| 195011. |
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| 195012. |
- Steneholm, Karin, et al.
(author)
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Change of inclusion characteristics during vacuum degassing of tool steel
- 2006
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In: Steel Research International. - : Wiley. - 1611-3683. ; 77:6, s. 392-400
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Journal article (peer-reviewed)abstract
- The inclusion characteristics were studied during vacuum degassing by interrupting the operation at five different times after the start of operation. Slag and steel samples were collected and thereafter assessed with respect to steel and slag composition, total oxygen content, size distribution of inclusions and chemical composition of inclusions. The main conclusion is that the number of inclusions in the different size classes as well as the total oxygen content seem to reach a minimum value after around ten minutes of vacuum degassing. Furthermore, it seems to be a consistent trend that, during vacuum degassing, the top slag influences the inclusion composition.
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| 195013. |
- Steneholm, Karin, et al.
(author)
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Effect of top slag composition on inclusion characteristics during vacuum degassing of tool steel
- 2007
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In: Steel Research International. - : Wiley. - 1611-3683. ; 78:7, s. 522-530
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Journal article (peer-reviewed)abstract
- The focus of the study was to investigate the effect of the chemical composition of the top slag on the inclusion chemical composition during vacuum treatment of a plastic mould tool steel. Sampling was done before and after vacuum degassing. The chemical composition of the inclusions was determined by using SEM combined with EDX. The results showed that several inclusion compositions were found before vacuum degassing, while only one main composition of inclusions was present after vacuum degassing. Furthermore, the composition of the top slag was found to have a great influence on the composition of the inclusions found in samples taken after vacuum degassing. The present study also shows that the vacuum degassing effectively reduces the number of inclusions in steel. Finally, the thermodynamic calculations of the activities using Wagner's equation were found to predict a lower oxygen activity value than the calculations made using the Thermo-Calc software.
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| 195014. |
- Steneholm, K., et al.
(author)
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Removal of hydrogen, nitrogen and sulphur from tool steel during vacuum degassing
- 2013
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In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:3, s. 199-205
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Journal article (peer-reviewed)abstract
- The removal of hydrogen, nitrogen and sulphur during vacuum degassing of a tool steel grade was studied. Both slag and steel samples were collected before and after vacuum treatment for 10 heats. From these, the chemical compositions of steel and slag were determined. Thereafter, the removal rates of sulphur, hydrogen and nitrogen were calculated. For sulphur and hydrogen only first order reaction models were considered. However, for nitrogen both first order and second order kinetic models were studied. The results showed that the removal of hydrogen and nitrogen can be described with first order reaction models. However, the removal rate of sulphur follows the equilibrium sulphur content at all stages during the vacuum degassing. It is also clear that after 10 min of degassing the hydrogen and nitrogen removal is more or less finished for the studied steel grade. However, the sulphur refining can still be carried out for longer times to reach lower values.
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| 195015. |
- Steneholm, Karin
(author)
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The Effect of Ladle Treatment on Steel Cleanness in Tool Steels
- 2016
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Doctoral thesis (other academic/artistic)abstract
- The aim of the present work was to get an overview of the steel cleanness in tool steel. Plant trial studies of three steel grades were done with different focuses.Firstly the change of the inclusion characteristics during the vacuum degassing in the ladle was looked upon. The top slag composition was altered and sampling was made before and after vacuum degassing and the results showed that the top slag composition has an effect on the inclusion composition. Thermodynamic calculations indicated that the oxygen activity for the steel/inclusion was twice as large as that of the steel/top slag before vacuum degassing. However, after vacuum degassing the oxygen activity values were close.In order to study the inclusion characteristics during vacuum degassing the process was interrupted at five pre-determined time points for sampling. During vacuum the number of the smaller inclusions was decreased. However, for the larger inclusions (>11.2µm) the number of inclusions had increased. Throughout the degassing process the inclusion composition was found to approach the top slag composition and at the end of the process only one type of inclusion composition was found.The removal of hydrogen, nitrogen and sulphur was studied. Samples were taken before and after vacuum degassing. It was found that the removal kinetics of hydrogen and nitrogen can be described with first-order reactions. When 10 minutes of vacuum degassing have passed, the removal of hydrogen and nitrogen is more or less finished for the studied steel grades.Two steel grades with similar process route and with only a few differences in steel composition were studied. The sum of FeO and MnO was found to be a clear indicator for when reoxidation had taken place. The results from oxygen activity calculations indicate that calculations of oxygen activities with multivalence slag species such as Fe and Cr requires measurements for validations to ensure that reliable results are obtained.
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| 195016. |
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| 195017. |
- Steneholm, Karin, et al.
(author)
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The role of process control on the steel cleanliness
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Other publication (other academic/artistic)abstract
- The possibilities of obtaining a good process control in order to reach a good cleanliness of the steel were studied based on plant trials. Steel and slag samples were taken from two steel grades with a slightly different composition, but with similar processing conditions. Thereafter, the chemical compositions of the steel and slag samples were determined. The results show that the sum of the FeO and MnO was found to be a clear indicator for when reoxidation had taken place. No conclusive indicator was found to predict the extent of slag carry-over from the electric arc furnace. However, most of the variation in deoxidation seem to originate from the accuracy of the slag raking. Steel grades with low amounts of deoxidisers such as C and Si naturally were found to result in higher oxygen contents at the start of deoxidation. Furthermore, calculations of oxygen activities in the steel melt were made and the results were compared to measurements with varying results. Overall, the results indicate that calculation of oxygen activities with multivalence slag species such as Fe and Cr requires additional measurements to obtain accurate results.
