Wyniki 1-6 spośród 6 dla zapytania: authorDesc:"GRZEGORZ MICHTA"

85 lat Katedry Metaloznawstwa i Metalurgii Proszków 1922-2007

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W artykule opisana została historia Katedry Metaloznawstwa i Metalurgii Proszków od momentu jej powstania w roku 1922, aż do chwili obecnej. Przedstawiono istotne momenty decydujące o losach Katedry oraz krótkie notki biograficzne pracowników, którzy wywarli istotny wpływ na jej profil naukowo badawczy. Zamieszczono także życiorysy naukowe kolejnych kierowników Katedry. Końcowa część artykułu pośw[...]

Microstructure and mechanical properties of ultra-high strength steel Weldox 1300

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For years, metallurgists seek to manufacture structural steel with the highest strength properties while still satisfying low temperature toughness. With the growth of the yield strength it is possible to make the structure of the elements of a smaller wall thickness, and therefore lighter and less expensive to transport. A smaller wall thickness requires less welding consumables and hence the welding process become shorter. The increase in strength properties of steel can be achieved by proper selection of the chemical composition and/or quenching and tempered processes. Such opportunities provide consistently quenched and tempered steels, by the adequately matched the chemical composition and appropriate heat treatment. These steels have very good mechanical properties and good plastic properties with good weldability. The mechanical properties and chemical composition can be found in the standard EN 10025-6 [1]. It should be noted, however, that the steels of yield strength above 1000 MPa are not mentioned in the current standard. This is due to the fact that these steels are a relatively new materials for constructions. An important development has been achieved in ultra-high strength low-alloy steels. The good impact properties is a result of the addition of small amounts of V by causing V4C3 precipitates to form during tempering. The dispersion strengthening by this carbide raises the yield strength while at the same time retards grain growth and improves the impact resistance [2]. The previous investigation have shown that Mo moderately increases the yield strength of martensitic steels, probably due to its large atomic size, whereas the addition of Mn results in a slight decreases in yield strength. Authors [3] reported that the both Mn and Mo increase the stacking fault energy of the austenite matrix, although Mn is generally considered to stabilize the ?Á phase by lowering the stacking fault energy of the austenite. [...]

Characterization of microstructure and mechanical properties of electron beam welded Allvac 718Plus butt welded joint DOI:10.15199/28.2016.6.3

  Allvac 718Plus (718Plus) is a high strength, corrosion resistant commercial polycrystalline nickel-based superalloy developed by ATI ALLVAC over 10 years ago. 718Plus has been designed to fuse the most desired properties of Inconel 718 and Waspaloy, producing advantages of good mechanical properties, higher working temperature than Inconel 718, good fabricability and reasonable cost of production. 718Plus is strengthened by γʹ phase and other precipitates which are located mainly at grains boundaries. Compared to Inconel 718, 718Plus has increased concentration of Al, Ti and Co and decreased amount of Fe. Weldability of 718Plus is comparable to Inconel 718, thus there is a risk of intergranular microcracking in heat affected zone (HAZ). The test joint have been welded autogenously using electron beam at 120 kV accelerating voltage, 10 mA current and 78 cm/min welding speed. The microstructure of casted base material, heat affected zone (HAZ) and weld metal of electron beam welded 718Plus were investigated by means of light (LM) and scanning electron microscopy (SEM). SEM observations of welded joint microstructure were performed using secondary electrons (SEM-SE). SEM/EDS analysis were carried out. Both MC type carbides and Laves phase were observed in interdendritic regions of base material. The microstructure of heat affected zone was composed of γ matrix, γʹ phase and MC-type carbides, Laves phase and Laves/γ eutectic. In weld metal zone no γʹ precipitates were observed. The microhardness measurements have shown a decrease in weld metal and HAZ. It can be caused by an influence of the welding process thermal cycle. Key words: 718Plus, electron beam welding, SEM.1. INTRODUCTION Allvac 718Plus (718Plus) is a relatively recently developed nickelbased superalloy which properties lead to widespread potential of applications. This alloy belongs to a group of nickel-base superalloys strengthened by ordered[...]

Własności mechaniczne stali niskowęglowych z manganem, krzemem i miedzią po izotermicznym wyżarzaniu w zakresie 400÷700 °C

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W pracy przedstawiono wyniki badań własności mechanicznych dla dwu wytopów stali niskowęglowej: zawierającej mangan i krzem (0,2 %C, 1,5 %Mn, 1,5 %Si), oraz mangan, krzem i miedź (0,2 %C, 1,5 %Mn, 1,5 %Si, 1,0% Cu). Badania prowadzono po chłodzeniu z zakresu dwufazowego i przemianie izotermicznej przebiegającej przy temperaturach z zakresu 400÷700 °C. Własności mechaniczne po przemianie perlity[...]

Laser welding of DP steel - characterization of microstructure of steel and welded joint

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Increasing demands on weight reduction, safety and cost have led to a rapid development in car body engineering. A number of new materials are being investigated, especially steels of greater strength. Advanced High Strength Steels (AHSS) are being intensively explored by the automotive industry [1]. The combination of excellent structural properties and good formability makes AHSS such as DP (Dual Phase) steel attractive candidates for light-weight vehicles. Dual Phase steels, so called because they consist essentially of a dispersion of martensite in a ferrite matrix, are produced by intercritically annealing and cooling with rate appropriate to achieve the desired structure [2]. Apart from the chemical composition, the microstructure and mechanical properties from the practical point of view the most important property is weldability of automotive steels [3]. Traditionally, resistance welding and fusion welding have been used in the automotive industry. However, the most prospective welding process in this branch of industry is laser welding. The main advantages of laser welding are small distortions of the sheets caused by a small width of HAZ, high welding speed and flexibility of this process [3]. Kang et al. [4] have shown results of laser welding of DP 600 steel 1.4 mm in thickness. They have performed hardness measurements, microstructure examination, mechanical properties and formability tests. The results have shown that the maximum hardness in the heat affected zone (HAZ) exceeds 350 HV. The maximum hardness was mainly the result of bainite, ferrite and small amounts of martensite phase. In another studies [5], High Strength Low Alloy (HSLA) and DP980 (980 MPa) sheet steels, 1.2 mm in thickness, were welded with a 4 kW diode laser. For the DP steel weld formability was much lower than that of corresponding base metal, due to the formation of soft zones in the outer region of the HAZ of the welds. Results of DP 600 [...]

Optimization of a microstructure and properties of Fe-30Ni alloy by thermomechanical treatment

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The material investigated was the Fe-30Ni alloy in which martensitic transformation was induced by plastic deformation or quenching in liquid nitrogen. The morphology and volume fraction of martensite can be modified by the change of the deformation path, temperature and strain. The pronounced strengthening was observed after deformation induced martensitic transformation, which resulted in [...]

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