How do I know if I got the quench right?

SpacemanSpiff23

SpacemanSpiff23

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Feb 22, 2009
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I just quenched my first blade, and it didn't explode!!:)


I've heard that you should test it with a file, but I don't know what the outcome of the test should be. Should it not scratch it at all, or should it just barely scratch it, and not bite in at all?

I'd like to be sure before I go through the 4 hour tempering process.


Is there any other simple tests I can do to make sure I got it right?

Thanks for all the advice and help so far, I'm almost there!
 
Being as detailed as you can in a post like this would be very helpful. Including info such as, but not limited to:

type of steel,
austenitizing temperature
normalizing routine, if any
soak time, if any
type of quenchant
temperature of quenchant
whether or not any agitation was used.

Getting it right, in my opinion, means doing all or as many things as possible by the book in terms of the HT recipe for a particular steel.
 
It is quite no bite at all, if it bites it might be bitten the decarb layer, so try to sand the grayish layer before testing. If file is very fresh and good quality there is a possibility of a minor scratch but there should be no bite at all, it must scate on the steel...
There are some other tests but the file test is the most practical one. Some also crack a piece from the tang area for hidden tang blades. I did that also, but it was not for hardness testing but to ispect the grain, be sure to make the tang longer that needed...
 
yes the file test is good. all it will tell you is if it got hard. Now one thing to remember is that you could have a thick layer of decarb on the surface of the blade depending on what you used to heat your blade. If i do a file test i use a used file and try to file the edge like i was trying to sharpen it. if you have bad decarbe the file will bite till that layer is gone then it will slide of. i have a video on my site on how to do a file test.
 
69_knives said:
Being as detailed as you can in a post like this would be very helpful. Including info such as, but not limited to:

type of steel,
austenitizing temperature
normalizing routine, if any
soak time, if any
type of quenchant
temperature of quenchant
whether or not any agitation was used.

Getting it right, in my opinion, means doing all or as many things as possible by the book in terms of the HT recipe for a particular steel.
Click to expand...


I don't know the type of steel, it was an old file. This is my first time doing this, so I don't really know all the vocabulary. I Heated it up to non magnetic, let it cool (normalized it), checked to see if it bent at all. Then heated it back up to a little above non mag, and quenched it in canola oil that was about 110 degrees. Then I sanded it off, scrached it a very little bit with a file and moderate pressure. I threw it back in the heat, and quenched it 2 more times. The third time might have gotten a little too hot, as the color was much brighter than the previous 2 times. I sanded it off again, and the file had a much harder time scratching it. Now it's sitting in my rather finicky oven at around 410-430 degrees.
 
The thing that has me so worried is that even with crappy charcoal briquettes, I still managed to get it up to non magnetic in about 4-6 minutes. It just seamed too fast.
 
As I and many others have found out, working with unknown steel can be challenging. If you have a lot of it it is worth it to have it tested professionally to find out what it is or at the very least, do extensive HT testing yourself even destroying several pieces to see grain size and hardenability and what works best in getting it right.
 
What non-magnetic tells you is to raise the heat a couple of shades redder before quench. Non-magnetic is 1414°, and most steels need to be at 1475°, to 1500°. The file should just skate across the steel after quench, unless, as mentioned, you have a bit of decarb. Then you need to remove that. The problem with the file test, contrary to popular belief, is that a common file will not cut steel harder than 58/59 Rc, so it really DOES NOT tell you that you got the steel full hard. However, without buying testing files, that is about as good a test as can be done.
 
OK, here is what we little knifemakers that cannot afford a RC tester can do. Do find a friend with a RC tester and beg him to use it a couple of times. Then do make half a dozen basic chisels and HT them full to 64-65 HRC but dont temper them for now. Test them with the temporary RC tester of your friends and check if they all are fully hardened. Take the highest reading sample and sign the RC measurement on that. Then take one and temper it at lowest temper temp. And test it and sign the measure on that. Take the third and temper at a bit higher temp. and sign it, and lower the hardness of each one than the previous one. Now you have lets say a 65 , 63 , 61 , 59, 57, and for example 54 HRC chisels, exactly known hardnesses of those you can now pretty precisely test your knives from now on...
Ok it may sound silly, but it may work. What do you think?
 
The old fashioned way to tell if the quench went right is, whether or not it popped the scale or patina/oxidation off in the quench. It should pop a good deal of it off and leave sort of a freckled look, at the least. Generally, if it popped scale off well and didn't crack or warp, the quench went alright,... but this should always be followed by some in shop and/or field testing after tempering to make sure.

Checking with a sharp file after the quench is also a good idea, but do it "comparatively" against some tools of known hardness and composition.
 
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Another thing I have done is used the tip of a knife to scratch the bade in question. On an edge quenched or clay quenched or a poorly hardened blade, you can tell by how deep the scratch is across the blade roughly how hard it is. On a clay quenched blade, the hardened edge shouldn't really make any mark except for leaving some color from the scratching blade. if you scratch across the blade the scratch will get deeper in a softer area.

