PDA

View Full Version : HT



cnilson
02-20-2010, 12:45 AM
Can I heat treat 1095 with a torch and get a good do on it? Can you quench in warmed 10-30 oil? I know these might be dumb questions, but I am pretty new to all this. Thank you:)

silver_pilate
02-20-2010, 01:33 AM
You may be able to do the heating with a torch, but motor oil isn't going to cut it for a quench. 1095 does best with a very fast quench (formulated oil like Park's#50, brine, or water), but there's been good discussion about using canola oil on thinner blades with decent results. It may not get as hard as it could, but it can make a servicable knife if it's not too thick (I'd guess no more than 5/32" at the spine). So why canola instead of water? If you're new to this, I'd expect you may have some uneven stresses created by grinding. That's going to increase you chance of the blade cracking in a water quench. Plus, sometimes you have everything right, and it can still crack. To reduce the chances of that, normalize the blade by bringing it to non-magnetic and then letting it cool to room temperature in air.

The hardest thing about using a torch is acheiving a uniform temperature without overheating any part. And it's going to be a bit warmer than non-magnetic for 1095, and it could stand to stay at temp for a minute or two.

It's a good idea to spend time studying the details of heat treatment, as it is one of the most important factors in creating a quality knife. Each steel has its own "recipe" for successful hardening. There is no one-size-fits-all for heat treating.

--nathan

Doug Lester
02-20-2010, 03:34 PM
One question is what are you using for a torch. If you are using a simple propane torch, I'd say it is doubtful that you will be able to get a good heat on anything with an uncontained fire. An acetyline torch of a rose bud tip is a better tool. Another factor is the exact makeup of the 1095. Because steel is only recycled here in the US, from what I've been given to understand, the exact composition of the steel can vary. Steel with higher trace elliments in it than is normally found in "virgin" 1095 may make it easier to harden in a light oil.

Doug Lester

cnilson
02-20-2010, 03:48 PM
What I have is a large propane cutting torch. I heated the blade till it did not attract a magnet and then went straight to heated 10-30 oil. I do not have a hardness tester,but I tried a file on it and it seemed pretty hard. The file mostly just slid across.

LRB
02-20-2010, 04:36 PM
First, you do not quench at non-magnetic. You need around 75 more heat. Second, that file test will tell nothing as to 1095. I can guarantee you have a hardened pearlite and martensite mix that will not hold a good edge. The file will skip off steel in this condition just as it would full martensite. You might want to re-treat it using canola oil and more heat. Get it a couple of shades redder than non-magnetic, or it will not go into solution. Quenching at non-magnetic is one of those myths that just won't die. If it does not go into a good solution, you will not have a good dispersal of carbon, and if it does not cool fast enough, you will get hardened pearlite instead of martensite, as you now have. Canola oil is about the best you can do without buying real quench oil. Motor oil, as mentioned, is useless for a 1095 quench oil.

Scott Jones
02-20-2010, 05:22 PM
Yes...and have fun experimenting.

Doug Lester
02-21-2010, 01:44 PM
LRB, if you don't quench at non-magnetic what do you quench at? Even if you hold the steel in the forge to assure that all the carbon has gone in solution and there is enough extra heat to go from the forge to the quench tank and still have all the steel austinized, it is still non-magnetic. I have always read to heat the steel to non-magnetic and then soak for several seconds to gain more heat so maybe that myth of quenching at non-magnetic is more of a missunderstanding.

I also went back to my references and looked for hardened pearlite in the description of steel phases and couldn't find anything on it, not even in "Steel Metalurgy for the Non-metalurgist". As is known the differences in the physical structure of crystals causes a difference in the mechanical properties of steel. What is the difference in the physical structure between hardened pearlite and regular pearlite?

Doug Lester

silver_pilate
02-21-2010, 03:55 PM
I see your point, Doug, but I think it's just a semantics game. What Wick is trying to say is that too many people just go to non-magnetic and as soon as it's there, they quench. The problem is that steel will go non-magnetic at 1414F, and 1095 should be quenched from around 1500F. You are right in that both will be non-magnetic, but one will harden and one will not.

Also, not so speak for him, but I assume he's saying you'll have a "hardened" blade that is a mixture of pearlite and martensite that will not perform near as well as a hardened blade consisting entirely of martensite.

