Characteristics of the microstructure of corrosion-resistant cast 24Cr-5Ni-2.5Mo duplex steel after introduction of 0.98, 1.67 and 4.3% Si were described. Based on the test results it has been found that silicon addition introduced to the corrosion-resistant cast two-phase duplex steel significantly reduces austenite content in the alloy matrix. Increasing silicon content in the test alloy to 4.3% has resulted, in addition to the elimination of austenite, also in the precipitation of Si-containing intermetallic phases at the grain boundaries and inside the grains. The precipitates were characterized by varying content of Cr and Mo, indicating the presence in the structure of more than one type of the brittle phase characteristic for this group of materials. The simulation using Thermo-Calc software has confirmed the presence of ferrite in all tested alloys. In the material containing 4.3% Si, the Cr and Si enriched precipitates, such as G phase and Cr3Si were additionally observed to occur.

The article presents the results of the investigations performed on high manganese austenitic steel which underwent the test of uniaxial tension, with the application of electric current impulses. The application of low voltage impulse alternating current of high intensity during the plastic deformation of the examined steel caused the occurrence of the electroplastic effect, which changed the shape of the stress-strain curve. A drop of flow stress and elongation of the tested material was observed in the case of the application of electric current impulses, in respect of the material stretched without such impulses and stretched at an elevated temperature. The analysis of the morphology of the fractures showed differences between the samples tested under the particular conditions. An analysis of the alloy’s microstructure was also performed under different conditions. The application of electric current impulses can have a significant influence on the reduction of the forces in the plastic forming processes for this type of steel.

The contributions of work-hardening of austenite and the presence of martensite on the hardening of an AISI 304L stainless steel were evaluated based on plastic deformation under different reductions in thickness at two rolling temperatures. The cold deformation temperatures of 300 K and 373 K were chosen to induce strain-hardening plus strain-induced martensitic transformation in the former and strain-hardening in the latter. This made it possible to elucidate the real effects of strengthening mechanisms of metastable austenitic stainless steels during mechanical working.

The article deals with the influence of chemical composition of martensitic stainless steel for castings GXCrNi13-4 (the 1.4317 material) on mechanical properties and structure of as cast steel after heat treatment. Properties of these martensitic stainless steel are heavily influenced by chemical composition and structure of the material after heat treatment. Structure of these steels after quenching is formed with martensite and residual austenite. When tempering the steel the carbon content in martensite is reduced and gently deposited carbides occur. The way of heat treatment has a major impact on structure of martensitic steels with low carbon content and thus on strength, hardness and elongation to fracture of these steels. Chemical composition of the melt has been treated to the desired composition of the lower, middle and upper bounds of the nickel content in the steel within the limits allowed by the standard. Test blocks were gradually cast from the melt. The influence of the nickel equivalent value on structure and properties of the 1.4317 steel was determined from results of mechanical tests.

The modification of the chemical composition of non-metallic inclusions by rare-earth elements in the new-developed microalloyed steels was discussed in the paper. The investigated steels are assigned to production of forged elements by thermomechanical treatment. The steels were melted in a vaccum induction furnace and modification of non-metallic inclusions was carried out by the michmetal in the amount of 2.0 g per 1 kg of steel. It was found that using material charge of high purity and a realization of metallurgical process in vacuous conditions result in a low concentration of sulfur (0.004%), phosphorus (from 0.006 to 0.008%) and oxygen (6 ppm). The high metallurgical purity is confirmed by a small fraction of non-metallic inclusions averaging 0.075%. A large majority of non-metallic inclusions are fine, globular oxide-sulfide or sulfide particles with a mean size 17 µm2 . The chemical composition and morphology of non-metallic inclusions was modified by Ce, La and Nd, what results a small deformability of nonmetallic inclusions during hot-working.

Determination of the ferrite content in austenitic steels, which solidified under defined conditions. Ferrite content in austenitic matrix was determined from samples with wall thickness of 60 mm. Measured ferrite contents served to propose the regression equations for the calculation of the ferrite content in steels with Cr content of 18 up to 22 % and Ni of 9 up to 11 %. An additional regression equation was proposed for steels with a higher Ni content. The proposed regression equations have been checked up on the operating melts. In conclusion, the ferrite content in the axis of the casting of wall thickness of 500 mm has been calculated and it was compared to the ferrite determined in the usual way from the cast-on test.

The research was concerned with the influence of chemical composition of austenitic steels on their mechanical properties. Resulting properties of castings from austenitic steels are significantly influenced by the solidification time that affects the size of the primary grain as well as the layout of elements within the dendrite and its parts with regard to the last solidification points in the interdendritic melt. During solidification an intensive segregation of all admixtures occurs in the melt, which causes a whole range of serious metallurgical defects and it has also a significant influence on subsequent precipitation of carbides and intermetallic phases. Chemical heterogeneity then affects the structure and mechanical properties of the casting. In a planned experiment, we cast melted steels containing 18 to 28 % Cr and 8 to 28 % Ni with variable carbon and nitrogen contents. Testing the tensile strength of the cast specimens we could determine the Rp0.2, Rm, and A5 values. The dependence of the mechanical properties on the chemical content was described by regression equations. The planned experiment results allow us to control the chemical content for the given austenitic steel quality to achieve the required values of the mechanical properties.

