Seizing (Binding) of Stainless Steel

None. They will all gall/seize.

Anti seize may be you only hope.

You need an anti-seize compound.

Is this a new problem?

Test/interview question?

What are you trying to do.

You can't expect an answer to a question with no facts/details.

Have you looked on the internet for an answer? I mean at a metallurgical site?

Mat web?

Search for "anti-seize stainless steel".

It isn't rocket science.

None that I know of, I have even had dissimilar grades coated in anti-seize compound and tightened correctly bind. All you can do is reduce the risk.

What's the application exactly?

"For piping the male thread is often either covered with a lubricant containing Teflon powders or Teflon pipe dope tape"

Even that doesn't help much.

Years ago an old and wise pipe-fitter showed me a method to greatly reduce, but certainly not eliminate, galling on both 304 and 316 fittings. When wrapping the Teflon tape around the threads of pipe, use a double layer or even triple layer of tape. This increases the distance between the male and female threads which reduces the occurrences of those micro points of the metal touching each other and "micro-welding" themselves to each other. Another extremely important point is to make sure that the tape is wrapped in the direction of the threads. Start at the end of the pipe and stop when the threads are at their shallowest at the unthreaded pipe section.

These help tremendously, not only when tightening a joint but especially when it comes time to take it apart.

Make sure that the tape does not go past the end of the threads. If it is shredded or torn off then you have a potential particle problem as it goes down stream.

Good Luck, Old Salt

Excellent, especially the comments about wrapping the tape in the right direction, thickness and where to start. Once worked in the pharmaceutical field and everything was St Stl. Hardest part was getting new operators to pay attention to what they were doing when assembling pipe fittings. In the sterile manufacturing almost everything was St Stl pipe. Tried Cherry-Burrell but couldn't assemble them aseptically. In that dept. it was a very expensive mistake if not assembled correctly since some were wholesale at in excess of $10/ml.

Good Luck, Old Salt

Beeeautiful - you got it.The company I work for builds sanitary process skids and the non-sanitary utility lines are always 304L. That's how we do it.

Great article on galling. This is a problem we encounter in high vacuum applications, we can't use lubricants other than a bit of isopropyl alcohol during assembly & have to use stainless. Our workers are very aware of the problem & have learnt not to force anything that feels tight but we still get the occasional bind.

Are other grades of stainless steel impervious to galling (bind) effects with 304L stainless steel, NO! As others here in this community more qualified than I can explain, depending on the kinematics of the circumstance, nearly any two solid metals contacting each other can be made to bind with each other.

Is this criticism applicable to your scenario, HTFSIK when you do not explain any of the kinematics of your scenario. For all we know these parts could be just stacked on a shelf in contact with each other or dealing with the impact forces of launching a 155mm howitzer shell.

Please think before you post.

A lot depends on the application....here is a study on various matches of SS in different applications with results....and possible mitigating coatings, treatments and lubricants...From the hip I would say 440C....

http://www.nickelinstitute.org/~/Media/Files/TechnicalLiterature/ReviewofWearandGallingCharacteristicsofStainlessSteel_9006_.pdf

There are different types of stainless steels:

Austenitic: Class 300

Ferritic: Class 200

Martensitic: Class 400

Austenitic-ferritic: Called Duplex

To which you want to refer

Not all are compatible with 304 Austenitic

I used to work on submarine reactor vessels and galling was always a big problem. The nuts that held the pressure head on were 1-1/2"-6 (I believe). We used CRES 304L cond A (again I believe). It has been 40 years since I worked on them.

I'm glad to see that you use the correct term. CRES 304L.

There should be a difference of 40 to 50 Brinell's hardness number or 15 to 20 Rockwell hardness C between mating components in order to avoid galling/seizing. The components that meet this criteria , will not seize/gall. SS is typically more prone to galling.

Re anti-seize

When using Swagelok stainless steel fittings, we often use Swagelok's Silver Goop® an "Oil-based thread lubricant for use on stainless steel and high-temperature alloys. Features ... Resists galling". See here http://www.swagelok.com/products/leak-detectors-lubricants-sealants/lubricants/silver-goop.aspx

Another possibility is to make bearings (or nuts) of non-ferrous metal having similar electro-chemical potential (to avoid creating a corrosive pairing)

Since claude chang gives no useful information in their question it's hard to give a satisfactory, intelligent answer.

But, if mechanical properties are important, non-ferrous metals may not be a good choice in this unknown application.

I wouldn't argue with lyn but bronzes have good strength as nuts and bearing shells.

If you are designing a fastening device with stainless components, ostensibly to meet load, reusability, size requirements, corrosion resistance, I would want to know what works well. We have used 304 and 316 SS 15mm or 5/8" bolts with nyloc nuts to fasten very large steel solar mounts for about 7 years. The threads do not extend into the bearing surfaces. We have had bouts of galling issues from time to time. It could be user error, or manufacturing defects, or a combination. I believe the stuff we use is made in China. We use large stainless flat washers at each end. If it galls, we use a cheater bar, twist it off, and start over. We want a permanent, good intentions resistant, locking pin. Does anyone have a comment about speed of nut rotation as it pertains to galling? I think slow is better, but it is only observational.

Getting teflon wrap under a nyloc seems like a poor idea to me. I've never mixed 316 bolts and 304 nuts, but I'll try it. They both seem to perform very well over time,, ie no corrosion, fatigue or failure. Lubricant seems to help, and we have seen no degradation of the nyloc, but then the oldest are only 8 years old. I have seen our installers use WD-40, which I stopped. They were alarmed that they were wasting 1 out of 20 fasteners, which I can appreciate. We want the bolts very snug, and torqued to 75 ft. LB. It's even possible that they are galled in that condition, as long as there has been no twist, I'm ok with it. Periodic inspection seems to be difficult to sell, everyone thinks that under any circumstance there is no reason to worry. (ie, spend money)

Anyway, if your primary concern is not to lose the nut (the bolt is acting as a pin). such as it is with us, galling is easy to spot during installation. At the slightest hint, we toss and replace.

The prevailing theory is that the mechanical work of engaging the threads is causing a temperature change, especially when the rate of engagement exceeds the rate of heat dissipation. To address this, the advice has always been (with respect especially to tapered thread pipe fittings of stainless steel) to (1) use a thread lubricant that has considerable heat capacity (such as alcohols that can evaporate away later), teflon paste, etc. My experience has been that any particular rate more than one revolution per several minutes will gall with teflon paste. If a leak free low pressure connection is all that is required, then one has the option of alternating materials between stainless steel fittings (given chemical compatibility exists). I use polypropylene tees in joints where stainless steel threads are connected in branch circuits for example. These require no tape, no thread seal, and due to the "stretchability" of black polypropylene, an exceptionally good seal is made against caustic soda or sulfuric acid. Obviously, this might not apply to sanitary, but one might have the option of using Kynar fittings as a go-between.

I hypothesise, but have never tested supercooling the parts to be joined with liquid nitrogen or dry ice, then running them up snug. The return to room (or other normal) temperature will actually loosen the threads as I recall, so very small movements should be made while the steels are warming up. Maybe someone will figure out precisely how to manage thermal welding (seizing) using this in some modified way, such as repeated cooling during tightening with a defined rate of torque, and speed. Perhaps an entirely new class of anti-seize compounds that are suitable viscosity at colder temperatures could be employed in this scheme.