How Far Should I Go?

my point was just that I think the pizza oven was better than I thought. I'll be doing another batch soon and I feel I kinda know what im doing now. I might better than a toaster oven?
Thanks, this is a blast!
 
475, is starting to creep very close to the area of tempered martensite embrittlement. If there is a chance it will get any hotter than that, i would be very careful of alloy choice, and temperature.
 
docmott said:
so far ive done 2 batches of knives in the oven. the first was kinda learning, I wasn't sure what was going to happen. the first attempt I made the temp a little high expecting it to lower some. it didnt. so first batch and 2nd tempering I let it cool to a hair over 400dg. closed it up and checked every 20min or so. after 2hr the temp was just the same. I guess it works. on the 2nd batch of knives I let the fire kool to just over 400dg. put them in and closed it up. I checked every 20min or so. all fine. after 2hr I pull them out to cool. put a little wood in the fire, it didnt take much and it was up to 600dg. I busted it up and let it go about 20min and it was down to 400dg. put them in and closed the door. the temp went up a little? not over 450dg so I just opened the door and let it go down to 400dg. closed the door and checked every 20min, it stayed there until 2hrs was up. im just figuring it out. I think the is the rate. for KWH $38.84
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38.84 cents per KWH.
 
Blankblank said:
475, is starting to creep very close to the area of tempered martensite embrittlement. If there is a chance it will get any hotter than that, i would be very careful of alloy choice, and temperature.
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ok thanks, I'll keep it at 400
 
Just an update, over the weekend I heat treated and tempered 8 knives. Again I got the wood fired oven going and not paying action I let the fire temp get too low. stoked the fire and got it steady at 500dg. once it started dropping I moved the coals around and got it to just over 400dg. closed it up and checked it every 15min or so. for 2hrs it was steady at 400dg and just dropping a hair. I pulled them out and added some more wood to the fire. the second batch was a breeze, the temp stayed at 400dg for 2hrs. the trick is get it hot and let it just cool down. ive done it the other way by adding wood and getting it up to temp and closing it up. the bad thing is it can get hotter if it gets some air. Happy New Years!
 
Lots of good info on HT here in many ways. Back to your original concern of grinding time and thicknesses, I want to make a suggestion. Starting at 100 grit is too fine imo and I think that’s why you want to go more pre HT. You put a lot of heat in to the system when grinding for profile at that grit and hardness only exacerbates that point.

I start at 36, then 60, then a small amount at 120 for bevels. Maybe give that a shot and keep your other HT methods ?

My 2 cents 😊
 
Ok good info, thanks. I think I need to bevel a little more too getting the blade a little thinner. the finish bevel feels to steep to me?
 
Blankblank said:
475, is starting to creep very close to the area of tempered martensite embrittlement. If there is a chance it will get any hotter than that, i would be very careful of alloy choice, and temperature.
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TME starts at 575°F.
A 475° temper will not approach TME.
However, the drop in the tempering curve for 1095 is right at 450°. It is Rc62 around 450° and drops about one point more at 475°, then starts dropping faster.

I use 425° for 1095 and get around Rc 63-62.

All the above assumes that it was fully and properly heat treated before tempering. If using a forge don't expect these results.
 
Now im starting close to 425dg and it holds close to 400dg for 2hrs. thank you for the info !
 
Hey Doc, I see you are 73. I turn 73 in 19 days.

Don't sweat 25° either way, as it will make 1 point of hardness difference at the most.

The best way to dial in the tempering is by comparison.
Take three bars of the same batch of 1095 steel (.10X1"X6" is good). Don't do more than clean the surfaces off and round three corners a bit. Scratch or stamp a letter or number on the end with two round corners to tell which is which later. Do the best hardening and quench you can on all three. Then temper one at 400° (twice), one at 425°, and one at 450°.
Grind the edge with a 90° corner back 3" in a FFG bevel on each test blade. Dip in water often to avoid burning the edges. Sharpen all three at around 10DPS. Test all three and compare results to pick which temper works best for your equipment and process. Stick with that temperature from there on.

Good tests are the brass rod test, cutting cardboard, manilla rope, and carving on wood. Examine the edge regularly to see what damage is done.

Save the three blades as bench knives. Put duct tape or electrical tape on the handle end.
 
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I like that, I have some 1095 1inx8inx1/8, after I finish what I got going I'll give that a try. so one at 400 twice, one at 425 once, and one at 450 once.
Happy Birthday !!
 
someone said they do all beveling after heat treating. I saved one blank out to give this a try, we'll see?
 
No, all are tempered twice - one at 400° one at 425°, and one at 450°.

With a mist system or regular dipping in water, doing the bevels post-HT is simpler.
 
Stacy E. Apelt - Bladesmith said:
TME starts at 575°F.
A 475° temper will not approach TME.
However, the drop in the tempering curve for 1095 is right at 450°. It is Rc62 around 450° and drops about one point more at 475°, then starts dropping faster.

I use 425° for 1095 and get around Rc 63-62.

All the above assumes that it was fully and properly heat treated before tempering. If using a forge don't expect these results.
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Everywhere i see states for these steels right around 500 is when tempered martensite embrittlement starts. Maybe just under. Ive seen it nicknamed 500 degree embrittlement.

I couldnt find something directly for 1095 but i dont have any reason to believe it would start higher for that steel. I do recall 5160 can handle a bit higher of a temper before it starts. But i cant remember exacts.

Screenshot_20230103-202723.pngScreenshot_20230103-203135.png
 
We are talking about martensite, not bainite. Tempered MARTENSITE Embrittlement,
Also, TME is a time function as well as temperature. It takes longer soaks (over one hour) to even start TME. It doesn't destroy a blade, just lowers the toughness.

Yes, I see some information that TME stars as low as 480°, but for practical purposes, it takes more than that temperature and longer time to get a significant amount. One reason I recommend rapid cooling from temper is it tends to reduce the effects of TME.

Perhaps Larrin will chime in with his POV.
 
Stacy E. Apelt - Bladesmith said:
We are talking about martensite, not bainite. Tempered MARTENSITE Embrittlement,
Also, TME is a time function as well as temperature. It takes longer soaks (over one hour) to even start TME. It doesn't destroy a blade, just lowers the toughness.

Yes, I see some information that TME stars as low as 480°, but for practical purposes, it takes more than that temperature and longer time to get a significant amount. One reason I recommend rapid cooling from temper is it tends to reduce the effects of TME.

Perhaps Larrin will chime in with his POV.
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It wont destroy a blade, but a blade that is softer, and less tough. I think i would consider a worse blade than one not suffering from tme.

And i know we arent talking about bainite. That article is on bainite, but it is also talking about tme. If you want more context you can read the entire article. https://knifesteelnerds.com/2021/06...ents-of-52100-o1-and-1095-how-much-toughness/
 
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