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Topic: Cementite

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In the News (Tue 21 May 19)

  The structure of cementite
Cementite has an orthorhombic lattice with approximate parameters 0.45165, 0.50837 and 0.67297 nm.
"Modelling and Characterisation of molybdenum carbide precipitation and Cementite Dissolution during the tempering of Fe-C-Mo martensitic steel"
"Modelling and Characterisation of Vanadium Carbide precipitation and Cementite Dissolution during the tempering of Fe-C-V martensitic steel"
www.msm.cam.ac.uk /phase-trans/2003/Lattices/cementite.html   (225 words)

 Saarstahl AG
Through this heat treatment, the cementite lamination of the perlite is transformed to a spherical form - known as granular cementite.
For hypoeutectoid steels, the microstructure consists of perlite and ferrite and for hypereutectoid steels of perlite and cementite.
Due to this intermediate anealing, it is possible to cut out the carbon released as surplus in the austenite carbon as cementite and avoid the risk of formation of residual austenite during the subsequent case refining process.
www.saarstahl.com /english/produkte/waermebehandlung_eigenschaften/arten/arten1.htm   (3159 words)

  Iron And Steel - LoveToKnow 1911
These are cementite, a definite iron carbide, Fe 3 C, harder than glass and nearly as brittle, but probably very strong under gradually and axially applied stress; and ferrite, pure or nearly pure metallic a-iron, soft, weak, with high electric conductivity, and in general like copper except in colour.
Ferrite and cementite are thus the normal and usual constituents of slowly cooled steel, including all structural steels, rail steel, andc., and of white cast iron (see § 18).
As the temperature sinks still farther, pro-eutectoid cementite (see § 22) forms progressively in the austenite both primary and eutectic, and this pro-eutectoid cementite as it comes into existence tends to assemble in the form of a network enveloping the kernels or grains of the austenite from which it springs.
1911encyclopedia.org /I/IR/IRON_AND_STEEL.htm   (14043 words)

 New Page 2
The cementite aligns because of the presence of impurity elements present in the interdendritic zone.
The closer the interdendritic zones, the closer the aligned globular/spheroidal cementite are, and therefore, the finer the final surface pattern.
It is the large cementite particles responsible for the thicker “thread” of the Damascus patterns.
home.att.net /~moltenmuse/Production.htm   (1538 words)

 The Tempering of Martensite: Part Two   (Site not responding. Last check: 2007-09-10)
It is likely that this interlace cementite is responsible for tempered martensite embrittlement, frequently encountered as a toughness minimum in the range 300-350°C, by leading to easy nucleation of cracks, which then propagate across the tempered martensite laths.
This influence on the cementite dispersion has other effects, in so far as the carbide particles, by remaining finer, slow down the reorganization of the dislocations inherited from the martensite, with the result that the dislocation substructures refine more slowly.
In plain carbon steels cementite particles begin to coarsen in the temperature range 350-400°C, and addition of chromium, silicon, and molybdenum or tungsten delays the coarsening to the range 500-550°C. It should be emphasized that up to 500°C, the only carbides to form are those of iron.
www.key-to-steel.com /IT/ViewArticle.asp?ID=128   (1527 words)

 Examination of Blades
The alignment of the cementite, however, is not very strong indicating that the blade would not have had a crisp Damascus pattern.
The microstructure of the cementite is not unlike that found in KIS #15, both have cementite needles that are beginning to break up and form spheroids.
The mottled appearance is due to slight variations in the elemental compositions of the different regions, corresponding to the original location of dendrites and interdendritic regions that formed during the initial solidification of the metal.
home.att.net /~moltenmuse/examination.htm   (1638 words)

 Ferritic-pearlitic steels
The relatively coarse and partially spheroidized cementite particles produce a simultaneous decrease in both the tensile and the yield strength after the SA treatment when compared to the CC processing.
On the other hand, the inhomogeneous distribution of cementite and the presence of lamellar pearlite deteriorate the reduction of area as observed after the SA process.
In both cases fine cementite particles were homogeneously distributed in the ferrite matrix and 65-70% of all ferrite interfaces were high angle grain boundaries.
www.mpie-duesseldorf.mpg.de /1371/?L=1   (3465 words)

