Why does 1095 need a 10 min soak time, also...

[Londinium Armoury]

I'll just get right into the questions, because there's going to be a few of them, and thank you in advance for helping. So I've just set up a little heat treating station and Japanese style Yaki-Ire claying stand to start my new batch of knives with hamons.
I've chosen 1095 as my steel of choice (For now, getting some shirogami, and W2 in soon) I've worked with 1095 in the past, and have had nice results with it. I always use AISI 1095 in its annealed state, then I normalize heat to dull red and water quench, then temper at around 200c for an hour x2.
This time however I'm not going to be tempering in an oven, as I'm going to be using Yaki Modoshi traditional tempering methods, which is basically like a short temper and almost like a second quench at a much lower temp, very different to oven soaking tempering.
This will be leaving my blades very hard on the edge and more suited for hardness rather than toughness.
So anyway, I never actually knew 1095 needed a 10 min soak time when I used to use it in the past, I just heated it up to dull red let it sit there for maybe 1 min until evenly heated, then dunk, nice and slowly right into the water, no soak time or anything near 10 mins. The blades always turned out super hard and never broke on me, I've had no reports of them being chippy on the edge, or broken with terrible looking fractures from people I've given the blades to.
Now I'm doing some final reading before I start my new batch in my new set up, and I hear 10 min soak time, 1095 is difficult, needs a long soak time or it wont harden. Then I start to worry what if the Yaki Modoshi method combined with the lack of 10 mins soaking makes some very weak blades? Because I have all the stuff ready to go, and I don't really want to change the Yaki Modoshi method, or waste the 1095.
So my question that I can't find an answer to is, why does 1095 require a 10 min soak time? is this information legit that I'm reading, what is in the composition of 1095 that demands it be soaked for 10 mins? I ran over all the composition charts and got out my list of steel compositions and compared them with other steels that don't require a 10 min soak.
I can't work it out by myself because I'm not a metalurgist or as experienced as others here, so help me out please, what is in 1095 that makes this a prerequisite? I just can't see anything in it that would make this true, it just looks like a regular basic carbon steel, shallow hardening with a dash of manganese and trace elements.
Am I missing something?

 

[Londinium Armoury]

Just in case people were wondering about my "Why" i'll give a comparison to help share my confusion.
If I compare 1095 to Shirogami 1, they are basically identical in chemical composition. Yet Shirogami 1 is suited for Yaki-ire and Yaki Modoshi with 0 soak time before quench yet I'm told 1095 is not suitable. This doesn't make sense to me.

Shirogami 1 and 1095 are basically the same steel as far as I can tell chemically, shiro has slightly more carbon by .2% which is basically nothing, as 1095 usually has more than .95 and can typically have over 1%.
So if I can heat treat shirogami without a 10 min soak, using traditional Yaki Ire and Yaki Modoshi without issue, what's the technical issue with 1095?

 

[Joshua Fisher]

Maybe Larrin could jump in on this, if I’m remembering correct from past discussions I think it has to do with getting enough carbon into solution, also a lot of people are quenching 1095 in oil so in my mind it seems more critical to make sure all of the available carbon is in solution when using a slower quenching method, I wonder if using the faster quench that 1095 really needs because of the shallow hardening helps reduce the need for soaking the steel at temp. I’ve also used 1095 with good results without a long soak quenching in parks 50 with is similar in speed to water. I’m not a metallurgist so hopefully Larrin or someone else could elaborate more on this, I’m just thinking out loud more or less.

 

[Londinium Armoury]

Maybe Larrin could jump in on this, if I’m remembering correct from past discussions I think it has to do with getting enough carbon into solution, also a lot of people are quenching 1095 in oil so in my mind it seems more critical to make sure all of the available carbon is in solution when using a slower quenching method, I wonder if using the faster quench that 1095 really needs because of the shallow hardening helps reduce the need for soaking the steel at temp. I’ve also used 1095 with good results without a long soak quenching in parks 50 with is similar in speed to water. I’m not a metallurgist so hopefully Larrin or someone else could elaborate more on this, I’m just thinking out loud more or less.

