EXTREME pressure lubes

[Phreakish]

This seems the best fit, and most diverse group:

I'm currently running a process by which a carbide die is yanked through a 4340 tube (2.5" od, 1.6" id) that is .05 larger than the initial hole. The carbide tools are G30 (tungsten carbide), and the 4340 is tempered to ~Rhc 21+-1, the length of the tube is approx 9". Typicall pull forces range from 275 to 350 BAR.

The issue is that we've had recurring 'galling' issues. 'Galling' may be a misnomer in this case, but its the termed used so far.

Observations:

Process: tubes are lightly coated with what appears to be an EP moly wheel bearing grease (black, sticky, industrial sized bucket).

The tools are typically 'wiped' clean, but not solvent cleaned - they rarely have much lube on them when the process begins.

At the end of the first stroke, we have metal transfer which varies from thin 'flake-like' formations that can be wiped away (almost completely, but not entirely) to actual smeared metal transfer (actual galling).
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The ID in the part is typically honed to size, with obvious (typical) honing marks remaining. Test blanks are cut to size with a boring bar, and as such the finish is quite different (these deposits tend to be flakier).

When the tool finishes its pass, there is typically no detectable lube on the contact surfaces. The finish of the ID shows 'polished' areas that relate to where the 'deposits' are found on the carbide tool.

What I'm looking for is a lube that can be applied to help eliminate the metal transfer. Or help with application techniques that may help based upon the above observations. Or am I up a creek?

 

[evelrod]

I'm not a specialist in EP lubes, but I do know of several conventional anti seize lubricants and synthetic EP lubes that are FAR superior to "moly based wheel bearing grease".
I don't even use that stuff for my WHEEL bearings! Yuck.

Rod

 

[Phreakish]

and they are???

Thanks.

 

[drwebb]

I think you need a metal working fluids specialist rather than automotive engineer. Maybe try the folks in the Tribology forum.

 

[carnage1]

You can get several brands of antisieze at your local parts store. you are obviously after a larger amount. most of the antisieze compounds are a thick petroleum base, with suspensions of metal in them. sulfur, nickle and copper come to mind but I'm not certain exactly what is in the stuff.

If you can try it without causing problems, try putting a big blob of the goo you already have on the end of the tool and running it, as it strokes it should get smeared thinly and evenly on the tool. This should tell you if you can just use a different application method or if you need a different lubricant.

A last question is can you spec a different finish on the carbide contact surfaces? ground carbide tends to be smooth but edmed carbide has a bit of a matte finish to it.

 

[Phreakish]

Thats one of the contentions. The original tool spec was for a surface finish of 2-4Ra, the surfaces to me appear to be as-edm'd to me, which cannot be good. We have other dies that have been coated with TiN, it didn't seem to do much good/bad for us.

 

[romke]

i agree with DrWebb. what could possibly help is the use of a socalled "cutting oil", usually a rather thin oil with somewhat "agressive" EP properties and limited cooling properties as used for metalworking purposes where EP properties are more important then cooling. they used to contain Cl-additives that worked very well, but nowadays other ingredients are included since chlorine is banned. a local metalworking fluid specialist might be able to suggest a suitable product

antiseize compounds are not designed for this type of operation, and neither are moly greases designed for wheel bearings.

 

[coatingengineer]

Hi.

Here are some ideas to get you thinking.

First, see greases as systems made up of two components: a thickener and a fluid. The thickener's purpose is to create a large surface area to retain the oil (the source of lubrication).

Greases have pressure-speed limits, ultimately determined by shear strength which, in turn, is determined by your thickener. Generally, softer greases are what you're after, since they're less resistant to flow.

But, under higher loads, yes, using softer greases, the lubricant film can become discontinuous. That's where EP additives help. Do use them with care. Lithium stearate soap-thickened greases may work, but I'd contact the National Lubricating Grease Institute. They're the experts.

For extreme loads, though, your choice for molybdenum disulfide is excellent. Solid film lubricants (also known as dry film lubrications) may be the answer. Applying them to your dies could be a nice fit.

If you'd like more information on MoS2 low friction coatings, consider:

<a href="

http://www.industrialcoatingsworld.com/Low-Friction-Coatings/MoS2-Low-Friction-Coatings.html">MoS2

Low Friction Coatings</a>


Good luck!









William Gunnar

http://www.IndustrialCoatingsWorld.com