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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 ?
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;
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.
One of the root causes of these problems resides in the surface decarburization or carburization of the sintered parts which are the result of carbon potential fluctuation in the sintering furnace.
Melting of the ore-coal pellets in the arc furnace is characterized by diversity of heat and mass transfer processes, stipulated by action of both heat engineering and combination of physical-chemical factors, which accompany decarburization of the pool, slag formation, oxidation of the metal by oxygen of the furnace atmosphere, etc.
Each of the six ladles of steel was melted in a single, 95-ton electric arc furnace and then subsequently treated and kept hot in rotation in either the vacuum arc degassing unit or the similar vacuum oxygen decarburization unit," Marston said.
In wet hydrogen-containing atmospheres this reaction accounts for most of the decarburization.
Driven by energy security, decarburization and industrial benefit, the Chinese government has set up an ambitious plan to achieve 30-gigawatt installations by 2020 in the offshore wind industry.
The developed technological process for production of especially low-carbon steel included melting of the intermediate product in ASF from the metal scrap with addition of a portion of non-conversion iron (or some other primary raw material) for ensuring minimal content of non-ferrous metals (chromium, nickel, copper); tapping of the intermediate product into the ladle and its partial reduction; decarburization of the metal on the degassing installation of the chamber type; bringing of the metal up to the assigned chemical composition in the ladle--furnace installation; casting of steel on MCCB with full protection of the jet against secondary oxidation and application of the system for electromagnetic mixing of metal in the mould.