Characterization of Strain Induced Precipitation of Nb in Microalloyed Austenite Using Classical and Novel Techniques

Iparraguirre, C.; Fernández-Calvo, Ana Isabel; López, Beatriz; Scott, Colin; Rose, Aleena; Kranendonk, W.; Soenen, B.; Paul, Georg

doi:10.4028/www.scientific.net/msf.500-501.677

Cited by 12 publications

(13 citation statements)

References 15 publications

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“…To the authors knowledge, very few data is available on the comparison of the recrystallized fraction obtained from different simulation techniques. Only Iparraguirre et al 26 compared softening fractions obtained from plastodilatometry and from torsion, showing a difference in softening level between both types of tests. In spite of these differences, they found a relatively good correlation in the measurements of the precipitate size and the amount of Nb precipitated in the different types of experiments.…”

Section: Resultsmentioning

confidence: 99%

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Characterization of the Austenite Recrystallization by Comparing Double Deformation and Stress Relaxation Tests

Vervynckt

Verbeken

Thibaux

et al. 2010

steel research int.

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A high amount of deformation below the non-recrystallization temperature (T nr ) is a common industrial practice to achieve a good combination of toughness and strength in microalloyed steels. To combine the industrially relevant optimum combination of high productivity and product quality, an accurate knowledge of T nr and the recrystallization kinetics is required. Although a lot of literature data is available on the recrystallization behaviour of microalloyed steels, correlations are often difficult to be made due to the effect of different experimental setups, types of analysis and test schedules that are used to obtain this data. Although this would significantly improve the knowledge about these steels, so far, no systematic comparison has been presented in literature to correlate the different techniques and methods. In this study, different hot rolling simulation techniques, testing schedules and types of analysis were used to determine the recrystallization kinetics of a microalloyed steel. On the one hand, good agreement was found between the results from different test equipment for the double deformations tests. On the other hand, stress relaxation tests showed accelerated kinetics and appeared to be less effective.

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Section: Resultsmentioning

confidence: 99%

“…So far, only few comparisons between different techniques and methods were reported. Iparraguirre et al 26 studied the differences in recrystallization behavior by double deformation testing using different mechanical testing modes, i.e. uniaxial compression on a dilatometer and torsion tests.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Austenite Recrystallization by Comparing Double Deformation and Stress Relaxation Tests

Vervynckt

Verbeken

Thibaux

et al. 2010

steel research int.

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“…In some cases precipitates are detected on replicas before the onset of precipitation is defined by the "plateau" in the softening curve. 41,42) On the other hand, difficulties arise in separating the hardness increment owing to the precipitates from other mechanisms, such as grain size strengthening, solid solution strengthening and dislocation strengthening. 30) It has been found that microhardness measurements lead to longer periods than in chemical analysis for strain-induced precipitation measurements.…”

Section: Precipitation Constantsmentioning

confidence: 99%

Improved Model of Kinetics of Strain Induced Precipitation and Microstructure Evolution of Nb Microalloyed Steels during Multipass Rolling

2008

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One of the main problems of empirical and semi-empirical models that are used to predict austenite microstructure evolution during hot rolling is their limited range of applicability regarding chemical compositions. This paper aims to improve a previous microstructural model paying special attention to the development of a more general equation for the prediction of the onset of strain induced precipitation in Nb microalloyed steels. This has been done with the help of new expressions describing the kinetics of strain induced precipitation as a function of the chemical composition. Moreover, the evolution of strain induced Nb precipitation was also modeled in order to determine the amount of Nb precipitated after each strain pass. The predictions obtained with the new model have been compared to results obtained in multipass laboratory tests using several Nb microalloyed steels. The model allows us to better understand the complex interactions occurring between Nb and microstructural softening depending on composition and process parameters.

