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1

Evaluation of Structural Powder Steel Properties after High-Temperature Thermomechanical Treatment and Finish Turning

Leksycki Kamil, Feldshtein Eugene, Maruda Radosław, Dyachkova Larisa, Szczotkarz Natalia, Zverko Alexandra

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 1

26--35

EN

High-temperature thermo-mechanical processing (HTTMP) is a combination of plastic deformation and heat treatment operations. Such action makes it possible to increase metal mechanical properties resulting from both mechanical strengthening and heat treatment. As a result, it is possible to achieve high complex of operating characteristics of different types of steel and other alloys. However, there is a lack of information on the applicability of HTTMP of powder steel. These types of steel are very effective substitutes for traditional structural steel but are characterized by poor mechanical properties. This study considers the possibility of using HTTMP for powder steel frame additionally infiltrated by bronze with MoS2 addition to increase mechanical properties of the materials studied. Steel infiltrated, infiltrated and then hardened, infiltrated and then HTTMP treated with strain rates of 30, 50 and 70% were compared. The microstructural properties and hardness of the materials before machining were studied as well as the cutting forces and surface topography of those materials after turning with AH8015 carbide inserts. Cutting forces tests were realized with vc = 157 m/min, f = 0.25 mm/rev and ap = 0.25 mm. Surface topography tests were carried out with vc = 157 m/min, f = 0.25 mm/rev and ap = 0.25 mm. Constant cutting parameters were used to eliminate the effects of rest factors. It was found that the lowest cutting forces (Fc, Fp and Ff), surface roughness parameters (Sa and Sq) and small areas with single high peaks on the machined surface were obtained for infiltrated powder steel with subsequent HTTMP machining under 50% strain rate.

2

Method of experimental study of the force-deformation characteristics of the Belleville spring of the stop assembly of a direct-flow gate valve

Hasanov Ilman I., Guliyev Agali A., Tanriverdiyev Yusif A.

Nafta-Gaz

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2023

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R. 79, nr 11

742--748

EN

The article presents research methods and appropriate equipment for conducting experiments, as well as the analysis of the results. Studies on the hardness of the microstructure, elastic deformation and parts and samples were carried out using hardness testers, microscopes PMT-3, MIM-8 and devices for measuring the “force-strain” characteristic. The results of the study wer used to establish the dependence of the elastic properties of Belleville springs on the heat treatment modes, while also determining the microstructure and layer depth using various research methods. Every work studying the elastic properties and measurement of the static compressive force of a spring at a given strain value has been studied theoretically. Depending on the operating conditions, disc springs can be installed singly or assembled into packages, forming an elastic element working under compression. The research materials will be used in the work to improve the tightness of straight-through valves and the durability of the shut-off assembly parts. The dependence of the spring compression force and its deformation on the geometrical parameters of the disc springs has been established. Comparison of experimental and theoretical dependences has been made. It has been established that the residual deformation of the Belleville spring after captivity has a negative effect on the tightness of the shut-off valve assembly. The influence of various technological processes and modes of thermal treatment of disc springs on their elastic properties has been studied. Practical recommendations for improving the technological process of thermal treatment of Belleville springs have been proposed. The tasks of further research and implementation of the obtained results have been determined. Search work has been carried out to improve the technology of hardening processing of parts of the shut-off unit (gate and seat) of direct-flow valves. The possibility of using accelerated nitrocarburizing in a triethanolamine medium with induction heating by high-frequency currents at a temperature range of 950°С for boriding and borochroming has been established. Samples were made from standard steel grades 40, 40Kh and 38Kh2MYuA, subjected to hardening by the considered methods, and a study was made of the hardness, depth and microstructure of the hardened layer. Research in this direction should be continued in order to study the tribological characteristics (friction coefficient and wear resistance) of hardened parts. Each operation of the spring manufacturing technology has been studied, and deviations that have a significant impact on the operation of the spring and the sealing of the shut-off valve assembly have been identified.

