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Microstructural Characteristics of Metals
Published in Vladimir B. Ginzburg, Metallurgical Design of Flat Rolled Steels, 2020
Ledeburite is an eutectic in the iron-carbon system, the constituents being an austenite and a cementite. The eutectic contains 4.3% carbon. It is a constituent of iron-carbon alloys containing more than 2% carbon and for this reason the dividing line between steels and cast iron is set at 2% carbon. Fig. 1.22 illustrates the microstructure of ledeburite in cast iron [3].
Iron–Carbon Phase Diagram
Published in Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak, Phase Transformations and Heat Treatments of Steels, 2020
Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak
Whenever the liquid crosses this line EFG at the eutectic point F, the eutectic reaction takes place, and the liquid solidifies into a mixture of two phases, namely, austenite (γ) and cementite (Fe3C). This eutectic mixture is commonly known as ledeburite. It is usually not seen in microstructures since austenite undergoes another transformation during further cooling. In general, the alloys that are having more than 2.11% carbon are categorized under cast irons. Furthermore, the cast irons are subdivided into two classes. The alloys having carbon between 2.11% and 4.3% are called as hypoeutectic cast irons, whereas those having carbon between 4.3% and 6.67% are called as hypereutectic cast irons. Depending upon this classification, which is based on the amount of carbon, the composition of the alloy at the eutectic temperature varies. For example, the hypoeutectic cast irons (say 3% C) consist of proeutectic austenite along with liquid before the eutectic reaction takes place. In contrast, hypereutectic cast irons (say 5% C) comprise proeutectic cementite. The exact amount of these proeutectic phases is determined by using the Lever rule. The remaining amount of liquid transforms into the mixture of austenite and cementite, i.e., ledeburite upon cooling at the eutectic temperature.
The Alloys of Iron, Their Physical Nature, and Behavior During Deformation
Published in William L. Roberts, Cold Rolling of Steel, 2017
In the iron-carbon system, solid solutions of carbon in delta, gamma and alpha iron exist, namely, delta solid solution, austenite and ferrite. A eutectic (ledeburite) occurs at a composition of 4.3% carbon and consists of austenite (1.7% carbon) and cementite. There is also a eutectoid (pearlite), containing close to 0.8% carbon, consisting of ferrite and cementite.
Formation behaviours of blowhole and chill layer by GTAW in cast iron
Published in Welding International, 2018
Toshiyuki Hasegawa, Michinori Okubo
Figure 3 shows the microstructure in the vicinity of the weld bonds made with Fe-Cr-Ni filer metal. In both flake graphite cast iron (a) and nodular graphite cast iron (b), a chill layer derived from ledeburite, a eutectic structure of austenite and cementite, was observed near the bond on the base metal. In both cases, a martensite/bainite structure, caused by rapid cooling after welding, is evident nearer the bond in the heat-affected zone (HAZ). Further, in the HAZ of the nodular graphite cast iron, around the graphite a small-grain bainite structure is evident in the base ferrite granules and also in a part of the grain boundaries.