PDF | On Feb 1, , Doru M. Stefanescu and others published Classification and Basic Metallurgy of Cast Iron. 𝗣𝗗𝗙 | On Oct 15, , Doru M Stefanescu and others published A History of Cast Iron. PDF | Cast iron with 3 wt. % Cu was prepared by induction melting and casting in sand molds. The structure of the samples was studied using light microscopy.
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Cast Iron Microstructure specifically, the inoculant enhances graphite nucleation, preventing the formation of primary carbides. Anomalies and Their Using the. Cast iron production in Ancient Greece: myth or fact? Mediterranean Archaeology and Archaeometry, vol.6, No 2 (), Maria Kostoglou. Steel and cast iron Chapter 11 - 1 Chapter 11 - 2 1 Taxonomy of Metals Metal Alloys Adapted from Ferrous Nonferrous Fig. , Callister 7e. Steels Steels Cast.
Magnesium, however, is a very reactive can occur between the Mg in the iron and the oxygen in the element.
As a consequence, ductile iron has a higher tendency to surrounding environment. This reaction can form dross, even in the form slag than does gray iron or malleable iron. The reaction mold.
Dross defects such as this can occur, for example, in castings products that result are often called dross. The presence of Mg in with knife gates. Dross can also be generated in the runner system molten iron also causes the iron to generate slag, almost continu- when fluid dynamics causes turbulent flow conditions to exist. This dross is the result of the Mg too cold. As a consequence, a good slagging practice must be exercised when pouring ductile iron. Sometimes, the dross is associated with undissolved or partially dissolved inoculant.
Figure 26 shows an example. Figure 24 shows an ex- have a normal silicon level, whereas the structure on the opposite side ample of the graphite structure associated with dross that has oc- will have a high Si level.
Energy dispersive x-ray EDX spectro- curred in the casting. When etched, the area associated with the dross graphic analysis has been helpful in identifying this type of dross will often have a ferritic structure, as shown in Fig. The occur- defect. Figures 27 and 28 show a typical example of analysis in the rence of dross in a casting can be the consequence of poor slagging normal structure vs.
When slag enters the mold cavity during pouring, the dross-type structure shown in Figs.
Other elements are also known to cause this problem. Lead levels as low as 0.
If the condition becomes significant, the precipitation onto crystallographic planes can occur, aside from the primary graphite flakes, creating hatch marks in the structure. Photomicrograph showing same area seen at lower magnification in Figs. Also note graphite forms with thin graphite forms in note that other graphite forms have precipitated within regions between graphite flakes toward middle and middle top; X, between flakes; X, unetched condition.
Photomicrograph showing a pearlitic gray cast iron with Fig. Photomicrograph of ductile cast iron. Photomicrograph showing same area seen at lower Fig. Photomicrograph of same area shown at lower magnifica- magnification in Fig.
Photomicrograph showing same area seen at lower austenitizing temperature reached, in three-phase region indicated magnification in Figs. In the two examples, the austenitizing tem- rich steadite regions. Research1,2 has shown that this graphite type perature reached the three-phase region, indicated by the arrow in can be controlled with the addition of rare earth elements, primarily the phase diagram in Fig.
As a consequence, the condition does not often occur in As a consequence, the austenite that was present transformed to ductile cast iron because of the presence of rare earth elements in the the desired pearlite or ferrite constituent.
However, the ferrite or treatment alloy. If the condition is occurring in gray cast iron, it can pearlite that was present in the structure, but was not transformed, be controlled by eliminating the lead. However, inoculation with a remained intact as the sample was cooled. The structures shown in cerium-bearing inoculant can also reduce the effect. The untransformed constituents are properties of the resulting iron. For example, a normal Class 30 gray the cause of the unusual shapes in the photomicrographs.
Cast irons that are quenched and tempered to form martensite can have unusual microconstituents. In addition to the expected marten- site, an unexpected white constituent in the structure can occur. Unusual Ferrite Microstructure in This white constituent is shown in Figs. The constituent is retained Analyzing microstructures can sometimes be confusing. For ex- austenite. All of these constituents are normally expected dissolved in the austenite, prior to quenching.
As the temperature for ductile iron microstructures. However, the shapes and the con- increases above the eutectoid reaction, the amount of carbon dis- stituents as shown in these photomicrographs are not normal.
When this iron is quenched, some Both structures resulted from heat treatment. The structure was the of the high carbon austenite is retained, leaving a mixed structure of consequence of a normalizing heat treatment intended to produce martensite and austenite.
