Heat Treat

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Not exactly welding. When working with circuits I built and a program I wrote to read EGT's, I thought it would be easy to adapt it to operate a kiln. In doing so I thought I would play with heat treating; drill bits, lathe tools, spindles for cars, etc. This winter would be a good time for me to work on the program and such.One thing I know about heat treating is there is a lot more then just heating the part to cherry red then dropping it oil. With a computer controlled Kiln I could really control what I do. Do you know of any good books which discuss the art of heat treating? Something I can sit down and read on during the holidays...
Reply:I don't have any books but I built two ovens for work. Once big enough to park two tractor trailers inside of.  I like your little setup.
Reply:That kiln in the photo is actually an automated kiln my wife uses for ceramics. That one I test my egt's in but i don't want to use that one for tooling. She has a couple smaller kilns which would be perfect for me. I can dedicate them for tooling and I don't have to worry if I am going to mess them up for her ceramics. The circuit in the photo does a dozen different things. The circuit I would set up for the kiln would be much simpler and dedicated just for that use.
Reply:Try the free pdf to get you going with metalurgy and heat treating (nifty text book written and placed in the public domain by a professor at the university of Iowa), link here; http://www.feine-klingen.de/PDFs/verhoeven.pdfThe "Heat Treaters Guide" is available from ASM (and I'm pretty sure AWS now).Anyway, save it to your desktop and have a go at it.Matt
Reply:Go to the Admiral Steel web page. They provide heat treat specifications for several types of steel (the ones they sell).Knife supply houses also provide heat treating information on a lot of different steels. Just search  "Knife Supplies" for several of them.
Reply:Thanks guys!
Reply:It depends on the heat treating that you're trying to do.  For hardening, Machinery's Handbook.  For stress relieving of welds, ASME Section VIII Division 1 UCS-56.  I would be happy to provide you info from either of those sources if you let me know what you need.
Reply:http://www.mcmaster.com/#is a good source for steel and info.You can choose a steel that fits your equipment. Air hardening might be a good fit for your kiln. I like W1 which I can harden with a torch and a can of water.Lincoln SA200, HH135, Lencospot, HF80 Inverter, Rockwell 11x35 lathe, HF drill mill, Kama 554 tractor w/ FEL & BH, Belarus 250AS, lot's of Chinese tools
Reply:I did get a couple books to read over the holidays; thanks.Here is the project. I have a couple extra kilns so I wanted to use one for heat treating metal. I made a circuit where you put in max temp, slow or fast climb, and holding time (to hold at the temp). The circuit controls the kiln and gives you temp. The circuit is basically operational. I was going to use a servo to actuate kiln but I will probably get a 75a 240v solid state relay. I also have it set up to turn on a light when done but I just have to wire it in. I will build the control box out of aluminum and wire it up in January.
Reply:Wish I knew how to do that. I want to do the same thing for a heat treat oven.Unfortunately I will be stuck with a PID that I will have to adjust when needed as it does not have RAMP or SOAK capabilities.That will be pretty cool when it is working and doing what you want it to.
Reply:I that is something you want to do I am sure I could walk you through it (with some time). This was built from a processor known as an OOPIC but the same thing could be done with a basic stamp or an adruino. It would take a small understanding of electronics (not much) and a small understanding of programing) not as hard as it sounds).
Reply:I meant to say OOPIC no longer exist which is why it would have to be done with another board.
Reply:When working with circuits I built and a program I wrote to read EGT's, I thought it would be easy to adapt it to operate a kiln. In doing so I thought I would play with heat treating; drill bits, lathe tools, spindles for cars, etc. This winter would be a good time for me to work on the program and such.
Reply:Ive got a bunch of old temp and quench charts, if you need any specifics drop me a line.  I used to get stuck running an induction hardener fairly often.With regard to lathe tools, or any machine tools - almost all of them are roughed in, hardened THEN final ground for dimension.  Even car spindles/large tools may have enough distortion from heat treat, through hardening or even just surface hardening to tweak them out of tolerance, its a good idea to leave material in critical areas (threads, bores) to 'finish it to fit' .  Better quality steels will distort more consistently than lower grades.  Some of the recent Mexico recycled import steel is so NON-homogeneous that you can get more than .150 variance on a 1.0 through bore in a 2 inch plate.
