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- May 21, 2006
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I use it mainly for folders.
monty
monty
-
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Damascus heat treat problem.
- Thread starter steelglint
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- Aug 14, 2001
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Monty, while Brownells says it's for "fast quenching" in their online description, they also say it has a "low rate of heat extraction" to prevent deformation and cracking. It's a mid-speed oil. 1095 needs about the fastest quench you can get, and you have about 1 second or less from when it starts quenching to get the temp below 1000F. That's hard enough to do with the physical manipulation of getting it in the tank, then the quenchant better be fast. In your case, I'd say what you are seeing is exactly where the quenchant ran out of efficacy.
Like others have said, you need a faster oil. You might try heating your Tough Quench up towards 130-140F. Around here the usual oil mentioned for 1095 is Park 50. It's almost as fast as water but a little less brutal on the blade and reduces the possibilty of cracking a bit.
Like others have said, you need a faster oil. You might try heating your Tough Quench up towards 130-140F. Around here the usual oil mentioned for 1095 is Park 50. It's almost as fast as water but a little less brutal on the blade and reduces the possibilty of cracking a bit.
- Joined
- Dec 2, 1999
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- 9,910
Ive seen those staight lines before on some of my blades except on the flats. It was from using a surface grinder and not annealing afterwards. No amount of regrinding would take them out either. The surface grinder I used even had a coolant system but apparently there is enough heating from hogging off steel to cause some hard/soft problems that only shows up when etching. They go very deep too. I believe you would see them on the flats too if they would have hardened.
Did you happen to grind the bevels with the blade vertical? Even a couple times could have the same effect.
I use tough quench too for 1084/15n20. Great stuff.
1095 needs a faster quench. I use Parks 50. Its super fast but Ive never cracked a blade yet.
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- May 21, 2006
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Hey Mike,
Thats why I come here. You guys are great. Guess I need to do more home work on the different types of carbon steel.
Thanks, monty
- Joined
- May 21, 2006
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Bruce,
I did do some very light vertical grinding on the flats but the bevels are hollow. The billet looked surface ground when I got it so maybe it got hot then. Thank you for clearing up the mystery. I'll get some Parks before using anymore 1095.
monty
- Joined
- Sep 9, 2003
- Messages
- 2,361
As far as the differential hardening, I am surprised there is this much confusion about this after how much it has been covered here and on a most of the other forums on the net. 1080 has a manganese boost that 1095 doesnt that allows it to harden a little deeper, moving the pearlite nose ever so slightly to the right. 15n20 is basically 1075 with nickel added so it has the same advantage as well as whatever small effect the nickel will add, while this is a shallow hardening mixture it is significantly deeper than the other. 1095 and 1090 are the most shallow hardening of the high carbon 10XX series due to a serious manganese deficiency, and nickel doesnt harden at all, I personally wouldnt have it in any steel that is going to take an edge but that is another can of worms that I will not open.
That shallow hardened zone is quite natural, very repeatable, and exactly as I would expect in oil quenching that steel. I too think it looks terrible on Damascus blades, but that is simply a matter of opinion. To over come it one needs to either increase the hardenability of the steel or increase the quench speed.
Increasing the hardenability of the steel could be as simple, yet discouraging, as going with another steel mix, or adjusting the internal conditions of the steel while austenitizing in order to retard pearlite formation. Some would suggest going lower in austenitizing temp but my exhaustive testing and microscope work has shown me that this will only make the line less distinct by filling the blade with fine pearlite. The standard practice in industry is to bump your soak temp up, not in order to grow grains but to dissolve more carbide and other points at which the pearlite will have a chance to nucleate during the quench. With 1095 this will raise the possible amount of retained austenite, but that line will get a lot closer to the spine, in the nickel it doesnt really matter since it is NEVER going to harden anyway.
Increasing the quench speed is as simple as changing the medium or increasing agitation. You are agitating, arent you? Knifemakers are about the only people in the world that hold steel completely still in a quench and then suffer the consequences of it while holding onto the belief the moving the blade could warp it. Due to vapor blankets holding it still is what causes the warpage! Move that blade as quickly as you can from tip to tang in a stabbing motion through that oil and break up that vapor jacket, while exposing it to fresh cool oil. In the words of Fredrick Douglass agitate, Agitate, AGITATE!. Increasing the rate of agitation can bring the H factor of fast oil on par with still water (around 1 on that scale).
Heat your oil to around 130F and lower its viscosity and thus multiply its heat extraction abilities. Get it too hot and this will quickly drop again so play Goldilocks and keep your oil not too cold, not too hot, but just right. Find a good quenching oil that matches your steel, 1095 will need the fastest you can get, Parks #50 may be quicker for you, check with Darren Ellis.
