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1

A New Flexible and Economic Technology for the Low Pressure Sand Casting of Steel Alloys

Krumm Steven, Scheidhauer Nico, Wolf Gotthard, Dommaschk Claudia

Journal of Casting & Materials Engineering

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2021

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Vol. 5, no. 3

45--52

EN

Low pressure casting is a very well established process for the casting of aluminium alloys. In the field of ferrous materials, however, the process has so far only found a few applications. The crucial reasons for this are the low flexibility and poor economic efficiency of the existing technologies. Since 2016, a new technology has been developed at the Foundry Institute of the TU Bergakademie Freiberg, in which an induction crucible furnace can be used as a melting unit and, in combination with a cover including a casting pipe, as a casting unit. The new technology stands out from existing low-pressure casting technologies for ferrous materials, particularly in terms of its flexibility and cost-effectiveness. The main focus of the activities was the development of a casting pipe as well as the verification of its lifetime, the elaboration and verification of process parameters and sequences as well as the upscaling of the technology for an industrial application. In all considerations, the focus was on both the technical feasibility and the economic efficiency of the process. The result is extensive expertise that can be used in the future to offer a finished product for industrial applications as a plug-and-play solution together with an induction furnace construction company.

2

The Influence of Wall Thickness and Mould Temperature on Structure and Properties of Thin Wall Ductile Iron Castings

Górny M., Kawalec M., Witek G., Rejek A.

Archives of Foundry Engineering

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2019

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iss. 2

55--59

EN

The excellent property combination of thin wall ductile iron castings (TWDI), including thin wall alloyed cast iron (e.g. austenitic TWDI) has opened new horizons for cast iron to replace steel castings and forgings in many engineering applications with considerable cost benefits. TWDI is considered as a potential material for the preparation of light castings with good mechanical and utility properties, the cost of which is relatively low. In this study, unalloyed and high Ni-alloyed (25% Ni) spheroidal graphite cast iron, with an austenitic metallic matrix were investigated. The research was conducted for thin-walled iron castings with 2, 3 and 5mm wall thickness, using different mould temperature (20°C, and 160°C) to achieve various cooling rates. The metallographic examinations i.e. characteristic of graphite nodules, metallic matrix, and primary grains of austenite dendrites (in high-nickel NTWDI) and mechanical properties were investigated. The study shows that homogeneity of the casting structure of thin-walled castings varies when changing the wall thickness and mould temperature. Finally, mechanical properties of thin-walled ductile iron castings with ferritic-pearlitic and austenitic metallic matrix have been shown.

3

The Effect of a Thin-Wall Casting Mould Cavity Filling Conditions on the Casting Surface Quality

Trytek A., Orłowicz A. W., Tupaj M., Mróz M., Markowska O., Bąk G., Abram T.

Archives of Foundry Engineering

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2016

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Vol. 16, iss. 4

222--226

EN

The paper presents results of metallographic examination of faults occurring in the course of founding thin-walled cast-iron castings in furan resin sand molds. A non-conformance of the scab type was Observed on surface of the casting as well as sand buckles and cold shots. Studied the chemical composition by means of a scanning electron microscope in a region of casting defects: microanalysis point and microanalysis surface. Around the observed defects discloses high concentration of oxides of iron, manganese and silicon. A computer simulation of the casting process has been carried out with the objective to establish the cause of occurrence of cold shots on casting surface. The simulation was carried out with the use of NovaFlow & Solid program. We analyzed the flowing metal in the mold cavity. The main reason for the occurrence of casting defects on the surface of the casting was gating system, which caused turbulent flow of metal with a distinctive splash stream of liquid alloy.

4

Structural gradient in a thin wall casting of ductile iron

Fraś E., Górny M.

Archives of Foundry Engineering

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2007

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Vol. 7, iss. 4

63-68

EN

In this paper a experimental and theoretical structural analysis of thin walled casting made of ductile iron is presented. The work shows that these castings posses a non-homogenous gradient structure associated with (i) the graphite nodule densities and (ii) the ferrite and cementite volume fractions. The microstructural inhomogeneities are attributed to sharp variations in the cooling rates along the length of the casting. The experimental investigations were made using of the castings with a 1.6 mm wall thickness, where the graphite nodule count, N_F and de fractions of ferrite, f_f and cementite eutectic, f_c were determined as a function of distance from the runner. It was found that the theoretical predictions were in good agreement with the experimental outcome. In particular, this work shows that it is possible to produce thin wall plate shaped castings made of nodular cast iron with wall thicknesses of 1.6 mm (without chills, cold laps, or misruns).