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Influence of cooling rate on microstructure of a NB-V HSLA steel

Legerski M., Schindler I., Suchánek P.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2007

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Vol. 321, z. 89

115-116

EN

In most cases an effort is made to combine controlled rolling of the microalloyed steel with its accelerated cooling, which has a favourable influence mainly on size of the resulting ferritic grain. In practice an opposite case may sometimes happen, where even slowed down cooling of final rolled products occurs. For example, after rolling of universal mill plates in a three-high mill the rolled products are not water-sprayed but they cool from the finish rolling temperature in collection pits, where accumulation of a larger quantity of the hot material strongly reduces speed of cooling down the material, compared also with free cooling in the air. In laboratory experiments mentioned below a simplified simulation of controlled finish rolling and slowed down cooling of such universal mill plates was carried out.

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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.

3

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.