| 1. |
- Siwecki, Tadeusz, et al.
(författare)
-
Optimization of Slab Reheating & Processing Temperatures for Flat and Long Products of High Strength Steels
- 2013
-
Rapport (refereegranskat)abstract
- The present work was carried out with the aim of reducing the initial slab reheating temperature before rolling while at the same time improving properties by optimisation of the steel composition and process parameters. Optimisation of slab reheating and hot rolling/cooling parameters in connection with heavy plate, strip and long products rolling has been carried out on a laboratory scale for high strength steels. The investigation has concerned six steels originating from SSAB EMEA (Borlänge and Oxelösund) and OVAKO Bar AB (Smedjebacken). Effects have been investigated of reduced slab reheating temperature (Treh), finish rolling temperature during thermo-mechanical processing (TMCP) and accelerated cooling rates (ACR=20-80°C/s) following hot rolling to the coiling temperature of 550°-600°C or to room temperature (RT). The results obtained for strip steels show also that a reduced reheating temperature (1220°C) combined with a high finish rolling temperatures and cooling rates over 20°C/s to coiling temperatures (Tcoil) of 550°-600°C produce very positive mechanical properties in the present steels. Improvements in the yield strength of heavy plate have been obtained by lowering the slab reheating temperature from 1240°C to 1160°C, especially in combination with high pass reductions of 15% and rapid cooling (~100°C/s) to RT. Yield stress improvement for the long product was obtained by lowering the slab reheating temperature from 1250°C to 1180°C and by increasing the cooling rate up to 5°C/s to RT. The results obtained in laboratory scale have been compared with full scale strips and long products of the present steels processed industrially in a same manner and a good agreement between these results has been observed. Analyses of precipitates (particles size and chemistry) in the specimens after TMCP processing were carried out using transmission electron microscopy. The results agree with expectations from ThermoCalc predictions of precipitate dissolution and show a close relationship with the observed microstructures and properties. Lowering the slab reheat temperature by 60-80°C reduces energy consumption by up to 14000 MWh per year and, as a result, reduces the release of CO2 emissions into the atmosphere by 3 600 tonnes per year during production of the present steels.
|
|
| 2. |
- Fransson, Åsa, 1971, et al.
(författare)
-
Hydromechanical characterization of fractures close to a tunnel opening: A case study
- 2012
-
Ingår i: ISRM International Symposium - EUROCK 2012.
-
Konferensbidrag (refereegranskat)abstract
- Important factors influencing the hydromechanical behavior of a fracture are in situ rock stresses (natural and induced) as well as hydraulic heads, fracture orientation, connectivity and fracture geometry, including their infillings. Particular attention is given to larger, water-conducting fractures that intersect or are close to a tunnel. For the Bentonite Rock Interaction Experiment (BRIE) at the Äspö Hard Rock Laboratory (HRL) in Sweden, the interaction between rock and bentonite in a deposition borehole is of particular interest. The BRIE experiment is being conducted at a depth of 420 meters in crystalline rock. This paper presents results from the initial identification, characterization and modeling of a small number of fractures close to the tunnel opening. So far, these fractures have been identified as the most important water-conducting fractures. In this identification and characterization exercise, core-drilled, vertical, three-meter deep investigation boreholes were made in the tunnel floor. Logging of natural hydraulic heads in boreholes and hydraulic tests, along with borehole and tunnel mapping in combination with modeling, indicate small deformations. This was also confirmed by deformation measurements performed in the boreholes. The description of the site will be further updated and revised and additional investigations into the link between stress history, fracture geometry and selection of fracture mechanical properties will be of particular interest.
|
|
| 3. |
- Hutchinson, Bevis, et al.
(författare)
-
Elasticity and wave velocity in fcc iron (austenite) at elevated temperatures – Experimental verification of ab-initio calculations
- 2018
-
Ingår i: Ultrasonics. - : Elsevier. - 0041-624X .- 1874-9968. ; 87, s. 44-47
-
Tidskriftsartikel (refereegranskat)abstract
- High temperature crystal elasticity constants for face centred cubic austenite are important for interpreting the ultrasonic properties of iron and steels but cannot be determined by normal single crystal methods. Values of these constants have recently been calculated using an ab-initio approach and the present work was carried out to test their applicability using laser-ultrasonic measurements. Steel samples having a known texture were examined at temperatures between 800 °C and 1100 °C to measure the velocity of longitudinal P-waves which were found to be in good agreement with modelled values.
|
|
| 4. |
- Junker, Johan, et al.
