“Application of Thermal Analysis to the metallurgical control of the casting process.”

In this second publication the various functionalities of Thermolan® thermal analysis tool in the different areas of the production process are addressed, as well and how they are applicable to all types of foundries. With the proper use of Thermolan®, it is possible to control the process to ensure the quality of the final product.

Starting from the head of the process, in the melting area, one of the most widespread practical uses is the determination of the carbon content, which are obtained with great accuracy and in a short period of time. That way a continuous control of the appropriate carbon level for each reference can be achieved. 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 charges of the melting systems.

Regarding the applications of the system in the area for ​​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 magnesium nodulization treatment, being able to carry out comparative studies of different nodulizing 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, the application of Thermolan® to evaluate the main metallurgical characteristics stands out, but it also allows comparing the influence of different metallic charges, different nodulizers and various inoculants. That way, the quality of the metal can be traced during the whole process. Thermolan® also obtains in part predictions of the matrix microstructure, of the characterization of the graphite and the tendency to present contraction defects, of the presence of carbides and of inverse chill.

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

The validation process followed to obtain the internal soundness parameter of the parts by introducing the thermal analysis has been similar.

The validation process for the functionalities corresponding carbides appearance risk parameter and for predicting ferrite / perlite contents in the part, have also been developed based on metallographic analysis performed of the critical areas.

As a summary, we can indicate the following conclusions. By means of thermal analysis it is possible to predict the characteristics of the material and its internal soundness as well as to detect defects of metallurgical origin. This way, it is possible to eliminate or optimize the random controls of batch validation and process validation, because it allows to control the nodularity (when it comes to spheroidal cast iron) or the type of graphite (in lamellar cast iron) and the internal soundness in safety parts.