Fulltext search in archive

This paper explores the investigation of a natural alloy processed using the rapid solidification tech-nique. The study involves the reduction of manganese nodules through aluminothermy with a 20 wt. % excess of aluminum, followed by further processing of the resulting alloy using the melt-spinning process. The obtained melt-spun ribbons were subjected to a comprehensive analysis, including X-ray diffraction, scanning electron microscopy for microstructure observation, and EDS analysis for local chemical composition. The research unveiled that the rapidly solidified ribbons consist of several key phases, including β-Mn, the Heusler phase Mn2FeSi, and an intermetallic phase (Cu,Mn)3(Al,Si). Im-portantly, the phase composition exhibited notable differences from that of the as-reduced alloy, with a reduced number of phases in the rapidly solidified ribbons. Notably, the phase composition re-mained stable even after annealing, demonstrating the robustness of the rapidly solidified material. Impressively, the material exhibited a remarkable hardness of approximately 800 HV 0.1, even after 100 hours of annealing at temperatures of 500 and 750°C.

The paper focuses on proposing a method for implementing key performance indicators (KPIs) to assess the effectiveness of manufacturing processes. For the evaluated processes of precision parts machining, the share of non-conforming products was proposed as a KPI, evaluated as both an exter-nal and an internal indicator. The external indicator EXTppm expressed the quantity of faulty prod-ucts to the volume of production. Its monthly development during 2022 was evaluated. The internal KPI represented the internal share of non-conforming products INTppm during 2022 which was re-lated to the order of part A. Towards the conclusion causes for not attaining the targeted KPI values are pinpointed, and recommendations are put forth to enhance the productivity of manufacturing processes.

Currently, there is a demand in the aerospace industry for a more effective and non-invasive milling technique for powder metallurgy γ-TiAl alloy. The primary objective of this research is to examine the surface milling process of a γ-TiAl alloy generated by powder metallurgy. The primary objective of this study is to examine the impact of process parameters on the surface roughness and cutting force of the alloy, with the aim of optimizing both surface roughness and cutting force. The response surface method was implemented to examine the milling process, and the NSGA II algorithm was employed to optimise surface roughness, cutting force, and material removal rate. The findings indicate that the cutting depth exerts a significant impact on both the surface morphology and surface roughness. The available data indicates a clear correlation between the depth of cutting and the rate of feed, as well as the resulting assessment of surface roughness. Nevertheless, the first rise in spindle speed is associated with a subsequent increase in surface roughness, followed by a subsequent drop of a lesser magnitude. A minimal threshold for surface roughness has been established at 0.203μm. The spindle speed exerts the primary impact on the cutting force. There exists a positive link between the cutting force value and both the cutting depth and feed speed, as the cutting force value has a positive correlation with the incremental changes in these variables. Nevertheless, the relationship between cutting force and the observed trend is non-linear, exhibiting an initial decrease followed by a rise when cutting force is augmented. The minimal cutting force necessary was quantified as 112.3 N. Subsequently, a regression analysis was employed to develop a correlation model between surface roughness and cutting force. and machining parameters. The confirmation of the coefficients' validity in the model was achieved via the utilisation of analysis of variance (ANOVA) and residual analysis. The main goal of developing a machining parameter optimisation model is to limit surface roughness and cutting force, thereby improving operational efficiency. The NSGA-II method is utilised to tackle the problem of multi-objective optimisation, leading to the attainment of the optimal parameter solution. The purpose of the verification test is to evaluate the precision of the forecasts generated by the optimised model. The work holds importance in its analysis and juxtaposition of diverse processing factors, alongside the use of multi-objective optimization methodologies.

Wire electrical discharge machining (WEDM) was employed to process thin-walled, multidirectional carbon fiber-reinforced silicon carbide (Cf-SiC) composites. This study investigates the effects of key WEDM parameters, including gap voltage (Vg), pulse on-time (Ton), pulse off-time (Toff), and wire electrode type on material removal rate (MRR) and surface roughness (SR). All experimental planning, data analysis, optimization, and result visualization were conducted using MATLAB software. Results indicate that using CuZn50-coated wire electrodes increases MRR by 11% compared to CuZn37 bare brass wire. Scanning electron microscopy (SEM) confirmed the inverse thermal expansion-based material removal mechanism, revealing surface defects such as fiber fractures, interfacial detachment, craters, and micro-cracks. Surface roughness, as indicated by 3D topographic measurements was found acceptable with an average Ra between 2 and 3 μm. Overall, WEDM proves effective for machining Cf-SiC, especially for complex geometries such as holes, grooves, keyways, and splines when appropriate electrodes and parameters are applied.

