Pretty much supported by the concepts in industry, although I have little to document that concept. I do have ample information suggesting diamond grinding wheels not be used on steel.
Ah! Now we're talking. I have in my possession enough published information to substantiate the fact that silicon carbide does, indeed, dissolve in steel.
One must consider that at the point of contact, terrific heat is generated, so the rules sort of change. Because of the intense heat, there is dulling of the grain attributed to dissolving into steel. I'll gladly forward a scan of the information to you. One of my references is a soft bound booklet by Norton Company, copyright 1951. It is titled Lectures on Grinding. On page 19 there are two paragraphs that describe the accepted theory of the reaction.
Anyone interested in a scan is invited to request it. I'll get it out as quickly as possible.
I feel compelled to dispel misleading information, particularly in this instance. The problems from wrong wheel selection are overwhelming, speaking from experience. To get a better understanding of the significance of the wrong wheel, try grinding some steel on your surface grinder using a silicon carbide wheel. The net effect, and almost instantly, is for the wheel to glaze over. Hardness of the bond makes no difference, regardless of how you approach the problem, it persists. Change to an aluminum oxide wheel and it "magically" goes away. The research accomplished by Norton was right on the money.
Got me curious. Where's a first-year student when you need one? It wasn't hard to find references.
U.K. chemistry professor's article, "In any application where friction is important the diamond-coated tool bit will heat up and, in the case of ferrous materials (be it the tool substrate or the workpiece) the diamond coating will ultimately react with the iron and dissolve"
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SP3, manufacturer of PCD tooling, "Diamond is unaffected by almost every other chemical or compound in nature. One exception is hot iron. The carbon atoms in diamond will dissolve into the iron, quickly eroding the diamond surface."
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Materials science encyclopedia entry for diamond, "Diamond will react with strong carbide forming metals (i.e. tungsten, tantalum and zirconium). It dissolves in iron, cobalt, manganese, nickel, chromium and the platinum-group metals."
I have cut sapphire and other exotic stone with diamond laps. I never cut metal.
I have hand laps that are diamond - they are used in or with water and the action is slow. The diamond is either 'used', chips into tiny chunks or otherwise vaporizes in spite of the water.
Localized points of contact become very hot. Blue white hot. The diamond might burn up or change state and then get absorbed.
So I take it Im not supposed to use the red wheels when grinding aluminum or nylon?
Gunner
"The British attitude is to treat society like a game preserve where a certain percentage of the 'antelope' are expected to be eaten by the "lions". Christopher Morton
The red wheels, if they are the ruby red, are aluminum oxide, just as the old salmon colored wheels are. The choice in both instances would be silicon carbide, although I'm not sure that grinding nylon is done well with either of them.
I hope you're removing the leg before grinding the nylon, Gunner!
"The British attitude is to treat society like a game preserve where a certain percentage of the 'antelope' are expected to be eaten by the "lions". Christopher Morton
Norton is one of largest manufacturers and suppliers of abrasive products in the world. They may even be the largest; they claim so. I think it is safe to assume their engineers have completed at least two years of chemistry and physics and have come to a good understanding of the word "dissolve," but if you doubt it, you can call them and ask about their credentials. You can reach them at one of the numbers listed on this page:
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You might try reading some technical literature on the use of diamonds in cutting iron and iron alloys, including steel.
Your comment accomplished the opposite of your stated intent: it spread misinformation.
Here are some more references for you to debunk, if you have time:
Ok, Harold, you're right and I'm wrong. Hot iron dissolves diamond. It doesn't say that in any of my chemistry books and it doesn't say that in a chemical engineering book, it doesn't say that in my CRC handbook, although it says graphite is soluble in liquid iron. It says diamond melts above 3550 degrees C, but a reference on the net indicates that diamond breaks down at a much lower temperature. So maybe it breaks down to graphite and then dissolves into the steel.
In any case, there appear to be plenty of references in the tooling industry that iron and diamond don't work together.
As I already admitted in another reply, I was wrong about the silicon carbide wheels on small grinders. To answer your question, nope, I can't tell the composition of a wheel at a glance. The dry ones mostly look gray and the water or oil soaked ones just look dark. Although silicon carbide ones come in black and green, mine are black, just like silicon carbide wet/dry paper. I don't have a clue what the red wheels are as they aren't marked. I have sharpening stones, but of the two that retain their packaging, one says carborundum and the other says silicon carbide (unopened). Both are the same (of course) and are essentially the same color as my aluminum oxide grinding wheels. My packaged grits are silicon carbide and they also have the same dark grey color.
