I hate to beat a dead horse, but I have a few questions

[IH8U]

I just want to start by saying that I have searched and read multiple posts on 5160 stock removal and I have forged a couple of flint strikers that were heat treated ok.

Here goes: I'm using 1/4 inch 5160 that I got from a blade maker. I have almost finished the profiling and grinding and have left the edge about the thickness of a dime (give or take). I have some file marks left to remove before I want to heat treat it. Everything has been done by hand with files and sand paper. I plan on bringing the edge to non-magnetic and quenching in oil 3 times and then temper at 350 for an hour 3 times.

1. does my heat treating plan sound about right?

2. I have read about the file test (skating off the edge), but how am I to go about putting a cutting edge on it, if its already hardened with hand tools?

3. Should I complete the edge before I heat treat? I assume leaving the edge thicker prior to heat treat is to avoid warping and cracking?

4. I'm also under the assumption that hand buffing is exactly what it sounds like and is simply hand sanding with a high grit sandpaper?

Thanks and any assistance or comments are appreciated.

 

[LRB]

Non-magnetic is not enough. 5160 needs to be upwards of 1500o, and needs to soak for a few minutes at that temp. If you normalize it before the heat and quench process, you only need one quench. I would not temper at less than 400o. If you attempt to soak it, as it should be, you will need decarb protection, at least along the edge area. You will have to grind the edge in, or spend a lot of time on a coarse stone. A simple hand held belt sander would do the edge, but watch the heat build up. You might want to do some deeper research before you attempt this.

 

[Kevin R. Cashen]

Non-magnetic is not enough. 5160 needs to be upwards of 1500o, and needs to soak for a few minutes at that temp. If you normalize it before the heat and quench process, you only need one quench. I would not temper at less than 400o. If you attempt to soak it, as it should be, you will need decarb protection, at least along the edge area. You will have to grind the edge in, or spend a lot of time on a coarse stone. A simple hand held belt sander would do the edge, but watch the heat build up. You might want to do some deeper research before you attempt this.

Let me start by saying that I am in total agreement with you, however you do realize that there are scores of bladesmiths out there reading this (and I am surprised none have answered you yet) and saying that you are full of it because they have made a bazillion knives out of 5160 by just heating to nonmagnetic, quenching it (the more times the better), and tempering to 375F and they all worked just fine.

Going backwards, the 375F is always a dead give away that they only went to non- magnetic. Interesting games can be played with carbides from repeated quenching, however 5160 is about .2% carbon away from having any extra carbon to spare to carbides so those games don’t apply, the only thing to be gained is smaller grain size and as LRB has pointed out proper normalizing will get that just fine with 5160.

Steels with less than .8% carbon benefit from higher heating before the quench because they are basically made up of grains of low carbon iron with patches of more carbon rich phases scattered throughout. Heating to non magnetic will dissolve those carbon parts (pearlite) but will not move that dissolved carbon into the middle of the iron (ferrite) patches. Quenching from non magnetic will get you structures that will be harder around the outside but carbon starved in the middle. This will skate a file just fine but still not actually be as hard as it could be. Heating around 100F higher and holding it there will move the carbon entirely throughout and make a complete solution (austenite) which upon quenching will be entirely hard all the way through. And the addition of chrome only forces the temps higher to move that carbon (1525F for 5160). I should point out that I am speaking on an entirely microscopic scale here, the differential hardening by edge quenching is on an entirely different scale and I won’t even go there as that is up to the individual, but think we should at least get the parts we want hard completely hardened.

All that being said it is not always possible to nail the time and temperature to get the most out of a steel as we are often limited by the tools and techniques available. If the best you have is a magnet, then heat 5160 to non magnetic and then keep it there for a few minutes before quenching. Start tempering at 350F and check with a file or the best methods for checking hardness you have and bump the temp up by 20 degrees and temper again, repeating until you get the hardness you want.

As quenched 5160 is capable of reaching 62HRC and you may even find 61-61.5HRC from just going to non magnetic, but it will not hold that hardness near as long in tempering. A blade at is soaked at 1525F will need to go to 400F or better to get the same readings.

 

[Sam Salvati]

Well THAT just solved a WHOLE massive amount of issues. Kevin, what do you mean when you say "it will not hold that hardness near as long in tempering", are you talking about the regular loss of RC from tempering, or is it more so when just going from non magnetic.

 

[JTknives]

i have good results soaking at 1550 for 7 min and quenching in 115ºf minarial oil. then temper at 355-360 for 2-4 hrs. my edges are a little thicker than norm but with the testing i have done its been great.

