Damascus heat treat problem.

S

steelglint

Joined
May 21, 2006
Messages
96
Hey guys,
I've been using a bit of commercial Damascus for stock removal knives the last few months, and run into somthing I dont understand. I heat treated 5 blades yesterday- pbc coated at 700, then up to 1475 for 5 min. then quenched spine down, point first in Brownells fast q. 2 draws at 375 for 1 hr.
1 blade was old Parker Edwards scrap -not sure of the makeup- .110 thick.
2 blades were 1080 and 15n20 at .125 thick. The last 2 are 1095 and pure nickle and are .185. After the ht, I noticed that the thicker blades looked like they were differentally hardend- you could see a definite wavey line. I tested them as quenched and found that on the tang, just behind where the guard will be, the thicker blades were 49rc. Cant test the edge because of no flat area but a new file wont touch it so I know its hard. The 2 .125 blades tested 62rc. So after getting the final grinding and sanding done, I etched them all pretty deep and then buffed them. The 3 thinner blades turned out as expected but on the thicker ones I got a bunch of-lines?- running paralell to the edge but only in the hardend part of the blade!!!? Anybody no what causes this? Is it common with differental hardening? I,m pretty new to h. treating carbon steels so any help would be much appreciated.

Thanks, Monty


Heres some pics.


steejpics001.jpg

steejpics004.jpg

steejpics007.jpg
 
Howdy,
You're getting a soft back and hard edge because the oil you're using is too slow for the steels you're using. You could get a faster oil, or raise the hardening temp some. I'd go up to 1500.
As for the lines along the edge, I don't know. That's pretty bizarre. Maybe it's carbide segregation.
Nice looking blades, BTW.

Phillip
 
lengthen your soak time to 10 minutes. I soak mine at 1490 for 10 minutes and they do just what I want. I don't know anything about Brownells fast q. but it should be just fine for 1080 &15n20 unless its super slow oil.
Those lines are a mystery to me, never had anything like that come about.

Bill
 
Thanks Phillip, I'll bump it up to 1500 on the next batch. Those lines have me stumped.
Theres no delamanations but you can feel them with your finger nail....wierd.


monty
 
Phillip Patton said:
Howdy,
You're getting a soft back and hard edge because the oil you're using is too slow for the steels you're using. You could get a faster oil, or raise the hardening temp some. I'd go up to 1500.
As for the lines along the edge, I don't know. That's pretty bizarre. Maybe it's carbide segregation.
Nice looking blades, BTW.

Phillip
Click to expand...

Er... I don't see how this is a problem. Ok, it may be as long as one doesn't know why or how it happens, but once you can control the process, is actually a very desirable characteristic in a knife.
 
Alarion said:
Er... I don't see how this is a problem. Ok, it may be as long as one doesn't know why or how it happens, but once you can control the process, is actually a very desirable characteristic in a knife.
Click to expand...

It's not desirable to everyone.
Personally, I don't care for the look of an edge quench on a damascus knife.
 
Phillip Patton said:
It's not desirable to everyone.
Personally, I don't care for the look of an edge quench on a damascus knife.
Click to expand...

Yes. This is true.
Even so, while it can be disappointing from an aesthetical point of view, it is an advantage from a mechanical perspective as it is on a monosteel.
I wonder if there is a method to make the damascus stand out while not doing so to the temperline as well. :confused:
 
Foreword: sorry for the double post. I was typing with my cat on my lap, and didn't see her pressing various keys while I was typing... :p:D
No, really, I'm serious, it's true.

steelglint said:
So pretty much more heat in the steel. Thanks guys.


Monty
Click to expand...

No. That's plain wrong. Heat the steel too much and you'll have grain growth that will make your blade fragile.
What you see there happened for one of two reasons:

1) You plunged your blade in the oil partially. You hesitated, or didn't submerge it thoroughly, or something like that, and you got a temperline.

