Guhring oHG - Carbides

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Carbide is currently the most important tool material in the metal working industry. In order to meet the high demands and using up-to-date methods, i.e. the sinter HIP process, we produce our own carbide for our tools. Our own carbide factories enable the development and application of the optimal carbide grade for our tools. We guarantee highest, porous-free qualities.

In particular, the following 6 carbide grades are applied in producing our tools:

Classific. to ISO 513	Range of application	Hardness [HV30]	Composition in %	Grain size [µm]	Bending strength (N/mm²)
K10	superhard, suitable for the application on extremely rigid machines; preferred application: reamers.	1870	92,0 WC 6,0 Co 2,0 TiC/TaC	< 0,7	3000
K20	hard, especially suitable for the machining of abrasive materials on rigid machines	1700	90,5 WC 8,0 Co 1,5 TiC/TaC	< 0,7	3200
K10/K20	developed from the classic K10/K20, equal hardness, but with a considerable increase in hardness	1620	94,0 WC 6,0 Co	< 1,5	2500
K40	top grade with ultra-fine grain, universal application; this high quality carbide is used for all ratio drills, taps and milling cutters produced to K quality.	1620	90,0 WC 10,0 Co	< 0,5	3700
P25	carbide grade with extreme heat-resistance, especially suitable for dry machining	1520	73,5 WC 9,0 Co 17,5 TiC/TaC	< 2,5	2300
P40	universal grade for the application on less rigid machines or interrupted cutting	1420	77,0 WC 11,0 Co 12,0 TiC/TaC	< 2,5	2500

The DK grades

consist primarily of tungsten carbide as the "hardening agent" and cobalt, the "binding agent." Regarding hardness and toughness they are superior to the DP grades. Because of the diffusion and seperation process between the hot chip and the DK carbide, built-up edges and cratering may occur, especially when machining steel . This disadvantage can be eliminated by coating the tool.

The DP grades

were originally developed for the machining of steel. Its tendancy for built-up edges can be reduced by adding TiC and TaC. These mixed carbides improve the oxidation resistance at higher cutting temperatures, but are less though. Exaggerated, DP grades currently only exist because of the fact that tools, after regrinding, often cannot be re-coated by user.

The table lists the most important and the most popular carbide grades in practice and are in order of decreasing hardness. Their sensitivity to chipping has yet to be determined and should therefore be considered as a subjective assessment. However, the sensitivity to chipping depends a great deal on the grain-size of the carbide. There is a definite tendancy towards smaller and finer grain-sizes. Cutting tool manufacturers and users gain 2 important advantages from that:

The smaller the grain size, the tougher the tool, making it possible to apply in unstable conditions.
Considerably sharper cutting edges are possible with smaller grain-sizes. Carbide tools will therefore one day be able to machine exactly like the HSS tools, producing even better hole surfaces and run at lower speed and feed rates than where it was previously necessary to detach the chip efficiently.

DK-carbides have the following grain-sizes (unfortunately not yet standardized):

2,5 µm	>	normal grain size	>	1,5 µm
1,5 µm	>	fine grain	>	0,7 µm
0,7 µm	>	finest grain	>	0,5 µm	(Guhring description = F)
0,5 µm	>	ulta fine grain	>	0,1 µm	(Guhring description = UF)
0,1 µm = 100 nm	>	nano grain

Currently, DP-carbides cannot be produced smaller than 1,5 µm.