Now all of these things are good if you want to kill that quench line differentiating the hardened area of the blade from the soft spine, if you want it there do pretty much the opposite of what I have listed. But if you want it, do it for aesthetic reasons, as despite what the hype of the katana mystique has given us, it does not really offer any physical advantages over a fully hardened blade, unless of course you like bent blades.
That shallow hardened zone is quite natural, very repeatable, and exactly as I would expect in oil quenching that steel. I too think it looks terrible on Damascus blades, but that is simply a matter of opinion. To over come it one needs to either increase the hardenability of the steel or increase the quench speed.
Increasing the hardenability of the steel could be as simple, yet discouraging, as going with another steel mix, or adjusting the internal conditions of the steel while austenitizing in order to retard pearlite formation. Some would suggest going lower in austenitizing temp but my exhaustive testing and microscope work has shown me that this will only make the line less distinct by filling the blade with fine pearlite. The standard practice in industry is to bump your soak temp up, not in order to grow grains but to dissolve more carbide and other points at which the pearlite will have a chance to nucleate during the quench. With 1095 this will raise the possible amount of retained austenite, but that line will get a lot closer to the spine, in the nickel it doesnt really matter since it is NEVER going to harden anyway.
Increasing the quench speed is as simple as changing the medium or increasing agitation. You are agitating, arent you? Knifemakers are about the only people in the world that hold steel completely still in a quench and then suffer the consequences of it while holding onto the belief the moving the blade could warp it. Due to vapor blankets holding it still is what causes the warpage! Move that blade as quickly as you can from tip to tang in a stabbing motion through that oil and break up that vapor jacket, while exposing it to fresh cool oil. In the words of Fredrick Douglass agitate, Agitate, AGITATE!. Increasing the rate of agitation can bring the H factor of fast oil on par with still water (around 1 on that scale).
Heat your oil to around 130F and lower its viscosity and thus multiply its heat extraction abilities. Get it too hot and this will quickly drop again so play Goldilocks and keep your oil not too cold, not too hot, but just right. Find a good quenching oil that matches your steel, 1095 will need the fastest you can get, Parks #50 may be quicker for you, check with Darren Ellis.
Now all of these things are good if you want to kill that quench line differentiating the hardened area of the blade from the soft spine, if you want it there do pretty much the opposite of what I have listed. But if you want it, do it for aesthetic reasons, as despite what the hype of the katana mystique has given us, it does not really offer any physical advantages over a fully hardened blade, unless of course you like bent blades.
- Joined
- Sep 9, 2003
- Messages
- 2,361
Now as for those lines
I find them quite fascinating since they appear to be similar, but not quite, to an issue I studied and worked to overcome, but are not the same since they are in the hardened area after the heat treat.
I am very interested in hearing Bruces input about the surface grinding as that falls in line with what I discovered and overcame. When you do very heavy grinding on soft steel you not only cut it but you deform it at the bottom of those deep troughs that coarser abrasives gouge out (40X or coarser). This results in strain energy being put into the steel at the bottom of those lines. Steel with this type of deformation strain is more susceptible to chemical attacks like oxidation or corrosion than the stress free stuff. For some time I suffered with having soft fittings that had a perfect 600X polish come out of the etch with all the 36X scratches right back again. This puzzled me until I studies up and figured all this out. Now I simply heat the part to a recrystallization temperature for a quick stress relieving or low normalization and all that strain is erased so I can say goodbye to those 30X scratches, and the heat treated damascus etches out with a much nicer and more consistent contrast.
While that is all nice and interesting it does not, however, account for this issue. Since it is occurring in a direction opposite of heavy grinding and after all the heat treating should have erased any strain, we have something else going on. The blade can give s several clues, one of which is that the lines are in the hardened area much more boldly than in the soft spine.
Due to the fact that is it pattern welding we can rule out alloy banding or carbide segregation so this leaves the more shallow effects occurring. Lines like this can often form when the FeCl is too warm and the blade is left for too long undisturbed in the etch. The bubbles will tend to follow the same path along the blade to the surface and cut very straight lines into the etched surface, I have had it happened and it is very frustrating.
Any oils greases or other things that could interfere with the etch needs to be completely removed, I have gotten straight lines very similar to this from wiping the blades and leaving streaks that interfered with the etching. A more common problem however is wiping the black oxides off between etches and getting sloppy with it, care must be take to completely remove all oxides, because they tend to have a lick consistency and if you just rub you fingers along the blade wiping them slightly you will leave thicker lines of that slurry which will act quite effectively as a resist.
Last I would look at the anti scale you applied for heat treating. Did you sprinkle it on or brush it somehow? Was the blade heated in a forge or oven? Did the blade rub up against anything while the compound was liquid covering it? If so you could be looking at streaks of decarb where the atmosphere was able to make contact through the compound.
I find them quite fascinating since they appear to be similar, but not quite, to an issue I studied and worked to overcome, but are not the same since they are in the hardened area after the heat treat.
