Sandvik 13C26

he said in solution, meaning chromium not tied up in carbide, that is the chromium that adds to corrosion resistance. 420 has so much chrome in solution because it has so little carbon.
 
Hi, Cobalt. Not to step into the middle of something here, but notice that Larrin was discussion chromium in solution, which of course is different than chromium percentage in the untreated alloy.

Edit to add ... hardheart beat me to it.
 
Larrin said:
If you look at the amount of chromium in solution, you'll see that they stainless steels don't vary much after heat treatment. 12% chromium in solution is a whole bunch for most steels. D2 only has around 5-8%, for example. 13C26 typically has 11-12% depending on the heat treatment. 154CM has only 10.5%, but makes up for some of that with a large amount of molybdenum. 440C only has about 12%. 440A and 440B have more. 420 has almost all of its chromium in solution, which is why it is so corrosion resistant even though it has low chromium.
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Larrin I understand your argument: Since 13C26 has a lower carbide content a greater percentage of its chromium should be in solution and available to modify the oxide layer rather than tied up in chromium carbides and unavailable for passivation. (But I also hear you saying that 13C26 is lower in corrosion resistance than 440A.)

What is your source for the %Cr in solution for the different alloys?
That's good boogie.

add: DOW and hardheart both beat me to it.
 
knarfeng said:
Larrin I understand your argument: Since 13C26 has a lower carbide content a greater percentage of its chromium should be in solution and available to modify the oxide layer rather than tied up in chromium carbides and unavailable for passivation. (But I also hear you saying that 13C26 is lower in corrosion resistance than 440A.)

What is your source for the %Cr in solution for the different alloys?
That's good boogie.

add: DOW and hardheart both beat me to it.
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The main one is the Verhoeven book, you can also find some in the Crucible patents and data sheets.
 
Cobalt said:
http://www.calphad.com/martensitic_stainless_steel_for_knives_part_1.html
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http://www.calphad.com/martensitic_stainless_steel_for_knives_part_1.html

The austenite composition for AISI 440C at 1000°C (1832°F) is found at the point where the tie line drawn through AISI 440C intersects the carbon saturation line. It is worth noting that even though AISI 440C alloy contains 1.075 percent of carbon and 17 percent of chromium overall, the austenite that forms at 1000°C (1832°F) contains only around 0.3 percent of carbon and 11.7 percent of chromium (see Figure 1).

http://www.pfonline.com/articles/clinics/0402cl_clean1.html

;)
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it will experience very poor corrosion resistance due to the formation of iron carbides and iron-chromium carbides. The material in the vicinity of the iron-chromium carbide is depleted of chromium and is technically no longer a stainless steel (in those localized areas that have experienced chrome depletion)
 
knarfeng said:
Larrin I understand your argument: Since 13C26 has a lower carbide content a greater percentage of its chromium should be in solution and available to modify the oxide layer rather than tied up in chromium carbides and unavailable for passivation. (But I also hear you saying that 13C26 is lower in corrosion resistance than 440A.)

What is your source for the %Cr in solution for the different alloys?
That's good boogie.

add: DOW and hardheart both beat me to it.
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I would be interested as well, as those numbers seem very low. I know that the solution numbers are lower, but didn't think they were anywhere near that low.
 
hardheart said:
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The austenite composition for AISI 440C at 1000°C (1832°F) is found at the point where the tie line drawn through AISI 440C intersects the carbon saturation line. It is worth noting that even though AISI 440C alloy contains 1.075 percent of carbon and 17 percent of chromium overall, the austenite that forms at 1000°C (1832°F) contains only around 0.3 percent of carbon and 11.7 percent of chromium (see Figure 1).



it will experience very poor corrosion resistance due to the formation of iron carbides and iron-chromium carbides. The material in the vicinity of the iron-chromium carbide is depleted of chromium and is technically no longer a stainless steel (in those localized areas that have experienced chrome depletion)
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exactly, but is there one for 13c26?
 
My numbers were off the top of my head, but you guys can read the Verhoeven book (which gives numbers mostly at 2000F austenitizing temperature which gives higher chromium numbers than typical), as well as the Crucible patents and data sheets, which usually gives the chromium in solution after the recommended heat treatment.
 
I think 13C26 & AEB-L were designed to lie on the critical tie line, where there is 0.6 C & 12 Cr in the austenite.
 
Thanks, Cobalt. Those are interesting links.
 
All these reasons seem valid enough. Given some forum anecdotes and personal experience, I still think there's some unaccounted voodoo involved. I've seen 420J2 (of all things) rust, while a 12C27mod blade (chemically etched beforehand!) remain unaffected when both left to the elements side by side, for several weeks. Also some mysterious lack of consistency from one batch of steel to another.
 
shecky said:
All these reasons seem valid enough. Given some forum anecdotes and personal experience, I still think there's some unaccounted voodoo involved. I've seen 420J2 (of all things) rust, while a 12C27mod blade (chemically etched beforehand!) remain unaffected when both left to the elements side by side, for several weeks. Also some mysterious lack of consistency from one batch of steel to another.
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That's pretty interesting, Shecky. After using some 12C27mod blades for a while and really liking the steel, I was surprised to learn that Sandvik developed this alloy for dishwasher safe cutlery in commercial kitchen usage. I've never really put it to the test, but it sounds like it lives up to the claims.

IMO there are a lot of factors that can promote rusting: steel could be contaminated either from the factory or during fabrication, finish could be such as to hold moisture and dirt, or the environment could be unusually moist or salty. I've even suspected that knives carried in the pocket could be affected by the detergent the pants are washed in, and how well they got rinsed during washing.
 
look up things like " passivation". I have no idea how many blades are passivated.
 
Just wanted to give some follow up, after it got a rub down with 1000 grit paper and oil, I have carried this Junk Yard Dog II everyday since, under pretty much the same conditions as before, and the blade has not developed any rust spots again.
 
The Last Confederate said:
Just wanted to give some follow up, after it got a rub down with 1000 grit paper and oil, I have carried this Junk Yard Dog II everyday since, under pretty much the same conditions as before, and the blade has not developed any rust spots again.
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That's good to hear, hopefully it was just some type of contamination like mete said.
 
It's common enough and it's easier to polish the blade than to go into endless discussions about carbon/chromium ratios [CS is no longer on the forum ]
 
mete said:
It's common enough and it's easier to polish the blade than to go into endless discussions about carbon/chromium ratios [CS is no longer on the forum ]
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You never know!?!?!?

Although I greatly doubt my friend's ability to just sneak back onboard incognito and simply lurk.
 
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