# How to Thermal Cycle Knife Steel (article and video)



## Larrin (Aug 28, 2021)

Experiments and recommendations on how to process steel after forging. Hardness and toughness measurements along with images of the microstructure. There is a YouTube video as well as an article that has more details.

Article: How to Thermal Cycle Knife Steel - Knife Steel Nerds

Video:


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## Kippington (Aug 29, 2021)

I can't even begin to imagine the amount of work that went into this. Thank you for sharing!


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## captaincaed (Aug 29, 2021)

Vid was great, as was the recent interview. Love the combination of simplicity without sacrificing detail.


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## inferno (Sep 11, 2021)

hi larrin. i'm working with 52100 now. from large diameter round bearing stock. so i have to flatten these. i take these up to yellow with acetylene. so it i can bend/bang them straight.

tried to simply take these to unmagnetic once, then air cool. then harden. 1 shade above unmagnetic. warped like fukn crazy. and it was totally unusable. 
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then tried a very high temp one shot "normalizing" with acetylene after flattening. to get all tensions out. up to maybe light yellow. almost white.

then 3 cycles to just above unmagnetic, then air cool. in open air. now, hardening these i take them to like 1-2 shades above unmagnetic. dunk in a mix of hot hydraulic oil and motor oil. comes out hard as glass. and cracking these parts shows a grain size of almost 0. i cant ever see any grain. its just dull gray.
but its 0% unrepeatable i guess. i do this all by eye. with acetylene and propane.

after tempering 2x at 180C my bacho files just skid along. 

yeah thats some anecdotal data for you. i feel i did good though.


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## inferno (Sep 11, 2021)

hey if it works it works.


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## Larrin (Sep 13, 2021)

inferno said:


> hi larrin. i'm working with 52100 now. from large diameter round bearing stock. so i have to flatten these. i take these up to yellow with acetylene. so it i can bend/bang them straight.
> 
> tried to simply take these to unmagnetic once, then air cool. then harden. 1 shade above unmagnetic. warped like fukn crazy. and it was totally unusable.
> ---------------
> ...


The term is nonmagnetic rather than unmagnatic.

In the first case you heated to nonmagnetic instead of normalizing? Why?

Why are you heating with an acetylene torch? That leads to uneven heating which then leads to warping, etc. 

Why use hydraulic oil/motor oil? 

Why create extra problems for yourself?


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## inferno (Sep 16, 2021)

Larrin said:


> The term is nonmagnetic rather than unmagnatic.
> 
> In the first case you heated to nonmagnetic instead of normalizing? Why?
> 
> ...



yes of course is nonmagnetic 

i had already taken the steel way above nonmagnetic, around forging temps i guess, when flattening it.
then i took it just above non magnetic once. and it didn't work out. it warped in the quench.

i use the acetylene because its free and i do it at work. when i get payed.  and its fast. very very fast.

i use hydraulic oil and motor oil since this is what i have access to for free.

because free is free. 0 money spent. and its even better if i can do it all at work.


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