by salzi684 » 13 Feb 2004 18:27
Pick-It hit this one right on the head. When you heat steals to high temperatures and quench them quickly like that you are creating a phase of steal call martensite. Although martensite is very hard it is also so brittle that it is pratically worthless.
Side note on the anealing process. By heating the material to a certain temperature and holding it there for a couple of hours you are doing a few things things.
1st the heat allows the carbon in a hardened steal to diffuse throught the material and possibly into the surrounding enviroment. Im not sure what sort of processing is done on hacksaw blades, but I would imagine that they are case hardened. If this is the case, trying to temper this material would be a bad idea. When the carbon is only in the outermost layer of steel it acts sort of like a surface finish. It creates a shell that is very hard over the surface of the softer inner steel and allows the material to reamin flexible without the wear that would occur with plain un-hardened steel. If this material was heat treated the carbon would reach the inner steal, making the whole part more brittle.
If you were working with a steel that was not hardened the annealing process would make the material more flexible, but only if the material had been some how worked (think bending back in forth). The anealing process would allow the crystals to grow in size, making the material more flexible.
If someone is at all interested in this I would recomend getting a book on material science. I find the subject very interesting and at the basic levels that would be discussed in most books it isn't that hard of a subjet to teach yourself, allthough previous knowledge in chemisty, physics, and calculus definatly help.