The article is focused on thermomechanical and plastic properties of two high-manganese TRIPLEX type steels with an internal marking 1043 and 1045. Tensile tests at ambient temperature and at a temperature interval 600°C to 1100°C were performed for these heats with a different chemical composition. After the samples having been ruptured, ductility was observed which was expressed by reduction of material after the tensile test. Then the stacking fault energy was calculated and dilatation of both high-manganese steels was measured. At ambient temperature (20°C), 1043 heat featured higher tensile strength by 66MPa than 1045 heat. Microhardness was higher by 8HV0,2 for 1045 steel than for 1043 steel (203HV0,2). At 20°C, ductility only differed by 3% for the both heats. Decrease of tensile properties occurred at higher temperatures of 600 up to 1100°C. This tensile properties decrease at high temperatures is evident for most of metals. The strength level difference of the both heats in the temperature range 20°C up to 1100°C corresponded to 83 MPa, while between 600°C and 1100°C the difference was only 18 MPa. In the temperature range 600°C to 800°C, a decrease in ductility values down to 14 % (1045 heat), or 22 % (1043 heat), was noticed. This decrease was accompanied with occurrence of complex Aluminium oxides in a superposition with detected AlN particles. Further ductility decrease was only noted for 1043 heat where higher occurrence of shrinkag porosity was observed which might have contributed to a slight decrease in reduction of area values in the temperature range 900°C to 1100°C, in contrast to 1045 heat matrix.

Cast stainless steel of the Cr-Ni duplex type is used, among others, for the cast parts of pumps and valves handling various chemically

aggressive media. Therefore, the main problem discussed in this article is the problem of abrasion wear resistance in a mixture of SiC and

water and resistance to electrochemical corrosion in a 3% NaCl- H2O solution of selected cast steel grades, i.e. typical duplex cast steel,

high silicon and manganese duplex cast steel, and Cr-Ni austenitic cast steel (type AISI 316L). The study shows that the best abrasion

wear resistance comparable to Ni-Hart cast iron was obtained in the cast duplex steel, where Ni was partially replaced with Mn and N.

This cast steel was also characterized by the highest hardness and matrix microhardness among all the tested cast steel grades. The best

resistance to electrochemical corrosion in 3% NaCl- H2O solution showed the cast duplex steel with high content of Cr, Mo and N. The

addition of Ni plays rather insignificant role in the improvement of corrosion resistance of the materials tested.

The results of the modification of austenitic matrix in cast high-manganese steel containing 11÷19% Mn with additions of Cr, Ni and Ti

were discussed. The introduction of carbide-forming alloying elements to this cast steel leads to the formation in matrix of stable complex

carbide phases, which effectively increase the abrasive wear resistance in a mixture of SiC and water. The starting material used in tests

was a cast Hadfield steel containing 11% Mn and 1.34% C. The results presented in the article show significant improvement in abrasive

wear resistance and hardness owing to the structure modification with additions of Cr and Ti.

The paper presents the results of the effect of isothermal heating time on the disappearance of strain hardening (the softening degree) of the studied high-manganese TRIPLEX type steels at a temperature of 900 and 1000°C. In order to determine the kinetics of recrystallization of austenite plastically deformed for selected steels, hot compression tests with draft ε = 0.2 were made. The presented results reveal that the complete recrystallization of austenite needs long isothermal heating times. In industrial conditions, such long times are not used, therefore in the initial rolling passages, the time required for half recrystallization of austenite t0.5 is often used. The total disappearance of the strain hardening, completion of the recrystallization of austenite tested high-manganese X98 and X105 TRIPLEX type steels isothermal heating time requires far more than 200 s. The increase of the deformation temperature is a factor influencing the acceleration of the disappearance of strain hardening.

Steel and cast-iron products, due to their low price and beneficial properties, are the most widely used among metals; their consumption has become an indicator of the economic development of countries. The characteristics of iron raw materials, in relation to current metallurgical requirements, are presented in the present this article. The globalization of the trade and development of steelmaking technologies have caused significant changes in the quality of raw materials in the last half-century forcing improvements in processing technologies. In many countries, standard concentrates (at least 60% Fe) are almost twice as rich as those processed in the mid-20th century. Methods of quality assessment have been improved and quality standards tightened.

The quality requirements for the most important raw materials ‒ iron ores and concentrates, steel scrap, major alloy metals, coking coal, and coke, as well as gas and other energy media ‒ are reviewed in the present paper. Particular attention is paid to the quality testing methodology. The quality of many raw materials is evaluated multi-parametrically: both chemical and physical characteristics are important. Lower-quality parameters in raw materials equate to significantly lower prices obtained by suppliers in the market.

The markets for these raw materials are diversified and governed by separate sets of newly introduced rules. Price benchmarks (e.g. for standard Australian metallurgical coal) or indices (for iron concentrates) apply. Some raw materials are quoted within the framework of the commodity market system (certain alloying components and steel scrap). The abandonment of the long-established system of multi-annual contracts has led to wide fluctuations in prices, which have reached a scale similar to that of other metals.

