System for determining and documenting grain refining and modification

Aluminium alloys are subject to constant fluctuations as result of their composition. This is due both to the specified limit ranges of their permissible chemical composition, as well as natural change, for example through loss of Mg in the working process.

Treatments of a melt with various preparations (the effects of which vary in duration) also change the solidification process and therefore influence the quality of the castings. Given that recycling and recycled materials are common everyday practice, it is apparent that zero states, ideal or zero curves, etc. are not possible; instead only ever the current state of a melt. Considering this condition to be a "0" state or fully unmodified because a treatment has not yet been carried out is therefore incorrect and leads to acting "blindly".

Direct assessment of the current state of modification is only possible with differentiated assignment of the depression in the eutectic range. This requires that a distinction be made between the shift of the eutectic point by alloying elements such as Mg, Cu, Fe or the shift by modifying elements such as Na and Sr. This means: Depression does not equal modification.

These effects on the solidification process are always dependent on the effect of the quantity present: For example, 0.1% Mg can give a ΔT of 0.8 - 1.2 K; as such with an AlSi10Mg whose Mg content is limited from 0.25 to 0.45% for example, a mean value of 0.3% Mg would give a ΔT of 2.4 - 3.6 K. Given that Sr reaches a ΔT of 4.0 K to max. 10.0 K depending on the alloy, it is clearly apparent that determining the effect is more important than knowing the quantity. The success of modification is essentially dependent on the effect of the refining agent used, such as Na, Sr and/or P, Ca. The fact that a modifying element is present in quantity does not guarantee that modification has been achieved. In the case of the inoculant TiBor, analysis of the grain refinement is comparable. The incubation time, treatment and standing time determine the effectiveness of grain refinement and differ significantly from the purely quantitative spectrometry approach.

Precise acquisition and differentiated analysis of the solidification, i.e. determination of the influences of all "participants", is the fundamental prerequisite for the sound evaluation of modification / grain refinement. These findings are part of the IDECO thermo-analysis, which enables a fully automatic analysis for quality control and therefore promotes waste reduction, energy efficiency and process optimisation.

The results of the complete documentation, summarised in a report containing detailed information about the suppliers of the materials, the melting process, the melt treatments, the results of the accompanying tests, the temperature curve as well as the target and identification of the cast part, can be seen in the typical printout of an IDECO thermo-analysis. IDECO Thermo-Analysis devices are of course equipped with a network-compatible database, in which all information, including external measurement data (e.g. spectral analysis, temperatures, density index, degassing parameters of the Melt Clean) is automatically stored and managed. The usefulness of a database like this is almost limitless when it comes to analysing dependencies, process controls and statistics of any kind, thanks to the tailored configuration.

Internal analysis process
interne Analyse

Typical printout
typischer Ausdruck