Application of Thermal Analysis to the metallurgical control of the casting process

Through these lines we will discuss the various functionalities of the thermal analysis tool Thermolan® in the different areas of the production process and how thermal analysis is applicable to all types of foundries. With the proper use of this system, it is possible to control the process to ensure the quality of the final product.

Starting from the head of the process, in the fusion area, one of the most widespread practical uses is the determination of the carbon content, whose results are obtained with great accuracy and in a short period of time, which allows continuous control of the appropriate carbon level for each reference. At the same time, the metallurgical quality of the base metal is analyzed and its evolution over time is checked. Since the system makes warnings of deviations and presents corrective actions based on expert knowledge, it allows precise adjustments to be made to the loads of the melting systems.

Regarding the applications of the system in the area of metal conditioning and treatment, in the case of spheroidal and compact cast iron, the tool assesses the nodularity index and allows evaluating the metallurgical quality of the metal before and after the nodulization treatment with magnesium, being able to carry out comparative studies of different nodularizers alloys, as well as conditioning products that allow us to determine which ones are optimal for the process.

Regarding the functionalities in the pouring area, its application to evaluate the main metallurgical characteristics stands out, but also the influence of different metallic charges, different nodulizers and various inoculants can be compared, which allows to obtain the traceability of the quality of the metal during all the process. Thermolan® also obtains in-part predictions of the matrix microstructure, the characterization of the graphite and the tendency to present contraction defects, the presence of carbides and inverse chill.

The validation process of the parameters Self feeding factor (or S.F. factor, that is, the ability of the metal to compensate for shrinkage defects) and nodularity index are based on hundreds of comparative tests between system predictions versus metallographic part analysis. The results obtained on the thermal cup predict the results on the castings.

Similar has been the validation process followed to obtain the internal soundness parameter of the parts introducing the thermal analysis and the software developed by Azterlan that takes into account the geometry of the piece.

The validation process carried out for the functionalities corresponding to the parameter “risk for the appearance of carbides” in the castings and to validate the predictions of ferrite / perlite contents in the part, have also been carried out by analyzing metallographies of the critical areas required by the customer.

As a summary, we can indicate the following conclusions. By means of thermal analysis it is possible to predict the characteristics of the material, its soundness and defects of metallurgical origin. In this way, it is possible to eliminate or optimize the random controls of batch validation and process validation, since it allows to carry out a control both of the nodularity in the case of spheroidal cast iron, and of the type of graphite in lamellar cast iron and of internal health in safety components.