The graphite compactness degree in modified irons.
For the elaboration of grey cast irons we started from a metallic charge made up of synthetic pig irons (100%) (Riposan, Lupinca, 2006). Synthetic pig iron from the load have produced in an electric arc furnace with 6 to capacity, starting from the steel scraps. The steel scraps have been carefully selected regarding the chemical composition of additional elements. The correcting of the carbon content was made by adding graphite dust in the charge. The elaboration furnace used is an electric furnace with medium frequency induction, with a capacity of 250 kilos. For the compact modification we used a compact mag alloy from the FeSiMgCe(RE) category (RE: Ce, La, Nd, Pr) (~65%Ce). The graphitizing modification was made with two types of modifying substances: FeSi (~75%Si) and FeSiSr (~45%Si, ~0.8%Sr), by adding modifying substances on the "stream" of liquid cast iron, at the discharge in a casting pot.
The modified cast irons with compact graphite (ductile irons and compacted graphite irons) are used mainly for the obtaining of cast pieces for the engine construction industry. The research of compacted graphite irons and ductile irons are performed in our university ("Eftimie Murgu" University of Resita) from over 4 years, being a research domain of continuous interest. The practical stage of the research is performed in the casting in Foundry Plant of Engine Construction Plant of Resita (Lupinca, 2008).
In this study, we will use the notion of compact graphite for the separations of nodular graphite and for the separations of vermicular graphite.
In this paper we have presented the results for four charges, whose treatment technology in a liquid state in order to obtain a modification was made in a different way regarding the quantities of the modifiers used. Thus:
--the charges 1 and 2 were treated with greater quantities (identical for the two charges) of nodulizing modifier, FeSiMgCe(RE) and with same amount of graphitizing modifiers, but different from the chemical composition point of view: FeSi--charge 1 and FeSiSr--charge2;
--the charges 3 and 4 were treated with smaller quantities (identical for two charges) of nodulizing modifier, FeSiMgCe(RE) and with the same amount of graphitizing modifier (as for charges 1 and 2): FeSi - charge 3 and FeSiSr charge 4.
In this study we have analysed and we have presented only the graphite morphology, respectively the dimensions of the graphite separations, resulted after modification. This results about the graphite morphology of this modified irons is different from other results have been presented in other paper (Lupinca, 2007).
2. EXPERIMENTAL RESULTS
[FIGURE 1 OMITTED]
The graphite morphology, respectively the shape and dimensions of the graphite separations from the four cast irons charges modified with FeSiMgCe(RE) + FeSi and with FeSiMgCe(RE) + FeSiSr, were analyzed according to ISO 945. Thus:
* The graphite separations obtained from charge 1 of modified cast iron are nodular graphite separations type 5-6 (0.12H-0.03mm) and in which the smaller dimensions of graphite are predominant (0.03 H-0.06mm) (type 6) (~75%) (Fig. 1.A);
* From charge 2 of modified cast iron we also obtained nodular graphite separations, but with dimensions of 0.12H/0.015mm (type 5H/7); graphite nodules of very small dimensions (0.015H/0.03mm) (type 7) are found in a greater concentration (~60%) (Fig. 1.B);
* In charge 3 of modified cast iron, we have obtained graphite vermicular separations in a greater concentration (>75%), but also graphite nodular separations, both being type 5 (0.06H/0.12mm) (Fig. 1.C);
* Synonym with charge 3, the graphite separations in charge 4 of modified cast iron are also presented, but the compacted graphite separations are predominant, type 6 (0.03H/0.06mm) (Fig. 1.D);
* This shape analysis of compact graphite separations of modified cast irons, can show us that the use of the nodulizing modifier FeSiMgCe(RE) in a greater concentration (1.5/1.7) at the modification of cast grey irons, leads to obtaining of nodular graphite separations, respectively to the producing of ductile cast irons (Fig. 2);
* The use of the same type of modifying nodulizing substance in a lower concentration (0.9/ 1.1%) at the modification of grey cast irons, leads to the obtaining of compacted graphite cast irons (>75% vermicular graphite separations and <25% sferoidal graphite separations) (Fig.2);
* Because the graphitizing modifiers are used in the modification of cast irons in the same proportion, the character of the graphite separations is given by the quantity of nodulizing graphite used;
* But, the use the graphitizing modifier type FeSiSr in the casting of pig irons leads to a decrease in dimensions of the compact graphite separations (type 7, respectively type 6) (charge 2 and 4), in comparation to the graphitizing modifier type FeSi which leads to the obtaining of compact graphite separations, which slightly greater dimensions (type 5) (charge 1 and 3) (Fig. 1);
* According to these studies and considering a other studies (Riposan, 1995), the sferoidal graphite separations (100%) in the modified cast irons are obtained when treating with the nodulizing modifier FeSiMgCe(RE) in a greater concentration than 1.5% and with graphitizing modifiers FeSi and FeSiSr, in a lower concentration of 0.9%;
* Also, for the adding of nodulizing modifier FeSiMgCe(RE) lower than 1.0% and the same adding of graphitizing modifiers we obtain in the structure of the modified cast irons over 75% compacted graphite separations;
* Regarding the type of modifier used when treating grey cast irons, we have to mention that if a higher fineness is wanted, we can use the treatment method with the modifier FeSiSr, and if the obtaining of some compacted graphite separations with a lower degree of fineness is wanted, we may apply the technology of the use of graphitizing modifier type FeSi;
* These specifications may be applications in the case of the use a production technology of modified grey cast irons to the studies presented.