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| 195018. |
- Steneholm, K., et al.
(author)
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The role of process control on the steel cleanliness
- 2018
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In: Ironmaking & steelmaking. - : Taylor & Francis. - 0301-9233 .- 1743-2812. ; 45:2, s. 114-124
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Journal article (peer-reviewed)abstract
- The possibilities of obtaining a good process control in order to reach a good cleanliness of the steel were studied based on plant trials. Steel and slag samples were taken from two steel grades with a slightly different composition, but with similar processing conditions. Thereafter, the chemical compositions of the steel and slag samples were determined. The results show that the sum of the FeO and MnO was found to be a clear indicator for when reoxidation had taken place. No conclusive indicator was found to predict the extent of slag carry-over from the electric arc furnace. However, most of the variation in deoxidation seem to originate from the accuracy of the slag raking. Steel grades with low amounts of deoxidisers such as C and Si naturally were found to result in higher oxygen contents at the start of deoxidation. Furthermore, calculations of oxygen activities in the steel melt were made and the results were compared to measurements with varying results. Overall, the results indicate that calculation of oxygen activities with multivalence slag species such as Fe and Cr requires additional measurements to obtain accurate results.
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| 195019. |
- Stenemo, Erik, et al.
(author)
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Prestudy on System Level Impacts of Automation, Electrification and Digitalization for Long-term Transport Analysis and Planning
- 2021
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Reports (other academic/artistic)abstract
- The aim of this prestudy is to investigate how developments within automation, electrification and digitalization (AED) may affect the demand for passenger and freight transport in Sweden in terms of transport activity (ton-kilometers TKM and passenger-kilometers PKM), traffic activity (vehicle kilometers traveled VKT), modal distribution and other characteristics of the transport system, in order to assess whether the current base forecasts for 2040 that are developed and used by Trafikverket are still robust when accounting for developments and impacts of AED. Both freight and passenger transports are considered, as well as several transport modes. These include road (passenger cars, light and heavy trucks), rail (long and short distance), marine (ships and ferries) and air (planes). In addition, support infrastructure such as charging stations and goods terminals are considered. Automation technologies include automated vehicles and goods handling. Electrification refers to the replacement of conventional fuels with electric energy, as well as charging infrastructure. Digitalization is the broadest of the technological fields, and includes both digital services and digital infrastructure. The latter is furthermore an enabler for first and foremost automation, but also for electrification to some extent. The theoretical perspective of the study is that transport demand is derived from the need to transport goods and people. Several drivers of transport demand (such as mode characteristics and economic structure) are presented and included in a general framework for assessing transport demand. The framework further incorporates a variety of previously constructed models and consists of three layers (activities & material flows, transport services and infrastructure) which connect in two markets (the transport and traffic market). The effects on transport demand are assessed from a set of demand parameters, including TKM, PKM and VKT. Finally, six mechanisms through which AED could affect transport demand are presented and integrated into the general framework. Through literature reviews and workshops, a set of general trends within AED were identified. Since there is a considerable uncertainty regarding how these trends could develop until 2040, an explorative scenario-based approach was employed. In order to structure this approach, a morphological analysis was conducted where the identified trends were formulated as parameters and their stages of development as attributes. Combined, these parameters and attributes formed a morphological box which could be used to illustrate different scenarios. In this study, four scenarios were then mapped in the morphological box: a base scenario intended to mimic explicit and implicit assumptions in the base forecast and three alternative scenarios (Partnership Society, Social Engineering 2.0 and Swimming in Data) intended to contrast the base scenario by illustrating alternative societal and technological development paths. These scenarios and their respective morphological box mappings were then analyzed based on the general framework. The first step in this impact analysis consisted of investigating possible separate impacts of the parameters on each layer and market in the general framework. The mechanisms of which each parameter would affect the system were also identified. Examples of effects include changes in generalized costs and service levels. In the second step, the impacts from combined AED development were studied based on the scenario mappings in the morphological box. This highlights possible synergies between the technologies. Finally, the combined effects were compared with the base scenario in order to reach the study’s aim. The results of the analysis show that automation, electrification and digitalization technologies separately could lead to changes in transport efficiency as well costs. Furthermore, synergetic effects leading to even stronger impacts on factors such as these could arise when they are combined. Through the general framework and the demand impact mechanisms, it was shown that factors such as these could lead to changes in the transport demand, modal distribution and transport system characteristics. Since the scenario mapping shows that the base forecasts do not consider development in automation and digitalization to a significant extent, the base forecasts would probably not be robust if these technologies see a continued development and implementation in the transport system.
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| 195020. |
- Stener, Jonas, et al.
(author)
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Dimensionering av korta pålar – pelare eller pålar med sidomotstånd?
- 2023
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In: Bygg och Teknik. - 0281-658X .- 2002-8350. ; :1, s. 20-23
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Journal article (pop. science, debate, etc.)abstract
- Spetsbärande pålar dimensioneras vanligtvis efter den modell för böjknäckning med sidomotstånd med ekvivalent styvhet som redovisas i Pålkommissionens rapporter. För pålar som är kortare än den elastiska knäcklängden är dock förutsättningarna för denna beräkningsmodell inte giltig. Alternativet är då att använda beräkningsmodell för fri pelare som redovisas i Eurokoder. Föreliggande artikeln redovisar resultatet av ett examensarbete på KTH där skillnaden jämförs för beräkningsmodeller som består av standardmodell för böjknäckning med sidomotstånd, beräkning för axialbelastad fri pelare enligt SS-EN 1993–1, och FEM-modell innefattande initialutböjning.
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