Structure and wear of gradient steel castings

The effect of overheating of the melt over the equilibrium liquidus in the temperature range 1570 °C – 1670 °C and the rate of its cooling during crystallization and structure formation of castings on the formation of the length and morphology of the main macrostructural zones, grain dispersion, characteristics of the fine crystal structure, hardness and intensity of abrasive wear over the section of 25L steel castings with a differentiated cast structure was investigated. Regular changes of these indicators depending on thermokinetic conditions of crystallization are established. The determining influence of the melt cooling rate on the morphology and dispersion of the cast structure due to different degrees of melt supercooling during crystallization of different structural zones of castings is shown. As the distance from the rapidly cooling surface of the castings and taking into account the increase in the temperature of the melt overheat from 1570 ºC to 1670 ºC, the grain size varies from 5… 7 numbers to 1… 2 numbers, respectively. In the case of normal heat removal rate during crystallization, the grain size in the castings varies from 4… 2 to -1… -2 numbers. The determined characteristics of wear resistance of steel in different structural zones correlate with changes in the characteristics of the cast structure and the cross-sectional strength of castings. The research results open the prospect of developing new foundry technologies for the production of cast products with differential properties for special operating conditions. Keywords: gradient structure, structural zones, melt, wear.

Technological features of the production of welded beds from prefabricated base parts

The work is devoted to the problem of fatigue strength of welded-cast joints as applied to the operating conditions of body parts of machines. Such operating conditions are characterized by non-uniformity of intensity and concentration of the load on parts and assemblies during the operation of the equipment. This heterogeneity of the load actualizes production of precisely welded-cast base parts for metalworking equipment beds. This is of considerable technological and economic interest. The aim of the work is to study the strength of welded-cast bearing structures in relation to the work of beds of heavy lathes. Unalloyed medium-carbon structural steel 35L and steel of ordinary quality MCT3 in the form of rolled products were used as the main materials for research. The research methods are presented. The study of the structure and properties of the welded joint made it possible to assess the technical feasibility of using the studied metals in the manufacture of welded-cast bearing structures. It has been established that welding of steel castings with rolled steel causes significant structural and mechanical heterogeneity. The influence of processing technology on the nature of formation of the structure of welded-cast joints is presented. The influence of heat treatment on the value of the hardness of the welded seam and the heat-affected zone was investigated. The study of the fatigue resistance of welded-cast specimens was carried out in relation to the operating conditions of joints undergoing vibration loads at normal temperatures, which can be classified as fatigue with a symmetric load cycle. It was found that the use of heat treatment of welded-cast specimens significantly reduces the mechanical heterogeneity of the joint along the seam and the heat-affected zone. Based on the results of studying mechanical characteristics, the choice of technology for the production of welded-cast joints is justified.

Important Key Process Simulations in the Field of Steel Metallurgy

During the last decade, the chair for ‘Simulation and Modelling of Metallurgical Processes’ (SMMP) has worked on different metallurgical processes with the highlights of the following five industrial relevant topics: (i) modelling the as-cast structures of large steel castings; (ii) exploring the formation mechanisms of macrosegregation; (iii) describing magnetohydrodynamic and electrochemical phenomena in remelting processes, (iv) understanding how solidification and flow can be influenced by magnetohydrodynamics during steel continuous casting; and (v) describing nozzle clogging in steelmaking processes. In this contribution, the main achievements from the group on the above five topics are briefly described.

Peculiarities of calculations of formation of extended sections of steel castings in disposable moulds with functional coating of definite microrelief

In the present article are considered the issues of influence of the microrelief of the working cavity surface of the sand-and-clay mould on the intensity of heat exchange and formation of the structure in the surface area of the metal blank, for prevention of hot cracks formation.