As these structures clearly show, the goal was not of martensite and high carbon austenite. To prevent retained austenite from occurring in quenched mar- Ductile iron is in a family of metals called cast iron, which has tensitic cast iron structures, the temperature from which the iron is three principal elements: The fact that Si is quenched should be lowered to a temperature immediately above the present is often forgotten.
At certain temperatures, this element eutectoid. The correct temperature may require trial and error to allows austenite, ferrite and carbides to exist in equilibrium as a establish it for individual irons.
The reason is that the eutectoid three-phase field. The presence of this field can cause difficulties, temperature varies significantly, as a function of Si, and no single particularly during heat treatment.
Nickel also To normalize or anneal ductile cast iron, the casting must be stabilizes austenite. As Ni content increases, so does the tendency for heated to a high enough temperature for the matrix to become retained austenite. Photomicrograph illustrating retained austenite in a Fig. Photomicrograph illustrating retained austenite in a martensitic ductile cast iron.
Small angular white constituents martensitic ductile cast iron. Small angular white constituents arrows in matrix are retained austenite; remainder of matrix is arrows in matrix are retained austenite; matrix is martensite; martensite; X, nital etch. Photomicrograph illustrating retained austenite in a martensitic gray cast iron.
White angular constituent in structure is martensitic gray cast iron. White angular constituent is retained retained austenite; remainder of matrix is martensite; X, nital austenite; remainder of matrix is martensite; X, nital etch. Poor nodularity negatively affects both the yield strength Affect Ductile Iron Properties and elongation.
The microstructure of ductile iron plays a vital role in affecting the mechanical properties of the final casting. For Prob- experience with a certain casting is provided. This grade is an as-cast pearlitic ductile iron with a minimum ultimate tensile strength of 80, psi, a For Problem 2 failing to meet the yield strength requirement , minimum yield strength with 0.
Problem 1: Lustrous Carbon Defects Problem 2: The castings failed to meet the yield strength require- in Cast Iron3—5 ment, with only a 50, psi at 0. Problem 3: The castings failed to meet the yield strength and the Lustrous carbon defects generally appear on the surface or just elongation requirements. It can be reasons for these inconsistencies. The volatile gases are released as the organic intercellular carbides Fig. As shown in Fig.
These carbides significantly carbons. It is often removed from the ferrite content was excessive. Figure 44 shows that the ferrite the casting surface by casting cleaning operations. Excessively high ferrite content the lustrous carbon folds into solidifying metal, causing unaccept- detracts from the yield strength. Unusual Hard Spots The use of tin as a pearlite stabilizer is well established. Tin decreases the sensitivity of the casting to variations in shakeout time.
However, excess Sn, espe- cially in the presence of high S, can cause serious problems. Photomicrograph showing high incidence of intercellular carbides in casting. Based on the application of cast iron, the alloying elements added to the furnace differ. The commonly added alloy elements are carbon followed by silicon. The other alloying elements added are chromium, molybdenum, copper, titanium, vanadium, etc. How is cast iron classified?
Based on the alloying elements added, the variation in the solidification of the cast iron and heat treatment used, the microstructure of the cast iron can vary. Depending upon the application and the preferred mechanical properties, iron castings can be classified into the following.
Types of cast iron White cast iron When the white cast iron is fractured, white coloured cracks are seen throughout because of the presence of carbide impurities. White cast iron is hard but brittle. It has lower silicon content and low melting point. The carbon present in the white cast iron precipitates and forms large particles that increase the hardness of the cast iron.
It is abrasive resistant as well as cost-effective making them useful in various applications like lifter bars and shell liners in grinding mills, wear surfaces of pumps, balls and rings of coal pulverisers, etc. Based on the application of cast iron, the alloying elements added to the furnace differ. The commonly added alloy elements are carbon followed by silicon. The other alloying elements added are chromium, molybdenum, copper, titanium, vanadium, etc.
How is cast iron classified? Based on the alloying elements added, the variation in the solidification of the cast iron and heat treatment used, the microstructure of the cast iron can vary. Depending upon the application and the preferred mechanical properties, iron castings can be classified into the following. Types of cast iron White cast iron When the white cast iron is fractured, white coloured cracks are seen throughout because of the presence of carbide impurities.
White cast iron is hard but brittle. It has lower silicon content and low melting point. The carbon present in the white cast iron precipitates and forms large particles that increase the hardness of the cast iron.
It is abrasive resistant as well as cost-effective making them useful in various applications like lifter bars and shell liners in grinding mills, wear surfaces of pumps, balls and rings of coal pulverisers, etc.