New here- 15 years old. Question about heat treating 1084 in kiln

[Keanen]

Hi I am new to the forum. I am 15 years old and I am having some problems with heat treating 1084 from New Jersey Steel Baron in my Evenheat kiln with Parks 50.

I am doing stock removal and was normalizing at 1600 & 1450 for ten minutes and soaking at 1475 for ten minutes before quenching. When I did a snap test, the test coupon bent. I went ahead and tried without normalizing, but instead soaked at 1490 for fifteen minutes. I had success with this. The coupon snapped and had really fine grain.

My question is why would normalization cause the coupon to be soft with course grain/tearing? What is happening that normalization is affecting the heat treat?

My quench tank is beside my kiln. I try to get the temperature to 70. I am concerned that I might have overheated the oil when I was heat treating out of a forge, but it looks fine to the eye. I have quenched perhaps 100 blades in it.

 

[DeadboxHero]

Hi I am new to the forum. I am 15 years old and I am having some problems with heat treating 1084 from New Jersey Steel Baron in my Evenheat kiln with Parks 50.

I am doing stock removal and was normalizing at 1600 & 1450 for ten minutes and soaking at 1475 for ten minutes before quenching. When I did a snap test, the test coupon bent. I went ahead and tried without normalizing, but instead soaked at 1490 for fifteen minutes. I had success with this. The coupon snapped and had really fine grain.

My question is why would normalization cause the coupon to be soft with course grain/tearing? What is happening that normalization is affecting the heat treat?

My quench tank is beside my kiln. I try to get the temperature to 70. I am concerned that I might have overheated the oil when I was heat treating out of a forge, but it looks fine to the eye. I have quenched perhaps 100 blades in it.

Fine pearlite and retained austenite.

The normalizing and cycling lead to reduced hardenability and overaustenitizing.

 

[Keanen]

Fine pearlite and retained austenite.

The normalizing and cycling lead to reduced hardenability and overaustenitizing.

Thanks for your reply. Can you explain what you mean by overaustenitizing? I don't understand that term.

Am I wrong, I thought it was commonplace to normalize steel. Thank you.

 

[Alex Topfer]

It is common to normalise steel, but it does reduce hardenability. This is more of an issue for those of us who forge, as the forging increases the grain size and adds stresses which then needs to be fixed.

Your first one should have worked. Have you calibrated the kiln? Maybe your temperatures are reading higher than they actually are, otherwise maybe try water quenching a coupon. Overheating the oil shouldn't have had that much effect.
What are the dimensions of the coupon?

 

[Keanen]

It is common to normalise steel, but it does reduce hardenability. This is more of an issue for those of us who forge, as the forging increases the grain size and adds stresses which then needs to be fixed.

Your first one should have worked. Have you calibrated the kiln? Maybe your temperatures are reading higher than they actually are, otherwise maybe try water quenching a coupon. Overheating the oil shouldn't have had that much effect.
What are the dimensions of the coupon?

Thank you. I haven't calibrated the kiln. How would you go about doing that? It's pretty new.

I did try water quenching with the normalization treatment that I stated and it did harden. The coupons are 3/16" and about 1"x2".

 

[DeadboxHero]

Thanks for your reply. Can you explain what you mean by overaustenitizing? I don't understand that term.

When you are hardening the steel, you are bringing up to a critical temperature where it transforms from ferrite to austenite.

We call this "austenitizing"

When we cool fast (quench) from austenitizing, there is some residual austenite left over that did not transform into the harder phase (martensite)

We call this retained austenite. It is soft (15 HRC)

The temperature used for austenitizing is a major factor for how much or little retained austenite (RA) is left in the structure.

Yes, austenitizing at too high of a temperature will cause excessive carbon in solution and will interfere with the transformation to hard phase.

We call this "over austenitizing"

There are other problems from over austenitizing also such as enlarged grains and plate martensite but I'm skipping that for brevity.

Since you have an Evenheat klin you can combat this by soaking at the proper temperature and even further refine with cold treatment.


But cold treatment can't make up for over austenitizing.

The key take away here is that the prior microstructure before austenitizing has a HUGE effect on the austenitizing temperature needed.

Am I wrong, I thought it was commonplace to normalize steel. Thank you.

You are not wrong, but that is used for resetting the microstructure after forging. However, since you are doing stock removal, it is technically unnecessary.

