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EN
Water is used as working fluids in hydro and thermal power engineering, as well as in heat supply and cooling systems. In the process of heating water in water-heating boilers, scale forms due to the precipitation of crystals of mineral additives and mineral salts. Over time, the accumulation of scale with low thermal conductivity leads to a decrease in the internal diameter of the pipes. Consequently, the flow of liquid is hindered, the hydraulic resistance increases and the thermal conductivity of the device decreases. The scale layer is usually removed by acid washing of the internal heat exchange surfaces or mechanical washing. However, both methods involve the use of a substantial amount of chemicals and result in highly polluted wastewater. In addition, it significantly increases operating costs. The article uses statistical methods for processing experimental data, and generally accepted methods for conducting experiments to study the patterns of scale formation using control and measuring instruments and accurate methods for measuring technological parameters. The main purpose of the paper is to study the influence of a constant magnetic field on the formation of mineral salts deposits on the surface of walls of thermal appliances used in chemical, oil refining, and food processing industry. The influence of a constant magnetic field on the formation of scale on the surface of the walls of the heating element in a water heater has been established. According to the results of an experiment aimed at preventing the accumulation of mineral salt deposits on the surface of the heating element in a water heating boiler under the influence of a magnetic field, the amount of mineral salt precipitate deposited on such surface can be reduced up to 5.2 times. Consequently, the prevention of mineral scale formation is achieved, eliminating the need to use expensive chemicals. The stable operation of the devices contributes to enhanced thermal efficiency. Under the influence of a magnetic field, scale formation decreases on average by a factor of 5, as long as the water temperature does not exceed 70°C. However, if the temperature rises above 90°C, the scale formation rate gradually increases.
PL
Woda jest wykorzystywana jako płyn roboczy w energetyce wodnej i cieplnej, w systemach ciepłowniczych i chłodniczych. W procesie podgrzewania wody w kotłach wodnych powstaje kamień kotłowy w wyniku wytrącania się kryształów dodatków mineralnych i soli mineralnych. Z biegiem czasu wzrost grubości kamienia o niskiej przewodności cieplnej prowadzi do zmniejszenia wewnętrznej średnicy rury. W rezultacie przepływ cieczy staje się utrudniony, wzrasta opór hydrauliczny i maleje przewodność cieplna urządzenia. W celu usunięcia warstwy kamienia stosuje się zwykle mycie kwasem wewnętrznych powierzchni wymiany ciepła lub oczyszczanie mechaniczne. Wszystkie te metody wiążą się z użyciem dużej ilości chemikaliów i wytwarzaniem mocno zanieczyszczonych ścieków. Ponadto znacznie zwiększają one koszty eksploatacji. W artykule zastosowano metody statystyczne przetwarzania danych eksperymentalnych oraz ogólnie przyjęte metody prowadzenia eksperymentów do badania przebiegu powstawania kamienia kotłowego za pomocą przyrządów kontrolno-pomiarowych oraz dokładne metody pomiaru parametrów technologicznych. Głównym celem pracy jest zbadanie wpływu stałego pola magnetycznego na powstawanie osadów soli mineralnych na powierzchni ścianek urządzeń cieplnych stosowanych w zakładach przemysłu chemicznego, rafineryjnego i spożywczego. Określono wpływ stałego pola magnetycznego na powstawanie kamienia kotłowego na powierzchni ścianek elementu grzejnego podgrzewacza wody. Zgodnie z wynikami eksperymentu mającego na celu zapobieganie osadzaniu się osadów soli mineralnych na powierzchni elementu grzejnego w kotle wodnym pod wpływem pola magnetycznego, ilość osadów soli mineralnych osadzonych na powierzchni elementu grzejnego kotła wodnego można zmniejszyć nawet 5,2-krotnie. W rezultacie zapobiega się tworzeniu kamienia kotłowego i nie stosuje się drogich chemikaliów. Sprawność cieplna urządzeń osiągana jest dzięki możliwości stabilnej pracy urządzenia. Tworzenie się kamienia pod wpływem pola magnetycznego zmniejsza się średnio 5-krotnie, dopóki temperatura wody nie przekroczy 70°C. Jednakże, gdy temperatura wzrośnie powyżej 90°C, tempo tworzenia się kamienia stopniowo wzrasta.
