Testing W2 Hardness Quenched with Parks 50 and 9% Brine Solution.

[ndp_2010]

Dear jeff, couple of Q's did you test temperatures with your thermocouple when the metal plates were in the kiln? as shown in post 48 http://www.bladeforums.com/forums/s...-and-9-Brine-Solution?p=16566705#post16566705


These findings are very interesting and almost identical to what I found in my paragon km24D, showing a temp variation of ~50 degrees C (120F) from the probe, till about 1/2 way down the oven, then a slightly less variation (drilled a few holes in mine as well ).
Apparently at such high temperatures, the air inside is so thin that there is next to no air movement, and thats why the temp inside doesnt equalise. Even after 3 hours soaking my oven had the same temp variations! Also tried fire bricks etc. but still the same issue.
Looks like the addition of elements in the back of the kiln (and lack of elements in the door) really promotes an uneven heating environment thats unacceptable IMO for knives. As far as im aware paragon modified their latest oven to have no elements in the back. Its great to see you getting much more even heats in the oven by modifying it and is something that I will need to do. Untill then will have to set my oven 50C lower and use the back half for heat treating.

 

[Jeff the Millwright]

Dear jeff, couple of Q's did you test temperatures with your thermocouple when the metal plates were in the kiln? as shown in post 48 http://www.bladeforums.com/forums/s...-and-9-Brine-Solution?p=16566705#post16566705


These findings are very interesting and almost identical to what I found in my paragon km24D, showing a temp variation of ~50 degrees C (120F) from the probe, till about 1/2 way down the oven, then a slightly less variation (drilled a few holes in mine as well ).
Apparently at such high temperatures, the air inside is so thin that there is next to no air movement, and thats why the temp inside doesnt equalise. Even after 3 hours soaking my oven had the same temp variations! Also tried fire bricks etc. but still the same issue.
Looks like the addition of elements in the back of the kiln (and lack of elements in the door) really promotes an uneven heating environment thats unacceptable IMO for knives. As far as im aware paragon modified their latest oven to have no elements in the back. Its great to see you getting much more even heats in the oven by modifying it and is something that I will need to do. Untill then will have to set my oven 50C lower and use the back half for heat treating.

No ndp_2010 I did not have metal plates in my oven when I was testing with my thermocouple. The only reason I had them in there for the other tests was that I was using the tempil stick at that point and I didn’t want the mess from them melting on the bottom of my oven I just had them in there to protect my oven.

And thank you for posting because it is validating to see that you are getting the same problem with your Paragon oven and that they omitted the rear element in their latest ovens.

 

[duurza]

You do have an interesting argument duuraz I have to concede that logically it does make sense that since the conductivity of the metal is much greater than the amount of heat that can be radiated from the elements it does make sense that the pipe would even out the heat but I just don’t see that happening in practice.

Because think about this. If this were true then you would not need a pipe at all because your knife being metal would conduct the heat inside itself faster than oven heat could be applied to it through radiation from the element. So if your argument were true the knife would be doing the exact same thing for itself that the pipe would do.

And that isn’t the case because one thing that made me think that my oven wasn’t evenly heated was when I made a knife it was obviously hotter the farther in it was because it was brighter and if your logic was true it would have been red consistently along its length because it would have been able to conduct the heat internally faster than the element could radiate heat to it unevenly.

I fixed my problem by moving my element so there is no point in me doing a test with a pipe because now I have even heat in my furnace so the results would be meaningless. But I would like to see someone try that just out of curiosity because I don’t think it would do much to even out the heat.

As a disclaimer to not ruffle any feathers this is just my opinion but all my experience tells me that putting a pipe in a in a furnace will not even out the heat inside the pipe but if someone does that experiment I would love to see it because I am curious.

You are right. That is where the 5% error comes into play . Direct radiation will still ever so slightly cause the exposed surface to be at a higher temperature compared to the core because in reality, there needs to be a thermal gradient between the surface and the core in order for there to be a movement of heat (logical).

The tube though would definitely help even out the temperature because it would take the (assumed wild) fluctuations in radiation at the surface and evenly distributed it within itself. This uniform increase in temperature is then radiated to the object inside.

I'm not trying to tear apart any of your tests; on the contrary, I find it very interesting that you are going through all of this to make a knife. I studied engineering so I find all of this very interesting.

Last note: you are also correct in saying that the pipe would not totally even out the temperature within. Radiation reflected from the rear walls would definitely strike the object inside. What you would need is a sealed steel box!

