Effects of Nb on Strain-Induced Precipitation of NbC and Static Recrystallization for High Nb Pipeline Steels

2010 ◽  
Vol 146-147 ◽  
pp. 1315-1321 ◽  
Author(s):  
Gui Ying Qiao ◽  
Fu Ren Xiao ◽  
Xiao Bing Zhang ◽  
Shao Hui Chen ◽  
Bo Liao
Keyword(s):  
Activation Energy ◽  
Stress Relaxation ◽  
Compression Test ◽  
Static Recrystallization ◽  
Pipeline Steel ◽  
Relaxation Technique ◽  
Start Time ◽  
Pipeline Steels ◽  
Kinetics Of Precipitation ◽  
Kinetics Of

Strain-induced precipitation of complex carbonitrides and recrystallization for three high-Nb pipeline steels with different Nb and C content have been studied by using a stress relaxation technique and two-passes interrupted compression test. Sequentially, the PTT diagrams were obtained, and static recrystallization activation energy was calculated. Furthermore, the effects of Nb and C content on strain-induced NbC precipitation and static recrystallization were discussed. The results confirm the faster kinetics of precipitation and its retarded recrystallization in the case of higher Nb pipeline steel, and that the recrystallization is easier in low Nb pipeline steel in comparison to the case of high Nb steel. However, the effects of Nb on strain-induced precipitation and static recrystallization were associated with the Nb/C ratio. The precipitation start time (Ps) of strain-induced NbC is delayed in lower Nb/C ratio pipeline steel. It is suggested that the reduced supersaturation of Nb can result in the delay of precipitation of strain-induced NbC carbides forming in the low Nb/C ratio steel.

Characteristics of the Static Recrystallization Kinetics of an Intercritically Deformed C-Mn Steel

2004 ◽  
Vol 467-470 ◽  
pp. 293-298 ◽  
Author(s):  
Haiwen Luo ◽  
Jilt Sietsma ◽  
Sybrand van der Zwaag
Keyword(s):  
Stress Relaxation ◽  
Static Recrystallization ◽  
Avrami Exponent ◽  
Recrystallization Kinetics ◽  
Ferrite Fraction ◽  
Austenite Recrystallization ◽  
Austenite Grains ◽  
Intercritical Region ◽  
Mn Steel ◽  
Kinetics Of

The austenite recrystallization kinetics in the intercritical region of a C-Mn steel is investigated by means of stress relaxation tests. It is found that the Avrami exponent, n, decreases significantly with decreasing temperature, i.e. with increasing ferrite fraction. This behaviour deviates from that of austenite recrystallization in the purely austenitic state, in which case the Avrami exponent is constant and independent of temperature and deformation. To interpret this, the influence of spatial variation of the plastic strain in the intercritical austenite grains on recrystallization kinetics is modelled quantitatively. The modelling results seem to indicate that the strain heterogeneity is responsible for the decreasing Avrami exponent with decreasing intercritical temperature.

Effect of Austenite Deformation on Recrystallisation Behaviour in an X-70 Microalloyed Steel

2010 ◽  
Vol 89-91 ◽  
pp. 721-726 ◽  
Author(s):  
Lin Sun ◽  
Bradley P. Wynne ◽  
Eric J. Palmiere
Keyword(s):  
Microalloyed Steel ◽  
Pipeline Steel ◽  
Current Model ◽  
Compression Tests ◽  
Precipitation Kinetics ◽  
Start Time ◽  
Critical Temperatures ◽  
Softening Parameter ◽  
Fractional Softening ◽  
Kinetics Of

In the present study, the effect of austenite deformation on the recrystallisation behaviour in terms of recrystallisation-stop and recrystallisation-limit temperatures (T5% and T95%) of an X70 niobium microalloyed pipeline steel have been investigated by interrupted plane strain compression tests. The extents of recrystallisation are calculated using a modified fractional softening parameter. And the 20% and 60% of fractional softening were correlated to T5% and T95%. Quantitative optical metallography indicates that this method provides for a convenient and reliable experimental measurement of the critical temperatures associated with the recrystallisation of austenite. The recrystallisation kinetics and the precipitation kinetics of Nb(CN) were calculated using two widely applied models. The experimental results from this study suggest that the current model of precipitation kinetics might overestimate the precipitation start time.

