How hot to ruin a HT?

res1cue

res1cue

Joined
Feb 2, 2010
Messages
2,138
I know that you don't want a blade to get too hot, or else you will ruin the HT. How hot does it have to be?

Up till now, I have been fighting to keep my GF from using my knives to cut meat straight out of the oven, and I am just wondering how high of a temp (ballpark is fine) before the HT starts being altered?
 
I heard over 300 degrees a long time ago one night when my father was talking with his buddies about making knives, have no idea if it's even close to right
 
It totally depends on the steel alloy and at what temp the alloy was tempered at. Damage only occurs if you exceed the tempering temp. In general anything under 375-400degrees won't change the temper of most steels. But then some steels are tempered at closer towards 1,000 degrees. So it goes back to the steel type.

Cutting hot meat won't hurt it.
 
I keep my nice kitchen knives, and other outdoor knives, out of the dish washer. There's quite a bit of heat there, micarta, wood, and other handle materials can start to seperate from the pins or tang.
I have heard that the heat from the dishwasher will alter the HT just at the very (thinnest) part of the edge. I have no info to back this up, nor any experience. I'd almost think the damage done from other silverware to the edge would be more a concern. Just look at most knives that go from the dishwasher to the drawer.

In the culinary industry, we cut hot meat all the time, can't say anyone ever noticed any issues. Plus, the rest of the knife acts as a heat sink, the handle doesn't get hot in the process. Yet, in the dishwasher, the whole knife gets very hot, grab some metal right out of the dry cycle, if it's too hot to touch, it could alter the HT at the edge.
Like said though, depends on the steel, the HT used, and the dishwasher.
 
foxx said:
I keep my nice kitchen knives, and other outdoor knives, out of the dish washer. There's quite a bit of heat there, micarta, wood, and other handle materials can start to seperate from the pins or tang.
I have heard that the heat from the dishwasher will alter the HT just at the very (thinnest) part of the edge. I have no info to back this up, nor any experience. I'd almost think the damage done from other silverware to the edge would be more a concern. Just look at most knives that go from the dishwasher to the drawer.

In the culinary industry, we cut hot meat all the time, can't say anyone ever noticed any issues. Plus, the rest of the knife acts as a heat sink, the handle doesn't get hot in the process. Yet, in the dishwasher, the whole knife gets very hot, grab some metal right out of the dry cycle, if it's too hot to touch, it could alter the HT at the edge.
Like said though, depends on the steel, the HT used, and the dishwasher.
Click to expand...


The problems with dishwashers have to do with the knives bouncing around banging into other steel knives, forks and spoons and the harsh nature of some of the soaps used.

It has nothing to do with the temp of the water used as it will never be hot enough to hurt the tempering of the blades.

Another common myth with zero truth that gets spread around.
 
It isn't the heat, it is the bouncing as mentioned above, but also the microabrasives in your detergent that will take the edge off your knife, will also take the anodizing off the aluminum.
 
Yeah, you have nothing to worry about. Now don't call me lazy but I think I am about to put my Rukus in the dishwasher, because I'm really sick now (hopefully just the flu) and the micarta scales are super dark, from oil. Heck a hard brush and acetone barely does much. I can always re-sharpen my blade.
 
I think the lowest temp at which you can anneal (blow a temper) a heat treated blade is 400 degrees, and it goes up from there. If you got a blade that hot, it would be glowing red so that puts it into perspective of just how hot that really is.

Also, a lot of people think that even if you don't reach the annealing threshold you can still damage your knife by "soaking" it at a lower temp, say 275. It doesn't work that way. You could soak it at 275 for hours with no ill effect, but bring it over 400 (sometimes higher) for one minute and you've done damage.
 
CrimsonTideShooter said:
I think the lowest temp at which you can anneal (blow a temper) a heat treated blade is 400 degrees, and it goes up from there. If you got a blade that hot, it would be glowing red so that puts it into perspective of just how hot that really is.

Also, a lot of people think that even if you don't reach the annealing threshold you can still damage your knife by "soaking" it at a lower temp, say 275. It doesn't work that way. You could soak it at 275 for hours with no ill effect, but bring it over 400 (sometimes higher) for one minute and you've done damage.
Click to expand...

Thanks for edumacating me on that. I always wondered, but never knew.
 
CrimsonTideShooter said:
I think the lowest temp at which you can anneal (blow a temper) a heat treated blade is 400 degrees, and it goes up from there. If you got a blade that hot, it would be glowing red so that puts it into perspective of just how hot that really is.

Also, a lot of people think that even if you don't reach the annealing threshold you can still damage your knife by "soaking" it at a lower temp, say 275. It doesn't work that way. You could soak it at 275 for hours with no ill effect, but bring it over 400 (sometimes higher) for one minute and you've done damage.
Click to expand...

