Bonding Stainless Plates

Pressure does not run. The description lacks the necessary precision to answer exactly what needs to be done.

6000 psi and plates and ports is a lethal combination.

Are you working on a Charles Darwin award?

I am having a little trouble attaching pics of these plates. This is an old German produced "adapter plate". That is what they called it. It is on old machinery that is 20+ yrs. The top plate is a flat, smooth surfaced piece of stainless steel. The bottom plate has the porting channels machined into it. These plates were sandwiched together with a process I am not familiar with. The way we took these plates apart was to machine away the top plate and then rebuild it. Each plate is 14" long x 7" wide x 1/2" thick. When together they are used to be an adapter between an electronic box that uses low voltage to operate solenoids and on the other side is a row of simple, manual valves that bolt straight to the bottom plates outside surface. These are bolted on with small 8mm bolts. The machined channels that are located in the bottom plate are 6mm wide and 6mm deep. I have tried some pretty high tech epoxy that failed under pressure. (I feel the mandatory thickness, .007 to .014 was not maintained). The epoxy was pressed too thin when the plates were bolted together. I am simply trying to get this back in working order. Thank you

Out of the house now.

Epoxy does not need.to be that thick, unless spacing is required. If so, use some .001 glass beads or equiv to maintain thickness. More later.

Keeping the adhesive out of the porting is something that needs to be figured out. I am having a hard time coming up with a substance that could be put into these channels and then sprayed out after the adhesive has cured.

OK. So, once bonded there is no outside access to these ports?

I'm hesitant to start recommending things yet, but maybe a glass cloth supported epoxy film adhesive could work.

You would need to experiment to limit squeeze-out into the ports. This can be die cut or laser cut so the adhesive oversize compared to the cut-outs.

Also, stainless steel is difficult to bond, due to its low surface energy.

More information will help.

I've done all this in a past life. One-offs for satellites was normal, as were exotic materials. This was long ago though and materials have advanced far beyond me now.

Something like this?

http://www.boschrexroth.com/RDSearch/rd/r_48045/re48045_2006-06.pdf

?

Yes.

On the Rexroth first page, under features, it describes them as "sandwich plates".

This is what I am working with. The working fluid is 97% water and 3% addatives. The working pressure is 5K and has the ability to see 6k psi spikes.

All the adhesive manufacturers I contacted had an absolute thickness and thinless number. I don't feel adhesives will work. I am more inclined to go with oven heated, metal based bonding agent. I have no idea where to go to get this done??

1. Where are you?

2. How many do you have?

3. Why not buy a new one?

4. Why did you take the old one(s) apart?

5. Why are you trying to put it back together?

6. Can you Google?

7. Can you post a picture?

Contact these guys then. I would think they have the plate you need. At least they know how to do this.

They might even be able to fix yours or make a new one.

It also talks about seals and screws.....these plates aren't screwed together with a gasket in between?

See my post #36. There are companies that do vacuum brazing in most metropolitan areas.

With vacuum brazing, the parts have to be clean, but no fluxes are required, and surface tension will pull the braze material away from any large holes/ports.

Most of the parts we have brazed were edges joined to flat or curved surfaces; I'm not sure if there might be difficulties with two large flat surfaces, but as long as the two main plates have very similar coefficients of thermal expansion, I don't see a problem.

If you can get the flatness specs on both pieces to lower tolerances, like 0.0005" precision grinding, and get them also ultra-clean without interfering with surface finish, then you could heat them in oven to a specification temperature under hard vacuum, and the metals will absolutely self-weld together. I am not an expert on this, but I slept in a motel in Ida-Bel, Oklahoma last weekend. Does that count?

What would you think that temperature would have to be?

Have you heard of anyone that does this process? I will contact them. Thanks

My first guess is bright yellow heat - upwards of 1000 °C, and obviously less than the melt point.

https://www.youtube.com/watch?v=TZ5sD9hQTyw

This is for Alumaloy aluminum "solder" or brazing rods. They can make amazing repairs with this on aluminum, but I have zero information as to whether this will bond with stainless steel. It apparently is great for bridging gaps and hole, so it might really mess up and plug your channels if you are not careful. If it did, you can always either remelt and separate, or you can try etching with hydrochloric (muriatic acid) (in a vented area). With some care you could dissolve excess aluminum with caustic soda solution (probably 10%, although lower strength will work also), and leave the aluminum between the pieces. This material seems to have high tensile properties, but I am totally not aware of bonding characteristics.

That's Diffusion Bonding. It requires a significantly higher temperature than vacuum brazing, of course depending on the chosen braze alloy. The parts must be supported to ensure contact at the intended regions, or the material may sag. This is especially true at diffusion temperatures.

Do you happen to know the temperature we are talking? Thanks

I'm NOT directly knowledgeable about diffusion bonding. In fact, doing just a tiny bit of research, it's difficult to distinguish between some forms of diffusion bonding and vacuum brazing.

There's also some info in Wikipedia.

Depending on the materials, we commonly vacuum braze around 900-1000°C.