A Scale-up Study on Chemical Segregation and the Effects on Tensile Properties in Two Medium Mn Steel Castings

Two ingots weighing 400 g and 5 kg with nominal compositions of Fe–8Mn–4Al–2Si–0.5C–0.07V–0.05Sn were produced to investigate the effect of processing variables on microstructure development. The larger casting has a cooling rate more representative of commercial production and provides an understanding of the potential challenges arising from casting-related segregation during efforts to scale up medium Mn steels, while the smaller casting has a high cooling rate and different segregation pattern. Sections from both ingots were homogenized at 1250 $$^{\circ} $$ ∘ C for various times to study the degree of chemical homogeneity and $$\delta $$ δ -ferrite dissolution. Within 2 hours, the Mn segregation range (max–min) decreased from 8.0 to 1.7 wt pct in the 400 g ingot and from 6.2 to 1.5 wt pct in the 5 kg ingot. Some $$\delta $$ δ -ferrite also remained untransformed after 2 hours in both ingots but with the 5 kg ingot showing nearly three times more than the 400 g ingot. Micress modeling was carried out, and good agreement was seen between predicted and measured segregation levels and distribution. After thermomechanical processing, it was found that the coarse untransformed $$\delta $$ δ -ferrite in the 5 kg ingot turned into coarse $$\delta $$ δ -ferrite stringers in the finished product, resulting in a slight decrease in yield strength. Nevertheless, rolled strips from both ingots showed $$>900$$ > 900 MPa yield strength, $$>1100$$ > 1100 MPa tensile strength, and $$>40$$ > 40 pct elongation with $$<10$$ < 10 pct difference in strength and no change in ductility when compared to a fully homogenized sample.

Machine learning mathematical model for the automatic setup of the cal and hrd flow during the process of primary aceration in electric ovens

In this work, a mathematical model is developed for the automatic predisposition of the flow of lime and HRD during the primary steeling process in HEA of the steel mill of Sidor, C.A. Model that was possible through an intelligent dynamic process control system, under a descriptive field research profile; considering a sample of 46 commercial grade steel castings (ASTM A 1018). The system consists of two simulation modules that ensure the ideal thermodynamic condition (steel temperature between 1535 to 1575 ° C, ITHD indicator less than 1,5% and a binary base index of the slag between 2 to 2,6 ) for the protection of refractory material and dephosphorization of steel. Having as a result, a reduction of the Tap To Tap of 7,08%; reduction of lime consumption by 5,28% and an increase in productivity of 7,51%. Keywords: Primary Metallurgy; Electric Arc Furnace (HEA); Mathematical Model; Machine Learning. References [1]Asociación Latinoamericana del Acero, "Alacero", [Online]. Available: https://www.alacero.org/sites/default/files/publicacion/proceso_siderurgico.pdf. [Last access: July 04, 2020]. [2]F. Morral, E. Jimeno y P. Molera, Metalúrgia general, Barcelona: Reverté, 1985. [3]B. Bucciarelli, G. Torga, F. Sabugal, F. Díaz y M. Lardizabal, "Evolución en el control del fósforo en la acería de Ternaris SIDERCA", de 18a Conferencia de acería del IAS, Rosario, Santa Fe, 2011. [4]S. Kalpakjian y S. Schmid, Manufactura, ingenieria y tecnología, 4ta ed., México: Pearson educación, 2002. [5]M. Oropeza, J. López, A. Pérez y J. Ucar, "Contribuciones para el control del fósforo cuando se utiliza mineral reducido de hierro", Revista metalurgia, vol. 35, nº 2, pp. 479-490, 2008. [6]J. Castro y F. Echeverría, Introducción a las técnicas de computación inteligente, 1era ed., Venezuela: Universidadde los andes, 2001. [7]A. Sadeghian y J. Lavers, "Application of radial basis function networks to model electric arc furnaces", IJCNN,vol. 6, pp. 3996-4001, 1999. [8]J. Brito, "Diseño de un control automatizado para la alimentación de cal mezcla en función del HRD para ajustar la basicidad binaria de la escoria del horno eléctrico #1 de la acería de planchones de Ternium SIDOR", trabajo de grado inédito, 2008. [9]A. Zambrano, V. Collazo, N. Troncone y J. Rodríguez, "A computer tool for closed-loop dynamical system identificaction through artificial neural networks", Universidad, Ciencia y Tecnología (UCT), vol. 16, nº 64, pp. 190-202, 2012. [10]E. Moreno, Tecnología de producción del ferrosilicio, 3era ed., Venezuela: Ferroatlántica de Venezuela, 2005. [11]C. García, "Optimización del proceso de formación de escoria espumosa en los hornos eléctricos de acerías de planchones de Sidor", trabajo de grado inédito, UNEFM, Punto Fijo, 2011. [12]M. Rojas, "Estudio del consumo de cal, coque, oxígeno y HRD en el proceso de formación de esocria epsumosa en el HE-5 de la acería de planchones de Sidor, C.A.", trabajo de grado inédito, UNEXPO, Puerto Ordaz, 2012. [13]R. Morales, R. Lule, F. López, J. Camacho y J. Romaero, "The slag foaming practice in EAF and its influence on the stelmaking shop productivity", ISIJ International, vol. 35, nº 9, pp. 1054-1062, 1995. [14]W. García, "Implementación de prácticas de escorias espumosa en los EAF de la acería eléctrica de planchones de Sidor, C.A.", trabajo de grado inédito, USB, Caracas, 2002. [15]S. Alameddine, B. Bowman, S. Paege y P. Stafford, "Innovation in EAF and in steelmaking processes", de AIM, Milano-Italia, 2009. [16]J. Mateos, "Análisis y optimización de costes en una planta de procesado y producción de acero", trabajo de grado inédito, UC3M, Madrid, 2010. [17]A. Conejo y J. Cárdenas , "Energy consumption in the EAF with 100% DRI", AISTECH Proceddings, vol. 1, pp. 529-535, 2006. [18]M. Rojas, O. Prado, O. Carvajal y R. Higuerey, "Impacto del consumo de cal, coque, oxígeno y HRD en la formación de escoria espumosa durante el proceso de aceración primaria en hornos de arco eléctrico", Universidad, Ciencia y Tecnología (UCT), vol. 17, nº 67, pp. 134-140, 2013.

