Author Topic: Metallurgist Info: Wanted. (Read 12423 times)

tel76 · « **on:** February 05, 2010, 09:10:30 »

I am replacing the water plates on the side of my block and i have obtained stainless steel screws identical to the original (Allen heads) that i would like to fit do we have a Metallurgist that can answer the following?
1- Will s/s screws be satisfactory in this application (with all the heat cycles)?
2- If i use s/s washers under steel bolts would this give problems sometime down the line?

Bernd · « **Reply #1 on:** February 05, 2010, 12:54:16 »

I am certainly no metallurgist, but should be no problem at all. Remember, stainless is made by adding chromium and nickel to plain steel (=iron). There are several hundred stainless alloys, some magnetic, some not, with additional components like carbon and molybenum depending on the desired properties of the end result, but there is no reason why any of that ought here. The bolts on these plates don't need to be hardened as they don't undergo any severe stresses on that location, and any stainless will beutifully handle the minimal heat on the block.....after all, if stainless is good enough to be used for high end cookware, where temperatures MUCH higher than water near the boiling point are a daily occurrence.

My vote is...go for it if you wish

Bernd

SteveK · « **Reply #2 on:** February 05, 2010, 13:04:06 »

I'm also not a metallurgist, but have been around then process industry for 35 years. I would vote no on this one. SS and Carbon Steel expand and contract at different rates. Mixing them adds no value and could lead to an issue. I would also be concerned about stress corrosion cracking of any stainless used at the temperatures our engines run. (this would be more of a problem if you live in a coastal environment)

ja17 · « **Reply #3 on:** February 05, 2010, 15:33:34 »

Hello,

I am also not a metallurgist, but have dealt with issues on dissimilar metals at my real job over the years.

First be aware that most stainless steel bolts are actually weaker than the carbon steel originals. If you look at the torque spec for the same size stainless steel you will usually find it to quite a bit less than the originals. so be careful you do not break them off. Stainless steel is much less machineable than carbon steel, so if you do break one off it can be more difficult to remove or drill.

Galvenmetric corrosion occur es between dissimilar metals that are in contact with each other and an "electrolytic fluid" like water is present. You basically are creating a battery which generates a slight electric current as the metals react on each other. There is a galvanometric chart which has values for all types of metals. As two types of metal get farther apart on the chart they become more corrosive to each other. I believe that stainless steel and cast iron are not that far apart so you should not have a issue here. Starless steel in some metals will end up causing more corrosion than a standard plated bolt.

Anyway, these are just some facts, I can't really say from experience, but it sounds like an interesting idea. Michael Salemi can write volumes on gavemetric corrosion I suspect, (car wash business).

hauser · « **Reply #4 on:** February 05, 2010, 23:57:32 »

I know a metallurgist. He is one of the owners where I get my car serviced.

Contact Steve Brotherton.

http://www.continentalimports.com/ser_index.html

mdsalemi · « **Reply #5 on:** February 06, 2010, 14:54:29 »

My own take is to leave it alone; if you want new bolts, replace with exactly the same. I'm a BIG believer in stainless steel, but I personally would not do anything on the engine block different than what came from the factory.

Bernd · « **Reply #6 on:** February 06, 2010, 16:39:53 »

Maybe I stand wrong in this, but I am not buying the reasoning so far. The base metals for Stainless and cast Iron are the same; the other chemicals in the two change their physikochemical properties. Thus, everything everyone has said so far is true. Obviously, there are somewhere around 300+ stainless alloys being produced with varying characteristics.

However, the covers for the water compartments on our engines are NOT exposed to the high temperatures, as, for example the exhaust side. After all, the temperature increases gradually from whatever ambient temperature prevails to working temperature of our cooling systems. In addition, there are seals between the 2 surfaces (plate and engine block).

Nobody seems to have problems mating stainless steel exhaust systems to our cast iron headers, right? There is tremendous expansion and contraction going on in that scenario; yes, there is not a "water" in liquid form interphase, but there is plenty of H20 coming out that side of our engines. The point here is not the water, but the fact that expansion/contraction occur to much greater extremes. The linear expansion/ contraction coefficient for cast iron is 10.4 (millionth of a millimeter per degree Kelvin change in temperature) That of mild steel 13.0, and stainless from 9.9 for ferritic to 17 for 304 austenitic alloys. Thus, for a 100 degree Centigrade change in temperature, steel will expand 13/10,000 of a mm, and stainless up to 17/10,000mm for the most expansile alloys. I venture a guess that the thread variance in our bolts is a bit greater than that, and given the fact that the bolt has to thread only a portion of a cm, I doubt this is an issue.

