Tempering 1095/15n20/1084

[Gayton Arrigotti]

A quick question......If you get into the blue color on tempering should you start over and quench again?

[Jerrod Miller]

It is impossible to say what the actual temper is like since tempering colors are in no way accurate.  Otherwise, the temper temperature needed is going to depend on what you want for a final outcome, which will depend on the style of blade (e.g. paring knife vs machete).  

[Gayton Arrigotti]

Ok .........Its going to be a simple kitchen knife......I took a file to the edge and its a bit sticky?.

              I want it to sharpen easily with a steel...............

 

[vlegski]

Don't confuse the colors your steel achieve during an oven tempering or even in a forge with tempering by as they say running the colors. Steel oxidizes as its heated and any contamination on the steel causes different colors.  If you Tempered it again and the colors would change. 

As far as hardness that's going to depend on the tempering temperature, the type of steel. Was this steel you made,  or did you buy an unknown steel online? Did you use Fahrenheit or centigrade. 

Too many unknowns to give a answer.

[Jaro Petrina]

Quite honestly, even if the colours of steel differ according other factors rather than actual temper, they might be quite consistent if you have surface treated the same way every time.  That means you grind with the same grit and you set up the same temperature on the kitchen owen and you get roughly same temper. IMHO the colour tempering was done for about two millenia with good degree of sucess. I have friend who makes swords and he quenches and tempers 5160 with razer amazing consistency. But he also knows his product. On simple steels this is a no brainer, on 52100 it starts to be kind of dificult.

 

Edited February 18, 2022 by Jaro Petrina

[Jerrod Miller]

6 hours ago, Jaro Petrina said:

IMHO the colour tempering was done for about two millenia with good degree of sucess.

That is very well documented to not be true.  Medieval era blades have been tested and shown to be all over the place for chemistry and microstructure.  Historically blades were terrible compared to what we can achieve now, and the average modern person expects more performance quality than they did back then (because it is more possible now).  

[Gayton Arrigotti]

The steel was new from reputable company selling metals and knife making goods.

I made the billet and I use Fahrenheit. My toaster oven was originally set at about 400 degrees and nothing much was happening visually so I set to around 440 degrees

and blue violet and red appeared.

[Jaron Martindale]

If you're using a toaster oven (me too ) I got advice that has saved  quite a few blades from accidental under/over-tempering: get a candy thermometer.  Most are rated at or above 500 deg (way over what any reasonable blade needs), for mostly continual use, and tend to be accurate since candy makers need to the degree accuracy.  Many will also recommend putting a pan of sand in the oven for thermal mass to help keep the temp even throughout the temper cycle since the oven will cycle on and off frequently.  Right now my oven is behind 40-50 deg of what the knob says, so setting it to 425-ish will put me right around 375-380.  I might try setting your oven to the temp you used again and measure with a thermometer what heat you were tempering at and determine if it got you into over-tempering range or if your oven is also a little behind like mine.

A far as color goes, everyone else has pretty much covered it.  I notice a large difference in the colors my 1065 will temper at vs 80CrV2 (seeing a large variety of colors in the 80CrV2, including blues/purple/bronzes) at the same temps, but like everyone says: your surface prep, heat-treat up to this point, and material choice all play a role in the colors seen.  I've even seen my fingerprints show up on a temper once, lol!!

[vlegski]

Jarons got some good advice.   I found my toaster oven ran 20f high.. Ive found that my damascus does well at 425 f in my oven.. I use 1080/4 and 15n20,  the occasional 1095. I get  good edges with nice edge retention in those temp ranges.

 

[Gayton Arrigotti]

I will get a thermometer that sounds like a good way to dial in an accurate temp. for my thrift store toaster oven.

 

[Alex Middleton]

Definitely recommend the oven thermometer, and the additional thermal mass added inside.  One other thing I'll add in is to not get comfortable setting your oven the same way every time.  Sometimes my oven is 50 deg. high, other times it's right on.  I've gotten in the habit of turning it on well before I start my heat treat process so I have time to monitor it and adjust the temp accordingly.  I've accidentally tempered a couple of blades too high.  Hardening a blade you've been working on for hours the first time is nail biting enough.  Having to redo it sucks even more.

[Alan Longmire]

26 minutes ago, Alex Middleton said:

Definitely recommend the oven thermometer, and the additional thermal mass added inside.  One other thing I'll add in is to not get comfortable setting your oven the same way every time.  Sometimes my oven is 50 deg. high, other times it's right on.  I've gotten in the habit of turning it on well before I start my heat treat process so I have time to monitor it and adjust the temp accordingly.  I've accidentally tempered a couple of blades too high.  Hardening a blade you've been working on for hours the first time is nail biting enough.  Having to redo it sucks even more.

 

+1!  My toaster oven temperature knob marking bear only the slightest relation to the actual temperature inside.  One day, the knob at 350 will produce 475, the next it will produce 230.  Once it went to 500 before I unplugged it.  I have slices of fireclay chimney liner on the rack to make a flat surface and thermal mass.  I start it at least an hour before I'm going to be tempering both to allow it to heat up and stabilize and to make sure the temperature is what I want.  A tiny tweak to the knob can change it by up to 50 degrees.

 

Now that I have an Evenheat blade kiln I rarely use the toaster oven, or I'd try to modify it with Joel's trick shown here:

 

 

 

 

[Charles dP]

Thanks Alan. I was looking for that a while back and couldn’t find it.

[MLeonard]

On 2/20/2022 at 11:51 AM, Alan Longmire said:

 

+1!  My toaster oven temperature knob marking bear only the slightest relation to the actual temperature inside.  One day, the knob at 350 will produce 475, the next it will produce 230.  Once it went to 500 before I unplugged it.  I have slices of fireclay chimney liner on the rack to make a flat surface and thermal mass.  I start it at least an hour before I'm going to be tempering both to allow it to heat up and stabilize and to make sure the temperature is what I want.  A tiny tweak to the knob can change it by up to 50 degrees.

 

Now that I have an Evenheat blade kiln I rarely use the toaster oven, or I'd try to modify it with Joel's trick shown here:

 

 

 

 

I made a PID loop for my toaster oven and it now holds + or - 3 degrees at 450.  I also cut up an old pizza stone to help retain heat.  I'm currently tempering my 1095 blades at 425 for 2 hours.  I have been having good luck in doing so.  I've been reading more and more about 2, 1 hour cycles.  Does it make that big a difference?  

[Alan Longmire]

1 hour ago, MLeonard said:

I've been reading more and more about 2, 1 hour cycles.  Does it make that big a difference?  

 

It helps transform any retained austenite, which if left alone will stabilize.  How big a difference it makes depends on how much retained Austenite you have to start with.  In the first cycle, you temper the martensite. Upon cooling, some of the retained austenite (if any) will transform to untempered martensite.  The second temper takes care of that untempered martensite, making your blade tougher for the same hardness.  

 

Retained austenite left for around an hour after quenching will stabilize as austenite, even at tempering heat.  This decreases toughness and overall hardness. Thus the temper immediately after hardening, and two one hour cycles rule. 

 

Note this is for carbon steels only.  Stainless alloys each do their own thing. For AEB-L, for instance, the factory recommends a single two-hour temper.