PL

Artykuł przedstawia metody badawcze i odpowiednie wyposażenie służące do przeprowadzania eksperymentów, a także analizę wyników. Badania przyprowadzono przy użyciu testerów twardości, mikroskopów PMT-3, MIM-8 oraz urządzeń do pomiaru charakterystyki “siła-odkształcenie”. Wyniki tych badań wykorzystano do ustalenia zależności właściwości elastycznych sprężyn Belleville od parametrów obróbki cieplnej, jednocześnie określając mikrostrukturę i głębokość warstwy za pomocą różnych metod badawczych. Każdy przypadek badania właściwości elastycznych i pomiaru statycznego siłowego odkształcenia sprężyny przy danej wartości odkształcenia był analizowany teoretycznie. W zależności od warunków pracy sprężyny tarczowe mogą być montowane pojedynczo lub w pakietach, tworząc element elastyczny podlegający ściskaniu. Materiały badawcze mogą zostać wykorzystane w pracach mających na celu poprawę szczelności zasuw oraz trwałości części zespołu zamykającego. Ustalono zależność między siłą kompresji sprężyny i jej odkształceniem a parametrami geometrycznymi sprężyn tarczowych. Dokonano porównania wyników eksperymentalnych i teoretycznych. Ustalono, że szczątkowe odkształcenie sprężyny Belleville po jej zamontowaniu ma negatywny wpływ na szczelność zespołu zaworu zamykającego. Zbadano wpływ różnych procesów technologicznych i trybów obróbki cieplnej sprężyn tarczowych na ich właściwości elastyczne. Zaproponowano praktyczne zalecenia w celu poprawy procesu technologicznego obróbki cieplnej sprężyn Belleville. Określono cele dalszych badań i sposób wdrożenia uzyskanych wyników. Przeprowadzono prace badawcze w celu poprawy technologii hartowania części zespołu zamykającego (zasuwy i gniazda) zasuw klinowych. Sprawdzono możliwość zastosowania przyspieszonego azotonawęglania w środowisku trietanoloaminy z indukcyjnym ogrzewaniem prądem o wysokiej częstotliwości w zakresie temperatury 950°C w procesie borowania i borochromowania. Wykonano próbki ze standardowych gatunków stali 40, 40Kh i 38Kh2MYuA, które poddano hartowaniu przy rozważanych metodach, przeprowadzono badanie twardości, głębokości i mikrostruktury warstwy hartowanej. Badania w tym kierunku powinny być kontynuowane w celu zbadania charakterystyk tribologicznych (współczynnika tarcia i odporności na zużycie) hartowanych części. Przeanalizowano każdą fazę technologii produkcji sprężyny i zidentyfikowano odchylenia, które mają znaczący wpływ na działanie sprężyny i uszczelnienie zespołu zaworu zamykającego.

3

Laser welding of hot stamping blanks

Wróbel Ireneusz, Danielczyk Piotr

Mechanik

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2023

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R. 96, nr 4

37--41

EN

The article presents technological tests of laser welding of flat blanks of the same thickness, made of two types of hot-stamping steel. Special equipment for welding blanks was shown. Tests of laser welding of 2 mm thick blanks of two types of Usibor 1500 and Usibor 2000 steel with different parameters were carried out. Smooth tensile specimen were cut out of the welded blanks. The obtained microstructure and hardness tests were performed. The research results were discussed.

PL

W artykule opisano próby technologiczne laserowego spawania płaskich formatek o tej samej grubości, wykonanych z dwóch rodzajów stali do tłoczenia na gorąco. Pokazano oprzyrządowanie do spawania formatek. Przeprowadzono testy laserowego spawania formatek o grubości 2 mm z dwóch rodzajów stali - Usibor 1500 i Usibor 2000, przy różnych parametrach procesu. Z zespawanych formatek wycięto próbki wiosełkowe do badań wytrzymałościowych. Wykonano badania uzyskanej mikrostruktury oraz twardości. Omówiono wyniki badań.

4

Case hardening development review (2001-2020)

Wołowiec-Korecka E.

Archives of Materials Science and Engineering

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2023

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Vol. 120, nr 2

70--85

EN

Purpose: The purpose of the work is a complex review of methods applied industrially as case hardening. The paper contains an overview of scientific and development works on surface case hardening methods, especially carburising and quenching, described in the literature from 2001-2020. Design/methodology/approach: State-of-the-art was reviewed by a critical review of the world literature published in 2001-2022, including theoretical work, scientific research, and industry reports. An additional examination of the state of the art was conducted in terms of patent works. Findings: The period of 2001-2020 was a time of intensive work on the modernisation of case hardening techniques to improve the repeatability and uniformity of the produced layers and minimise deformations after hardening. Developing computing technologies have played a large part in this progress. New technologies have also been developed. Research limitations/implications: The review of papers and patent databases was limited to databases providing English-language content options. Practical implications: Case hardening is a crucial stage of steel heat treatment in almost every industrial branch: mechanical, tool, automotive, railway, and aviation. Originality/value: A synthetic review of case hardening methods was presented, particularly carburizing and quenching methods; it also analysed the possibilities and directions of their development.

