HT Issue

[Alex Roy]

I have a small hunter I made a couple of days ago. I brought it up to temp around 1600 by my guess, over non magnetic (easily).

 

Im quenching it in 10w-40 after about a 5 minute soak and repeated this three times. I slightly upped the temp each time and still a file bites it pretty well.

 

My guess is that the oil is too thick and its not cooling the blade fast enough.

 

What would you suggest for a quenchent and any other recommendation would be helpful.

 

Oh, I almost forgot the steel is 5160.

[Sam Salvati]

Vegetable oil, and some people say that multiple hardening decreases a steel's ability to harden.

[Alex Roy]

What about Auto transmission fluid with motor oil 1/1 ratio or 2/1?

[Beau Erwin]

I use McD's used fryer oil! *grins*

 

Oooh new forum thingies...err anyway yes multiple quenching can refine the grain of the steel, and can eventually decrease it's hardenability.

 

Fast food joints are usually willing to give away the oil if you want it, since they have to pay to have it shipped off anyway.

[Doug Lester]

What are you heating the blade in? Is it giving an even heat? Don't guess, get a magnet, they're cheap. Didn't take me long to learn that judging temperature by color is unreliable and I learned it by using a magnet on steel that I thought was hot enough, it stuck. How hot was the oil? It might have been too hot. The references that I have said not to to over 160 degrees. How long is it taking you to go from the forge to the quenchant? You only have a second or two, more than that you may have too much cooling on the way to the tank. As for right now, I'm tending to go with Wayne Goddard's opinion that the type of oil does't matter much. I've used a modification of Goddard's Goop, a combination of skillet drippings, vegetable oil, parafin, and a couple of old candles in a pan for edge quenching and peanut oil in a quenching tank and both have done real well.

 

Doug Lester

[Alex Roy]

I have a magnet, I used it and the heat was incredibly even.

 

I have a 15 gallon tank so mass isnt an issue.

 

I removed the blade and it went into the oil imediately.

 

The Oil was about 90 degrees.

 

I have used vegetable oil before and I had problem with mice jumping in and drowning, also I dont want to have to deal with the congealing at low temps, because in the winter around here it gets damn cold.

 

Im not about to buy a Pyrometer because Im dont feel like putting down another couple hundred bucks (Im in college).

[Guy Thomas]

Are you absolutely sure you are using 5160?

[guarnera]

I have a small hunter I made a couple of days ago. I brought it up to temp around 1600 by my guess, over non magnetic (easily).

 

Im quenching it in 10w-40 after about a 5 minute soak and repeated this three times. I slightly upped the temp each time and still a file bites it pretty well.

 

My guess is that the oil is too thick and its not cooling the blade fast enough.

 

What would you suggest for a quenchent and any other recommendation would be helpful.

 

Oh, I almost forgot the steel is 5160.

 

 

This gets mentioned often. Have you tried grinding a little off the edge after quenching to see if you hit hard steel? Often we forget about decarb. I had a knife I made out of 5160. I was using a torch and a magnet to H.T. Quench 1 was in heated oil. The file bit into it. 2nd quench into oil, same results. Third quench into room temp water, file still bit into the blade edge. I was stumped for a while, then I thought about decarb. So I went to the grinder and ground straight into the edge, and after not to much grinding I could feel that I hit hard steel. It was deeper then I thought. Maybe a 1/16th had to come off the edge. deeper then I thought it would be, but there was hardened steel under the soft decarburized surface layer. I hope this helps.

 

Tony G

[guarnera]

I have a small hunter I made a couple of days ago. I brought it up to temp around 1600 by my guess, over non magnetic (easily).

 

Im quenching it in 10w-40 after about a 5 minute soak and repeated this three times. I slightly upped the temp each time and still a file bites it pretty well.

 

My guess is that the oil is too thick and its not cooling the blade fast enough.

 

What would you suggest for a quenchent and any other recommendation would be helpful.

 

Oh, I almost forgot the steel is 5160.

 

 

This gets mentioned often. Have you tried grinding a little off the edge after quenching to see if you hit hard steel? Often we forget about decarb. I had a knife I made out of 5160. I was using a torch and a magnet to H.T. Quench 1 was in heated oil. The file bit into it. 2nd quench into oil, same results. Third quench into room temp water, file still bit into the blade edge. I was stumped for a while, then I thought about decarb. So I went to the grinder and ground straight into the edge, and after not to much grinding I could feel that I hit hard steel. It was deeper then I thought. Maybe a 1/16th had to come off the edge. deeper then I thought it would be, but there was hardened steel under the soft decarburized surface layer. I hope this helps.