LOL!!

Same thought, you were first!

My guess would be furnace brazing. I'm not familiar with using it with stainless steel, but fairly familiar (from a user standpoint, not fabricator) of brazed aluminum heat exchangers which have small passages.

Stainless would have to be brazed in a H2 atmosphere or the surface will form a green oxide coating that will not braze at all.

I think vacuum furnaces are commonly used. In OP's case, torch brazing might be possible. He seems to want to use a copper-based filler (not sure if he saw copper color in the original joint). I'd be concerned about galvanic corrosion, since copper is less noble than stainless steel and he seems to be using a water-based fluid.

You guys are very good! I will do some research into the information you have suggested. I will keep posting questions and results that come from these great ideas. I am not from this field. Thank you, Steve

I second this. I have soldered SS successfully in the past.

The solder is a real option.

Have you seen a copper based method?

Plus say a Rivet/Screw/other fixing in several areas when no porting is. Just to reduce or even stop bits flying around if the soldering gives way....a guard might also be a good idea too....6000 PSI is seriously dangerous!! I know that as I used to recharge gun buffers/recuperators in the RN.....

Not that I am saying it will give way!! Just "belt and braces(suspenders)!" always seems a good idea....

Very interesting blog.....

Plug or slot weld.

HP silver solder then clean up the ports?

Silver solder (silver brazing) is stainless steel friendly.

I suggest you explore either seam or spot welding. Most commonly used for jointing flat surface with negligible distortion and virtually no deleterious effect on micro structure of heat affected zone.

I love the web site thanks, but I could not find the pdf, can you help me to find it?

The link should go straight to it but try pasting this into your browser.

http://www.jm-metaljoining.com/pdfs-uploaded/Joining%20Stainless%20Steel.pdf

Thanks for trying, but it still does not work. Did you test it again yourself?

Eventually I even found the pdf, it appears to be "broken", sadly.....which is probably why the link does not help....

If you have a copy that you can send, let me know and I will send you a PM with a usable email address, OK?

The link took me straight to the PDF, on my Mac.

I think its me being on a foreign IP....

It opened for me. Good info.

I have had success with Loctite to build such manifolds with small porting, it is anaerobic so what may squeeze into the ports wont set up and can still be blown out. Works well long as you won't see temps above 400°F.

Good Luck.

Ricfre

I have successfully soldered large stainless steel parts together. Soldering is a lower temp solution than brazing and generally not as strong. Iridium Corp can provide the solder and flux and probably walk you through the process. Solders and flux's vary greatly in performance so be careful in any case. Basically a solder paste is chosen/applied to some thickness to achieve the final bead line and the assembly is heated to a required temperature to create the bond. The result is very neat with little or no solder excursion out of the bond.

Niagara Thermal Products in Niagara NY is one of the two or three companies in the USA that has a vacuum furnace that goes to high enough temperatures to vacuum braze stainless steel

I have them build stainless steel heat exchangers

Come on! There have got to be a lot more companies than that! I am aware of at least 4 here on the west coast, and know vaguely of several others. When our furnaces are too busy, we commonly send stuff to LA or to the SF Bay area to be brazed.

I used to be able to buy silver solder in shim form. You could use this to cut a 'gasket' and then apply flux and heat evenly to melting point, and voila!

Jim

I still have a bit of that that I picked up about 50 years ago, and it certainly is still available, but at 6ksi, I'd rather trust true brazing.

Of course there are quite a few different alloys that are called 'silver solder'. Some are way stronger than others, but my above statement still stands.

Again, with vacuum brazing, no flux is required. Excess flux can weaken a joint.

This link gives 40,000 to 70,000 psi tensile strength for 4.5% silver solder. http://www.harrisproductsgroup.com/en/Expert-Advice/tech-tips/tensile-strength-of-brazed-joints.aspx

I have also seen soft solder called silver solder so i understand what you are saying. Our supplier ( BOC ) has tip colours to denote the percentage of silver. As the silver content goes up so does the strength but also the melting point. Stainless steel joined with yellow tip has be done very cautiously as the flux burns off and the SS oxidises just after the silver solder melts. If you don't remove the heat quickly enough... Start again. Better to use a furnace and heat slowly till you see it run. Just looked at BOC webpage and found it is now called silver braze. Other posts now make sense. We may be talking about the same stuff. I used to call bronze welding 'brazing' and using silver bronze? sticks 'silver soldering'. Of course naming can be local and all is OK until you employ a 'foreigner' and ask him to braze something together and he uses the more expensive 'silver braze'...

Jim

This link says

Your "names" tie in well with what I was taught 50 odd years ago......eg. 100% accurate for me personally.

Alumaloy also makes a product that is low melting (500 °F) and will bond stainless steel (made specifically for stainless steel). You simply will need to figure out how to achieve even pre-heating (in an appropriate oven??) film the two pieces with minimal stainaloy (??) then join and cool. Metals must be very clean before wetting with the rod melt. Be careful not to use excess material, as this may clog the ports.

Thanks, I am looking into every option. Steve