(författare)
-
Differentiation of human dermal fibroblasts towards endothelial cells
- 2013
-
Ingår i: Differentiation. - Oxon, United Kingdom : Elsevier. - 0301-4681 .- 1432-0436. ; 85:3, s. 67-77
-
Tidskriftsartikel (refereegranskat)abstract
- The ultimate goal of vascular tissue engineering is the production of functional grafts for clinical use. Difficulties acquiring autologous endothelial cells have motivated the search for alternative cell sources. Differentiation of dermal fibroblasts towards several mesenchymal lineages as well as endothelial cells has been proposed. The aim of the present study was to investigate the endothelial differentiation capacity of human dermal fibroblasts on a gene expression, protein expression and functional physiological level. Endothelial differentiation of fibroblasts was induced by culturing cells in 30% human serum, but not in fetal calf serum. Expression of proteins and genes relevant for endothelial function and differentiation was increased after induction. Furthermore, fibroblasts exposed to 30% human serum displayed increased uptake of low-density lipoprotein and formation of capillary-like networks. The results of this study may have an impact on cell sourcing for vascular tissue engineering, and the development of methods for vascularization of autologous tissue engineered constructs.
|
|
| 5. |
- Komenda, Jacek, et al.
(författare)
-
The effect of boron addition on precipitation and hot ductility of 1.5Mn-0.1Nb-Ti carbon steels in As-cast condition
- 2016
-
Ingår i: Materials Science Forum. - 9783035711295 ; , s. 990-995
-
Konferensbidrag (refereegranskat)abstract
- Twelve experimental steels with a base composition 1.5wt% Mn, 0.01 wt% V and 0.1 wt% Nb and varying C (0.05, 010 and 0.20 wt%), Ti (20 - 260 ppm) and B (0 - 100 ppm) contents have been systematically examined to quantify the effects of composition on precipitation behavio-ur and hot ductility during simulated continuous casting conditions. Nb-rich precipitates were present in the alloys with 0.10 wt-% C and 0.20 wt-% C. Alloys with 0.05, 010 and 0.20wt% C contained 50 - 100 nm size Ti-Nb carbonitrides. Boron was bound in 20 - 100 nm size boronitrides located in prior austenite grain boundaries. A Gleeble 3800 was used to study hot ductility and strain induced precipitation processes in the alloys. Alloys without B and Ti additions exhibited poor hot ductility at 850°C and 950°C, whereas the 0.05 wt-% C and 0.10 wt-% C alloys showed improved hot ductility (reduction in area 40-50%) by the addition of either >50 ppm B or 250 ppm Ti. The 0.2 wt-% C alloys showed no improvement from B or Ti additions. Examination of fracture surfaces of hot ductility specimens showed that boronitrides were located at prior austenite grain boundaries in alloys containing 80 - 100 ppm of B. Compression-relaxation tests showed that alloying with boron caused a noticeable decrease of the start temperature of straininduced precipitation in the alloys.
|
|
| 6. |
- Lönnqvist, Susanna, 1986-, et al.
(författare)
-
Tracking keratinocytes and melanocytes using carboxyfluorescein hydroxysuccinimidyl ester staining
- 2019
-
Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 14:8
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction The treatment of burn wounds and hypopigmentation conditions often require autologous transplantation of keratinocytes and melanocytes. Tracking transplanted cells to ascertain their contribution to tissue recapitulation presents a challenge. This study demonstrates a methodology based on passive staining with carboxyfluorescein hydroxysuccinimidyl ester ( CFSE) that enables localization of cells in tissue sections to investigate the fate of transplanted cells in wound re-epithelialisation. Methods Viability and migration of CFSE-stained keratinocytes and melanocytes were investigated using viability staining and scratch assays, while proliferation of cells was measured using flow cytometry. In addition, CFSE-stained keratinocytes and melanocytes were transplanted to a human ex vivo wound model, either in suspension, or with the aid of macroporous gelatine microcarriers. Wounds were analysed seven, 14 and 21 days post transplantation using cryosectioning and fluorescence microscopy. Sections from wounds with transplanted co-cultured keratinocytes and melanocytes were stained for pancytokeratin to distinguish keratinocytes. Results CFSE-staining of keratinocytes and melanocytes did not affect the viability, migration or proliferation of the cells. Transplanted cells were tracked in ex vivo wounds for 21 days, illustrating that the staining had no effect on wound re-epithelialisation. In conclusion, this study presents a novel application of CFSE-staining for tacking transplanted primary human keratinocytes and melanocytes.
|
|
| 7. |
- Malmström, Mikael, PhD, 1982-, et al.