Also, if galvanized/zinc plated screws suffer a surface breakdown, I thought that the galvanic reaction occurring between steel and zinc often times accelerates the formation of rust. This would not be an issue with stainless. The only thing these bolts hold on are the covers in question, so strenth in this case is also not a problem.

so, beating maybe a dead horse into a pulp, as it's not really a big deal to me one way or the other, my vote still stands....should be just fine. However, I do recognize that there are MANY much more experienced individuals on this web forum than me. Perhaps they can help improve our knowledge base with real scientific explanations? I love to learn and won't be insulted if I am wrong

Bernd

mdsalemi · « **Reply #7 on:** February 07, 2010, 19:22:47 »

Bernd--

There may be 300+ stainless alloys, but probably 75% of all fasteners in stainless are 304 and most of the rest 316. You can find, if you search, specialty alloys and fasteners but it isn't easy. But that's neither here nor there; do an search on the internet and you'll find a variety of firms supplying stainless hardware kits for engines:

http://www.streetrodstuff.com/Products/1004/
http://alloyboltz.com/catalog/index.php
http://www.depss.com/

I would keep the normal screws not for any other reason than appearance. All of what you say is true, that stainless should not pose a problem. But is this particular location a place prone to rust or corrosion? Silver grade anti-seize or loctite will help.

Bernd · « **Reply #8 on:** February 07, 2010, 23:51:16 »

Hi Michael

you are absolutely right. I am keeeping my 280sl (almost....) original as well, and therefore I kept my bolts the way they were:). There are many cars that I see that are not show cars, but nonetheless are very nice, even with some minor changes. The decision of stainless vs. original in this case therefore is not necessarily a big issue: merely was trying to provide a rational asessment and answer to the question.

I hope to meet all of you guys at a future meeting, so I can put faces to the names I have learned so much from.

This website is awesome, and without it my restoration which took an 18 year detour due to life would not be possible without some major headaches.

Thanks again,
Bernd

RickM · « **Reply #9 on:** February 08, 2010, 16:37:33 »

I personally would not have a problem mating 304 (18/8) or 316 stainless to cast iron. I would have an issue mating stainless to stainless. Being of like composition is not always the ideal situation.

TheEngineer · « **Reply #10 on:** February 10, 2010, 20:49:11 »

Let's talk about nuts & bolts: Bolts (screws) come in different grades: The strength is different. It's marked on the head of the bolt. Don't replace rated bolts with something cheaper! Your stainless fasteners may be unrated. But please install every bolt and every nut with grease on the tread: It fills the small voids and prevents corrosion. For the hot areas use a heat rated grease, like that one made by Permatex, I have used it even on parts that go thru carburizing and the bolts come out nice. For nuts that hold the exhaust manifold, you should use brass or bronze. Don't be cheap! I have worked for many hours just to get a seized nut out!

tel76 · « **Reply #11 on:** February 10, 2010, 21:58:55 »

The origional combination allen headed/washer is no longer available from MB, the bolt that is now supplied is Torx pan head screw with the head being a larger diameter with no washer indicated, the new part number is N 000000 001145.
This bolt is not long enough to secure the alluminium side plate, this is the position that i was going to use the s/s allen head bolts.
I will tomorrow see if there is any indication stamped on them what quality they are as indicated by The Engineer.

TheEngineer · « **Reply #12 on:** February 11, 2010, 18:23:12 »

All Allenhead bolts are grade 8.

tel76 · « **Reply #13 on:** February 11, 2010, 21:42:33 »

Is grade 8 good or bad for this application and why only one grade?

