Forging and Forming

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Forging and Forming

مُساهمة من طرف Argon في الأحد مارس 30, 2008 6:43 pm

6.0 Forging and Forming

6.1 Cold Forming

Cold forming consists of drawing, extruding or otherwise shaping of metal at or just above room temperatures. Just plain beating the hell out of metal with a hand sledge is a form of cold forming. This process greatly increases the hardness, tensile strength and yield strength. It also increases the brittleness of the part. This is true for almost any metal alloy.

6.2 Hot Forming

Hot forming usually refers to the forging process. "Working" the metal while its hot is much easier than cold working but does not do as much work hardening to the piece.

Hot working can be defined as: plastically deforming a metal above the re-crystallization temperature. For steel, this temperature is the austenite formation temperature. To hot work a metal, you first heat the metal well above the austenite temperature. 300 to 400º F over is common. This allows plenty of time for you to form the piece while its austenite. Here is where we can do some "blacksmithing" at home. The process is basically simple. Heat the part above the austenite transformation temperature then beat the hell out of it. You will be able to "feel" if its getting to cold. As the part cools back through the austenite temperature and starts to form pearlite it will become stiffer. Just stick it back in the fire and heat it back up.

Another way to tell that it's too cold is by its Curie point. The Curie point is the temperature where a magnetic alloy becomes non-magnetic or visa-versa. For low-alloy steel, the curie point is 1414º F. A quick touch with a magnet will tell you if you are over the curie point. Typically, you should stay over 1500º F. Of course, there is the color vs temperature method to determine its temperature. Once the part is the shape you want, you can let it cool on its own to form a normalized structure or you can quench it to harden it by forming martensite. Don't forget to temper it.
When you are done, you will have a decarburized layer. The best method for removing this layer is with a file. You will know when you have removed it when the file doesn't remove as much as easily. The decarburized layer is all ferrite. Ferrite is much softer than tempered martensite. I have done this at home with small parts using a torch. If the grade of steel is not very harden able, you will need to quench it in brine (10 percent salt water). If its very hardenable, brine will crack it. Use an oil for these steels. As with any quenching operation, agitation accelerates the quenching operation. I have never done large parts at home. You would need a large hot fire. I would suggest reading a blacksmithing FAQ. However all of the metallurgy remains the same.

Argon
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تاريخ التسجيل : 07/09/2007

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رد: Forging and Forming

مُساهمة من طرف ENG_3ALIM في الإثنين مارس 31, 2008 11:48 pm

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ENG_3ALIM
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تاريخ التسجيل : 08/03/2008

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