Silicon Additions for Improving Steel Toughness

Interesting, the sharp drop in toughness as the shock steels near 60hrc brought them extremely close to 3v. At lower Rockwell c hardness they are significantly tougher.

Who'd have thunk 3v nearly as tough as a shock steel but with better all around attributes for a knife :rolleyes:

Glad Mr. Hugo took the time to read this.
 
Part of the drop in toughness for the shock resisting steels at high hardness is because of the poor toughness with a 300°F temper, not because of an inherent inability to have high hardness with high toughness. The Latrobe datasheet for S5, for example, shows the use of higher austenitizing temperatures for higher hardness. https://www.cartech.com/globalassets/datasheet-pdfs/cartech_s5.pdf

Certainly getting much higher than 61 or 62 Rc is difficult with similar high toughness.
 
Larrin said:
Part of the drop in toughness for the shock resisting steels at high hardness is because of the poor toughness with a 300°F temper, not because of an inherent inability to have high hardness with high toughness. The Latrobe datasheet for S5, for example, shows the use of higher austenitizing temperatures for higher hardness. https://www.cartech.com/globalassets/datasheet-pdfs/cartech_s5.pdf

Certainly getting much higher than 61 or 62 Rc is difficult with similar high toughness.
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What are the other trade offs for a knife in s5? The point behind infi and 3v to an extent is the well rounded attributes.

Obviously steels surpass them in any single area but the ability to have high marks in all areas is what makes them desirable.

Sheer toughness means nothing if the knife sucks for it's intended use... As a knife.

Plenty of structural steels will survive being beaten with a hammer more than 3v. They make a crappy knife because of achievable (or lack thereof) hardness.

If there are steels that out perform 3v across the board, I'd love to know what they are so I can let all the big names in the performance knife game in on the secret.
 
shinyedges said:
What are the other trade offs for a knife in s5? The point behind infi and 3v to an extent is the well rounded attributes.

Obviously steels surpass them in any single area but the ability to have high marks in all areas is what makes them desirable.

Sheer toughness means nothing if the knife sucks for it's intended use... As a knife.

Plenty of structural steels will survive being beaten with a hammer more than 3v. They make a crappy knife because of achievable (or lack thereof) hardness.

If there are steels that out perform 3v across the board, I'd love to know what they are so I can let all the big names in the performance knife game in on the secret.
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Those may be your criteria for what makes a good knife but that does not mean they are universal criteria for what makes a good knife. There isn't much point to wear resistance in a chopper for example. Resistance to deformation and chipping is not helped by wear resistance, and higher wear resistance makes manufacturing and resharpening more difficult which is significant when we are talking about large blades. If we are talking about folders of kitchen knives then it will be different criteria. Even within those categories there are many different types. Comparison to structural steels is not really a good one because S5 achieves much higher hardness (59+ Rc). Steel selection and edge geometry design must include both the use case and the intended user.
 
Larrin said:
Those may be your criteria for what makes a good knife but that does not mean they are universal criteria for what makes a good knife. There isn't much point to wear resistance in a chopper for example. Resistance to deformation and chipping is not helped by wear resistance, and higher wear resistance makes manufacturing and resharpening more difficult which is significant when we are talking about large blades. If we are talking about folders of kitchen knives then it will be different criteria. Even within those categories there are many different types. Comparison to structural steels is not really a good one because S5 achieves much higher hardness (59+ Rc). Steel selection and edge geometry design must include both the use case and the intended user.
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Interesting, I find my choppers are more effective when sharp so I appreciate a steel that can holds it's edge in my choppers like my 1311. What's "good" is subjective in a knife especially for specific applications, I agree. Although I'd wager there is a fairly universal consensus on what "good" constitutes for most people.

My point in the comparison involving structural steels was the sacrifice of other attributes for the Uber toughness. Which I think it was valid.
 
shinyedges said:
Interesting, I find my choppers are more effective when sharp so I appreciate a steel that can holds it's edge in my choppers like my 1311. What's "good" is subjective in a knife especially for specific applications, I agree. Although I'd wager there is a fairly universal consensus on what "good" constitutes for most people.

