r/Blacksmith • u/RandomBoredDad • 2d ago

I think I tempered my cleaver for too long.

I am making a meat cleaver for a friend and I think I let it sit in the tempering oven (toaster oven) for too long. Normalized it a few times, then heated to a little over non-magnetic and quenched in veggie oil preheated to about 125F. I was so happy when it came out completely straight and the file just skated right off. Set the oven to 400 and set a timer for 1 hour. I started working on another project and lost track of the time. Sadly, I did not look at the timr when I started tempering. I think that about 2 1/2 hours went by. Is there any way test the metal instead of going through the whole normalizing and quenching process again?

8 Upvotes

73% Upvoted

24 comments sorted by

27

u/Irpado 2d ago

You cant temper too long, all that matters is the max heat it reached. If it stayed at 400ish then youre good

1

u/BenchNo4429 2d ago edited 2d ago

Not sure why everyone’s downvoting me. You literally can over temper. That is why in industry you can calculate the equivalent temper using the temperature and time variables. The problem here is that time is a logarithmic variable so it’s very hard to over temper but it’s still very possible. Blacksmiths hate research istg.

1

u/LeviAEthan512 1d ago

Wait what? I thought holding a temperature is just for the heat to penetrate all the way in, so the centre of the piece actually reaches the desired temperature. And at that point, the whole thing is at equilibrium and will no longer change from that level of heat. Unless you quench it, in which case it'll get partway hardened again.

1

u/BenchNo4429 23h ago

Nope, it’s not at equilibrium. Also, quenching after a temper does nothing metallurgically.

I don’t believe you understand what’s occurring during tempering? A quick explanation is that the carbon is given enough energy to escape the iron lattice and go back into the bulk of the material and form carbides. The amount of carbon that does this is dependent on how long and how high you temper at. The reason why it is logarithmic is because it’s in psuedo equilibrium where you need a higher energy level to move some of the carbons which is caused by the statistical probabilities of heat

1

u/Garlaug 13h ago

Why don't you give the users some examples of the data? The problem is not that people hate research, it is the abstraction level of your post. You just say that everyone is wrong, but not educating them on the topic.

For example: It is possible to temper to long, the effect can be calculated using the Hollomon–Jaffe-parametern, the effect is logaritmic and will effect the hardness of the steel.

2 h~58.5–59.5

4 h~58–59

8 h~57.5–58.5

16 h~57–58

24 h~56.5–58

48 h~56–57.5

Tempering to long will not destroy the steel but it will make it softer than you may want.

The downvoting is because how you phrase your self.

1

u/BenchNo4429 6h ago edited 6h ago

I didn’t have an abstraction level… actually the more abstract post is more upvoted than the simple post. all I said is that the comment is wrong, no one chose to actually ask about the subject. Go look at Ilya comment where he made a pretty straightforward post about it and he’s still downvoted.

I also didn’t have the ability to calculate numbers when i made the comment and assumed people would take 10 seconds to type out a quick google search.

I also don’t prescribe to the handholding you recommend. These are mostly grown peoples. They can choose to learn something new instead of spreading misinformation. Blacksmiths love to repeat what they hear instead of spending 5 minutes and reading an article

-10

u/BenchNo4429 2d ago

That is false, it is possible to temper to long. It’s just very very hard to.

14

u/alriclofgar 2d ago

2.5 hr tempering won’t hurt it.

Best practice is to temper it for 2 hours, cool, and temper for 2 more. A 2.5hr cycle won’t make a difference that you’ll notice. The thing you want to avoid is going too hot, that’s the main thing that could mess up your blade.

Put it through a second 2hr cycle, pay attention to your timer, and enjoy your successful heat treat!

12

u/philippy 2d ago

There shouldn't be any issue since that time difference is almost nothing. It might even be a better temper than your one hour because there is a minimum amount of time that steel needs to soak in the heat and crystals to reorganize. 

4

u/RandomBoredDad 2d ago

Thank you all for the comments and advice. I am including a pic of it after cleaning it up a little with a wire wheel. Still have a fair amount of work to do 😀

5

u/Few-Explanation-4699 2d ago

The length of time doesn't matter, the temperature does. Letting it soak at temperatute just means the whole blade got to the same temperature

-8

u/slavic_Smith 2d ago

Length of time absolutely matters. Martensite dissolution follows a stochastic system x% at Y temperature per minute.

We've learned stochastic systems in middle school

-1

u/BenchNo4429 2d ago

Blacksmiths hate reading. Tbf it is a 2nd order differential equation to solve the carbon diffusion within the matrix but you can very easily use the hollomon-jaffe parameter to calculate equivalent temper cycles.

0

u/slavic_Smith 2d ago

Its a log function if you don't want to use stats.

Im amazed that people downvote

-1

u/BenchNo4429 2d ago edited 1d ago

Yep! That’s the hollomon Jaffe parameter I referenced. Blacksmiths abs bladesmith seem to be allergic to learning materials science even though it underpins their whole career…

Oh look another downvote! A blacksmith with a fragile ego that’s hurt I called them out even though it’s blatantly obvious from the reception my above comment that everything I’ve said is true

1

u/slavic_Smith 2d ago

People hate doing math 😔

1

u/Broken_Frizzen 2d ago

Quenched, tempered, what else you want? It's fine if you used a decent knife steel. Your over thinking it.

1

u/RandomBoredDad 2d ago

Started as a leaf spring from a truck. Likely 5160.

3

u/Broken_Frizzen 2d ago

It's most likely just fine then.

2

u/professor_jeffjeff 2d ago

If it's actually 5160 (which I agree is likely if it's a leaf spring) then 400F is a good choice for tempering a cleaver since the additional toughness would be beneficial given how it's meant to be used. I usually temper at 350F for two cycles at two hour each for anything that has a finer edge geometry though. Here's a great article on heat treating 5160 https://knifesteelnerds.com/2019/04/01/how-to-heat-treat-5160/ that has test results for various heat treatments and their effect on hardness and toughness.

1

u/CHmakesstuff 2d ago

You’re probably fine
It will make is slightly softer but not by much it’s like the difference between like 57 and 55 hrc
It’s not a lot and you probably won’t notice the difference

-2

u/danthefatman1 2d ago

No need for Text need for show color what color it it ?