In this paper results of microstructural observations for series of CuZn39Pb2 alloys produced from qualified scraps are presented. The individual alloy melts were differentiated in terms of thermal parameters of continuous casting as well as refining methods and modifications. Structural observations performed by SEM and TEM revealed formation of different types of intermetallic phases including “hard particles”. EDS results show that “hard particles” are enrich in silicon, phosphorus, iron, chromium and nickel elements. Additionally, formation of Al-Fe-Si and Al-Cr in alloy melts was observed as well. It was found that quantity and morphology of intermetallic phases strongly depends upon the chemical composition of raw materials, process parameters, modifiers and refining procedure applied during casting. It was observed that refining process results in very effective refinement of intermetallic phases, whereas modifiers, particularly carbon-based, results in formation of large particles in the microstructure.
This article discusses issues related to continuous casting of brass. The tested material was CuZn39Pb2 brass with the use of continuous casting and different parameters of the process. The position consists of a melting furnace with a graphite refining pot of about 4000 cm3 chuting capacity, a graphite crystallizer of 9,5 mm nominal diameter, a primary and secondary cooling system and an extracting system as well. The analysis was carried out in terms of technological parameters of the process and type of charge. Highlighted: feedrate ingot, number of stops, and technological temperatures. The surface quality of the obtained ingots and the structure were analyzed. The most favorable conditions were indicated and technological recommendations indicated. They have been distinguished for ingots for plasticity and other technologies. Favorable casting conditions are low feed and low temperature. Due to the presence of impurities coming from the charge it is disadvantageous to have Ni greater than 0.053% by mass, and Fe more than 0.075% by mass. It is recommended to maintain a high zinc content in the melt which is associated with non-overheating of the metal during casting and earlier melting.
Trial series of cast alloy MO59 obtained from qualified scrap was investigated. SEM and TEM of resulting precipitates were conducted. The SEM analysis demonstrated the dependence of silicon, phosphorus, iron, chromium and nickel in the composition of the so-called hard precipitates. TEM analysis showed the formation of phase AlFeSi and AlCr. Made studies have shown the important role of the composition of the batch melts brass CuZn39Pb2 type. The analysis of SEM and TEM resulting precipitates pointed to the formation of various forms of divisions, only one of which was described in the literature character of the so-called hard inclusions. The SEM studies demonstrated the dependence of the occurrence of inclusions rich in silicon, phosphorus, iron, chromium and nickel. In contrast, additional TEM analysis indicated the formation of AlFeSi phase type and AlCr. The results of the analyses referred to the structure of the batch. Due to the difficulty of obtaining recycled materials that do not contain these elements necessary to carry out further analyzes in the direction of defining the role of phosphorus in the formation of the so-called hard inclusions.
This article contains information concerning of the analysis the possibility of defining refinery qualities of the slag based thermophysical and thermodynamical data. The paper presents a model of slag refining processes and a method of determining the reduction capability of slag solutions. Slag was analysed with the use of the DTA methods for the brass melting conductions. The study of computer program including the satisfactory number of data there are used in to the design a modern device rotating head used for gas-slag refining. It was achieved that the refining gas and fluxes were distributed ever by the rotating head. High effectiveness of the gas-slag refining processes was proved for the brass.
The article describes the optimization of the melting brass. Brasses, as one of the most popular alloys of copper, deserve special attention in the context of the processes of melting, which in turn would provide not only products of better quality, but also reduce the cost of their production or refining. For this purpose, several studies carried out deriatographic (DTA) and thermogravimetric (TG) using derivatograph. The results were confronted with the program SLAG - PROP used to evaluate the physicochemical properties of the coatings extraction. Based on the survey and analysis of the program can identify the most favorable physico - chemical properties, which should be carried out treatments. This allows for slag mixtures referred configurations oxide matrix containing specific stimulators of the reaction. Conducted empirical studies indicate a convergence of the areas proposed by the application. It should also be noted that the program also indicates additional areas in which to carry out these processes would get even better, to optimize the melting process, the results.
Source/filter models have frequently been used to model sound production of the vocal apparatus and musical instruments. Beginning in 1968, in an effort to measure the transfer function (i.e., transmission response or filter characteristic) of a trombone while being played by expert musicians, sound pressure signals from the mouthpiece and the trombone bell output were recorded in an anechoic room and then subjected to harmonic spectrum analysis. Output/input ratios of the signals’ harmonic amplitudes plotted vs. harmonic frequency then became points on the trombone’s transfer function. The first such recordings were made on analog 1/4 inch stereo magnetic tape. In 2000 digital recordings of trombone mouthpiece and anechoic output signals were made that provide a more accurate measurement of the trombone filter characteristic. Results show that the filter is a high-pass type with a cutoff frequency around 1000 Hz. Whereas the characteristic below cutoff is quite stable, above cutoff it is extremely variable, depending on level. In addition, measurements made using a swept-sine-wave system in 1972 verified the high-pass behavior, but they also showed a series of resonances whose minima correspond to the harmonic frequencies which occur under performance conditions. For frequencies below cutoff the two types of measurements corresponded well, but above cutoff there was a considerable difference. The general effect is that output harmonics above cutoff are greater than would be expected from linear filter theory, and this effect becomes stronger as input pressure increases. In the 1990s and early 2000s this nonlinear effect was verified by theory and measurements which showed that nonlinear propagation takes place in the trombone, causing a wave steepening effect at high amplitudes, thus increasing the relative strengths of the upper harmonics.
