Papers by Keyword: Bronze

Abstract: Several Roman bronze objects were confiscated from a digger, which had been collected illegally at the archaeological site of Burg, Burgenland. Since these parts are archaeologically worthless, they were allowed to be examined with destructive analysis methods. The investigative results of five parts are presented. The surface of the parts is covered with a green patina which contains mainly Cu and smaller amounts of Sn, Pb, P, Ca, Al, S and Fe. If XRF analyses are performed, it must be taken into account that elements such as Sn accumulate in the patina. The average XRF analyses of the hook showed a content of 0.8 wt.% Sn and about 2 wt.% Pb, but in the fibular parts and the button up to 42 wt.% Pb were detected. Due to very different compositions of the samples, the microstructures are also appropriate miscellaneous. It is possible to distinguish between cast, recrystallized and deformed microstructures. These investigations show that the Roman metallurgist used a wide variety of copper alloys, because raw and recycled materials were probably processed together.

Abstract: In the region of Inzersdorf ob der Traisen in Lower Austria, 273 cremation graves from the late Bronze Age (ca. 1300–800 BC) were recovered. Also, various bronze artefacts were found in some graves, including a button which was analyzed by metallography. It should be determined how the button was manufactured, for example by casting or soldering, and microstructural changes can be detected due to temperature effects by cremation. The button is made of bronze whose composition was determined by XRF: 87 wt.% Cu, 9 wt.% Sn and 1 wt.% Pb. The microstructure of the bronze clearly shows a temperature influence during cremation. The bronze microstructure is recrystallized as well as parts were melted, causing oxidation at the grain boundaries. Also, some areas of the bronze show small shrink holes. Further corrosion took place during long-term storage of the button in the soil.

Abstract: In the Bronze Age several possibilities for tin bronze production were available, namely direct from copper and cassiterite ore or by alloying copper with metallic tin. Cassiterite ores from two sources, Cornwall and Schlaggenwald, were available. It has to be noted that cassiterite from Schlaggenwald contained about 25 wt. % WO₃, presumably as wolframite. For the experiments, copper was melted at 1090 °C, covered with charcoal and then cassiterite and again charcoal was added. As is known from Sn smelting, the presence of tungsten reduces the yield of Sn. Thus, in our experiments the Sn content in the bronze was reduced. It can be confirmed by these experiments that the direct production of tin bronzes from copper and cassiterite ore is possible. In the Bronze Age the negative effect of tungsten should not have played a role, because at that time only the cassiterite deposits of Cornwall were known in Europe.

Abstract: Copper is a widely used material in various industries due to its properties like good corrosion resistance, thermal and electrical conductivity, stability at high temperatures, etc. To increase the mechanical and tribological properties, additional reinforcement should be added to the copper matrix. Adding tin into copper will result in the formation of bronze which is stronger and harder than either of the pure metals. This study deals with the comparative study of mechanical and tribological properties of microwave sintered and conventionally sintered Cu-6Sn. The mechanical properties of Cu-6Sn processed through powder metallurgy are compared with that of Cu-6Sn processed through casting. Hardness and wear resistance was observed to be higher for conventionally sintered specimens. Microwave sintered Cu-6Sn exhibit enhanced mechanical properties compared to Cu-6Sn processed through casting.

Abstract: The present paper analyzes the differences in behavior and resistance to erosion through vibrating cavitation, between the bronze structures CuSn-12C resulting from two volumetric thermal treatments of hardening and tempering. The analysis was performed on the basis of macro and microscopic images, as well as on the basis of the histogram in which the values ​​of the reference parameters used in the laboratory custom and prescribed by the international norms ASTM G32-2016 are compared. This shows the dependence of the degree of erosion as a function of the temperature of tempering heat treatment, after hardening, as a result of microstructural changes and the hardness of the surface attacked by cavitation. The experimental research is performed on the standard vibrating device within the Cavitation Erosion Research Laboratory of the Politehnica University of Timișoara.

Abstract: The article describes the features of the process of casting copper alloys in the chill mold. The main properties of alloys depending on the content of various components in it are revealed. The main negative factors leading to a decrease in the casting properties of the process, as well as the quality of the castings obtained, are indicated. Based on the information and analytical review, possible options for improving the efficiency of the process are identified. These include: alloying, refining, modification, the use of various one-time coatings, the use of heat treatment of castings. The use of hard coatings applied by the method of physical vapor deposition in order to increase the efficiency of the entire casting process is proposed.