 

[ndp_2010]

Thanks for the reply. It would be interesting to see if there was any improvement with adding metal plates, theoretically they might help distribute heat a little more evenly since this would be through conduction rather than air convection which is not effective at this temp, although I doubt it would completely fix the issue.
I might have to try this a a quick fix untill I can modify my current oven.

 

[Jeff the Millwright]

I'm not trying to tear apart any of your tests; on the contrary, I find it very interesting that you are going through all of this to make a knife. I studied engineering so I find all of this very interesting.

No problem duurza; I did not take your opinion as trying to tear apart my tests and found your points interesting. And I am going through all this to make a knife because I actually enjoy the discovery process and I find it a challenge to make the best knife I can. I don’t have to worry about trying to make money from knife making so I can take my time and really do it right and heat treating is the most important aspect in a knive’s performance so I really want to get the process down properly.

Besides I am retiring in a year and being in the construction trades I don’t have to work all the time so when I don’t work as a millwright I am tinkering around in my shop but there I get to do what I want to do which makes it a lot more gratifying and fun.

My 5 gallons of Parks 50 arrived today so whenever I get some time off again I can actually make a knife.

 

[Jeff the Millwright]

Thanks for the reply. It would be interesting to see if there was any improvement with adding metal plates, theoretically they might help distribute heat a little more evenly since this would be through conduction rather than air convection which is not effective at this temp, although I doubt it would completely fix the issue.
I might have to try this a a quick fix untill I can modify my current oven.

Yes just out of curiosity ndp_2010 I would also be interested about any results of someone adding metal plates or even a pipe or a sealed steel box in an oven to see if it distributed the heat more evenly. My oven is within 10°F pretty much throughout its length now with my modification so it really wouldn’t mean anything if I did a test but if anyone else does I would love to see the results posted also.

 

[ndp_2010]

Yes just out of curiosity ndp_2010 I would also be interested about any results of someone adding metal plates or even a pipe or a sealed steel box in an oven to see if it distributed the heat more evenly. My oven is within 10°F pretty much throughout its length now with my modification so it really wouldn’t mean anything if I did a test but if anyone else does I would love to see the results posted also.

Thats excellent result and I think is fine for normal use. I will get another probe and test my oven again with a metal plate. But eventually would like to modify my oven as well like you have done.

 

[Jeff the Millwright]

"Superior heat distribution

To improve the heat distribution in the Double Barrel 18T, we have added heating elements in the top and removed the heat from the back. The furnace now heats from three directions--the two sidewalls and the top for uniform heating."

Someone mentioned that Paragon ovens no longer have an element in the back to try to get a more even heat so I went to their website and found this which verifies it is true and that they eliminated the rear element because it caused uneven heating. Personally if I had it to do over again unless there are other things I don't know about the Paragon ovens I would definitely recommend that over the Evenheat oven I have that came with a rear heating element because of the uneven heating it caused.

 

[whiteyluvsrum]

Someone mentioned that Paragon ovens no longer have an element in the back to try to get a more even heat so I went to their website and found this which verifies it is true and that they eliminated the rear element because it caused uneven heating. Personally if I had it to do over again unless there are other things I don't know about the Paragon ovens I would definitely recommend that over the Evenheat oven I have that came with a rear heating element because of the uneven heating it caused.

All the current Paragon knife making kilns don't have rear elements anymore, its been like that for at least a year or two. They are in the process of making an upgrade kit for there older models as well.

 

[ndp_2010]

All the current Paragon knife making kilns don't have rear elements anymore, its been like that for at least a year or two. They are in the process of making an upgrade kit for there older models as well.

yes they are which is a relief for those who have the older model (myself included). the disturbing thing about all these ovens is that they were never properly tested, and there was clearly no thought going into the oven layout, which is clear by the 120F difference between the readout and 3/4 of the oven. >.< im sure overheating is not a huge issue for pottery or glass etc, but 10's of degrees for steel is very worrying.
I was very surprised that I had not come across a detailed outline of the problem previous to this post - im sure quite a few people knew about it

 

[noseoil]

I know it's flogging a dead horse, but what about making a simple "tube" for the oven which is double-wall construction? Perhaps a heavy plate on the bottom, which is the foot or base, an "outer" tube of larger diameter & then an "inner" tube to set the blade in for the HT & cycling. It could be fairly simple to make but might help a lot in actual use. I know it's like adding legs to the snake, but it might make for a much better stability in the temperature cycle.....

P.S. Jeff, you're as tenacious as a bulldog with this one, but I know it will make for some wonderful blades when you're done tinkering.

 

[Jeff the Millwright]

All the current Paragon knife making kilns don't have rear elements anymore, its been like that for at least a year or two. They are in the process of making an upgrade kit for there older models as well.

