By partly replacing the use of primary energy sources with waste heat recovery, climate and environmental goals for the future will be closer at hand. This thesis investigates the waste heat potential of Alfa Laval’s vacuum brazing furnaces in Ronneby and alternative ways of integrating the furnace’s waste heat into the building’s HVAC system. The main challenge was the low-temperature qualities associated with the cooling water, which constituted an obstacle to recovering waste heat without any additional equipment, such as a heat pump. Tests and analyses performed in this thesis are, therefore, mainly aimed at raising the temperature quality of the cooling water. A test was conducted on the cooling system to calculate the energy losses with regards to the cooling water. In one 11-hour cycle, 1546 kWh of electricity was used to heat the furnace. Out of that, 1360 kWh was cooled off to the atmosphere. Additionally, a test on the furnace’s clean-up cycle was performed. The maximum cooling water temperature reached during this test was 44 C. This shows excellent potential in the possibility of recovering the waste heat without any additional equipment. Further, this thesis aims to broaden the knowledge around areas concerning increased cooling water temperatures, which, during the writing, seemed to have a gap in documented sources. The results of this thesis indicate that a temperature quality increase of the furnaces’ cooling water is possible. Cooling system changes have also been suggested, which is necessary for an efficient and safe heat recovery.

This master´s thesis deals with theoretical study of decarburization of austenitic steels. Mathematical model, which analyse numerical calculations, was compared with experiments. Obtained results were discussed considering validity of model and performed aproximations.

Heat transfer during metal pouring and its solidification in the vacuum furnace have been investigated by experiments using model set of castings of different diameters and insulations. The pouring metal was Inconel 713LC alloy based on nickel. The found data have been used for optimization of the numerical simulation of the thermal regime during the both pouring and solidification phases of the process in vacuum. Numerical simulation of the alloy structure in individual castings has been made by the CAFE module of the ProCast software and obtained results compared with the real structure. The optimized boundary conditions can be used for simulation of real castings.

Research on bainite and martensite structures has indicated that lower bainite needles have a refining effect on the lath martensitic structure. Lower bainte needles partitions prior austenite grains and will consequently have a refining effect on the subsequent formed lath martensite. Smaller austenite grains will result in smaller lath martensitic packets and blocks and will result in enhanced mechanical properties.   In order to create a variation of lower bainte structure in a matrix of martensite, two different heat treating methods were tested. The work was focused towards the formation of lower bainite during isothermal heat treating in molten salt, above and below the MS-temperature. Both un-tempered and tempered samples were analyzed .Two different materials were tested, both were AISI 4140 but with a slightly difference in hardenability. The material provided by Ovako Steel is 326C and 326F the later had a higher hardenability. In order to better distinguish the two structures from each other when studied under a microscope, a variation of etching methods were tested.  It was possible to create a variation of lower bainite structures in a matrix of martensite.  326F shows less amount of lower bainite and provides a higher average surface hardness before tempering.

In Gasturbinenbrennern kommen Nickelbasiswerkstoffe für thermisch hoch belastete Komponenten standardmäßig zum Einsatz. Die Bauteile liegen strömungstechnisch vor der stattfindenden Verbrennung, wodurch es zu einer stark einseitigen thermischen Belastung kommt. Ein wirtschaftlich effizienter Einsatz von Nickelbasiswerkstoffen kann daher in Kombination mit kostengünstigen warmfesten Stählen für die weniger stark thermisch belasteten Bauteilbereiche erreicht werden. Ziel der vorliegenden Arbeit ist die Prozessentwicklung zum Hochtemperaturlöten von im Brennerbau häufig verwendeten Nickelbasislegierungen und dem niedriglegierten warmfesten Stahl 16Mo3 (1.5415). Im Entwicklungsprozess wurden die Mikrostruktur der Verbunde charakterisiert, die Auswirkungen thermischer Ausdehnungsunterschiede evaluiert und die erreichbare Festigkeit erfasst. An einem Demonstrator wurden die Erkenntnisse im Rahmen der industriellen Fertigung getestet.:1 Einführung 1.1 Einleitung und Motivation 1.2 Stand von Wissenschaft und Technik 1.3 Schlussfolgerungen und Zielsetzung 2 Technologische Grundlagen 2.1 Der Hochtemperaturlötprozess 2.2 Thermische Ausdehnung 2.3 Diffusion 2.4 Metallurgische Prozesse 3 Experimentelle Durchführung 3.1 Grund- und Lotwerkstoffe 3.2 Lötprozesse und Probengeometrien 3.3 Mikrostrukturelle, thermische und mechanische Charakterisierung 4 Ergebnisse und Diskussion 4.1 Mikrostrukturcharakterisierung 4.1.1 Grundwerkstoffe 4.1.2 Lötsystem 16Mo3 – INCONEL 625 4.1.3 Lötsystem 16Mo3 – Nimonic 75 4.1.4 Lötsystem 16Mo3 – Hastelloy X 4.1.5 Lötsystem 16Mo3 – INCONEL 718 4.1.6 Normalisierungsgefüge von 16Mo3 4.1.7 Zusammenfassung der Mikrostrukturcharakterisierung 4.2 Thermische Ausdehnung 4.2.1 Maßänderung 4.2.2 Eigenspannungen 4.3 Mechanische Eigenschaften 4.3.1 Zugversuch 4.3.2 Zugscherversuch 4.3.3 Ermittlung der kritischen Überlapplänge 4.4 Demonstrator 5 Zusammenfassung und Ausblick / Nickel-base alloys for thermally high loaded components are widely used for gas turbine burner parts. By means of flow direction burner parts are located prior to the combustion. They are therefore one-sided thermally loaded. An economical efficient use of nickel based alloys can be achieved in combination with low alloyed steels for thermally less loaded components. The aim of this work is the development of brazing processes for GT-burner manufacturing related nickel based alloys and the low alloyed steel 16Mo3 (1.5415) using nickel based filler materials. The development includes a microstructural characterization of the brazed compounds, the evaluation of thermal expansion behavior and the maximum strength. A final test examines the feasibility by means of industrial manufacturing.:1 Einführung 1.1 Einleitung und Motivation 1.2 Stand von Wissenschaft und Technik 1.3 Schlussfolgerungen und Zielsetzung 2 Technologische Grundlagen 2.1 Der Hochtemperaturlötprozess 2.2 Thermische Ausdehnung 2.3 Diffusion 2.4 Metallurgische Prozesse 3 Experimentelle Durchführung 3.1 Grund- und Lotwerkstoffe 3.2 Lötprozesse und Probengeometrien 3.3 Mikrostrukturelle, thermische und mechanische Charakterisierung 4 Ergebnisse und Diskussion 4.1 Mikrostrukturcharakterisierung 4.1.1 Grundwerkstoffe 4.1.2 Lötsystem 16Mo3 – INCONEL 625 4.1.3 Lötsystem 16Mo3 – Nimonic 75 4.1.4 Lötsystem 16Mo3 – Hastelloy X 4.1.5 Lötsystem 16Mo3 – INCONEL 718 4.1.6 Normalisierungsgefüge von 16Mo3 4.1.7 Zusammenfassung der Mikrostrukturcharakterisierung 4.2 Thermische Ausdehnung 4.2.1 Maßänderung 4.2.2 Eigenspannungen 4.3 Mechanische Eigenschaften 4.3.1 Zugversuch 4.3.2 Zugscherversuch 4.3.3 Ermittlung der kritischen Überlapplänge 4.4 Demonstrator 5 Zusammenfassung und Ausblick