Tempering

[rmatel]

If steel is not tempered after heat treating it is brittle. More or less brittle than a solid carbide tool? I'm thinking specifically about drill rod ( oil, air, water), but expand the discussion if you feel so inclined.

[Rotate]

Carbide is harder than hardened steel.

Albert

[SGW]

Carbide is certainly harder; not sure about relative brittleness though. I suspect that fully quenched, fully hardened steel is more brittle than carbide. Guessing again, I'd say water hardening is likely to be the most brittle when fully hard, but I don't know for sure.

[Thrud]

Water hardening only gives a thin layer on the surface similar to case hardening with a hardness of about RC62 - don't use with any threaded parts as it will most likely fracture in the threads. O-1 is better for threaded parts.

Carbide is from 90-99 on the Rockwell C scale. Carbide has better torsional properties than steel so it is used in boring bars where overhang exceeds 10:1. It also absorbs vibrations better and is also used in "tuned" boring bars exceeding a 10:1 overhang. The toughness of carbide depends on how much other heavy metals and carbides are alloyed with it. The toughest inserts use Silcon Nitride wisker reinforcing (the most expensive ones). A new super tough grade of carbide inserts is being developed to replace HSS all together and might be out in a few years. Carbide can shatter just like glass when broken (trust me).

Tempering softens the metal in a controlled fashion to give desirable properties such as impact toughness, or flexibility.


[This message has been edited by Thrud (edited 03-22-2002).]