scholarly journals Study of Static Recrystallization Kinetics and the Evolution of Austenite Grain Size by Dynamic Recrystallization Refinement of an Eutectoid Steel

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1289
Author(s):  
Cesar Facusseh ◽  
Armando Salinas ◽  
Alfredo Flores ◽  
Gerardo Altamirano
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Static Recrystallization ◽  
Controlled Rolling ◽  
Strain Rates ◽  
Peak Strain ◽  
Compression Tests ◽  
Eutectoid Steel ◽  
Austenite Grain Size ◽  
Austenite Grain

Interrupted and continuous hot compression tests were performed for eutectoid steel over the temperature range of 850 to 1050 °C and while using strain rates of 0.001, 0.01, 0.1, and 1 s−1. The interrupted tests were carried out to characterize the kinetics of static recrystallization(SRX) and determinate the interpass time conditions that are required for initiation and propagation of dynamic recrystallization (DRX), while considering that the material does not contain microalloying elements additions for the recrystallization delay. Continuous testing was used to investigate the evolution of the austenite grain size that results from DRX. The results indicate that carbon content accelerates the SRX rate. This effect was observed when the retardation of recrystallization due to a decrease in deformation temperature from 1050 to 850 °C was only about one order of magnitude. The expected decelerate effect on the SRX rate when the initial grain size increases from 86 to 387 µm was not significant for this material. Although the strain parameter has a strong influence on SRX rate, in contrast to a lesser degree of strain rate, both of the effects are nearly independent of the chemical composition. The calculated maximum interpass times that are compatible with DRCR (Dynamic Recrystallization Controlled Rolling), for relatively low strain rates, suggest that the onset and maintaining of the DRX is possible. However, while using the empirical equations that were developed in the present work to estimate the maximum times for high strain rates, such as those observed in the wire and rod mills, indicate that the DRX start is feasible, but maintaining this mechanism for 5% softening in each pass after peak strain is not possible.

The Dynamic Recrystallization of Hot-Deformed Austenite in a Micro-Alloyed Steel

2012 ◽  
Vol 724 ◽  
pp. 287-290
Author(s):  
Yuan She ◽  
Zhao Hui Zhang ◽  
Jun Yang ◽  
Jian Tao Ju
Keyword(s):  
Dynamic Recrystallization ◽  
Peak Stress ◽  
Controlled Rolling ◽  
Alloyed Steel ◽  
Compression Tests ◽  
Austenite Grain Size ◽  
Alloyed Element ◽  
Deformation Equation ◽  
Dynamic Recrystallization Behavior ◽  
Micro Alloyed Steel

As the dynamic recrystallization (DRX) behavior of hot-deformed austenite is the basis of determining controlled rolling schedule for steel, in the present work, the dynamic recrystallization behavior of austenite of a 0.22%C-1.30%Mn-0.04%Nb micro-alloyed steel was investigated by means of high temperature compression tests on the Thermecmastor-Z simulator. By the analysis of true stress-strain curves at different deformation stages, the hot deformation equation of austenite was established for the steel. As a result, the energy to induce recrystallization of austenite for the steel is 419.1 kJmol-1, as it was influenced by the drag effect of micro-alloyed element Nb in solid solution. The ratio (σc/σp) of critical stress σc (where DRX occurs) to peak stress σp is 0.93 while the ratio (εc/εp) of critical strain εc to peak stress εp is 0.52 for the steel. The austenite grain size of dynamic recrystallization of the micro-alloyed steel is refined by decreasing the deformation temperature and improving the stain rate.

scholarly journals Dynamic Precipitation in Mg–8.08Gd–2.41Sm–0.30Zr Alloy during Hot Compression

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2147
Author(s):  
Limin Zhu ◽  
Quanan Li ◽  
Qing Zhang ◽  
Xiaoya Chen
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Compression ◽  
Strain Rates ◽  
Dynamic Precipitation ◽  
Compression Tests ◽  
Effects Of Temperature ◽  
Compression Temperature

Dynamic precipitation of Mg–8.08Gd–2.41Sm–0.30Zr (wt %) alloy during hot compression was studied in the present work. The effects of temperature and strain rate on dynamic precipitation, and the effects of dynamic precipitation on dynamic recrystallization (DRX) and microhardness, were systematically analyzed. For this purpose, hot compression tests were conducted at the strain rates of 0.002~1 s−1 and temperatures of 350~500 °C, with the compaction strain of 70% (εmax = 0.7). The obtained results revealed that dynamic precipitation occurred during hot compression at 350~400 °C, but did not occur for T ≥ 450 °C. The precipitates were demonstrated to be β-Mg5Gd with a size of 200~400 nm, and they were distributed in the DRXed region. Dynamic precipitation occurred at strain rates in the 0.002~0.01 s−1 range, but did not occur when the strain rates were in the 0.1~1 s−1 range for the hot compression temperature of 350 °C. The relationships between the hot compression temperature (T) and DRXed grain size (lnd), microhardness (Hv), and DRXed grain size (d−1/2) of Mg–8.08Gd–2.41Sm–0.30Zr alloy were obtained.

