Development of Theories on Graphite Formation in Ductile Cast Iron. By:Cees van de Velde Last revision:January 15, 2004 1. INTRODUCTION Conducting a survey on the subject of solidification of nodular cast iron is no easy task as the number of publications in this field, along with the different opinions on the nodule formation process, appear endless.
CompactMag™ Si,Mg, Ca, Rare Earths Highly effective alloy for the production of compacted graphite irons with reduced section sensitivity and wide production window. Please refer to your local Elkem representative for further information on the range of products available for grey, compacted and ductile irons.
Nov 01, 2016· Graphite flotation, which potential causes can be high carbon equivalent, excess of pouring temperature, slow cooling rate in thicker sections or an insufficient inoculation. ... Ductile cast irons are versatile alloys thanks to the possibility to obtain different combinations of mechanical and technological properties by means of the chemical ...
Abstract : Ductile Iron castings with section thickness 60mm, 70mm & 80mm were ... The microstructure of typical commercial spheroidal graphite irons in as cast condition consists ... Graphite flotation and spiky graphite are found. Fig. …
Graphite Flotation Nodule Alignment Carbides Flake Graphite Surface Structure Common Metallurgical Defects in Ductile Iron Compacted Graphite Exploded Graphite Chunky Graphite Spiky Graphite Potential Causes; Low residual magnesium and/or rare earth from poor nodularisation practice, high temperatures or long holding time.
Sep 07, 2018· Graphite formation in the solid state is both in ductile cast irons and in steels strongly promoted by high silicon contents above 3 wt.% Si. The matrix microstructure in austempered ductile iron can be further refined by …
Apr 01, 2008· A degenerated graphite layer was found only on the surfaces exposed to the nitrogen containing binder . The conversion of soluble nitrogen to an insoluble form by adding Ti and Ce (RE) proved to be effective in minimizing the flake graphite formation. Therefore, 0.02%-0.04% titanium may be desirable in ductile irons . 3. Conclusions (1)
Search Results for degradation-of-graphite-morphology-in-high-magnesium-content-ductile-cast-irons. Degradation of Graphite Morphology in High Magnesium Content Ductile Cast Irons. Author: Chong Sun ... Such an investigation usually involves cast iron with varying graphite nucleation potential and varying content of spheroidizing ...
Dec 01, 2001· Case Study 3--This foundry produced heavy section ductile iron castings using induction melting and tundish treatment. Heavy section casting problems included graphite flotation, segregation, shrinkage and relatively poor nodularity. The (Ga, Ce, S, O)-containing inoculant and a Ba-inoculant were tested as ladle additions.
increased dross formation in both ductile and compacted graphite irons. However, in ductile iron, a minimum sulfur level of at least 0.005 to 0.008 percent is necessary after magnesium treatment to insure proper post-inoculation and reduce the risk of carbides.
Jan 17, 2014· The remaining most common defect in ductile iron is graphite flotation (Figure 19). It is basically modified graphite, not detectable through UT or MPI, and it only appears as a color variation on the casting surface. The influence of graphite flotation on mechanical properties is small (about -6%).
late graphite can be increased considerably by using a hypereutectic chemistry between 4.33 and 4.60 that solidifies without a graphitic liquidus. In other words, below a certain C.E. value, the presence of Magnesium and possibly other elements in Ductile Iron, prevent graphite from forming in the liquid. So
In hypereutectic nodular cast irons, primary precipitation of graphite may lead to graphite flotation in thick section castings. Graphite degeneracy such as so-called exploded graphite is then often associated with this flotation phenomenon and it appears as precipitates where the nodular form is replaced by star-like or flower-like shape. It has been reported that exploded …
Graphite Formation and Dissolution in Ductile Irons and Steels Having High Silicon Contents: Solid-State Transformations, Metallography, Microstructure, and Analysis, 2018, pp. 1-9, DOI: 10.1007/s13632-018-0478-6
In ductile irons, graphite is in the form of nodules rather than flakes as in gray iron. Nodule formation is achieved by adding a small amount of magnesium or cerium to the alloy when in the liquid phase, the growth of graphite can be slowed during the solidification process. Whereas sharp graphite flakes create stress concentration points ...
Answer: I cannot cite specific physical processes within a fluid metal that cause graphite flotation. However, graphite and iron have widely different densities and melting points so a large enough conglomeration of solid graphite in an otherwise fluid iron system
On the other hand, the appearance of some graphite degen- eration such as chunky graphite has also been related to high silicon contents in ductile …
Jan 07, 2017· Graphite floatation This is caused when large, low density graphite nodules are formed during the solidification of thick section or otherwise slow cooling castings.