We talking celsius or fahrenheit? If we are talking F red is not visble in the steel at 400...closer to 800 in pitch black and around 1000ish in daylight. And by "ruin ht" I assume the original poster meant ruin the existing temper....which doesn't take annealing to do (if we are talking about "full anneal" and not tempering). Say a steel is 60rc at about 400degrees and you accidentally heat it to 600...your rc might then be down in the mid 50's. Again...the temps are totally dependent on the steel alloy.
 
ecos said:
We talking celsius or fahrenheit? If we are talking F red is not visble in the steel at 400...closer to 800 in pitch black and around 1000ish in daylight. And by "ruin ht" I assume the original poster meant ruin the existing temper....which doesn't take annealing to do (if we are talking about "full anneal" and not tempering). Say a steel is 60rc at about 400degrees and you accidentally heat it to 600...your rc might then be down in the mid 50's. Again...the temps are totally dependent on the steel alloy.
Click to expand...

I was going by C, sorry. I thought all HT specs were done by C?

ETA: Looks like not all, but yeah that's what I was going by. I guess I can change it to F.
 
Just thought I'd add this, if you are grinding an already heat treated blade (finishing, sharpening, anything) and you get it hot enough to leave a blue looking oxide layer, then you've effectively ruined the temper - at least in that spot.
 
Keep it under about 350 and I don't know of a standard knife steel that will care. Your handle might, epoxies are often not designed for that temp range, nor are many handle materials, but the steel itself won't care.
Since food right out of the oven is rarely over 175 you're pretty safe. The dish might be hotter but not enough to matter since it started cooling the instant it left the oven.

Something to keep in mind, many stainless steels get tempered in two ranges, high or low. Just because the factory temper was at 1000F doesn't mean 450F won't screw things up. I didn't look up exact numbers for a particular steel, but you get the idea. It's not a straight or even one way curve for some of the more complex alloys, it can be a bit of a wave.

Something that might be a concern in terms of heat with the dishwasher is the drying cycle. Depending on your model it may use an exposed heating element and if the blade is near or even directly in line of sight to that element you may expose it to enough heat to be an issue. I'm not sure how hot those elements get so I can't be sure.

There's a secondary issue to consider with hot foods though. If the blades are not stainless you'll see an almost instant patina form when cutting most hot foods. The exact look varies, and as long as you properly clean the knife it is purely visual and is actually helping to prevent more serious corrosion.
 
It depends on the steel but I would say somewhere around 400. Sometimes to anneal a file I'm making a knife from I will toss it in the oven it at 450* for 2 hours twice, and that is for W2.
 
Remyrw said:
Keep it under about 350 and I don't know of a standard knife steel that will care. Your handle might, epoxies are often not designed for that temp range, nor are many handle materials, but the steel itself won't care.
Since food right out of the oven is rarely over 175 you're pretty safe. The dish might be hotter but not enough to matter since it started cooling the instant it left the oven.

Something to keep in mind, many stainless steels get tempered in two ranges, high or low. Just because the factory temper was at 1000F doesn't mean 450F won't screw things up. I didn't look up exact numbers for a particular steel, but you get the idea. It's not a straight or even one way curve for some of the more complex alloys, it can be a bit of a wave.

Something that might be a concern in terms of heat with the dishwasher is the drying cycle. Depending on your model it may use an exposed heating element and if the blade is near or even directly in line of sight to that element you may expose it to enough heat to be an issue. I'm not sure how hot those elements get so I can't be sure.

There's a secondary issue to consider with hot foods though. If the blades are not stainless you'll see an almost instant patina form when cutting most hot foods. The exact look varies, and as long as you properly clean the knife it is purely visual and is actually helping to prevent more serious corrosion.
Click to expand...

I'd never run my knife through the dishwasher anyways. And the knives in question here are stainless, but thanks for the heads up anyways

CrimsonTideShooter said:
Just thought I'd add this, if you are grinding an already heat treated blade (finishing, sharpening, anything) and you get it hot enough to leave a blue looking oxide layer, then you've effectively ruined the temper - at least in that spot.
Click to expand...

Never happened to me (yet)

All my sharpening is by hand, so I doubt I can achieve that kind of heat.
 
cpmsteel said:
Yeah, you have nothing to worry about. Now don't call me lazy but I think I am about to put my Rukus in the dishwasher, because I'm really sick now (hopefully just the flu) and the micarta scales are super dark, from oil. Heck a hard brush and acetone barely does much. I can always re-sharpen my blade.
Click to expand...

I've heard of guys having micarta seperate in the dishwasher. I've not done this myself, but the hot water loosens up the epoxy and the layers will start to spread apart. Not worth the risk, IMO.
 
foxx said:
I've heard of guys having micarta seperate in the dishwasher. I've not done this myself, but the hot water loosens up the epoxy and the layers will start to spread apart. Not worth the risk, IMO.
Click to expand...

I actually forgot to check it. I'm sick. (like I said. I've barely even felt like chcking the forums) anyway I dont think there is epoxy on that knife, if so I can fix it, but I wouldn't put a really nice blade in the dishwasher period.
 
cpmsteel said:
I actually forgot to check it. I'm sick. (like I said. I've barely even felt like chcking the forums) anyway I dont think there is epoxy on that knife, if so I can fix it, but I wouldn't put a really nice blade in the dishwasher period.
Click to expand...

CPMsteel, I'm talking about the epoxy that is holding the fabric layers of the micarta itself. Not, the possible epoxy holding the scales to the tang. Both can be affected by the hot water from the dishwasher. A chunk of micarta in the dishwasher by itself can be damaged.
 
You must log in or register to reply here.
Back
Top