 

[me2]

Well THAT just solved a WHOLE massive amount of issues. Kevin, what do you mean when you say "it will not hold that hardness near as long in tempering", are you talking about the regular loss of RC from tempering, or is it more so when just going from non magnetic.

I'm not Kevin, but I'll take a stab at it and see if he agrees. The steel benefits from an even distribution of carbon and chromium, which comes from a little bit of a soak at temperature to redistribute these 2 into the ferrite regions from the pearlite regions, which is where they are concentrated after annealing or normalizing. If the chromium is not distributed throughout, or still tied up in carbides from a low soaking time or temperature, it cannot slow down the softening of the steel during tempering, hence the lower tempering temperature will get the same hardness in a "non-magnetic, then quench" blade as the 400 degree or greater tempering temperature would in one that has the chromium dispursed and doing what its supposed to, which is give higher hardness at the same tempering temperature. To give a direct answer, the softening happens faster than normal during a non-magnetic, then quench procedure.

Does anyone know if 5160 has undisolved carbides, even a little bit, since the addition of chromium moves the eutectoid concentration down?

 

[Sam Salvati]

Wow Me2, thanks that's fascinating.

 

[Kevin R. Cashen]

Me2, I agree entirely, but I may put a little more emphasis on moving the carbon around than the chrome. Chrome is a pretty large atom compared to iron or carbon and I would hate to reinforce the misconception that substitutional alloying moves around all that much. The chrome is there and for the most part we give to it or rob from it the carbon needed to make carbides or saturated martensite. Once the chrome gets its hands on the carbon it just doesn’t like to let go so we need to free it up with heavier persuasion.

Does anyone know if 5160 has undisolved carbides, even a little bit, since the addition of chromium moves the eutectoid concentration down?

Does this answer your question? This is an image of 5160 that was undersoaked. I have images of material that was heated to 1525F with no soak and I have images of material that was heated to 1414F with a little soak, but I honestly can't remember which one this is but it is undersoaked.

As per my paragaph above, you have only a given ammount of carbon and then you have all that chrome floating around. 5160 will not make cementite (iron carbide) readily because there is just not enough carbon, but if there is a way to accomplish somethings abnormal in steel a bladesmith is the guy to find it. Mess around enough and all sorts of things can be done. With that chromium just sitting there waiting to snatch up carbon if you cycle the steel in ways that do not allow complete solution you are going to get patches of ferrite and loads of huge chromium carbides, but it will be at the expense of the martensites carbon levels. The image shows a fully quenched blade that was not soaked enough, so you have grains of martensite surrounded by proeutectoid ferrite (extra iron) but the grains themselves are littered with heavy carbides. This is exactly what I would also expect to see if one is multiple quenching 5160 if the temp is too low, on every heat the chromium can snatch more carbon while very little goes into solution, the problem is that as long as a taffy blade that easily bends is the benchmark there is no reason to realize that this is a problem. Carbide rich and carbon anemic martensite will seem hard and hold an edge from the carbides alone but it isn't truly hard throughout. This is also why people can get away with undersoaking and quenching in water, there isn't enough carbon in the martensite to crack or warp.

If this piece had been soaked, those same carbides would be there but they would be a whole heck of a lot smaller, in fact most would not even be visible at that magnification.

 

[jdm61]

I now use my Paragn to heat treat, but when I was using my forge, I found that if i quenched Admiral 1075 at non-magnetic and tempered it at 400, I ended up with an edge that was a tad softer than i would have liked. With Aldo's 1084, 1475 with a short soak and quench in Parks #50 leave a pretty hard edge even after a 400 temper. I may go to 425 on the next batch as the smaller stock has .85 carbon and the bigeer stuff .89. I temper my W2 blades at 475. Any comments on that Mr. Cashen?

 

[Kevin R. Cashen]

Well THAT just solved a WHOLE massive amount of issues. Kevin, what do you mean when you say "it will not hold that hardness near as long in tempering", are you talking about the regular loss of RC from tempering, or is it more so when just going from non magnetic.

Sam to expand on Me2's excellent explanation, Longer soaking would take the carbon from those carbides and saturate the martensite with it. Tempering takes carbon back out of the supersatured martensite allowing it to relax and thus give lower hardness readings. The more carbon you put into the martensite to begin with, the more will have to be taken out to see the same readings. A person should not see any real changes in hardness at 350F or below in tempering unless the martensite barely has enough carbon to maintain that hardness to begin with, then very low tempering temperatures moving very miniscule ammounts will make a difference. However if a good ammount of carbon got put into solution, you will have to go much higher in tempering to achieve the same effect and the carbides formed, as well as those left over, will be incredibly fine and well dispersed, which will make a much stronger steel that will resist abrasion.