The article deals with ultrasonic testing possibilities of the copper alloy centrifugal casts. It focused on the problems that arise when testing of castings is made of non-ferrous materials. Most common types of casting defects is dedicated in theoretical introduction of article. Ultrasonic testing technique by conventional ultrasound system is described in the theoretical part too. Practical ultrasonic testing of centrifugal copper alloy cast - brass is in experimental part. The experimental sample was part of centrifugally cast brass ring with dimensions of Ø1200x34 mm. The influence of microstructure on ultrasonic attenuation and limitations in testing due to attenuation is describes in experimental part. Conventional direct single element contact ultrasound probe with frequencies of 5 MHz, 3.5 MHz and 2 MHz were used for all experimental measurements. The results of experimental part of article are recommendations for selecting equipment and accessories for casting testing made of non-ferrous metals.
Some metallographic studies performed on the basis of the massive forging steel static ingot, on its cross-section, allowed to reveal the following morphological zones: a/ columnar grains (treated as the austenite single crystals), b/ columnar into equiaxed grains transformation, c/ equiaxed grains at the ingot axis. These zones are reproduced theoretically by the numerical simulation. The simulation was based on the calculation of both temperature field in the solidifying large steel ingot and thermal gradient field obtained for the same boundary conditions. The detailed analysis of the velocity of the liquidus isotherm movement shows that the zone of columnar grains begins to disappear at the first point of inflection and the equiaxed grains are formed exclusively at the second point of inflection of the analyzed curve. In the case of the continuously cast brass ingots three different morphologies are revealed: a/ columnar structure, b/ columnar and equiaxed structure with the CET, and c/ columnar structure with the single crystal formation at the ingot axis. Some forecasts of the temperature field are proposed for these three revealed morphologies. An analysis / forecast of the behavior of the operating point in the mold is delivered for the continuously cast ingot. A characteristic delay between some points of breakage of the temperature profile recorded at the operating point and analogous phenomena in the solidifying alloy is postulated.
Experimental observations of the steel morphology as well as measurements of the solutes concentration in the macro-scale were made on the basis of the vertical cut at the mid-depth of the 15-tons steel forging ingot serially produced in one of the steel plant in Poland. Experimental observations of the morphology accompanied by the measurements of the Peclet Number were also made on the cross-section of the continuously cast brass ingots serially produced in the copper / brass industry in Poland. The performed measurements allowed to work out some maps of the alloying elements segregation for the longitudinal section of the steel static ingot and a Growth Law for the columnar grains formation in the brass ingots. The marginal stability criterion has been applied to the last mentioned development / description. Some suggestions for the micro-segregation measurement mode in the columnar structure are derived.
An innovative method for determining the structural zones in the large static steel ingots has been described. It is based on the mathematical interpretation of some functions obtained due to simulation of temperature field and thermal gradient field for solidifying massive ingot. The method is associated with the extrema of an analyzed function and with its points of inflection. Particularly, the CET transformation is predicted as a time-consuming transition from the columnar- into equiaxed structure. The equations dealing with heat transfer balance for the continuous casting are presented and used for the simulation of temperature field in the solidifying virtual static brass ingot. The developed method for the prediction of structural zones formation is applied to determine these zones in the solidifying brass static ingot. Some differences / similarities between structure formation during solidification of the steel static ingot and virtual brass static ingot are studied. The developed method allows to predict the following structural zones: fine columnar grains zone, (FC), columnar grains zone, (C), equiaxed grains zone, (E). The FCCT-transformation and CET-transformation are forecast as sharp transitions of the analyzed structures. Similarities between steel static ingot morphology and that predicted for the virtual brass static ingot are described.
The Structural Peclet Number has been estimated experimentally by analyzing the morphology of the continuously cast brass ingots. It allowed to adapt a proper development of the Ivantsov’s series in order to formulate the Growth Law for the columnar structure formation in the brass ingots solidified in stationary condition. Simultaneously, the Thermal Peclet Number together with the Biot, Stefan, and Fourier Numbers is used in the model describing the heat transfer connected with the so-called contact layer (air gap between an ingot and crystallizer). It lead to define the shape and position of the s/l interface in the brass ingot subjected to the vertical continuous displacement within the crystallizer (in gravity). Particularly, a comparison of the shape of the simulated s/l interface at the axis of the continuously cast brass ingot with the real shape revealed at the ingot axis is delivered. Structural zones in the continuously cast brass ingot are revealed: FC – fine columnar grains, C – columnar grains, E – equiaxed grains, SC – single crystal situated axially.