(författare)
-
In-Situ Grain Size Measurement During Dynamic Recrystallization And Hot Rolling Simulations By Laser Ultrasonics (GLUS®)
- 2024
-
Konferensbidrag (refereegranskat)abstract
- The real-time grain size measurement has recently been realized by laser ultrasonics in the hot-rolling process [1]. This enables quality control, the possibility of direct feedback to the process control system, as well as feedback to the set-up calculation which is performed before each transfer bar is sent through the finishing mill to be rolled. The gauge provides novel insights into how the material behaves during production. This is especially useful for low-alloyed steels that phase transform at cooling to room temperature making it difficult to use traditional metallographic methods to estimate prior austenite grain structure. However, the grain size gauge is currently only installed at one position in the mill, thus, providing measurements at a single point in the process. To better understand how material behaves during the whole process the GLUS® testbed at Swerim, which is the combination of the thermo-mechanical simulator GLEEBLE and laser ultrasonics can be used. The method provides a unique possibility to explore and validate alloying concepts on a smaller scale to increase the understanding of how material properties evolve during for example annealing or hot-rolling processes. In this work, this is demonstrated for an austenitic stainless steel making it possible to confirm LUS measurements with room temperature observations. Thermomechanical simulations are made corresponding to a 6-stand finishing mill, with different deformation strategies reaching the same total deformation. Grain structure is monitored with laser ultrasonics on 316L. In addition, we will present the results from grain size measurement during the deformation showing the capability of GLUS to capture the microstructure evolution such as dynamic recrystallization.References[1] Malmström M, Jansson A, Hutchinson B, Lönnqvist J, Gillgren L, Bäcke L, et al. Laser-Ultrasound-Based Grain Size Gauge for the Hot Strip Mill. Applied Sciences 2022;12:10048. https://doi.org/10.3390/app121910048
|
|
| 8. |
- Malmström, Mikael, 1982-, et al.
(författare)
-
Laser-Ultrasound-Based Grain Size Gauge for the Hot Strip Mill
- 2022
-
Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 12:19
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 9. |
- Nyyssönen, Tuomo, et al.
(författare)
-
Significance of Annealing Twins in Laser Ultrasonic Measurements of Grain Size in High-Strength Low-Alloy Steels
- 2023
-
Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 13:6
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we demonstrate the significance of austenite annealing twin boundaries when calibrating laser ultrasonic measurements for gauging austenite grain size in situ during the thermomechanical processing of high-strength low-alloy steels. Simple calculations show how differences in twinning density can lead to errors in grain size measurements if twins are disregarded during calibration and the method is used for a broad range of steels. Conversely, when calibration is performed using alloys with a metastable austenite microstructure at room temperature, the same calibration is suitable for a broad range of HSLA steels, provided that annealing twins are taken into account. Since light optical microscopy does not allow the characterization of annealing twins in low-alloy steel, the verification of the laser ultrasonic results was conducted using the novel approach of comparing the twinned grain sizes obtained using the ultrasonic method in low-alloy steels with the austenite grain maps reconstructed from martensite orientation maps measured using electron backscatter diffraction. Finally, we show how differences in twinning density occur even for alloys with a roughly similar stacking fault energy, further highlighting the importance of annealing twins in the calibration of laser ultrasonic measurements for industrial use.
|
|
| 10. |
- Rakar, Jonathan, et al.
(författare)
-
Evaluating Multi-Lineage Induction of Human Dermal FibroblastsUsing Gene Expression Analysis
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- During the past decades, several adult stem cell populations from a range of tissues have been characterized. Since principally all human cells contain the same genetic material, the specific gene expression profile determines the cell phenotype. The notion of terminally differentiated somatic cells being necessarily restricted to one phenotype has been challenged, and instead an inherent range of plasticity for any given cell type has been suggested. We have in previous work shown that normal human dermal fibroblasts have an inherent plasticity and can be induced to differentiate towards adipogenic, chondrogenic, endotheliogenic and osteogenic lineages when subjected to defined induction media. The aim of the present study was to further study the differentiation of human dermal fibroblasts on a gene expression level. This was achieved by employing genome wide expression analysis using microarray technology. Selected gene expression was also evaluated over time using real-time PCR. Several master regulatory genes important for lineage commitment, as well as phenotypically relevant genes, were found regulated in the respective induced cultures. The results obtained in this study strengthen previously published results showing an inherent ability for controllable phenotype alteration of human dermal fibroblasts in vitro. We conclude that adipogenic, chondrogenic, endotheliogenic and osteogenic induction results in novel phenotypes that show a genetic readiness for lineage-specific biological functionality.
|
|
