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Grades Of Carbide

blake in spokane

Hot Rolled
Joined
Jan 11, 2008
Location
spokane
To those of us that do job/repair work & the stuff is junk before it comes in the door - Does the grade of carbide make any difference when chopping on a welded up shaft, torched burnout, inturupted cut, rusted crusted material, ect.? Will C2 know that it's steel not cast iron? Plus all the different grades the give us in the carbide catalogs. Or is carbide - carbide
 
Carbide..........

No carbide is not just carbide. I've used cast iron grades at slower SFM's to do a darn good job of turning hardened steels. I've also used PCD to turn carbide. Sometimes you can even get chips from the carbide like you were turning steel.

Try to use PCD to turn junk carbide grades and you'll find the difference in carbide grades!
 
There is a spectrum from abrasion-resistant tungsten carbides to crater/chip-resistant titanium carbides. Cast iron (and many non-ferrous) are usually machined with the tungsten grades, because they will last longer. Steel is usually machined with the titanium grades, because they won't break.

That's a big simplification, of course, even before you get into the bewildering array of coatings. Carbide grain size (thus the new "micro-grain" carbides) and binders make a big difference in strength and wear resistance. Also, the different between "cast iron" grades and "steel" grades isn't just about wear-vs-break; there are also some high-temperature chemistry differences. Compare the old ANSI grade system with C1-C4 for cast iron, and C5-C8 for steel, with the new ISO system with P50-P1 for steel, K50-K1 for cast iron, and also M, N, S, and H ranges for stainless, non-ferrous, superalloy and hardened materials. Have a look at the chart here.

If you're working on steel with flame-cut slag and welds, I would start with C5 or P50/P40 grade, or possibly a C1 or K50/K40, as those are the tougher grades of their respective ranges. C2 would not be as good a choice, but if it doesn't chip or break there's no reason not to use it for one-off jobs. If you had to pick one grade for your one-off jobs, I would go with a tough grade. It might wear down a bit faster, but it won't die as dramatically as a hard grade. However, grades at the tough end of the spectrum will usually not finish as nicely as the harder ones. So, no, carbide isn't just carbide.
 
There are a whole lot of differences in carbides. The difference in a 10% cobalt straight medium grain C-2 and a fine grain grade with 8% cobalt and 6% TiC and a little TaC can mean a 400% life improvement to a high volume user.
Knowing this arcane stuff is what they pay me for. :)

BUT , If you are gonna beat the crap out of it on one off stuff without optimizing feeds and speeds , and this seems to be what you are mentioning, any C-2 with a hone and a TiN coat will work just fine.

I have 30 years testing carbide and my shop can make any insert I want but when I'm going to whip off a simple lawnmower part on the old South Bend I grab a piece of uncoated C2 and go at it.

I would suggest some honed molded chipbreaker tools for roughing and some upsharp ground positive tools for light finishing cuts when you need to sneak up on that last 1 or 2 thou..

Bob
 
There is a spectrum from harder tungsten carbides to tougher titanium carbides. Cast iron (and many non-ferrous) are usually machined with the hard grades, because they are resistant to abrasion and will last longer. Steel is usually machined with the tough grades, because the hard grades will chip or crater.

Just to show that there is never any agreement on this the above is 180 degrees from what I would do.
Not trying to start a fight, just saying that different folks and differing applications find different things that work. :cheers:

You look at the way the tool breaks down and you change things based on that. If the tool never does the same thing for very long you don't get this option in which case cheap and tough usually works best.
Bob
 
There is a spectrum from abrasion-resistant tungsten carbides to crater/chip-resistant titanium carbides. Cast iron (and many non-ferrous) are usually machined with the tungsten grades, because they will last longer. Steel is usually machined with the titanium grades, because they won't break.


You are correct in that...Tungsten (C2) is for cast iron (and non-ferrous metals) and titanium based carbides are for steels, but titanium carbides are the more brittle ones. They have a higher "hot-hardness" and less abrasion resistance. I.E...Carbide bob is correct. This opinion is based on "expert" sourceS and personal experience.

Jeff
 
There's a zillion factors that contribute to success in cutting non homogenous materials where weld, scale, metallurgical inconsistancies like damage, hardspots, inclusions, (pick any or all) and rust prevail. The carbide grade in obly one. You also need a tool geometrically strong, stout shank, a rigid machine, and feed/speed parameters. I've cut risers off K-monel ring castings so hard and obdurate the upwards force of the work passing under the tool was sufficient to raise the multi-ton rail of a 6 ft King vertical boring mill against the restraint of the column clamps.