5

The regeneration of the tools to cellulose cutting using electric arc surfacing method

Romaniuk Svitlana, Barlak Marek, Wilkowski Jacek

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2023

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No. 122

57--66

EN

The regeneration of the tools to cellulose cutting using electric arc surfacing method. The paper presents the laboratory results of the regeneration of the tools to cellulose cutting, using electric arc surfacing method. Three types of regenerating material was used in the rod electrodes form. Additionally, each material was applied with additional non-magnetic powder in the coating. Finally, the layer with the highest microhardness was covered with a ZrN coating in the Arc PVD process. The relative wear coefficient, the friction moment, the friction coefficient, the width of friction track and the microhardness were measured. The SEM observations and EDS investigations were applied for the studies of the microstructure of investigated materials. The best results were obtained for the regeneration using regenerating material, marked as “T-590 + powder”, with ZrN coating.

PL

Regeneracja narzędzi do cięcia celulozy metodą napawania łukowego. W pracy przedstawiono laboratoryjne wyniki regeneracji narzędzi do cięcia celulozy, regenerowane metodą napawania łukiem elektrycznym. Zastosowano trzy rodzaje materiałów regenerujących w postaci elektrod prętowych. Dodatkowo, do materiałów regenerujących dodawano niemagnetyczny proszek w postaci otuliny. Warstwę o największej mikrotwardości pokryto jeszcze powłoką ZrN, w procesie Arc PVD. Zmierzono względny współczynnik zużycia, moment tarcia, współczynnik tarcia, szerokość toru tarcia oraz mikrotwardość. Do badań mikrostruktury badanych materiałów wykorzystano obserwacje SEM oraz badania EDS. Najlepsze wyniki uzyskano dla regeneracji przy użyciu materiału regenerującego oznaczonego jako „T-590 + proszek” z powłoką ZrN.

6

Specifics of physico-mechanical characteristics of thermally-hardened rebar

Kopiika Nadiia, Selejdak Jacek, Blikharskyy Yaroslav

Production Engineering Archives

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2022

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Vol. 28, Iss. 1

73--81

EN

Thermal hardening is widely used nowadays for modification of steel bar properties and obtaining effective reinforcing material. Strength and deformation characteristics of thermally hardened reinforcement is the complex indicator of reinforcement efficiency. Therefore, reliable assessment of physico-mechanical characteristics of thermally hardened rebar is topical and important issue. This article is intended to the analysis of physico-mechanical characteristics of thermally hardened rebar on the basis of experimental data. Thorough statistical processing of experimental data was made and specific features of strength parameters were identified. Analytical model of strength characteristics is proposed, which enables to take into account inhomogeneous strength properties of the rebar along its cross-section. It could be stated that assessment of physico-mechanical characteristics of thermally hardened rebar is topical and important issue, which is the prospective area of further research.

7

Electron beam surface hardening of steel C45

Śliwiński Piotr, Kubik Kamil, Kopyściański Mateusz

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2022

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Vol. 66, No. 6

27--35

EN

Surface hardening makes it possible to obtain high wear resistance of components exposed to friction without the need for hardening the entire element, thereby reducing stresses and deformations as well as process costs. The electron beam, due to its ease of dynamic deflection and focusing as well as very high heating rates, makes it possible to obtain surface layers of required properties. The article presents results of metallographic tests and Vickers hardness tests of electron beam hardened shafts made of steel grade C45. The hardening process resulted in the obtainment of layers having thickness not exceeding 400 μm and hardness not exceeding 900 HV0.1.