If you are going to do normalizing and a grain refining cycle, it will be important for you to also spheroidize the carbides to stabilize the amount of carbon your putting in solution with a soak.

With the current steps you did, you're starting place before hardening was fine pearlite which Is ideal for doing a forge heat treatment with little soaking. However, with doing a soak, the pearlite dissolves carbon rapidly which can lead to over austenitizing especially at 1475f with thermal cycling.

Another factor working against you is that 1084 is an extremely shallow hardening steel which requires an extremely fast quenchant. It should be noted that parks 50 is at the very edge of being able to harden 1084 and should be done in thinner cross sections.

The normalizing and cycling that you did will even further reduce the hardenability

Finer grains make it difficult to out pace diffusion, and in this case if you are getting diffusion during quenching you are creating very fine pearlite (40 HRC)

So, all those factors combined will lead to the problems you experienced.


Ways to circumvent this

1. Don't use normalizing and grain refinement with 1084 stock removal. (Also 1490f is too high)

2. Use a steel with better hardenability such as 80Crv2, 52100 etc then you can normalize and grain refine to your hearts content (don't forget to anneal to spheroidize carbides before austenitizing)

3.For 1084, use an anneal to spheroidize after normalizing, adjust the austenitizing temperature to account for overaustenitizing due to finer more easily dissolved carbides and use a even faster quenchant such as brine to get diffusionless transformation which will be hindered by finer grain.

 

[fitzo]

Welcome to BladeForums, Keanen!

If you have a furnace with one of the fancy ramping controllers, look in the directions for something called "autotune". If it's there, run it.

Usually, I'd suggest a second thermocouple/digital temperature device and a little hole here or there. I have a 1/4 inch hole drilled in the door and about 3/4 of the way back through the top of my Evenheat. 18 inch long thermocouples. It gets expensive. Keep it in mind for later unless you keep having problems with other steel.

As for your steel: I would ask of those here who would know - is this one of NJSB's steels that comes from Europe heavily spheroidized and needs special treatment?

 

[Keanen]

When you are hardening the steel, you are bringing up to a critical temperature where it transforms from ferrite to austenite.

We call this "austenitizing"

When we cool fast (quench) from austenitizing, there is some residual austenite left over that did not transform into the harder phase (martensite)

We call this retained austenite. It is soft (15 HRC)

The temperature used for austenitizing is a major factor for how much or little retained austenite (RA) is left in the structure.

Yes, austenitizing at too high of a temperature will cause excessive carbon in solution and will interfere with the transformation to hard phase.

We call this "over austenitizing"

There are other problems from over austenitizing also such as enlarged grains and plate martensite but I'm skipping that for brevity.

Since you have an Evenheat klin you can combat this by soaking at the proper temperature and even further refine with cold treatment.


But cold treatment can't make up for over austenitizing.

The key take away here is that the prior microstructure before austenitizing has a HUGE effect on the austenitizing temperature needed.





You are not wrong, but that is used for resetting the microstructure after forging. However, since you are doing stock removal, it is technically unnecessary.

If you are going to do normalizing and a grain refining cycle, it will be important for you to also spheroidize the carbides to stabilize the amount of carbon your putting in solution with a soak.

With the current steps you did, you're starting place before hardening was fine pearlite which Is ideal for doing a forge heat treatment with little soaking. However, with doing a soak, the pearlite dissolves carbon rapidly which can lead to over austenitizing especially at 1475f with thermal cycling.

Another factor working against you is that 1084 is an extremely shallow hardening steel which requires an extremely fast quenchant. It should be noted that parks 50 is at the very edge of being able to harden 1084 and should be done in thinner cross sections.

The normalizing and cycling that you did will even further reduce the hardenability

Finer grains make it difficult to out pace diffusion, and in this case if you are getting diffusion during quenching you are creating very fine pearlite (40 HRC)

So, all those factors combined will lead to the problems you experienced.


Ways to circumvent this

1. Don't use normalizing and grain refinement with 1084 stock removal. (Also 1490f is too high)

2. Use a steel with better hardenability such as 80Crv2, 52100 etc then you can normalize and grain refine to your hearts content (don't forget to anneal to spheroidize carbides before austenitizing)

3.For 1084, use an anneal to spheroidize after normalizing, adjust the austenitizing temperature to account for overaustenitizing due to finer more easily dissolved carbides and use a even faster quenchant such as brine to get diffusionless transformation which will be hindered by finer grain.