I am very interested in hearing Bruces input about the surface grinding as that falls in line with what I discovered and overcame. When you do very heavy grinding on soft steel you not only cut it but you deform it at the bottom of those deep troughs that coarser abrasives gouge out (40X or coarser). This results in strain energy being put into the steel at the bottom of those lines. Steel with this type of deformation strain is more susceptible to chemical attacks like oxidation or corrosion than the stress free stuff. For some time I suffered with having soft fittings that had a perfect 600X polish come out of the etch with all the 36X scratches right back again. This puzzled me until I studies up and figured all this out. Now I simply heat the part to a recrystallization temperature for a quick stress relieving or low normalization and all that strain is erased so I can say goodbye to those 30X scratches, and the heat treated damascus etches out with a much nicer and more consistent contrast.
While that is all nice and interesting it does not, however, account for this issue. Since it is occurring in a direction opposite of heavy grinding and after all the heat treating should have erased any strain, we have something else going on. The blade can give s several clues, one of which is that the lines are in the hardened area much more boldly than in the soft spine.
Due to the fact that is it pattern welding we can rule out alloy banding or carbide segregation so this leaves the more shallow effects occurring. Lines like this can often form when the FeCl is too warm and the blade is left for too long undisturbed in the etch. The bubbles will tend to follow the same path along the blade to the surface and cut very straight lines into the etched surface, I have had it happened and it is very frustrating.
Any oils greases or other things that could interfere with the etch needs to be completely removed, I have gotten straight lines very similar to this from wiping the blades and leaving streaks that interfered with the etching. A more common problem however is wiping the black oxides off between etches and getting sloppy with it, care must be take to completely remove all oxides, because they tend to have a lick consistency and if you just rub you fingers along the blade wiping them slightly you will leave thicker lines of that slurry which will act quite effectively as a resist.
Last I would look at the anti scale you applied for heat treating. Did you sprinkle it on or brush it somehow? Was the blade heated in a forge or oven? Did the blade rub up against anything while the compound was liquid covering it? If so you could be looking at streaks of decarb where the atmosphere was able to make contact through the compound.
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- May 21, 2006
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Kevin,
Thanks for weighing in. I'm going to print all the responses to this thread for future reference. As to your questions, no...I didn't agitate...(but I will, still learning). Mike and Bruce said the same thing about the oil. Get something faster. The pbc coating was sprinkled on heavy with a shaker. I had complete coverage and was carefull when placing them in the holders in the oven. I'm starting to think it might have been the FC that caused the lines. I checked the smaller blade several times during the etch, the larger one only once and it has far more lines. I'll set up an aeorator as per Chuck's post. Again, I thank all you guys for your responses.
Monty
Thanks for weighing in. I'm going to print all the responses to this thread for future reference. As to your questions, no...I didn't agitate...(but I will, still learning). Mike and Bruce said the same thing about the oil. Get something faster. The pbc coating was sprinkled on heavy with a shaker. I had complete coverage and was carefull when placing them in the holders in the oven. I'm starting to think it might have been the FC that caused the lines. I checked the smaller blade several times during the etch, the larger one only once and it has far more lines. I'll set up an aeorator as per Chuck's post. Again, I thank all you guys for your responses.
Monty
- Joined
- Oct 3, 2002
- Messages
- 12,297
Kevin, I too have seen the grinding lines after etching and came to the same conclusion. Can be very frustrating.
The lines in those blades are formed during etching. You must clean all the black oxides off every 5 minutes or so.
I also find that leaving my blades a little thicker before HT and grinding to finished thickness after HT eliminates a lot of potential problems. No need for an anti-scale coating when doing it this way.
The lines in those blades are formed during etching. You must clean all the black oxides off every 5 minutes or so.
I also find that leaving my blades a little thicker before HT and grinding to finished thickness after HT eliminates a lot of potential problems. No need for an anti-scale coating when doing it this way.
- Joined
- May 21, 2006
- Messages
- 96
Okay guys, I reground the larger blade enough to remove the lines and the previous etch. Then etched with agitaition for ten minutes. I got a very deep etch and no lines. Appreciate all the help.
Monty
Monty
- Joined
- Apr 14, 2006
- Messages
- 3,816
I recommend parks 50. I used peanut oil for many years but the parks 50 gives more consistent results. I also have an oil called fast quench from McMaster Carr. It works really well but smells like used motor oil. The fast quench is a 9-11 second while the parks is a 7-9 second. But as mentioned you need to get that blade into the quench faster than 6 seconds, more like 1-2. I have had the streaking problem on all carbon steels esp. damascus and on 5160. Wayne Goddard suggested the aerator and it has cured the problem. My etch process is clean well, hang point down in tank with bubbles for 1 minute, remove and rub down well with 1500-2000 grit w/d paper. repeat 3 times. for a deeper etch leave in the tank for 2-3 minutes each cycle.
Chuck
Chuck