8

Electron beam surface hardening

Śliwiński Piotr, Węglowski Marek St., Kwieciński Krzysztof, Wieczorek Andrzej

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2022

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Vol. 66, No. 1

7--20

EN

The surface hardening of steel components makes it possible to achieve high abrasive wear resistance without the necessity of hardening the entire cross-section of a given element. As a result, it is possible to apply lower stress and reduce the cost of the process. Because of very high heating rates (of up to 10^9 K/s) as well as the ease of dynamic deflection and focusing, the use of electron beam to harden component surfaces enables the obtainment of surface layers characterised by required properties. This article constitutes an overview of publications concerning electron beam-based surface hardening.

PL

Hartowanie powierzchniowe elementów stalowych umożliwia uzyskanie wysokiej odporności na zużycie w warunkach tarcia elementów, bez konieczności hartowania całego ich przekroju, wprowadzając mniej naprężeń oraz obniżając koszty procesu. Ze względu na bardzo wysokie prędkości nagrzewania, sięgające 109 K/s, a także łatwość dynamicznego odchylania i ogniskowania, zastosowanie wiązki elektronów do hartowania powierzchni elementów umożliwia uzyskanie warstw wierzchnich o wymaganych własnościach. W artykule przedstawiono przegląd prac dotyczących zagadnienia hartowania powierzchniowego wiązką elektronów.

9

The Effect of Zirconium as an Alloying Additive on the Microstructure and Properties of AlSi9Mg Alloy Cast in Sand Moulds

Kamińska Jadwiga, Angrecki Michał, Dudek P.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 4

5--13

EN

The aim of the study was to select the optimal content of zirconium introduced as an alloying additive to obtain the best strength properties of Al-Si alloy. A technically important disadvantage is the tendency of silumins to form a coarse-grained structure that adversely affects the mechanical properties of castings. To improve the structure, modification processes and alloying additives are used, both of which can effectively refine the structure and thus increase the mechanical properties. According to the Hall-Petch relationship, the finer is the structure, the higher are the mechanical properties of the alloy. The proposed addition of zirconium as an alloying element has a beneficial effect on the structure and properties of silumins, inhibiting the grain growth. The starting material was an aluminium-silicon casting alloy designated as EN AC-AlSi9Mg (AK9). Zirconium (Zr) was added to the alloy in an amount of 0.1%, 0.2%, 0.3%, 0.4% and 0.5% by weight. From the modified alloy, after verification of the chemical composition, samples were cast into sand moulds based on a phenolic resin. The first step in the research was testing the casting properties of alloys with the addition of Zr (castability, density, porosity). In the next step, the effect of zirconium addition on the structure and mechanical properties of castings was determined.

10

Mechanical performance of ultra-high-performance strain-hardening cementitious composites according to binder composition and curing conditions

Kim Min-Jae, Oh Taekgeun, Yoo Doo-Yeol

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e63, 1--12.

EN

This study investigated the mechanical properties and microstructures of three ultra-high-performance strain-hardening cementitious composites (UHP-SHCCs) with different mix proportions and curing conditions. The binders comprised ordinary Portland cement (OPC), silica fume, and ground granulated blast furnace slag (GGBS); the specimens were cured under air and wet curing conditions for 28 and 91 days, respectively. Compressive and direct tensile tests were performed, along with subsequent microstructural analyses using the particle packing theory and scanning electron microscopy, on the composite matrix and reinforcing polyethylene (PE) fibers. The test results indicate that the inclusion of GGBS, more than 50% (by weight of OPC), leads to a decrease in compressive and tensile strength by up to 35.7% but an increase in ductility by up to 55.9%. In addition, a higher content of GGBS resulted in larger deviations based on the curing conditions. The wet curing condition was more effective for the development of a higher energy absorption capacity than the air curing condition at a curing age of 28 d. By contrast, 91 d of wet curing resulted in the lowest strain energy in this study, mainly because of the considerably reduced strain capacity.

11

Rozwój mechanicznego utwardzania nawierzchni drogowych z tłucznia

Skowron Marek

Drogownictwo

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2021

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nr 3

89--92, III okł.

PL

W artykule przedstawiono rozwój mechanicznego utwardzania nawierzchni drogowych z tłucznia w niektórych krajach europejskich w XIX w. Opisano wybrane rodzaje walców drogowych z napędem konnym i parowym. Podano również główne szczegóły ich konstrukcji oraz ich wady i zalety.

EN

This paper presents the development of mechanical drystone road paving in some European countries in the 19th century. Selected types of horse and steam powered road rollers are described. The main details of their design and their advantages and disadvantages are also given.