 The ABCs of Steel Metallurgy
For instance, cementite is an intermetallic compound of iron and carbon, and pearlite was so named because of its pearl-like appearance.
Cementite and ferrite join in a lamellar form to produce pearlite.
The 0.8% C steel was chosen because it is one of the easiest to harden.
www.aws.org /wj/2003/02/031   (3074 words)

 Untitled Page
The film of cementite at the martensite plate boundaries is due to the decomposition of retained austenite.
C, 5 h is associated with a minimum in toughness because of the precipitation of relatively coarse cementite platelets in a Widmanstätten array.
C leads to the coherent precipitation of needle--shaped molybdenum--rich zones, and a peak in the strength; the precipitation occurs at the expense of the cementite particles, so the increase in strength is also accompanied by a large increase in toughness.
member.newsguy.com /~nutech/uoc.html   (2933 words)

One way for carbon to leave the austenite is for cementite to precipitate out of the mix, leaving behind iron that is pure enough to take the form of ferrite, and resulting in a cementite-ferrite mixture.
Cementite is a stoichiometric phase with the chemical formula of Fe Cementite forms in regions of higher carbon content while other areas revert to ferrite around it.
Tungsten interferes with the formation of cementite, allowing martensite to form with slower quench rates, resulting in high speed steel.
www.oobdoo.com /wikipedia/?title=Steel   (5456 words)

CEMENTITE (Fe Cementite is also known as iron carbide which has a chemical formula, Fe It contains 6.67 % Carbon by weight.
The excess cementite deposits in the grain boundaries.
This excess cementite is also known as proeutectoid cementite.
info.lu.farmingdale.edu /depts/met/met205/fe3cdiagram.html   (420 words)

 Heat Treat Chemistry   (Site not responding. Last check: 2007-09-10)
Pearlite is a mixture of Ferrite and Cementite.
Cementite is a compound of iron and carbon known as "iron carbide".
However, Cementite is present in the alloy between 0.8% and 6.67% carbon.
www.energysolutionscenter.org /HeatTreat/TechPro/HeatTreatChemistry.htm   (1485 words)

 StopTech : Balanced Brake Upgrades   (Site not responding. Last check: 2007-09-10)
Cementite is very hard, very abrasive and is a poor heat sink.
When deposit are present, by having isolated regions that are proud of the surface and running much hotter than their neighbors, cementite inevitably forms and the local wear characteristics change which results in ever increasing TV and roughness.
The trouble with this procedure is that if the grinding does not remove all of the cementite inclusions, as the disc wears the hard cementite will stand proud of the relatively soft disc and the thermal spiral starts over again.
www.stoptech.com /tech_info/wp_warped_brakedisk.shtml   (2986 words)

 Names and Steel
In 1882 he discovered the iron-carbon "Mischkristalle" and became relatively famous.
"Ledeburite" as a name for the iron - cementite eutectic was adopted in honor of his achievements.
Martens started as an engineer, made it to the director of the royal mechanical laboratory, which evolved into the "Staatliche Materialprüfungsamt" in Berlin.
www.tf.uni-kiel.de /matwis/amat/mw1_ge/kap_8/advanced/t8_4_1.html   (585 words)

 Principle of Heat Treating
Steel having a carbon content greater than.85 percent (hypereutectoid steel) has an excess of cementite over that required to mix with the ferrite to from pearlite, hence both cementite and pearlite are present in the fully annealed state.
The structural constitution of carbon steel in terms of ferrite, cementite, pearlite and austenite for different carbon contents and at different temperatures is shown by the accompanying diagram.
The temperature at which the excess ferrite or cementite is completely dissolved into the austenite is called the upper critical point.
www.sonic.net /~blade/Info___Links/About_Steel/Principle_of_Heat_Treating/principle_of_heat_treating.html   (2172 words)

