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## hydrocarbon

CMSgt Bo said:


> My fault, I linked to this thread. If any thread is worthy of being brought back from the dead, it is this one.


Agreed; TrickTock's posts in particular were _quality_.


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## Boaters

Awesome info my next watch u1 teg.


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## avrvmadrid

Glad this got refloated, great thread,shame it seems to have died


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## Boaters

I feel the same way just read it again pretty much got my mind set on a u1 -T really liking that sub steel to bad the prices just went up now it is a c note more.


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## poomsar

Reading this in 2017....

Very cool thread!! U1T it is

Sent from my SM-T810 using Tapatalk


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## Camguy

Glad this thread got re-animated. Absolutely fascinating reading.


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## Spring-Diver

Wow! What a read 

This should be it's own sub forum 



Sent from my iPad Pro using Tapatalk


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## CMSgt Bo

Spring-Diver said:


> Wow! What a read
> 
> This should be it's own sub forum
> 
> 
> 
> Sent from my iPad Pro using Tapatalk


This thread has been resurrected more times than Jason Voorhees in those silly slasher movies from the 80's. ;-)

It's still as relevant as it was 9 years ago (Sinn steel analysis, not Jason Voorhees).


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## Kahuna

Tons of great information in this thread! Thoroughly enjoyed the read! b-)


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## Commisar

What a fascinating read

Sent from my SM-G973U1 using Tapatalk


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## deediver

Zombie Alert!

Many years later and I still have the U1000 and it still looks like new. Whatever Sinn is doing with their case treatment can’t be beat. I just ordered a Damasko DC80 in black and I hope it holds up half as well as the Tegimented Sinn.

The metallurgy and material science that goes into a modern watch is amazing, at any price point.


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## DestroLefty

So good, it needs to be 
BUMPED!


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