Thought on SK-5 steel

[hardheart]

1080 can have up to 0.88% C

Neither Cold Steel nor any heat treatment method has anything to do with the name SK-5. SKD11 is another name for D2, doesn't matter how you heat it.

Carbon V was 50100B/0170-6C. Camillus probably did the CS blades the same as the Beckers and pretty much every other knife made of this steel. There really wouldn't be a need for separate heat treats from one factory for one steel on a similar fixed blades. Who knows how flexible the Taiwan factories are in processing the steels.

 

[hkpokes_you]

No Hardheart -- you got it backwards. The old JIS name for AISI 1080 was SK-5 -- or, rather, they allowed Americans importing steel to call their AISI SK-5 -- but the AISI regulations would not let you sell SK-5 of the sort that you saw on that spectrometer readout as 1080; AISI allows for between .75 and .88 carbon in steels sold as 1080 -- but that SK-5 was clocking in at at least .9 (it looked a little higher than that to me -- if anything it is more typical of 1090 melt).

The SK-5 shown does look like it meets the limits on S, P and Mn for AISI 1080 -- but AISI does not list a range for the max Si you can put in an alloy. I'd think that you'd have to call something other than 1080 if it had a composition like that...and you'd probably want to...you would get a cleaner melt with less oxidization because of the Si. You'd also avoid case-hardening the piece after quenching because the Si in that range is a good ferrite strengthener.

Edit: Also -- the particular 420HC heat treatment I was referring to involved a well-thought-out cryogenic treatment; as with everything, I imagine that the good stuff costs a little more -- not everyone wants it -- and some people pay more to get the better HT.

Edit 2: Okay here is the final scoop -- JiS lists the typical carbon range for SK-5 as between .8 and .9 -- and the typical Si content as .35. This makes SK-5 most similar to 1086 -- which is between .8 and .93 C -- and a Si range (if it has any) of between .15 and .30.

So, basically -- SK-5 is most similar to 1086 with a dash of Si that AISI deems worth our taking note of...

 

[hardheart]

What did I get backwards? I looked in my ASM Heat Treater's Guide, and on page 204, it says 0.75-0.88 C for 1080.

 

[hkpokes_you]

JIS let you call anything with .8-.9 carbon SK-5; but you can't call SK-5 AISI 1080 because it has too much Si.

The carbon range for 1080 is .75 to .88 -- and the Si range maxes out at .3 (though you don't NEED any at all to have 10xx).

The carbon range for SK-5 is .8-.9 -- and the industry standard is to have .35 Si -- but they aren't as anal about calling high Si melts of AISI alloys within the .8 to .9 C range SK-5.

Despite this -- we are aren't 'nice enough' to label their steel by our name.

.35 Si is a little too high to be an AISI standard carbon steel. And the carbon range of SK-5 is more typical of 1086 melts than 1080 melts.

Not a big deal...but this seemed to be a cause of confusion before.

 

[Gator97]

JIS let you call anything with .8-.9 carbon SK-5; but you can't call SK-5 AISI 1080 because it has too much Si.

All the sources I have seen list SK-5 as AISI 1080 equivalent. Japanese or US or any other steel name crossreference table.

The carbon range for 1080 is .75 to .88 -- and the Si range maxes out at .3 (though you don't NEED any at all to have 10xx).

As far as I have seen no AISI source had Si specified for 10xx series. Where do you get the 0.3 Si from?

Despite this -- we are aren't 'nice enough' to label their steel by our name.

It(SK5) sure gets listed as 1080 all over the place.

 

[hkpokes_you]

Okay...I'm sorry if it came off like I was trying to start stuff with you guys. I like your posts, and regret it if I'm coming off like a punk. I found one manufacturer that listed their Si content for SK-5 as .35 -- the range for Si in SK-5 seems to be .15-.35 according to JiS standards.

Here's the clearest table I could find in the public domain; thanks to the Tenhiko Corporation:

http://www.tenhiko.com/search/zairyou/tokushukou/tanso.html


US standards for Si content seem to allow for between .15-.30; that isn't a requirement on 10xx alloys -- to clear up confusion -- that's just the level of Si you see in Si-killed rather than Si-alloyed steels; by the same logic they'd probably list max Al content at .005 -- the level you find when Al is added as a deoxidizer -- but, I mean, that's really a fairly minuscule amount -- they probably don't list it because it's probably not the sort of thing you're going to detect unless you are looking for it in specific...