Development and Industrial Applying on Rolling Mill 5000 of the Model of Austenite Grain Size Evolution in Nb-Microalloyed Steels

2016 ◽  
Vol 879 ◽  
pp. 312-317
Author(s):  
A.V. Chastukhin ◽  
D.A. Ringinen ◽  
S.V. Golovin ◽  
L.I. Efron
Keyword(s):  
Grain Size ◽  
Rolling Mill ◽  
Microalloyed Steels ◽  
Compression Tests ◽  
Austenite Grain Size ◽  
Soaking Time ◽  
Austenite Grain ◽  
Size Evolution ◽  
South Stream ◽  
Rolled Plates

In this research evolution of austenite grain size in Nb-microalloyed steels X65÷X120 grades during slab reheating and roughing rolling was studied. A mathematical model has been development to obtain the target temperature and soaking time in furnace, which ensure a uniform austenite structure and maximum possible dissolution of the carbonitride particles prior to roughing rolling. The Hot Rolling Recrystallization Model (HRRM) has also development to predict the austenite microstructure evolution during roughing rolling. The model is based on empirical equations and organized following a tree-structure. A validation of the model has been carried out in the laboratory by multipass compression tests. The models jointly have been used to create new strategies of processing technology of rolled plates on rolling mill 5000 for the South Stream pipeline. The industrial application has confirmed a great benefit of the models in point of cold resistance of rolled plates.

The Influence of Increased Cr Content and Austenite Grain Size on the Kinetics of Phase Transformations when Cooling Hypo-Eutectoid Steel

2006 ◽  
Vol 258-260 ◽  
pp. 421-426
Author(s):  
Ignacy Wierszyłłowski
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Carbon Steel ◽  
Phase Transformations ◽  
Austenite Phase ◽  
Eutectoid Steel ◽  
Austenite Grain Size ◽  
Cr Content ◽  
Austenite Grain ◽  
Kinetics Of

The paper presents the influence of the grain size and a little higher Cr content on the kinetics of austenite phase transformations during continuous cooling of hypo-eutectoid steel. The kinetics of austenite phase transformations during continuous cooling were determined by means of analysis of the dilatometric curves and structure investigations. The influence of the austenite grain size and the higher Cr content was analysed in two hypoeutectoid steels containing about 0.4% C. One of them had, Cr content higher, by about 1%. In both steels, the austenite grain size was changing insignificantly up to the austenitising temperature of about 950fl. Above that temperature, the austenite grain size in carbon steel grew much quicker than that in the steel with Cr addition. The austenite grain in the Cr enriched steel was smaller than that in carbon steel and, in spite of that, the duration of cooled austenite transformations were several times longer. This means that the phase transformations are much more strongly influenced by the addition of chromium slowing down carbon diffusion in austenite, than by the austenite grain size. For each phase transformation in the examined steels, the activation energy of the transformation has been determined. The activation energy of all the phase transformations varied slightly with the increase of austenitising temperature. On the basis of the obtained results, curves of true isothermal transformations have been developed for the beginning of the phase transformations in both steels, related to infinitely quick cooling down to the transformation temperature.

Microstructural Aspects of Recrystallization-Controlled Rolling in V-Ti-N Steels

1985 ◽  
Vol 43 ◽  
pp. 334-335
Author(s):  
M.G. Burke ◽  
R.M. Fix ◽  
A.J. DeArdo
Keyword(s):  
Grain Size ◽  
Cooling Rate ◽  
Steel Industry ◽  
Room Temperature ◽  
Controlled Rolling ◽  
Accelerated Cooling ◽  
Air Cooling ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Processing Treatment

Recrystallization controlled rolling (RCR) has been developed as an economically viable alternative to conventional controlled rolling, a thermomechanica1 processing treatment currently employed in the steel industry. RCR processing involves deformation below the austenite grain coarsening temperature of the steel, followed by accelerated cooling to an intermediate temperature and air cooling to room temperature. The V-Ti-N system is well-suited to RCR processing because Ti (in the form of TiN precipitates) promotes a fine reheated austenite grain size while the V in solution in the austenite will be available for subsequent precipitation in the ferrite. The precipitation potential of V-Ti steels has been shown to increase with increasing N content and cooling rate.

