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1

Effect of cold rolling and annealing on mechanical properties of HSLA steel

Schindler I., Janosec M., Mistecky E., Ruzicka M., Cizek L., Dobrzański L. A., Rusz S., Suchanek P.

Archives of Materials Science and Engineering

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2009

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Vol. 36, nr 1

41-47

EN

Purpose: was to examine effect of the parameters of cold deformation and recrystallization annealing on mechanical properties of a Nb-microalloyed HSLA steel. Design/methodology/approach: Research of strip steel QStE 420 was based on a combination of laboratory cold rolling, recrystallization annealing in vacuum furnace, mechanical (particularly tensile) tests and metallographic analyses. Findings: It was validated that by a sophisticated combination of size of previous cold reduction size and parameters of the following annealing it is possible to impact markedly a set of final properties of particular strips. Formability of the studied HSLA steel rises and vice versa strength properties fall with an increasing temperature of annealing. Research limitations/implications: The experiment should be supplemented by additional TEM analyses explaining the behaviour and role of precipitates. Practical implications: The experimentally obtained particular trends of mechanical properties may be utilized for optimization of conditions of heat treatment of the investigated HLSA steel in a cold strip rolling mill, reflecting the specific requirements for a relation between strength and plastic properties. Originality/value: Experimental potentialities of the Institute of Modelling and Control of Forming Processes in the sphere of cold rolling and heat treatment were introduced in their integrity for the first time.

2

Several approaches to ADC transfer function approximation and their application for ADC non-linearity correction

Suchanek P., Slepicka D., Haasz V.

Metrology and Measurement Systems

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2008

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Vol. 15, nr 4

501-511

EN

The performance of current electronic devices is mostly limited by analog front-end and analog-to-digital converter's (ADC) actual parameters. One of the most important parameters is ADC nonlinearity. The correction of this imperfection can be accomplished in the output data but only if the nonlinearity is well characterized. Many approaches to ADC characterization have been proposed in scientific articles in the last several years. In this paper three different approximations of ADC low-frequency non-linearity (common polynomials, Chebyshev polynomials and Fourier series) were analyzed and the practical applicability, approximation accuracy and noise sensitivity were investigated. The first results of nonlinearity correction were presented, too.

3

Properties of a Nb-V-Ti microalloyed steel influenced by cold rolling and annealing

Janosec M., Schindler I., Palat J., Cizek L., Vodarek V., Mistecky E., Ruzicka M., Dobrzański L. A., Rusz S., Suchanek P.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 20, nr 1-2

251-254

EN

Purpose: was to investigate impact of cold forming and annealing on microstructural and mechanical properties of HSLA steel. Design/methodology/approach: Testing of Nb-V-Ti microalloyed strip steel was based on a combination of cold rolling, recrystallization annealing, mechanical testing, metallography and TEM. Findings: It was confirmed that by a suitable combination of size of previous cold reduction size and parameters of the following annealing it is possible to influence considerably a complex of mechanical properties of particular strips. Strength as well as plastic properties depended on the course of recrystallization and precipitates' coarsening during annealing. Research limitations/implications: The experiment should be supplemented by the more detailed analyses of microstructure. Practical implications: The results may be utilized for optimization of terms of heat treatment in a cold rolling mill, especially in accordance with specific requirements for a relation between plastic and strength properties of the investigated steel. Originality/value: Research possibilities of VSB-TUO in the sphere of cold rolling of Nb-V-Ti HSLA steel were introduced in combination with the complex approach to processing of the obtained results.

4

Mathematical description of deformation resistance of IF steel including influence of phase transformations

Schindler I., Plura J., Jurko V., Rusz S., Suchanek P., Janosec M.