EN
In Kosovo, the supply of potable water from water sources is represented by about 40%. This study represents the geochemical analyses of sediments, spatial and statistical analyses of major elements in sediments (fraction <63 µm) of water sources in the Drini i Bardhë River basin. For a better understanding of the geochemical consistency of sediments, inductively coupled plasma-mass spectrometry (ICP-MS) was used and the amounts of P and S were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). By comparing the concentrations of Ba, Se, and P with the existing criteria, it was found that 26 of 50 sample points exceed recommended norms, which cause low/significant toxic effects and 23 of 50 sample points include anomalies of the analyzed elements. In terms of statistical interpretation, the average concentration of the studied elements decreased in such order: Ca > Al > Mg > K > S > P > Na > Ba > Sr > Li > Rb > B > Ga > Cs > Be > Se. In terms of correlation analyses, elements such as Li, Be, Mg, P, and Ba did not show a significant positive correlation with any element. Cluster analysis of R-modality shows a branch of dendrogram linked with Ca, Al, Mg, S, K, P, Na, Ba, Sr, Cs, B, Ga, Se, Be, Rb, and Li. Spatial distribution maps of major elements show that high concentrations of Li, Ca, and Ba were located mostly in the northern part, high concentrations of B, Na, Mg, Sr, and Cs were located in the north-east part, high concentrations of Be and Al were located in the north and south part and high concentrations of P, S, K and Rb were located mostly in the south-east part of the catchment basin. This high concentration of elements is impacted by the lithology of rocks and by the minor influence of human activity (the case of P).
EN
In the geological structures containing crude oil and associated gases and located in areas where volcanic activity has been detected, radioactive substances and minerals are contained both in the structure of the reservoir waters and in the impurities related to the composition of the extracted crude oil. They are present during the extraction of crude oil and associated gases and affect human health and environmental safety. Radioactive elements have been detected in reservoir waters, in impurities associated with crude oil, and especially during the processing of drilling fluids (the separation of detritus sourced from geological strata from the used drilling fluid). Other radioactive elements were also detected in the areas polluted with oil and drilling waste. In order to determine the radioactivity level of crude oil originating from the area of volcanic activity of the Romanian Mountains, crude oil samples were collected from the oil field in a one-year analysis. The collected samples were analysed to determine their physical-chemical structure. The reservoir water associated with these samples and the minerals separated from the crude oil following their solvent extraction were also analysed. Radioactive elements were detected using X-ray spectrometry, and their chemical structures are also discussed.
PL
W strukturach geologicznych zawierających ropę naftową i towarzyszący jej gaz ziemny oraz zlokalizowanych w obszarach, w których wykryto aktywność wulkaniczną, substancje i minerały radioaktywne zawarte są zarówno w strukturze wód złożowych, jak również w zanieczyszczeniach powiązanych ze składem wydobywanej ropy. Są one obecne podczas wydobycia ropy naftowej i towarzyszącego jej gazu, mając wpływ na zdrowie ludzkie i bezpieczeństwo środowiska. Pierwiastki radioaktywne wykryto nie tylko w wodach złożowych i związanych z nią zanieczyszczeniach, ale przede wszystkim podczas obróbki płuczek wiertniczych, w tym w procesie oddzielania detrytusu pochodzącego z warstw skalnych od zużytej płuczki wiertniczej. Inne pierwiastki radioaktywne wykryto także w obszarach zanieczyszczonych ropą i odpadami wiertniczymi. Dla określenia poziomu radioaktywności ropy naftowej pochodzącej z obszaru aktywności wulkanicznej w górach Rumunii, z jednego ze złóż ropnych w ciągu jednego roku pobrano próbki ropy naftowej do analiz. Pobrane próbki przeanalizowano pod kątem struktury fizykochemicznej. Przebadano także wodę złożową powiązaną z tymi próbkami oraz minerały oddzielone z ropy naftowej po ich ekstrakcji rozpuszczalnikiem. Pierwiastki radioaktywne zidentyfikowano za pomocą spektrometrii rentgenowskiej, omówiono również ich struktury chemiczne.
EN
In the context of resource utilization, the applications of waste biomass have attracted increasing attention. Previous studies have shown that forming biochar by heat treatment of sludge could replace the traditional sludge disposal methods, and sludge biochar is proved to be efficient in wastewater treatment. In this work, the pyrolysis, hydrothermal carbonization and microwave pyrolysis methods for preparing sludge biochar were reviewed, and the effects of different modification methods on the performance of sludge biochar in the synthesis process were comprehensively analyzed. This review also summarized the risk control of heavy metal leaching in sludge biochar, increasing the pyrolysis temperature and use of the fractional pyrolysis or co-pyrolysis were usually effectively meathods to reduce the leaching risk of heavy metal in the system, which is crucial for the wide application of sludge biochar in sewage treatment. At the same time, the adsorption mechanism of sludge biochar and the catalytic mechanism as the catalytic material in AOPs reaction, the process of radical and non-radical pathway and the possible impacts in the sludge biochar catalytic process were also analyzed in this paper.