Thanks for the reply, I did read this in a few places, I think right here in a few bladeforums threads people mentioned it in posts dating years back. I still never really understood why 1095 had a carbon distribution issue when going into solution and other steels with similar carbon content didn't. From what I understood I couldn't see the difference between 1095 and a number of other steels, like the shirogami 1 example I gave, because to me it actually seems like 1095 is the more simple steel of the 2, I think Shiro has more silicon than 1095, so it's a tiny bit more complex if you can call it complex at all. There's a bunch of steels even all of the 10xx series that 1095 is in that don't require a soak, I don't think 1084 or 1075 or 1055 require soaking. 75 and 84 do have more manganese though and could technically be classed as borderline deep hardening steels? So those aren't a good comparison, that's why I used shiro 1 as the comparison, because it's basically 1095 with a pinch more carbon. So if shiro 1 has no trouble distributing 1.2% carbon why would 1095 have a problem distributing 1%
Or I could say if Hitachi took .2% carbon out of Shirogami 1, would that mean it no longer can be quenched without a soak and now requires 1? Or does that tiny bit of silicon actually make the carbon behave itself uniformly? I can't find anything about silicon helping distribute carbon if anything it would not have any effect at all at such low amounts, except maybe make it potentially a fraction tougher? I doubt it's noticibly tougher than 1095 though, especially being higher in carbon content it's probably less tough.
If I never read about the 10 min soak time I don't think I would have even noticed there was a problem or it was even needed.
Thanks I will await more replies from others.

 

[Larrin]

Thanks for the reply, I did read this in a few places, I think right here in a few bladeforums threads people mentioned it in posts dating years back. I still never really understood why 1095 had a carbon distribution issue when going into solution and other steels with similar carbon content didn't. From what I understood I couldn't see the difference between 1095 and a number of other steels, like the shirogami 1 example I gave, because to me it actually seems like 1095 is the more simple steel of the 2, I think Shiro has more silicon than 1095, so it's a tiny bit more complex if you can call it complex at all. There's a bunch of steels even all of the 10xx series that 1095 is in that don't require a soak, I don't think 1084 or 1075 or 1055 require soaking. 75 and 84 do have more manganese though and could technically be classed as borderline deep hardening steels? So those aren't a good comparison, that's why I used shiro 1 as the comparison, because it's basically 1095 with a pinch more carbon. So if shiro 1 has no trouble distributing 1.2% carbon why would 1095 have a problem distributing 1%
Or I could say if Hitachi took .2% carbon out of Shirogami 1, would that mean it no longer can be quenched without a soak and now requires 1? Or does that tiny bit of silicon actually make the carbon behave itself uniformly? I can't find anything about silicon helping distribute carbon if anything it would not have any effect at all at such low amounts, except maybe make it potentially a fraction tougher? I doubt it's noticibly tougher than 1095 though, especially being higher in carbon content it's probably less tough.
If I never read about the 10 min soak time I don't think I would have even noticed there was a problem or it was even needed.
Thanks I will await more replies from others.

Shirogami #1 doesn't have more silicon than 1095, only more carbon.

Soak time is to ensure there is sufficient time for the entire piece to heat through and to dissolve carbides. Because 1095 doesn't have much in the way of alloying elements, and carbon can diffuse relatively rapidly, the required time at austenitizing temperature is relatively short. If the steel was annealed to have very large carbides, diffusion time would be longer and a somewhat longer soak would be necessary. However, 10 minutes is unlikely to hurt the steel, particularly if the austenitizing temperature is appropriate, and I prefer to have a longer soak time with a lower temperature then trying to get consistent hardness and properties from a very short soak time where things are more variable. The steel is changing the most in the initial stages and things start to "level out" and change more slowly. I prefer to be in the leveling out stage.

For those that are recommending a long soak time as being required for 1095 could be doing so for a few different reasons: 1) their furnaces are reading too high so at the lower temperature they are using more time is necessary. 2) the longer time is growing the grain somewhat for higher hardenability because the quench isn't fast enough (1095 with its very low hardenability can have issues hardening even with fast oil). 3) they are having inconsistent heat treating and have a list of things that are "required" for a good heat treatment, some of which make a difference and some of which don't, and a 10 minute soak made it on the list somehow. 4) Someone else told them 10 minutes and so they told other people.

My book recommends 10 minutes at 1425-1475°F, but that couldn't have affected bladeforums threads from years past as the book is new. The 10 minutes isn't gospel, and if I was recommending heat treatments in a forge I may not recommend 10 minutes. But 10 minutes is sufficient for consistent heat treatment when using a furnace.

 

[Londinium Armoury]

Shirogami #1 doesn't have more silicon than 1095, only more carbon.

Soak time is to ensure there is sufficient time for the entire piece to heat through and to dissolve carbides. Because 1095 doesn't have much in the way of alloying elements, and carbon can diffuse relatively rapidly, the required time at austenitizing temperature is relatively short. If the steel was annealed to have very large carbides, diffusion time would be longer and a somewhat longer soak would be necessary. However, 10 minutes is unlikely to hurt the steel, particularly if the austenitizing temperature is appropriate, and I prefer to have a longer soak time with a lower temperature then trying to get consistent hardness and properties from a very short soak time where things are more variable. The steel is changing the most in the initial stages and things start to "level out" and change more slowly. I prefer to be in the leveling out stage.

