The Importance of TDA Thermal Analysis in an Automated Metallurgical Process

The article presents the results of research and work related to the implementation of the research and development project POIR.01.01.01-00-0120/17 co-financed by the EU, through the NCBR, entitled: Innovative technology using thermal analysis, TDA, of self-feeding manufacturing of high-quality cast iron to produce new generation, enhanced performance casts. In many foundries, thermal derivative analysis (TDA) is used in addition to chemical analysis to evaluate the physical and chemical properties of an alloy while it is still in the melting furnace or ladle and before it is poured into the mold. This fact makes it possible to improve the metallurgical quality of the alloy by introducing alloying additives, carburizers or modifiers into the furnace as part of the pre-modification or primary or secondary modification in the ladle or when pouring into molds. Foundry machinery (modifier dosing systems and spheroidizing station) is very important in these operations. Only the full synergy of modern equipment with modern technology ensures high quality and repeatability of the casting process. The article mainly discusses the obtained parameters of TDA analysis (with the use of the ITACA system) at different stages of melting and how to improve them by using modern and fully automated dosing systems (Itaca OptiDose, ItacaWire and ItacaStream). Special attention was paid to the minimum temperature of the eutectoid. The change of its value after the modification process, its influence on the quality of the melted metal, a very strong correlation with the number of nuclei and the number of graphite precipitations in the casts were shown

Optimizing the Gating System for Steel Castings

The article presents the attempt to optimize a gating system to produce cast steel castings. It is based on John Campbell’s theory and presents the original results of computer modelling of typical and optimized gating systems for cast steel castings. The current state-of-the-art in cast steel casting foundry was compared with several proposals of optimization. The aim was to find a compromise between the best, theoretically proven gating system version, and a version that would be affordable in industrial conditions. The results show that it is possible to achieve a uniform and slow pouring process even for heavy castings to preserve their internal quality

Selected Phenomena of the In-Mold Nodularization Process of Cast Iron That Influence the Quality of Cast Machine Parts

This paper discusses a problem connected with the production process of ductile iron castings made using the in-mold method. The study results are presented showing that this method compromises the quality of the cast machine parts and of the equipment itself. Specifics of the nodularization process using the in-mold method do not provide the proper conditions for removal of chemical reaction products to the slag, i.e., the products stay in the mold cavity and they also decrease the quality of the casting. In this work, corrosion-type defects were diagnosed mostly on the surface of the casting and some compounds in the near-surface layer—i.e., fayalite (Fe2SiO4) and forsterite (Mg2SiO4)—which cause discontinuities in the metal matrix. The results presented here were selected based on experimental melts of ductile iron. The elements of the mold used in this study, the shape of the mixing chamber, charge materials, method of melting, temperature of liquid metal, etc. were directly related to the production conditions. An analysis was conducted of the chemical composition using a Leco GDS500A spectrometer and a carbon and sulfur Leco CS125 analyzer. Metallographic examinations were conducted using a Phenom-ProX scanning electron microscope with an EDS system

Method for Resistivity Measurement of Grainy Carbon and Graphite Materials

The article presents the issue of electrical resistivity measurement of carbon materials. The device that was developed by the authors is described and is the subject of a Polish patent. The innovative approach of the setup is based on the possibility of measuring the resistivity of grainy (powdered, dusty) materials without having to conduct their preliminary pressing. The material that is to be analyzed is placed inside the chamber made of electrically non-conducting material. The sample is then compacted with pneumatically driven pistons and the compaction force can be controlled by the air pressure. The device as proposed by the authors works at a pressure of 900 kPa, which is equal to the compaction force of 1.2 kN. Resistivity is calculated on the basis of the voltage drop recorded on the sample length. The research covers the analysis of the influence of carbon material grade and compaction force on the resistivity value. It was stated that the resistivity of the graphite materials that were analyzed here changed within the range of 43⁻172 µm: petroleum coke—360⁻780 µm; the anthracite—1900⁻3900 µm. The experimental method presented here can be used whenever carbon materials are present in the form of grains

The Importance of SiC in the Process of Melting Ductile Iron with a Variable Content of Charge Materials

The article presents issues related to melting ductile iron grade EN-GJS-400-15, with different proportions of feedstock (steel scrap and pig iron). The main attention was paid to determining the impact of silicon carbide on the structure and properties of melted cast iron. In the conducted melts, carbon and silicon deficiencies were supplemented with a suitably chosen carburizer, ferrosilicon, and SiC metallurgical silicon carbide. The percentage of silicon carbide in the charge ranged from 0 to 0.91%. The basic condition for the planning of melts was to maintain the repeatability of the chemical composition of the output cast iron and cast iron after the secondary treatment of liquid metal with various charge compositions. Based on the tests, calculations, and analyses of the results obtained, it was concluded that the addition of SiC may increase the number and size of graphite precipitates. Increasing the SiC content in the charge also caused a change in the solidification nature of the alloy and the mechanism of growth of spheroidal graphite precipitates, causing their surface to form a scaly shell. The influence of the addition of silicon carbide on the reduction of the temperature of liquidus in the alloys was also observed. Silicon carbide had a positive effect on the structure and properties of melted alloys. The introduction of SiC into the melting in the studied range caused an increase in the content of carbon and silicon without causing an increase in the amount of impurities in the alloy

Numerical modelling and experimental validation of the pneumatic powder injection into liquid alloys

322-328The pneumatic powder injection is well-known and widely used with injection lances submerged into metal bath. However, sometimes better is to not introduce the lance below the liquid metal surface because of the metal splashing and introducing of gases into metal volume. In such a case non-submerged lance is used but the problem with particles jet penetration into the metal volume appears. This paper presents the results of the studies on the pneumatic powder injection with non-submerged lance. The high-speed camera recording of the model diphase jet leaving the lance is carried out. Then image analysis is performed to estimate real particles motion parameters. Furthermore, the jet cone is analysed to check its character of development and compared with the reported results in the literature. The results are obtained that the particles real velocity is smaller than calculated from typically used formulas. The same with cone angles – it seems to be different than quoted in the literature. Next stage is numerical modelling using AnSys software. The results were compared with the experiments and the model is adjusted. The next stage is ferroalloy “cold” injection and again the computer modelling. The last stage is FeSi injection into grey iron experiments. The analysis of the results is combined both with the laboratory results and modelling then compared with previous data. As a consequence the validated numerical model is obtained which can be helpful for the injection process planning in industrial conditions

Various Aspects of Application of Silicon Carbide in the Process of Cast Iron Melting

The article discusses benefits associated with the use of silicon carbide in the process of melting gray cast iron and ductile cast iron in induction electric furnaces. It presents the analysis of the impact of various charge materials and the addition of a variable amount of SiC and FeSi to the fixed charge when melting cast iron of grades GJS 400-15 and GJS 500-7 on mechanical properties and microstructure. Moreover, the article includes an analysis of the efficiency of carburization and the increase in the content of silicon during the application of SiC. The article also presents the results of the study of primary modification using silicon carbide at the minimum temperature of Temin eutectic and Tsol solidus. Based on analysis of the literature, conducted research, and calculations, it was found that the addition of silicon carbide has a beneficial impact on the properties of melted cast iron. The addition of SiC in the charge increases the content of C and Si without increasing the amount of contaminations. The addition of SiC at reduced pig iron presence in the charge decreases production costs, while the use of SiC as an inoculant increases both Temin and Tsol, which is beneficial from the point of view of cast iron nucleation