EN
West Papua province in eastern Indonesia is positioned in a dynamic tectonic zone along with the collision of the Australian, Pacific, and Eurasian plates. The interaction resulted in the formation of strike-slip faults such as Koor, Sorong, Ransiki, and Yapen, that are prone to earthquakes in the region. The rocks of West Papua in the northern part are a contribution to the Pacific Ocean plate consisting of ophiolite and volcanic arcs of the archipelago, even while the rocks of the Australian plate in the southern part are dominated by quaternary and siliciclastic sedimentary. It has a wide variety of resources, including oil and gas. This study combines the interpretation of regional gravity and magnetic data derived from satellite observations to identify the subsurface structure of West Papua. This is performed since most studies were conducted on the surface and did not significantly focus on the subsurface. The composition of subsurface is determined through three-dimensional (3-D) unconstrained inversion modeling using the iterative reweighting inversion of regional gravity and magnetic anomalies as a function of density contrast and magnetic susceptibility of rocks. In depth variations, gravity inversion produces density contrast ranging from −0.348 to 0.451 gr/cm3 , whereas magnetic inversion provides rock susceptibility varying between −0.363 and 0.223 SI. Gravity and magnetic inversions characterize the subduction of the Pacific Ocean plate in the north, extensive intrusion of igneous rocks, and low density-susceptibility contrast in the Bintuni basin as a source of oil and natural gas. The boundary between the sediment layer and the basement is believed to be 15–20 km deep, with rocks from the uplifted mantle in the north and a Silur-Devon aged Kemum formation in the south.
EN
The Gondwana Late Palaeozoic Ice Age is probably best represented by the Dwyka Group in South Africa. Striated and grooved surfaces or pavements are commonly considered to have formed subglacially, as are diamictites which have been interpreted as in-situ or reworked tillites. These interpretations were tested by investigation of outcrops in formerly well-studied areas, throughout South Africa. Detailed analyses have focused on striated surfaces/pavements and surface microtextures on quartz sand grains in diamictites. The sedimentological context of four pavements, interpreter to be glaciogenic, display features commonly associated with sediment gravity flows, rather than glaciation. A total of 4,271 quartz sand grains were subsampled from outcrops that are considered mainly to be tillites formed by Continental glaciation. These grains, analysed by SEM, do not demonstrate the characteristic surface microtexture combinations of fracturing and irregular abrasion associated with Quaternary glacial deposits, but mainly a mix of surface microtextures associated with multicyclical grains. The Dwyka Group diamictites warrant reinterpretation as non-glacial sediment gravity flow deposits.
7
Content available remote Types and valorization of sludge generated in water treatment processes
EN
This paper is a study on the problem of sludge formation in water treatment processes. Various physical and chemical processes used in technological systems of water treatment were described and those which are the source of sludge were indicated. The chemical composition of the sludge was presented, with particular emphasis on hazardous organic and inorganic pollutants. An essential part of the work was to consider the possibilities and ways of valorizing sludge. It was deter- mined that the type of generated sludge depends on the applied process and its pollution degree depends on the type and quality of the water taken. Most of the sludge is formed during the coagulation process of surface waters, which may be contaminated with various heavy metals. Among the possibilities and methods of sludge valorization, an interesting way to use it is in construction, as an admixture to various building materials. It is also possible to use sludge as an unconventional adsorbent or reaction catalyst in the oxidation of organic pollutants present in wastewater.
EN
This study describes the settling velocity phenomenon and deals with the methods for its estimation. The accuracy of three previously proposed settling velocity equations is also checked in this study. After graphical and statistical analysis, the authors proposed generalized reduced gradient (GRG) and hybrid generalized reduced gradient–genetic algorithm (hybrid GRG-GA) approaches for the estimation of settling velocity. Hybrid GRG-GA-based settling velocity approach showed more precise results than GRG approach. In addition, hybrid GRG-GA and GRG approaches were compared with previously proposed equations using 226 data points. The graphical and statistical analysis shows that the hybrid GRG-GA and GRG approaches give better agreement with observed data points as compared to previously proposed equations. Application of hybrid GRG-GA reduces the sum of square of error in fall velocity by over 70% and 30% on an average as compared to previous equations during training and testing, respectively. This study highlights that the hybrid GRG-GA approach could be efficiently used for calculating the settling velocity.