Steel loss related to the formation of scale is a parameter that is of great importance in the charge heating process. The value of steel loss determined by the thickness of the scale layer affects the intensity of the heat transfer process in the heating furnace, but also constitutes a significant element in the heat-material balance. Reducing the loss of steel during charge heating has a positive effect on heat consumption and material losses, which is extremely important in the context of energy and resource savings, the main elements of sustainable development processes. The methodology of determining the loss of steel to scale in an industrial heating furnace is presented in the paper. The results of calculations for various charge temperatures at the entrance to the furnace are presented. The influence of furnace operating conditions on steel loss is discussed.

The aim of this study is to compare the corrosion resistance of X37CrMoV5-l tool steel after nanostructurization and after a conventional heat treatment. The nanostructuring treatment consisted of austempering at 300°C, which produced a microstructure composed of nanometric carbide-free bainite separated by nanometric layers of retained austenite. The retained austenite occurred also in form of blocks which partially undergo martensitic transformation during final cooling. For comparison, a series of steel samples were subjected to a standard quenching and high tempering treatment, which produced a microstructure of tempered martensite. The obtained results showed that the corrosion resistance of steel after both variants of heat treatment is similar. The results indicate that the nanocrystalline structure with high density of intercrystalline boundaries do not deteriorate the corrosion resistance of steel, which depends to a greater extent on its phase composition.

In present work, two nuclear grade steel (P91, P92) are joined using the arc welding process. The welded joints were subjected to the heat treatment in order to restore the mechanical properties and overcome the heterogeneity across the joints. The weldments were studied for microstructure evolution and mechanical behavior under different condition of heat treatment. The variation in mechanical behavior obtained for the welded joints were tried to relate the microstructural evolution. After the normalizing based heat treatment, homogeneity with negligible δ ferrite across the welded joints was observed.

Both the steel loss to scale and the scale adhesion are very important parameters of the heating process. High values of steel loss (large thickness of the scale layer) reduce the heat exchange intensity in the furnace chamber, which results in higher energy consumption. A low adhesion value adversely affects the operation of heating furnaces, while too high value causes the scale to roll into a steel product and deteriorate its purity and quality.
The paper presents the research methodology and the results of measurements of steel loss and scale adhesion. The effect of the excess air combustion ratio values on loss of steel and scale adhesion for constant furnace efficiency is discussed. This influence was described by mathematical dependencies. The tests were carried out for traditional technology and rational technology, enabling the reduction of steel losses to scale and energy consumption.

In Eurocode 5, the stiffness equation for bolted steel-wood-steel is stated as a function ofwood density and fastener diameter only. In this research, an experimental study on various configurations of tested bolted steel-wood-steel (SWS) connections has been undertaken to predict the initial stiffness of each connection. In order to validate the Eurocode 5 stiffness equation, tests on 50 timber specimens (40 glued laminated timbers and 10 laminated veneer lumbers (LVL)) with steel plates were undertaken. The number of bolts was kept similar and the connector diameter, timber thickness, and wood density were varied. The results obtained in the experimental tests are compared with those obtained from the Eurocode 5 stiffness equation. From the analysis, it is signified that the stiffness equation specified in Eurocode 5 for bolted SWS connections does not adequately predict the initial stiffness. The results from Eurocode 5 stiffness equation are very far from the experimental values. The ratio of stiffness equation to experimental results ranges from 3.48 to 4.20, with the average at 3.77, where the equation overpredicted the experimental stiffness value for the connection. There is a need to consider or incorporated other parameters such as geometric configurations in Eurocode 5 stiffness equation to improve the ratio with the experimental data.

The column is one of the most significant structural elements, which is designed to support mainly the compressive load. Strengthening of existing reinforced concrete columns is required to enhance ductility and increase load capacity to sustain the overload as sometimes there may be a change in use. Ten rectangular concrete columns were constructed and tested. H/b ratio was kept constant and equals 6 for all columns The aim of this work is to study the behaviour and efficiency of RC columns strengthened with steel jackets subjected to axial load. An experimental study of the behaviour of ten strengthened concrete columns with slenderness ratio (t / b) equals 6 was carried out. Variables such as aspect ratio ( H / b), the volume of steel batten plates, and spacing of steel batten plates at centres ( S) were considered. The results showed that using this method of strengthening is very effective and an increase in the axial load capacity of the strengthened columns is obtained.

The results are based on two experimental high-manganese X98MnAlSiNbTi24-11 and X105MnAlSi24-11 steels subjected to thermo-mechanical treatment by hot-rolling on a semi-industrial processing line. The paper presents the results of diffraction and structural studies using scanning and transmission electron microscopy showing the role of Nb and Ti micro-additives in shaping high strength properties of high-manganese austenitic-ferritic steels with complex carbides. The performed investigations of two experimental steels allow to explain how the change cooling conditions after thermo-mechanical treatment of the analysed steels affects the change of their microstructure and mechanical properties. The obtained results allow assessing the impact of both the chemical composition and the applied thermo-mechanical treatment technology on the structural effects of strengthening of the newly developed steels.