Triple quench secrets to be revealed?(or not)

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concerning home freezing in a refrigerator :)
I think it's the wait time that will raze up the Rockwell
not the cold from the home freezer,,
not saying it won't help to a small existent,
but knowing I can straighten out warps just as soon as I can handle the blade from the hardening quench
this tells me it does with time get harder.

sometime I'd like to see just what a piece will Rockwell at say testing the same piece at
different times after the hardening quench,
say every 15 or 30 min's. to see just what it's doing.

you say time is a factor in the NL why not time at room temp after the treatments.
I say this is the biggest factor not the home cold at about 28+ deg.
some of the manufactures say -120 is needed so that means Dry ice
round -90 would not be at the min
coldness needed to do any good.
I think to get accuracy in testing you need steel that has stabilized completely.
just 2 more cent :)
 
Roger , if you have the equipment for -320F and would like to do it OK. But remember that a steel with only .60% carbon would not be expected to have any significant amount of retained austenite so the benefits would not be significant. Also something like a one point change on the rockwell C scale is not significant .Specs for hardness should always be a range, 2-3 points for a blade.
 
mete, are you telling me 5160 has only 0.6% carbon?? I had no idea.

More to the essence of your recent posting, I am not promoting deep freeze for this test. I was only responding to an observation by another. This HT will be done to your specs. if I am the one to do it. That I promise and that is the way I prefer it be done.

RL
 
What I seek to know is...

1- In identical forged 5160 steels, does a knife benefit from multiple quenches?

2- if there is a noticable benefit from the use of the multiple quench, from where is it comming?. and how can I help this along?


although it might be interesting to later on see how freezing a knife effects it,,,I , and most people on earth, have little ability to freeze a knife down to -320
 
DaQo, I believe cryo is good for any high carbon steel. You can use the dry ice method as I did before I went broke by buying a dewar. Keep the steel in the dry ice for as long as the ice remains. If you can keep it going for two days by putting the container in the freezer - do it.


RL
 
Bill,

If I read your post correctly...


The remaining piece will get two more anealing heats then be ground to the thickness of the other three. Then I will harden only half of it using the same procedure as I would if I were making a knife. The sample will then be polished and etched
Click to expand...

This 4th piece of steel will have been heat treated as you and Ed would normally treat a blade? If so, testing it compared to the other three samples will cover any questions that I had. Thanks for going to all the trouble with your donation to the cause! I know how busy you are since you went full time. More like full time and a half.;)

Rick
 
yes, I agree, the ability of freezing a knife might be interesting to note, after I begin to understand the 3 Heat treatings that I do now, and their full effect on my blades.

However I also think that tossing a freeze into a knife test could mess up the results.

Now I do use my freezer when I take my blades in from the last heat treating, and before I start to temper them,,,however this is based on only 2 things. First a small comment Ed Fowler made in the b ook Knife Talk , where he says such a thing "Might not help but will not harm" a knife.

and 2nd, it's a handy place to keep the blades out of sight from others, (kids)

The dry-ice idea is interesting,,,Im not sure at all where such could be had in my area. I might look into that, however the freezer is already here so I might just......
 
The results of the 5160 single quench test are in.

Here is how it was heat treated:

Ramp oven to 1475 and let stabilize.

Place test piece in oven.

Check to see when test piece color consistantly matches that of a reference piece of steel already in oven.

Soak 5 minutes.

Quench to oil temp. in 134 F. vegetable oil.

Temper immediately at 400 F. for 1 hour.

Still air cool to room temp.

Grind scale and decaboration.

Rockwell
--------------------------

Three samples were taken across the surface of the test piece:
(test results rounded to the nearest 1/2 point)

58 HRC
58
58
---------------------------

I promised the guys over on the 440C triple oil quench thread I would do their triple quench tomorrow. I will do my best to do the 5160 triple quench Sunday.

I haven't even looked at a 5160 data sheet yet because I wanted to remain as blind as I could while doing this. I am anxious now to look at one.

Bill, I didn't get one that you had heat treated. I got three equal pieces, all un-hardened. Thank you for sending them. I just went back on the thread and it doesn't look like I told you I received them. I am sorry. I have been in several different directions lately.

Roger
 
Roger,

I haven't sent the forth piece yet. I am busting ass triing to get the knives done for the show and haven't taken the time to do it yet. It might be after the show before I get it done and sent off to you. How much did you have to take off the other pieces after heat treating.
 
Bill, almost nothing. Shallow decarb.. The triple quench should be a different story. Plan to do it tomorrow (09/07). I am working on the 440C guys triple quench right now. I got steel for both testings at the same time and am trying to be fair by alternating one day for this one and one day for that one.