PL
W kopalniach podziemnych woda pochodząca z naturalnych dopływów oraz woda technologiczna pochodząca głównie z sieci rurociągów przeciwpożarowych gromadzona jest w osadnikach znajdujących się najczęściej na najniższym poziomie kopalni. Zwykle jest to woda zanieczyszczona mechanicznie. Gromadzenie się osadu odbywa się na zasadzie sedymentacji. W artykule przedstawiono metodę oczyszczania osadników wód kopalnianych opartą na zasadzie hydrourabiania i hydrotransportu oraz sposób segregacji na część stałą, czyli osad, i wodę. Konsystencja otrzymanego osadu pozwala na jego transport, np. za pomocą przenośnika, a woda może być ponownie wykorzystana w procesie hydrourabiania osadu. Do tego celu stosuje się urządzenia z serii ZEKO.
EN
In mines, water from natural inflows as well as process water from fire protection systems is usually stored in sedimentation tanks, located primarily at the lowest level of the mine. Such water usually contains mechanical contaminants, undergoing the process of sedimentation. The article presents a method enabling the cleaning of mine water sedimentation tanks. The method involves jet mining, hydrotransport and segregation into sediment (i.e. the solid fraction) and water. The consistence of sediment obtained after segregation makes the former transportable (e.g. using an appropriate conveyor/feeder), whereas water can be reused subsequently in the jet mining of sediment. One of the solutions enabling the performance of the above-named process is a ZEKO series system
EN
In mines, water from natural inflows as well as process water from fire protection systems is usually stored in sedimentation tanks, located primarily at the lowest level of the mine. Such water usually contains mechanical contaminants, undergoing the process of sedimentation. The article presents a method enabling the cleaning of mine water sedimentation tanks. The method involves jet mining, hydrotransport and segregation into sediment (i.e. the solid fraction) and water. The consistence of sediment obtained after segregation makes the former transportable (e.g. using an appropriate conveyor/feeder), whereas water can be reused subsequently in the jet mining of sediment. One of the solutions enabling the performance of the above-named process is a ZEKO series system.
PL
W kopalniach podziemnych woda pochodząca z naturalnych dopływów oraz woda technologiczna pochodząca głównie z sieci rurociągów przeciwpożarowych gromadzona jest w osadnikach znajdujących się najczęściej na najniższym poziomie kopalni. Zwykle jest to woda zanieczyszczona mechanicznie. Gromadzenie się osadu odbywa się na zasadzie sedymentacji. W artykule przedstawiono metodę oczyszczania osadników wód kopalnianych opartą na zasadzie hydrourabiania i hydrotransportu oraz sposób segregacji na część stałą, czyli osad, i wodę. Konsystencja otrzymanego osadu pozwala na jego transport, np. za pomocą przenośnika, a woda może być ponownie wykorzystana w procesie hydrourabiania osadu. Do tego celu stosuje się urządzenia z serii ZEKO.
PL
Celem niniejszego artykułu jest przedstawienie problemów związanych z eksploatacją kotłów parowych o ciśnieniu roboczym do 20 barów. Szczególną uwagę zwrócono na wymagania jakości wody zasilającej kotły parowe, jak też problem odsalania oraz oszczędności wody i ciepła. Wskazano technologie uzdatniania wody, najbardziej opłacalne w zastosowaniu.
EN
The aim of this paper is to present problems connected with exploitation of steam boilers with pressure up to 20 bars. Particular emphasis is put on the quality of steam boiler feed water, on desalting problems, water and heat savings. Water treatment technologies are indicated, the most cost-effective in application.
PL
Celem niniejszego artykułu jest przedstawienie problemów związanych z eksploatacją kotłów parowych o ciśnieniu roboczym do 20 barów. Omówiono przyczyny wytrącania się osadów kamienia kotłowego i korozji. Szczególną uwagę zwrócono na wymagania dotyczące jakości wody zasilającej kotły parowe, jak też na problem odsalania oraz oszczędności wody i ciepła.
EN
The aim of this paper is to present problems connected with exploitation of steam boilers with pressure up to 20 bars. Reasons of boiler scaling and corrosion are described. Particular emphasis is put on the quality of steam boiler feed water, on desalting problems, water and heat savings.