* In the other paper (Lupinca, 2008) we have presented the results of the research about the modification of the cast iron with the same nodulizing modifiers (FeSiMgCe(RE)) (the same addition - >1,5%) and the same graphitizing modifiers (FeSiSr) (but, with different addition - 0,5% approximate), where we have obtained over 85% the compacted graphite separations concentration. So, if we want to obtain the compacted graphite irons (with over 90% compacted graphite separations concentration, we will must to treat the cast irons with lover 0,9% addition the nodulizing modifiers, FeSiMgCe(RE), and lover 0,6% addition the graphitizing modifiers, FeSiSr.
* So, the paper presents partial results of the study, taking in consideration the fact researches are still ongoing, using other compositions of the modifying substances introduced in liquid irons.
Riposan, I., a.a. (1995)., Study on the Graphite Compactness degree in Modified Cast Irons, Progess in Metallography, Ed. M. Kurz, M. Pohl Information Sgesellschaft, 1995 (EUROMET 1995), pp. 163-166, Germany
Riposan, I., Lupinca, C.I. (2006)., Producing of Synthetic Pig iron in Electric Arc Furnaces, The 4th Symposium with International Participation KOD2006, pp. 341-344, ISBN 86-85211-92-1, Palic, Serbia & Montenegro
Lupinca, C.I. (2007)., Studies about micrography of ductile irons, The 13th International Symposium on Metallography --Metallography 2007, 2-4 May 2007, Kosice, Slovakia, ISSN 1335-1532, Acta Metalurgica Slovaca, Rocnik 13, pp. 118-122
Lupinca, C.I. (2008)., The Influence of the Modifiers on the Compacted Graphite Iron Characteristics, Annals of DAAAM for 2008 & Proceedings of the 19th International Symposium, pp. 383-384, ISBN 978-3-901509-68-1 (ISSN 1726-9679), 22-25 Oct. 2008, Trnava, Slovakia, Published by DAAAM International, Vienna, Austria
Tab. 1. Chemical composition of the modified cast irons [%] Charge C Si Mn P S no. 1. 3.57 2.23 0.193 0.056 0.013 2. 3.65 2.25 0.194 0.057 0.016 3. 3.50 2.04 0.190 0.051 0.016 4. 3.58 2.05 0.190 0.052 0.013 Charge no. Cu Ni Cr Mo Mg 1. 0.27 0.044 0.076 0.069 0.0452 2. 0.27 0.045 0.073 0.070 0.0434 3. 0.14 0.100 0.110 0.002 0.0220 4. 0.13 0.100 0.110 0.001 0.0250 Tab. 2. The concentration of compact graphite in the modified cast irons [%] Graphite morphology Charge Nodular Vermicular no. graphite graphite (GG) (CG) 1. 100 -- 2. 100 -- 3. 25 75 4. 25 75 Fig. 2 Graphic representation of the nodular graphite (GG) separations and vermicular graphite (CG) separations in the modified cast irons [%] GG formatios and CG formatios report [%] Charge no. GG CG 1 100 0 2 100 0 3 25 75 4 25 75 Note: Table made from bar graph.
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|Author:||Lupinca, Cinca Ionel|
|Publication:||Annals of DAAAM & Proceedings|
|Date:||Jan 1, 2009|
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