Please explain 'solid carbide'

[itrade]

In hardened steel we talk of carbides and things. I'm still learning that stuff. But one issue eludes me:

Drill bits and saw tooths are listed as 'solid carbide'. Is it really? Or is it just steel with a high percentage of carbides?

How do you make a 'solid carbide' bit?

In general I'm just lost on this subject.

Steve

 

[mete]

The carbide drill bits , cutting tools etc are not steel. Nor are they 'solid carbide'.The carbides are made of grains of carbide, often tungsten carbide, 'glued' together with cobalt. The cobalt may be as much as 15%. These pieces of carbide are then brazed onto a steel shank to make the drill etc.

 

[Laredo7mm]

Here is what i found:

"Carbide is a cemented matrix of tungsten carbide particles in cobalt. The formation of the tip material is similar in concept to concrete in which sand and gravel are cemented together with a limestone clay mixture. In carbide, the tungsten carbide particles are embedded in cobalt. To manufacture carbide, the tungsten carbide particles are first mixed together as fine powders and heated to 2700-2800 degrees F. Once the tungsten and carbide have combined, cobalt is added and the mixture is subjected to pressures in a die of up to 30 tons. The resulting tools shape is then heated in two stages (presintering and sintering) in an atmosphere controlled furnace to achieve final hardness."

Like what Mete said.

 

[fitzo]

I worked in research on these things at one time many years ago. Hardnesses on these tools are usually in the high 80's Rc and often at 90. Hard stuff. As mentioned, after press-forming to shape in the presence of some type of volatile parafin-like binder, the pieces were heated in a vacuum furnace to the point the cobalt melted, surrounding the tungsten carbide crystals, thus "cememnting" them into a lathe bit, drill bit, or tire studs (for us old farts who remember 'em).

In drilling applications, they are meant to work at higher speeds. I kept some drill bits that are finer than a needle, meant to run at 100,000 RPM. I have no idea what they were used for.

They have far less strength laterally than HSS steel drills(transverse rupture strength), and break easy. Have to have your drill table nice and perpendicular to the axis of the drill. Not good for hand drilling. Mills have to be fed just right to not break the end mill.