O1 vs 80CrV2

[Juha Perttula]

The biggest difference between O1 and 80CrV2 is, I think, Mn content. O1 has more Mn and therefore it has better hardenability (slower oil can be used). Mn result in more retained austenite and for that reason as-quenched hardness of O1 is 1 or 2 Rc number lower. But tempered to about 60 Rc they have equal toughness. O1 may be slightly air hardening during normalizing, but the normalizing is not important, because double hardening gives smallest grain size and best toughness. Generally tempered martensite is tougher than bainite with the same hardness.

 

[hugofeynman]

The biggest difference between O1 and 80CrV2 is, I think, Mn content. O1 has more Mn and therefore it has better hardenability (slower oil can be used). Mn result in more retained austenite and for that reason as-quenched hardness of O1 is 1 or 2 Rc number lower. But tempered to about 60 Rc they have equal toughness. O1 may be slightly air hardening during normalizing, but the normalizing is not important, because double hardening gives smallest grain size and best toughness. Generally tempered martensite is tougher than bainite with the same hardness.

I thought it was the other way around, bainite being tougher than tempered Martensite, for the same hardness. At least, I retained that information from Metallurgists that I talk with.

 

[Larrin]

The biggest difference between O1 and 80CrV2 is, I think, Mn content. O1 has more Mn and therefore it has better hardenability (slower oil can be used). Mn result in more retained austenite and for that reason as-quenched hardness of O1 is 1 or 2 Rc number lower. But tempered to about 60 Rc they have equal toughness. O1 may be slightly air hardening during normalizing, but the normalizing is not important, because double hardening gives smallest grain size and best toughness. Generally tempered martensite is tougher than bainite with the same hardness.

The article already described the difference in Mn and hardenability. You will have to provide references for tempered martensite being tougher than bainite.

 

[Juha Perttula]

Tempered martensite vs. bainite

Thank you for the comments. Generally tempered martensite is tougher than bainite with similar hardness because bainite transformation in blade smith forge is usually poorly controlled. But the blade smith's bainite can attain good toughness because it is quite soft. So, martensitic edge and bainitic spine can be a good combination. Ball bearing manufacturers may use bainitic 52100; therefore, this topic is studied. Here is one article http://mtmcongress.com/proceedngs/2012/3/09.EFFECT OF AUSTEMPERING TEMPERATURES ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF A BEARING STEEL.pdf They used unnotched 10x10x55 mm Charpy specimens and got 50 J (50 J/cm2) at hardness level of 55 Rc. In my own corresponding measurements (7.5x11x55 mm unnotched Charpy) with hardened and tempered bearing steel I got values around 100 J/cm2 at hardness level of 62 Rc . So, my tempered martensite was harder and tougher than their bainite.

I have also compared in my lab dia 2x15x55 mm AISI 1075 bainitic and tempered martensite samples at hardness level of 52 Rc. In this case bainite was tougher having about 100 J/cm2 while tempered martensite had only 70 J/cm2. In quality control, I have seen several times that incomplete hardening ( i.e. some bainite) have spoiled the toughness of industrial component. However, we should note that well controlled indusrtial bainite can be tough, and in some cases even tougher than tempered martensite. But anyway, in my opinion, bainite is not easy magic trick to attain superior toughness.

 

[Larrin]

Tempered martensite vs. bainite

Thank you for the comments. Generally tempered martensite is tougher than bainite with similar hardness because bainite transformation in blade smith forge is usually poorly controlled.

I'm not sure what you mean. Who is forming bainite in a forge? The bladesmiths are properly heat treating using a forge to form martensite but not bainite?

But the blade smith's bainite can attain good toughness because it is quite soft. So, martensitic edge and bainitic spine can be a good combination. Ball bearing manufacturers may use bainitic 52100; therefore, this topic is studied. Here is one article http://mtmcongress.com/proceedngs/2012/3/09.EFFECT OF AUSTEMPERING TEMPERATURES ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF A BEARING STEEL.pdf They used unnotched 10x10x55 mm Charpy specimens and got 50 J (50 J/cm2) at hardness level of 55 Rc. In my own corresponding measurements (7.5x11x55 mm unnotched Charpy) with hardened and tempered bearing steel I got values around 100 J/cm2 at hardness level of 62 Rc . So, my tempered martensite was harder and tougher than their bainite.