Sep 10, 2019· EN 1563, Founding—Spheroidal Graphite Cast Irons (2011) 51. R. González-Martinez, U. de la Torre, J. Lacaze, J. Sertucha, Effects of high silicon contents on graphite morphology and room temperature mechanical properties of as-cast ferritic ductile cast irons. Part I—microstructure. Mater. Sci. Eng. A 712, 794–802 (2018)
Feb 16, 2021· ICME National Webinar "Graphite Nucleation in Grey and Ductile Irons". Presented by Dr.Torbjorn Skaland, Mr. Mark Sims & Mr. James Vaughan – Elkem Ltd. The Technical Lecture will be streamed online only as a webinar due to ongoing Covid 19 restrictions. You may join the webinar at 7.15 pm where there will be the opportunity for attendees ...
2. exploded graphite if Mg > 0,07 % combined with a high Ceq and the presence of (fairly high) Ce- content This graphite is mostly combined with graphite flotation (graphite can be completely nodular with graphite flotation at Mg < 0,065 %) in thick sections, at hot spots and in the connection of the riser and casting section.
Inoculation in Cast Iron. Poor base iron nucleation and inoculation can be a typical cause for the formation of poor graphite structures in both gray and ductile irons, which can ultimately lead to the desired mechanical and physical properties not being met. The morphology, chemistry and crystallinity of the recarburizer material can have a ...
Jan 06, 2010· MeltLabGuy (Materials) 6 Jan 10 15:20. Carbon flotation in ductile iron is caused when the foundry allows the Carbon Equilivant to exceed the ability of the magnesium to suppress graphite formation in the liquid. My experience suggests that limit is about 4.55 - 4.60 with moderate levels of magnesium 0.030 to 0.035%.
The conventionally measured hardness of graphitic irons is influenced by the graphite, especially in gray iron. Martensite micro hardness may be as high as 66 HRC, but measures as low as 54 HRC conventionally in gray iron (58 HRC in ductile). The critical temperature of iron is influenced (raised) by silicon content, not by carbon content.
Nov 03, 2016· Use of rare earths, high silicon and carbon contents, and low cooling rates are reported as possible reasons for formation of chunky graphite in ductile iron castings. The understanding of this graphite degeneration is however limited, and the above conclusions are still controversial. To get further insight into this topic, ductile cast iron melts have been …
RELATIONSHIP BETWEEN COOLING RATE AND MICROSEGREGATION IN BOTTOM-CHILLED DIRECTIONALLY SOLIDIFIED DUCTILE IRONS W.S. Changa, C.M. Lina, b, * aDepartment of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan b Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, …
The article also talks about the effects of composition, graphite shape, and section size on the mechanical properties of ductile iron. Tables and graphs provide helpful information on the tensile properties, compressive properties, torsional properties, damping capacity, impact properties, fracture toughness, fatigue strength, and elevated ...
Ductile iron—also referred to as spheroidal or nodular iron—is actually a group of irons that exhibit high strength, flexibility, durability, and elasticity due to their unique microstructure. Cast ductile iron normally contains over 3 percent carbon; it can …
Graphite floatation This is caused when large, low density graphite nodules are formed during the solidification of thick section or otherwise slow cooling castings. The nodules, being of a lower density than the matrix, tend to float towards the surface of the casting and thus can have a negative effect on the mechanical properties (and ...
The unique step in the processing of ductile iron is the nodularization of graphite. This is the step where magnesium is added to the molten alloy to create a residule Mg level of approximately 0.03-0.06%, which is the amount necessary to cause graphite to form spheroids.
NODULARISERS Description of a structure should follow the convention Form : Distribution : Size, e.g. Type IA4 for a grey cast iron Type VI5 for a ductile iron Elkem manufactures and markets a range of high quality nodularising alloys to …
graphite floatation, spiky graphite and nodule alignment. - Those related to inclusions/abnormalities within the matrix, such as flake graphite surfaces, slag inclusions, ... has a marked effect on the shrinkage tendency of ductile irons. Foundries operating at the higher end of the magnesium range, 0.05% or above, will find that the iron is ...
- The outstanding properties of ductile iron are due to a nodular or spheroidal form of precipitated graphite in the microstructure. - This favorable nodular graphite shape is obtained by treating with magnesium to retain residual Mg content within narrow control limits, then inoculating with ferrosilicon to nucleate that graphitization.
coarse "potato" graphite formed, as shown in Figure 3. The so-called graphite flotation was not observed in high-Si cast iron, even for such a high-CE examined here, because the carbon content (less than 3.50%) was probably not high enough to reach the critical value for graphite floatation. If the CE is too low, there is probably
Chunky graphite formation in ductile cast irons: effect of silicon, carbon and rare earths Use of rare earths, high silicon and carbon contents, and low cooling rates are reported as possible reasons for for-mation of chunky graphite in ductile iron castings. The un-derstanding of this graphite degeneration is however lim-
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