Cast iron flake graphite

Cast iron, flake graphite, plain or low alloy 0 2 0 2 <400 K750 Cast No Fair 45 6.7 ... 

Figure 2.13 Microstructures obtained by varying thermal treatments in cast irons (Gf = graphite flakes = graphite rosettes G = graphite nodules P = pearlite). From K. M. Ralls, T. H. Courtney, and J. Wulff, Introduction to Materials Science and Engineering. Copyright 1976 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

Graphite. This is the tree or linnunhiiied carbon usually found in cast irons Because graphite occurs as flakes, cast irons are easily machinable even though they have a high resistance u> abrasion. 

The Al-Si alloy shows distinct precipitates (<20pm), characteristic of Al-Si alloys of eutectic composition. The cast iron contain graphite flakes typical of grey cast iron, while no discemable microstmctural features are present for the Cr-bearing steel. Table 3 shows the composition and properties of the materials. 

Alloys with other useful properties can be obtained by using yttrium as an additive. The metal can be used as a deoxidizer for vanadium and other nonferrous metals. The metal has a low cross section for nuclear capture. 90Y, one of the isotopes of yttrium, exists in equilibrium with its parent 90Sr, a product of nuclear explosions. Yttrium has been considered for use as a nodulizer for producing nodular cast iron, in which the graphite forms compact nodules instead of the usual flakes. Such iron has increased ductility. 

An ahoy of titanium containing 40—50% Ti and 45—50% Si is used as an additive in cast iron to shorten the graphite flakes. The effect is to provide a smooth casting surface. The resulting casting is then used to produce glass botde molds. 

Another group of cast-iron alloys are called Ni-Resist, These materials are related to gray cast iron in that they have high carbon contents (3 percent), with fine graphite flakes distributed throughout the structure. Nickel contents range from 13.5 to 36 percent, and some have 6.5 percent Cu. 

Figure 17.1 Flakes of graphite embedded in a matrix of iron (gray cast iron).

The specimen in Fig. 17.15 is part of a cast iron pump impeller. The spongelike surface contours are apparent, as is the black coating that covers surfaces exposed to the cooling water. Microstructural examinations revealed preferential deterioration of the iron matrix surrounding the graphite flakes. 

Because cast iron has a carbon content approximately equivalent to its eutectic composition, it can be cast at lower temperatures than steel and flows more readily than steel because of its much narrower temperature solidification range. The presence of the graphite flakes in cast iron decreases its shrinkage on solidification much less than that of steel. These factors contribute to the fabrication of cast iron as sound castings in complex shapes and with accurate dimensions at low cost. 

Austenitic cast irons (either flake graphite irons or nodular graphite irons) are produced by mixing in nickel from 13-30%, chromium from 1-5% and copper from 0.5-7.5 (to lower nickel-containing grades to augment the corrosion resistance at lower cost). 

The persistent increase in volume of cast iron items in high-temperature situations becomes the limiting factor in the use of unalloyed cast irons, especially in flake graphite castings [4,5]. 

Properties of flake graphite-grade cast irons.58... 

Cast irons, although common, are in fact quite complex alloys. The iron-carbon phase diagram exhibits a eutectic reaction at 1 420 K and 4-3 wt.<7oC see Fig. 20.44). One product of this eutectic reaction is always austenite however, depending on the cooling rate and the composition of the alloy, the other product may be cementite or graphite. The graphite may be in the form of flakes which are all interconnected (although they appear separate on a... 

Scaling results for the flake graphite cast irons a, b, d and e in Fig. 7.21 show that the weight increase related to surface area due to scaling rises as the quantity of graphite increases with increase in carbon content (iron a), and as the graphite becomes more widely dispersed in the matrix (iron d). Apart from carbon content, changes in the base metal composition and... 

Meehanile CC (formerly KC) Flake graphite-pearlitic cast iron for general use for solutions with pH less than 2... 

Meehanite HE Flake graphite-pearlitic cast iron all-round material for general use with good thermal shock resistance... 

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