Steve Sells

Heat treat information

18 posts in this topic

Links to the pinned Heat treat information, While writted for the thin sections of blades. ithese will get you a long way to the HT of your other projects as well.

 

Introduction to heat treating     http://www.iforgeiro...-heat-treating/

Advanced heat treating            http://www.iforgeiro...-heat-treating/

Advanced methods of annealing  http://www.iforgeiro...ealing-methods/

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Thank you for taking the time and posting the above articles very informative just what need .

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These are a wonderful read and quite informational for a new smith like myself. Thanks again!

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I was reading over Steve Sells intro to heat treating thread since I am doing research for a project on tempering for a science fair at our school. I am trying to understand if steel is really made of individual cubes? Steve says "At room temperature steel is in a body centered cubic structure. The cubes of steel have an atom at each of the 8 corners of the cube, and one [would this be a carbon atom or steel atom?] in the center of the box." So what I am wondering is, is steel kind of like Styrofoam, made up of little balls?

Another question is, before steel is heated, in its ferrite form, there is only one carbon atom present? and then at the curie temperature, 5 more carbon atoms suddenly appear and attach themselves to the faces of the steel cube? Where does that carbon come from? Perhaps there are some scientists here that wouldn't mind just looking at my questions a bit?.... Thank you.

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Think you need to do some more research on the molecular structure of steel in its varied forms.  This is a complicated subject, and I'm not the right person to explain it, but the various alloys of steel (typically comprised of an alloy of iron and carbon atoms with the addition of various other trace alloys depending on the particular steel material makeup) form a crystalline matrix that exhibits different properties depending on how those iron and carbon atoms are arraigned. The general layout of the carbon and  iron atoms in the overall matrix can vary depending on the percentage of carbon in the mix (i.e. low carbon steel, containing carbon up to around 0.25%, and high carbon steel, with carbon percentages between around 0.55 and 0.95%) and the heat treatment process that the material is exposed to.  This layout has a large effect on the properties of the steel, including working and melting temperatures, hardness, strength, flexibility, etc.  The tempering you reference is only one small part of the heat treatment process.

Suggest you do some reading up on metallurgy at your local library.  While anything you read online should be carefully vetted before being taken as gospel (including this post), the accepted print references in the library are typically more reliable.  A local engineering school will have years of reading matter on this fascinating topic.

BTW, if you are identifying these "little balls" as atoms, then yes, steel is made up of little balls... as is arguably everything else we experience in the physical world.

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In my book I even have pictures and drawings , I explained  that a body centered cubic is ferrite. with iron on the corners and carbon in the center.  Austenite is a face centered cube of iron, and the hardened form is in pyramids called martensite. with 4 iron atoms and one carbon in the center.

I posted the threads on heat treating to assist in showing people how steel changes at temperature, and why some times things do not harden.  Physics states if there is not enough carbon present, as in mild steel, to form martensite in an appreciable amount of the steel matrix, then no amount of super quench can change that, simpler to use correct steel for the application. or case hardening is also an option, to providing the necessary carbon for the conversion.

no single book or website is going to give us a full knowledge of metallurgy, that is why there are multi year university classes for that level of information.

 

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How atoms and molecules are constructed is not a metallurgy thing but more an atomic physics thing, *and* most of the "shortcuts" we use to think about things are just that and don't hold true the deeper you go into a structure---like atoms are not balls, they are mainly empty space and the location of electrons is statistical rather than deterministic.

However if you were making a model you would use differing coloured balls of clay and toothpicks to show the different phases of iron.  I teach my bladesmithing students to think of it as low temp, BCC---place my hands on my belly and then as you raise the temp it transforms into FCC raising my hands to my face.   Deformation---correlated to hardness is caused by rafts of atoms sliding over one another.  Carbon getting "stuck" in a place it doesn't fit well by quenching makes for "speed bumps" making it harder for the rafts to slip over one another.  And all this is true and all this is false depending on how deeply you get into the subject...

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thank you for taking the time to reply. I'm not sure that I still understand this, but I will continue researching. Thomas, I really like your idea of the clay and toothpicks for models.

10 hours ago, tonyw said:

So what I am wondering is, is steel kind of like Styrofoam, made up of little balls?

8 hours ago, latticino said:

BTW, if you are identifying these "little balls" as atoms, then yes, steel is made up of little balls...

 

Well, I meant to say that steel, which appears to be solid, is made of cubic structures just like Styrofoam is made of little balls pressed together. Is that a correct analogy?

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Well it's a bit more complex: steel is composed of crystals, AKA "grains",  that are composed of atoms arranged in structures dependent on the phase of the steel and composition.

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Oh, so I am missing a step. In order of size: atoms, structures, and then steel crystals or grains.

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Have you accessed a good encyclopedia yet?   Trying to get this off the net is NOT the way to go about it! Especially from someone who took their MatSci classes back in the late 1970's...Might be able to get one of my students in the UTEP metallurgy program to pinch hit for me; I see him Saturday when he comes over to forge.

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Tony,

All matter in the forms you are used to is mostly empty space. Styrofoam is macroscopically empty. Iron crystals are not. You can't fit air into those empty spaces. Air is much too big. It's sub-atomically empty, not macroscopically empty.

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I must admit, I feel more confused than ever, I'm sure it's my fault. I'm sorry you have to deal with my thick-headedness. I bet its frustrating. I'll study this some more; if it's possible, I would like to develop a simple and general sort of explanation of the structure of steel that anybody can understand, which has got to start with me understanding it first. The best way to really learn something is to teach it to others. I'll try to post what I think I understand once I really get it... Thanks for being patient!

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Think of this as being like looking at something; what you see with your eyes is real, but it differs from what you see with a microscope, which differs from what you see with an scanning electron microscope, X rays, micro probe, etc  You pretty much have to chose what level of detail you are going to teach at:  clay ball models of atoms and molecules and bubble rafts to model dislocations and movements are fairly general.  When you start mentioning Heisenberg and strong vs weak forces you are in deep even if the description is charming---or anti charming...  Throw in magnetic domains to muddy things further...

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Here I am again. I said I would post what I understood once I really got it. I was trying to do this research for a science fair project. At the fair I demonstrated how to temper steel. I showed people that I could snap a quenched piece of 1/4" spring steel by hand, and they saw that I couldn't break it after I had tempered it to a blue, but I don't think they really got the exact science behind it, which was fine, I guess. I had a poster board with my understanding of basic metallurgy, which honestly, I barely got it myself. I thought I would put a couple pictures of my poster board, and if you feel like reading it, you can tell me what I got right and what I got wrong. And thanks to Thomas' suggestion, I did make some clay models. I think I learned a lot. The hard part was fitting an entire field of science on one little poster board, and then being able to explain what I put up there....

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Thanks for showing us the results!   Hopefully you will continue to learn about it and maybe even think of getting a degree in it someday.

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Here's some useful charts from the war departments technical manual from 1942. Obtained a copy from a friend of a WWII veteran that it was issued to I believe. 

 

Hope this helps someone in a least a little way!

 

Brent  

 

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