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T. Szymczak

The Structure of the Silumin Coat on Alloy Cast Steels

The work presents the analysis results of the structure of the coat obtained by dipping in silumin AlSi5 of two grades of alloy cast steel: GX6CrNiTi18-10 (LH18N9T) and GX39Cr13 (LH14). The temperature of the silumin bath was 750±5°C, and the hold-up time of the cast steel element τ = 180 s. The absolute thickness of the coat obtained in the given conditions was g = 104 μm on cast steel GX6CrNiTi18-10 and g = 132 μm on GX39Cr13. The obtained coat consisted of three layers of different phase structure. The first layer from the base "g1" was constructed of the phase AlFe including Si and alloy additives of the tested cast steel grades: Cr and Ni (GX6CrNiTi18-10) and Cr (GX39Cr13). The second layer "g1" of intermetallic phases AlFe which also contains Si and Cr crystallizes on it. The last, external layer "g2" of the coat consists of the silumin containing the intermetallic phases AlFeSi which additionally can contain alloy additives of the cast steel. It was shown that there were no carbides on the coat of the tested cast steels which are the component of their microstructure, as it took place in the case of the coat on the high speed steels.

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T. Szymczak and Z. Kowalewski

Variations of Mechanical Parameters and Strain Energy Dissipated During Tension-Torsion Loading

The paper presents behaviour of materials under complex loading being combinations of torsion-reverse-torsion cycles superimposed on monotonic tensile deformation. The 2024 aluminium alloy, P91 steel and M1E copper were investigated under plane stress state using thin-walled tubular specimens. All tests were strain controlled and a total strain was less than 1%. An influence of torsion cycles on tensile characteristic was manifested by lowering of the proportional limit and yield point. This effect was increased with magnification of cyclic strain amplitude and in the case of copper a reduction of yield point was equal around 90%. A character of this effect was checked using the yield surface concept after each test. The papers also presents, variations of tangential hardening modulus and plastic strain energy dissipation.

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T. Rynarzewski and M. Szymczak

Open access

T. Szymczak

Abstract

The work presents the research results of the silumin coat structure applied on the carbidic alloy ductile iron with the metal matrix: pearlitic, bainitic and martensitic. The coats were made in the AlSi5 silumin bath at the temperature tk = 750±5°C. The holding time of cast iron element in the bath was τ = 180s. Irrespective of the kind of tested ductile iron the obtained coat consisted of three layers with a different phase composition. The first layer from the cast iron ground “g1`” is built from Fe4CSi carbide which contains selected alloy additives of the cast iron. On it the second layer “g1``” crystallizes. It consists of the AlFeSi inter-metallic phase which can appear in its pure form or contain a small quantity of the alloy additives of the cast iron. The last external part of the layer “g2” mainly consists of the hypo-eutectic phases of silumin. The AlFeSi inter-metallic phases in the form of free precipitations with a lamellar or faceted morphology can also appear there. These phases also can contain a small quantity of the alloy additives of the cast iron. More than that, in all the layers of the coat there are graphite precipitations. The phenomenon of graphite movement to the coat is caused by intensive dissolving of the cast iron element surface by the aluminum of the silumin bath.

Open access

T. Szymczak, G. Gumienny and T. Pacyniak

Abstract

The paper presents the results of hypoeutectic silumin 226 grade and silumin produced on its basis through the addition of V and Mo. Vanadium and molybdenum were added as the preliminary alloy AlV10 and AlMo8 in an amount providing the concentration of 0.1; 0.2; 0.3 and 0.4% V and Mo. TDA curves of tested silumins were presented; regardless of the chemical composition there were similar thermal effects. Pressure castings microstructure research revealed the presence in silumins with the addition of V and Mo phases do not occur in silumin without these additives. These phases have a morphology similar to the walled, and their size increases with increasing concentration of V and Mo. The size of the precipitates of these phases silumin containing 0.1% V and Mo does not exceed 10 microns, while 0.4% of the content of these elements increases to about 80 microns. Tests of basic mechanical properties of silumins were carried out. It has been shown that the highest values of tensile strength Rm = 295 MPa and elongation A = 4.2% have silumin containing approximately 0.1% V and Mo. Increasing concentrations of these elements causes a gradual lowering of the Rm and A values.