Actually, I think that diamonds only sublime. I'm not convinced there's a liquid phase of carbon, but I'm no chemist. This statement should open up another round, yes?
Yep. It's been long known that they don't.
That, as far as I know, is how you identify silicon carbide wheels, aside from reading the label.. In grinding wheels, I've never seen them in any colors except for green and black. I've long wondered why, because you can buy silicon carbide lapping compound in gray, as you've suggested. I'll eventually check my reference books from Norton to see if they address that issue.
I don't have a clue what the
They are usually aluminum oxide. Could be wrong, though.
That's the whole idea here. Share what we know. I commend you for your polite post acknowledging all our comments.
If a first or second year chemistry student told you that, it just emphasizes the old adage that a little knowledge is a dangerous thing. In fact carbon does dissolve in molten iron, forming a matrix of iron carbides. This is well known to metallurgists and chemists with more than a first year knowledge of the chemistries of iron and carbon. Certainly the engineers at Norton, the world's largest manufacturer of abrasives, know this.
On sublimation of diamond. Although 3550 degree C is listed as a melting point in several references some of the same references indicate that it actually sublimes. Still, these references don't fit what appears to be a valid reference that says diamond breaks down at a much lower temp, and that reference gave breakdown temps in the presence of oxygen and in the presence of nitrogen. I believe that was in one of Bob Powell's references.
Glad there are no hard feelings. I'm still having a hard time getting my head around the fact that none of my basic references say anything about diamond dissolving in iron or any other metal.
My lack of education makes it difficult for me to grasp the entire concept, but I wonder if what's happening at lower temps is the oxygen combines with the diamond to create CO2.
I'd like to think I'm a little better than that. I know when I'm wrong I'll willingly admit so, and offer an apology when required, and admire those that are willing to do the same. I detest those that slink away silently when they are wrong, refusing to even acknowledge the error of their ways. Takes a much bigger man to admit to being wrong, and for that you deserve, and have, my respect.
Looks like you do know how to "back out gracefully".
I'm still having a hard
That's likely because under normal circumstances it doesn't, unlike precious metals, that willingly migrate into some other metals when brought into intimate contact, even at room temperatures. Bear in mind that it's also a fairly recent discovery, although the phenomenon had long ago been identified, but perhaps not well understood. Same goes for silicon carbide dissolving in steel. . One of the references I have, which I am having trouble locating again, makes mention of the "phenomenon" of the abrasive apparently dissolving in steel, and they hadn't quite concluded exactly what the score was. The entire concept was not fully accepted as late as the mid 40's, apparently. Pretty much all the literature I have came from my grinding mentor, who was a journeyman grinder at that point in time. While he was not much as a machinist, he was an outstanding hand at precision grinding. That seemed to he his calling.
The reaction apparently requires considerable heat in order to occur. That likely explains why you find small drill pointers that run a diamond wheel, but likely at slow speed. I'm not sure about that, though.
Does it make you wonder if there would be a lot more diamond in the world if it weren't for the abundance of iron in nature? Could be diamond would have formed in lots of places had the carbon not been absorbed by iron.
At this point you are in the range of solid state chemistry.
I used to work with guys who 'did' solid state chemistry, for things like crystaline lighting phospors, and for ZrOx oxygen sensors. This was at GTE labs in waltham, mass.
Some of the guys had PhDs, and others simply worked in the lab and wore those funny pointy hats with stars and plantets on them. They also tended to have jars around with strange labels, eye of newt and jaw of toad, etc. It's a very strange discipline and most of it is art, to go along with a small amount of science. Things like 'fluxes' that work at 1600 deg C.
All I *can* say with some certainty is that a) one should not attempt to intuit the results of an experiment based on ordinary chemistry rules, and b) trust the experience of those who have worked in the field.
Jim
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John Doe posses an outstanding ability to describe his reasoning with such detail and yet make such a technical issue clear to the layman. He makes such a difficult task look so easy. A true indicator of a real porfessional. We should applaud Mr. Doe for his significant contribution to this thread.
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