 [No title]   (Site not responding. Last check: 2007-09-10)
When the cementite particles precipitate, the tetragonal distortion of the bct crystal structure disappears and the phases present are ferrite (bcc Fe) and cementite, just as predicted by the phase diagram.
In this condition, the cementite particles don't contribute much to the strength of the steel and they are large enough to be observed in an optical microscope.
Notice that the ferrite and cementite phases present in the spheroidized steel are exactly the same phases present in pearlite: [gamma] goes to [alpha] + Fe However, changing the size, shape and distribution of the phases in steel produces different combinations of mechanical properties.
www.tu-darmstadt.de /fb/ms/student/fs/german/lab/w4/mse4-2.htm   (3634 words)

 Cementite   (Site not responding. Last check: 2007-09-10)
Cementite is iron carbide with the formula Fe C, and an orthorhombic crystal structure.
Cementite contains 6.67% Carbon by weight; thus above that carbon content in the Fe-C phase system, the alloy is no longer steel or cast iron, as all of the available iron is contained in cementite.
Cementite mixes with ferrite, the other product of austenite, to form lamellar structures called pearlite and bainite.
www.threeplanes.net /cementite.html   (244 words)

 Iron Phase Diagram   (Site not responding. Last check: 2007-09-10)
Cementite is a hard brittle compound with and orthorhombic crystal structure each unit cell has 12 Fe atoms and 4 C atoms
Below is an Isothermal Transformation (IT) diagram, also called a TTT (Time, Temperature, Transformation) curve for a eutectoid steel test piece which has been rapidly cooled in a bath at a set temperature, held for a time and then water quenched.
The crystal structure is a stressed structure which is resistance to dislocation movement it is therefore strong and relatively brittle.
www.roymech.co.uk /Useful_Tables/Matter/Phase_diagram.html   (974 words)

 Sword Forum International - A Metallurgical Rosetta Stone
Ac1: The temperature, upon heating, that corresponds with the boundary between the ferrite-cementite field and the fields containing ferrite and austenite or cementite and austenite.
Cementite: Iron carbide (Fe3C), for the purposes of this forum this will mostly be used in reference to the form carbon takes in steel.
In alloys greater than.83% (hypereutectoid) there will be pearlite and varying degrees of proeutectoid cementite leftover when the steel is slow cooled.
forums.swordforum.com /printthread.php?threadid=39472   (1392 words)

 Structure of plain steel   (Site not responding. Last check: 2007-09-10)
Carbon is present as a compound of iron and carbon (6-67 %) called cementite, having the chemical formula Fe This cementite is hard (Brinell hardness 600 +), brittle and brilliantly white.
These two phases are ferrite and cementite which form a eutectic mixture, containing 0,87% carbon and known as pearlite.
Again, the alloy solidifies as a cored solid solution, but on reaching line FP, cementite starts to be ejected and the residual alloy becomes increasingly poorer in carbon until point P is reached, when both cementite and ferrite form in juxtaposition.
www.key-to-steel.com /ViewArticle.asp?ID=3   (1045 words)

 Engineering Materials – NOTES – Chapter 9 – Phase Diagrams
Recall, pearlite is a layered combination of cementite (Fe C) and ferrite (Fe with some C dissolved in it).
Cementite is harder and more brittle than ferrite.
Strong adherence at the boundary between cementite and ferrite.
www.uwplatt.edu /~mirth/me3040ch10.htm   (1320 words)

 Title page for ETD etd-10132004-194232 ( Browse | Search ) All Available ETDs
In this type of hypereutectoid steel, the proeutectoid cementite precipitates along the austenite grain boundaries prior to the formation of the pearlite.
At the beginning of this work, two proeutectoid cementite networks were identified; one in the center and the other close to the surface of the wire rod.
It was also used to verify the influence of the environment on the transformation of austenite and the precipitation of the proeutectoid cementite.
etd.library.pitt.edu /ETD/available/etd-10132004-194232   (264 words)

 Interactive Practice Quiz Template
Represents a phase of pearlite with cementite around the grain boundaries.
Represents a microstructure of pearlite with cementite around the grain boundaries.
The eutectic point; At this temperature, a transformation from liquid iron to solid austenite and cementite occurs..
www.ul.ie /~walshem/fyp/quiz3.htm   (172 words)

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