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.

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.

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

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.

scholarly journals Study of the Microstructure and Strain Induced Precipitation during Thermomechanical Processing of Low Carbon Microalloyed Steels

2012 ◽  
Vol 706-709 ◽  
pp. 2118-2123
Author(s):  
Manuel Gómez ◽  
Pilar Valles ◽  
Sebastián F. Medina
Keyword(s):  
Hot Rolling ◽  
Thermomechanical Processing ◽  
High Strength ◽  
Transformation Products ◽  
Carbon Steels ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Mean Flow ◽  
Wide Range ◽  
Final Microstructure

A series of anisothermal multipass hot torsion tests were carried out to simulate hot rolling on three high-strength low-carbon steels with different amounts of Mn, Mo, Nb and Ti and designed for pipeline construction. Mean Flow Stress was graphically represented against the inverse of temperature to characterize the evolution of austenite microstructure during rolling. The effect of austenite strengthening obtained at the end of thermomechanical processing on the final microstructure obtained after cooling was studied. Higher levels of austenite strengthening before cooling promote a refinement of final microstructure but can also restrict the fraction of low-temperature transformation products such as acicular ferrite. This combined effect gives rise to a wide range of final microstructures and mechanical properties depending on the composition, processing schedule and cooling rates applied. On the other hand, the precipitation state obtained at diverse temperatures during and at the end of hot rolling schedule was evaluated by means of transmission electron microscopy (TEM) in two microalloyed steels. It was found that two families of precipitates with different morphology, composition and mean size can coexist in microalloyed steels.

Challenges of Nb Application in Thermomechanical Processes of Steels for Long Products

2018 ◽  
Vol 941 ◽  
pp. 386-393
Author(s):  
Beatriz López ◽  
Beatriz Pereda ◽  
Felipe Bastos ◽  
Marcelo Rebellato ◽  
J.M. Rodriguez-Ibabe
Keyword(s):  
Hot Rolling ◽  
Carbon Steels ◽  
Microalloyed Steels ◽  
Chemical Compositions ◽  
Low Carbon ◽  
High Carbon ◽  
Wide Range ◽  
Nb Microalloying ◽  
Thermomechanical Processes ◽  
Rolling Heat

Nb is a classical microalloying element in the design of thermomechanical treatments in low carbon steels for flat products applications. However, its use in medium-high carbon grades, as occurs in hot rolling of bars, is less common. This is, in part, because of the diversity of characteristics required to those grades of steels and the less knowledge about the function of Nb in these cases. Consequently, less information is reported concerning thermo-mechanical processing of Nb microalloyed steels in long products applications. In this case, it is necessary to consider the singularities related to these processes, such as the short interpass times and the wide range of chemical compositions usually applied on these products. Short interpass times result in high strain rate values that can lead to metallurgical changes on the mechanisms occurring during the hot rolling must be considered. Moreover, the high Carbon contents applied in long products, usually between 0.20–0.40%, can influence the Nb solubility and precipitation in each stage of the process: prior to hot rolling on the reheating furnace, during the process and after hot rolling, depending on the cooling strategy adopted and on the post-rolling heat treatments that can be applied. This paper analyses different singularities associated with the use of Nb microalloying for long products. Several aspects, such as the partial or complete dissolution of the Nb prior to hot rolling, its role in the control of austenite microstructure and its incidence in the final microstructure and mechanical properties, will be considered.

Factors Limiting the Achievable Ferrite Grain Refinement in Hot Worked Microalloyed Steels

2005 ◽  
Vol 500-501 ◽  
pp. 355-362 ◽  
Author(s):  
E. Novillo ◽  
E. Cotrina ◽  
Amaia Iza-Mendia ◽  
Beatriz López ◽  
Isabel Gutiérrez
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Hot Rolling ◽  
Rolling Mill ◽  
Solute Drag ◽  
Microalloyed Steels ◽  
Rolling Mills ◽  
Hot Rolling Mill ◽  
Conventional Rolling ◽  
Ferrite Grain Size

Nb is added to C-Mn steels in order to use the solute drag and/or strain induced precipitation as a useful tool to condition the austenite in the hot rolling mill and produce during the subsequent cooling a refined ferrite grain size. The highest degree of refinement is obtained in conventional rolling mills by accumulating the deformation in austenite during the last passes, followed by early cooling in the run out table to produce a high density of nucleated ferrite grains. However, the maximum refinement is to a certain extent attenuated due to the ferrite grain coarsening taking place during the transformation. The present work analyses the different aspects limiting the final achievable ferrite grain refinement.

New Phenomenological Model of Hot Mean Flow Stress

2013 ◽  
Vol 32 (2) ◽  
pp. 133-138
Author(s):  
Ivo Schindler ◽  
Petr Kawulok ◽  
Stanislav Rusz ◽  
Jiří Plura ◽  
Zdeňek Vašek ◽  
...  
Keyword(s):  
Flow Stress ◽  
Hot Rolling ◽  
Effective Strain ◽  
Single Equation ◽  
Mean Flow ◽  
Strain And Strain Rate ◽  
Wide Range ◽  
Mean Flow Stress ◽  
Experimental Values ◽  
Fast Prediction

AbstractBased on the measurement of roll forces during the laboratory hot rolling of flat samples graded in thickness, the new phenomenological type of mean flow stress model was developed and applied on plain-carbon and HSLA steels. The obtained models describe with a very good accuracy the hot deformation resistance characteristics in the temperature range 1123 to 1463 K, large effective strain, and strain rate in the useful range of approximately 10 to 100 s−1. Difficulty in the mathematical description of the influence of temperature on mean flow stress in the wide range of temperature by a single equation was solved by introducing another constant in the temperature member of the conventional model. The newly proposed model solves by phenomenological means a frequent problem of heteroscedasticity of relative deviations between the calculated and experimental values of mean flow stress values depending on temperature. It becomes more reliable from the viewpoint of the operational application, e.g. fast prediction of mean flow stress values and power/force parameters necessary in the steering systems of hot rolling mills.

Occupational and Environmental Health

2017 ◽  
Keyword(s):  
Public Health ◽  
Occupational Health ◽  
Environmental Health ◽  
Health And Safety ◽  
Practical Experience ◽  
Global Perspective ◽  
Clear Understanding ◽  
Practical Case ◽  
Environmental Sciences ◽  
Wide Range

This thoroughly updated seventh edition is a comprehensive, clearly written, and practical textbook that includes information on both occupational health and environmental health, providing the necessary foundation for recognizing and preventing work-related and environmentally induced diseases and injuries. National and international experts share their knowledge and practical experience in addressing a wide range of issues and evolving challenges in their fields. A multidisciplinary approach makes this an ideal textbook for students and practitioners in public health, occupational and environmental medicine, occupational health nursing, epidemiology, toxicology, occupational and environmental hygiene, safety, ergonomics, environmental sciences, and other fields. Comprehensive coverage provides a clear understanding of occupational and environmental health and its relationships to public health, environmental sciences, and government policy. Practical case studies demonstrate how to apply the basic principles of occupational and environmental health to real-world challenges. Numerous tables, graphs, and photographs reinforce key concepts. Annotated Further Reading sections at the end of chapters provide avenues for obtaining further infomation. This new edition of the book is thoroughly updated and also contains new chapters on climate change, children’s environmental health, liver disorders, kidney disorders, and a global perspective on occupational health and safety.

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