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1

Comparison of the influence of austenitization and quenching conditions on the microstructure of HSLA 38MnVS6 steel

Illichmanová Edita, Tillová Eva, Uhríčik Milan, Belan Juraj, Šnircová Melisa

System Safety : Human - Technical Facility - Environment

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2025

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Vol. 7, iss. 1

364--374

EN

The study investigates the effect of various heat treatment conditions on HSLA steel 38MnVS6, aiming to expand its potential applications in the automotive industry. The study focuses on optimizing the parameters of austenitizing, quenching, and low-temperature tempering. The objective was to achieve a predominantly martensitic microstructure and ensure a minimum hardness of 50 HRC throughout the cross-section of the material. Three heat treatment regimes were applied to the samples at an austenitizing temperature of 870°C. In the first two regimes, quenching was performed in oil at 120°C and 70°C, while in the third regime, a different quenching oil was used at the same temperature of 70°C. For each sample, surface and core hardness were measured using the Rockwell method, followed by detailed microstructural analysis. The results showed that increasing the carbon potential in the furnace reduced the ferrite fraction at the surface and positively affected surface hardness. A key finding was that the use of low-viscosity quenching oil enables the achievement of the critical cooling rate required for the desired hardness. Moreover, lowering the oil temperature effectively suppressed the formation of undesirable fine lamellar pearlite (troostite). The results indicate the potential of the experimental material for applications subjected to high dynamic loading. Therefore, further research should include fatigue strength and tribological testing to further validate the material performance.

2

Wpływ hartowania elektronowego na własności tribologiczne stali w różnych stanach dostawy

Śliwiński Piotr, Węglowski Marek, Wieczorek Andrzej, Nuckowski Paweł, Skołek Emilia, Marciniak Szymon

Materials Science and Welding Technologies / Technologie Materiałowe i Spawalnicze

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2025

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Vol. 69, No. 2

29--38

PL

Stale nanobainityczne wykazują bardzo korzystne połączenie właściwości mechanicznych, takich jak wytrzymałość, plastyczność oraz odporność na zużycie. Ze względu na swoje własności znajdują zastosowanie w produkcji odpowiedzialnych elementów maszyn, takich jak wały czy przekładnie zębate. Jednak w niektórych przypadkach, aby osiągnąć pożądane rezultaty, może być konieczne zwiększenie twardości warstwy powierzchniowej. W przedstawionym badaniu prostopadłościenne elementy ze stali nanobainitycznej hartowano wiązką elektronów. Uzyskane próbki zostały następnie poddane analizie mikrostruktury za pomocą mikroskopii świetlnej, a także analizie XRD, pomiarom twardości Vickersa i testom tribologicznym typu Ball-On-Disc. Wyniki analiz ujawniły znaczące zmiany mikrostruktury i wynikający z nich wzrost twardości i odporności na zużycie tribologiczne.

EN

Nanobainitic steels exhibit a highly favourable combination of mechanical properties such as strength, ductility and wear resistance. Owing to these properties, the steels are used in the production of critical machine components such as sha³ s and gear transmissions. However, in some cases, it may be necessary to increase the surface layer hardness to achieve the desired performance. In the study discussed in the article, cuboidal elements made of nanobainitic steel were subjected to electron-beam hardening. Aferwards, the specimens were analysed in terms of microstructure using optical microscopy as well as XRD analysis, Vickers hardness testing and ball-on-disc tribological testing. The results obtained from these analyses revealed significant microstructural transformations, leading to an increase in both hardness and tribological wear resistance.

3

Thermodynamic Analysis and Impact of Quenching on Microstructure & Mechanical Properties of High Silicon Ductile Iron

David Joseph B., Pustal B., Weirich T., Bührig-Polaczek A.