Increase of non-stick properties of steel castings using industrial man$made waste in molding sands

The problems of improving the non-stick properties of castings, in particular, the use of molding sands with the addition of industrial man-made waste are considered. The results of industrial tests of such mixtures, their properties and analysis of the quality of technological samples are presented. Keywords: burn-in, industrial waste, molding sands, industrial tests, technological sample. [email protected]

Gradient structure and properties of steel castings

The influence of melt overheating in the range of 50-150 °C on the equilibrium liquidus and its cooling rate during crystallization of castings on the formation of macrostructural zones along their cross section, on the change of grain dispersion, dendritic structure characteristics and mechanical properties was investigated on the example of 25L steel. It is established that the macrostructure of castings in the direction of unilateral heat removal as it moves away from the cooled surface consists of four main structural zones - small coaxial crystals, columnar, branched and large coaxial crystals, the length and morphology of which naturally change depending on thermokinetic conditions of crystallization. The decisive role of the cooling rate at significant overheating of the melt to increase the number of crystallization nuclei, the formation of a more dispersed cast structure by increasing the degree of supercooling of the melt during crystallization is shown. The regularities of quantitative characteristics change of microstructure and dendritic structure depending on change of temperature-time parameters of crystallization in different structural zones of castings and their connection with characteristics of mechanical properties of steel are established. On the basis of mathematical processing of experimental data by linear regression analysis interpolation models and their graphical interpretations are obtained, which allow to quantify and predict the change of mechanical properties in different structural zones of gradient castings depending on melt overheating temperature and cooling modes within the investigated factor space. Keywords: gradient structure, structural zones, melt, mechanical properties.