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Relationship between microstructure and mechanical properties of strips from microalloyed steel after cold rolling and annealing

Janošec M., Schindler I., Vodárek V., Místecký E., Růžička M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2007

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Vol. 321, z. 89

105-106

EN

A large testing programme of an HSLA strip steel grade S 500 MC was conducted. The experiment was based on combination of cold rolling, recrystallization annealing, mechanical testing and metallographic examinations. Samples of pickled cuts of hot rolled strip of thickness 4 mm were used for simulation by rolling. Chemical composition of the steel grade was as follows: 0.06 C - 1.38 Mn- 0.24 Si - 0.013 P - 0.005 S - 0.022 Al - 0.03 V - 0.02 Ti - 0.07 Nb (wt %). Samples in the form of strips with dimensions 4 x 25 x 340 mm were rolled in several passes with total height reduction 5 to 75 %. Particular partial strains were realized at room temperature in the housingless, hydraulically pre-stressed laboratory mill QUO (a four-high mill with work rolls of diameter 62 mm) [1]. Afterwards the laboratory mill products were annealed in the vacuum furnace with the protective gas atmosphere consisting of N2+H2. The annealed samples underwent the mechanical testing. The gained results yield stress YS, ultimate tensile strength UTS and their ratio, as well as elongation Ago in %, were summarized in graph (see Fig. 1) in dependence on relative height reduction before annealing - 8 [%]. The found out points were plotted in a coordinate system and the corresponding curves were constructed manually. It was confirmed that by a suitable combination of size of previous cold deformation and parameters of the following recrystallization annealing it is possible to influence a complex of mechanical properties of particular strips. Particular trends of strength and plastic properties correspond to each other. These trends are caused by structure-forming processes (deformation strengthening, recrystallization) which were documented by micrographs (see Fig. 2 for example). Values of strength properties may be influenced by the described way in the range of approximately 100 MPa, which enables - related to applications in practice -to use the obtained results in formation of technological procedures of forming and heat treatment in cold rolling mills.

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Microstructure and mechanieal properties of cold rolled, annealed HSLA strip steels

Janošec M., Schindler I., Vodárek V., Palát J., Rusz S., Suchánek P., Růžička M., Mistecký E.

Archives of Civil and Mechanical Engineering

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2007

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Vol. 7, no 2

29-38

EN

A large testing programme of a strip steel grade, microalloyed by vanadium, titanium and niobium, was condueted. The experiment was based on combination of cold rolling, recrystallization annealing, mechanical testing, metallographic examinations, SEM and TEM analyses. Samples in the form of stripes with dimensions of 3.9x25x500 mm were rolled in several passes with the total height reduction of 5 to 75%. Particular partial strains were realized at room temperature in the housingless, hydraulically prestressed laboratory mill. Afterwards the laboratory mill products were annealed in the vacuum fumace with the protective gas atmosphere consisting of N2+H2. The annealed samples underwent the tensile test at the room temperature and the Brinell hardness test. The gained results - hardness, yield stress, tensile strength and their ratio, as well as elongation A80, were summarized in dependence on cold deformation before annealing.

PL

Przedstawiono wyniki badań właściwości taśm ze stali mikrostopowych z dodatkami V, Ti oraz Nb. Przeprowadzony eksperyment obejmował walcowanie na zimno, wyżarzanie rekrystalizujące, badania mechaniczne oraz badania metalograficzne metodami SEM i TEM. Próbki w postaci pasów blachy o wymiarach 3,9x25x500 mm walcowano w temperaturze pokojowej, w kilku przepustach z całkowitym gniotem wynoszącym od 5 do 75% na laboratoryjnej bezstojakowej walcarce konstrukcji sprężonej. Odwalcowane pasma następnie wyżarzano w próżniowym piecu w atmosferze gazu ochronnego N2+H2. Wyżarzone próbki poddano próbie rozciągania w temperaturze pokojowej oraz pomiarowi twardości Brinella. Uzyskane wyniki twardość, granica plastyczności, wytrzymałość na rozciąganie oraz wydłużenie A80 zestawiono na wykresach w zależności od odkształcenia względnego. Wyniki badań metalograficznych metodami SEM i TEM były podstawą do analizy zależności pomiędzy właściwościami mechanicznymi a mikrostrukturą. Wykazano, że zwiększanie odkształcenia plastycznego na zimno ogranicza skłonność do rozrostu wydzieleń podczas wyżarzania.

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Influence of cold rolling and annealing on mechanical properties of steel QStE 420

Schindler I., Janošec M., Místecký E., Růžička M., Čížek L., Dobrzański L. A., Rusz S., Suchánek P.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

231--234

EN

Purpose: was to investigate impact of cold reduction size and annealing on mechanical properties of HSLA steel. Design/methodology/approach: Testing of strip steel QStE 420 was based on a combination of cold rolling, recrystallization annealing, mechanical testing and metallographic analyses. Findings: It was confirmed that by a suitable combination of size of previous cold deformation and parameters of the following annealing it is possible to influence considerably a complex of mechanical properties of particular strips. Strength properties were more or less decreasing with the rising annealing temperature, whereas plastic properties were increasing. Research limitations/implications: The experiment should be supplemented by additional modes of soft- and recrystallization annealing. Practical implications: The results may be utilized for optimization of terms of heat treatment in a cold rolling mill, exactly in accordance with specific requirements for a relation between plastic and strength properties of the investigated material. Originality/value: Research possibilities of VSB-TUO in the sphere of cold rolling were introduced for the first time.

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The comparison of power, economy and ecological parameters of spark-ignition engine of lawn mowers

Kadleček B., Pejša L., Růžička M.

Eksploatacja i Niezawodność

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2005

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nr 3

50-54

EN

The subject of this report is a description of measuring results and mutual comparison of power, economy and ecological parameters of spark-ignition engines. Four engines equipped with a vertical crank-shaft with power from 3 to 5 kW were compared. These engines were mounted as a drive unit on lawn mowers.

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Future trends in design of construction and agricultural machines

Voštová V., Vondráčková T., Růžička M.

Eksploatacja i Niezawodność

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2005

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nr 3

55-57

EN

New trends in design of construction and agricultural machines are apparent mainly in aims that they should achieve e.g. economic transport, more efficient work technologies, environmental protection etc. The controlling process of building or agricultural technologies is often very similar. This operational control includes e.g. laser methods that operate construction and agricultural machines by means of total station; Global Position System (GPS) with a mobile map utilization that controls construction and agricultural machines etc. The mutual combination of these systems can be seen as well. Stability analysis of the system implementation is to be done in Czech Republic. The main reason for the analyses is eventual wearing out of firm's machinery. The paper describes the mathematical model of laser control and dozer's work technology with the utilization of GPS and laser.