Study on Recrystallization Behavior of High Strength Automobile Steel Sheets Produced by CSP

2005 ◽  
Vol 475-479 ◽  
pp. 153-156
Author(s):  
Zheng Zhi Zhao ◽  
Yong Lin Kang ◽  
Xin Ping Mao ◽  
Yin Li Chen ◽  
Gui Jiang Chen ◽  
...  
Keyword(s):  
Grain Size ◽  
Deformation Temperature ◽  
High Strength ◽  
Controlled Rolling ◽  
Recrystallization Behavior ◽  
Controlled Cooling ◽  
Austenite Grain Size ◽  
Steel Sheets ◽  
Austenite Grain ◽  
Automobile Steel

The recrystallization behavior of high strength automobile steel sheets (ZJ590L) developed by CSP technology is studied in this paper. The effect of the deformation temperature, reduction on the austenite grain size and the recrystallized fraction of ZJ590L steel during hot deformation has been investigated. Technique of test and analysis includes preparing stepped test piece and quantitative metallograph. The mechanism of austenite microstructure refinement has been discussed, which provides valuable references to set parameters of controlled rolling and controlled cooling process. The analysis shows that the austenite grain size fines with the increase of deformation temperature and reduction, and the recrystallized fraction increases. When the deformation temperature is above 1000°C and reduction exceeds 40%, complete recrystallization can be obtained.

The effects of temperature and strain rate on the hot deformation behavior of AISI H10 tool steel

2020 ◽  
Vol 118 (1) ◽  
pp. 107
Author(s):  
Maryam Kamali Ardakani ◽  
Maryam Morakabati
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Tool Steel ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Strain Rates ◽  
Compression Tests ◽  
Hot Deformation Behavior ◽  
Temperature Range

The hot deformation behavior of a H10 hot work tool steel was studied by performing hot compression tests over the temperature range of 900 to 1200 °C and strain rates of 0.001–1 s−1 and total strain of 0.7. At temperatures below 1100 °C, the grain size is fine and below 20 μm. In this temperature range, grain size increase with temperature due to dissolution of carbides. Then by increasing temperature to 1150 and 1200 °C, the grain size is increased significantly due to growth of grains. The study on the effect of strain rate showed that at constant temperature of 1000 °C, the grain size increased from 4.8 to 6 μm with increasing strain rate from 0.001 to 1 s−1. Also, this increase in the strain rate at temperature of 1100 °C lead to increase the grain size from 5.9 to 17 μm, due to the occurrence of dynamic recrystallization. At 1200 °C growth of grains causes to decrease grain size from 112 to 87 μm by increasing strain rate. According to the microstructural investigations, at the temperatures of 1000 and 1100 °C and strain rates of 0.01 and 0.1 s−1 dynamic recrystallization was the main softening mechanism. As a result, the most suitable range for hot deformation was obtained at the temperature range of 1000–1100 °C and strain rates of 0.01–0.1 s−1.

Static Recrystallization Behavior of a Nitrogen Controlled Z2CN19-10 Austenitic Stainless Steel

2017 ◽  
Author(s):  
Min Luo ◽  
Chun Xu ◽  
Bing Zhou ◽  
Yan-hui Guo ◽  
Rong-bin Li
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Static Recrystallization ◽  
Volume Fraction ◽  
Experimental Results ◽  
Strain Rates ◽  
Recrystallization Behavior ◽  
Hot Workability ◽  
Compression Tests

In order to increase the hot workability and provide proper hot forming parameters for nitrogen controlled Z2CN19-10 austenitic stainless steel, the static recrystallization behavior was investigated by double-pass hot compression tests in the temperature range of 950–1100°C, initial grain size of 72μm–152μm, and the strain rates of 0.01, 0.1, 1, and 5 s−1. The tests were conducted with inter-pass times varying between 1 and 100 s after achieving a pass strain of 0.05, 0.1, 0.15 and 0.2 in the first pass on a Gleeble-1500 thermo-mechanical simulator. The static recrystallization fraction has been predicted by the 2 % offset stress method and verified by metallographic observations. The metallographic results indicate the crystallized grains generate at the cross of the prior austenite grain boundary and grow up. Also the kinetics of static recrystallization behavior for Z2CN19-10 steel are proposed. Experimental results show that the volume fraction of static recrystallization increases with the increase of deformation temperature, strain rates, pass strain and interval time, while it decreases with the increase of initial grain size. According to the present experimental results, the activation energy (Q) and Avrami exponent (n) was determined as 199.02kJ/mol and 0.69. The established equations can give a reasonable estimate of the static recrystallization behavior for Z2CN19-10 steel.

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