12

Początki mechanicznego utwardzania nawierzchni drogowych na ziemiach polskich

Skowron Marek

Drogownictwo

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2021

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nr 7-8

226--230

PL

W artykule przedstawione zostały początki mechanicznego utwardzania nawierzchni drogowych na ziemiach polskich. Podano szczegóły konstrukcji powszechnie używanego walca konnego systemu Majewskiego. Opisano także pierwsze próby zastosowania walców parowych.

EN

This paper presents the development of mechanical hardening of road pavement in Poland. Selected types of horse and steam powered road rollers are described. Details of the construction of the commonly used Majewski system horse roller are given. The first attempts to use steam rollers were also described.

13

Effect of the Precipitation Hardening on the Structure of AlSi7Mg0.3Cu0.5 Alloy with Addition of Zr and Combination of Zr and Ti

Kuriš M., Bolibruchova D., Matejka M., Kantorikova E.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 1

95--100

EN

The article focused primarily on comparing the achieved mechanical results for AlSi7Mg0.3Cu0.5Zr and AlSi7Mg0.3Cu0.5Zr0.15Ti experimental alloys. Experimental variants with the addition of Zr ≥ 0.05 wt. % demonstrated the ability of Zr to precipitate in the form of Al3Zr or AlSiZr intermetallic phases. Zr precipitated in the form of long smooth needles with split ends. When evaluating the thermal analyses, the repeated peak was observed already with the initial addition of Zr in the range of approximately 630°C. It was interesting to observe the increased interaction with other intermetallic phases. EDX analysis confirmed that the individual phases are based on Cu, Mg but also Fe. Similar phenomena were observed in experimental alloys with a constant addition of Zr and a gradual increase in Ti by 0.1 wt. %. A significant change occurred in the amount of precipitated Zr phases. A more significant increase in mechanical properties after heat treatment of AlSi7Mg0.3Cu0.5Zr experimental alloys was observed mainly above the Zr content ≥ 0.15 wt. % Zr. The improvement of yield and tensile strength over the AlSi7Mg0.3Cu0.5 reference alloy after heat treatment was minimal, not exceeding 1 %. A more significant improvement after heat treatment occurred in modulus of elongation with an increase by 6 %, and in hardness with an increase by 7 %. The most significant drop occurred in ductility where a decrease by 31 % was observed compared to the reference alloy. AlSi7Mg0.3Cu0.5Zr0.15Ti experimental alloys, characterized by varying Ti content, achieved a more significant improvement. The improvement in tensile strength over the AlSi7Mg0.3Cu0.5 reference alloy after heat treatment was minimal, not exceeding 1 %. A more significant improvement after heat treatment occurred in modulus of elongation with an increase by 12 %, in hardness with an increase by 12 % and the most significant improvement occurred in yield strength with a value of 18 %. The most significant decrease also occurred in ductility where, compared to the reference alloy, the ductility drop was by up to 67 %.

14

Chemical activation effect on the mechanical response of mortars based on dune sand

Ladjel Djelloul, Zairi Moncef, Belagraa Larbi

Mining Science

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2020

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Vol. 27

61--71

EN

The main qualities sought for a mortar are usually; the high compactness, good sealing or impermeability, better mechanical strength and long-term durability. The different methods of accelerating setting and hardening of the mortar as well as the desired characteristics are of great importance with regard to the use of mortars and their different applications in civil engineering. This work is a contribution to improving the properties of mortars at fresh and hardened state by different activation techniques in particular chemical alkaline activators method. The properties of chemically activated mortars using alkaline solutions (KOH and NaOH) at dosages of 0, 2 and 4% was investigated in this experimental program using a based cement matrix with dune sand and blended cement type CEM II/ B grade 42. The results obtained showed the beneficial effect of the chemical activation modes mainly, an improvement of the mechanical response (compressive strength) at young age and in the long term.

15

Forming the surface layer properties during grinding

Deja Mariusz, Stanisławska Alicja, Szkodo Marek, Wszelak Karolina

Mechanik

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2019

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R. 92, nr 10

661--663

EN

The article describes the grinding of flat surfaces combined with changes in the properties of the surface layer, in particular through its hardening. Issues related to the grindhardening technology are discussed. In addition, tests have been presented in which improved grinding properties of the workpiece through plastic deformation have been obtained after the grinding process.

