Grain Size Modeling during Hot Rolling of a Nb Microalloyed Steel Beam

2013 ◽  
Vol 753 ◽  
pp. 397-402
Author(s):  
Emanuelle Garcia Reis ◽  
Ronaldo Barbosa
Keyword(s):  
Grain Size ◽  
Hot Rolling ◽  
Microalloyed Steels ◽  
Strain Rates ◽  
Rolling Schedule ◽  
Austenite Grain Size ◽  
Beneficial Effects ◽  
Size Evolution ◽  
Nb Microalloyed Steel ◽  
Two Stages

Hot rolling of beams is carried out essentially in two stages. Roughing is performed in a reversing mill at temperatures in the range of 1100 oC, at relatively low strain rates and with long interpass times. Finishing is carried out in a reversing two stand mill at temperatures in between 1000 and as low as 700 oC considering parts of the web in the last passes. Strain rates are moderate and interpass times are in the range of 5 to 20s. There is, therefore, as it can be seen from the description just made of the rolling schedule, a fair resemblance to deformation in plate mills. Technology for themomechanical processing, TMP, of plates is very well known and disseminated. Application of this technology to beam rolling is, on the other hand, rather seldom known of. This paper addresses an application of TMP plate technology to beam rolling. In particular, austenite grain size evolution is examined. The usage of Nb microalloyed steels to this process is discussed in terms of possible beneficial effects to ferrite grain refinement.

The Influence of Initial Grain Size and Strain Sequence of Slab Hot Rolling on the Austenite Evolution of Peritectic Microalloyed Plate Steels

2014 ◽  
Vol 1019 ◽  
pp. 339-346 ◽  
Author(s):  
Rorisang Maubane ◽  
Kevin Banks ◽  
Waldo Stumpf ◽  
Charles Siyasiya ◽  
Alison Tuling
Keyword(s):  
Grain Size ◽  
Hot Rolling ◽  
Plain Carbon Steel ◽  
Microalloyed Steels ◽  
Heating Rates ◽  
Austenite Grain Size ◽  
Soaking Time ◽  
Austenite Grain ◽  
Dynamic Recrystallisation ◽  
Temperature Constant

The influence of the strain sequence during slab hot rolling (also known as “roughing”) on the evolution of austenite in plain carbon, C-Mn-V and C-Mn-Nb-Ti-V steels was investigated. Reheating and roughing simulations were conducted in a Bähr deformation dilatometer using a constant austenitising temperature, constant soaking time and various heating rates and roughing strain sequences. Stress analysis was used to quantify the austenite softening behaviour and the prior austenite grain size was measured from quenched specimens. The austenite grains of the plain carbon steel were coarser than those of both microalloyed steels, with the C-Mn-Nb-Ti-V grade being the finest due to effective pinning of the grain boundaries. Pass strains greater than 0.2 were sufficient for initiation of dynamic recrystallisation (DRX) for the C-Mn and C-Mn-V steels and led to uniform austenite microstructure with austenite grain sizes less than 40µm after the roughing stage.

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.

An Integrated Model for Rolling Schedule Design of Microalloyed Steels

2018 ◽  
Vol 941 ◽  
pp. 77-82
Author(s):  
Zhan Li Guo ◽  
Nigel Saunders ◽  
Jean Philippe Schillé
Keyword(s):  
Grain Size ◽  
Hot Rolling ◽  
Effective Strain ◽  
Deformation Resistance ◽  
Precipitate Size ◽  
Microalloyed Steels ◽  
Clear Understanding ◽  
Austenite Decomposition ◽  
Rolling Schedule ◽  
Wide Range