Usually it is best to compare values within a single study, since so many parameters are different. For example, in the study you cited that austenitized at 950C for 30 minutes, which likely led to significant grain growth. Also, the ASTM standard for charpy testing says not to compare toughness tests between different sample dimensions because of the different size of the constrained region.

I have also compared in my lab dia 2x15x55 mm AISI 1075 bainitic and tempered martensite samples at hardness level of 52 Rc. In this case bainite was tougher having about 100 J/cm2 while tempered martensite had only 70 J/cm2. In quality control, I have seen several times that incomplete hardening ( i.e. some bainite) have spoiled the toughness of industrial component. However, we should note that well controlled indusrtial bainite can be tough, and in some cases even tougher than tempered martensite.

I appreciate that you were willing to also share the result that contradicts your opinion.

But anyway, in my opinion, bainite is not easy magic trick to attain superior toughness.

On that we can agree.

 

[scott.livesey]

a big difference between O1 and 80CrV2 is price and availability. You can find 80CrV2 at two or three knife supply sites in limited sizes. You can get O1 from 100's of places, in thickness from 1/64" to 1 1/2", widths to 12", precision ground flat stock if you want, most of the sources are ISO9000 compliant, NOS(new old stock) is typically 10% to 30% cheaper than same size in 80CrV2. 80CrV2 would be my choice if I was making a rugged use blade at Rc60. O1 would be my choice if I was making thin geometry blade at Rc 62-65.

 

[hugofeynman]

Finally watched Forged in Fire: knife or death! I think Michael Allensons sword has not a bainitic structure, because he told that his knife was austenized in one salt pot up to critical, then parks 50, and finally was tempered during an hour at 450F in another salt pot. So a good Martensite is also really tough. The right steel, ultra precise temperatures and times that’s the secret to a durable blade.

 

[Willie71]

Finally watched Forged in Fire: knife or death! I think Michael Allensons sword has not a bainitic structure, because he told that his knife was austenized in one salt pot up to critical, then parks 50, and finally was tempered during an hour at 450F in another salt pot. So a good Martensite is also really tough. The right steel, ultra precise temperatures and times that’s the secret to a durable blade.

I’m no expert, as I’ve never done it, but that sounds like marquenching. Larrin? Please clarify.

 

[Larrin]

I’m no expert, as I’ve never done it, but that sounds like marquenching. Larrin? Please clarify.

If it was quenched in oil near room temperature than it would not be marquenching. But I haven’t seen the show and we now have two conflicting accounts of what was reported in the episode.

 

[hugofeynman]

I’m no expert, as I’ve never done it, but that sounds like marquenching. Larrin? Please clarify.

Willie71, I think marquenching is what Fredrik Haakonsen is doing here, with his Vanadis 4 extra blades http://kniver.blogspot.pt/2007/08/herding-med-fredrik-jeg-har-ikke-lest.html?m=1 (sorry, is in Norwegian, use google translator), quenching them in molten salt at 500C (932F) or what my man Adam Kornalski makes, he heats until critical, and then quenches in 160C-180C (320F- 356F) hot oil. I don’t know exactly why they do this, but I think this way they don’t have warping problems and less internal stresses in the blade.

 

[Larrin]

In the show he says “salt pot up to critical into Parks 50, and then it was tempered in a secondary salt pot at 450 for an hour.” The microstructure was tempered martensite.

 

[Big Chris]

In the show he says “salt pot up to critical into Parks 50, and then it was tempered in a secondary salt pot at 450 for an hour.” The microstructure was tempered martensite.

Sorry, I watched the episode again last night and noticed that I mis-heard what he said.

 

[Willie71]

If it was quenched in oil near room temperature than it would not be marquenching. But I haven’t seen the show and we now have two conflicting accounts of what was reported in the episode.

I misread the post, and I thought he was quenching in 450f salt.

 

[Larrin]

I can see why it would be confusing because often if using two salt pots for heat treating that is for the purpose of austempering or marquenching. In his case he was using it for a more conventional quench and temper.

 

[hugofeynman]

Like Kevin Cashen and Fredrik Haakonsen do, although Haakonsen marquenches his blades, he doesn’t do the conventional near to room temperature quench.

