Steel Weirdness.

JTknives

JTknives

Joined
Jun 11, 2006
Messages
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I don't relay need help but just have some questions about some tests i have been doing. first off i started with a chunk of 5160 that was 1.75" long by about .75" wide and .25" thick. i put it in the heat treat oven and took it up to around 1540 give or take 10 or so deg and let it soak for around 10 to 15 min at temp. then pulled it out and oil quenched it in 65 deg or so warm motor oil. I know i know i should have used my good oil and warmed it up a bit but this was kinda a fly by night test and my other oil was in the other shop:o. any way, there was not much scale on the bar, at least not more then normal. i ground a bit off the flat surface and took a RC test and came at about 61.5 which was not bad as i was using Luke warm motor oil. i then took it to the vice and clamped maybe a half inch it it and tried to break it with a large hammer. after a few very hard whacks it snapped. i garbed my loop and checked out the grain size and it looked good, a nice even gray color. This result was not a suprize at all as i have been working with this material for a while. i did that so i could compare it to another test i did after that.

so i took a slice of what i believe is L6 from crucible as i sliced it from a very large round that had L6 wrighten on it. so this chunk of L6? was 5/16" thick and around 7/8" wide and 6" long. i put it in the heat treat oven at the same temp as the 5160 and let it soak for 20 min. after 10 min or so the bar had developed very bad scale, it looked like a bubble around the whole bar. the scale had puffed up away from the bar quite a bit, probably almost 1/8". i then pulled it out and quench it with a blast from the compressed air hose till i could touch it. then i gave it a quick rinse in the sink. all the puffy scale got blasted off with the air hose and the bar did not look to scaley. I then took it to the grinder and removed the surface decarb layer like i did with the 5160. I then tested the RC and it came in at around 56RC. then to the vice to see if i could break it in half. i clamped about one inch in the vice and started hitting it as hard as i did the other one. but nothing so i relay waled on it as hard as i could and still nothing. remember i was hitting the top of the bar and that was sticking out 5" from the vice and it was stronger then the 5160 that was onley sticking out just a little more then one inch. I could not get the L6? bar to break. so i went to the 20 ton press and suspended it between 2 bars of steel. the space between the bars was a little more then 4 inches might even been 4.5". so i started pressing on the center of the bar and the bar started to flex and it started to get hard to pump the press. i turned my face away and kept pressing it. then all the sudden there was a very loud PING and the bar broke in half, half of the bar shot across the shop. i grabed the bar that was still on the press and checked it out with the loop and i was shocked. it had a very fine grain structure, more fine then the 5160 and much more smooth looking. I could see where the steel failed as there was very faint lines all starting at a corner of the bar and then spread out as they made there way to the other side of the bar.

So i guess my question is this, I dont know what to ask:eek::foot:.
but relay i was not expecting that much strength from just air hardening the L6? bar. But then agen i have herd that crucibles L6 is a kind of air hardening. also whats up with the weird scale i was getting. i would say i over heated it but the 5160 was fine at the same temp and i had my new pid connected to the oven as well just to make sure. does any of what i have described sound Like property's of L6 or am i just smoking crack. I realy dont know if this is L6 other then L6 is wrighten in both ends and i got it from my surplus steel place. but i have never had any problem with wrong labeling from them before. Thanks for reading my nonsense.
 
J any steel with nickel in it will want to scale more than a steel with out it chances are it is indeed L6.

Bob
 
JT,
First, L-6 is a designation, not a formulation. There are several formulation types of L-6. Some are much different from others. The carbon can range from .50 to .75, the norm is .60 to .75.

L-6 has an austenititizing range from 1455-1555F, so you were on the high end. As said, Nickel steels will scale more if unprotected.

L-6 can be forced air or warm oil quenched.

As for the forced air quench.-
The nose for L-6 ranges from 10 seconds (to get below 700F) to over 2 minutes for some of the formulations. Forced air would easily do this. The chart comparing L-6 ,with .75C, quenched in air vs quenched in oil lists the as quenched hardness at 1550F as 64 for oil and 63 for air. At 1590F it is the same Rc 63 for both. That info would suggest some serious auto-tempering happened in the cooling of your sample ( if it was .75C). What you did was a good industrial procedure to get a spring temper in L-6 - if it is .75C.