--nathan

Doug Lester
02-21-2010, 10:47 PM
What I'm saying is that I have never heard of hardened pearlite but maybe he knows something that I don't. Wouldn't be the first time. Just asking for an explanation of the term. Actually with quenching 1095, or most 10XX steels, you can end up with a mixture of martensite and pearlite or even martensite, pearlite, and bainite if you don't have a really agressive quenchant. Retained austinite is practically inevidable. It depends on how long the steel spends in each of these areas. This also depends on the level of manganese. One also has to keep in mind that with most of the steel that we have available is recycled and what we end up with is something close to 10XX steel and not classical 10XX. As an example, the last batch of 1084 that Aldo had made up/ran across had almost 30 points of silicon and above what I would consider a bit more than a trace of some other metals. I'm not dissing Aldo, this is what was available, but it does effect performance in heat treating. This probably has a lot to do with why different people have different results when it comes to heat treatment. They think that they are talking about the same steels when actually they are not.

Doug Lester

LRB
02-22-2010, 06:56 AM
Thankyou Nathan, that was my point. Hardened pearlite is just a simplistic descriptive term for a pearlite/martensite mix that allows a file to skip, giving those who don't know, the impression that everything went as it should, although the steel is acually in a poor condition as a blade. There may be much truth in what Doug said about the quality of available steel. Last year I had a piece of 01 that had a longitudinal band running the length of the blade, just about midway, that would not harden. I tried three times. The edge below the band was hard, and the spine and point were hard, but the band, about 3/8" wide, and seemingly uniform, never would harden. Oven heated, decarb protected, soaked, and quenched in Parks AAA.

Doug Lester
02-22-2010, 11:51 AM
Thanks for explaining what you mean by hardened pearlite, I guess that it's the technician in me that was put off by the term. I prefer to call it what it is. I think that we agree on middle ground. A non-magnetic state in the steel is required to harden steel but is not in and off itself an indicator that one has arrived at the proper temperature in the steel to go to the quench tank. So there really is no myth here.

On Ed Cafrey's site there was a man complaining that he just couldn't get a blade that was made of 5160 to harden. In the end it was felt that what he had been sold was probably structural steel and not the spring steel that he ordered.

Doug Lester

LRB
02-22-2010, 01:20 PM
To Mr. Lester. Yes there is. The myth involves quenching right at non-magnetic, 1414. This practice is even taught by some smiths. Bring the blade to non-magnetic then quench. I have seen these posts over and over. They will also often say, or imply that if you go much hotter you get too much grain growth. I don't know of any steel that will reach it's optimum at much below 1475. You can get 1080 hard slightly above 1414, but it will not be as good as it should be, and what did you not understand about non-magnetic when I followed that with, you need about 75 more heat before you quench?

Doug Lester
02-22-2010, 09:35 PM
Well, if you are seeing those recommendations then I would have to agree with you. Then again, I'd say that it's not so much a myth as lousy instructions. Anything that I have read by the likes of Ed Cafrey, Jim Hrisoulas and Wayne Goddard, have stated to heat to non-magnetic and then return to the forge a heat a little more. The steel must be fully austinized when it enters the quenchant or the temperature will pass into the pearlite or bainite area before it starts to form martensite. I understood you perfectly when you said that the steel needed to be around 75 degrees above the austinization point when quenched. My objection is that in your original post you simply stated that non-magnetic was a myth, as in untrue. It is true but, as we both agree, not suffecient in itself. There are a lot of extreem beginners who read these posts and they can really get thrown off by such statements. Statements like you made were really as bad as the ones that give poor instructions.

As far as people wetting themselves over grain growth, I couldn't agree more. One, it is correctable and, two it is preventable, to an extent. Grain growth is influenced much more by temperature than time. All one has to do is to turn the forge down. Steel can be soaked a lot longer at 1500 degrees than it can at 1800 degrees and at 2000 degrees you get in trouble pretty fast.

Doug Lester

LRB
02-23-2010, 05:56 AM
Although I admitedly may be poor at composing, I don't believe any "normal" person would have a problem understanding what I wrote. The guy that started this thread did exactly what I was talking about. He heated until the magnet would not stick, then immediately quenched, because he has either read somewhere, or been told by someone that, that is the proper way it's done. That is my final word on the matter. Have a good day sir.

Doug Lester
02-23-2010, 11:26 AM
Ok, truce.

Doug Lester