Thanks for the info whiteluvsrum but I really wish I knew that before I bought my Evenheat oven because although I have been able to modify it to get even heat by removing the back element who knows how long my element will last now that I have tampered with it and it doesn’t fit together quite as good as it originally did since I disassembled and reassembled it.

 

[Jeff the Millwright]

yes they are which is a relief for those who have the older model (myself included). the disturbing thing about all these ovens is that they were never properly tested, and there was clearly no thought going into the oven layout, which is clear by the 120F difference between the readout and 3/4 of the oven. >.< im sure overheating is not a huge issue for pottery or glass etc, but 10's of degrees for steel is very worrying.
I was very surprised that I had not come across a detailed outline of the problem previous to this post - im sure quite a few people knew about it

Yes ndp_2010 I agree it is frustrating this wasn’t made common knowledge sooner and I also find it amazing that Evenheat continues to sell these poorly designed ovens. They must know that Paragon has corrected their design so you would think they would follow suit because it is a pretty minor upgrade to correct a bad problem.

 

[Jeff the Millwright]

I know it's flogging a dead horse, but what about making a simple "tube" for the oven which is double-wall construction? Perhaps a heavy plate on the bottom, which is the foot or base, an "outer" tube of larger diameter & then an "inner" tube to set the blade in for the HT & cycling. It could be fairly simple to make but might help a lot in actual use. I know it's like adding legs to the snake, but it might make for a much better stability in the temperature cycle.....

P.S. Jeff, you're as tenacious as a bulldog with this one, but I know it will make for some wonderful blades when you're done tinkering.

I wish someone would actually test that dead horse proposed solution noseoil because I’m curious myself whether it would work but I have doubts about it so it would be interesting to see an actual test. Unfortunately I can’t do it because my oven is pretty evenly heated now since I tinkered with it.

But I can’t see the tube system working. The theory is that a tube will conduct heat down the length of the tube generating an even heat inside the tube but I just can’t see that happening. Heat seeks equilibrium and heat will travel from a higher place to a cooler place until they are equal in temperature. So it makes sense in theory that a tube would carry the heat down its length until the whole thing was evenly heated but I think what people fail to take into consideration is that as the heat travels down the tube from the hot end of the oven to the cooler end heat would be dissipated from the tube surface back into the oven because it would be hotter than the cooler part of the front of the oven. So my supposition is that the tube would just mimic the temperature of the oven pretty much.

Unfortunately I have been working the last few weeks so I haven’t been able to do any blade making but yes noseoil I am getting to the point where I should be able to make some pretty good blades. Now that I know my heat is even in my oven I’m going to do some test samples to figure out exactly what temperature gives me my maximum hardness with my W-2.

From my tempilstick tests I think I am within about 5° from what my readout on my oven tells me if the stick is pretty accurate but of course there is no way to know that so I think I will try three samples right under the sensor at 1450°F and 1460°F and 1470°F. Hopefully one of these will give me a hardness of 68 and then I am off to the races to actually make a knife. If all goes well I will get that done tomorrow if I don’t get called for work.

Before I make my next knife I am also going to make a platen out of some 2 inch 1095 that I have because the one I have now is just mild steel and it’s starting to get a little wear in it. Obviously I want it as hard as possible and I’m not sure if I will just quench it and not temper it for maximum hardness or if it might crack if I don’t. Maybe I will temperate to about 200°F? Any suggestions?

 

[Willie71]

A stress relief temper is a good idea. I used O1 and used 300f.

 

[Jeff the Millwright]

A stress relief temper is a good idea. I used O1 and used 300f.

I think you are right Willie because it’s better to lose a couple of points of hardness than have the thing crack on me. Interesting you use O1 because I would think 1095 would hold up almost as well.

Here’s a photo of it before I have done the heat treating. I’m holding my new platen in front of the old thick mild steel one I have been using. Because my 1095 is only about .175” I am just going to attach it to my old one with some machine screws for support. I countersunk my holes front and back and centered them so I can flip it vertically and horizontally as it wears as I only seem to use the top half so I should get four uses out of it.

I did some tests today also with Aust. temps for W-2 which are kind of interesting so I will post them after dinner.

 

[Willie71]

I had 1/4" O1 on hand. My 1095 is 3/32". I have W2 in 1/4", but I like it too much for blades, and I don't use O1 much anymore,

 

[Jeff the Millwright]

Now that I have my oven heating pretty much evenly throughout its length I did some tests to try to determine the best austenitizing temperature for my oven with W-2.