To see what a change in the carbon content can do, look at the chart on .50C L-6 compared to .75 L-6. It shows the Rc as 63.5 for .75C and 57.5 for .50C when quenched in oil from 1525F.

Now ,using this information and comparing it to your results, you may have low carbon L-6 made for an industrial purpose, or high carbon L-6 that auto-tempered. Only an analysis will show which L-6 it is. ( this is one of the exact points in my "steel snob" postings). The good thing is that you tested it ,and have some idea of where to proceed from here in making knife blades. I would do the same tests with two pieces of the L-6 and compare the results to oil vs air. This will tell you a lot more.

So you probably did everything right.....you just didn't know what you were doing.( in a metallurgical sense)
This is one of the pitfalls in comparing steels. It is often apples to oranges. If all you look at is the fact that they are both round - then they are identical.
If you look at what is inside - they are as different as you can get.

Stacy

Did Barb's present fit?
Stacy
 
thanks stacy, i will do another batch of 2 and i will oil quench one and air quench another. i just have vet grade mineral oil but it has been great for my 5160 so it should be good for the l6 i would think. anything thing i should test.

yes Stacy her present fit great. I'm a little worried about using it in one of my knife shoots because then i have 2 things taking attention away from my knife ;), one is Barbara's hot tummy and that sweet belly button ring you made her. o well i will just have to make an amazing knife then wont i.

O and i am a steel snob as well, that's why I'm doing the testing i am. i hate working with unknown material. And knowing that the steel just gets hard when quenched is not enough for me, I have to know more.
 
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JT,
The only thing that worries me is the turning your head and letting steel fly around at high speed part of your testing. Find a way to break it safely please. Make up some kind of guard for your press to contain any flying pieces of metal!
 
It would have been cool if you did a side by side quench in motor oil, and another in whatever comercial stuff you had on hand on the 5160, and then test the hardenss with a 400-450f temper. Chances are there wouldn't be much difference.
 
scottickes said:
JT,
The only thing that worries me is the turning your head and letting steel fly around at high speed part of your testing. Find a way to break it safely please. Make up some kind of guard for your press to contain any flying pieces of metal!
Click to expand...


I agree 100%. Turning you head just means changing the strike angle of the blow that could kill you. I was once struck with a tiny sliver of steel from a misalignment punch press punch, It went thru my cheek and struck me in the gum well below my teeth and it felt like I took a hard hit with a hammer. The shard was about 1/4 long and maybe a 1/16 wide. I thought it it had ripped my face open and broke my jaw. I have taken a few hits. That was a dandy.

If that piece you broke would have hit you instead of bouncing around the shop, you would not be make this inquiry. Be curious, learn, have fun. BE SAFE PLEASE
 
I'll add that sticking it in a vise and hitting it with big hammer isn't the safest way either.

Clamp the test sample in a strong vise or between the press dies. Stick a 4 foot piece of pipe over the part sticking out ( a piece of 1" pipe with the end flattened works good). Bend the sample until it breaks, keeping in mind that your body may move rapidly when the piece breaks.( try not to fall down on some sharp things or bash your skull on the press ram)

Stacy
 
For another idea on the velocities and dangers of shattering tool steel. I was using a large mag drill on a large beam. The 7/8" hogan bit (kind of a hole saw for metal that is faster than a regular drill) hit a slag inclusion in the beam. The sudden stalling of the bit ripped the magnet loose of the beam and the drill struck me in the arm so hard I actually had blood weeping out the skin of my arm (major bruise). The bit also shattered. I was wearing leather gloves. The base of my ring finger on my right had was also bleeding from a small cut. I healed up. But, years later I was entertaining my grandkids with a ball shaped rare earth magnet and had stuck another small disk shaped one under my ring. I would move my hand over the ball and it would follow my hand. They were amazed. But, my finger started to hurt. When I moved the magnet under my ring, my skin bulged out. I kept messing with it and a point of steel poked out of my skin. I ended up taking out a jagged piece about the size of a BB. I am sure it was from the drill. Stuff like that is why guys like me are totally X-rayed before they ever MRI us. All this is another reason to ALWAYS wear safety glasses. BE careful.
 
well i'm back. i am getting some weird results. this time i did a plate quench with no forced air and a oil quench that was swished around very quickly. so i did 4 chuncks. i tested each bar 4 time, two on one end and 2 on the other. that is why there is 2 numbers for each bar. i did not want my tongs to affect the result of the tests so i measured both ends. Thy where heat treated at 1510-1520 and soaked for 15 min at temp.

