What difference does .......
- Thread starter Roger
- Start date
Karl B. Andersen
Well-Known Member
Many times the alloy content - most frequently the Carbon content - has a rather large window of % fluctuation in a given steel type.
For example, "The Heat Treater's Guide" gives the C content a range of 0.60 to 1.4.
That's a huge difference.
That's why it's often important to get some type of certification from your steel supplier where your steel's alloy lies.
This will determine which end of the heat spectrum you need to use.
For example, "The Heat Treater's Guide" gives the C content a range of 0.60 to 1.4.
That's a huge difference.
That's why it's often important to get some type of certification from your steel supplier where your steel's alloy lies.
This will determine which end of the heat spectrum you need to use.
Knifemaker.ca
Dealer - Purveyor
Roger, your question is a it broad and covers half of the entire science of heat treat. (The other is time)
I suspect there is something specific you are looking for. If you can tell us what steel you are looking at on that chart - and what performance characteristics you'd value, we might be able to help you with some suggestions for that starting point you want.
I suspect there is something specific you are looking for. If you can tell us what steel you are looking at on that chart - and what performance characteristics you'd value, we might be able to help you with some suggestions for that starting point you want.
Kevin R. Cashen
Super Moderator
When the steel is alloyed with a good amount of carbide formers the high and low temps are given for austenitizing based upon the properties most desired. Low temps will give lower Rockwell for greater toughness by leaving more carbon locked in the carbide for abrasion resistance. The higher temperatures will result in greater strength by putting more carbon into solution and raising the Rockwell. But if it is a simple steel, like say W-2, there will be a range due to the fact that W-2 can have anywhere from .75% to well over 1% carbon, the higher temps are for the lower carbon flavor, while the lower temps will be for the high carbon stuff.
Should have explained better. I'm starting with the basic 10XX series mostly 1095 and some stuff I suppose is old coil spring 5160. The unknown is trial and error but the different manufactures of 1095 have various carbon contents so It's nice to know if what I'm using I can vary the temperature depending on that content and get an end result that takes the most advantage of the steel I'm using and what the intended purpose of it is. Then I guess a good thing to remember is if the carbon is less use a bit more heat and less if the carbon is at the top of the scale.
Kevin R. Cashen
Super Moderator
I have spawned some questions with my words about abrasion resistance vs. toughness/strength; questions are always good, but confusion is something I don’t want to bring so I hope to help avoid that with the following.
There are three main properties involved here- toughness, strength, and abrasion resistance. Toughness and strength most often are on opposition when the avenue of toughness is increased ductility, i.e. dropping a blade from 60HRC to 54HRC in order to gain “toughness” but at a significant and unavoidable, loss of strength. Strength being the ability to resist deformation, and ductility being the ability to easily deform are indeed the opposite ends of the “hardness” spectrum. Hardness is not so much a property unto itself as it is a way of measuring and expressing strength.
Now for the third- abrasion resistance, and increase in hardness will often increase abrasion resistance, but not all hardness is the same, so while higher Rockwell will increase wear resistance, the inverse is not always true, higher wear resistance does necessarily mean higher Rockwell hardness. Since hardness is actually just a way of expressing a particular form of strength there can be different forms based on how they are measured, the two most common are scratch hardness (e.g. the Mohs scale), and penetrative hardness (e.g. Rockwell).
In a simple carbon steel that has .80% carbon or less all you have is the sliding scale of ductility vs. strength, and so if you want greater abrasion resistance you need to sacrifice some toughness and slide things toward higher strength. This is why you have all of these inventive differential construction and heat treating measures on old blades that used ancient steels, basic steels/basic properties. Intentional alloying was developed as an answer to this, to be able to have our cake and eat it too, when it came to optimizing steel properties, this is yet another reason why I say – alloying changed everything.
However I do have an interesting ancient exception that I often use as the best simple illustration of this abrasion resistance vs. toughness/strength concept- wootz. I have a wootz cake that Ric Furrer and I made maybe ten or fifteen years ago, that I use as a door stop in my lab (like to joke that I finally found a good use for wootz:3
. I have demonstrated this concept to shop visitors by taking a letter stamp and with hand pressure alone marking that steel, and then handing them a file and have them go at it and see what 1.4% carbon steel does to a file. I have worn 14” chopsaw wheels down to the hub trying to cut that rather ductile steel! With the carbide action what you have is the equivalent of playdoh with diamonds mixed into it.
