Multiple quench

Fiddleback

Fiddleback

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I use 01, 5160, and 1095 steel to make my knives.

Another thread at another spot discussed tripple quenching. Is there a reason to do this? Is it steel specific?
 
The thread Andy refers to had to do with the forging of this knife -

DSC02660.jpg


I triple quenched this knife in old motor oil.

The steel is likely 1080-1084 or similar. Do you think the triple quenching might have caused this?
DSC02667.jpg


Can you see the cracking?

Thanks! And thanks for starting the thread, Fiddle. I was just over here to do that.

Andy
 
Andy, The short answer is "No."

If you have properly austinized your steel at the correct temperature, then quenched in real heat treating oil (or salts), and everything was done to readily available metallurgical standards, the only good reason for a triple quench is the cool extra hamons it can leave. Now, on the other hand, if you've screwed things up, a triple quench might get you back about to where you should have been in the first place.

By the way, this is a controversial subject, so I'll probably get flamed by the people who've never looked at the Heat Treaters Guide. :rolleyes:
 
Oops, now their are two Andys. My initial response was to Fiddleback.

Andrew, check with Kevin or Mete, but my guess would be that the cracking was caused by overheating.
 
Thanks Chris. I can't imagine getting flamed without taking a position either way, but if necessary to get the requested knowledge, so be it. Flame on.
 
Quenching an oil or water (not air) hardening steel multiple times decreases the grain size. That is the whole purpose of doing so.

Your corroded blade was not caused by quenching multiple times.
 
I thought normalizing reduced grain size.

Mete, where are you brother?
 
Right here !! Triple quenching is used to get minimum grain size .Normalizing stress relieves, makes uniform grain size [that's why we want it after forging] and reduces grain size to a degree [but does not minimize grain size]...The surface problems pictured where not caused by triple quenching unless you went way above normal temperatures. If you have surface problems like that after forging or after any step in HT grind it off least it cause other problems such a s cracking.
 
OK, to summarize - triple quenching can be a good thing. Normalizing is a good thing... but clearly excessive heat is a bad thing.

Now, I'm using a homebuilt bucket charcoal forge, and I'm just heating to above non-magnetic (using the magnet about every third time, going by color the rest of hte time).

How hot above non-magnetic would I have to go to see the kind of cracking I got in that photo? Can I go that hot with my setup?

Evidently I can... but how to avoid this in the future?

Andy


mete said:
Right here !! Triple quenching is used to get minimum grain size .Normalizing stress relieves, makes uniform grain size [that's why we want it after forging] and reduces grain size to a degree [but does not minimize grain size]...The surface problems pictured where not caused by triple quenching unless you went way above normal temperatures. If you have surface problems like that after forging or after any step in HT grind it off least it cause other problems such a s cracking.
Click to expand...
 
mete said:
Right here !! Triple quenching is used to get minimum grain size .Normalizing stress relieves, makes uniform grain size [that's why we want it after forging] and reduces grain size to a degree [but does not minimize grain size]...The surface problems pictured where not caused by triple quenching unless you went way above normal temperatures. If you have surface problems like that after forging or after any step in HT grind it off least it cause other problems such a s cracking.
Click to expand...


Thanks Mete, you are a great asset to this forum.
 
Please forgive me as I KNOW I'm about to hijack this thread, but hopefullty to the betterment of knowledge for all involved....At least all the unknowing such as myself:D
When triple quenching could you please explain how this is done. I have an evenheat oven and quality quenchants, but not sure exactly how one goes about the rapid climb to critical associated with this procedure. Should I just leave my oven on at the desired temp, pull the blade out, quench, and stick the blade back in until I THINK it has come back to temp again and repeat?:confused:
Sorry just a bit confused
Matt
 
mdoyle said:
When triple quenching could you please explain how this is done. I have an evenheat oven and quality quenchants, but not sure exactly how one goes about the rapid climb to critical associated with this procedure. Should I just leave my oven on at the desired temp, pull the blade out, quench, and stick the blade back in until I THINK it has come back to temp again and repeat?:confused:
Sorry just a bit confused
Matt
Click to expand...


Yeah, that sounds right to me, though I'm not speaking from experience.

It appears you need to heat it quickly. There is an explanation in the text, the gist of which is you only want to dissolve around grain boundary, otherwise large grains absorb small grains, which is not what you want. If you start to melt around grain boundary, then quench, you now have more grains = finer grain. Fast heat to lowest effective temp, then quench. The procedure he used is below:



Excerpt from

Metallurgy of Steel for Bladesmiths & Others

who Heat Treat and Forge Steel

by John D. Verhoeven





"When heat treating to form martensite, toughness is also enhanced by fine grained

austenite because it results in a finer lath or plate size in the martensite. Again the same

ideas apply. Rapid heating and repeated cycling produce smaller martensite

microstructures. Grange [8.3] has presented a study showing the beneficial effect of

small austenite grain size on the mechanical properties of 8640 steel. He achieved grain

sizes in the ultrafine range of ASTM No. 13 to 15 by a 4 cycle process where the steel

was austenitized in molten lead for around 10 s, cooled to room temperature, cold worked

and then cycled again. A series of similar experiments was performed here on 3 steels to

examine the effectiveness of thermal cycling alone, no cold working was employed. The

steels were heated by immersion in a salt pot. Initially the steels were austenitized for 15

min. at 1650 oF and oil quenched in rapidly stirred oil. Then the steels were given 3

thermal cycles consisting of a 4 minute austenitization in 1450 oF salt and a quench in

rapidly stirred oil. The grain sizes were measured with the same technique described by

Grange [8.3] and the ASTM numbers before and after the 3 cycle treatment are given in

Table 8.2. It is seen that ultrafine grain sizes were obtained."
 
