The combined effect of chemical composition and cooling rate on transformation temperatures of hypoeutectoid steels

The transformation temperatures A(r3) and A(r1) of four unalloyed hypoeutectoid steels with a carbon content of 0.029-0,73 % were determined using dilatometric tests. Unusually high cooling rates of 2 and 8 degrees C s(-1) were used intentionally, corresponding to the conditions in the wire rod rolling mills The developed regression models are phenomenological and allow a simple prediction of transformation temperatures, depending only on the cooling rate and the chemical composition of the steel represented by the carbon equivalent (in the case of A(r1)), respectively by the A(c3) temperature (for A(r3)). When calculating the A(c3) temperature, it was worth considering its non-linear dependence on carbon content. It has been verified that the derived equations are applicable even at relatively low cooling rates when the austenite decomposes exclusively on ferrite and pearlite.Web of Science56317016

Study of the effect of deformation on transformation diagrams of two low-alloy manganese-chromium steels

The work deal with an assembling and comparing of transformation diagrams of two low-alloy steels, specifically 16MnCrS5 and 20MnCrS5. In this work, diagrams of the type of CCT and DCCT of both steels were assembled. Transformation diagrams were assembled on the basis of dilatometric tests realized on the plastometer Gleeble 3800, of metallographic analyses and of hardness measurements. In addition, for comparison, the transformation diagrams were assembled even with use of the QTSteel 3.2 software. Uniform austenitization temperature of 850°C was chosen in case of both steels and even both types of diagrams. In case of both steels, an influence of deformation led to expected acceleration of phase transformations controlled by diffusion and also of bainite transformation. In both cases, the kinetics of martensitic transformation was not significantly affected by deformation.Web of Science6341741173

The influence of deformation and austenitization temperature on the kinetics of phase transformations during cooling of high-carbon steel

The aim of the performed experiments was to determine the influence of deformation and of austenitization temperature on the kinetics of phase transformations during cooling of high-carbon steel (0.728 wt. % C). The CCT and DCCT diagrams for austenitization temperature 940 degrees C and DCCT diagram for austenitization temperature 1000 degrees C were constructed with the use of dilatometric tests. On the basis of obtained results, a featureless effect of austenitization temperature and deformation on the kinetics of phase transformations during cooling of investigated steel was observed. Critical cooling rates for the transformation of martensite in microstructure fluctuated from 5 to 7 degrees C . s(-1) (depending on the parameters of austenitization and deformation), but only at cooling rates higher than 8 degrees C . s(-1) a dominant share of martensite was observed in the investigated steel, which resulted in the significant increase of hardness.Web of Science6341748174

Study of hot deformation behavior of CuFe2 alloy

Nil strength temperature of 1062 degrees C and nil ductility temperature of 1040 degrees C were experimentally set for CuFe2 alloy. The highest formability at approx. 1020 degrees C is unusable due to massive grain coarsening. The local minimum of ductility around the temperature 910 degrees C is probably due to minor formation of gamma-iron. In the forming temperatures interval 650-950 degrees C and strain rate 0.1-10 s(-1) the flow stress curves were obtained and after their analysis hot deformation activation energy of 380 kJ.mol(-1) was achieved. Peak stress and corresponding peak strain values were mathematically described with good accuracy by equations depending on Zener-Hollomon parameter.Web of Science64270670

High-temperature deformation properties of CuCr0.6 alloy

The submitted paper aimed to investigate the hot deformation behavior of CuCr0.6 alloy. Nil strength temperature of 1349 K and nil ductility temperature of 1313 K have been experimentally determined. Formability is monotonously increased with the decrease of forming temperature in the temperature range from 923 K to approx. 1273 K. The flow stress curves were obtained in the forming temperature interval of 923-1223 K and at a strain rate of 0.1-10 s(-1). After their analysis, the hot deformation activation energy of 340 kJ mol(-1) was calculated for peak stress and 393 kJ mol(-1) for steady state. This proves that the value of the activation energy depends upon a strain size.Web of Science57641440

Hot formability of heat-resistant stainless steel X15CrNiSi 20-12

High-temperature plastic properties of heat-resistant stainless steel X15CrNiSi 20-12 were assessed on the basis of hot tensile tests and nil strength tests. The results were supported by metallographic analyses using SEM and EDX analysis. The formability of the investigated steel can be divided into roughly three temperature areas. In the temperature range of 900 degrees C to about 1050 degrees C, formability was negatively affected by precipitation of carbide particles at grain boundaries. As the temperature rose to 1200 degrees C, these particles dissolved, resulting in an increase in formability. Further temperature increases resulted in a relatively steep drop in formability caused by overheating of the material. The nil ductility temperature of 1280 degrees C and the nil-strength temperature of 1362 degrees C were determined. The Plastic and strength properties of the investigated material were compared with the deformation behavior of the reference steel X5CrNi 18-10, which shows a significantly wider range of suitable forming temperatures.Web of Science65273472

