Cobalt said:
If you are looking specifically for toughness, bainite in that class of steels is much tougher than martensite.
Also, I don't think S-5 is made any longer so you would have to settle for S-7.
Timken still lists it and has data sheets on it.
Razorback - Knives said:
The higher the rc is the more prone to chipping.
Steels have a complex relationship between hardness and toughness, both in terms of ductility and ability to resist impact. There are several embrittlement zones through the temper range due to carbide and impurity segregation along grain boundries which makes steels more brittle, not less, as they are tempered softer. Most steels have a performance peak very close to their maximum hardness.
As a steel is softened it is also made weaker and even if it becomes more ductile and able to resist impact, it will now yeild sooner and the ultimate tensile point will be lower so the edge will tear off at a much lower force. Thus underhardening a steel to get toughness is usually a poor idea. This was well discussed on Swordforums including relevant stress/strain graphs by Lee Cordochorea :
http://forums.swordforum.com/showthread.php?s=&threadid=55349
Also a very thin grind and edge.
Steels are more flexible when they are thinner because the strain under a given stress is proportional to the thickness of the steel. Kevin Cashen has discussed this in detail on swordforums, it is why very thin edges will easily pass brass rod type tests and very thin blades will flex to extreme angles without taking a set and go much further before breaking.
As you reduce cross section absolute strength and durability of course decrease, however failure will start to become more brittle in nature. For example while it is easier to bend a ATS-34 blade 1/8" thick, it will bend to a much larger angle than one 1/4" thick which will crack at a low angle. Edges behave along the same principles, thinner edges tend to deform while thicker ones tend to chip when overstressed.
Overthickening an edge to get durability however is just as bad as underhardening it, now you give up cutting ability and ease of sharpening (and for stainless often corrosion resistance). Choose a more suitable steel, Bryson notes this in his book on steel selection as do most books on tool steels.
-Cliff
Was cutting roots and some pebbles snuggled the edge. Stupid pebbles.