EN
Purpose: Due to an increase in a number of bridges being constructed, scour depth around bridge piers is gradually being recognized as one of the possible reasons for bridge failure. According to [1] about 53% of bridge failures in the US were caused due to floods and corresponding scour in the rivers. Lots of work has been carried out around the single pier but in the case of group piers, the work is very less. Hence, it becomes necessary to calculate the actual scour depth around the bridge piers considering the close location of bridges as well. Design/methodology/approach: Recognizing the need for research in this direction, an experimental study was planned and conducted in the Hydraulics Laboratory of Civil Engineering Department of National Institute of Technology Kurukshetra, India. Experiments were conducted in a standard recirculating tilting bed water flume 15 m long, 0.4 m wide, and 0.60 m deep. The orientation of more than one pier, namely Tandem pattern was employed for the work. Two pier models, 62 mm and 42 mm diameter were used for the experimental study. The mobile bed used in the experiments had an average mean size, d50 = 0.23 mm, 0.30 mm and 0.50 mm. Findings: The outcomes of the ANN function and M5 model analysis have been used to compare with experimental results. From the earlier studies, it was concluded that, when the clear spacing between the pier models was greater than 0D the scour depth around the piers increase with a rapid rate. However, in the case of modelling techniques, M5 models show higher predictive accuracy than ANN models. Research limitations/implications: It is a significant area of research. However, the present study has been a time and facility- constrained study. Therefore, there is a large scope to conduct further studies on the subject, Different pattern i.e. Side by Side; Staggered and Group of piers can be adopted for further investigations. Originality/value: Sufficient work has been done by number of researchers around the single bridge pier. But due to rapid urbanization a number of bridges constructed in close proximity to each other which affects the scour depth of each other. Modelling techniques used in hydraulic engineering are not always effective in practice. The present study discusses the effect of spacing on scouring around piers in a tandem arrangement using experimental as well as modelling techniques. To predict the scour depth of the Tandem arrangement 89 laboratory data sets have been used.
EN
Throughout the world, considerable quantities of water treatment sludge (WTS) and sewage sludge (SS) are produced as waste. This study assessed in the laboratory, the possibility to use both waste products when they are incorporated as filler at 1% with relation to the total mass of a hot mix asphalt - HMA. To this end, both waste products were initially reduced to ash through a calcination process. Resistance tests under monotonic load (Marshall and indirect tension tests), and cyclic load (resilient modulus test) were applied on mixes that contained WTS and SS. Besides, moisture damage (modified Lotmman test), and abrasion (Cantabro) resistance were assessed. An analysis of variance (ANOVA) test was performed in order to verify if the results are statically equal or not to those of the control HMA. As a general conclusion, it is reported that both materials show a resistance increase under monotonic load and higher stiffness under cyclic load (cohesion) when they are incorporated into the mix as filler despite the fact that the asphalt content used was less than the control mix. However, some problems are observed associated with moisture damage resistance, and friction wear (adherence).
EN
This study investigated the multifractality of streamfow data of 192 stations located in 13 river basins in India using the multifractal detrended fuctuation analysis (MF-DFA). The streamfow datasets of diferent river basins displayed multifractality and long-term persistence with a mean exponent of 0.585. The streamfow records of Krishna basin displayed least persistence and that of Godavari basin displayed strongest multifractality and complexity. Subsequently, the streamfow-sediment links of fve major river basins were evaluated using the novel multifractal cross-correlation analysis (MFCCA) method of cross-correlation studies. The results showed that the joint persistence of streamfow and total suspended sediments (TSS) is approximately the mean of the persistence of individual series. The streamfow displayed higher persistence than TSS in 60% of the stations while in majority of stations of Godavari basin the trend was opposite. The annual cross-correlation is higher than seasonal cross-correlation in majority of stations but at these time scales strength of their association difers with river basin.
EN
The model reclamation process of the studied fly ash deposits has been started in 2003 by formation of five different experimental surface layers containing fly ash and organic matter in various combinations. Then, grass mixture was sown on these surface layers. In 2015, selected properties of plant communities growing on different variants of surface layers applied in the reclamation process were assessed. It was assumed that the type of mineral and organic substrates used in the process and their quality were the main factors affecting the long term plant diversity present on different variants of restored surfaces. The aim of this analysis was the assessment of the effectiveness of ash waste reclamation (carried out on five different types of the surface layer) after 12 years since its initiation. The long term results of the reclamation process showed that the applied surface layers allowed for an effective reclamation of ashes since all variants of experimental surfaces were totally covered by dense vegetation. The predominance of plant species from ruderal and segetal habitats indicated that the soil of the experimental habitats was fertile with neutral and slightly alkaline pH, and texture of sandy loams. The experimental surface layers with a texture of sand of favourable C:N ratio, neutral or slightly alkaline did not limit the plant development. The use of organic waste markedly contributed to the floristic diversity of the spontaneously developed vegetation. Coniferous bark used in some experimental variants had a marked effect on their floristic distinctiveness due to the presence of species preferring habitats of lower pH values.