 

[mete]

The whole point is to saturate the martensite , otherwise you never get the full properties.Tempering will take out quench stresses and produce fine carbides .I would start at 400 F. There is no need to temper more than once with 5160 and I would do it for 2 hours.More complex steels need 2 or three tempers.

 

[Kevin R. Cashen]

I now use my Paragn to heat treat, but when I was using my forge, I found that if i quenched Admiral 1075 at non-magnetic and tempered it at 400, I ended up with an edge that was a tad softer than i would have liked. With Aldo's 1084, 1475 with a short soak and quench in Parks #50 leave a pretty hard edge even after a 400 temper. I may go to 425 on the next batch as the smaller stock has .85 carbon and the bigeer stuff .89. I temper my W2 blades at 475. Any comments on that Mr. Cashen?

I would have to go back through my files to find them*, but I found that I had to go to 500F or better on 1095 to get some hardness levels I was looking for in impact testing a few years back. I was astounded at the time at how little the Rockwell reading moved after each hotter tempering. The same thing is applying here and it is quite elemental- the more carbon in solution, the harder the steel.

Your 1084 can handle a bit more heat in the soak (1500F) as you do not need to be concerned about too much carbon. Yep! Thats right, things just got more complicate. When the steel is above the eutectoid and it is simple with no carbide formers, you then need to stay a little lower in the soak so as not to put too much carbon into solution and get greater chances of distortion, cracking, or retained austenite. Here the ideal would be to put around .7%-.8% carbon into solution and any remaining carbon wuold be inthe form of very fine and evenly dispersed carbides (a bit trickier than it sounds).

If you do large series of test in order to show the trends in numbers, you can watch a steel like 52100 peak in hardness around, and even below, 1475F with a real good soak, and then actually start giving lower Rockwell readings as you go higher in soak temperatures. This is due to increasing ammounts of retained austenite caused by excess carbon in solution.

This is one of the reasons why 5160 is considered a good begginers steel, even though I say it should be more carefully soaked- it is really hard to overheat it. 1084 is easier to heat treat without controlled soaks than 1095 since it is more difficult to overdo things, 1095 gets really ugly when you over heat it


*Forgive me if I often referrence notes that I do not have on hand but I have vertically stacked filing everywhere and too many notes over the years to keep track of. I have two full drawers and a couple of boxes of mounted metallography samples with little or no labeling, I am hopeless

 

[IH8U]

Holy science lesson, thanks for all of your input guys. I did speak to Mr. Gossman, whom I got the steal and asked him how he hardens this same steel. My first question was about "normalizing" since I have not heard about that process. If I had forged the blade, then normalizing would be the next step, but since it was just stock removal then there shouldn't be a need. The steal was completely annealed from the beginning.

So If I decode some of Kevin's science and take into account Mr. Gossman's suggestions, this is how I figure I should proceed.

1. Fire up the poor mans forge and heat her up to non-magnetic and let her sit for a few more minutes to try and reach about 100 degrees above non-magnetic.
2. Quench in warm, clean motor oil or tranny fluid. (Scott suggested 120-140 degrees)
3. Once the blade is just warm to the hand, throw her in the oven at 400 degrees for an hour, let cool for an hour and repeat for a total of 3 tempers. Using a thermometer to ensure its at 400 degrees.

So, I think I have a good process to follow. Its my first blade and I have spent a lot of time filing and profiling and want to make it the best I can.

With the heat treating out of the way, does anyone have any suggestions on putting a final edge on after its hardened? If my files skate off the edge, I think I'm going to have some issues making her sharp, I have what I believe are some small diamond coated files, how will those work? As LRB suggested a coarse stone or use of my hand belt sander will work, but take up a lot of time. It's just going to be a real bee-otch using the hand sander and keeping the grind straight.

Again, thanks for all the assistance. I can't wait to take some pictures and finish her up.

 

[PIndelicato]

IH8U,

It seems we are not too far apart geographically and also project-wise (although you are a few steps ahead of me.) I too am working on my first blade, and it's a 5160 stock removal piece done all by hand.

I don't have anything to add, but I'm curious about this heat treating discussion and also to see how you progress to the end. Do you happen to have any pics of your knife as it currently sits?

 

[IH8U]

IH8U,

It seems we are not too far apart geographically and also project-wise (although you are a few steps ahead of me.) I too am working on my first blade, and it's a 5160 stock removal piece done all by hand.

