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Steel MakingSteel Before The 1850'sIn spite of a rapid increase in the use of machines and the ... Heat Treatment Of Steel Heat treatment consists in heating and cooling metal at defin... Tungsten Tungsten, as an alloy in steel, has been known and used for a... Bessemer Process The bessemer process consists of charging molten pig iron int... The Leeds And Northrup Potentiometer System The potentiometer pyrometer system is both flexible and subst... Ebbw Vale And The Bessemer Process After his British Association address in August 1856, Besseme... Effect Of Different Carburizing Material [Illustrations: FIGS. 33 to 37.] Each of these different p... Carbon Tool Steel Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham... Placing The Thermo-couples The following illustrations from the Taylor Instrument Compan... Cutting-off Steel From Bar To cut a piece from an annealed bar, cut off with a hack saw,... Annealing Method Forgings which are too hard to machine are put in pots with ... Phosphorus PHOSPHORUS is an element (symbol P) which enters the metal fr... Flange Shields For Furnaces Such portable flame shields as the one illustrated in Fig. 1... Compensating Leads By the use of compensating leads, formed of the same materia... Gas Consumption For Carburizing Although the advantages offered by the gas-fired furnace for ... Lathe And Planer Tools FORGING.--Gently warm the steel to remove any chill, is parti... Plant For Forging Rifle Barrels The forging of rifle barrels in large quantities and heat-tre... Crankshaft The crankshaft was the most highly stressed part of the entir... Classifications Of Steel Among makers and sellers, carbon tool-steels are classed by g... Piston Pin The piston pin on an aviation engine must possess maximum res... |
The Pyrometer And Its UseCategory: PYROMETRY AND PYROMETERS In the heat treatment of steel, it has become absolutely necessary that a measuring instrument be used which will give the operator an exact reading of heat in furnace. There are a number of instruments and devices manufactured for this purpose but any instrument that will not give a direct reading without any guess work should have no place in the heat-treating department. A pyrometer installation is very simple and any of the leading makers will furnish diagrams for the correct wiring and give detailed information as to the proper care of, and how best to use their particular instrument. There are certain general principles, however, that must be observed by the operators and it cannot be too strongly impressed upon them that the human factor involved is always the deciding factor in the heat treatment of steel. A pyrometer is merely an aid in the performance of doing good work, and when carefully observed will help in giving a uniformity of product and act as a check on careless operators. The operator must bear in mind that although the reading on the pyrometer scale gives a measure of the temperature where the junction of the two metals is located, it will not give the temperature at the center of work in the furnace, unless by previous tests, the heat for penetrating a certain bulk of material has been decided on, and the time necessary for such penetration is known. Each analysis of plain carbon or alloy steel is a problem in itself. Its critical temperatures will be located at slightly different heats than for a steel which has a different proportion of alloying elements. Furthermore, it takes time for metal to acquire the heat of the furnace. Even the outer surface lags behind the temperature of the furnace somewhat, and the center of the piece of steel lags still further. It is apparent, therefore, that temperature, although important, does not tell the whole story in heat treatment. Time is also a factor. Time at temperature is also of great importance because it takes time, after the temperature has been reached, for the various internal changes to take place. Hence the necessity for soaking, when annealing or normalizing. Therefore, a clock is as necessary to the proper pyrometer equipment as the pyrometer itself. For the purpose of general work where a wide range of steels or a variable treatment is called for, it becomes necessary to have the pyrometer calibrated constantly, and when no master instrument is kept for this purpose the following method can be used to give the desired results: Next: Calibration Of Pyrometer With Common Salt Previous: The Thermo-couple
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