Computer Methods in Materials Science

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2007

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Vol. 7, No. 1

24-28

EN

The aim of work was to describe by a single equation deformation resistance of IF steel with titanium in the temperature range of 700 to 1200 °C, in relation to the forming temperature T [°C], equivalent strain ? and equivalent strain rate ? [s-1]. Chemical composition of the investigated material (in wt %) was as follows: 0.004 C – 0.127 Mn – 0.008 Si – 0.008 P – 0.009 S – 0.041 Al – 0.003 N – 0.072 Ti – 0.040 Cu – 0.013 Ni – 0.003 Mo – 0.003 As – 0.003 Sn (other elements max. 0.002 % each). The mean equivalent stress ?m [MPa] was determined by an original procedure, based on laboratory rolling of flat samples with scaled-in thickness in the computer controlled mill Tandem. Values of ?m were computed from values of the registered roll forces by means of a specially developed methodology that uses (among others) knowledge of a particular equation for description of the forming factor for the stand A of the mill Tandem, in dependence on geometric conditions of rolling. Variables ? (in the range of ca 0.1 – 0.5) and ??(in the range of ca 10 – 120 s-1) were expressed by an automatic procedure from the registered actual revolutions of rolls and dimensions of samples measured before and after rolling. Due to an intended application of results in rolling at very low temperatures (above all in the ferrite region) and in accumulative roll bonding, the samples were heated directly to the forming temperature, which – of course – influenced the temperature boundaries between the ferrite region, a two-phase region ferrite + austenite and the austenite region. These temperature boundaries were determined experimentally as 917 °C, or 959 °C. Coefficients A, B, C and D were calculated in a simple equation of type ?m = A • ?B?• ?C • exp(-D • T) for each of the given temperature ranges. A proved method of multiple non-linear regression and statistic software Unistat 5.5 were utilized for this calculation. Due to effect of chemical composition of the investigated IF steel its deformation behaviour in all three temperature regions is very different. With decrease in temperature the deformation resistance of austenite and ferrite increases and, on the other side, fiercely falls in the two-phase region due to a rising share of softer ferrite. A top phase of the describing work was represented by an attempt to describe this deformation behaviour by a single equation. After a large analysis a certain way was proposed in the end, which uses a cumulative function in which particular members are multiplied by coefficient 1 or 0, in dependence on a specific temperature. Calculations of specific coefficients had to be proposed in such a way so that they could react to surpassing of temperature boundaries between individual phase regions. Relative deviations of values??m, calculated on the basis of the gained universal equation back for conditions of the laboratory rolling, from values of the mean equivalent stress expressed directly from roll forces do not surpass š 10 %. It may be considered to be very good accuracy, for instance from viewpoint of adaptive control systems in hot rolling mills. However, only practical applications suggest whether it will be possible to use a single (universal), but quite complicated, model for conditions of fast control of real rolling mills, or whether simple, but of course temperature limited, relationships creating partial fragments of this complex model will be preferred.

PL

Opracowanie pojedynczego równania opisującego opór sta IF z dodatkami tytanu w różnych temperaturach (od 700°C i 1200°C) z uwzględnieniem wpływu temperatury procesu odkształcenia logarytmicznego e h i średniej wartości intensywności odkształcenia e jest tematem niniejszej pracy. Średnie wartości intensywności naprężenia om zostały wyznaczeni z testów walcowania próbek płaskich o zróżnicowanej wy|gch sokości na walcarce Tandem, bazując na zmierzonych siłach. Do obliczenia wartości sigma m z sił zastosowano opracowaną metodę wykorzystującą odpowiednie równania opisujące poszczególne parametry walcowania na walcarce Tandem.

5

Deformation behaviour of low carbon deep-drawing steels influenced by phase transformation

Schindler I., Legerski M., Suchanek P., Rusz S., Janosec M.

Archives of Civil and Mechanical Engineering

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2007

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Vol. 7, no 1

93-100

EN

The aim was to determine the phase transformations temperatures of a specific IF steel grade, microalloyed by titanium, and quantify influence or phase composition on its deformation resistance in comparison with a common low carbon deep-drawing steel grade. In the case or the IF steel separate, sufficiently accurate, models describing mean equivalent stress after heating or the material directly to the forming temperature, matter for three temperature regions (ferrite, ferrite + austenite, or austenite), were developed.

PL

Celem badań było wyznaczenie temperatur przemian fazowych dla stali typu IF z mikrostopowym dodatkiem tytanu oraz ilościowe określenie wpływu składu fazowego na opory kształtowania, szczególnie w porównaniu ze zwykłym gatunkiem niskowęglowej stali do głębokiego tłoczenia. Zastosowano odrębne modele opisujące średnie odkształcenie zastępcze w funkcji temperatury, odkształcenia i prędkości odkształcenia dla trzech zakresów temperatur (odpowiadających występowaniu struktury ferrytu, ferrytu i austenitu oraz samego austenitu). Wartości temperatur określających te zakresy nie odpowiadają dokładnie temperaturze przemian fazowych, wyznaczanych podczas chłodzenia materiału. Wynika to stąd, że dane wejściowe dla tych modeli były uzyskane podczas nagrzewania stali do temperatury obróbki plastycznej. Uzyskane wyniki potwierdzają teoretyczne założenia o spadku oporów kształtowania w wyniku zmniejszenia zawartości węgla oraz w wyniku obecności miękkiej fazy ferrytycznej w stalach niskowęglowych. Względnie niski opór kształtowania ferrytu może być wykorzystany podczas walcowania stali IF w zakresie występowania struktury ferrytycznej.

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Control of chemical composition of slag in ladle furnace

Adolf Z., Suchanek P.

Prace Instytutu Metalurgii Żelaza

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2006

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T. 58, nr 4

59-60

EN

Authors compare slag regime for heat in ladle furnace at making of steel for rails. The works were aimed at formulation of conditions for replacement of fluorspar slag by alumina slag with preservation of identical refining effects. Both types of slag were assessed according to mass of admixtures added into ladle, mass of ladle slag, corrosion effect of slag on lining and their ability to desulphurise steel.

PL

Autorzy porównują warunki pracy żużla wsadowego do piecokadzi w czasie procesu odlewania stali na szyny. Prace miały na celu sformułowanie warunków dotyczących zastąpienia żużla fluorytowego żużlem glinowym z zachowaniem identycznych warunków rafinacji. Oba rodzaje żużla zostały poddane ocenie ze względu na masę domieszek dodanych do kadzi, masę żużla kadziowego, wpływ żużla na korozję wyłożenia i zdolność do odsiarczania stali.