The task of comprehensive machine care, monitoring of reliability and maintenance is currently a priority not to wait for a malfunction, but to prevent malfunctions before they occur. In the possibilities of mod-ern diagnostic tools, this activity is the task of oil analysis, which is a highly effective tool for monitoring the condition of hydraulic oils during their long-term operation. It is possible to prevent the failure of the entire system by regular monitoring of the technical condition of oils based on the analysis of hydraulic oil pollution. Oil analysis can reveal the amount of additive elements, oil pollution, the amount of addi-tives and changes in the physico-chemical parameters of the oil. In order to determine the current state of the oil filling, it is necessary to use a suitable diagnostic method. The submitted contribution de-scribes an experiment aimed at evaluating the state of hydraulic oil by means of EDX (Energy-dispersive X-ray spectroscopy) analysis, DSC (Different Scanning Calorimetry) analysis and infrared spectroscopy.

This paper introduces a customized Fused Filament Fabrication (FFF) printer, featuring an advanced electromechanical system that achieves a substantial 500% increase in printing speed compared to con-ventional FFF printers. This research scrutinizes the printer's capabilities, emphasizing the dimension-al accuracy. Specifically, this study focuses on the investigation of the effect of high printing speeds on the dimensional accuracy of linear artifacts. The material selected is Acrylonitrile Butadiene Styrene (ABS) and the FFF-fabricated parts are designed and measured based on the ISO ASTM 52902-2021 standard. Last but not least, statistical analysis and comments are following, showing remarkable re-sults on such high-speeds.

The aim of this study was to verify the laser shock peening (LSP) on the microstructure of P265GH steel and X6CrNiTi18-10 stainless steel. The LSP surface treatment was done underwater on the dis-similar weld joint of the P265GH and X6CrNiTi18-10 tubes. The metallographic analysis then focuses on the evaluation of microstructure in heat-affected zones of both materials. The results of our analysis are possibly summarised as follows. Light and scanning electron microscopy have shown grain refinement in the treated surface of the HAZ region of X6CrNiTi18-10 steel. For P265GH steel, it was possible to find a remelted surface layer with a thickness of 3.3±0.6 micrometers in the peened areas. For P265GH steel was also possible to observe a significant increase in dislocation density in the grains with straight contact with the peened surface. In the case of X6CrNiTi18-10 steel, this area extended to a depth of over 50 micrometers from the peened surface.

Additive technologies are becoming a common part of not only prototype production, but also piece or small series production. However, the choice of technology and material plays a key role in the applicability of the manufactured parts. The most widespread type of additive technology is FFF technology, which consists of applying a fused plastic string in single layers. The resulting mechanical properties of parts produced using this technology depend not only on the material and structure selected, but also on the process parameters used in the printing process itself. This study deals with the production of filament from PLA, which is the primary material. The advantage is its environmental degradability after the end of the life cycle of PLA products. However, the resulting properties of the printed parts may depend on the way the filament is prepared and in particular on the melt temperature during filament extrusion. This study investigates the effect of the produced filaments on the quality of printed parts. It has been shown that the filament production technology has a significant effect on the quality of printed parts.

Past efforts which focused on the essential monitoring of the chain tension of scraper conveyers employed in fully mechanized coal mining operations have developed innovative power solutions based on the incorporation of piezoelectric devices that generate the electrical power required for the wireless transmission of chain tension data based solely on the vibrations of the scraper conveyor itself. However, these past studies have failed to evaluate the effects of different environmental factors on the electricity generating capacity of the piezoelectric devices. The present work addresses this issue by evaluating the maximum peak-to-peak voltage generated by a variable excitation piezoelectric device experimentally under a wide range of mechanical excitations, including static applied loads of 1600 g, 3200 g, and 4800 g with added oscillatory loads of different frequencies of 1.0 Hz, 2.0 Hz, and 3.0 Hz, and displacement amplitudes of 1.0 mm, 2.0 mm, and 3.0 mm. Compared with excitation frequency and excitation load the impact of an oscillatory load amplitude increasing from 1.0 mm to 3.0 mm on the obtained peak-to-peak voltages is quite profound, where the peak-to-peak voltage of the device increases by nearly 270%. The kind of piezoelectric power generation device which can adjust many kinds of external excitation is innovatively designed. The efficient and stable power supply of the piezoelectric device to the tension detection system of the scraper conveyor is realized.

