Specialized metallurgical processes – compositions for use therei – Processes – Process control responsive to sensed condition
Patent
1997-11-28
1999-04-06
Batten, Jr., J. Reed
Specialized metallurgical processes, compositions for use therei
Processes
Process control responsive to sensed condition
164 41, 164 571, C22C 3308, G01N 1302, G01N 3320
Patent
active
058912134
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase of international application PCT/SE96/00659, filed May 21, 1996 which designated the U.S.
BACKGROUND OF THE INVENTION
The present invention relates to a new method for predicting the nucleation and growth of graphite crystals during the solidification of cast irons.
WO-A1-86/01755 relates to such a method. A sample from a bath of molten iron is permitted to solidify during 0.5 to 10 minutes. The temperature is recorded simultaneously by two temperature responsive means, one of which is placed in the center of the sample and the other in the immediate vicinity of the vessel wall. The number and shape of the graphite particles which constitute the graphite phase is assessed in relation to known reference values by aid of recorded values of supercooling at the vessel wall, the recalescence at the vessel wall, the difference between the temperature at the vessel wall and at the center of the vessel and the maximum slope of the temperature time curve during the period of constant eutectic growth temperature at the center. The method can be used for calculating the amounts of inoculants and graphite structure modifiers that have to be added or removed in order to obtain a cast iron comprising a desired form of cast iron, such as flaky graphite iron, compacted graphite iron (CGI) and spheroidal graphite iron (SGI).
The method according to WO-A1-86/01755 produces excellent results, but it also has some drawbacks. The amount of time required for the determination, up to 10 minutes may be rather high, and the measurement per se is also rather complicated. Hence, there is a need for a quick, simple and reliable method for predicting the nucleation and growth of graphite crystals during the solidification of cast irons.
SUMMARY OF THE INVENTION
The aforesaid problem in connection with producing cast irons having a certain desired morphology of graphite crystals and containing graphite shape modifiers and/or inoculants, is solved by a method in accordance with the invention, according to which: iron; of batches of molten iron that are known to solidify as different forms of cast iron.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to the accompanying drawings according to which:
FIG. 1 is a graphic representation of the surface tension of liquid iron as a function of the concentration of the highly surface active elements, oxygen, sulfur and selenium, and standard components of cast irons which are less surface active such as nitrogen, phosphorus and carbon;
FIGS. 2A and 2B illustrate the atomic structure of graphite and defines the A-axis and C-axis directions of growth of graphite crystals; and
FIG. 3 is a schematic illustration of the measuring equipment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The method according to the present invention is based on an accurate measurement of the surface tension of the liquid iron following base treatment with inoculants and graphite shape modifiers such as magnesium. As is shown in FIG. 1, it is well-known (See P. Kzakevitch and G. Urbain: J. of the Iron and Steel Institute (JISI), Vol. 186, 1957, pp. 167-170.) that the surface tension of liquid iron changes with varying contents of surface active elements such as sulfur and oxygen. As the concentration of these elements increases, the surface tension of liquid iron decreases thus allowing the formation of elongated graphite crystals with a high surface area-to-volume ratio such as is found in conventional grey cast irons. With lower concentrations of sulfur and oxygen, the surface tension of the liquid iron increases thus favoring the formation of spheroidal graphite crystals which have a minimized surface area-to-volume ratio. Compacted graphite crystals, which are arguably a three-dimensionally growth-distored form of flake graphite morphology, are known to grow preferentially at intermediate values of liquid iron surface tension.
While several theories regarding the growth mechanism and ultimate shape of graphite ha
REFERENCES:
patent: 3284192 (1966-11-01), Larson et al.
patent: 3765227 (1973-10-01), Campbell et al.
patent: 4246026 (1981-01-01), Stefanescu et al.
patent: 4449700 (1984-05-01), Erpelding
patent: 5305815 (1994-04-01), Pan Ping et al.
patent: 5615730 (1997-04-01), Hiraoka et al.
Kozakevitch et al: "Surface Tension of Pure Liquid Iron, Cobalt, and Nickel at 1550.degree. C.", Journal of the Iron and Steel Institute, Jun. 1957, pp. 167-173.
Mizina et al: "Surface tension of complex inoculants and their efficency for smelting cast iron", Dialog Information Services, file 21, Metadex, Dialog accession no. 1848281, Metadex Accession No. 199501-45-0034, Rasplavy, vol. 1, pp. 88-91, Jan.-Feb. 1994, (abstract only).
Kul'Bovskii: "Factors Influencing Graphite Particle Form in Cast Iron", Soviet Castings Technolgy (Now: Russian Castings Technology)) See also: Liteinoe Proizvodstavo). Dialog Information Services, File 32, Metadex, Dialog accession No. 1814414, Metadex accession No. 199402-51-0166, vol. 2, pp. 11-12, 1991 (abstract only).
Herfurth: "Investigation of the effect of various allloying additions on the surface tension of liquid cast iron to establish correlations between surface tension and the formation of various forms of graphite", Freiberger Forsch B 105, 1966, pp. 267-310, see pp. 281-288 and pp. 299-307 (abstract).
Nosov et al: The Surface Tension and Thermo-physical Properties of Cast Irons Modified With Magnesium, Yttrium, Gadolinium, and Zicronium, Fiz-Khim. Issled. Metall. Protessov, vol. 10, pp. 60-63, 1982, Dialog Information Serices, File 32, Metadex, Dialog Accession No. 888163, Metadex Accession No. 84-320362 (Abstract).
Aleksandrov et al: "A study of Graphite Formation in Cast Iron: Methods of Controlling Cast Iron Properties at the Casting Stage", Fonderia Ital., 27 (4) 103-107, Apr. 1978 (abstract).
Batten, Jr. J. Reed
Sinter-Cast AB
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