scholarly journals Discussion on the Rate Controlling Process of Coarsening of Niobium Carbonitrides in a Niobium Microalloyed Steel

2005 ◽  
Vol 500-501 ◽  
pp. 703-710 ◽  
Author(s):  
David San Martín ◽  
Francisca García Caballero ◽  
Carlos Capdevila ◽  
Carlos García de Andrés
Keyword(s):  
Grain Growth ◽  
Volume Diffusion ◽  
Microalloyed Steels ◽  
Second Phase ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
The Matrix ◽  
Niobium Microalloyed Steel ◽  
Grain Growth Kinetics ◽  
Austenite Grain Growth

Austenite grain growth in microalloyed steels is governed by the coarsening of fine precipitates present at grain boundaries below the grain coarsening temperature. Zener model is widely used in metals to describe the pinning effect of second phase particles precipitated in the matrix. In this work it has been discussed whether grain boundary or volume diffusion is the rate controlling process for the coarsening of the niobium carbonitrides. Calculations on austenite grain growth kinetics, obtained coupling Zener theory and both rate controlling processes of precipitate coarsening, have been compared against experimental austenite grain size results under nonisothermal heating conditions. In this sense, it has been concluded that the coarsening of niobium carbonitrides is mainly controlled by volume diffusion of Nb in austenite.

Non-Isothermal Austenite Grain Growth Kinetics in the HAZ of a Microalloyed X-80 Linepipe Steel

2011 ◽  
Vol 172-174 ◽  
pp. 809-814 ◽  
Author(s):  
Kumkum Banerjee ◽  
Michel Perez ◽  
Matthias Militzer
Keyword(s):  
Grain Size ◽  
Heating Rate ◽  
Grain Growth ◽  
Growth Kinetics ◽  
Electron Microscopic ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Grain Growth Kinetics ◽  
Austenite Grain Growth ◽  
Linepipe Steel

Non-isothermal austenite grain growth kinetics under the influence of several combinations of Nb, Ti and Mo containing complex precipitates has been studied in a microalloyed linepipe steel. The goal of these studies is the development of a grain growth model to predict the austenite grain size in the weld heat affected zone (HAZ). A detailed electron microscopic investigations of the as-received steel proved the presence of Ti-rich, Nb-rich and Mo-rich precipitates. Inter and intragranular precipitates of ~5-150 nm have been observed. The steel has been subjected to austenitizing heat treatments to selected peak temperatures of 950, 1150 and 1350°C at various heating rates of 10, 100 and 1000°C/s. Thermal cycles have been found to have a strong effect on the final austenite grain size. The increase in heating rate from 100 to 1000°C/s has a negligible difference in the austenite grain size irrespective of the austenitizing temperature. However, the increase in grain size has been noticed at 10°C/s heating rate for all the austenitizing temperatures. The austenite grain growth kinetics have been explained taking into account the austenite growth in the presence of precipitates.

scholarly journals Kinetics of Austenite Grain Growth during a Continuous Heating of a Niobium Microalloyed Steel

2004 ◽  
Vol 467-470 ◽  
pp. 929-934 ◽  
Author(s):  
David San Martín ◽  
Francisca García Caballero ◽  
Carlos Capdevila ◽  
C. Carcía de Andrés
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Heating Rate ◽  
Grain Growth ◽  
Continuous Heating ◽  
Second Phase ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Average Grain Size ◽  
The Matrix

Grain growth is a thermally activated process in which the average grain size increases as temperature and time increases. The driving force for grain growth results from the decrease in the free energy associated with the reduction in total grain boundary energy. There are several known factors that influence the migration of grain boundaries such as second phase particles precipitated in the matrix and the solute elements segregated at grain boundaries. The austenite grain boundaries are revealed using the thermal etching method. Carbon extraction replicas were prepared to determine the composition and size of precipitates present in the matrix. In this work, the evolution of the average prior austenite grain size (PAGS) of a low carbon steel microalloyed with niobium is studied as a function of temperature and heating rate. Austenite grains show a two-stage growth. It has been found that as heating rate increases, the grain coarsening temperature (TGC) increases and the grain size at that temperature decreases. TGC temperature lies around 40-60°C below the temperature for complete dissolution of carbonitrides (TDISS).

Austenite Grain Growth Kinetics in a Low C-Mn Steel and a Ti-Nb-V Microalloyed Steel

2014 ◽  
Vol 1019 ◽  
pp. 327-332 ◽  
Author(s):  
K.A. Annan ◽  
C.W. Siyasiya ◽  
W.E. Stumpf ◽  
K.M. Banks ◽  
A.S. Tuling
Keyword(s):  
Grain Growth ◽  
Microalloyed Steel ◽  
Microalloyed Steels ◽  
Growth Equation ◽  
Austenite Grain ◽  
Grain Growth Kinetics ◽  
Increasing Temperature ◽  
Austenite Grain Growth ◽  
Mn Steel ◽  
Good Agreement

The effect of thermal processing (TMP) parameters on grain growth in a low C - Mn steel and a C - Mn steel microalloyed with Nb, Ti and V were compared as part of a wider study on grain growth in microalloyed steels. The grain growth rate was found to be low at low temperatures and short soaking times but increases significantly with both increasing temperature and time. The activation energy Q, the grain growth equation constants n and A were found to be higher in the microalloyed steel than the plain C-Mn steel. A constitutive model for predicting austenite grain growth in the low C-Mn steel and the microalloyed steel has been developed. The predictive potential of the model is in good agreement with the experimental data.