Reply:Well, your hardening will be done by heating 'till cherry red or a specific temp if you want to be precice and them dumping the part in oil, water, or blowing cold air over the top depending on the properties of the material.  Where your computer controlled kiln will come in handy is stress relieving, normalizing, and tempering after a hardening process.
Reply:Originally Posted by SRO1911Ive got a bunch of old temp and quench charts, if you need any specifics drop me a line.  I used to get stuck running an induction hardener fairly often.With regard to lathe tools, or any machine tools - almost all of them are roughed in, hardened THEN final ground for dimension.  Even car spindles/large tools may have enough distortion from heat treat, through hardening or even just surface hardening to tweak them out of tolerance, its a good idea to leave material in critical areas (threads, bores) to 'finish it to fit' .  Better quality steels will distort more consistently than lower grades.  Some of the recent Mexico recycled import steel is so NON-homogeneous that you can get more than .150 variance on a 1.0 through bore in a 2 inch plate.
Reply:Originally Posted by 76GMC1500Well, your hardening will be done by heating 'till cherry red or a specific temp if you want to be precice and them dumping the part in oil, water, or blowing cold air over the top depending on the properties of the material.  Where your computer controlled kiln will come in handy is stress relieving, normalizing, and tempering after a hardening process.
Reply:I have a basic understanding of hardening and have been doing additional reading. It's not about the heating as much is about the cooling. The kiln works great for some one I work with but he opens the kiln and eye balls the color of the part before pulling it out and quenching it. He can control over all temps easier then with a torch which has caused him warping problems in the past. There is a lot to it depending on what you are doing which is obvious.The kiln works fine but the key key is the type of quenching and it really depends on what you are working with. Quenching with water it appears can quench it too fast making it brittle, where oil can some times be too slow for some parts. Settling on a brine or salt mix, oil, etc.The science of it all is quite deep; deeper then I can grasp as of yet; weather it is heated and quenched enough to bring it into the bainite or martensite phase, etc. On top of this is the decarbonizing of the metal, etc. There are a dozen ways of testing hardness from a Rockwell hardness test, penetration test,  tensile, Youngs model of elasticity, impact, and on and on....The advantage of the kiln is I can control the heating temps to ensure I have a level heat saturation and starting point for repeatable test. It brings one constant to the mix.I am going to be laser cutting some wrenches and I am going to run some test on some metal samples first from. The question is for me a guy in a garage to create samples, controls and test in a way which is repeatable and means something. It should be fun.In the mean time, I did get the circuit built. I also have (not shown) a 240v 50a dpst relay. All I need to do is build a control box and wire it up. With it I can control climb rate, max temp and holding temp. It will light up the LED lights when done.
Reply:When you are heat treating steel you first need to determine the requirements for that steel. All steels require different treatment. I heat treat knives on a regular basis and it is a little more involved than heating to cherry red and dumping in oil.When you heat the steel you are doing it for a reason, you are trying to converting the properties in the steel from one property to another. For 1095 and 1084 and similar high carbon steels this happens when the steel becomes non-magnetic. You can't accurately do this by color unless you do it in the same light all the time and practice until you get it right. Any light changes and your colors look different, making this method a guess at best.Heat until the steel becomes non-magnetic and them quench rapidly in the correct quench medium. Some steel want water like W-2, the W means water or O-1, the O means oil.Oil must be heated before using as a quench. When you take an extremely hot piece of steel and dump it in cold oil the oil will boil around the steel and this creates a vapor barrier that holds the oil back from touching the steel, this slows the quenching. You heat the oil to 125 degrees and the vapor barrier is almost non existent and the quench is faster. Faster equals more complete transformation.Then you temper to get your desired hardness. This can be accomplished by trial and error or following the specs given by the steel manufacturer.Unless you heat treat in an inert environment you will get some scaling. You must remove the scale prior to fit up of the part as the scale changes the finished size. For small parts this can be catastrophic but for large parts you can leave a bit as suggested earlier and finish after heat treatment, just keep all future process from heating the material above the tempering temps.How you quench is important to avoid warping. For example, a knife should not be laid sideways in the top of the oil and released. The one side will quench a little before the other and warp the blade. However, adding the blade quickly tip first and quickly plunging all the way in will usually avoid warping. I would never just throw it in the oil. It can harden and break when it hits the bottom of the container if it is thin like knife blades.If you use an oven that does not use an inert atmosphere, you must create one by using heat treating foil to contain your part and keep it from oxygen during heating.Research the steel you plan to use and get to know it well and treat it as suggested by the manufacturer and experiment from that baseline to get what you want.
