Rsparozi

Tempering 1095 blades to blue

Recommended Posts

Good Evening all and Happy Holidays...

I have a concern regarding two 1095 blades I recently heat treated. I’ll give a little background on the process I performed so you get a more complete picture. 

Both blades are stock removal from 0.156” 1095. I attempted creating hamons on each blade using high temp furnace cement. After grinding the blades to shape, I normalized four cycles from non magnetic working the temps down to a very dull red almost black heat.  Once cool to the touch, I applied the high temp furnace cement and let sit for nearly two days. For the quench, I used warmed canola, took the blade up to non-magnetic, let it sit for another ten seconds, and quenched. Files skated, blades hardened to my level of satisfaction. Here’s where I’m concerned that I screwed up. Preferring a more durable knife and willing to give up some hardness, I set the tempering oven to 475F, and left the blades for an hour and a half. The photo below shows my colors after the hour and a half. My concern is, I’ve never taken a tempering cycle to blue, I usually prefer dark straw at the edge. Did I over-temper these? I was looking for a hardness around 59-60 RC.

Any advice or experience would be greatly appreciated.

Best,

Rick

32D4EB2F-5A41-458C-8140-4AA247C77E1A.jpeg

Share this post


Link to post
Share on other sites

Color temperature is a form of surface change and doesnt indicate much, except in cases where you heat a part like the tang and let the color shift up the blade, because then it is an indication that the steel has heated like a thermometer. Blue is usually at a temp of 590. the air in your oven is usually much hotter then the temp setting, while the object may only heat up to the setting because it has to absorb that heat, especially near the coils. so you blade may be blue colored and light blue colored, but it doesn't mean your blade was tempered to 590.

did you quench the tempers at all?

Share this post


Link to post
Share on other sites

Thanks for the reply Sly, for clarification I didn’t quench the normalizing heats or the temper. The normalizing heats I allowed the blade to go to black heat, and on the temper - I only did one so far - I pulled the blade from the oven and let it cool wrapped in a blanket down to room temp. I also find it interesting how there’s such a distinguishable color line at where the clay covered the blade. The dark straw at the spine would have been my preferred color, but it seems the color is independent of blade thickness and more related to the steel type. While all this leaves me scratching my head a bit, I have to admit it only pulls my fascination with blades and metallurgy a lot deeper. Looks like I’ve got some reading to do.

Share this post


Link to post
Share on other sites

Here's my 2 cents.  If those were my blades I'd check them with a file.  If you have a set of hardness files that would be best.  If not, I'd just check the cutting edge with a normal file.  If it skates or barely bites I'd probably continue to finish the blade.  If the file were to cut in significantly I'd start the heat treatment process over.

I've learned to distrust the temperature settings and readings on ovens, especially toaster ovens.  I bought a cheap oven thermometer which I place in the oven roughly where the blade will be for tempering.  I then adjust the oven temperature until I get the reading I want on the thermometer.  It helps to have something with a bit of mass to retain heat during the off cycles.  A pan filled with sand will suffice.  Once you can maintain the desired temperature, then you can place the blade in the pan of sand for your desired amount of time and be fairly confident that you have tempered at your desired temperature.

Share this post


Link to post
Share on other sites

Great advice guys, thanks. I checked them with a file, skated right over. Went back to the annealed piece of 1095 for a reference feel and can easily feel the difference. Not worried about these being hard anymore, so I’m gonna finish them. I bought a cheap oven thermometer at WalMart today that goes up to 500F, from here on I’ll be double checking my oven temps like you recommended. Really appreciate everyone’s input, thanks again.

Share this post


Link to post
Share on other sites

Tempil sticks and thermomelt sticks are another way to check temperatures.  

 

Share this post


Link to post
Share on other sites

Yes I’ve heard about those as well as the knife hardness files. Seems as though they are a worthwhile investment, especially if the intent is to one day sell knives as a source of income. If anyone knows of a good product from a reputable source for either I’d be interested to hear, otherwise it’s USA knife Maker or Knifekits.com!