1- oil #1 55rc and 56rc
2- oil #2 55rc and 55rc
3- plate #1 53rc and 54rc
4- plate #2 54rc and 55rc

so i am onley getting 55.25 for the oil and 54 for the plate quench. something seams off to me or this is not L6 like i thought. could be maybe S7 but When i got it it was labled L6. but hay i guess never take a label for granted.

so now i need to get my bearings on things. I am going to do the test over but use some L6 i just got from crucible that i know is L6 and i have the certs on it. I will be back soon with the results.
 
it does sound funny... like Stacy says...theres lots of room in the L6 recipe to wiggle..

http://www.crucibleservice.com/eselector/prodbyapp/tooldie/champloy.html

myself ..i also use only champaloy for crucible for L6.... it does scale and it sticks to it like glue... usually use acid to take it off..

and it alway hardens.. .. to the point of being a nuisance when you go to drill it... so i'm starting to doubt that you have crucible stuff .... .. if you have a little coupon left... you could try water quenching and see if it lives... just out of curiosity..

G
 
so i just tested the L6 i got from crucible and the plate quench gave me 62.5 and the oil quench gave me 64+. so my process of heat treating L6 seams to be ok so now I realy dont know what i got. i also noticed that the mistery stuff has like 10 times more scale then the L6 i just did. but when i quench it it all comes off and leaves a clean surface. I just water quenched a chunk in ice cold tap water and i did not crack so now its on to the surface grinder to get a clean decarb surface to test. will be right back
 
Ok so i tested the water quenched chunk and it came out at 59-60hrc. hu weird. maybe i should start collecting betts and then go in and have it tested and see who wins. all i know is at 55-57 hrc it is amazingly tough. i did another break test and i ground a notch half way through it on the back side so it was thiner. the break point was a little thicker then 1/8th of an inch thick and about 7/8th wide. i maxed out our 20ton press trying to get it to break. i finley broke it but i had to use both hands on the pump handle and realy give it what for. i wraped the steel in a shop towel befor i broke it so nothing went flying. any ideas anyone, i can send a chunk to some one that might be able to tell me more.
 
O and remember the break test was on a chunk of steel that just came out of the quench tank and had not even been tempered yet so i can just image how much tougher it would be after tempering. now what if this is one of those steels that needs to get a little hotter then 1525. Maybe i will try forging a hawk out of it and see how it fairs. really i should just get it tested but its quite fun trying to figure out what it is, I mean i really cant think of a steel that can take any quench technique you can throw at it and still give you close to equal hardness values. It's just funny that you can get 55hrc with plate quenching it slow or throw it into ice cold water and get 59hrc. and all this with out any cracks or funky distortion at all. hu maybe i will sleep on it and see what i come up with.
 
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interesting stuff..

did you try to spark test it beside the champaloy.. i'm sure the carb difference is noticeable.. ..i bet the champaloy shoots shorter and puffier sparks..
- but is the color of the sparks the same...

sometimes color of sparks is easily seen between alloys... eg... O1 does have a unique color compared to W1 for example

what about one of the S-series of steel .. i thought they also scaled abit.. and are known for toughness

the thing about the L6 steel...is that darn scale sticks like glue... from what i remember it wouldn't just pop off in the quench... so that has me thinking that it maybe something else..... most of the time i have to use a side body grinder to get the scale off...

its cool that your doing this tests to figure it out... and i was surprised it survived the water quench... that is very interesting
 
Being that it didn't crack and is still incredibly tough after quenching, is it hardening right through?
 
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