New developments in high quality grey cast irons
The paper reviews original data obtained by the present authors, revealed in recent separate publications, describing specific procedures for high quality grey irons, and reflecting the forecast needs of the worldwide iron foundry industry. High power, medium frequency coreless induction furnaces ar...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Foundry Journal Agency
2014-07-01
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| Series: | China Foundry |
| Subjects: | |
| Online Access: | http://www.foundryworld.com/uploadfile/2014090237114725.pdf |
| _version_ | 1811242470472679424 |
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| author | Iulian Riposan Mihai Chisamera Stelian Stan |
| author_facet | Iulian Riposan Mihai Chisamera Stelian Stan |
| author_sort | Iulian Riposan |
| collection | DOAJ |
| description | The paper reviews original data obtained by the present authors, revealed in recent separate publications, describing specific procedures for high quality grey irons, and reflecting the forecast needs of the worldwide iron foundry industry. High power, medium frequency coreless induction furnaces are commonly used in electric melting grey iron foundries. This has resulted in low sulphur (<0.05wt.%) and aluminium (<0.005wt.%) contents in the iron, with a potential for higher superheating (>1,500 °C), contributing to unfavourable conditions for graphite nucleation. Thin wall castings are increasingly produced by these electric melt shops with a risk of greater eutectic undercooling during solidification. The paper focused on two groups of grey cast irons and their specific problems: carbides and graphite morphology control in lower carbon equivalent high strength irons (CE=3.4%-3.8%), and austenite dendrite promotion in eutectic and slightly hypereutectic irons (CE=4.1%-4.5%), in order to increase their strength characteristics. There are 3 stages and 3 steps involving graphite formation, iron chemistry and iron processing that appear to be important. The concept in the present paper sustains a threestage model for nucleating flake graphite [(Mn,X)S type nuclei]. There are three important groups of elements (deoxidizer, Mn/S, and inoculant) and three technological stages in electric melting of iron (superheat, pre-conditioning of base iron, final inoculation). Attention is drawn to a control factor (%Mn) x (%S) ensuring it equals to 0.03 – 0.06, accompanied by 0.005wt.%–0.010wt.% Al and/or Zr content in inoculated irons. It was found that iron powder addition promotes austenite dendrite formation in eutectic and slightly eutectic, acting as reinforcement for the eutectic cells. But, there is an accompanying possible negative influence on the characteristics of the (Mn,X)S type graphite nuclei (change the morphology of nuclei from polygonal compact to irregular polygonal, and therefore promote chill tendency in treated irons). A double addition (iron powder + inoculant) appears to be an effective treatment to benefit both austenite and graphite nucleation, with positive effects on the final structure and chill tendency. |
| first_indexed | 2024-04-12T13:51:46Z |
| format | Article |
| id | doaj.art-0b39587c5db549ca9655d7b252094422 |
| institution | Directory Open Access Journal |
| issn | 1672-6421 1672-6421 |
| language | English |
| last_indexed | 2024-04-12T13:51:46Z |
| publishDate | 2014-07-01 |
| publisher | Foundry Journal Agency |
| record_format | Article |
| series | China Foundry |
| spelling | doaj.art-0b39587c5db549ca9655d7b2520944222022-12-22T03:30:30ZengFoundry Journal AgencyChina Foundry1672-64211672-64212014-07-01114351364New developments in high quality grey cast ironsIulian Riposan0Mihai Chisamera1Stelian Stan2POLITEHNICA University of Bucharest, RomaniaPOLITEHNICA University of Bucharest, RomaniaPOLITEHNICA University of Bucharest, RomaniaThe paper reviews original data obtained by the present authors, revealed in recent separate publications, describing specific procedures for high quality grey irons, and reflecting the forecast needs of the worldwide iron foundry industry. High power, medium frequency coreless induction furnaces are commonly used in electric melting grey iron foundries. This has resulted in low sulphur (<0.05wt.%) and aluminium (<0.005wt.%) contents in the iron, with a potential for higher superheating (>1,500 °C), contributing to unfavourable conditions for graphite nucleation. Thin wall castings are increasingly produced by these electric melt shops with a risk of greater eutectic undercooling during solidification. The paper focused on two groups of grey cast irons and their specific problems: carbides and graphite morphology control in lower carbon equivalent high strength irons (CE=3.4%-3.8%), and austenite dendrite promotion in eutectic and slightly hypereutectic irons (CE=4.1%-4.5%), in order to increase their strength characteristics. There are 3 stages and 3 steps involving graphite formation, iron chemistry and iron processing that appear to be important. The concept in the present paper sustains a threestage model for nucleating flake graphite [(Mn,X)S type nuclei]. There are three important groups of elements (deoxidizer, Mn/S, and inoculant) and three technological stages in electric melting of iron (superheat, pre-conditioning of base iron, final inoculation). Attention is drawn to a control factor (%Mn) x (%S) ensuring it equals to 0.03 – 0.06, accompanied by 0.005wt.%–0.010wt.% Al and/or Zr content in inoculated irons. It was found that iron powder addition promotes austenite dendrite formation in eutectic and slightly eutectic, acting as reinforcement for the eutectic cells. But, there is an accompanying possible negative influence on the characteristics of the (Mn,X)S type graphite nuclei (change the morphology of nuclei from polygonal compact to irregular polygonal, and therefore promote chill tendency in treated irons). A double addition (iron powder + inoculant) appears to be an effective treatment to benefit both austenite and graphite nucleation, with positive effects on the final structure and chill tendency.http://www.foundryworld.com/uploadfile/2014090237114725.pdfgrey iron; S; Al; Zr; Ti; electric melting; furnace superheating; preconditioning; inoculation; graphite nucleation; graphite morphology; carbides; dendritic austenite; iron powder |
| spellingShingle | Iulian Riposan Mihai Chisamera Stelian Stan New developments in high quality grey cast irons China Foundry grey iron; S; Al; Zr; Ti; electric melting; furnace superheating; preconditioning; inoculation; graphite nucleation; graphite morphology; carbides; dendritic austenite; iron powder |
| title | New developments in high quality grey cast irons |
| title_full | New developments in high quality grey cast irons |
| title_fullStr | New developments in high quality grey cast irons |
| title_full_unstemmed | New developments in high quality grey cast irons |
| title_short | New developments in high quality grey cast irons |
| title_sort | new developments in high quality grey cast irons |
| topic | grey iron; S; Al; Zr; Ti; electric melting; furnace superheating; preconditioning; inoculation; graphite nucleation; graphite morphology; carbides; dendritic austenite; iron powder |
| url | http://www.foundryworld.com/uploadfile/2014090237114725.pdf |
| work_keys_str_mv | AT iulianriposan newdevelopmentsinhighqualitygreycastirons AT mihaichisamera newdevelopmentsinhighqualitygreycastirons AT stelianstan newdevelopmentsinhighqualitygreycastirons |