Composite materials have consistently been applied in areas where a combination of properties such as strength, stiffness, and low weight is crucial. Motorcycle construction is no exception, as these parameters significantly impact riding characteristics, safety, and overall performance. This article focuses on quantifying the torsional and vertical stiffness of a single-sided swingarm made of carbon fiber reinforced polymer (CFRP) using finite element analysis (FEA) and verifying these results through experimental measurements. To enhance the accuracy of the simulations, which involve complex geometries and anisotropic materials, the material properties of selected fabrics used in the prototype production were measured. Specific fixtures were designed for the experimental measurements, enabling the application of torsional moments and vertical forces. Deformation under these loads was evaluated using the TRITOP photogrammetric system, which tracks deformations by monitoring the displacement of reference points under static load conditions and comparing them to a reference, unloaded state. Based on the acquired data, the overall stiffness values and their distribution along the length of the swingarm were calculated. The results showed a significant difference between simulation and reality. For the overall torsional stiffness, the simulated value was 249 N·m/°, while the measured was 270 N·m/°, showing a discrepancy of 7.7%. The vertical stiffness value from simulation was 414 N/mm, compared to 411 N/mm from experimental measurements, with a minimal difference of -0.7%. The stiffness distribution along the length of the swingarm exhibited a correlation, but with notable variation in certain areas. This confirms that accurately simulating CFRP parts with complex geometries is highly challenging, partly due to the sensitivity of the manufacturing process. Therefore, verification through experimental measurement is considered good practice.

Titanium and its alloys are an important structural material in all sectors of industry. Thanks to its mechanical properties. One of the most widely used titanium alloys is the Ti6Al4V alloy. If we heat alloys for a long time in an air atmosphere, TiO2 is formed on the surface of the parts. The Ti6Al4V alloy, also referred to as Ti64, is a two-phase alloy formed by α+β solid solutions from the point of view of microstructure, it is characterized by corrosion resistance and good biocompatibility. Through heat treatment, we can improve the mechanical properties of the alloy, improve the fracture toughness, influence and reduce the internal stress and influence the machinability of the material. To achieve a longer service life of products made of this alloy, we can use the method of surface treatment, in the form of nano layers. An analysis of the Ti6Al4V alloy was performed for the cell, after heat treatment at temperatures of 650 °C and 800 °C and followed by corrosion loading in a salt fog environment. The exposure time in the corrosive environment was between 168 and 720 hours. Changes in the microstructure were ob-served and the change in microhardness in the surface layers of Ti6Al4V was described.

The article presents the method of investigating the pressure distribution on uneven surfaces, used for the development of a new, modern series of school furniture that meets the relevant health, pedagogical and legal requirements. During the examination of pressure conditions on school chairs with a flexible tactile sensor, which was primarilly developed for this purpose, exact data on the immediate differences in contact pressures between the person sitting and the seat are obtained. Based on this information, it is then possible to optimally shape the seats during their design and subsequent production according to the age of the sitters and the needs of the organizational form of teaching from the point of view of the specific character of the teaching environment. Technical parameters of the flexible tactile sensor depend on the shape and number of electrodes, as well as on the conductive inks used, they are stated and dis-cussed within the article. Due to the large number of collected data, a robot, otherwise used in teaching, was used for obtaining of individual loading characteristics of the proposed sensor. At the end of the article, the results obtained by the statistical processing of the measurements are summarized and dis-cussed.

Strength and malleability are important reasons for increasing applications of Al-Si alloys. Mechanical properties of Al-Si cast alloys depend not only on chemical composition but, more importantly, on microstructural features such as morphologies of dendritic α-rich in Al, eutectic β-rich in Si particles and other intermetallics that are present in the microstructure. The microstructure of an unmodified hypoeutectic AlSi7Mg alloy is responsible for the alloy's low strength parameters, and it limits the extent of practical applications. The mechanical properties of hypoeutectic silumins can be improved through chemical modification as well as traditional or technological processing. The improvement in mechanical properties generally has been attributed to the variations in the morphology and size of the eutectic silicon phase particles. This study presents the results of modification of an AlSi7Mg alloy with Sr, Al+ 10% Sr alloy and AlSi7Mg + 10% Sr master alloy. The tests were carried out on modified primary silumin alloy obtained at slow and fast cooling. Modifying additives in granular form and in the form of a rod were used. All additions were introduced into the alloy in an amount that guaranteed a constant strontium contribution to the modified alloy. The influence of the analyzed modifiers on the microstructure and mechanical properties of the processed alloy was presented in graphs. The modification of a hypoeutectic AlSi7Mg alloy improved the microstructure and alloy's properties. The results of the tests indicate that the microstructure and mechanical properties of the modified alloy are determined by the cooling rate of the modifier and its form. Higher parameters were obtained after modification of the AlSi7Mg alloy with a master alloy composed of Sr and AlSi7Mg alloy produced by rapid cooling and introduced in granular form.