Since most people feel the best temp is around 1460°F initially I tried 1450, 1460 in 1470. I had three pieces that I had put a thin watered-down skim-coat of furnace cement on to act as a scale inhibitor as recommended by Stacy because I suspected scale was giving me wide variations in readings on some of my earlier test pieces.

As you can see from my readings 1450°F gave me the best results but not as high as I had hoped for so it seemed my ideal temperature was lower. I also put in a piece of 1450°F Tempilstick and it was totally melted at 1450°F so I assumed my furnace was hotter than the readout temperature in conjunction with the fact 1450°F also seemed too hot for an austentizing temp and most people were using 1460°F.

So my second test I reused the same pieces to save material and time and did not coat them with any skim coat or furnace cement. As you can see 1430°F and 1440°F gave much better results even with just the scale removed. I also did a tempilstick melt test on this series and it was melted at about 1420°F so if the stick is accurate which there is no way of knowing my oven is about 30°F hotter than the readings and the fact my ideal austentizing temperature seems to be about 1435°F seems to verify this fact pretty closely since most people are using 1460°F for theirs.

I didn’t include these figures so as not to confuse myself but this second set of tests where I reused the same samples from the first tests without recoating them with a skim layer of furnace cement gave variances of readings up to 15 points so that does verify that it is scale that was causing such disparities in the past with my tests. I may do some tests later perhaps with some commercial scale inhibitors because I find it’s hard to get the skim coat of furnace cement even and with it I still did get a couple of points variance in my first tests but that’s markedly better than without it.

So now that I know my range I’m going to do tests every 5°F starting at 1430°F up to 1450°F with pieces that have a skim coat of furnace cement and I will be removing a layer to really know what my hardness is at and below the surface.

What is surprising is how quickly the hardness falls off outside the 1430°F to 1450°F ranges. It seems pretty obvious even at this preliminary stage that this steel only has a 20°F range before hardness is dramatically affected so it just goes to show how important a very evenly heated oven is for knife making. And I hate to beat a dead horse but that’s why I think it’s so sad that Evenheat sells heat treating ovens that heat so unevenly because doing a sizeable knife in one of those ovens would definitely fall off the extreme ranges beyond the 20°F mark.

 

[Willie71]

Now that I have my oven heating pretty much evenly throughout its length I did some tests to try to determine the best austenitizing temperature for my oven with W-2.

Since most people feel the best temp is around 1460°F initially I tried 1450, 1460 in 1470. I had three pieces that I had put a thin watered-down skim-coat of furnace cement on to act as a scale inhibitor as recommended by Stacy because I suspected scale was giving me wide variations in readings on some of my earlier test pieces.

As you can see from my readings 1450°F gave me the best results but not as high as I had hoped for so it seemed my ideal temperature was lower. I also put in a piece of 1450°F Tempilstick and it was totally melted at 1450°F so I assumed my furnace was hotter than the readout temperature in conjunction with the fact 1450°F also seemed too hot for an austentizing temp and most people were using 1460°F.

So my second test I reused the same pieces to save material and time and did not coat them with any skim coat or furnace cement. As you can see 1430°F and 1440°F gave much better results even with just the scale removed. I also did a tempilstick melt test on this series and it was melted at about 1420°F so if the stick is accurate which there is no way of knowing my oven is about 30°F hotter than the readings and the fact my ideal austentizing temperature seems to be about 1435°F seems to verify this fact pretty closely since most people are using 1460°F for theirs.

I didn’t include these figures so as not to confuse myself but this second set of tests where I reused the same samples from the first tests without recoating them with a skim layer of furnace cement gave variances of readings up to 15 points so that does verify that it is scale that was causing such disparities in the past with my tests. I may do some tests later perhaps with some commercial scale inhibitors because I find it’s hard to get the skim coat of furnace cement even and with it I still did get a couple of points variance in my first tests but that’s markedly better than without it.

So now that I know my range I’m going to do tests every 5°F starting at 1430°F up to 1450°F with pieces that have a skim coat of furnace cement and I will be removing a layer to really know what my hardness is are.

What is surprising is how quickly the hardness falls off outside the 1430°F to 1450°F ranges. It seems pretty obvious even at this preliminary stage that this steel only has a 20°F range before hardness is dramatically affected so it just goes to show how important a very evenly heated oven is for knife making. And I hate to beat a dead horse but that’s why I think it’s so sad that Evenheat sells heat treating ovens that heat so unevenly because doing a sizeable knife in one of those ovens would definitely fall off the extreme ranges beyond the 20°F mark.

I had similar results. +/- 10f from ideal sees less consistency, even if you get a few full hardness readings. It's really picky about austentizing temp.

 

[kuraki]

how did you quench these?