For those that are recommending a long soak time as being required for 1095 could be doing so for a few different reasons: 1) their furnaces are reading too high so at the lower temperature they are using more time is necessary. 2) the longer time is growing the grain somewhat for higher hardenability because the quench isn't fast enough (1095 with its very low hardenability can have issues hardening even with fast oil). 3) they are having inconsistent heat treating and have a list of things that are "required" for a good heat treatment, some of which make a difference and some of which don't, and a 10 minute soak made it on the list somehow. 4) Someone else told them 10 minutes and so they told other people.

My book recommends 10 minutes at 1425-1475°F, but that couldn't have affected bladeforums threads from years past as the book is new. The 10 minutes isn't gospel, and if I was recommending heat treatments in a forge I may not recommend 10 minutes. But 10 minutes is sufficient for consistent heat treatment when using a furnace.

Thank you, that makes sense, so would you say if I cycled annealed AISI 1095 and reduced the grain size before quenching (on a stock removal blade that has not been heated up during shaping and kept cool and away from the hammers, it would be fine to quench with just a regular 1 min soak that I usually do? (I don't have a digital heat treating oven, just various anthracite/charcoal forges and a home made mapp gas mini HT forge)

As you said annealed steal has medium/large grain when it comes in, so I normally cycle it to reduce that anyway, so it should be fine right? also do you know why people don't recommend shirogami 1 to be soaked? because I don't see Japanese smiths soaking their shiro 1 or basic carbons. The way you put it if i'm not mistaking what you said in the wrong way sounds like, as long as it's grain size has been made smaller and cycled properly, and a water or brine quench is used, then the soak isn't actually needed?

Cheers for the reply.

 

[Londinium Armoury]

Shirogami #1 doesn't have more silicon than 1095, only more carbon.

Soak time is to ensure there is sufficient time for the entire piece to heat through and to dissolve carbides. Because 1095 doesn't have much in the way of alloying elements, and carbon can diffuse relatively rapidly, the required time at austenitizing temperature is relatively short. If the steel was annealed to have very large carbides, diffusion time would be longer and a somewhat longer soak would be necessary. However, 10 minutes is unlikely to hurt the steel, particularly if the austenitizing temperature is appropriate, and I prefer to have a longer soak time with a lower temperature then trying to get consistent hardness and properties from a very short soak time where things are more variable. The steel is changing the most in the initial stages and things start to "level out" and change more slowly. I prefer to be in the leveling out stage.

For those that are recommending a long soak time as being required for 1095 could be doing so for a few different reasons: 1) their furnaces are reading too high so at the lower temperature they are using more time is necessary. 2) the longer time is growing the grain somewhat for higher hardenability because the quench isn't fast enough (1095 with its very low hardenability can have issues hardening even with fast oil). 3) they are having inconsistent heat treating and have a list of things that are "required" for a good heat treatment, some of which make a difference and some of which don't, and a 10 minute soak made it on the list somehow. 4) Someone else told them 10 minutes and so they told other people.

My book recommends 10 minutes at 1425-1475°F, but that couldn't have affected bladeforums threads from years past as the book is new. The 10 minutes isn't gospel, and if I was recommending heat treatments in a forge I may not recommend 10 minutes. But 10 minutes is sufficient for consistent heat treatment when using a furnace.

Oh and from my list here, it's saying Shirogami 1 does have more silicon than AISI 1095. Just checked on a few data sheets to confirm my list was correct, you made me think I typed them down wrong. But they confirm my list, says Shirogami has .10 - .20 Si. and that 1095 has none added.

https://www.hitachi-metals.co.jp/e/yss/search/shirogami1.html

https://www.steel0.com/AISI_1095.htm

https://www.azom.com/article.aspx?ArticleID=6561

 

[Larrin]

Thank you, that makes sense, so would you say if I cycled annealed AISI 1095 and reduced the grain size before quenching (on a stock removal blade that has not been heated up during shaping and kept cool and away from the hammers, it would be fine to quench with just a regular 1 min soak that I usually do? (I don't have a digital heat treating oven, just various anthracite/charcoal forges and a home made mapp gas mini HT forge)

As you said annealed steal has medium/large grain when it comes in, so I normally cycle it to reduce that anyway, so it should be fine right? also do you know why people don't recommend shirogami 1 to be soaked? because I don't see Japanese smiths soaking their shiro 1 or basic carbons. The way you put it if i'm not mistaking what you said in the wrong way sounds like, as long as it's grain size has been made smaller and cycled properly, and a water or brine quench is used, then the soak isn't actually needed?

Cheers for the reply.

You are confusing grain size and carbide size. Carbides are hard particles formed by carbon and another element, in this case iron. Grains are part of the steel's structure and are not particles. Fine carbide size means austenitization is faster. If the grain size is very small it can mean lower "hardenability" meaning a faster quench is necessary for full hardness.

If a soak time is not recommended for Shirogami #1 my guess would be that's because it is intended for traditional bladesmiths who are using a forge to heat treat.