Processing parameters have direct impacts on the quality of the steels produced. This is particularly true for microalloyed steels, the production of which involves a thermomechanical controlled rolling process, which combines multi-pass hot rolling with accelerated cooling. On one hand, hot rolling may finish below A3temperature when austenite starts to transform to ferrite. On the other hand, controlled cooling is applied to obtain the desired microstructure from austenite decomposition. To optimise the TMCP parameters of such alloys, not only a clear understanding of each metallurgical phenomenon involved is required, but also the interactions among them. This paper reports our recent work on modelling of microstructural evolution and deformation resistance during multi-pass hot rolling of steels. The model considers the following metallurgical phenomena as well as their interactions: - Precipitation of MX type carbides, nitrides or carbonitrides. - Interactions between precipitation and recrystallisation and their effects on grain refinement. - Effect of grain size and cooling path on transformations from austenite to ferrite, pearlite, bainite and martensite. - Effect of rolling parameters, recrystallisation and microstructure on the deformation resistance of the alloy. The model predicts the evolution of microstructural features such as precipitate size and amount, recrystallisation fraction and effective strain, grain size, and austenite decomposition, as well as the alloy’s deformation resistance during hot rolling. It has been applied to a wide range of steels and demonstrated good agreement with experimental observations. Therefore, it has the great potential to be implemented in a production line to help optimise the rolling schedule for both C-Mn and microalloyed steels.

scholarly journals Grain Size Evolution and Mechanical Properties of Nb, V–Nb, and Ti–Nb Boron Type S1100QL Steels

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 492
Author(s):  
Jan Foder ◽  
Jaka Burja ◽  
Grega Klančnik
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Hot Forging ◽  
Size Control ◽  
High Strength ◽  
Fatigue Properties ◽  
Titanium Addition ◽  
Austenite Grain Size ◽  
Size Evolution

Titanium additions are often used for boron factor and primary austenite grain size control in boron high- and ultra-high-strength alloys. Due to the risk of formation of coarse TiN during solidification the addition of titanium is limited in respect to nitrogen. The risk of coarse nitrides working as non-metallic inclusions formed in the last solidification front can degrade fatigue properties and weldability of the final product. In the presented study three microalloying systems with minor additions were tested, two without any titanium addition, to evaluate grain size evolution and mechanical properties with pre-defined as-cast, hot forging, hot rolling, and off-line heat-treatment strategy to meet demands for S1100QL steel. Microstructure evolution from hot-forged to final martensitic microstructure was observed, continuous cooling transformation diagrams of non-deformed austenite were constructed for off-line heat treatment, and the mechanical properties of Nb and V–Nb were compared to Ti–Nb microalloying system with a limited titanium addition. Using the parameters in the laboratory environment all three micro-alloying systems can provide needed mechanical properties, especially the Ti–Nb system can be successfully replaced with V–Nb having the highest response in tensile properties and still obtaining satisfying toughness of 27 J at –40 °C using Charpy V-notch samples.

scholarly journals Simplification of Hot Rolling Schedule in Ti-Microalloyed Steels with Optimised Ti/N Ratio

2010 ◽  
Vol 50 (6) ◽  
pp. 868-874 ◽  
Author(s):  
Manuel Gómez ◽  
Lucía Rancel ◽  
Pedro P. Gómez ◽  
José I. Robla ◽  
Sebastián F. Medina
Keyword(s):  
Hot Rolling ◽  
Microalloyed Steels ◽  
Rolling Schedule

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.

Microstructure Modeling of the Ribbed Steel Bar Hot Rolling of V-Microalloyed Steel

2010 ◽  
Vol 168-170 ◽  
pp. 599-602
Author(s):  
Lei Yang ◽  
Yi Zhu He ◽  
Xiao Min Yuan
Keyword(s):  
Grain Size ◽  
Hot Rolling ◽  
Integrated Model ◽  
Analytical Models ◽  
Austenite Grain Size ◽  
Microstructure Modeling ◽  
Austenite Grain ◽  
Steel Bar ◽  
Rod Rolling ◽  
Strain Model

This paper proposes an integrated model for the prediction of the pass-by-pass evolution of the austenite grain size of the ribbed steel bar hot rolling. The integrated model consists of a strain model, a temperature model, a microstructure evolution model of austenite grain size and a flow stress model. Hot rod rolling experiments are conducted to examine the proposed analytical models. The integrated model is employed to examine the effects of modifications of the refined austenite grain size of the 500MPa ribbed steel bar. Refinement of ferrite could be realized by refining the austenite grain size at the final pass.

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