66andBlue · « **Reply #14 on:** February 11, 2010, 22:01:22 »

Be careful which bolts (metric or US) you use and which grades (US) you think they have or to which class (metric) they belong.
Take a look at the list here:

Bernd · « **Reply #15 on:** February 14, 2010, 15:54:42 »

Growing up in Germany and working summers at a refinery in the maintenance and machine shop, we used a product called MOLYKOTE on all the bolts that we installed during maintenance work on the steam pipe flanges, turbines, etc.. It is a very viscous oil in a can that contains very fine copper particles in suspension. It was an absolut must to install in any area that was expected to require future disassembly. I am not sure it is available in the US (have not checked as I still have my quart size can from 1976

)Would definitely not use it in spots where vibration could loosen the bolts though, i.e. applications that require locknuts or Loktite.

Obviously bolt hardness grade is always a consideration in moving parts or parts requiring extreme torque.

Which brings me to a question. Since I disassembled my car 20 years ago, and am just now finally reassembling it, I seem to have misplaced the bolts for the center bearing braket on the drive shaft where it is connects/supports the driveshaft on the frame. Does anyone know the grade/length of those bolts?

Bernd

Naj ✝︎ · « **Reply #16 on:** February 15, 2010, 09:52:14 »

Quote from: Bernd on February 14, 2010, 15:54:42

Which brings me to a question. Since I disassembled my car 20 years ago, and am just now finally reassembling it, I seem to have misplaced the bolts for the center bearing braket on the drive shaft where it is connects/supports the driveshaft on the frame. Does anyone know the grade/length of those bolts?

Bernd

Steel Bolts (8.80) 8mm dia x 22mm long

naj

Bernd · « **Reply #17 on:** February 15, 2010, 12:26:12 »

Thanks Naj!!!

RickM · « **Reply #18 on:** February 16, 2010, 15:12:11 »

Quote from: Bernd on February 14, 2010, 15:54:42

Growing up in Germany and working summers at a refinery in the maintenance and machine shop, we used a product called MOLYKOTE on all the bolts that we installed during maintenance work on the steam pipe flanges, turbines, etc..

Bernd

Hmm, sounds like it would contain Molybdenum.

Actually, one product that comes to mind for the purpose you mention is bronze paste.

Bernd · « **Reply #19 on:** February 17, 2010, 13:06:14 »

Right on, Rick

You're right. Looked it up and Wikipedia has a nice write up about Molykote on their german website. The english write up is similar but only comes up under the name Molybdenum.

Anyhow, great stuff!!! Keeps nuts and bolts from rusting together

Bernd

mdsalemi · « **Reply #20 on:** February 17, 2010, 14:28:12 »

I use a Loctite "Siver Grade" anti-seize. Unfortunately Loctite is owned by a foreign firm who has an abysmal website so pointing you to the product there is hard--but you can get this at any Grainger and many industrial supply houses.

http://www.amazon.com/Loctite-Silver-Grade-Anti-Seize-BOTTLE/dp/B00065U978 Heck, even AMAZON sells it!

There are many grade of any-seize depending on application, the silver grade is a step up from the basic stuff on the shelves at the auto supply store, but below those specified for use in salt-water environments, etc.

RickM · « **Reply #21 on:** February 17, 2010, 16:40:30 »

Not sure what the Molykote Wiki says but Molybdenum is an element used in many different grease products and coatings. It wears very well in high temp / high pressure environments. You'll find the higher quality assembly grease products use Moly as a critical ingredient, ie Camshaft grease.

While I use it often, it's pretty much overkill 90% of the time.

Add / FWIW:

Funny enough one of my materials vendors came in today and brought a rep from Devcon/Permatex industrial.
In one of the catalogs there's a section dedicated to anti-seize products.

Properties as follows:

- Aluminum/Copper/Graphite lubricant - anti-seize and anti-galling assembly/disassembly up to 1600F. Saltwater and corrosion resistant.
- Copper lubricant - anti-seize and anti-galling assembly/disassembly up to 1800F w/ good electrical conductivity.
- Nickel based lubricant - anti-seize and anti-galling assembly/disassembly up to 2400F - No copper & good for high temp/high pressure apps

He mentioned that they also carry a Silver based product but I didn't go further.

Also of interest were the Urethane Flexane products. The rep stated that some of these castable compounds are used by car restorers to recreate motor mounts that are unobtanium.
Other industrial products available are the latest offerings to very accurately cast/reproduce parts in metal or resin. (This is where I have a bit of experience).

I love having options. Perhaps a thread on "What's unavailable and needs to be recreated" is in order.

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