Archives of Foundry Engineering

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2025

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Vol. 25, iss. 1

43--51

EN

Solid-solution-strengthened ferritic ductile iron (SSFDI) exhibits superior tensile strength to elongation ratios up to a critical silicon content of 4.3 wt.%. Beyond this threshold, this material experiences a sudden drop in ultimate tensile strength and elongation at breakage. Previous studies indicate that this is may be because of the formation of superstructures like B2 and D03 especially at regions with high silicon content. This study aims to comprehend thermodynamics behind phase transition during solid-state transformation in high silicon ductile iron. Using thermodynamic simulations, this current investigation tries to pinpoint the transition temperature from the ferritic phase to superstructure formation especially B2 superstructure. Additionally, analysis is made to see consequences of quenching above this transition temperature on microstructure, and mechanical properties. The results contribute insights into phase transitions in high silicon ductile iron, offering practical guidance for optimizing heat treatment processes. By isolating the transition temperature and evaluating the impact of quenching, we provide actionable strategies for controlling microstructural evolution and enhancing mechanical performance in SSFDI. In conclusion, this research represents a crucial advancement in realizing the full potential of high silicon ductile iron for engineering applications. The findings deepen our understanding of the material's behavior and furnish practical approaches for improving its mechanical properties through controlled heat treatments and quenching processes.

4

Achieving high tensile properties and impact toughness in ultrahigh strength lean alloy steel by quenching and partitioning treatment

Wang Lirong, Liang Yilong, Zhao Fei, Xu Fahong, Lei Lei, Long Shaolei, Yang Ming, Jiang Yun

Archives of Civil and Mechanical Engineering

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2024

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Vol. 24, no. 1

art. no. e32, 2024

EN

In this study, a desirable combination of strength, ductility, and toughness in low-carbon 30CrMnSiA steel is achieved by a hierarchical multiphase microstructural architecture subjected to one- and two-step quenching and partitioning (Q&P) processes. The microstructural constituents are studied by EBSD, x-ray diffraction, dilatometry, and TEM. Experimental results show that microstructural refinement occurs in the martensite and bainite at a lower quenching temperature, where more Bain groups form in one close-packed plane group. This causes random distribution between martensite and bainite blocks, enlarging the volume of high-angle grain boundaries. Such refined microstructure, particularly for the increased martensite with higher-density dislocations, causes an increased strength at a decreased quenching temperature. By comparison, increased quenching and partitioning temperature produces more stable film-like retained austenite (RA) and a low dislocation density in martensite/bainite (M/B); thus, it provides better deformation by accommodating with M/B laths and absorbing substantial energy due to the transformation-induced plasticity effect. The lower dislocation density, the higher volume fraction of RA, and the higher HAGBs improve the impact toughness and tensile properties of lean alloy steel through a moderate Q&P process.

5

Wykrywanie pęknięć hartowniczych w stali łożyskowej 100Cr6 metodą prądów wirowych

Kondej Adam, Jończyk Sylwester, Lasota Piotr

Welding Technology Review

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2023

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R. 95

87--93

PL

W artykule opisano wyniki badań w zakresie identyfikacji i lokalizacji pęknięć hartowniczych w stali łożyskowej 100Cr6 z wykorzystaniem autorskiego urządzenia kontrolno-pomiarowego do badań nieniszczących metodą prądów wirowych Wirotest M2 oraz automatycznego stanowiska AutoWir-S1. Do badań zastosowano głowicę stykową o częstotliwości 861 kHz. System rejestrował zmiany amplitudy napięcia oraz częstotliwości rezonansowej. Wyraźny spadek wartości obydwu parametrów wskazywał na obecność nieciągłości. Efekt krawędziowy powodował wzrost amplitudy napięcia oraz spadek częstotliwości, jednakże zmiany te nie wpłynęły na detekcję pęknięć. Najmniejsze wykryte pęknięcie charakteryzowało się maksymalną szerokością około 20 μm i było niewidoczne okiem nieuzbrojonym. Uzyskane wykresy powierzchniowe jednoznacznie obrazują przebieg oraz lokalizację poszczególnych nieciągłości.

EN

The article describes the results of research on the identification and localization of quenching cracks in 100Cr6 bearing steel using a proprietary non-destructive testing device based on the eddy current method called Wirotest M2 and an automatic stand AutoWir-S1. A surface probe with a frequency of 861 kHz was used for the tests. The system recorded changes in voltage amplitude and resonant frequency. A significant decrease in both parameters indicated the presence of discontinuities. The edge effect caused an increase in voltage amplitude and a decrease in frequency, but these changes did not affect crack detection. The smallest detected crack had a maximum width of about 20 μm and was invisible by the unaided eye. The obtained surface charts clearly illustrate the course and localization of individual discontinuities.

