Is anyone still using S90V ( CPM 420V ) ?

Don Powell · Sep 27, 2003

Now that S30V is so commonly used, is any one still using S90V?
I know that one of the drawbacks of heat treating this steel is
the need for higher austinizing temps ( 2050 - 2100 F ). Paul Bos
could only get the steel up to HRC 57-58, while people like Phil Wilson were using it at HRC 60. So, is it ok at 57-58, or who would be
reccomended to heat treat it to rc 60. I talked to one of the metallergist at Crucible, a long time ago, and she said that to get high hardness that oil quenching or salt quenching was needed.
S90V at HRC 60 sounds very good for a folder. Any thoughts on this?

Darrel Ralph · Sep 27, 2003

Hi,
I still use it .
I still like it !
I would go with crucibles recommendations the hardness.
CPM-S90V is very tough!

John Andrews · Sep 28, 2003

I still have a hundred bucks worth of CPM440V, and I definitely like the stuff! I am saving what I have left for a couple of special knives, since it is about 1/4" precision ground stuff. I am guessing Phil is doing his own HT.The steel cost me $160 for 2 pieces of 18", after I told Crucible I wanted a 36" length. Crap, I needed it for a customer knife, and it took so long to arrive I had no choice but to accept it. One thing I did like, the steel arrived with good paperwork with the steel composition description.

tom mayo · Sep 28, 2003

the stuff is awesome!!!

Don Powell · Sep 28, 2003

John, are you saying that you have CPM 440V or CPM 420V? I was refering to 420V ( S90V . I was given a piece of S90V to try and was stopped when I learned that Paul Bos could only heat treat to Rc 57-58. I had remembered that Phil Wilson had used it at Rc 60 and when he did edge holding test, lower Rockwell numbers yielded much poorer edge holding in real world use. High hardness prevents rolling and blunting of the edge, a major cause of loss of sharpness, even though the steel has very high abrasion resistance.
I cannot heat treat myself, so where do you have it heat treated? Do you do it yourself?

John Andrews · Sep 29, 2003

Don, it is CPM440V, and no, I don't HT it myself. I THINK it was ol' D'Holder, but I will have to check my records.I understand it has to have the cryo treat also, which is way out of my reach. I bought the steel through DO-ALL, an outlet for Crucible. They have outlets all over the country, one about only 75 miles from here. One other thing, they sure did not like dealing with a small order such as mine, 36" and to them the low sum of $160. How beneath them! They can go jump before I ever order from them again!

rlinger · Sep 30, 2003

Don, if you have some of it send me a small sample (1 inch long) and I'll be happy to see what I can do with it on HT. I think deep cryo will be essential in attaining the hardness you wish. I can do that part too. I'll just stick it in there with my next Eastern turkey

.

If we are happy with the results I'll HT your blade if you like.

Roger

rlinger · Sep 30, 2003

Don, the Crucible data sheet is telling me to temper no lower than 400 F. but for better wear resistance a minimum temper of 500 F. should be employed. They spec a aim hardness of no greater than HRc 59 for the specs they outline. I have learned to pretty much trust Crucible data sheets and am sure I can hit their aim hardness but may not be able to acheive the 60 you wish to have. In addition, I can go to 2100 F. - within their recommended austenitizing temp. - and I would prefer to take their advise and not temper below 500 F. (in favor of better wear resistance, as they suggest). In short, I suggest I would probably fall short 1 point of what you want. Without ever working with S90V before, I think I can hit 59 but not 60. In fact I may have to temper at 400 F.,below the recommended optimum minimum, to achieve 59. Just my guess based on the trust I put in Crucible's data sheets.

I am not at all recending my offer to you. I am very happy to test a small piece of it for you.

Roger

Don Powell · Sep 30, 2003

Roger, you are incredible. That is very kind of you to offer to heat
treat this. I suspect that you are very eager to learn as much as you can about different alloys and from what learned about Phil Wilson's experience with S90V at Rc 60 or so it would be a great steel to try.
I met Maria Sawford at a family wedding and found that she is, or was a metallergist at Crucible. She had Crucible send me a 18" piece of S90V. In a letter from her, this is what she had to say about heat treating. " The typical application hardness of CPM S90V is 58/60 HRC. We suggest that the heat treatment should consist of austenizing at 2100F for 10 min, oil quenching and tempering for 2+2hr at 500F of maximum corrosion resistance is necessary. If you temper at 500F, you should consider a sub-zero treatment at -100F 1hour to minimize the retained austinite content. Normally the sub-zero treatment is applied between the first and second tempers to reduce the risk of cracking although it is more effective after the quench but the risk of cracking is somewhat greater." Quote from Maria K. Sawford, Reearch Engineer, Crucible Materials Corp.
Roger, if you think you might benefit from this experience, I will send you a piece.

rlinger · Sep 30, 2003

Yeah, send me a 1 inch long piece. I'll deep cryo directly after quench and then do two consecutive 2+ hour 500 F. tempers. I'll Rockwell it and send it back to you if you want to check the grain structure for yourself. It sounds like she thinks you can aim for 60 RHc by tempering at 500 F.. That would be nice. If we like the results my invitation to you is still open.