PL

W artykule scharakteryzowano szlifowanie powierzchni płaskich połączone ze zmianami właściwości warstwy wierzchniej, zwłaszcza poprzez jej zahartowanie. Omówiono problemy związane z tzw. technologią grind-hardening. Dodatkowo przedstawiono badania, w których po procesie szlifowania uzyskano lepsze właściwości elementu obrabianego wskutek odkształcenia plastycznego

16

Measurements and numerical simulations of laser hardening and remelting thermal cycles

Kik T., Wyględacz B.

Journal of Achievements in Materials and Manufacturing Engineering

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2019

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Vol. 96, nr 2

69--82

EN

Purpose: of these researches was to investigate the influence of thermal cycles recording conditions and comparing them with the calculated by FEM. This approach allows proposing a new way of determining the technological conditions of the process, based on numerical analyses. Design/methodology/approach: Thermal cycles of high power diode laser hardening and remelting was recorded and calculated by FEM. Results of metallographic examinations were compared with numerical simulations results, as well as the thermographic pictures. Acquisition errors during the thermal cycles were also defined. Findings: Due to the fact that the it was used FEM, comparison of the numerical analyses with real test results was performed for laser hardening and remelting process. Research limitations/implications: For complete information it is needed to collect bigger database of the results and prepare also hardness calculation model for WCL steel. Practical implications: The result of the presented work is to signal a methodology that allows obtaining information on the impact of the parameters of the laser hardening and remelting process on the properties of the treated samples. Not without significance is the fact that the use of FEM eliminates in this case a lot of errors that in real tests can distort the result. Originality/value: The researches were provided for high power diode laser hardening and remelting. The influence of heat input on layers properties and theirs structure was defined. Results were compared with thermographic pictures and calculated cases.

17

Badania kalorymetryczne oraz modelowanie numeryczne wpływu wybranych domieszek chemicznych na szybkość hydratacji cementu twardniejącego w różnych temperaturach

Kiernożycki Włodzimierz, Błyszko Jarosław

Cement Wapno Beton

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2019

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R. 24/86, nr 6

432--447

PL

W pracy przedstawiono wyniki badań kalorymetrycznych, w różnych temperaturach, cementu portlandzkiego oraz hutniczego z domieszką superplastyfikatora PCE i z domieszką ograniczającą skurcz, złożoną z mieszaniny wodorotlenków. Stwierdzono, że domieszki te tylko nieznacznie zmniejszają aktywność hydrauliczną badanych spoiw oraz ciepło hydratacji, w wyższych temperaturach twardnienia. Wykazano, że domieszka superplastyfikatora PCE nie tylko przedłuża okres indukcji w początkowym okresie hydratacji cementów, ale również spowalnia ten proces w okresie twardnienia. Wyraża się to przesunięciem w czasie i zmniejszeniem mocy źródła ciepła twardniejącego cementu, co ogranicza ryzyko uszkodzenia konstrukcji masywnych, w okresie ich wznoszenia. Dokonując transformacji, wybranych wyników badań zaczynów w temperaturze odniesienia 20°C na inne warunki cieplne, przedstawiono koncepcję ich uogólnienia w adiabatycznych warunkach twardnienia konstrukcji masywnych.

EN

The paper presents results of calorimetric measurements at different temperature of Portland and Slag Cement with the addition of PCE superplasticizer and shrinkage reducing admixture, composed of hydroxide mixture. The addition of these admixtures insignificantly reduces the heat and rate of the hydration, at higher temperature. The addition of the plasticizer delays the process of cement hydration at early stage, also influencing its rate later on. The phenomena can be observed as a delay in the process initiation and total value of the heat flow during the hardening. This admixture can be used to limit the cracking of massive constructions, during their execution. By analyzing the results of chosen cement pastes at the reference temperature of 20°C, the authors were able to propose a general method of assessing the quasi-adiabatic conditions during hardening of massive concrete structures.