Reply:That coincides with what I have been reading. I am sure I will have more questions but it's really time for me to get it going to play with it.I do have one question though. In lew of wrapping the material to keep it from loosing its carbon content, it mentioned several things burned to heat the part. Burning ovens using different things which provide carbon monoxide to bring the carbon content back up (primarily for tool steels). Obviously you don't have anything burning in an electric oven but....it made me wonder...could you run a small gas engine and pipe the exhaust through the kiln? Just a thought.
Reply:You won't be loosing much carbon content so I would not worry about it. I heat treat knives in a forge all the time and they perform very well. In lew of foil you could pump in argon. Just blast it at first and then trickle the rest of the time.
Reply:That's a good idea.
Reply:How much is the carbon an issue for things other then tool steels?
Reply:For most tings you will not have to worry about it. Just heat treat as directed by the steel manufacturer and you will be good to go.
Reply:Originally Posted by johnbeanHeat treatment is a method used to alter the physical and sometimes chemical material. The most common application is metallurgical. Heat treatments are also used for the manufacture of many other materials such as glass. Heat treatment involves the use of heating or cooling, normally to extreme temperatures, to achieve a desired result as hardening or softening of a material.I'm just curious if you looked at or bought any blacksmith books.  I read one off and on that I really enjoy.  It does describe the process quite well, as heat treating, annealing, and so forth are all so old.  There's a place near me that puts on blacksmithing classes, I need to go to one sometime.  This sounds like a very cool project and you sound like you know what you are doing.  Keep us postedCheers,
Reply:Yea, That's kind of what started the thread. I was looking for some good books to read over the holidays. I got one book before I left which was real good "Introduction to Metallurgy" which was a bit over my head but very informative. It gives me a place to start. In the mail today I got "Heat Treatment, selection and application of tool steels". I am looking forward to this one because it looks like I won't need a PHD to understand it. The topix already look familiar from the other book.You may not hear about it from me for a while. Right now I have a 100 things going on but I need to "Tap" into the kiln. It will be a project for mid January. The books are a good resource for coming up with a plan of action for what projects I take on.I also have some stuff for plating including liquid heaters which will work well for heating the oils or salt baths.
Reply:Be careful with the salts. Make sure you know how they work as a lot of people have hurt themselves by not starting heating them correctly.
Reply:Originally Posted by Bob WarnerBe careful with the salts. Make sure you know how they work as a lot of people have hurt themselves by not starting heating them correctly.
Reply:Kiln works up to a little over 2000 degrees!
Reply:Why did you put the thermocouple on a kiln that already displays the temperature?  Testing the thermocouple?
Reply:You mean the kiln in the first post? Yes rough calibration. I have a ball park place to start on temps. I can fine tune it with the cones used for ceramics. I can run the kiln and check how the cones melt. I can't use the nice kiln for several reasons. Even though it is automated, it is automated for ceramics. I really have no other programing functions. Second, once used for metal or powdercoating the wife can never use it for ceramics again.We had a couple older kilns she does not use any more hence the project. I am going to let her fire some ceramics before I use metal or powdercoating to see if this is a viable option for her with one of the smaller kilns.Last edited by gow589; 02-04-2011 at 07:45 PM.