Effect of strain on transformation diagrams of 100Cr6 steel

Based on dilatometric tests, the effect of various values of previous deformation on the kinetics of austenite transformations during the cooling of 100Cr6 steel has been studied. Dilatometric tests have been performed with the use of the optical dilatometric module of the plastometer Gleeble 3800. The obtained results were compared to metallographic analyses and hardness measurements HV30. Uniaxial compression deformations were chosen as follows: 0, 0.35, and 1; note that these are true (logarithmic) deformations. The highly important finding was the absence of bainite. In addition, it has been verified that with the increasing amount of deformation, there is a further shift in the pearlitic region to higher cooling rates. The previous deformation also affected the temperature martensite start, which decreased due to deformation. The deformation value of 1 also shifted the critical cooling rate required for martensite formation from the 12 degrees C/s to 25 degrees C/s.Web of Science104art. no. 32

Structure-forming processes at temperature-controlled rolling and cooling of seamless tubes of HSLA steel

Import 23/08/2017V laboratorních podmínkách byly zkoumány strukturotvorné procesy u HSLA oceli o složení 0,17 C – 1,1 Mn – 0,2 Si – 0,028 Al – 0,011 N – 0,025 Nb (ve hm. %). Byly také vyhodnoceny vlivy doválcovacích teplot na výslednou strukturu a byla stanovena teplota nulové rekrystalizace oceli těsně nad teplotou 850 °C. Byltaké sestaven DCCT diagram po deformaci na teplotě 900 °C. Snižování doválcovací teploty v intervalu 990 – 850 °C vedlo ke zjemňování zrna a homogenizaci výsledné mikrostruktury. Razantní pokles velikosti zrna pod teplotou 890 °C byl nejpravděpodobněji způsoben precipitací, která zpomalila rekrystalizaci. Laboratorním válcováním bylo dosaženo nejmenší velikosti zrna 17 µm. Bylo zjištěno, že válcovací síla při teplotě 850 °C byly zhruba o 60 % vyšší, než v případě doválcování při 990 °C.In the laboratory conditions, the structuring processes of HSLA steel with a composition of 0.17 C - 1.1 Mn - 0.2 Si - 0.028 Al - 0.011 N - 0.025 Nb (in wt. %) were investigated. The effects of finish rolling temperatures on the resulting structure were also evaluated and the non-recrystallization temperature of the steel was determined just above 850 ° C. The DCCT diagram after deformation at 900 ° C was assembled. Decreasing of the finish rolling temperature in the range 990 - 850 ° C resulted in grain refinement and homogenization of the resulting microstructure. The apparent decrease in grain size below 890 ° C was most likely due to precipitation, which slowed recrystallization. Laboratory rolling has achieved a smallest grain size of 17 μm. It was found that the rolling force at 850 °C was about 60% higher than the rolling at 990 ° C.633 - Katedra tváření materiáluvýborn

Biochemical measurements by SPRi method

Import 05/08/2014Použitím biosenzorů založených na principu rezonance povrchových plasmonů (SPR) docílíme efektivního způsobu měření biochemických látek. Metodou SPRi (metoda SPR s použitím CCD prvku pro záznam) je možné měřit desítky až stovky látek najednou v důsledku přítomnosti biologických rozpoznávacích prvků na biosenzoru. Výhodou této optické metody je měření v reálném čase s nižšími náklady, než nabízí běžně používané metody. Tato bakalářská práce je zaměřena na přípravu, měření biochemických látek pomocí biosenzorů a vyhodnocení provedených měření v laboratoři Vysoké školy báňské- Technické univerzity Ostrava.We can attain efficient way of measuring biochemical substances by using biosensors based on surface plasmon resonance (SPR) principle. With SPRi method (SPR method enhanced with CCD element for recording) is possible to measure large number of substances due to the presence of biological recognition elements on biosensor. The advantage of this optic method is real time measurement and lower cost than the commonly used methods. This bachelor thesis will focus on the preparation, measurement of biochemical substances using biosensors and evaluation of measurements performed in the laboratory VŠB-Technical university of Ostrava.516 - Institut fyzikyvelmi dobř