I've been contemplating making a set of scratching awls from 1095 with 10 or 20 degree F increments of temper starting at 350 and up to 475. With those I should be able to discern somewhat what the level of hardness is. Maybe I could also do a second set of samples and have them RC tested and matched up the the awls.
 
A problem with making test files is that if you make one that reads 60 Rc, it is going to behave just as a common file. It may stop cutting other steel at around 54 Rc. A common file is generally in the 64/65 Rc range as far as I know, but will stop cutting at 58/59 Rc, so you will have to make adjustments, and do testing in order to really know where you are with the hardness you have in mind. What I'm trying to say is, a 60 Rc file is going to skate probably 5 points or more, under your target hardness, so just because it skates, doesn't mean you at 60 Rc. In my experience anyway. I could be wrong, but I don't think so. Obtain a piece of steel that you KNOW is 58/59 Rc, and see if you can cut it with a common file, then I believe you will understand.
 
Sharp or new files work better on higher hardnesses. If you use a sharp file and do some comparison testing, you should be able to tell the difference between a Rockwell 65 and 62 fairly easy. Also if you decrease the surface area of contact, you will get better readings at higher hardnesses. Use the edge or corner of the file not the broad flat surface. It can also be helpful to lay a sheet of clean white paper under the test piece and check for particles of steel coming off.

If you start with a good sharp fairly fine single cut file (approx. Rockwell 65), and use the sharp corner of it instead of the broad flat surface, (across a surface area of 1/16th to no more than 1/8 inch on the test piece), you will see a small groove or scratch from it on pieces around Rockwell 60-62, whereas on pieces around Rockwell 64-65 it will slide across the surface and just shine it or burnish it a little, no matter how much hand pressure you apply. If the file is sharp and about a Rockwell 65, it will only completely stop cutting against another piece that is also about a Rockwell 65.

I think that there is a popular new myth that a file of about a Rockwell 65 completely stops cutting at around a Rockwell 58,... which really doesn't make sense anyway.
 
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Don Hanson III said:
Like Tai said, the scale popping off is a very good first indicator that the blade hardened.
Click to expand...


Is it my imagination, or does the scale action also tell you when you've over heated it (by not popping off)?
In other words, this only works, or at least works best, when you're right on temperature?


Mike
 
Scale not popping off is an indication of under heating and/or too slow a quench. Over heating should try to be avoided. I haven't done any tests on the scale reaction of over heating, but my feeling is that it would still pop scale. So, I try to stay close to the temperature where it pops scale well, but not a lot hotter. Hotter and faster is not necessarily better. In other words, you want it hot and fast enough to pop scale well and fully harden the blade, but not a lot hotter and faster than that. Again, it’s always a good idea to test the blade after heat treating, to make sure, or at least until you have the temp., and quenching medium worked out for a particular steel.
 
Tai, I stand corrected. Using a new file in the manner you described does cut at least 60 Rc. I have nothing harder on hand to check, but I suspect you are right in what you said. :foot: :thumbup:
 
That technique, with the corner of the file, works well up to about a Rockwell 62. If it's close to a 65 the corner of the file won't do anything but shine the test spot a little and skate right off.

At about a Rockwell 58, you can use the broad flat surface of the file, and even though it feels and looks like it's skating, if you lay a sheet of clean white paper underneath the test piece you will see tiny particles of steel coming off. If it is much harder, around Rockwell 62, the particles could just be teeth chipping out of the file, but they usually are larger.

Another good test, (for after tempering), is impact testing or chopping. You can use a piece of hardwood, and/or chopping through some heavy gage mild steel bailing wire over a piece of hardwood, and/or chopping at about a 45 degree angle into a brass or bronze rod, and checking for chipping or plastic deformation. Of course the desired results would depend on what the blade would be used for and what is desired. Again some comparison testing is a good idea.

If the edge is brittle, chips out easily and/or dramatically, comparatively speaking,... it's usually from overheating and grain growth in the quench cylce, and/or or not enough tempering.
 
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I am by no means of the same abilities of many of the folks who have offered info here, but here are some of the things I look for, in addition to the file test:

1. Scale comes off easily. I clean a freshly quenched blade in the dirt, wiping the oil from the quench off. Often the dirt contains sand or very small gravel, and if the quench is good the scale just sort of "wipes" off.

2. I can somewhat tell by the feel or sound of the metal when it is tapped against a hard surface, like my anvil. If it has hardened, it has a sharper, more brittle sound than if it is still softer.

3. I can tell quite a bit when I start to clean the scale off when I take it to my belt grinder. It works a certain way if it has hardened, or if it is soft. It will also spark the same way all the way the length of the blade.

4. After tempering, while working down to the final edge, I keep an eye on whether the steel works quickly or slowly, or if it seems softer in some places and harder in others.

I make mostly larger blades. I don't know if other folks look for these, but it's what I look for.

Hope this helps.

Andy
 
Wow, thanks for all the replies. I think I got it right. TH scale did pop off really easily when I quenched it, and the file didn't do any damage to it after I sanded off the remaining scale/crud.

After heat treating, it turned a perfectly even yellowish/brassy color that made me really happy. I'm almost done it now (working on the handles, and then I'll start polishing everything and then sharpen.
 
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