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Muhmond, Haji MuhammadORCID iD iconorcid.org/0000-0003-3579-8748
Publications (2 of 2) Show all publications
Muhmond, H. M. & Fredriksson, H. (2018). Effect of the cooling rate on the graphite nodule count and size distribution in nodular cast iron. In: 11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017: . Paper presented at 11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jonkoping, Sweden, 4 September 2017 through 7 September 2017 (pp. 45-53). Trans Tech Publications, 925
Open this publication in new window or tab >>Effect of the cooling rate on the graphite nodule count and size distribution in nodular cast iron
2018 (English)In: 11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Trans Tech Publications, 2018, Vol. 925, p. 45-53Conference paper, Published paper (Refereed)
Abstract [en]

The graphite nodule count, size distribution and homogenization of the nodules distribution are the factors which are of more significance for the properties of the material. By just increasing the inoculants or Mg will not help to get rid of problems like the un-even size distribution and or increasing the nodule count. The cooling conditions of the melt prior to solidification and during solidification can control these two parameters to a large extent. In this research, it is more emphasized on the nucleation sequence of MgO particles and on the cooling rates. The nucleation of MgO at different temperatures and at different cooling rates was found to have a great influence on the nodule size distribution and the homogenization of the microstructure. A mathematical model was derived to relate the Mg concentration in the liquid to the cooling rate, prior to solidification. The MgO particles count was calculated as a function of cooling rate. It was found that at higher cooling rates, MgO can be nucleated in multi steps during cooling process, which can increase the nodule count tremendously.

Place, publisher, year, edition, pages
Trans Tech Publications, 2018
Series
Materials Science Forum, ISSN 0255-5476 ; 925
Keywords
Cooling rate, MgO nucleation, Micro segregation, Nodular cast iron, Nodule count, Nodule size distribution
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-238380 (URN)10.4028/www.scientific.net/MSF.925.45 (DOI)2-s2.0-85050037831 (Scopus ID)9783035710557 (ISBN)
Conference
11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jonkoping, Sweden, 4 September 2017 through 7 September 2017
Note

QC 20181119

Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2018-11-12Bibliographically approved
Muhmond, H. M. (2014). On the Inoculation and Graphite Morphologies of Cast Iron. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>On the Inoculation and Graphite Morphologies of Cast Iron
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Research was conducted to understand the nucleation mechanism of graphite flakes and nodules and the effect of various elements on the growth morphology of graphite. Investigations were started on flake graphite cast iron. The effect of S on the graphite morphology and MnS was experimentally analysed. The influence of various type of oxides on the growth morphology of MnS and their relation with the graphite growth morphology was studied carefully through series of experiments, and results were related to the thermodynamic calculations, performed to predict the nucleation of oxides and sulfides at any temperature. The calculations were supported by EDX analysis on particles in the samples, showing sequential nucleation of flake graphite. The austenite volume fraction and the dendrite growth orientations were affected by the addition of Al to the melt. The effect of aluminium oxide and sulfur was studied on the austenite growth morphology with the help of colour etching technique. Thermal analyses were performed to study the effect of sulfur content on austenite volume fraction and growth morphology using DSC. The latent heat of solidification and the rate of austenite formation was studied and related to the sulfur content in the alloy.

To study the effect of O and S on the graphite morphology, pure Fe-C alloy was prepared and strong de-oxidizers and de-sulfurizer (Mg, Ca and Sr) were tested. With the help of ion etching and polishing, we were able to reveal the graphite growth morphology. The morphological changes in the graphite were explained by relating it to the composition of the melt in regard of dissolved S and O in the melt. The effect of other trace elements such as S, F, O, N, P, B and Se, was also investigated by testing them on an ultra-pure Fe-C alloy. The possibility of substituting a foreign atom in the basal plane of graphite was analysed based on the bonding energy between C and the foreign atoms. The resulting change in the structure of the basal plane was studied using Avogadro software and the resulting model were compared with the experimental results. The basal plane of nodular, flake and undercooled graphite was studied with the help of HRTEM, which showed differences in the lattice spacing between different graphite morphologies. The latent heat measurement showed that flake graphite have higher energy than the undercooled or vermicular graphite. This research made us enabled to tell about the growth along c-plane in graphite and the reason behind the transition of graphite morphology.

The effect of inoculation temperature and inoculation sequence on the nodularity was studied. EDX analysis were performed and the results were compared to the thermodynamic calculations.  It was found that, the melt composition is controlling the graphite growth morphologies. Strong de-oxidizers and de-sulfurizer are necessary to reduce O and S to a level where it does not influence the graphite growth morphology. The effect of various elements on the activity of oxygen in the melt is calculated. High Al cast iron was also studied. The major problem associated with this type of alloy was that, the Mg was not effective in producing nodular graphite. Experiments showed that de-oxidizers stronger than Mg are required to increase the nodularity. Thermodynamic calculations showed that the activity of oxygen in the melt was changing strongly by increasing the Al content in the alloy. This was increasing the required oxygen level to nucleate MgO.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. p. 76
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-155545 (URN)978-91-7595-349-6 (ISBN)
Public defence
2014-11-28, B2, Brinelvagen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20141107

Available from: 2014-11-07 Created: 2014-11-07 Last updated: 2014-11-07Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-3579-8748

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