Studies on softening kinetics of niobium microalloyed steel using stress relaxation technique

2010 ◽  
Vol 4 (2) ◽  
pp. 197-201 ◽  
Author(s):  
Cheng-Liang Miao ◽  
Cheng-Jia Shang ◽  
Guo-Dong Zhang ◽  
Guo-Hui Zhu ◽  
Hatem Zurob ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Microalloyed Steel ◽  
Relaxation Technique ◽  
Niobium Microalloyed Steel ◽  
Kinetics Of

A Review of the Stress-Relaxation Method for Following the Kinetics of Precipitation, Recovery and Recrystallization

2012 ◽  
Vol 706-709 ◽  
pp. 2758-2763 ◽  
Author(s):  
W.J. Liu
Keyword(s):  
Stress Relaxation ◽  
Relaxation Rate ◽  
Relaxation Method ◽  
Dislocation Model ◽  
Precipitation Kinetics ◽  
Kinetics Of Precipitation ◽  
Kinetics Of

Stress-relaxation method was first used by Liu and Jonas in 1980s for following the kinetics of strain induced precipitation of carbonitrides in austenite. Since then, the method has been widely employed for studying not only the precipitation kinetics but also the recovery and recrystallization processes in steels and other alloys. In the present paper, the principle and the worldwide usage of the method were reviewed. The dependence of stress relaxation rate on the occurrence of precipitation, recovery and recrystallization was interpreted based on a dislocation model. The capabilities and the limitations of the method were discussed and ways to overcome the existing limitations were also proposed.

Effects of Rare Earths on the Austenite Recrystallization Behavior in X80 Pipeline Steel

2010 ◽  
Vol 129-131 ◽  
pp. 542-546 ◽  
Author(s):  
Hong Liang Liu ◽  
Cheng Jun Liu ◽  
Mao Fa Jiang
Keyword(s):  
Activation Energy ◽  
Rare Earths ◽  
Static Recrystallization ◽  
Pipeline Steel ◽  
High Strength ◽  
Vacuum Induction Furnace ◽  
Recrystallization Behavior ◽  
X80 Pipeline Steel ◽  
Austenite Recrystallization ◽  
Activation Energy Of Deformation

In order to improve the effects of rare earths (RE) as microalloy on the recrystallization behavior in the high strength micro-alloyed steel, the X80 pipeline steels with different RE content were produced with a vacuum induction furnace, a series of hot torsion tests were performed under a range of deformation conditions, and the stress-strain curves were analyzed. The results showed that trace RE would improve the austenite recrystallization behavior. The activation energy of deformation and static recrystallization of the austenite in the X80 pipeline steel without RE additions were respectively 393 and 366 kJ/mol. When the RE addition was 0.0025 wt.%, the activation energy of deformation and static recrystallization were reduced by 33 and 29 kJ/mol respectively. But when the RE addition was increased to 0.0220 wt.%, RE would significantly inhibit the dynamic recrystallization of the austenite, the activation energy of deformation would be increased by 35 kJ/mol, but the activation energy of static recrystallization would reduce by 15 kJ/mol.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

1982 ◽  
Vol 47 (7) ◽  
pp. 1780-1786 ◽  
Author(s):  
Rostislav Kudláček ◽  
Jan Lokoč
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Liquid Phase ◽  
Ionizing Radiation ◽  
Oxide Catalyst ◽  
Absorbed Dose ◽  
Hydrogenation Rate ◽  
Solution Composition ◽  
Mixed Catalyst ◽  
Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

scholarly journals Fluoride Leaching of Titanium from Ti-Bearing Electric Furnace Slag in [NH4+]-[F−] Solution

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1176
Author(s):  
Fuqiang Zheng ◽  
Yufeng Guo ◽  
Feng Chen ◽  
Shuai Wang ◽  
Jinlai Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electric Furnace ◽  
Kinetic Equations ◽  
Surface Chemical ◽  
Leaching Rate ◽  
Surface Chemical Reaction ◽  
Mechanism And Kinetics ◽  
Semi Empirical ◽  
Kinetics Of ◽  
Furnace Slag

The effects of F− concentration, leaching temperature, and time on the Ti leaching from Ti-bearing electric furnace slag (TEFS) by [NH4+]-[F−] solution leaching process was investigated to reveal the leaching mechanism and kinetics of titanium. The results indicated that the Ti leaching rate obviously increased with the increase of leaching temperature and F− concentration. The kinetic equation of Ti leaching was obtained, and the activation energy was 52.30 kJ/mol. The fitting results of kinetic equations and calculated values of activation energy both indicated that the leaching rate of TEFS was controlled by surface chemical reaction. The semi-empirical kinetics equation was consistent with the real experimental results, with a correlation coefficient (R2) of 0.996. The Ti leaching rate reached 92.83% after leaching at 90 °C for 20 min with F− concentration of 14 mol/L and [NH4+]/[F−] ratio of 0.4. The leaching rates of Si, Fe, V, Mn, and Cr were 94.03%, 7.24%, 5.36%, 4.54%, and 1.73%, respectively. The Ca, Mg, and Al elements were converted to (NH4)3AlF6 and CaMg2Al2F12 in the residue, which can transform into stable oxides and fluorides after pyro-hydrolyzing and calcinating.

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

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