The article is focused on the analysis of the additive technology (3D printing) applicability by using DMLS in the production of the reducing valve part, i.e. atmospheric resistor. Currently, the men-tioned part is produced by EDM in combination with soldering from the Inconel 718 steel. The use of additive technologies brings the assumption of greater flexibility and economy of production, which is verified by a set of analyzes focused on the accuracy of production and the utility properties of the mentioned part. In addition to technological aspects, such as individual production processes, economic aspects are also compared. Individual comparisons are the basis for assessing whether replacing the conventional production approach with 3D printing is advantageous in this case. The results of this assessment can subsequently be used for future applications of the considered additive manufacturing approaches in the case of similar components.

This paper aims to study the efficiency of using prefabricated layers made from plain cementitious composite materials for enhancing the flexural behavior of reinforced concrete (RC) continuous beams. The strengthening system was applied at 20 mm thickness, 150 mm width, and adequate development length. The prefabricated layers were placed in the tension cover in the positive and negative zones. All beams have the same geometric dimensions and positive and negative steel reinforcement ratios. The results showed that the prefabricated layer was deformed with the RC specimen without debonding, which enhanced the cracking patterns and distributed the crack width. A slight improvement in the strengthened beam capacity was 7% for the yielding load and 6% for the ultimate load. The energy absorption capacity of the strengthened beam decreased by 30.67%, whereas both beams achieved the same ductility index.

The aim of the research was to assess the influence of additions of different proportions of alumini-um waste chips from the machining technology on the melt quality and final properties of AlSi7Mg0.3 alloy casts. All casts were created using by gravity casting technology into preheated metal mold. The first cast was a pure AlSi7Mg0.3 alloy, followed by other samples with contents of 10, 30, 50, 70 wt.% of aluminum waste chips in the batches. All the samples were subjected to the Brinnel hardness and Vickers microhardness of solid solution of α(Al). Also, Density index was measured. At the end of research, the microstructures of the samples were analyzed using a Laser Confocal Microscope Olympus Lext OLS 5000.

FDM forming 3D printers may encounter problems such as rough printing surface and poor accuracy during operation. This study mainly utilizes the complementary advantages of piston extrusion mechanism, sliding vane pump extrusion mechanism, and plunger pump extrusion mechanism to design a parallel combination of three nozzle extrusion mechanism, and conducts simulation experiments to verify its effectiveness based on temperature distribution data comparison. It basically avoids the irregular voids and faults caused by the thermal phase change of materials passing through the nozzle during the printing process.

Over the last decades, nickel-based superalloys with TBC coatings have been used as the main material for hot section turbine parts. The next step in the development of engines and increasing the combustion temperature is the use of Ceramic Matrix Composites (CMC). Nevertheless, in the presence of water vapour or molten salts, accelerated degradation of substrate material. This problems can be pre-vented by additional layers or coatings produced on its surface, or combinations of layers and coatings that form Environmental Barrier Coatings (EBCs). The aim of the research was the preparation of sam-ples of a mixture of erbium oxide powders with silicon oxide with the addition of: polyvinyl alcohol, starch and cellulose gum. Then their technological properties were examined. A mixture with the most favourable properties was selected and sprayed using HV-APS method using with various process parameters and investigated. Conducted research showed that energy of HV-APS process is too low for synthesis of erbium disilicate in the resulting coating. The material was only melted, not vaporized. Making powder agglomerates with an average size of 150 μm with the addition of 3% PVA leads to a significant decrease in the surface area of powder grains. This results in a significant increase in flowability and allows it to be used as a charge material for APS plasma spraying.

