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Cementite, also known as iron carbide, is a chemical compound of iron and carbon, with the formula Fe3C (or Fe2C:Fe). It is 6.67 percent carbon and 93.3% iron. It has an orthorhombic crystal structure. It is a hard, brittle material, normally classified as a ceramic in its pure form, though it is more important in metallurgy. MetallurgyThe iron-carbon phase diagramIn the iron–carbon system (i.e. plain-carbon steels and cast irons) it is a common constituent because at room temperature ferrite (essentially, the pure iron phase) can only hold 0.02% in solution. Therefore, in carbon steels and cast irons that are slowly cooled a portion of the elements are in the form of cementite. It forms directly from the melt in the case of white cast iron. In carbon steel, it either forms from austenite during cooling or from martensite during tempering. An intimate mixture with ferrite, the other product of austenite, forms a lamellar structure called pearlite. From Wikipedia under the
GNU Free Documentation License  corusgroup.com 390px x 480px | 159.00kB [source page] Steel Micro Structure Cementite  msm.cam.ac.uk 338px x 370px | 7.30kB [source page] 6 jpg 17 Oct 2004 12 45 7 2K 5 jpg 17 Oct 2004 12 45 27K 4 jpg 17 Oct 2004 12 45 7 3K 3 jpg 17 Oct 2004 12 45 24K  proservicetech.it 996px x 1282px | 171.40kB [source page] Immagini Acquisizione di una curva di raffreddamento e derivata prima Analisi e confronto di piu curve gia acquisite Calibrazione del sistema attraverso il modulo Auto Tuning From Yahoo Image Search: "Cementite"  materialengineeringsociety.blogspot.com Material Engineering Society Fri, 01 Feb 2008 09:21:00 GM ageing at 200 c and above leads to the second stage of ageing in which orthorhombic . cementite. fe3c is formed as platelets on {110} . often the platelets grow on several {110} planes from a common centre giving rise to structures which ... From Google Blog Search: "Cementite"  news.google.com Nanowerk LLC The strengthening arises due to the presence of nanoscale cementite /ferrite lamellar structure. The ferrite phase in this structure contains very high ... news.google.com Tuscia Web Tre mani successive di cementite hanno preparato il compensato a ricevere i colori. Anche queste fasi del lavoro sono documentato nei pannelli alla nostra ... and more » news.google.com Savona news Molti ritengono che la passeggiata a mare sia stata concepita da un'Amministrazione in preda al virus della cementite acuta ; anche Piazza Italia avrebbe ... and more » From Google News Search: "Cementite" How are ferrite, cementite and pearlite formed? Q. How are ferrite, cementite and pearlite formed? Asked by devilblues - Sat Jul 14 07:50:16 2007 - - 1 Answers - 0 Comments A. The three phases, ferrite, cementite and pearlite are thus the principle constituents of the infrastructure of plain carbon steels, provided they have been subjected to relatively slow cooling rates to avoid the formation of metastable phases. Answered by Dr.Shashikant - Sat Jul 14 07:56:52 2007 carbon steel question, multichoice. need help? Q. If a 0.8% C steel is heated to 650 C then the microstructure would contain? (a) Cementite only (b) Austenite only (c) Ferrite and Austenite (d) Pearlite only Asked by Bolter - Mon Nov 10 20:20:07 2008 - - 1 Answers - 0 Comments material science questions, plz tell me the reason?
Q. 5. Which of the descriptions are true for gray cast iron? (three corrected answers) (A)The carbon contents vary between 2.5 and 4.0 wt%. (B) Cementite formation is promoted by the presence of silicon in concentrations greater than about 1%. (C) The cementite exists in the form of flakes. (D) Gray iron is comparatively weak and brittle in tension. (E) Gray irons are very effective in damping vibrational energy. 6. Heating white cast iron at temperatures between 800 and 900 for a prolonged time period and in a neutral atmosphere (to prevent oxidation) produces which of the following alloy? (A) Ductile cast iron, (B) Gray cast iron, (C) Malleable cast iron, (D) Nodular iron, or (E) Tempered martensite. Asked by Sunny - Sun Jun 14 21:21:16 2009 - - 1 Answers - 0 Comments A. By now you would have turned this paper in, but I would have to say 5.: D and 6.: C. Answered by He Lives! - Thu Jun 18 13:21:03 2009 From Yahoo Answer Search: "Cementite" |
