which oil for 1095

[Chris Daigle]

And as to the short quench times, I'm not sure how other makers do it, but my method is fairly quick. It helps if you have a small setup like my own.

One of my quench "tanks" is a metal container with lid that is normally meant as a pasta container (OK, you all can call me a yuppie forger...go ahead ). But it has a few really good features. One, it's light enough and has the lid so that you can transport it out of the way when not in use. You can also hang a thermometer off the side to make sure the oil is heated up.

Being able to place it right under the forge makes for a quick dunk. This only applies for a full quench, and the size of the container will only accomodate up to a 7" blade, but it's worked well for me in the past.

Chris

[J.Arthur Loose]

When folks say that you have to quench in under 1 second it doesn't mean from the fire to the quench, it usually means from the time the blade hits the quench... unless you're *really slow* going from the fire into the quench. Take a blade out of the fire and watch for the shadows to start forming... that's how long you have to get it into the quench; probably a couple seconds, which is way better than .6!

Just wanted to put that out there since it confused me when I first started...

[paul harm]

over on don foggs forums a well known " expert" on heat treating suggested not going quite so high before you quench . if the steel is 25 degrees less hot , that's 25 deg. less to take it down to miss the nose . he went on to say , most people try a higher temp to get a good hardness , when actually the oppisite is true . i'm with mr. loose on the time it takes - i don't believe you're loosing more than a couple of degrees going from the forge to the oil , it's still at austinite temps , it's how fast your quenchent will take it down . just my 2 cents worth . paul

[SteveS]

Paul,

I might be way off here, but I've always believed just the opposite. The .6 seconds refers to how fast you have to get it from above critical to below the 'nose'.

The higher the temperature the more time you have. (Of course there are undesireable effects from too high, but I'm just refering to the martensite creation).

So, it isn't that you have less than a second to go from ANY temperature to below 500 degrees. It's how fast you get it from austentite temp to martensite temp.

Or am I out of wack here.

Steve

[paul harm]

the way it was explained was ; lets say critical temp is 1500 , and you'te trying to get to your number , 500 - it's easier to do than if you were at 1525 , or 1550 because there's 25 or 50 less degrees to cool down . i probably didn't explain it very well - it was more of a discussion on people having trouble getting the steel hard , and they were heating the blade hotter , making it just that much harder to miss the nose of the curve . a lot of people use thier forge and a magnet , and let the temp rise just a bit above non- magnetic , when they may be better off not alowing it to rise above non-magnetic . it was just a sugestion for people having trouble , and it makes sense . paul

[SteveS]

Paul, I don't even want to sound argumentitive so please don't mis-read me I'm trying to understand.

It seems to me that the issue is getting from (let's just use your numbers it's easier that way) 1525 to 500. If the blade is right at 1525 when it comes out of the 'oven' you don't have any time to hit the quench because if it takes a second to get to the quench you are already hitting the nose and air won't cool fast enough.

However if you are at 1600 (let's say) you have more time. Because the steel can drop to 1525 before you hit the quenchant. Then the quenchant can get you below the nose.

Or am I still confused (quite likely!)

Steve

[paul harm]

do i don't think you're argumentitive - it's a good discussion . let's do this - is it quicker to cool something from 2000 to 500 or from 1500 to 500 ? i would have to think it would be easier and quicker to cool it from 1500 . the same applies from 1550 /1500 to 500 . you're gonna get it down to 500 quicker if you start from a lower temp . by the way , it was howard clark who suggested this idea . maybe mr. loose would give his thoughts again ? maybe i didn't interpret howards thread properly - but that's how i remember it . paul

[paul harm]

after sitting here , thinking of the question from your side , i can see what you're saying . i guess what the question is - what is the temp drop from fire to quench ? if it's not dropping below austentite, then it's easier from a lower temp . if you are dropping below austentite, how much time was used ; that would be added to the total time . how would one measure the temp drop just before it hits the quench ? i've used files many times for knives with no problems , and just used a magnet , so i can't really say if going to a higher or lower temp is necessary . i was just stating what someone else said [ and i hope i quoted him right ] . i would think the carbon content from a file is at least as high as 1095 , and don't think it is possible to do it in .6 sec. how then does one explain them getting hard? maybe we have more time than the book says ? paul

[SteveS]

Paul,

I think we're getting the questions refined enough to answer. First I want to clarify my understanding that steel is austentite above a certain temperature (depending on alloys). Say the As temp is 1475, then it's austentite at 1475 and 1500 and 1600. So, given that let me take a crack at asking the question:

When creating martensite and considering the time factor, how do you measure the time? Is it the time spent getting the steel from the temp in the forge to below the 'nose'? Or is it the time to get it from austentite to below the nose?

I think that's the question we're trying to get answered.

Steve

[mete]

These kinds of threads are confusing ,vegetable oil, pasta containers ? Is this a cooking show ? .....Remember that the TTT diagrams are done with one specific chemistry under specific laboratory conditions. The transformation starts when you get below the transformation temperature ,at that point it takes about 1/2 second to start to transform to pearlite .That's not impossible especially with blades which are thin. After all it's done all the time . If you have problems look to your technique. Furnace temp - can you measure temps and control them accurately ? The better you can control temp and time [soak time ] the better off you are . Do you take out the blade and look at it and then check with a magnet ?Then you've lost too much time. [after magnet put it back in to make sure you're back to temp.]Do you have to walk to the quench ? then you've lost too much time. Water quench should work as should something like AAA since that is designed to bring the temp down quickly past the pearite region then slower through the martensite region...To answer Steve - when you go below the tranformation temp then the clock starts. Curie temp is 1414F [ magnetic temp] There is the often quoted Ac1 [on heating]but there is also Af1 [on cooling ,which is lower than the Ac1], and the specifics of chemistry etc . So don't get lost in all the theory ,refine you procedures and it should come out hard !

[paul harm]

mete - thank you - paul

[SteveS]

Originally Posted by mete

when you go below the tranformation temp then the clock starts.

OK so raising the temperature in the forge actually helps give you more time to get into the quench. IOW, if I have a blade at 1500 and go to the quenchant, I have to get sooner than if the blade is at 1550.

Steve

[paul harm]

try it and find out . let us know how it works out . paul

[J.Arthur Loose]

Originally Posted by SteveS

OK so raising the temperature in the forge actually helps give you more time to get into the quench. IOW, if I have a blade at 1500 and go to the quenchant, I have to get sooner than if the blade is at 1550.

Steve

What I was trying to say earlier is that the temperature drop of a blade in the air, as it is removed from the fire, happens a little slower than a lot of people think; otherwise we wouldn't need to quench at all. You've got two or three seconds in most cases before a blade in the air gets below critical. You can also see the transformation itself by looking for the shadows... in other words, if the edge looks dark before you get to the quench you've taken too long. I actually practiced this for a while with a thermocouple in my forge, just heating a blade right to the austenitic & watching it cool. I learned that it is better to be smooth and get the blade into the oil accurately than it was to stress and try to go as quick as possible.

[SteveS]

Thanks loads J.

I like the idea of watching for the shadows on the edge. I'm gonna practice that. I have been using the oven for the hardening process, because I couldn't get a consistent result from the forge. Funny, I've played with watching the shadows on the upswing .....


Steve