Grinding is one of the most important processes in machining precision rotating parts. GF & GT (grinding force and grinding temperature) of single particle in grinding wheel have great influence on surface roughness. This study established the GF & GT models of single particles. Abaqus was used to analyze the coupling between GF & GT of single particle. Combined with grinding parameters (grinding depth and grinding speed), the influence of GF & GT on the range of surface roughness of single particle abrasive was comprehensively studied. The machining and experimental analysis of precision aerospace bearings were carried out through theoretical analysis. The results show that with the increase of grinding depth, the GF & GT in X and Z directions increase gradually. However, the grinding temperature does not increase linearly with the increase of grinding depth. Compared with the grinding speed, the influence of grinding depth on the grinding force in Y and Z directions is much greater than that in X, which is 7.38 times and 5.81 times of the grinding speed, respectively. Grinding depth has the greatest influence on surface roughness, which is 3.6 times the grinding speed. When the test speed is constant at
60000 rev/min, the bearing temperature is between 30 °C and 65 °C and most of them are within 44 °C. The test data meet the requirements, and all indexes are controllable. The above conclusions provide a theoretical basis and selection of process optimization parameters for grinding precision rotating parts.

The impact of thermofriction on surface hardness has been investigated in this study. The metal disk method, which hardens parts' surfaces utilizing a metal disk, creates a hardened layer with the re-quired mechanical characteristics at a precise depth. The surface of treated products is one indica-tion of quality indicators. It has been noted that the thermal conductivity of the workpiece and tool material affects the irregular dispersion of heat in the processing zone. For evaluating the average integral rates of heating and cooling of the layer, the metal dependences have a significant impact on the form and properties of the friction-strengthened layer. It is discovered that several processing mode-dependent parameters affect power and density heat flow during hardening. It was found that when the feed rate increases, the hardened layer's depth decreases. The harder layer's depth increases as disk rotation speed (rpm) increases. when the disk rotation speed is increased to 265 rpm and the hardening depth (h) is 0.2 mm or less, it is said to be at N = (190-250) rpm. After heating the treated surface areas to a temperature between 130°C and 160°C above the critical temperature, the treated surface areas were then cooled applying compressed air to achieve the ideal surface hardness. After the hardening process, the surface hardness of blanks made of steel 1045 reached HRC 60, which is higher than conventional hardening.

The article highlights the promising potential of automating the forging process to enhance the durability of multi-cavity forging tools. Entrepreneurs aim to boost production efficiency by increasing output per unit of time and reducing the degradation of forging dies and punches. The high costs associated with specialized materials and complex manufacturing processes for these tools elevate the final product price. Automation offers a viable alternative, ensuring consistent process parameters and reducing the physical strain on workers. This consistency leads to extended tool durability, even without the use of special manufacturing techniques for their production. The study simulates the durability of multi-cavity dies in automated operations, demonstrating substantial advantages compared to manual forging. Simulation programs for forging processes and tool durability offer significant cost savings by providing insights into potential fatigue cracks, aiding in decision-making, and verifying operational parameters and tool designs. These simulations reduce the need for extensive: real-world tests and modifications of the forging tools.

The propagation and velocity of the deformation wave in the thin isotropic plate is investigated. The deformation is induced by the stroke of impact body onto the facial surface of the plate. The plate is supported perpendicularly. The excitation of the plate oscillation is initialized by a unit force (Heavi-side’s jump). The impact body has a rounded facet by radius c = 2.5 mm. Hook's material model and Kirchhoff’s and Flüegge’s geometric model have been investigated. The analytical solutions for both models are presented. The MATLAB script has been assembled to solve material and geometrical mod-els. The results were compared for two selected points on the surface of the plate. Plate deformation was recorded at two points T1 (at a distance of 20 mm from the impact location on the x axis) and T2 (at a distance of 20 mm from the impact location on the y axis).

This paper deals with the issue of selecting different machining parameters in the CAM system Siemens NX 1946. The issue of choosing between a solid end mill, milling cutter, and a high-feed tool when machining simple rectangular and rugged cavities concerning time and residual material is solved here. The chosen material was 1.1730, which is a basic material for the production of moulds without heat treatment. The paper deals with the issue of choosing the size of tool feed into the cut and its influence on the formation of the machining path depending on the depth of the cavity. The size of the residual material depends on the machining strategy and the choice of the plunge method into the material with regard to the total machining time. Performed simulations and experiments have shown a significant impact in individual settings and, thus, on the cost of machining components of such shapes.

