from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A nonmagnetic solid solution of ferric carbide or carbon in iron, used in making corrosion-resistant steel.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A solid solution or carbon or ferric carbide in iron that exists in steel at high temperatures
from the GNU version of the Collaborative International Dictionary of English
- n. a solid solution of ferric carbide or carbon in iron; -- it cools to form pearlite or martensite.
from The Century Dictionary and Cyclopedia
- n. A constituent of steel, obtained by quenching high carbon steel from a temperature of 1000° C. in a menstruum such as iced brine, which will produce very rapid cooling.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a solid solution of ferric carbide or carbon in iron; cools to form pearlite or martensite
He suggested to me a theoretical problem left over from his work during the war on the cooling of steel through the austenite-pearlite transition, and I learned a fair amount of metallurgy in order to understand the physical basis of the phenomenon.
In order to produce quick and intense carburization the iron should preferably be above its upper critical temperature or 1,600°F., -- therefore the carbon absorbed immediately goes into austenite, or solid solution.
There are several theories to explain this reaction, but generally it is only necessary to remember that in hardening we quench steel from the austenite phase, and, due to this rapid cooling, the normal change from austenite to the eutectoid composition does not have time to take place, and as a consequence the steel exists in a partially transformed, unstable and very hard condition at atmospheric temperatures.
The structure is then austenite and the air-cooled structure of this steel is martensite.
The growth is continually destroyed by the hammering, which should consequently be continued down to the upper critical temperature when the austenite crystals break up into ferrite and cementite.
Chromium steels are therefore capable of great hardness, due to the rapid cooling being able to retard the decomposition of the austenite.
If a piece of steel could be cooled instantly, doubtless austenite could be preserved and examined.
Higher percentages of nickel change the martensitic structure to austenite, the steel then being non-magnetic.
In the ordinary practice of hardening steels, the quenching is not so drastic, and the transformation of austenite back to ferrite and cementite is more or less completely effected, giving rise to certain transitory forms which are known as "martensite," "troostite," "sorbite," and finally, pearlite.
However, if the heating has gone above the critical very far, the austenite crystals start to grow; a very short time at an extreme temperature will cause
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