6

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.

7

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.

8

Impact of single-piece flow thermo-chemical treatment process conditions on hole quenching deformation

Stachurski Wojciech, Sawicki J., Zgórniak P., Wołowiec-Korecka E.

Archives of Materials Science and Engineering

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2023

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Vol. 121, nr 1

18--24

EN

Purpose: Pulsed low-pressure carburizing (LPC) and omnidirectional high-pressure gas quenching (HPGQ) are innovative methods for quenching the surface layer. The thermo-chemical treatment carried out by this method reduces quenching geometric deformations, with detailed numerical values not available in the literature due to the short existence of this method. Design/methodology/approach: Sixteen toothed elements of EN 20MnCr5 steel were subjected to pulsed low-pressure carburising with omnidirectional jet quenching in 4 groups, varying the process temperature (920°C, 960°C) and in two groups performing a tempering treatment. The elements were tested before machining by measuring their internal hole diameters, radial runout, roundness and cylindricity. These values were tested again after treatment. The direction of change and the statistical significance of the effect of treatment and its parameters, temperature and tempering were analysed. Findings: Thermo-chemical treatment significantly affects geometric changes in diameters, roundness, cylindricity and radial runout compared to elements without heat treatment due to physical transformations occurring during this treatment (p<0.05). Changing the process temperature in the value range of 920°C-960°C affects the hole diameter (makes it smaller) (p<0.05), but does not affect radial runout, cylindricity and roundness. The observed dimensional changes in diameters have numerically small values (<0.005 mm). The tempering treatment can affect the values of average diameters. Its effect on roundness, cylindricity and radial runout was not observed. Research limitations/implications: In the temperature range studied, the method of pulsed low-pressure carburising + omnidirectional high-pressure gas quenching makes it possible to raise the temperature of the process and shorten its duration without significant geometric changes in the treated elements. Practical implications: The method of pulsed low-pressure carburising and omnidirectional high-pressure gas quenching (HPGQ) ensures the maintenance of reproducible quenching deformations at a level significantly lower than conventional processing methods. Originality/value: The method of pulsed low-pressure carburising together with omnidirectional high-pressure gas quenching (HPGQ) is a method that has been used briefly in the industry, and there are few reports on it to date.

9

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.

10

Electron beam welding beam current on microstructure and mechanical properties of AISI 316 austenitic stainless steel

Li Huaying, Huang Fang, Li Jiacai, Li Juan, Zhao Guang-hui, Chang Yuan

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 4

art. e259, 1--19

EN

Welding experiments were carried out on AISI 316 austenitic stainless steel by vacuum electron beam welding (VEBW) machine at different welding beam currents (IW = 70 mA, 80 mA, 90 mA and 100 mA). Different vacuum electron beam welding beam current on AISI 316 austenitic stainless steel microstructure and mechanical properties were analyzed by optical microscopy (OM), electron backscatter diffraction (EBSD) and mechanical stretching machines, combined with digital image correlation (DIC) stretching. The results show that the elongation and tensile strength of AISI 316 austenitic stainless steel increases and then decreases with the increase of IW. The base material (BM) consists of fine austenite grains, while the weld material (WM) is characterized by fine equiaxed austenite grains scattered between elongated columnar austenite grains. No coarse austenite grains are observed in the heat affected zone (HAZ). The proper distribution of narrower HAZ and WM elongated columnar crystals ensures high yield strength (278 MPa), tensile strength (589 MPa) and good plasticity (88% total elongation) of the welded joints. The welded specimens are in ductile fracture mode and the fracture consists of various tough nests in different regions. The increase in elongation is attributed to the weakening of the thin lamellar grain structure and Cube texture {001} < 100 > formed by VEBW, which enhances the deformation coordination of dislocation slippage.

11

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.

12

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.

13

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.

