S390 steel

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LostCause

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So I decided to make drastic move.

I sold stuff I don't need and financed so called "grail".
So I placed order for a custom. Steel I picked is S390.

So I have larger fixed blades in 3V and SK5 and now S390 coming.

So, what should I expect from S390 steel? I know it's different from K390.
 
Never used it, but on paper it doesn't look far from Rex 45. Lots of W (can be run hard - ask your maker what he'll do, he can probably go beyond 65 HRC), a little less than 5% Chrome, so you don't have to worry too much about corrosion (think M4, for instance).
 
LostCause said:
So I decided to make drastic move.

I sold stuff I don't need and financed so called "grail".
So I placed order for a custom. Steel I picked is S390.

So I have larger fixed blades in 3V and SK5 and now S390 coming.

So, what should I expect from S390 steel? I know it's different from K390.
Click to expand...
As ferider suggested, it will depend on how it is heat treated. Similar to T15.

With a proprietary heat treat from Roman Case, that steel has out cut Maxamet and will strop back on plain cardboard. Not sure who else is running that steel, but it is certainly capable. You can PM me and I can send you some Youtube links (not mine). I would include them here, but don't want to violate any rules.

Here is a link from BF with some input from Larrin: https://www.bladeforums.com/threads...th-s390-possible-competitor-for-k390.1749142/
 
ferider said:
Never used it, but on paper it doesn't look far from Rex 45. Lots of W (can be run hard - ask your maker what he'll do, he can probably go beyond 65 HRC), a little less than 5% Chrome, so you don't have to worry too much about corrosion (think M4, for instance).
Click to expand...
He goes for 66-67 HRC range. It is a medium sized fixed blade.
That steel is usually heat treated at 68 HRC and at that hardness it has higher toughness than K390 from what I've found.

Also if it's similar to T15, then it also has basically double toughness than 60/61 HRC D2 steel while at that hardness.

I am interested to see how it'll behave in use.
 
SCTorrero said:
As ferider suggested, it will depend on how it is heat treated. Similar to T15.

With a proprietary heat treat from Roman Case, that steel has out cut Maxamet and will strop back on plain cardboard. Not sure who else is running that steel, but it is certainly capable. You can PM me and I can send you some Youtube links (not mine). I would include them here, but don't want to violate any rules.

Here is a link from BF with some input from Larrin: https://www.bladeforums.com/threads...th-s390-possible-competitor-for-k390.1749142/
Click to expand...
That steel is used by some Swiss, Ukrainian and Russian knife makers.

I saw youtube videos of them batoning nails and cutting glass with it and having no edge damage. Certainly looks promising.

I just read Larrin's imput. Thank you for posting.
 
Larrin said:
S390 is basically T15 with a little higher Co and Mo. That would give S390 a little higher potential hardness and a little lower toughness. In fact Bohler makes T15 as S393 so you can compare the two with their rating system: https://www.us.bohler.com/app/uploads/sites/92/2022/06/productdb/api/s000en.pdf

I tested CPM-T15 and posted the results here: https://knifesteelnerds.com/2021/05...eels-xhp-spy27-maxamet-rex-45-420-t15-rex-76/
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Thank you for response.

Upon checking Bohler data, S390 seems to have more edge retention than S393 without differences in toughness.
Bohler however did rate K390 as both, more wear resistant and tougher than S390 in cold work processes.
That could be due to these steels having different working hardness, K390 being around 64 HRC and S390 being around 68 HRC.

I decided to speak to few knife makers who use both steels, response was that due to these steels having significant Chromium content (4-5%) tungsten mainly forms softer W6C carbide that doesn't add much to wear resistance. Both steels have vanadium which forms VC vanadium carbides that contribute to wear resistance.
K390 having twice as much vanadium paired with higher carbon content is likely reason why it has better wear resistance.
Apparently, S390 has the edge in red hot hardness which is irrelevant to knives. But being put at same HRC, S390 will be a bit tougher.
One of the makers said that he prefers S390 due to having better edge stability than K390.


I went for S390 because particular maker usually makes this knife in S390 (I just asked for few other things on my knife being done different). It is around 14cm long blade, at around 5mm thickness and is full tang. Hardness range is 66-67 HRC. I think that the toughness should be more than enough for normal use.

I am however interested to hear your opinion about it.
 
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