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

Is the submarine steel really better?
 

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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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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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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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Can the U-boat steel be easily polished?
 

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

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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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I did not know that. Maybe!

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

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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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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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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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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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