funky flats

[balibalistic]

Hey Fella's,

i just finished doing my first heatreat on 440c.

I've finish ground the blade,bevel's and flats.for some reason the flats
have some wierd sqiggly lines through out.these were here prior to
heatreat,and are still visable when the light hits it at certain angles.

i know the blade is hard!! i heatreated it at 1875,held for 25 minutes,air
quenched under fan (no quench plates yet).then tempered twice at 375
for two hours each time.

Is some steel just like this?I'm a newb so kind of puzzled by this?

[Ray Rogers]

Yup, 440C is like that. For most types of knives a temper of 375 would probably give you too high a working hardness in 440 C for reliable durability. Since your knife appears to be a balisong this may not matter because the knife may not be used in a utility fashion. If it is used for hard work you may experience some edge chipping at that hardness, especially in a hollow ground blade ...

[balibalistic]

Thanks for the info Ray!you are correct..,this is a bali,and deeply hollow ground!i intended it to be a slicer for envelopes,letters,packages etc!i got my heatreat info from a combination of threads on this forum.i simply took the majority and devided it all :-) for a hard user should i bump the temper up to 400 twice at 2 hours each?i did'nt want to start a thread asking what has already been asked..lol.. i will be heatreating an (EDC) blade this weekend,so i'd appreciate any info.

[Ray Rogers]

440C is one of those steels that has a large number of possible heat treat processes and most of them work just fine. For instance, you used a fan cool but I use still air, you used 1850 F but I use 1875 F and we both seem to get good results.

Testing your blades, often to destruction, is the only way you'll really know exactly what is working for you and you're particular process. But, each steel has a maximum working hardness for a given application and I feel like 375 F is easily pushing it in this case. At 375 I would get a hardness in excess of 61 Rc, at 400F I get about 60, and at 425 mine drop to around 59. For a really hard use knife in 440C I might even go 450 F for Rc 58. Your mileage may vary, as they say. Generally, I use 425 and do it twice for an hour each time.

440 steels have a bad rep because they get used in many cheap commercial knives and most of the time it's 440A or 440B. Even when 440C is used the heat treat is usually inferior. So, even if you make your blades to Rc 58 the chances are good it will far out perform a commercially made 440 blade.

BTW, 440C benefits greatly from cryo and the numbers I gave you were from cryoed blades. Cryo adds considerably to the toughness of stainless blades. This means that at these tempering temperatures, your hardness may be a point less than mine (if you don't cryo) and thin edges even more likely to chip. Home brewed cryo using dry ice isn't too expensive so when you want the most from that steel you might consider looking into it. Do a Search for dry ice and kerosene ....

[balibalistic]

Thank's so much,Ray!! i just pulled blade out of the oven and will temper twice for 1 hour each at 425 F.i'd like this blade around 58.

i plan to do cryo..,just hav'nt worked up to that point yet.will post finished photo's..,just for kick's!

[Ray Rogers]

Ooops! Typo......I should have said temper for two hours each time....mea culpa.......

[balibalistic]

Ok..,thanks Ray!

[balibalistic]

Heatreat turned out very well..,thanks again Ray!



my first sole-authorship knife is sharper then all hell