Ljusa svenskar och mörka blattar : gymnasiestudenters tankar kring svenskar, invandrare och integration

Sverige är ett mångkulturellt land och det finns intentioner till integration i samhället och dess olika instanser. Skolan är en instans där barn, ungdomar och vuxna med olika bakgrund möts. Studenter med svensk bakgrund och studenter med utländsk bakgrund agerar inom skolan och det sker en kategorisering av studenterna i kategorierna svenskar och invandrare. Syftet med studien är att lyfta fram och tolka gymnasiestudenters tankar kring begreppen svenskar, invandrare och integration. Ett delsyfte är att genomföra en prövning av flödesskrivning som metod. Studien riktar sig till studenter i tredje året på gymnasiet i en kommun i Sverige. Resultatet av studien har visat att flödesskrivning lämpar sig väl som metod och därigenom har tankar lyfts fram kring begreppen. Tankar kring begreppet svenskar rör främst det ljusa som; vit, blond, och vänlighet. Tankar kring begreppet invandrare rör främst det mörka som; svart, bråk och kriminalitet. Tankar kring begreppet integration rör främst bråk och missförstånd och upplevs i stor utsträckning svårt. Ett krav för integration är positiva möten i tidig ålder mellan personer med svensk bakgrund och personer med utländsk bakgrund

Modeling the Microstructural Evolution during Hot Deformation of Microalloyed Steels

  This thesis contains the development of a physically-based model describing the microstructural evolution during hot deformation of microalloyed steels. The work is mainly focused on the recrystallization kinetics. During hot rolling, the repeated deformation and recrystallization provides progressively refined recrystallized grains. Also, recrystallization enables the material to be deformed more easily and knowledge of the recrystallization kinetics is important in order to predict the required roll forces. Hot strip rolling is generally conducted in a reversing roughing mill followed by a continuous finishing mill. During rolling in the roughing mill the temperature is high and complete recrystallization should occur between passes. In the finishing mill the temperature is lower which means slower recrystallization kinetics and partial or no recrystallization often occurs. If microalloying elements such as Nb, Ti or V are present, the recrystallization can be further retarded by either solute drag or particle pinning. When recrystallization is completely retarded and strain is accumulated between passes, the austenite grains will be severely deformed, i.e. pancaking occurs. Pancaking of the grains provides larger amount of nucleation sites for ferrite grains upon transformation and hence a finer ferrite grain size is achieved. In this work a physically-based model has been used to describe the microstructural evolution of austenite. The model is built-up by several sub-models describing dislocation density evolution, recrystallization, grain growth and precipitation. It is based on dislocation density theory where the generated dislocations during deformation provide the driving force for recrystallization. In the model, subgrains act as nuclei for recrystallization and the condition for recrystallization to start is that the subgrains reach a critical size and configuration. The retarding effect due to elements in solution and as precipitated particles is accounted for in the model. To verify and validate the model axisymmetric compression tests combined with relaxation were modeled and the results were compared with experimental data. The precipitation sub-model was verified by the use of literature data. In addition, rolling in the hot strip mill was modeled using process data from the hot strip mill at SSAB Strip Products Division. The materials investigated were plain C-Mn steels and Nb microalloyed steels. The results from the model show good agreement with measured data.  QC 2010070

Modeling the Microstructural Evolution during Hot Deformation of Microalloyed Steels

  This thesis contains the development of a physically-based model describing the microstructural evolution during hot deformation of microalloyed steels. The work is mainly focused on the recrystallization kinetics. During hot rolling, the repeated deformation and recrystallization provides progressively refined recrystallized grains. Also, recrystallization enables the material to be deformed more easily and knowledge of the recrystallization kinetics is important in order to predict the required roll forces. Hot strip rolling is generally conducted in a reversing roughing mill followed by a continuous finishing mill. During rolling in the roughing mill the temperature is high and complete recrystallization should occur between passes. In the finishing mill the temperature is lower which means slower recrystallization kinetics and partial or no recrystallization often occurs. If microalloying elements such as Nb, Ti or V are present, the recrystallization can be further retarded by either solute drag or particle pinning. When recrystallization is completely retarded and strain is accumulated between passes, the austenite grains will be severely deformed, i.e. pancaking occurs. Pancaking of the grains provides larger amount of nucleation sites for ferrite grains upon transformation and hence a finer ferrite grain size is achieved. In this work a physically-based model has been used to describe the microstructural evolution of austenite. The model is built-up by several sub-models describing dislocation density evolution, recrystallization, grain growth and precipitation. It is based on dislocation density theory where the generated dislocations during deformation provide the driving force for recrystallization. In the model, subgrains act as nuclei for recrystallization and the condition for recrystallization to start is that the subgrains reach a critical size and configuration. The retarding effect due to elements in solution and as precipitated particles is accounted for in the model. To verify and validate the model axisymmetric compression tests combined with relaxation were modeled and the results were compared with experimental data. The precipitation sub-model was verified by the use of literature data. In addition, rolling in the hot strip mill was modeled using process data from the hot strip mill at SSAB Strip Products Division. The materials investigated were plain C-Mn steels and Nb microalloyed steels. The results from the model show good agreement with measured data.  QC 2010070

Laser ultrasonics for online monitoring of microstructures in the hot strip mill

QC 20231030</p

Laser-Ultrasound-Based Grain Size Gauge for the Hot Strip Mill

The paper summarizes the creation of a robust online grain size gauge for a hot strip mill. A method and algorithm for calculating the grain size from the measured ultrasonic attenuation is presented. This new method is self-calibrating, does not rely on a geometrical reference sample and can cope with the effects of diffraction on the attenuation. The model is based on 52 quenched samples measured with more than 23,000 laser ultrasonics shots and has a correlation coefficient R2 of 0.8. Typical online laser ultrasonic measurements from the hot strip mill and the calculated grain size versus length are presented for a couple of steel strips

Laser ultrasonics for online monitoring of microstructures in the hot strip mill

QC 20231030</p