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“…This is reasonable taking into account previous experiences relative to the size of precipitates found at initial stages of strain induced precipitation. [27][28][29] In the same figure the F PIN corresponding to a nitrogen content of 40 ppm has been included for comparison, since this value is within the typical range of industrial eutectoid steel grades without specific nitrogen addition. The reduction in nitrogen from 110 to 40 ppm shifts the precipitation start temperature of VN in austenite to significantly lower temperatures, reducing almost completely the possibility of interaction between recrystallization and precipitation during practical rolling.…”

Section: )mentioning

confidence: 99%

“…27) and between 14 and 27 % in Ref. 28) for Nb(C, N) precipitation. It must be taken into account that in the present study precipitation was analyzed after the last pass, i.e.…”

Section: Austenite Conditioningmentioning

confidence: 99%

Role of Vanadium Microalloying in Austenite Conditioning and Pearlite Microstructure in Thermomechanically Processed Eutectoid Steels

Jorge-Badiola¹,

Iza-Mendia²,

López³

et al. 2009

ISIJ Int.

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Multipass torsion tests were carried out with two eutectoid steels, one microalloyed with vanadium, using different deformation sequences. The aim of the study was to investigate the potency of vanadium in the retardation of recrystallization for accumulating strain in the austenite. The study showed that at certain deformation conditions well defined non-recrystallization temperatures (T nr ) were observed in the vanadium microalloyed steel. As a consequence, an increase in the austenite grain boundary area per unit volume (S V ) was obtained which led to a refinement of the "ferrite unit" size in the pearlite.KEY WORDS: eutectoid steel; vanadium microalloying; austenite conditioning. 1615© 2009 ISIJ proved toughness.Nevertheless, there is a lack of knowledge concerning the potential use of vanadium for the accumulation of strain in eutectoid steels and the optimum deformation conditions to achieve this. This paper attempts to analyze the potency of vanadium to accumulate strain in the austenite through the application of thermomechanical treatments. Experimental ProcedureTwo eutectoid steels were considered for this study: a plain carbon one and another microalloyed with vanadium, both having the same base composition. The C-Mn steel was commercially produced in bar shape, while the C-Mn-V was cast in the laboratory by adding vanadium after remelting the above C-Mn steel. Afterwards the resulting slabs were hot worked to square ingots. The compositions of the materials are indicated in Table 1.Multipass torsion tests were carried out to determine the non-recrystallization temperature (T nr ). Specimens, having a gauge length of lϭ12 mm with a diameter of 2rϭ6 mm, were reheated for 15 min at 1 200°C. After reheating the samples were deformed applying 24 passes at decreasing temperature in the range 1 150-800°C. The measured torque G and the twist q were converted to von Mises equivalent stress (s) and strain (e) with the help of these equations:.................... (1) The tests were performed using different pass-strains: eϭ 0.2-0.3-0.4. The strain-rate used in all the tests was e˙ϭ 1.5 s Ϫ1, and the interpass time at each deformation stage was 10 s. During deformation a cooling rate of 1.5°C/s was applied. In a particular test, the strain per pass, strain-rate and interpass time were held constant. The values of the T nr were calculated by using the method proposed by Bai et al.,12) from the graphic representation of the mean flow stress (MFS) versus the inverse absolute temperature for each one of the passes.The initial austenite grain size prior to deformation was determined in specimens directly quenched after reheating treatment. In most tests, the specimens were also directly quenched after deformation for the analysis of the austenite microstructure. Some additional tests were carried out applying natural cooling (ϳ3°C/s) after deformation for the study of the pearlite microstructure.The metallographic observation of the samples was done on a surface parallel to the torsion axis at a distance close to ...

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Characterization of Strain Induced Precipitation of Nb in Microalloyed Austenite Using Classical and Novel Techniques

Cited by 12 publications

References 15 publications

Characterization of the Austenite Recrystallization by Comparing Double Deformation and Stress Relaxation Tests

Characterization of the Austenite Recrystallization by Comparing Double Deformation and Stress Relaxation Tests

Improved Model of Kinetics of Strain Induced Precipitation and Microstructure Evolution of Nb Microalloyed Steels during Multipass Rolling

Role of Vanadium Microalloying in Austenite Conditioning and Pearlite Microstructure in Thermomechanically Processed Eutectoid Steels

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