2 questions from a newbie

[WalterDavis]

Hey all, I just finished my first few knives and I am definitely in the running for that ugliest knife contest! Aside from being absolutely hideous, after finishing them I realized I jacked up a couple of things on the heat treat and am wonderinging how it willl affect the steel (I am using O1). I tried looking up the answers here, but me and the search engine are having a bit of a disagreement today.

First, the oil that I quenched the blades in was probably too cold- somewhere between 30-50 degrees (garage is lacking heat). No cracking or warping, but could there be any other affect? And any ideas on an easy way to keep the oil at the appropriate temperature?

Second, on the second tempering cycle I kinda forgot about the knife in the oven! It ended up staying in there for about 4 hours. Any negative affects possible?

I appreciate any info I can get. Thanks for your time.

Walter

 

[rashid11]

If it didn't crack during quench or right after that and you tempered it, it should be fine.

Not sure about tempering for 2x of recommended 2hr. Is it hard enough for you ? If yes, keep it.

O1 is very forgiving type - you can re-heatreat w/o normalizing, if you're
not sure about it.

To have oil warm - I put reqd amt into baking pan and warm it up
on stove or inside of me electrical oven. To where it is warm.

Those baking pans are excellent for quenching. Quite a variety available
@ your nearby Shoprite etc - tall/shallow/narrow/wide etc.

 

[DAMNENG]

The difference between one hour and two hours on the temper cycle probably didn't make 2 points difference on the Rockwell C scale, and if I had to guess I'd say maybe even less.

Cold oil is a slower quenching medium than 120 to 130°F oil. Big reason is the hot thin oil circulates fast enough to keep cooler oil flowing past the blade surface, where the cold thick oil moves real slooooooow and get real hot next to the blade.
I used to put my quenching pan on a lab hotplate and heat it. Took about an hour and a half. Now I take a 2" x 1/2" X 6" piece of steel barstock, stick it in the forge until it starts getting red around the edges, pull it out and hold it till the red dissapears, then stick it in a gallon of oil, unitl the bubbles stop. This will raise the temperature of the oil from 55 to about 140°F. If I want it cooler I can add oil or wait! If it isn't hot enough I can go again with a different chunk of steel. Takes about 5 minutes total.


Jim A.

 

[rashid11]

Yes, excellent point . Must remember it well 'cause it is counter-intuitive.
One'd think that colder medium would quench faster compared to warmer
one.

Not so with oil. So you warm it up NOT in order to reduce thermal shock
from cold oil, but rather for the opposite purpose: make it quench faster as
compared to cold oil.

 

[WalterDavis]

Good info, thanks guys. I like the idea of heating up a second piece of steel and using that to warm the oil. I'm using a baking pan w/ a fairly shallow amount of oil and just doing an edge quench on the knives, so that ought to work pretty well for me. I went ahead and put a handle on the knife that was left in the oven too long and I'm going to try it out and see how it holds up edge-wise. These first few are just experiments in that department anyhow, once I'm pretty sure of the steel I'll work on making them presentable.

Thanks,
Walter