I don't have anything to add, but I'm curious about this heat treating discussion and also to see how you progress to the end. Do you happen to have any pics of your knife as it currently sits?

I will take some pics tonight. I should have taken some last night, but I was trying to get all of the deep file marks out. I have even made some brown micarta for the handle and I'll snap a few shots of that too. She is looking good if I do say so myself.

 

[Sam Salvati]

Sam to expand on Me2's excellent explanation, Longer soaking would take the carbon from those carbides and saturate the martensite with it. Tempering takes carbon back out of the supersatured martensite allowing it to relax and thus give lower hardness readings. The more carbon you put into the martensite to begin with, the more will have to be taken out to see the same readings. A person should not see any real changes in hardness at 350F or below in tempering unless the martensite barely has enough carbon to maintain that hardness to begin with, then very low tempering temperatures moving very miniscule ammounts will make a difference. However if a good ammount of carbon got put into solution, you will have to go much higher in tempering to achieve the same effect and the carbides formed, as well as those left over, will be incredibly fine and well dispersed, which will make a much stronger steel that will resist abrasion.

Thanks a load Kevin, this rearranges my whole way of thinking and understanding concerning hardening and tempering:thumbup:, the alloys and materials in the steel already really do have MAJOR effects on EVERYTHING. Are all the proper temperatures for soak temps and stuff the ones stated on the stats in TTT diagrams and stuff for each given steel, or with your testing did you find they were a bit different for blades?

 

[sunshadow]

I would have to go back through my files to find them*, but I found that I had to go to 500F or better on 1095 to get some hardness levels I was looking for in impact testing a few years back. I was astounded at the time at how little the Rockwell reading moved after each hotter tempering. The same thing is applying here and it is quite elemental- the more carbon in solution, the harder the steel.

Your 1084 can handle a bit more heat in the soak (1500F) as you do not need to be concerned about too much carbon. Yep! Thats right, things just got more complicate. When the steel is above the eutectoid and it is simple with no carbide formers, you then need to stay a little lower in the soak so as not to put too much carbon into solution and get greater chances of distortion, cracking, or retained austenite. Here the ideal would be to put around .7%-.8% carbon into solution and any remaining carbon wuold be inthe form of very fine and evenly dispersed carbides (a bit trickier than it sounds).

If you do large series of test in order to show the trends in numbers, you can watch a steel like 52100 peak in hardness around, and even below, 1475F with a real good soak, and then actually start giving lower Rockwell readings as you go higher in soak temperatures. This is due to increasing ammounts of retained austenite caused by excess carbon in solution.

This is one of the reasons why 5160 is considered a good begginers steel, even though I say it should be more carefully soaked- it is really hard to overheat it. 1084 is easier to heat treat without controlled soaks than 1095 since it is more difficult to overdo things, 1095 gets really ugly when you over heat it


*Forgive me if I often referrence notes that I do not have on hand but I have vertically stacked filing everywhere and too many notes over the years to keep track of. I have two full drawers and a couple of boxes of mounted metallography samples with little or no labeling, I am hopeless

So Kevin, am I alright soaking 1084 and 1095 at 1550f? or should I back down to 1500?

confused again
-Page

 

[IH8U]

IH8U,

It seems we are not too far apart geographically and also project-wise (although you are a few steps ahead of me.) I too am working on my first blade, and it's a 5160 stock removal piece done all by hand.

I don't have anything to add, but I'm curious about this heat treating discussion and also to see how you progress to the end. Do you happen to have any pics of your knife as it currently sits?

I got some pics for you during my lunch hour. Please ignore the first hole nearest the blade, I call that one an "oopsy". Here you go, enjoy!

Specs:

5160 steel
pseudo convex grind
0.25 inches thick
6 inch blade
5.5 inch handle
1.25 inch wide blade
Handle will be home made chocolate brown micarta - see last couple of pics (I have some iron wood (thanks Scott), but unsure if it will go on this project)
I will be using (2) 0.25 inch solid aluminum pins for added cosmetic appeal

 

[PIndelicato]

That looks great, and I really like the handle shape you came up with. How did you accomplish the pseudo-convex grind?

I posted a link to a pic of my progress in my other thread if you want to check it out.

 

[IH8U]

Starting my grind from about the middle of the blade, I just added more pressure with my down stroke as I got closer to the edge. I have a black and decker work bench that I could lock the knife into at an angle and that probably helped out a lot and allowed me to add the extra ummpphh where I needed it.

I'll track down your other thread.