2) You heated your blade, checked for non-magnetic on the edge, but the edge got to critical temp sooner than the spine, due to different thickness, and the edge hardened while the spine didn't.
Soak the blade longer at the same temp, giving the spine as well time to get to critical. Or, if you used a gas forge, there is some strong gradient in temperature in the forge you must deal with.
Try to keep the blade spine down in the fire, if using a coal forge, and then flat down in the final minutes of heating, or move and rotate it in a gas forge.
Don't go much over non-magnetic, or you'll just improve grain growth. Mete or Kevin could be more specific on this subject.
 
Monty,
How are you heat treating? Since you mentioned specific temperatures, I figured you were using an oven or something. Is that true?
 
Alarion said:
Foreword: sorry for the double post. I was typing with my cat on my lap, and didn't see her pressing various keys while I was typing... :p:D
No, really, I'm serious, it's true.



No. That's plain wrong. Heat the steel too much and you'll have grain growth that will make your blade fragile.
What you see there happened for one of two reasons:

1) You plunged your blade in the oil partially. You hesitated, or didn't submerge it thoroughly, or something like that, and you got a temperline.

2) You heated your blade, checked for non-magnetic on the edge, but the edge got to critical temp sooner than the spine, due to different thickness, and the edge hardened while the spine didn't.
Soak the blade longer at the same temp, giving the spine as well time to get to critical. Or, if you used a gas forge, there is some strong gradient in temperature in the forge you must deal with.
Try to keep the blade spine down in the fire, if using a coal forge, and then flat down in the final minutes of heating, or move and rotate it in a gas forge.
Don't go much over non-magnetic, or you'll just improve grain growth. Mete or Kevin could be more specific on this subject.
Click to expand...



Evidently, you missunderstood my statement. I ment more heat as in let the blade soak longer and be heated throughout. I heated the blades in a controlled Paragon oven. The only thing that was done different on this batch was quenching spine down. The time from oven to oil was maybe 6 sec. Every thing went in the oil including the end of the tongs. I was under the impression to have a temper line you had to either edge quench or clay the back of the blade. I did neither. I dont have a problem with the temper line, I actually like it. But having it show up by accident bugs me and the paralell lines mess up the pattern in the steel.


monty
 
Hey Fitzo,
Yes, thats what I'm using.


Phillip, I'm using a paragon ht 14d oven.

Again thanks guys.

monty
 
The speed of your quenchant is the cause of your "quench Line". I would say that you hung the blade tip down in the FC correct?? I was getting these lines also. It was caused by etched material sliding down the blade during the etch. I use a cheap aquarium air pump with a aerator stone on the end. Put the hose into the FC with the stone on the end. Whenever you etch turn on the pump. This will do 2 things, it will keep the blade cleaner and it will speed up the etch. Give it a try.

Chuck
 
steelglint said:
Evidently, you missunderstood my statement. I ment more heat as in let the blade soak longer and be heated throughout. I heated the blades in a controlled Paragon oven. The only thing that was done different on this batch was quenching spine down. The time from oven to oil was maybe 6 sec. Every thing went in the oil including the end of the tongs. I was under the impression to have a temper line you had to either edge quench or clay the back of the blade. I did neither. I dont have a problem with the temper line, I actually like it. But having it show up by accident bugs me and the paralell lines mess up the pattern in the steel.


monty
Click to expand...

Weird... I understand perfectly why it bugs you...
6 seconds are a lot of time, but the worst it could do is get a cold edge and hot spine, and so soft edge and hard spine, kind of a reversed temperline, while yours is a proper temperline...
Bugs me as well... :confused:
 
Chuck,
Thank you for the info. and yes point down in the FC. Man, I never would have thought of that. Does it it only effect certain steels? I'll try the pump Idea. The other guys mentioned the oil too. Is tough quench too fast or slow? What do you all recommend?
Sorry for all the questions but like I said, this working with carbon stuff is still new to me.


monty
 
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