The article presents an example of analysis of the influence of selected parameters deriving from data acquisition in foundries on the occurrence of Gas porosity defects (detected by Visual testing) in castings of ductile cast iron. The possibilities as well as related effectiveness of prediction of this kind of defects were assessed. The need to rationally limit the number of possible parameters affecting this kind of porosity was indicated. Authors also benefited from expert group's expertise in evaluating possible causes associated with the creation of the aforementioned defect. A ranking of these parameters was created and their impact on the occurrence of the defect was determined. The classic statistical tools were used. The possibility of unexpected links between parameters in case of uncritical use of these typical statistical tools was indicated. It was emphasized also that the acquisition realized in production conditions must be subject to a specific procedure ordering chronology and frequency of data measurements as well improving the casting quality control. Failure to meet these conditions will significantly affect the difficulties in implementing and correcting analysis results, from which INput/OUTput data is expected to be the basis for modelling for quality control.
Today’s industry aims at such situation, where number of defective products, so called defects shall approach to zero. Therefore, one introduces a various changes in technology of production, introduces improvements which would help in accomplishment of this objective. Another important factor is introduction of different type of testing, which shall help in assessment which factor has significant effect on quantity of rejects, and which one could be neglected. Existence of casting rejects is unavoidable; therefore a new ideas, technologies and innovations are necessary in the entire widely understood foundry branch, in order to minimize such adverse effect. Performance of tests aimed at unequivocal determination of an effect of vibrations during crystallization on mechanical properties and porosity of the EN ACAlSi17 alloy was the objective of the present work. To do this, there were produced 36 castings from EN AC-AlSi17 alloy. All the castings underwent machining operations. Half of the casting was destined to strength tests, the other half served to determination of an effect of vibrations on porosity of the alloy. The specimens were divided into 12 groups, depending on amplitude of vibrations and tilt angle of metal mould during pouring operation.
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.
Vacuum conditions in foundry installations are generated using electric-driven vacuum pumps. The purpose of the experiment is to evaluate the performance of a vacuum-assisted system for compaction of moulding sand basing on registered plots of selected electric power parameters of the power-supplying system of the pumps. Model testing done on an experimental vacuum system installation, power-supplied from a system incorporating the recorders of instantaneous current and voltage values. Following the numerical procedure, the experimental data are analysed to yield mathematical relationships between the variations of the generated vacuum pressure levels and variations of selected electric power parameters. Registered and computed values of selected parameters: instantaneous and RMS voltage and current values, active, reactive and apparent power levels and power coefficient allow for diagnosing the adequacy and reliability of the system operation. According to the authors, the applied monitoring of the power parameters of a vacuum-assisted installation may become an effective and easy practical method of evaluating the performance of such installations, used also in foundry plants.
In this article the main problems related with the proper choice of the design and operation parameters of vacuum installation in vacuum moulding system have been discussed. In such system a vacuum are generated using electric-driven vacuum pumps. The aim of the experiment is to evaluate the performance of a vacuum system basing on registered plots of selected electric power parameters of the power-supplying system of the pumps with parallel measurements instantaneous values of pressure in selected points of model stand. The measurements system for power-supply unit has incorporated the recorders of instantaneous current and voltage values. Following the suitable numerical procedure, the experimental data are analysed to yield mathematical relationships between the variations of the generated vacuum pressure levels and variations of selected electric power parameters. According to the authors, the applied measurements system of the parameters of a vacuum-assisted installation may become an effective and easy practical method of evaluating the performance of such installations, used also in industry.
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.
Heating process in the domain of thin metal film subjected to a strong laser pulse are discussed. The mathematical model of the process
considered is based on the dual-phase-lag equation (DPLE) which results from the generalized form of the Fourier law. This approach is,
first of all, used in the case of micro-scale heat transfer problems (the extremely short duration, extreme temperature gradients and very
small geometrical dimensions of the domain considered). The external heating (a laser action) is substituted by the introduction of internal
heat source to the DPLE. To model the melting process in domain of pure metal (chromium) the approach basing on the artificial mushy
zone introduction is used and the main goal of investigation is the verification of influence of the artificial mushy zone ‘width’ on the
results of melting modeling. At the stage of numerical modeling the author’s version of the Control Volume Method is used. In the final
part of the paper the examples of computations and conclusions are presented.
Thermal processes in domain of thin metal film subjected to a strong laser pulse are discussed. The heating of domain considered causes
the melting and next (after the end of beam impact) the resolidification of metal superficial layer. The laser action (a time dependent belltype
function) is taken into account by the introduction of internal heat source in the energy equation describing the heat transfer in domain
of metal film. Taking into account the extremely short duration, extreme temperature gradients and very small geometrical dimensions of
the domain considered, the mathematical model of the process is based on the dual phase lag equation supplemented by the suitable
boundary-initial conditions. To model the phase transitions the artificial mushy zone is introduced. At the stage of numerical modeling the
Control Volume Method is used. The examples of computations are also presented.
According to the analysis of the current state of the knowledge shows that there is little information on the process of phase transformations
that occur during the cooling Cu-Al-Fe-Ni hypo-eutectoid bronzes with additions of Cr, Mo and/or W, made additions individually
or together, for the determination of: the type of crystallizing phases, crystallizing phases, order and place of their nucleation.
On the basis of recorded using thermal and derivative analysis of thermal effects phases crystallization or their systems, analysis of the
microstructure formed during crystallization - observed on the metallographic specimen casting ATD10-PŁ probe, analysis of the existing
phase equilibrium diagrams forming elements tested Cu-Al-Fe-Ni bronze, with additions of Cr, Mo, W and/or Si developed an original
model of crystallization and phase transformation in the solid state, the casting of high quality Cu-Al-Fe-Ni bronze comprising: crystallizing
type phase, crystallizing phase sequence, place of nucleation.