| Although someone has submitted a lost and found spell (which they jacked from the TV show Charmed, at least with the rhyming part)... I would like to send in mine that I use. Although it was in part taken from Charmed, too, (yes I admit it) I hav... Read more of Lost and Found Spell at White Magic.ca |  Informational.caPrivacy |
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Temperatures To UseCategory: HARDENING CARBON STEEL FOR TOOLS As soon as the temperature of the steel reaches 100 deg.C. (212 deg.F.) the transformation begins, increasing in intensity as the temperature is raised, until finally when the lower critical range is reached, the steel has been all changed into the ordinary constituents of unhardened steels. If a piece of polished steel is heated in an ordinary furnace, a thin film of oxides will form on its surface. The colors of this film change with temperature, and so, in tempering, they are generally used as an indication of the temperature of the steel. The steel should have at least one polished face so that this film of oxides may be seen. An alternative method to the determination of temper by color is to temper by heating in an oil or salt bath. Oil baths can be used up to temperatures of 500 deg.F.; above this, fused-salt baths are required. The article to be tempered is put into the bath, brought up to and held at the required temperature for a certain length of time, and then cooled, either rapidly or slowly. This takes longer than the color method, but with low temperatures the results are more satisfactory, because the temperature of the bath can be controlled with a pyrometer. The tempering temperatures given in the following table are taken from a handbook issued by the Midvale Steel Company. TABLE 23.--TEMPERING TEMPERATURES FOR STEELS ---------------------------------------------------------------------------- Temperature Temperature for 1 hr. for 8 min. --------------- Color --------------- Uses Deg. F.Deg. C. Deg. F.Deg. C. ----------------------------------------------------------------------- 370 188 Faint yellow 460 238 Scrapers, brass-turning tools, reamers, taps, milling cutters, saw teeth. 390 199 Light straw 510 265 Twist drills, lathe tools, planer tools, finishing tools 410 210 Dark straw 560 293 Stone tools, hammer faces, chisels for hard work, boring cutters. 430 221 Brown 610 321 Trephining tools, stamps. 450 232 Purple 640 337 Cold chisels for ordinary work, carpenters' tools, picks, cold punches, shear blades, slicing tools, slotter tools. 490 254 Dark blue 660 343 Hot chisels, tools for hot work, springs. 510 265 Light blue 710 376 Springs, screw drivers. ---------------------------------------------------------------------------- It will be noted that two sets of temperatures are shown, one being specified for a time interval of 8 min. and the other for 1 hr. For the finest work the longer time is preferable, while for ordinary rough work 8 min. is sufficient, after the steel has reached the specified temperature. The rate of cooling after tempering seems to be immaterial, and the piece can be cooled at any rate, providing that in large pieces it is sufficiently slow to prevent strains. Next: Knowing What Takes Place Previous: The Theory Of Tempering
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