Share this post


Link to post
Share on other sites

Good Morning All,

I thought it would be nice to post a pic of one of the finished knives in question from my original post. For me personally in my novice state, its not a bad knife, it’s probably my most technically complex to date with the gut hook, differential heat treat, and pinned hidden tang with the contoured G10 handle, and for that I’m very proud to create something that was better than my last blade. I had to add the black spacer which was unplanned due to some wobble, but I like it as an accent piece. It is far from perfect, but Rome wasn’t built in a day, and neither will my skills as a knife maker come to full maturity over the course of making a single knife. I can’t crush myself for not producing a flawless knife when I’m just still very much a noob. I’ve acquired a lot of new skills I plan carrying forward, and intend to improve on each of them on the next knife. Thank you to all the took the time to comment and offer up advice, it’s really appreciated, and has not fallen on deaf ears.

Happy Holidays!

1D418642-D3DB-4D28-B08D-16C9E625CB5B.jpeg

Share this post


Link to post
Share on other sites

you never want to quench the normalizing heats but quenching the temper is always a good idea after it is finished, in some cases it can add extra martensite. If youre using propane then you need to set the temp in the forge to sustain an austenizing temp for about 30 minutes, the purpose behind this is that you will allow the austenite to fully form and alleviate stresses. if youre using charcoal then you will want to thermo cycle it by evenly heating the blade and then letting it cool to glowing red and repeating the process till at least 3 times for best results, charcoal isnt exactly an even heat so air cooling the steel allows for the heat to disperse evenly, it still applies with propane but its less relavent when you can simply sustain a temp.

Where the color scheming comes into play is for the traditionalists like myself who use the forge itself to temper the blade, in which case the steel is being exposed from 1000-2000 degrees of heat to temper it depending on the method and the heat has penetrated the steel quite efficiently, it doesnt work if there is a simple exact tempering temperature of heat in which case time is required to diffuse throughout the blade and allow the martensite to breath as it were. If I can put it in an oven afterwards I still do it.

It looks like a decent knife, hand made objects will always have intrinsic value, I still carry and use my first shoddy knife.

Hope that helps.

-Sly

Edited by Sly

Share this post


Link to post
Share on other sites

I use my forge to temper blades---I heat the tempering tongs in the forge! (I bought a set at the local fleamarket for US$5 nobody recognized  what they were!)

Share this post


Link to post
Share on other sites

Good evening everyone, hope you had a productive weekend.

Just following up, I tempered another stock removal blade from 1095 this evening. As was recommended a few weeks ago, I purchased an oven thermometer to confirm what temperature range my oven would cover over the course of the 2 hour temper. I set the oven to 400F, brought it up to temp, put the blade and the probe in. The results were nothing short of shocking. Over the two hour time frame, the oven ranged from 387F up to 458F. I can’t imagine those fluctuations are anywhere near acceptable. Needless to say, from here on out I will do what Buzzkill recommended and fill a pan full of sand to add thermal mass to help stabilize the temperature fluctuations. Thanks for everyone’s input, great advice all around.

 

Share this post


Link to post
Share on other sites

Good Evening,

I hope I’m not dragging this thread along, but I thought it would be a good update. I purchased the hardness testing files from flexbar and tested the knives from the original post, the ones that tempered to blue. Looks like they tempered somewhere between the 50 and 55 files. Great recommendation to go for the hardness testers, will help me to refine my heat treating process.

Share this post


Link to post
Share on other sites

using 1095 you should be able to get those blades up to the next file of hardness eventually. Dont be afraid to soak hypereutectoid steels for 5 minutes before the quench

Share this post


Link to post
Share on other sites

I’ve got some spare 1095 from the original blank, I think I’m going to chop it up and try different methods for treatment. I’ll give the soak a try Steve, thanks for your suggestions. For the sake of science I went thru every knife I’ve ever made since I started a few years ago, turns out heat treating mystery steel yields highly inconsistent results, even if they were all made from files. I got hardness ranges from above the 65 file down to between the 40 and 45 files. No more mystery steel for me.

Share this post


Link to post
Share on other sites

1095 has some issues... Its got a really low manganese content which attributes to hardenability, ductility and flexibility at the same time, and a rather low silicon content so its not nearly as durable and its niche in heat treatment. Its got low Si content as well fot a 10xx steel, if you want to regularly make knives i recommend getting some 1084, has three times the manganese and twice the Si so it heats so much easier without the fragility and the range of acceptable quench temps is more forgiving and on average its got twice the use toughness.

Otherwise soaking to austenize or thermocycling at higher heats is your best friend. Like steve said.

Share this post


Link to post
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now