My point in the comparison involving structural steels was the sacrifice of other attributes for the Uber toughness. Which I think it was valid.
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Unless you are doing tasks with your choppers that are not chopping, the added wear resistance is not likely make the knife more effective at staying sharp.

It is a common misunderstanding that toughness is the only attribute that improves resistance to edge damage in chopping. Hardness/strength is also important for avoid edge rolling and deformation. So on the point of not using <50 Rc steel for choppers we agree.
 
Larrin said:
Unless you are doing tasks with your choppers that are not chopping, the added wear resistance is not likely make the knife more effective at staying sharp.

It is a common misunderstanding that toughness is the only attribute that improves resistance to edge damage in chopping. Hardness/strength is also important for avoid edge rolling and deformation. So on the point of not using <50 Rc steel for choppers we agree.
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I agree that it's a common misunderstanding, not one that I misunderstand though. When chopping like clearing brush it's not a 90° impact, it's a pull cut as well as chop ;) which strength and edge retention are both advantageous for.
 
Very interesting article.
So high alloy steels (without a lot of Si) will benefit from higher tempering temps because of secondary hardening, but low alloy steels will suffer TME if tempered too hot.
If a higher austenizing temperature is used for higher toughness-hardness balance of low alloy steels, don't you run the risk of excessive grain growth?
 
Lower austenitizing temperature is better for toughness, not higher.
 
danbot said:
Ah, that makes more sense. I had it backwards in my brain! :oops::)
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If only there was a way to make our reading comprehension perfect, instead of the ~60% it is reported to be:
"With low alloy steels, tempering above 400 or perhaps 450°F is generally not recommended. If lower hardness or higher toughness is desired it is better to use a lower austenitizing temperature or a steel with lower carbon. See this article for information on why a lower austenitizing temperature is good for toughness."

(By the way I am notorious for skimming articles online)
 
Larrin said:
If only there was a way to make our reading comprehension perfect, instead of the ~60% it is reported to be:
"With low alloy steels, tempering above 400 or perhaps 450°F is generally not recommended. If lower hardness or higher toughness is desired it is better to use a lower austenitizing temperature or a steel with lower carbon. See this article for information on why a lower austenitizing temperature is good for toughness."

(By the way I am notorious for skimming articles online)
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Haha! Yes, higher..lower...higher...lower..more..less..., it starts to get twisted around sometimes.
 
It's especially difficult when writing articles about how lowering one parameter raises another. Or dropping one thing correlates with increasing another.
 
Larrin said:
Yeah, usually.
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That’s one of the reasons why I prefer my knives treated with fire and oil, no cryo treatment. There’s a lot of controversy between cryo treatment studies, so no cryo for most of my knives. My pm steel knives are almost exclusively made with high tempers, to eliminate almost all RA. This will create a secondary Hardening pump, wish is beneficial to wear resistance, the main reason for pm steels to exist. Does cryo increases toughness in pm steels? Probably, 20%, or so, but why I want to force a pm steel knife to be tough? Isn’t pm steels supposed to be most wear resistant than others, with all that Vanadium? If I want TOUGH (chopper/survival blade) I go with steels with better “genetics” for toughness, like the ones I’ve mentioned over and over again. Does a big chopper need to be wear resistant? No! Those pm steels will loose their sharpness in dirty wood exactly like the ”simple” ingot steels, and will be a pain to sharpen when dull (or when chipped), because those vanadium carbides are there to make things harder. Maybe Ztuff is almost as tough as S7, but let someone chop all day with both steels really hard and dirty wood and, at the end of the day, look at the edges. Maybe both need some sharpening and one will be much easier to fix than the other. So is Ztuff an advantage over S7 giving 5 times more time sharpening? Is my brain thinking ok?
 
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