jdm61
itinerant metal pounder
- Joined
- Aug 12, 2005
- Messages
- 47,357
Thus my question about it effectively not being tempered. What would the expected as quenched hardness range of the 8670 be?
Never a break from tough questions around here.
Some hardness tests, like Vickers are basically linear with tensile strength:
Rockwell C hardness, however, is not:
I don't have a tensile strength conversion above 60 Rc, so here is a plot up to 70 Rc comparing to Vickers which is similar to the plot above but to higher hardness:
However, even a curve is more or less a straight line if on a small enough scale. And in the 58-66 Rc range we are talking about, the trend is very linear:
Therefore I wouldn't be too concerned about there being greater increases in strength from 61 to 63 Rc than from 58 to 60 Rc, as the difference is pretty small.
As it turns out, toughness often starts to level off at high hardness, rather than an acceleration to zero. One example is the CruForgeV data I posted before. Or in this data on Vanadis 4 Extra:
Therefore I maintain that the low toughness value for 8670 at ~64 Rc was due to insufficient tempering and not due to an inherent hardness effect.