Sometime we got forgings with scale 3/16 thick mashed into the metal so its edges are encapsulated in solid steel. I've seen 1 1/4" dia x 3/8 thick round carbide inserts in a double negative holder with a 2" square shank reduced to crumbs in spectacular sounding failures that makes the whole machine shiver. The machine is a 48" American engine lathe about 18 ft between centers equipped with faceplate drive.

Once in a while comes a machining problem solved only by the consumption of many carefully chosen inserts and a lot of patience and persistance. A shrewd estimator bids these on time and material.
 
There are maybe 5,000 grades of carbide depending on how you count. (Brookes World Directory of Hardmetals etc.)

Tranverse rupture strength varies from 100,000 psi to over 500,000 psi. Rockwell varies from 88 to 94. Those are figures as I remember them. Some research will turn up more extreme cases.

Some carbide you can heat and bend. Other grades will snap under their own weight.

We regularly replace standard C-2 (whatever that is) with advanced grades that give ten times the life. This is for brazed applications but I'll bet Carbidebob can do the same for inserts.

Saying "carbide" is like saying "steel".
 
This is very intresting. Thank you much gentlemen for the info youve put on here. Besides searching this forum is there a guide one of yall might suggest that contains this info? Like a machinist handbook for cutters?

Do you ever see a need for carbide on alum.? We cut a lot of 5052,6061, ussually T6. We have a guy that insists on it. This old tool maker just uses 2 flute HSS.

I have invested no time in learning about this, I see that changing,

Thanx again

Steve
 
To those of us that do job/repair work & the stuff is junk before it comes in the door - Does the grade of carbide make any difference when chopping on a welded up shaft, torched burnout, inturupted cut, rusted crusted material, ect.? Will C2 know that it's steel not cast iron? Plus all the different grades the give us in the carbide catalogs. Or is carbide - carbide


To get back to your original question, C-2 will know when it's steel and not cast iron. That being said, if you are just roughing a relatively small area of a welded-up shaft, C-2 may do the job pretty well. C-5 would probably be a better bet if you had it laying around, but as Forrest Addy mentions, there are a lot of factors to take into consideration.

Jeff
 
This is very intresting. Thank you much gentlemen for the info youve put on here. Besides searching this forum is there a guide one of yall might suggest that contains this info? Like a machinist handbook for cutters?

Do you ever see a need for carbide on alum.? We cut a lot of 5052,6061, ussually T6. .......

On Alum. (uncoated) the preferred grade is C-3 or C-4.
Sometimes known as cobalt depleted grades as you mix in less cobalt than what is technically needed to bind the tungsten (this helps with welding and build up, strength suffers).

There are maybe 5,000 grades of carbide depending on how you count. (Brookes World Directory of Hardmetals etc.)

When it comes to carbide this is the bible but last time I talked to Ken, maybe 6-7 years ago he said there may be no more editions as he was wanting to retire and could not find anyone to take over. :(

C2's are tougher (higher TRS) will take a lot of abuse, C5's have additives (TiC and TaC) which help with chip welding and thermal cracking when cutting steel but break easier.
Outside of cermets, which are a whole different animal, there are no Titanium carbides, they are all tungsten carbide, some just have TiC added, something like 14% in a C8 grade.

The current trend is toward micrograin C2 with a coating to handle steel.
You vary the cobalt content to give hardness. Currently all commercial, (other than a couple "composite" grades), micrograins are C2 due to particle size and grain growth problems.

Every carbide manufacture is constantly trying to reduce the number of base grades pressed as cross contamination is a big problem.
Bob

Bob
 
So what is the finest particle size micro grain carbide for purposes of obtaining the sharpest possible polished carbide cutting edge? I know about "breaking in" edges, dulling the edge, chipping etc. Most interested in the finest grain size, strongest, hardest carbide composition that will give the smoothest polished surface and near razor edge sharpness. Toughness to resist chipping is important but for very fine cutting on an extremely smooth and rigid machine edge wear is the failure mode.
 
Sharp cutting edge is a myth taken from the add for Gillet. In reality, it is not achievable and its is not practical for metal machining. Second, THE EDGE is a line so it cannot have STRENGTH etc. The beta results in industry are achieved with so the0called edge preparation - applying small radius instead of sharp cutting edge. A number of standard methods and machines (for example Conicity) are used today. If applied properly, edge preparation normally increases tool life DRAMATICALLY. Please stop dreaming about a sharp cutting edge when you use 200 grit abrasive wheel to sharpen the tool or when you used indexable inserts.
 