EN
Composting of sewage sludge together with green waste such as grass, leaves, branches, etc. is carried out in Poland on many objects. A common problem of all exploiters is the selection of the type of composting technology and its modification to the conditions prevailing in a particular region because the waste, that given objects are exposed to, is different which makes it necessary to adapt the technology to the conditions prevailing in the given facility. In the field of technological research of the composting process, the expected effect of the research was the characteristics of conditions for composting organic waste in relation to the efficiency achieved, indication of the optimal technological parameters and assistance in the selection of the target composting technology. The waste composting technology is based on the appropriate selection of the composition of the prisms and the periodic transfer of the piles by means of a specialized turning machine. For the purpose of the study project, the following research problem was formulated: what is the intensity of the composting process depending on the technological parameters of the prism (the size of the prism, the types of waste), the properties of the waste, the intensity of aeration by turning? According to the above basis, the following research hypotheses were identified: − the intensity of composting decreases with the increase of the cubic capacity (height) of the prism, − the intensity of composting decreases with the decrease in the frequency of waste transfer, − the intensity of composting decreases as a result of the application of organic waste.
PL
Kompostowanie osadów ściekowych wraz z odpadami zielonymi takimi jak trawa, liście, gałęzie itp., prowadzona jest w Polsce na wielu obiektach. Wspólnym problemem wszystkich eksploatatorów jest wybór rodzaju technologii kompostowania oraz jej modyfikacja do warunków panujących w danym regionie, ponieważ odpady trafiające na poszczególne obiekty różnią się od siebie, co powoduje konieczność dopasowania technologii do warunków panujących na danym obiekcie. W zakresie badań technologicznych procesu kompostowania spodziewanym efektem badań była charakterystyka warunków prowadzenia kompostowania odpadów organicznych w relacji do uzyskiwanych efektywności, wskazanie optymalnych parametrów technologicznych oraz pomoc w doborze docelowej technologii kompostowania. Technologia kompostowania odpadów oparta jest na odpowiednim doborze składu pryzm oraz okresowym przerzucaniu pryzm za pomocą specjalistycznej przerzucarki. 60 Na potrzeby projektu badań sformułowano następujący problem badawczy: jaka jest intensywność procesu kompostowania w zależności od parametrów technologicznych pryzmy (wielkość pryzmy, rodzaje odpadów), właściwości odpadów, intensywności napowietrzania poprzez przerzucanie? Na tej podstawie zidentyfikowano następujące hipotezy badawcze: − intensywność kompostowania maleje wraz ze wzrostem kubatury (wysokości) pryzmy, − intensywność kompostowania maleje wraz ze spadkiem częstotliwości przerzucania odpadów, − intensywność kompostowania maleje w wyniku stosowania zagnitych odpadów organicznych.
EN
In the presented investigation, cold-rolled sheets of a selected dual-phase (DP) steel were heat-treated according to varying thermal profiles, thus reproducing continuous annealing process. Initially the samples were soaked at 780 and 810 °C for 0–60 s followed by water cooling. Next, samples were preliminary treated by applying the same conditions, however after water cooling these compositions were subject to tempering at 230, 380 and 460 °C for both 60 and 240 s. The characterization of the effect of heat-treatment parameters on the mechanical properties and structure is the main objective of this investigation. Mechanical properties of the samples after applied thermal profiles were in line with those requirements imposed on the commercial sheets of DP steels. The obtained results of the investigation showed that tempering deteriorates the Yield Ratio, defined as Rp0.2/Rm. This was caused by the martensite decomposition combined with carbide precipitation processes. Transmission electron microscopy observations revealed precipitated carbides, Fe3C in martensitic and M7C3 in ferritic areas. The quantitative results of the structural investigation were then applied to predict the Rp0.2 and Rm using the Perlade model. The results indicate that discrepancies between the measured tensile tests and calculated Rp0.2 and Rm do not exceed 10%.
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