18

Badania fibrokompozytu cementowego z dużym udziałem przemysłowych produktów ubocznych, twardniejącego w warunkach naprężeń pokrytycznych

Jašek Marek, Stejskalová Kateřina, Hurta Jan, Brožovský Jiří

Cement Wapno Beton

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2019

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R. 24/86, nr 6

471--480

PL

W pracy opisano badania doświadczalne właściwości różnych wariantów kompozytów cementowych z dużym dodatkiem przemysłowych produktów ubocznych, zbrojonych włóknami i twardniejących w warunkach naprężeń pokrytycznych. Produkty uboczne, otrzymane głównie na Morawach w Regionie Śląskim Republiki Czeskiej zastosowano do otrzymywania zbrojonych włóknami kompozytów cementowych twardniejących w warunkach naprężeń pokrytycznych. Zbadano ich podstawowe właściwości fizyczne – gęstość świeżego i stwardniałego kompozytu, konsystencję, wytrzymałość na zginanie i ściskanie i moduł elastyczny. Badania wykazały, że kompozyty cementowe zbrojone włóknami i zawierające przemysłowe produkty uboczne mogą być stosowane w budownictwie.

EN

This work aims at experimental investigation of several variants of fiber reinforced cementitious composite with strain hardening made partially with industrial by-products. This paper describes the manufacturing, testing and evaluating the properties of the composite. Industrial waste produced mainly in Moravia-Silesia Region in the Czech Republic was used for the manufacturing of the fiber reinforced cementitious composite with strain hardening. The basic physical and mechanical properties were measured – volume density of wet and hardened composite, consistency, tensile, flexural and compressive strength and elastic modulus. The findings show that the fiber reinforced cementitious composite made partially with industrial by-products is a suitable material for sustainable constructions.

19

Numerical Analysis of Thermo-Mechanical Phenomena of the Progressive Hardening Elements Made of Tool Steel for Cold Work

Domański T.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 1

329--338

EN

The numerical algorithm of thermal phenomena is based on the solution of the heat conduction equations in Petrov-Galerkin’s formula using the finite element method. In the modeling of phase transformation in the solid state, the models based on the diagrams of continuous heating and continuous cooling (CHT and CCT). In the modeling of mechanical phenomena, equations of equilibrium and constitutive relationships were adopted in the rate form. It was assumed that the hardened material is elastic-plastic, and the plasticizing can be characterized by isotropic, kinematic or mixed strengthening. In the model of mechanical phenomena besides thermal, plastic and structural strains, the transformations plasticity was taken into account. Thermo-physical size occurring in the constitutive relationship, such as Young’s modulus and tangential modulus, while yield point depend on temperature and phase composition of the material. The modified Leblond model was used to determine transformation plasticity. This model was supplemented by an algorithm of modified plane strain state, advantageous in application to the modeling of mechanical phenomena in slender objects. The problem of thermoelasticity and plasticity was solved by the FEM. In order to evaluate the quality and usefulness of the presented numerical models, numerical analysis of temperature fields, phase fractions, stresses and strains was performed, i.e. the basic phenomena accompanying surface layer of progressive-hardening with a movable heat source of slender elements made of tool steel for cold work.

20

Influence of flame heating parameters on the hardness of hardened C45 steel

Dargacz M., Starosta R.

Journal of KONES

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2018

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Vol. 25, No. 1

41--47

EN

In this article, the impact of selected parameters of heating using a gas torch on the hardness of hardened alloy steels C45 was presented. The staff of the ship's engine room sometimes uses flame hardening during casual repairs of the machines weared as a result of operational extortions. The purpose of emergency repairs is to restore the possibility of work of ship machinery and equipment for the duration of the vessel's journey. An acetylene-oxygen torch was used to heat the steel. As the analysed parameters of the technological process, the heating time and the distance between the nozzle and the workpiece were selected. The values of the mentioned parameters have been selected so that the temperature of hardened steel is in the range from 800 to 1250 oC. The following values of the adopted machining parameters were used: the heating time was 60, 85 and 110 seconds, while the distance of the torch nozzle was 10, 20 and 30 mm. After heating, the samples were cooled by immersing in water. The research was based on a randomized orthogonal experiment plan. The purpose of the quantitative assessment of the influence of heating parameters on the hardness of hardened C45 steel, done statistical analysis variance analysis, multiple regression and mathematical optimization by the Tagichi method. Conducted tests and statistical analysis showed a significant effect of selected parameters of flame heating on the hardness of hardened C45 steel. The greatest influence on the hardness of the steel is the distance between the nozzle and the workpiece. The highest value of hardness was obtained using the following parameters of flame hardening: nozzle distance 30 mm, heating time 60 seconds.