Normally most of the times im machining welds insert costs are damn near irrelevant, the customer needs the part, can't get a new one so were manufacturing - aka weld and machining the old one. Using a $3 or a $5 insert or 2 is imaterial, the welding + time + machine down time is far more costly.

Generally i find edge hone - insert geometry to have far greater impact than the carbide grade. Often though that desicion is down to the insert manufaturers. I will normally switch to a different tool - insert combo to finnish ones im through the interuptions though!
 
So what is the finest particle size micro grain carbide for purposes of obtaining the sharpest possible polished carbide cutting edge? I know about "breaking in" edges, dulling the edge, chipping etc. Most interested in the finest grain size, strongest, hardest carbide composition that will give the smoothest polished surface and near razor edge sharpness. Toughness to resist chipping is important but for very fine cutting on an extremely smooth and rigid machine edge wear is the failure mode.


Strongest and hardest are opposites in carbide. More cobalt in the mix makes the tool stronger, less cobalt makes for a harder tool.
Real high cobalt content makes for good pulverizing hammers.
Low cobalt content makes for good fine finishing tools but they chip and break easily.

The primary advantage of micrograins is that cracks do not propagate as easily through them. Since the grains are smaller the cracks have to turn more times as they reach the boundary of each grain. This makes the tool harder to break in half. This is kinda simplified but hopefully you get the idea.

Until you are working with 2000-3000 grit wheels and very specialized machines grain size is not a problem for edge sharpness.

One of the things I see a lot on the net that always makes me roll my eyes is the statement that you can't get a razor sharp edge on carbide. This is absolute bull.

People see a 2000x picture of carbide structure and think "Oh yea, I see you can't sharpen it cause each particle falls out of the bond."
Ever look at a razor blade or a hand stoned piece of HSS at 2000x ? Kinda looks like a picture of the Rocky Mountains.

Fine grain carbides are at the 1-2 micron size. You need at least 1500x and very good optics just to see the particles.
Micrograins are 0.5 to 1 micron. This is approaching the resolution limit of any optical microscope made. The grooves from your 400 grit grinding wheel will span 10 or more grains.
Nanograin carbides, which are only used in very strange circumstances due to their cost, can only be seen using a SEM.

Getting a sharp edge is all about grinding technique. The wheel must enter the part at the cutting edge keeping the material in compression.
If you surface grind a piece of flat carbide and look at it under a reasonable magnification the right edge where the wheel is entering the part will be clean and chip free (assuming a good grinding wheel and good coolant flow).
The trailing left side of the part will be chipped. The size of these chips will depend on the wheel being used but they will be 10 to 100s of grains in size.

Every few years I'll see a rookie at the sink, red paper towels everywhere, and a trail of blood on the floor leading back to his machine.
I'll say "What happened?" and inevitably the answer is "I wiped off the edge on one of the finishing blades with my finger".
I give them the where were you when they passed out the brains look and ask "Who wants to drive numnuts to the hospital so they can stitch up his fingers?".
Bob
 
I have my own carbide insert fabrication shop.
We do mostly automotive work with a little sprinkling of jet engine and oil field stuff along with outsource specialty grinding work for some of the big guys.
Bob
 
Bob, I believe your experience with carbide is similar to mine. My question is who makes the best finest micrograin carbide etc. that allows the best polished top and edge. The best I have used some years ago was an experimental grade from Kennametal. Very careful grinding at the roughing stage and lapping similar to making single crystal diamond tools worked well on that X grade. I am sure there is better stuff out there now as that was micrograin carbide before it became generally available. I am back to doing a project similar to one that required special tools so I am wondering who is on top these days. Do you have the capability to make micrograin brazed 3/8" shank tools with very close radius tolerances?
 
My first thought hearing interrupted cuts and slag and such was to give cast materials like Stellite, Tantung or Blackalloy a try. They tend to work well under abusive conditions. That company referred to above, Stellram, has a name that suggests they do some form of Stellite. Reading their site they're careful not to mention it, but they're also careful not to pin down any materials other than saying "tungsten based products". I wonder if they make cast alloy inserts, since the above mentioned materials are all tungsten based.

Conrad
more cast alloy info here
 








 
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