 

[Steve@Allenson Armory]

The winner of Knife or Death last night on History had a sword, the first that did not bend nor suffer major edge degredation.
He was asked about his heat treat method; austenize in a salt pot and then quenched in a salt pot at 400 degrees for an hour.
If I understood your article correctly, this was a Bainite sword?
Please correct me if I'm wrong.

Thanks

Michael is my cousin and partner at Allenson Armory. The sword in question was made from 1075, Normalized in hi temp salt pot at aus temperature, heated to aus in salt pot, quenched in 110f (ish) Parks 50, clamped in a frame to prevent sabering and warping while it was allowed to cool to room temp, then tempered at 450 for an hour in low temp salt, any warps or wiggles corrected, then back to the 450 degree salt for 2 hours. the only damage the blade took during the competition was 2 little chips from hacking through the ice block, which were removed in less than 5 min with a few passes on a hand stone and a slack belt. The thing has a CRAZY amount of flex when he's showing off how far it will bend and not take a set, and to me, for a bastard sword, is balanced quite well for 1 handed use, but the "giggle factor" goes through the roof when you grip it as a hand and a half.

 

[hugofeynman]

Michael is my cousin and partner at Allenson Armory. The sword in question was made from 1075, Normalized in hi temp salt pot at aus temperature, heated to aus in salt pot, quenched in 110f (ish) Parks 50, clamped in a frame to prevent sabering and warping while it was allowed to cool to room temp, then tempered at 450 for an hour in low temp salt, any warps or wiggles corrected, then back to the 450 degree salt for 2 hours. the only damage the blade took during the competition was 2 little chips from hacking through the ice block, which were removed in less than 5 min with a few passes on a hand stone and a slack belt. The thing has a CRAZY amount of flex when he's showing off how far it will bend and not take a set, and to me, for a bastard sword, is balanced quite well for 1 handed use, but the "giggle factor" goes through the roof when you grip it as a hand and a half.

That sword is perfect! For me, a sword that can go through the hole knife or death circuit and even allowing the user/maker to win, its the benchmark for what a sword should be.

 

[i4Marc]

Larrin,

I read somewhere about Austenitizing at different temperatures. I'm sorry I don't remember the source and I've tried to find it again but can't. It was related in this case to 80CrV2 however I suspect it relates to most steels. I read that Austenitizing at the low end of the range will leave more carbon locked up in carbides giving better wear resistance and Austenitizing at higher temps will release more carbon resulting in a harder blade and better edge retention. If I read that correctly, can you please explain that a bit further about what happens in the steel Austenitizing at lower temps vs higher temps(or correct me)? I can see higher carbide levels or carbide size giving a toothier edge. Wouldn't higher wear resistance give you better edge retention?

 

[Larrin]

Larrin,

I read somewhere about Austenitizing at different temperatures. I'm sorry I don't remember the source and I've tried to find it again but can't. It was related in this case to 80CrV2 however I suspect it relates to most steels. I read that Austenitizing at the low end of the range will leave more carbon locked up in carbides giving better wear resistance and Austenitizing at higher temps will release more carbon resulting in a harder blade and better edge retention. If I read that correctly, can you please explain that a bit further about what happens in the steel Austenitizing at lower temps vs higher temps(or correct me)? I can see higher carbide levels or carbide size giving a toothier edge. Wouldn't higher wear resistance give you better edge retention?

I think I have this pretty well covered in this aritcle: http://knifesteelnerds.com/2018/03/01/austenitizing-part-2-effects-on-properties/

For a given hardness lower austenitizing temperature usually leads to higher toughness. Edge retention is primarily controlled by hardness for a given steel. Carbides are very important when comparing different steels to each other, however.

 

[DevinT]

Steels in the annealed condition have twice the carbide volume as hardened and tempered, hardness is more important to wear resistance/edge holding than carbide volume. There is a sweet spot for every grade according to the task.

With increasing hardness there is a drop in toughness and an increase in wear resistance. The higher the aus temp the more carbides dissolve and the more carbon and alloy goes into solution.

80crv2 will have relatively low carbide volume. For most simple steels slightly under hardening by using a temperature just below peak hardening temperature, produces a very good balance between wear resistance and toughness.

Hoss