Introduction

 

The problem to find out if the molten metal will in the solidified form have the desired properties is so old as the metallurgy itself. Today are 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 itself.  Besides the temperature measurement and the determination of the average chemical composition there is no any other direct melt quality control.

The 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.

The 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.

Ignoring 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".

Taking 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.

 

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