Abstract: The paper presents the results of the research on the vibration cavitation erosion of the CuSn12-C bronze, subjected to the volumetric heat treatment of quenching to 700 °C, with water cooling, followed by tempering to 250 °C, with slow cooling in the air. The applied heat treatment shows the improvement of the behavior and the resistance to the cavitation erosion, compared to the initial state, of molded semi-finished product. The evaluation of the behavior and the resistance to the cavitation erosion is made by comparing the value of the parameters MDEmax, Rcav and Rz with those of the delivery state, as well as on the comparison of the characteristic curves MDE(t) and MDER(t) with those of the CuNiAl I-RNR bronze (used at propeller casting). The tests were conducted on the vibrating apparatus with piezoceramic crystals from the Cavitation Laboratory of the Polytechnic University of Timisoara.

Abstract: This paper is devoted to the possibility of using tin as an alloying element in a copper alloy for the contact wire manufacture for high-speed electrified railways. To this end, laboratory experiments were carried out to determine the effect of tin on the structure, mechanical and electrical properties of samples, made of low-alloy system Cu-Sn alloys, under the cold deformation. Cast rods and rolled billets of CuSn0,2, CuSn0,4 and CuSn0,6 alloys are made. The cast rods macrostructure is studied. The analysis showed that with the introduction of tin into copper, there is no zone of columnar crystals in the macrostructure. Moreover, it was found that grains of α-solid solution of tin in copper have a shape close to equiaxial. A structure analysis of rolled billets showed that an increase in the deformation degree leads to grinding of crystalline grains. The mechanical properties of rolled billets were determined: ultimate tensile strength σ_U, offset yield strength σ_0.2 and elongation δ₅₀. The dependence of the electrical resistivity of rolled billets on the deformation degree and the tin content in the alloy is determined. Еhe higher the tin content in the alloy and the deformation degree is, the higher is the electrical resistivity. The electrical resistivity of samples, made of CuSn0.2 and CuSn0.4 alloys, coincides with the GOST R 55647-2018 requirements. The laboratory studies have shown that tin-containing copper alloys (Sn is up to 0.4 wt. %) can be recommended as a material for the manufacture of contact wire.

Abstract: The article presents the results of pilot-industrial experiments in the field of manufacturing technology of contact wire made of Cu-Sn alloys. Cast rods with a diameter of 20 mm, made of CuSn0.04, CuSn0.1, CuSn0.2, CuSn0.3, CuSn0.4 alloys, were obtained in a continuous casting plant on an Upcast system. Cast rods were deformed using a Conform technology, and extruded billets with a diameter of 18 and 20 mm were produced, which were subsequently drawn on a shaped contact wire with a cross section of 100 mm². Cast rods macrostructure and microstructure were studied. The macrostructure quantitative assessment of samples was studied in a cross and longitudinal section. A plot of the effect of the tin content in the alloy on the average grain area in cross section is obtained. An increase in the tin content in the alloy leads to a decrease in the average grain area. An analysis of the rod microstructure in a cross section showed that the structure is a grain of an α-solid solution of tin in copper, and the grain boundaries are thin and clean. After deformation by Conform technology a uniform fine-grained structure is ensured. The effect of the tin content in the alloy on the Brinell hardness of cast billets, made by Conform technology, is determined. An increase in the tin content in the alloy leads to an increase in the hardness of both cast and deformed billets. The microstructure analysis of the contact wire in the cross section is carried out. The mechanical and electrical properties of the contact wire with a cross section of 100 mm² are determined. An analysis of the results showed when the tin content in the alloy is up to 0.4 wt. %, the required level of mechanical and electrical properties of the contact wire is not provided. It may be necessary to change the size of the initial billet before drawing or to increase the tin content in the alloy more than 0.4 wt. %.

Abstract: Bronze-based composite materials are well known for use as friction materials. They are produced by powder metallurgy techniques from bronze powder, which acts as a matrix, and various friction modifying additives. The objective of this work was to study the effect of compaction pressure and sintering time on the properties of the unmodified bronze matrix. The bronze powder used was prealloyed with a composition of Cu-10Sn. The specimens were pressed by uniaxial die compaction with pressures of 282 to 339 MPa. The sintering experiments were conducted in an alumina tube furnace at 800 °C with sintering times of 30, 45, and 60 min under a vacuum pressure of 2.25x10^-2 Torr. From the results, it was found that the density of the samples increased with increasing compaction pressure. A microstructural examination of the samples for the different sintering times showed them to look very similar. Finally, the highest sintered density of 7.30 g/cm³ was obtained at 800 °C for 60 min.