problem to find out if the molten metal will in the solidified form have the
desired properties is so old as the metallurgy itself.
properties of the material as cast depend only on the crystalline structure and
the amounts of the constitutional phases as the result of the solidification
process, which is generally unknown.
Even with today's best technology this remained an art, mostly dependent
on the past experience of the personnel in each individual facility - the metal
with the same origin of raw material, with the same chemical composition, melted
and cast under the same conditions shows in the rule different properties of
solid final product from the facility to facility - and very often in the same
facility from day to day, from one melting team personnel to another. The reason
is well known. It is the complexity of physical and chemical processes during
the solidification, which are very sensitive on the fluctuations of the melt
system inner and outer parameters, summary called cleanliness and cast ability
of the melt. The processes are interdependent, connected and concurrent. They
determine the micro crystalline structure, macro crystalline structure, amounts
of the constitutional phases, chemical composition variations in the grains,
impurities, their amounts and locations etc. in the solidified alloy. These
parameters are in the end effect responsible for the final properties, including
further workability of the material obtained.
quality of material is defined as the "precision" with which the
properties aimed are achieved with the reasonable means; it is the ability to
achieve the goal properties. This is only possible by understanding the most
important interplaying factors - if they can be measured and quantitatively
influenced to control at least the most sensitive part of the metallurgical
process - the melt treatment, called secondary metallurgy, after the melting of
the charge material.
the eventual breaking down of the tools and facilities, practically the whole
metallurgical waste is caused by the improper cleanliness and cast ability. The
officially given figures for the amounts of the waste are the least of that what
cannot be "hidden".
in consideration, that all metallurgical facilities are producing a wide
spectrum of materials with different properties - even if the specialization on
the couple of alloys would be a benefit in most cases - they are not able to do
that. The actual waste is turned in account as the normal production by
attaching the closest standard alloy label to the product obtained, without
mentioning what actually the product should be. So the reduction of the real
waste amount is just a bookkeeping measure to reduce inevitable statistical
spread of production.
These problems are also well known and a great effort was made especially in the past years, after the recurring from the recession, to assure the optimal metallurgical processing for the given goal properties of alloys. Very sophisticated computer systems with the most modern software are used to analyze, to control and to regulate the whole production process. The results achieved are significant, but the waste, however diminished, remained. The reason for this situation is, that all steps to control and to regulate the melting process targeted on the production apparatus and facilities, but not on the properties of the molten metal. The only parameters concerning the molten metal in particular and taken into the consideration for the quality control are the temperature and the average chemical composition of the melt.