Wootz is mostly just simple iron-carbide, a fairly tame carbide in comparison- but alloying changed everything. With modern additions like vanadium, tungsten, niobium or titanium, the carbide power increases exponentially. In hardening steel by simply trapping carbon in solution, you can hope to get a maximum of around 66-68HRC, pretty good for abrasion resistance, but mere child’s play compared to the 80HRC+ of some of those carbides. So with steels that have heavy carbide formers, and the carbon to feed them, you can have a tougher steel (lower HRC) that has its carbide formers with a belly full of carbon for abrasion resistance, or you can have maximum hardness and abrasion resistance by feeding both the hardened steel matrix (fortifying the martensite), as well as still have some carbides left over, but with the knowledge that you have sacrificed toughness for that gain. The difference is made by how much heat you throw at dissolving those carbides.
One just needs to remember that it takes serious control to do it all correctly, because the more carbide action that is possible, the more things that can go wrong, this is why 1080 is an excellent beginners steel while 1095 is not and the only difference is a mere .15% carbon. The best place for any carbon in excess of .8% is in fine versions of those carbides scattered evenly throughout the steel, but the more carbide there is, the more it wants to gather together in brittle sheets and large blocks that makes for more brittle steel and poor edges regardless of the Rockwell.
There are three main properties involved here- toughness, strength, and abrasion resistance. Toughness and strength most often are on opposition when the avenue of toughness is increased ductility, i.e. dropping a blade from 60HRC to 54HRC in order to gain “toughness” but at a significant and unavoidable, loss of strength. Strength being the ability to resist deformation, and ductility being the ability to easily deform are indeed the opposite ends of the “hardness” spectrum. Hardness is not so much a property unto itself as it is a way of measuring and expressing strength.
Now for the third- abrasion resistance, and increase in hardness will often increase abrasion resistance, but not all hardness is the same, so while higher Rockwell will increase wear resistance, the inverse is not always true, higher wear resistance does necessarily mean higher Rockwell hardness. Since hardness is actually just a way of expressing a particular form of strength there can be different forms based on how they are measured, the two most common are scratch hardness (e.g. the Mohs scale), and penetrative hardness (e.g. Rockwell).
In a simple carbon steel that has .80% carbon or less all you have is the sliding scale of ductility vs. strength, and so if you want greater abrasion resistance you need to sacrifice some toughness and slide things toward higher strength. This is why you have all of these inventive differential construction and heat treating measures on old blades that used ancient steels, basic steels/basic properties. Intentional alloying was developed as an answer to this, to be able to have our cake and eat it too, when it came to optimizing steel properties, this is yet another reason why I say – alloying changed everything.
However I do have an interesting ancient exception that I often use as the best simple illustration of this abrasion resistance vs. toughness/strength concept- wootz. I have a wootz cake that Ric Furrer and I made maybe ten or fifteen years ago, that I use as a door stop in my lab (like to joke that I finally found a good use for wootz:3
. I have demonstrated this concept to shop visitors by taking a letter stamp and with hand pressure alone marking that steel, and then handing them a file and have them go at it and see what 1.4% carbon steel does to a file. I have worn 14” chopsaw wheels down to the hub trying to cut that rather ductile steel! With the carbide action what you have is the equivalent of playdoh with diamonds mixed into it.Wootz is mostly just simple iron-carbide, a fairly tame carbide in comparison- but alloying changed everything. With modern additions like vanadium, tungsten, niobium or titanium, the carbide power increases exponentially. In hardening steel by simply trapping carbon in solution, you can hope to get a maximum of around 66-68HRC, pretty good for abrasion resistance, but mere child’s play compared to the 80HRC+ of some of those carbides. So with steels that have heavy carbide formers, and the carbon to feed them, you can have a tougher steel (lower HRC) that has its carbide formers with a belly full of carbon for abrasion resistance, or you can have maximum hardness and abrasion resistance by feeding both the hardened steel matrix (fortifying the martensite), as well as still have some carbides left over, but with the knowledge that you have sacrificed toughness for that gain. The difference is made by how much heat you throw at dissolving those carbides.
One just needs to remember that it takes serious control to do it all correctly, because the more carbide action that is possible, the more things that can go wrong, this is why 1080 is an excellent beginners steel while 1095 is not and the only difference is a mere .15% carbon. The best place for any carbon in excess of .8% is in fine versions of those carbides scattered evenly throughout the steel, but the more carbide there is, the more it wants to gather together in brittle sheets and large blocks that makes for more brittle steel and poor edges regardless of the Rockwell.
Mark Behnke
Well-Known Member
Kevin
^ Maybe understanding some basic heat treating isn't out of my reach, with that post my understanding of a lot of the principals you write about and the differences in steels is becoming more clear.
Thank you for continuing to share your knowledge and work.
Mark
^ Maybe understanding some basic heat treating isn't out of my reach, with that post my understanding of a lot of the principals you write about and the differences in steels is becoming more clear.
Thank you for continuing to share your knowledge and work.
Mark
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