Austenite Grain Growth Kinetics during Continuous Heating of a Microalloyed X-80 Linepipe Steel

2012 ◽  
Vol 715-716 ◽  
pp. 292-296
Author(s):  
Kumkum Banerjee ◽  
Michel Perez ◽  
Matthias Militzer
Keyword(s):  
Grain Size ◽  
Heating Rate ◽  
Grain Growth ◽  
Growth Kinetics ◽  
Continuous Heating ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Grain Growth Kinetics ◽  
Austenite Grain Growth ◽  
Linepipe Steel

Non-isothermal austenite grain growth kinetics has been studied in a microalloyed linepipe steel with complex precipitates containing Ti, Nb and/or Mo. The goal of these experimental studies is to provide the basis for the development of a grain growth model to predict the austenite grain size evolution in the weld heat affected zone (HAZ). Detailed electron microscopic investigations of the as received steel proved the presence of Ti-rich, Nb-rich and Mo-rich precipitates. The steel was subjected to austenitizing heat treatments to selected peak temperatures of 950, 1150 and 1350 °C at heating rates of 10, 100 and 1000 °C/s, respectively. Thermal cycles have been found to have a strong effect on the austenite grain size. Austenite grain sizes increase with peak temperature and decreasing heating rate. However, the increase in heating rate from 100 to 1000 °C/s has a negligible effect on the austenite grain size. The observed austenite grain growth kinetics can be explained taking into account the potential dissolution of Nb-rich precipitates.

Effect of Rare Earth (RE) La on Solid Solution of Second Phase Particle and Austenite Grain Growth in Steel Containing High Niobium

2011 ◽  
Vol 189-193 ◽  
pp. 2869-2874 ◽  
Author(s):  
Wen Zhong Song ◽  
Qi Fang ◽  
Hui Ping Ren ◽  
Zi Li Jin ◽  
Hui Chang
Keyword(s):  
Solid Solution ◽  
Growth Rate ◽  
Rare Earth ◽  
Grain Growth ◽  
Phase Particle ◽  
Solution Temperature ◽  
Second Phase ◽  
Austenite Grain ◽  
Austenite Grain Growth ◽  
Soaking Temperature

The solid solution of the second phase particle and austenite grain growth behavior of the high niobium-containing RE steel was studied by mathematical calculation and extraction replica technique. The purpose of the study was to investigate the effects of Rare Earth La on austenite grain growth and propose an empirical equation for predicting the austenite grain size of RE steel. Austenite grain grows in an exponential law with the increase of heating temperature, while approximately in a parabolic law with the increase of holding time. Results show that the RE steel has good anti-coarsening ability at elevated temperatures. When soaking temperature is lower than 1250°C , AGS and growth rate are small for high niobium steel, but soaking temperature is lower than 1220°C , AGS and growth rate are small for RE steel. RE La can promote solid solution of second-phase particles Nb(C, N), the solution temperature decrease 30°C than high niobium steel.

Evaluation of Austenite Grains Growth in High Nb and Low Nb HSLA Steel

2020 ◽  
Vol 1000 ◽  
pp. 404-411
Author(s):  
Eddy S. Siradj
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Oil And Gas ◽  
Hsla Steel ◽  
Large Diameter ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Reheating Process ◽  
Austenite Grain Growth

This study was presented due to the increasing demand of High Strength Low Alloy (HSLA) steel, such as demand for thinner-walled and large diameter pipes in oil and gas industries. In order to meet the imposed economic restrictions, the high standard of all kinds of steel properties is required and can be achieved by controlling the steel microstructure. The austenite grain size influences the microstructure and properties of steel significantly, in which fine austenite grain size leads to higher strength, better ductility, and higher toughness. Studying the behavior of steel grain growth during the reheating process is still being a fascinating subject. P.R. Rios and D Zollner [1] mentioned that grain growth is the most important unresolved issue that has been a topic of research for many years. In this research, the behavior of austenite grain growth at a high niobium-low carbon (High Nb-low C) and low Nb-high C HSLA steel was evaluated, and the result was compared with other investigation. The results found that the austenite grain growth at high Nb-high C steel was slower than the growth at a low Nb-low C steel. The activation energy of austenite grain growth and both constant A and exponent n ware determined close agreement was obtained between the prediction of the model and the experimental grain size value.

Nonisothermal Austenite Grain Growth Kinetics in a Microalloyed X80 Linepipe Steel

2010 ◽  
Vol 41 (12) ◽  
pp. 3161-3172 ◽  
Author(s):  
Kumkum Banerjee ◽  
Matthias Militzer ◽  
Michel Perez ◽  
Xiang Wang
Keyword(s):  
Grain Growth ◽  
Growth Kinetics ◽  
Austenite Grain ◽  
Grain Growth Kinetics ◽  
Austenite Grain Growth ◽  
Linepipe Steel
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