 

Tony G

[Alex Roy]

I dont know whats going on, I quenched it one more time, After I grinded it and the file still bit, I got so of frustration, I put it in the vice and hit it with a hammer and snap, relatively fine grain on the inside, but the damn file still bite.

 

The destructive test tells me that it is hard enough to use as a knife, but Im going to do some testing.

 

Thanks for the input.

 

Tell me what you think.

Edited July 31, 2007 by Alex Roy

[Brian Vanspeybroeck]

Tony may be on to something....I have had situations where decarb will cause the edge of my 5160 blades to allow a file to bite them and appear to be soft. I don't think I have ever had to take 1/16th off to get to hard steel. Usually a couple thousanths tops.

 

My 5160 gets roaring hard quenched into anything from oil to 600F salt when austenitized from 1500 - 1600. If you are sure it is non magnetic at the quench then you have one of two problems. Decarb or it ain't 5160.

 

I have thermally cycled 5160 in descending heats from 1600f over 6 times and then quenched 3 times and the steel always gets hard. I think cycling low alloy or triple quenching can reduce the hardenability but certainly not to the point that it will no longer harden. If that happens you are playing with 10XX but not low alloy like 5160. IMO/IME

 

Brian

[guarnera]

I dont know whats going on, I quenched it one more time, After I grinded it and the file still bit, I got so of frustration, I put it in the vice and hit it with a hammer and snap, relatively fine grain on the inside, but the damn file still bite.

 

The destructive test tells me that it is hard enough to use as a knife, but Im going to do some testing.

 

Thanks for the input.

 

Tell me what you think.

 

 

Alex,

Are you using a new file? A new file will still give some bite on hardened 5160. The test is to be done with a semi dull or dull file.

[PMARTINKNIVES]

I dont know whats going on, I quenched it one more time, After I grinded it and the file still bit, I got so of frustration, I put it in the vice and hit it with a hammer and snap, relatively fine grain on the inside, but the damn file still bite.

 

The destructive test tells me that it is hard enough to use as a knife, but Im going to do some testing.

 

Thanks for the input.

 

Tell me what you think.

 

 

I would guess the steel is hardenable, I would also guess that your oil is tooooo slooow. Try warm tranny fluid at about 140 degrees, do a single quench(all you need), temper and then regrind the bevels a little and see how hard it is. Try to be successful with a single quench before attempting other fashionable multi quenches. Also, try a dull file and a new file, after tempering, the new file should bite and the dull one should skate off.

 

Peter

[kb0fhp]

I dont know whats going on, I quenched it one more time, After I grinded it and the file still bit, I got so of frustration, I put it in the vice and hit it with a hammer and snap, relatively fine grain on the inside, but the damn file still bite.

 

The destructive test tells me that it is hard enough to use as a knife, but Im going to do some testing.

 

Thanks for the input.

 

Tell me what you think.

 

Looking at the pictures of the fracture, you have a very small region surrounding the blade that is uniform. This is very suggestive of decarburization. Not knowing the dimensions of the cross section, it is not possible to determine the depth of the region. But I strongly suspect that decarb is the source for the part being soft.

 

On the broken piece, use a grinder and gently grind away about 1/16" and try the file again. It should be hard. You could also cut the piece in half with a saw and try the file on the inside of the piece - it should also be hard. If it is 5160 then just about anything will harden it - it is a very deep hardening grade. You could almost forced air cool it and it will get hard.

 

IMHO.

 

Scott

[Raymond Johnson]

Alex

Digital pyrometers are not that expensive.

You con get a pretty good one at harbor frieght. They call them digital thermomiture, but they will do everything a pyromiter will, because that's what they are. Marketing, what's up with that. They have stop carring them but most stores still have some in stock. Or they could get you one from another store or order it. Mine on clearance was $23

If that does not work for you, you can get one from Axner pottery supply for about $40. It is a modified volt meter, but works well. I have both. You wil still need to get a thermocople, but these are not that expensive.

Hope this helps.

[kb0fhp]

I would also use a fast oil - one that is meant for quenching - there are a lot of them. ATF fluid is mineral oil (usually) and it would be too slow. Motor oil is an unknown, and likely to stain the parts. It also has an unknown flash temperature. There is a reason quench oils have been developed, to get properties and properly control distortion. There a variety of sources, even some on this board that sell them in the necessary quantities.