Thanks for clearing up the other test piece. I was looking under furniture wondering if I had lost it. No problem on that one. Whenever.

Roger
 
The results of the 5160 triple quench tests are in.

Here is how it was heat treated:

Ramp oven to 1475 and let stabilize.

Place test piece in oven.

Check to see when test piece color consistantly matches that of a reference piece of steel already in oven.

When it does, quench immediately to oil temp. (I watched the clock and say that from the time the oven recovered to 1475 F. to the time steel became consistant in color and that of the reference piece about 1 1/2 minute or a little longer elapsed.)

Temper immediately at 400 F. for 1 hour.

Still air cool to room temp.

Repeat all above for a total of three quenches and three tempers

Grind scale and decaboration.

Rockwell test
--------------------------

Oven temperatures after the test piece was placed in oven and oven door closed:

autenitizing #1: 1399 F.
autenitizing #2: 1367 F.
autenitizing #3: 1385 F. (I timed the recovery time for this one: 1385 F. to 1475 F. = 2 min. 12 sec.)

I did not visually check for critical until after the oven recovered to 1475 F..

oil temperatures for quench:

quench #1: 134 F.
quench #2: 136 F.
quench #3: 136 F.
---------------------------
Three samples were taken across the surface of the test piece:
(test results rounded to the nearest 1/2 point)

58 HRc
58
58
---------------------------

Test pieces of 5160 for both single and triple quench tests are 2 1/2 X 1 /14 X 5/32 inch

Roger
 
I think this is Very useful information!

I believe that it's one key part of the overall characteristics of a blade made with 5160.

I will be very interested in any other suggestions for testable methods of Heat treating 5160 that could build on the results we see so far.
 
I did not want to post this until after both of those tests were complete and posted but ... Bill sent me three pieces. The first one I tested, and did not post, was heat treated more the way I have been doing my steels. I did a single quench and I did it precisely as I did the single quench piece previuosly posted with this one exception: I placed the test piece in the COLD oven, ramped to 1475 F. and upon the oven attaining 1475 F. soaked for 5 minutes.

Here is how it tested:

58 HRc
57.5
58

It is 58 HRc

Then, I put the piece in deep cryo for 16 hours, still air warmed to room temperature and tested again. Here are those results:

58 HRc
58.5
58

It remains 58 HRc

RL
 
A wall? I wouldn't say that. Look at the consistency in temperatures used. That was part of the whole purpose. It was a test of quenching not hardness limits. I tend to agree with you to the extent that for this relatively low carbon steel and austenitizing at 1475 F. we may have approached its upper hardness limit. I believe, and may be wrong, 5160 is often austenitized in the range of 1550 F. but I have not seen data sheets with aim hardness figures yet.

RL
 
concerning home freezing in a refrigerator
I think it's the wait time that will raze up the Rockwell
Click to expand...

Yes. Cold is needed as you mentioned, but time is critical to that formula to work at the lower temps. :cool:
 
Thanks rlinger (Roger)!

You published test results about single and triple quenched blades (5160).


Let's suppose that "only" 1000 knife makers (the total number of all makers must be bigger) can and will use your test results to do more efficient work. Then in production of let's say 300 blades per each maker will add up to 300000 blades, the saved time is significant.

Also you did give an information about
the problem of freezing. Must be invaluable for example to the makers figuring out to buy or not to buy a freezing tank.


DaQo'tah Forge says somethnig I do not understand, hitting the wall at 58?
With 5160 we can get even about 62 HRC but then the tempering must be almost non existent and the steel is brittle. In this test we used "a given" tempering temperature 400 F and then the steel can not be very hard.

On the other hand this question is interesting to think ahead because HRC is only one factor as to "goodness" of a blade, even it is very important to wear resistance or edge holding in other words.
By the way, for this reason I did speak about "user level tests" as rope cutting earlier.



pig
 
I acknowledge Mete and thank him here and now for directing me in the heat treat specifications I followed. It is his procedure outlined to me that I followed to my best ability.

As for deep freezing the 5160, I believe Mete had posted here that he did not believe a cryo treatment would increase the hardness of this particular steel because of its' relative low carbon content. My testing, at least to my satisfaction, shows him to be correct. However I have experienced great enhancement by cryogenically tempering other steels both stainless and simple high carbon and certainly remain a firm believer in its incorporation.

For a steel that is so highly thought of for its toughness and so desired for chopping blades I would think a hardness of 58 HRc is quite respectable. I am impressed with it and glad I was allowed this opportunity.

RL
 
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