Thank you so much for detailed reply. That's what I was looking for. I want to understand what is happening with the metal, not just how to get the results. I really appreciate the details.

 

[Keanen]

Welcome to BladeForums, Keanen!

If you have a furnace with one of the fancy ramping controllers, look in the directions for something called "autotune". If it's there, run it.

Usually, I'd suggest a second thermocouple/digital temperature device and a little hole here or there. I have a 1/4 inch hole drilled in the door and about 3/4 of the way back through the top of my Evenheat. 18 inch long thermocouples. It gets expensive. Keep it in mind for later unless you keep having problems with other steel.

As for your steel: I would ask of those here who would know - is this one of NJSB's steels that comes from Europe heavily spheroidized and needs special treatment?

Thanks, I have the TAP controller on a LB18. I will have to look for the autotune feature. Thanks.

I've considered a thermocouple, but I'm hoping to not have to go that route. Thanks for the reply!

 

[DeadboxHero]

Thanks, I have the TAP controller on a LB18. I will have to look for the autotune feature. Thanks.

I've considered a thermocouple, but I'm hoping to not have to go that route. Thanks for the reply!

The TAP controller algorithm doesn't have or need an "autotune" feature.

 

[fitzo]

There’s your answer about TAP and autotune! Lotta knowledge here.

Another suggestion - a book by a forum frequenter. Knife Engineering by Dr Larrin Thomas. You can peek at it at Amazon. You can understand the wealth of knowledge it entails by reading at Larrin’s Patreon, knife steel nerds. Look it up if you haven’t heard of it before.

Good luck!

 

[DeadboxHero]

Thank you so much for detailed reply. That's what I was looking for. I want to understand what is happening with the metal, not just how to get the results. I really appreciate the details.

If you apply that mindset to whatever you do and stay consistent. You will be the best at whatever you put your mind to.

Good luck. Work hard. Have fun.

 

[Seedy Lot]

How to Thermal Cycle Knife Steel - Knife Steel Nerds

Experiments and recommendations on how to process steel after forging. Hardness, toughness, microstructure. Some controversial conclusions!

knifesteelnerds.com

 

[DevinT]

Hold up, how did a fifteen year old get his own heat treating furnace?

What part of the country do you live?

Smart kid right here.

100 blades already, good job .

Hoss

 

[Keanen]

There’s your answer about TAP and autotune! Lotta knowledge here.

Another suggestion - a book by a forum frequenter. Knife Engineering by Dr Larrin Thomas. You can peek at it at Amazon. You can understand the wealth of knowledge it entails by reading at Larrin’s Patreon, knife steel nerds. Look it up if you haven’t heard of it before.

Good luck!

That's good to know!

I actually have that book and read it nearly every day. I have learned a lot from it! Thank you!

 

[Keanen]

How to Thermal Cycle Knife Steel - Knife Steel Nerds

Experiments and recommendations on how to process steel after forging. Hardness, toughness, microstructure. Some controversial conclusions!

knifesteelnerds.com

Thank you. I like Larrin Thomas. I have his book and use it almost every day!

 

[Keanen]

If you apply that mindset to whatever you do and stay consistent. You will be the best at whatever you put your mind to.

Good luck. Work hard. Have fun.

Thank you. I am trying to learn as much as I can. Metallurgy is my favorite thing to study!

 

[Keanen]

Hold up, how did a fifteen year old get his own heat treating furnace?

What part of the country do you live?

Smart kid right here.

100 blades already, good job .

Hoss

Thanks! I am homeschooled and work on my family's farm and have been saving all year for a kiln. We found one on marketplace and I paid for most of it and my parents loaned me the rest. I am paying then back every month when I get paid. Thankfully my parents are a nice loan service! I live in Ohio.

 

[DevinT]

Thank you. I like Larrin Thomas. I have his book and use it almost every day!

Larrin is my oldest son.

Hoss

 

[DevinT]

Thanks! I am homeschooled and work on my family's farm and have been saving all year for a kiln. We found one on marketplace and I paid for most of it and my parents loaned me the rest. I am paying then back every month when I get paid. Thankfully my parents are a nice loan service! I live in Ohio.

Too bad you’re not closer to Nevada, I’d help more.

Hoss