The operation of blast furnaces using natural gas and oxygen enriched blast (composite blast technology) is being used in many iron and steel companies to reduce the consumption of coke per unit weight of hot metal. The addition of oxygen to the air blast and injection of natural gas through tuyeres have a different effect on the basic variables of the blast furnace processes such as the temperature in the hearth, the degree of direct reduction and the dynamic conditions of the gas in the furnace. The most important reason for saving coke in composite blast technology is the decrease in the share of direct reduction of iron oxide. The main controlling parameter in the operation of the blast furnace using natural gas injection is the theoretical flame temperature. The amount of natural gas in the blast can be optimised to attain the minimum value of the theoretical flame temperature.The present paper presents the theoretical bases of the composite blast technology using natural gas injection and develops an accurate method to calculate the theoretical flame temperature. List of symbolsC h coke coke carbon consumption as a source of heat C r coke coke carbon consumption in reduction processes C d-el the coke carbon consumption for direct reduction of impurities of hot metal (Mn, S, Si and P) C e , Fe e carbon and iron contents in hot metal C H 2 O ,C CH 4 heat capacities of blast moisture and methane respectively C i the real coke carbon consumption C h i the ideal value of coke carbon consumption at r d 50 C min. the minimum possible coke carbon consumption by PDK model C NG the carbon content of natural gas C R coke replacement ratio with NG C 0 t b enthalpy of dry blast C W the quantity of coke carbon burning at tuyeres D CH 4 content in dry blast i9 b enthalpy of hot blast i C enthalpy of coke carbon burning to slag temperature i W enthalpy of raceway gases K i the real coke consumption K min the minimum possible coke consumption by PDK model M C , M Fe the molecular mass of carbon and iron respectively n mole of CH 4 Q C-Fe heat of dissolving carbon in Fe Q C w heat given by coke carbon burning at the tuyeres in the thermal reserve zone of the furnace (at T51173 K) Q CH 4 heat given by 1 mol of methane in the thermal reserve zone of the furnace at T51173 K r d the degree of direct reduction of wustite r d~F e z2 d Fee t b temperature of the blast t s temperature of methane u the amount of produced slag V b the volume of the blast V max NG the maximum NG injection through tuyeres V TG the yield of top gas W C the heat of combustion of coke carbon to CO -g H 2 the degree of utilisation of H 2 in the reaction: FeOzH 2 5FezH 2 O, the equilibrium constant of the reaction is K P2 Ironmaking and Steelmaking 2009 VOL 36 NO 1ḡ CO the degree of utilisation of CO in the reaction: FeOzCO5FezCO 2 , the equilibrium constant of the reaction is K P1 DH T 1 enthalpy of direct reduction of iron oxide Di e and Di u enthalpy changes of hot metal and slag respectively burning from T5 1173 K to temperature of hot metal and slag res...

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The purpose of this study was to find and optimize the process parameters of producing tool steel 1.2709 at a layer thickness of 100 μm by DMLS (Direct Metal Laser Sintering). HPDC (High Pressure Die Casting) tools are printed from this material. To date, only layer thicknesses of 20–50 μm are used, and parameters for 100 µm were an undescribed area, according to the state of the art. Increasing the layer thickness could lead to time reduction and higher economic efficiency. The study methodology was divided into several steps. The first step was the research of the single-track 3D printing parameters for the subsequent development of a more accurate description of process parameters. Then, in the second step, volume samples were produced in two campaigns, whose porosity was evaluated by metallographic and CT (computed tomography) analysis. The main requirement for the process parameters was a relative density of the printed material of at least 99.9%, which was achieved and confirmed using the parameters for the production of the samples for the tensile test. Therefore, the results of this article could serve as a methodological procedure for optimizing the parameters to streamline the 3D printing process, and the developed parameters may be used for the productive and quality 3D printing of 1.2709 tool steel.

This paper aims at an in-depth and comprehensive analysis of mechanical and microstructural properties of AISI 316L austenitic stainless steel (W. Nr. 1.4404, CL20ES) produced by laser powder bed fusion (LPBF) additive manufacturing (AM) technology. The experiment in its first part includes an extensive study of the anisotropy of mechanical and microstructural properties in relation to the built orientation and the direction of loading, which showed significant differences in tensile properties among samples. The second part of the experiment is devoted to the influence of the process parameter focus level (FL) on mechanical properties, where a 48% increase in notched toughness was recorded when the level of laser focus was identical to the level of melting. The FL parameter is not normally considered a process parameter; however, it can be intentionally changed in the service settings of the machine or by incorrect machine repair and maintenance. Evaluation of mechanical and microstructural properties was performed using the tensile test, Charpy impact test, Brinell hardness measurement, microhardness matrix measurement, porosity analysis, scanning electron microscopy (SEM), and optical microscopy. Across the whole spectrum of samples, performed analysis confirmed the high quality of LPBF additive manufactured material, which can be compared with conventionally produced material. A very low level of porosity in the range of 0.036 to 0.103% was found. Microstructural investigation of solution annealed (1070 °C) tensile test samples showed an outstanding tendency to recrystallization, grain polygonization, annealing twins formation, and even distribution of carbides in solid solution.

The main aim of this article is to compare two approaches to decreasing the overall weight of components by using additive manufacturing from AlSi10Mg alloy. This optimization is advantageous as it lessens both the production time of parts (components) and overall costs, in key industries such as aviation. The first method used to reduce the weight of a structure is the implementation of lattice structures, which replace filled parts with selected structures of different shapes, while maintaining key properties of the original structure. The other method to decrease weight is the topological optimization of prepared samples. In this article, these two options have been compared. The specially designed sample was first optimized topologically. Subsequently, it was lightened using selected structures (Octet truss and Rhombic dodecahedron) in SW Magics with different lattice parameters. These samples were then printed using DMLS technology from AlSi10Mg on the ConceptLaser M2 Cusing system. The material used was analysed by SEM, and a particle size distribution was also performed. Furthermore, a three-point bending test was performed on the bodies produced in this way. The results of this test were analysed and evaluated in terms of load (bending force), depending on the type of sample and the volume/weight saved.