Binderjetting technology works on the principle of line injection moulding, using metal powder and liquid binder as input material, which is uniformly applied by print heads to the previous layer using a nozzle. By successively applying each layer, the desired shape of the designed component is obtained. The technology offers a large number of advantages which include the possibility of using any printing powder that may contain functional graded materials. Furthermore, it is a green manufacturing technology where we can reuse unused metal powder in the next printing cycle after following the prescribed process. As a result, we characterize this technology as a near-waste-free production of metal parts. The research aims to analyse the impact of different orientations of printed parts within the workspace on the mechanical properties of the resultant components. Additionally, the study aims to compare these mechanical properties with the specifications recommended by the metal powder manufacturer and findings from previous research studies. Based on the experimental measurements carried out, we can conclude that the influence of the orientation of the parts in the workspace has only a minimal effect on the mechanical properties of the manufactured parts.

This article explores the significance of microtexturing on cutting tools for improved tribological performance and reduced friction in machining operations. Drawing inspiration from biomimetic structures, the study focuses on laser surface microtexturing and evaluates its impact on cutting forces and tool wear. Experiments involve microtextures of dots with a specific emphasis on a fiber laser-processed pattern. While long-term tests reveal the formation of negative protrusions on the textured tools, reduced variability in cutting forces suggests potential benefits for stable machining processes and increased tool longevity. The findings underscore the intricate relationship between microtexturing patterns and tool performance, offering insights into the broader implications for energy-efficient machining.

The paper focuses on a novel and perspective surface treatment technology called Plasma Electrolytic Oxidation (PEO) applied to aluminium and its alloys. This innovative technology generates layers with specific properties, particularly suitable for tribological and heat-resistant applications. Plasma Electro-lytic Oxidation technology represents an alternative to conventional oxidation methods, offering high utility properties and presenting a completely new approach to surface modification.

Reinforcement steel rebar is produced by several ways but most importantly the tempcore process. Due to mass production in steel rolling plants, the rebars are gathered after tempcore process at a specific temperature in bundles stack in the warehouse. The bundling temperature varies from 200 to 300 o C. The rebars need relatively long time, up to one day, to reach the room temperature in the bundles stack. This work investigates the effect of prolonged ageing time on the rebars mechanical properties after the tempcore process of both ageing in bundle and designed artificial ageing. The results of mechanical properties of ageing in bundle compared to the artificial ageing were found to be in good agreement. The yield and tensile strengths were found to decrease by 6.3 and 2.1 %, respectively, due to artificial ageing. However, the elongation and the tensile to yield ratio increased by 17.6 and 4.8 % respectively.

The paper presents the analysis of the gantry crane loading when driving along the crane track, using a 3D model, for which the analysis of the gantry crane frame loading was performed. The gantry crane is designed to remove dirt that is in front of the turbine under the water surface. For the gantry crane which moves along a track, the directional and vertical unevennesses were determined by experiment and are given in graphic and numerical form in (mm), relating to A track and B track with a total track length of 450 (m). Based on the knowledge of the unevenness of the rail track, the four random functional dependencies defining the irregularities of the individual rails as input variables were used for the kinematic excitation of the individual wheels of the gantry crane. The stress analysis was performed for a travel speed of 30 (m/min) and a lift of 10 (t) under the given loading. The results of the stress analysis are presented in graphic form.

The tempering procedure of quenched 54SiCr6 spring steel was analyzed using continuous heating dilatometry, isothermal dilatometry, metallography, and hardness measurement. The dilatometry was performed on four different steel modifications with graduated Si content and with two levels of Cu. Metallography and hardness measurement were analyzed only on samples with one Si level. Two types of tempering procedures were compared in this experimental program. The first one was sim-ple one-step tempering, the other was a special procedure of strain assisted tempering (SAT), which includes double tempering and strain applications between tempering. A dilatometry analysis with the support of metallography contributes to the material behaviour explanation, which is considerably different in both processing cases.

This study deals with influence of temperature and time of austenitization on final mechanical proper-ties, especially hardness, obtained after heat treatment of steel 1.3520. Following process parameters of heat treatment were varied: time of austenitization and type of cooling medium, which has a significant effect on final structure, thus mechanical properties. These parameters were varied according to reccomended range given in material sheet. As can be seen from results, different temperature and time of austenitization influenced final hardness after quenching and tempering. Lower temperature and shorter time of austenitization led to insufficient homogenization of austenite and incomplete transformation to martensite and bainite, which resulted in lower hardness. On the other hand, higher temperature and longer time of austenitization can lead to coarser austenite grain, which can also result in lower hardness.