14

Initial Analysis of the Surface Layer of AVGI Cast Iron Subject to Abrasion

Jakubus Aneta

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 2

50--56

EN

The article presents the results of research on the abrasion resistance of cast iron with vermicular graphite in the as-cast state and after austempering (the latter material is referred to as AVGI – Austempered Vermicular Graphite Iron). Austenitization was carried out at the temperature values of either 900°C or 960°C, and austempering at the temperature values of either 290°C and or 390°C. Both the austenitization and the austempering time was equal to 90 minutes. The change of the pearlitic-ferritic matrix to the ausferritic one resulted in an increase in mechanical properties. Abrasion tests were conducted by means of the T-01M pin-on-disc tribometer. The counter-sample (i.e. the disc) was made of the JT6500 friction material. Each sample was subject to abrasion over a sliding distance of 4000 m. The weight losses of both samples and counter-samples were determined by the gravimetric method. It was found that the vermicular cast iron austenitized at 900°C and austempered at 290°C was characterized by the lowest wear among the evaluated cast iron types. The geometric structure of the surface layer after the dry friction test exhibited irregular noticeable grooves, distinct oriented abrasion traces, plastic flow of the material, microcracks, and pits generated by tearing out the abraded material. The largest surface roughness was found for the AVGI cast iron heat-treated according to the variant 3 (Tγ =900 ºC; Tpi = 390°C), while the smallest one occurred in AVGI cast iron subject to either the variant 2 (Tγ =960 ºC; Tpi = 290°C) or the variant 4 (Tγ =900 ºC; Tpi = 290°C) of heat treatment and was equal to either 2.5 μm or 2.66 μm, respectively. It can be seen that the surface roughness decreases with the decrease in the austempering temperature.

15

Initial Assessment of Graphite Precipitates in Vermicular Cast Iron in the As-Cast State and after Thermal Treatments

Soiński M. S., Jakubus Aneta, Borowiecki B., Mierzwa P.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 4

131--136

EN

The purpose of the work was to determine the morphology of graphite that occurs in vermicular cast iron, both in the as-cast state and after heat treatment including austenitization (held at a temperature of 890°C or 960°C for 90 or 150 min) and isothermal quenching (i.e. austempering, at a temperature of 290°C or 390°C for 90 or 150 min). In this case, the aim here was to investigate whether the heat treatment performed, in addition to the undisputed influence of the cast iron matrix on the formation of austenite and ferrite, also affects the morphology of the vermicular graphite precipitates and to what extent. The investigations were carried out for the specimens cut from test coupons cast in the shape of an inverted U letter (type IIb according to the applicable standard); they were taken from the 25mm thick walls of their test parts. The morphology of graphite precipitates in cast iron was investigated using a Metaplan 2 metallographic microscope and a Quantimet 570 Color image analyzer. The shape factor F was calculated as the quotient of the area of given graphite precipitation and the square of its perimeter. The degree of vermicularization of graphite was determined as the ratio of the sum of the graphite surface and precipitates with F <0.05 to the total area occupied by all the precipitations of the graphite surface. The examinations performed revealed that all the heat-treated samples made of vermicular graphite exhibited the lower degree of vermicularization of the graphite compared to the corresponding samples in the as-cast state (the structure contains a greater fraction of the nodular or nearly nodular precipitates). Heat treatment also caused a reduction in the average size of graphite precipitates, which was about 225μm2 for the as-cast state, and dropped to approximately 170-200 μm2 after the austenitization and austempering processes.

16

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 %.

17

The effect of heat treatment on mechanical properties of 42CrMo4 steel

Çalık A., Dokuzlar O., Uçar N.

Journal of Achievements in Materials and Manufacturing Engineering

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2020

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Vol. 98, nr 1

5--10

EN

Purpose: In this study, the effect of heat treatment on the microstructure and mechanical properties of 42CrMo4 steel were investigated. Design/methodology/approach: The samples were annealed at 860°C for 120 min. followed by oil quenching and then tempered at temperatures between 480 and 570°C for 120 min. The microstructure of untreated 42CrMo4 steel mainly consists of pearlite and ferrite whereas the microstructure was found to be as a martensitic structure with a quenching process. Findings: The results showed that there is an increase in yield stress, ultimate tensile stress, hardness and impact energy, while elongation decreases at the end of the quenching process. Conversely, yield stress, ultimate tensile stress and hardness decrease slightly with the increasing of tempering temperature, while elongation and impact energy increase. Research limitations/implications: Other types of steels can be heat treated in a wider temperature range and the results can be compared. Practical implications: It is a highly effective method for improving the mechanical properties of heat treatment materials. Originality/value: A relationship between the mechanical properties and the microstructure of materials can be developed. The heat treatment is an effective method for this process.