This thread has been an excellent help to me. Thanks to you all!
 
No quenching operation caused the damage on the blade pictured, it is classic results of time at too high a temperature in the wrong atmosphere (mostly too hot). There are other ways, and I would submit better ways, to reduce grain size besides being redundant with your quench. THe impression is given too often that this is the only way.

I am currently working on one of the largest widescale studies on heat treating and austenitizing I have yet done, and as usual the metallography has blown all my concepts of attempting to simplify things involved in these process's. One cannot make blanket statements for different steels treated in different ways, and carbides just plain change everything! What you do in forging, normalizing and annealing, will set everything up for the final heat treatment.

From my observations the number one thing to do with any steel capable of forming carbides is keep them out of the grain boundaries! If they collect there, all future attempts at grain refinement will be in vain without first dissolving them, which will require temperatures that will cancel out all the work you may have so far done. Some steels that many believe are fine for beginners or the simplest of shops are even more problematic than I thought, and the reason so many smiths do all kinds of whacky things to refine grain is because of the difficutly in doing so with the tools an methods they have available for the choice in steels.

I don't mean to start a panic but with some steels one great way to put carbide in the grain boundaries, and lock in the size of your grains, is to stuff the blade into your forge and walk away for the day:eek: . I now know why I love spheroidizing, it does take much longer to disolve the balled carbides, but those little balls are scattered very evenly throughout the matrix, not in the previous grain boundaries, so they provide more points of new grain formation on the very first reheat.

I have a lot of data to analyse and draw final conclusions from but this latest round has thrown huge new issues on my plate. When you have control over the variables and can work within tigher parameters, anomolies and unpredicted results are great! You can then analyse them and the causes and learn things you had never expected!

I hope to organize my findings into solid materials to present to our field in a way not previously done - explanations backed up with hard data on the actual cause and effect, not wishful thinking or hype.
 
Kevin R. Cashen said:
No quenching operation caused the damage on the blade pictured, it is classic results of time at too high a temperature in the wrong atmosphere (mostly too hot).
Click to expand...

Very good, thanks, let's run with this a bit if you don't mind.

As I said, I have a bucket forge with a small blower on it. I use natural charcoal, and use a magnet to determine temperature.

If I don't use the magnet, I use color as a guide for temperature, pulling the steel out for forging when it is a good, through orange, and quenching when it is just past this solid orange, into yellow.

I annealed the blade by leaving it in the forge overnight, in the ashes. The blade was normalized three times before quenching.

I don't know how hot I can get my forge, and I don't know at what stage I overheated it.

For my purposes, how can I prevent overheating without the use of a temp. probe of some kind?

Andy
 
Kevin R. Cashen said:
I hope to organize my findings into solid materials to present to our field in a way not previously done - explanations backed up with hard data on the actual cause and effect, not wishful thinking or hype.
Click to expand...

Kevin, I hope this results in a book, I'd buy it. Would you advocate a speroidizing process as an essential step prior to heat treating, including simple high carbon steels like W1 and 1095?

Now if Howard would get around to writing one too...
 
Andrew Colglazier said:
Very good, thanks, let's run with this a bit if you don't mind.

As I said, I have a bucket forge with a small blower on it. I use natural charcoal, and use a magnet to determine temperature.

If I don't use the magnet, I use color as a guide for temperature, pulling the steel out for forging when it is a good, through orange, and quenching when it is just past this solid orange, into yellow.

I annealed the blade by leaving it in the forge overnight, in the ashes. The blade was normalized three times before quenching.

I don't know how hot I can get my forge, and I don't know at what stage I overheated it.

For my purposes, how can I prevent overheating without the use of a temp. probe of some kind?

Andy
Click to expand...
Kevin's research and info is very valuable to us makers out here, but it's hard to fully use for the charcoal using, shade tree maker :D

Are you forging in a low light area or outside in bright light? The temp of your hot steel will be greatly different from one to the other.

Most new makers overheat their blades when heating to be quenched. Bright orange to yellow is way too hot. Get the blade up to red in low light, as it slowly continues to come up in temp, it will brighten suddenly, hold it there for a bit, if you can and quench. A magnet will help find this temp (1400f to 1500f) but remember, a magnet will not stick to a overheated blade. So once you pass this temp, the magnet is no good.

For normalizing, heat to a little over non-magnetic once and twice at non-magnetic.

This should help the 'shade-tree-charcoal-smith' but listen to Kevin and work towards higher goals.
 
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