 

[Larrin]

Oh and from my list here, it's saying Shirogami 1 does have more silicon than AISI 1095. Just checked on a few data sheets to confirm my list was correct, you made me think I typed them down wrong. But they confirm my list, says Shirogami has .10 - .20 Si. and that 1095 has none added.

https://www.hitachi-metals.co.jp/e/yss/search/shirogami1.html

https://www.steel0.com/AISI_1095.htm

https://www.azom.com/article.aspx?ArticleID=6561

Silicon is present in all 1095, it isn't required by all specifications but it's always added. For example Buderus 1095 targets 0.1-0.3% Si: https://newjerseysteelbaron.com/wp-content/uploads/2020/11/1095.094.Tag418.pdf

 

[Londinium Armoury]

You are confusing grain size and carbide size. Carbides are hard particles formed by carbon and another element, in this case iron. Grains are part of the steel's structure and are not particles. Fine carbide size means austenitization is faster. If the grain size is very small it can mean lower "hardenability" meaning a faster quench is necessary for full hardness.

If a soak time is not recommended for Shirogami #1 my guess would be that's because it is intended for traditional bladesmiths who are using a forge to heat treat.

Thanks for clearing that up, I will remember that difference if I get around to buying a digital HT oven.

 

[Londinium Armoury]

Silicon is present in all 1095, it isn't required by all specifications but it's always added. For example Buderus 1095 targets 0.1-0.3% Si: https://newjerseysteelbaron.com/wp-content/uploads/2020/11/1095.094.Tag418.pdf

Cheers I' will update my list.

 

[Stacy E. Apelt - Bladesmith]

In my opinion, the biggest difference in 1095 and Shiro #1 is the manganese. A little drop in manganese makes a big difference in hardenability.
Also, some 1095 has small amounts of vanadium and other things. All this affects hardenability and the choice of quenchant.

 

[Londinium Armoury]

In my opinion, the biggest difference in 1095 and Shiro #1 is the manganese. A little drop in manganese makes a big difference in hardenability.
Also, some 1095 has small amounts of vanadium and other things. All this affects hardenability and the choice of quenchant.

Do you happen to know why some of the 10xx series has more manganese than others? it's quite a big difference I noticed between them, to a point where it actually stops me selecting them. If 1075 had less manganese I would probably try some hamon with it, but for some reason it has a huge amount compared to 1095.

 

[Stacy E. Apelt - Bladesmith]

10XX steels were not made to make knives. Manganese helps with hardenability and things like vanadium help with grain reduction. That is great for springs and tools, but not so good for yake-ire. Even blade steels from the knife suppliers usually have a significant amount of manganese to assure deep hardening. The only place shallow hardening is an advantage in knifemaking is in attaining a hamon.

 

[me2]

10xx steels with carbon more than 0.8 C may have a little more Mn than others. The increase in carbon can reduce hardenability a little.

 

[Londinium Armoury]

10XX steels were not made to make knives. Manganese helps with hardenability and things like vanadium help with grain reduction. That is great for springs and tools, but not so good for yake-ire. Even blade steels from the knife suppliers usually have a significant amount of manganese to assure deep hardening. The only place shallow hardening is an advantage in knifemaking is in attaining a hamon.

How selfish of the steel industry, to put engineering parts and other tools above the needs of people who practice out dated 1000 year old knife making methods. They have their priorities all wrong.

 

[Londinium Armoury]

10xx steels with carbon more than 0.8 C may have a little more Mn than others. The increase in carbon can reduce hardenability a little.

I'd prefer to not have to use 10xx steels but being in London I'm kind of stuck with them to practice on. I can only get W2 in 1 very specific size, max 3mm thick and 4cm wide, Then the Shirogami here is very over priced just under £50 per bar, I don't feel comfortable spending £50 per small bar for a basic carbon steel billet, seems extortionate.

 

[Stacy E. Apelt - Bladesmith]

I just looked at Workshop Heaven's site. The W2 is in a pretty good size for forging (30X6mm) and is less than 10£ a bar..
I didn't realize that the Hitachi steels had gone up so much. Check out Dictum in Germany.

 

[Londinium Armoury]

I just looked at Workshop Heaven's site. The W2 is in a pretty good size for forging (30X6mm) and is less than 10£ a bar..
I didn't realize that the Hitachi steels had gone up so much. Check out Dictum in Germany.

That's exactly the place where I was planning to source my W2 and Hitachi steels, I was put off by the £50 per bar price tag though, especially because I'm water quenching, each ping costing 50 no thanks haha. Cheers though that's the only place I can get those steels from UK soil without import.

 

[Stacy E. Apelt - Bladesmith]

Check steel suppliers for 26C3. It is between Hitachi White and Hitachi Blue. Some like to call it "Spicy White". It is very low price. Many of the USA knife and steel suppliers will ship it to the UK.