18

Study on PLA/PA11 Bio-Based Toughening Melt-Blown Nonwovens

Zhu Feichao, Yu Bin, Su Juanjuan, Han Jian

Autex Research Journal

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2020

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Vol. 20, no. 1

24--31

EN

With aim to improve the mechanical and thermal properties of poly (lactic acid) (PLA) melt-blown nonwovens (MBs), polyamide 11 (PA11) was melt blended with PLA at the weight proportions of PLA/PA11 (95/5, 90/10, 85/15, 80/20), and the corresponding PLA/PA11 MBs were also manufactured. The crystallization, thermal and rheological behaviors of PLA/PA11 blends were investigated. PLA/PA11 MBs were also characterized by morphology and mechanical properties. The results indicated that PA11, as globular dispersed phases, formed confined crystals and could improve the thermal stability of PLA matrix. The viscosity of PLA/PA11 blends was slightly increased but the rheological behaviors of “shear-thinning” kept unchanged in comparison with PLA. The average diameter of PLA/PA11 MB fibers was slightly increased, whereas the toughness of PLA/PA11 MBs including the strength and elongation were efficiently enhanced compared with those of PLA MBs.

19

The influence of quenching temperature on distortions during the individual quenching method

Wołowiec-Korecka E., Stachurski W., Zgórniak P., Korecki M., Brewka A., Byczkowska P.

Archives of Materials Science and Engineering

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2020

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Vol. 105, nr 2

80--85

EN

Purpose: In this paper, the impact of hardening temperature on the quenching distortions which occur during low-pressure carburizing with gas quenching - using the individual quenching method - was analysed. Design/methodology/approach: The reference elements were subjected to carburizing at 980°C, followed by gas quenching at temperatures of 860°C, 920°C and 980°C. The geometrical measurements of the elements were made before and after the chemical treatment and the size of the quenching distortions of their geometrical parameters was determined. Findings: It was demonstrated that a high temperature of quenching has an unfavourable effect on changes in cylindricity and roundness parameters but, at the same time, reduces the size of distortion of outer parameters. Low temperature quenching reduces quenching distortions of cylindricity and roundness parameters while increasing the distortion of outer dimensions. Research limitations/implications: Based on the research and analysis carried out in this work, it was found that the use of lower quenching temperature is justified in economic and quality terms. Practical implications: In the case of the aviation or automotive industry, very high quality of manufactured elements along with a simultaneous reduction of their production costs is extremely important. Maintaining the dimensions of the elements during heat treatment is extremely difficult. The tests allowed to determine the optimal hardening temperature, which brings with it acceptable deformations. Since it is easier to “repair” the outer geometrical dimensions (diameter, thickness), it seems that quenching from lower temperatures is a more favourable process. Originality/value: The conducted tests allowed to determine the most favourable conditions for hardening elements from the automotive industry, taking into account the occurring deformations and their subsequent processing

20

The analysis of stress distribution in tempered structural glass with stress concentrators under tension and compression

Šaučiuvėnas Gintas, Gečys Tomas, Mudrov Andrej, Ustinovichius Leonas, Miedzialowski Czesław

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

62--77

EN

The paper describes the results obtained from the tensile and compression experimental tests of the structural tempered glass plates with three different types of stress concentrators and without them. The types of stress concentrator have been chosen as close as possible to those usually found in practical situations and also taking into account the cases known from the literature. All tests are performed under the same conditions and with the step of loading 1.0 kN for tension and compression tests up to the limit of 8.0 kN. The stress gradients are measured with an optical device by birefringence. The research is aimed at determining the distribution and the values of stress gradients under tension and compression. The paper considers the problems of determining the stress values and their distribution in the glass plates with various stress concentrators, based on the results of non-destructive measuring, analytical calculations and the numerical simulation.