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T. Szymczak, G. Gumienny and T. Pacyniak

Abstract

The work presents the effect of strontium and antimony modification on the microstructure and mechanical properties of 226 silumin casts. The performed research demonstrated that strontium causes high refinement of silicon precipitations in the eutectic present in the microstructure of the examined silumin and it significantly affects the morphology of eutectic silicon from the lamellar to the fibrous one. Sr modification also causes an increase of: the tensile strength „Rm” by 12%; the proof stress „Rp0,2” by 5%; the unit elongation „A” by 36% and the hardness HB by 13%. Antimony did not cause a change in the microstructure of the silumin, yet it caused an increase in Rm and HB by 5%, in Rp0,2 by 7% and in A by 4%.

Open access

T. Szymczak, G. Gumienny and T. Pacyniak

Abstract

This paper presents the effect of the temperature and hold time in the holding furnace of 226 silumin on the characteristic quantities of TDA curves. The temperature of phase transformations and the cooling rate were tested.It has been shown that increasing both the hold time and the temperature in the holdingfurnace cause the decreasethe end ofα+Al9Fe3Si2+β and α+Al2Cu+βternary eutectics crystallizationtemperature in the tested silumin. This is due to the fact an increase in amounts of impurities as a result of reacting theliquid alloy with the gases contained in the air.It has been shown, however, that examined technological factors ofthe metal preparation do not cause systematic changes in the cooling rate.

Open access

T. Szymczak, G. Gumienny and T. Pacyniak

Abstract

The basic aim of this study is to investigate the effect of vanadium and tungsten on the crystallization process, microstructure and mechanical properties of silumin grade EN-AC 46000. The research involved a derivative thermal analysis DTA of the crystallization process, the metallographic analysis as well as the mechanical properties. The metallographic analysis was carried out on pressure die castings and made in the DTA probe. Vanadium and tungsten were added simultaneously to silumin in amount of approximately 0.1; 0.2; 0.3 and 0.4%. The DTA studies have shown the similar shape of all crystallization curves. It has been shown the additives of vanadium and tungsten in pressure die cast silumin can significantly increase its tensile strength as an well as elongation.

Open access

T. Szymczak, G. Gumienny, T. Pacyniak and K. Walas

Abstract

The work presents the results of the examinations of silumin 226 as well as a silumin produced on its basis containing a W and Mo addition introduced in the amount of 0.1; 0.2; 0.3 and 0.4% of both elements simultaneously. Investigations of the crystallization process of the silumins by the TDA method were conducted. Also, a microscopic analysis of their microstructure was performed and their basic mechanical properties were determined. Microstructure tests were made on casts produced in an TDA sampler as well as by the pressure method. The investigations exhibited a change in the course of crystallization of the silumin containing 0.3 and 0.4% W and Mo with respect to silumin 226 and the silumin with the addition of 0.1 and 0.2%. The presence of additional phases which did not occur in the case of lower addition contents was established in the silumin containing 0.3-0.4% W and Mo, regardless of the applied casting technology. The tests showed the possibility of increasing the tensile strength Rm, the proof stress Rp0,2 and the unit elongation A of the silumin as a result of a simultaneous introduction of the W and Mo addition. The highest values of Rm, Rp0,2 and A were obtained in the silumins with the additions of these elements within the range of 0.1-0.2% each.

Open access

T. Szymczak, G. Gumienny and T. Pacyniak

Abstract

The work presents the results of the investigations of the effect of the nitrogen (N2) refining time „τraf” and the gas output on the course of the crystallization process, the microstructure and the gassing degree of silumin 226 used for pressure casting. The refinement of the examined silumin was performed with the use of a device with a rotating head. The crystallization process was examined by way of thermal analysis and derivative analysis TDA. The performed examinations showed that the prolongation of the N2 refining time causes a significant rise of the temperature of the crystallization end of the silumin, „tL”, as well as a decrease of its gassing degree, „Z”. An increase of the nitrogen output initially causes an increase of the temperature „tL” and a drop of the gassing degree „Z”, which reach their maximal values with the output of 20 dm3/min. Further increase of the output causes a decrease of the value „tL” and an increase of „Z”. The examined technological factors of the refining process did not cause any significant changes in the microstructure of silumin 226.