On second thought, if you can spare two 1 inch long samples I think it would be good to find out the Rockwell difference between cryo before first temper and cryo between temper 1 and 2. From what she seems to say it looks like I may be able to hit 60 on the cryo before temper. I believe more austenite will be transformed by cryo before temper. I do this with all my stainless now because Paul Boss has advised me to and SO FAR I have had no noticible fractures.

Roger

Cliff Stamp · Oct 1, 2003

Just a note, last I heard Phil was running it at ~62/63 HRC.

-Cliff

Don Powell · Oct 1, 2003

Roger, thanks very much. I will send you the two pieces. I am installing a new furnace tomorrow, and I won't get to it till the weekend. Cliff, thanks for the info. A couple of years ago, when I noticed that Phil Wilson ran his knives quite hard, I wrote to him and he informed me that he did not have any problems with chipping. I do know that he considers the use for his S90V knives to be only for slicing. I wonder how he achieves that level of hardness. Must be very high austenizing temps ( > 2150F ) and interrupted oil, molten salt or something like that.
Roger, check your mail.

Cliff Stamp · Oct 2, 2003

They are very specialized knives, it will chip easily at that hardness and isn't an inherently very tough steel anyway. The blade do have very high soak temps, oil quenched followed by deep cryo in liquid nitrogen.

-Cliff

John Andrews · Oct 2, 2003

In one fine article Phil wrote he had a fellow in a chicken packing house using one of the CPM knives of his. It was for a long work period. When the knife was returned to Phil there was, I beleive, a dime size or so round chip in the blade. It was kind of a puzzle why the knife chipped the way it did, and the location of the chip was a little suspicious to him, if I remember correctly. Phil has written some other examples of the same steel blades,In Knives Illustrated. Phil's trek with the CPM steel is a very interesting saga. True, Phil makes a pretty hard blade, but his blades perform great for slicing chores and dressing large sea fish and salmon.

Cliff Stamp · Oct 2, 2003

Yes I have used one of his fillet knives in S90V it was when he was first running it so it was rather soft at 59 HRC. I have also use a light utility knife from him in CPM-10V at 62 / 63 HRC. Very nice for what it is designed to do.

-Cliff

Jason Arnold · Oct 3, 2003

I use S90V. More so than any other stainless even. Get a pretty accurate 59HRC. Can get it harder if need be.

Don Powell · Oct 5, 2003

I want to thank all of you who have responded to this thread. I want
to especially thank rlinger who has offered to heat treat two pieces of S90V, to evaluate the process and the resulting HRC, and then heat treat two blades. Some of you have said very good things about this alloy. What can I expect from this alloy, heat treated to HRC 60, with liquid nitrogen soak, used for a folder for everyday cutting chores. I have never used my EDC knives to pry or chop. If I whittled hard wood, would the blade tend to chip out. Could I strip wire without expecting damage? I am familiar with the charpy values attributed to this steel, but in my experience, some of these numbers don't seem to correlate to what can be done to the knife blade. For example, D2 should not be used to chop, but at HRC 60 ( Paul Bos heat treat ) I have used a couple of knives to chop many, many limbs, saplings to drag deer and so forth. Never any damage, maybe I was lucky! The blade geometry was fairly robust though, I must say.

Jason Arnold · Oct 5, 2003

One of my customers spent several hours carving wood with one of my S90V kogatana. No chipping or signs of wear for that matter. That knife was at 59/60HRC. Twisting and all. I use a "zero" edge on just about all my knives too.

rlinger · Oct 5, 2003

Don, I received the S90V sample pieces yesterday (Saturday) in good order. I was going to heat treat today/this evening but checked my LN level and it is finally evaporated. As I said before, I did not expect to be able to HT until last of month and now that is for sure since I will get my dewar refilled after I return from bow hunting.

RL

rlinger · Oct 6, 2003

Got the dewar refilled today. Am ramping the oven now. Will have two preliminary test results this evening: one 'as quenched' and one 'after first temper'. I will deep cryo one test piece before temper and the other between tempers. I will austenitize @ 2100 F. for 20 minutes (foil wrapped) and rapid air quench. The two tempers will be @ 400 F. for 2 hours 15 minutes per. Cryo will be LN for a minimum of 12 hours and a maximum of 18 hours and will be specified later. I am air quenching instead of oil quenching because of the foil wrap and because that is the way I would do it if they were blades. One other piece of info: both test pieces are in the same packet and will be quenched together.

RL