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Related to Decarburization: decarbonization



the reduction of the carbon concentration in steels and alloys that takes place upon heating in oxidizing media, as well as in hydrogen (dry or wet).

Decarburization of steel and alloys may produce both harmful and beneficial effects. Decarburization during heat treatment or during heating prior to rolling or forging extends into the interior of the metal to a depth that depends on the temperature and duration of heating, and it leads to degradation of surface properties in the finished articles and to rejects.

Decarburization is the result of various complex reactions: C + ½O2 = CO; C + O2 = CO2; C + CO2 = 2CO; C + H2O = CO + H2; C + 2H2 = CH4; C + FeO = CO + Fe. The reactions are initiated and proceed at appreciable rates at temperatures above 700°C. Decarburization may be eliminated by heating in furnaces with a protective atmosphere or under vacuum. Decarburization in open furnaces is minimized by reducing the residence time of metal at high temperatures (for example, in walking-beam furnaces) or by using rapid electrical contact heating of the metal. Decarburized layers formed during production may be removed mechanically (on grinding machines). Annealing of metal in reducing gas mixtures containing natural gas or other hydrocarbons is also used; this results in enrichment of the surface of articles with carbon (restorative carburizing).

As a type of chemical heat treatment, decarburization improves the properties of metals and alloys in which carbon is an undesirable impurity (transformer steel and stainless steels). Refining decarburization is achieved by heating in gaseous media of fixed composition, which is selected to prevent the base metal from participating in chemical reactions. Transformer steel is annealed in N2-H2-H2O mixtures. In this case, the ratio of the H2 concentration to the H2O concentration is such that the iron is not oxidized, whereas the carbon forms CO and is removed. Stainless steels and similar alloys, which contain readily oxidizable alloying elements, are subjected to refining annealing in dry hydrogen.



The loss of carbon at the surface of carbon steel when it is heated for processing or in modifying its mechanical properties.
References in periodicals archive ?
For example, after heat treating, parts can be checked for hardness, tensile strength, and many other cracks, decarburization, and many other factors which might be affected by the treatment.
It is stated conclusively that sintering under this mechanisms occurs without demanganisation and decarburization of the compacts in the atmosphere with the low dew point contrary to that with a high dew point adversely affecting the sintering and alloying process.
The paper also reviews the causes of decarburization and the dynamics of measuring atmosphere carbon potential.
The heating technology was designed such that scaling and surface decarburization are as low as possible, heat consumption is kept to a minimum in spite of high temperature uniformity, and the NOx and CO emissions are reduced to the maximum possible extent.
He is the author of dozens of technical papers on industrial gas applications in steelmaking, pulp & papermaking and water treatment, and editor of a book on the Argon-Oxygen Decarburization process.
absence of the need to use graphitized electrodes will allow refusing from the steel decarburization process, that will simplify and make easier process of movement of the plasmatrons;
It requires removal of the decarburization surface layer, as well as the maintenance of a flat and smooth area for the hardness impression.
The minimum and maximum microhardness are observed near the boundary between the facing and backing, which is associated with the redistribution of carbon because of increased solubility in the liquid phase and decarburization at the liquid-solid phase interface.
In addition, the short heating time improves the metallurgical properties of the hardened zone by reducing grain growth, decarburization, and oxidation of the pin
When austenitizing, care must be taken to avoid carburization or decarburization by carefully monitoring the heat-treating atmosphere.