Adam. Edgehopper. S5 isn't much of a steel at all. Its' main problem is lack of wear resistance. What do you expect from a steel with a composition of C 0.6, Cr. 0.25, V 0.2 and Mo 0.3 ? There is not much good stuff there; it is a low alloy steel.
Go back to your Cold Forming Tool Steel chart and see how M2 or M4 compare with S5; each has much more abrasion resistance than S5. Here, you probably say, 'but Dr. Walt, look at the toughness of S5.' Well, Adam, that IS what the chart says, but remember that BM brought out AFCK's in M2 because they were tougher than ATS-34?
Now go to the plastics tooling table and take a look at CSM-21. WOW!! This has toughness off the scale! Even better than S7, which is the same as S5! Well, Adam,
CSM-21 is 15% Cr, Ni 4.0, Cu 3.5, Mo 0.2, and C of 0.02 !! This is a steel very similar to the 18-8 stuff they use in flatware. Note that the Rc is 33-42 typical.
So toughness, which is difficult to measure anyway, is even more difficult to use to determine how a steel will perform.
Also, go back to the Cold Forming Tool Materials chart and look at CPM 9V, 10V, and 15V. Notice something? Right! As the wear resistance goes up, the toughness goes down. This is frequently the case. Further, the toughness is really only a SWAG, as the heat treatment can have a dramatic effect on the steel.
CPM manufacturing is designed to allow for greater amounts of alloy ingredients to be present throughout the steel, especially carbides. These steels offer significant advantages over traditional ingot cooled steels, which tend to allow the components to separate out.
S5 steel is an old fashioned ingot steel, which was good in its' time, but is hardly cutting edge (groan) now.
I am having a Kit Carson folder made from CPM 420V, and another poster has chosen CPM 10V. Why don't you give me your views on these two choices? See you, my friend, Walt
As always, any comments, questions, suggestions or criticisms welcomed. WW
