Zugl.: Clausthal, Techn. Univ., Diss., 2007

Essen, Universiẗat, Diss., 2004--Duisburg.

Zugl.: Hamburg, Techn. Univ., Diss., 2008

Inert gas atomization is one of the main sources for production of metal powder forpowder metallurgy and additive manufacturing. The obtained final powder size distribution iscontrolled by various technological parameters: gas flow rate and pressure, liquid metal flowrate, gas type, temperature of spraying, configuration of nozzles, etc. This work explores anotherdimension of the atomization process control: modifications of the liquid metal properties andtheir effect on the obtained powder size. Series of double-alloyed Cr-Mn-Ni steels with sulfur andphosphorus were atomized with argon at 1600◦C. The results indicate that surface tension andviscosity modifications lead to yielding finer powder fractions. The obtained correlation is comparedwith the individual modification of surface tension with S and Se and modification of viscosity withphosphorus. Discrepancy of the results is discussed. Additives of surfactants and viscosity modifierscan be a useful measure for powder fractions control.

Syftet med denna studie var att undersöka om landströmsanslutningar bör placerares midskepps vid manifoldern, alternativt i aktern på tankfartyg. Fokus låg på att hitta bästa placeringen utifrån säkerhet och arbetsmiljö ombord på fartyget och i hamnen. Detta studerades genom kvalitativa intervjuer med sex olika aktörer inom området för att få ta del av deras erfarenheter och åsikter kring ämnet. Parallellt genomfördes även en faktainsamling där standarder, regelverk samt tidigare forskning på området samlades in. Resultatet från intervjuerna sammanställdes och jämfördes sedan mot materialet från faktainsamlingen.  De krav som ställs i olika standarder kan, oavsett placering, innebära säkerhets- och arbetsmiljö nackdelar men respondenterna var övertygade om att man med rätt utrustning och rutiner kan upprätthålla en säker och god arbetsmiljö. Utifrån säkerhet ansåg flera respondenter att en placering långt ifrån manifoldern, där fartygets last hanteras är att föredra även om det finns andra säkerhetsmässiga nackdelar med en sådan placering. Arbetsmiljömässigt hade respondenterna flera för- och nackdelar med båda placeringarna som främst rörde problematiken kring kabelhanteringen. / The purpose of this study was to investigate whether shore power connections should be placed midships at the manifold, or alternatively, aft on tanker vessels. The focus was on determining the best location based on safety and working conditions onboard the vessel and in the port. This was studied by conducting qualitative interviews with six different stakeholders in the field to gain insight into their experiences and opinions on the subject. Concurrently, a data collection was conducted where standards, regulations, and previous research in the field were gathered. The results from the interviews were compiled and compared against the material from the data collection.  Regardless of the placement, there are safety and working environment disadvantages that are also stipulated as requirements in various standards, but the respondents were convinced that with the right equipment and procedures, a safe and good working environment can be maintained. Concerning safety, several respondents believed that a placement far from the manifold where the vessel's cargo is handled is preferable, even though there are other safety disadvantages associated with such placement. In terms of the work environment, the respondents identified several pros and cons with both placements, primarily related to the issue of cable handling.

The paper presents new results concerning the influence of the gas density and porous plug diameter on the nature of liquid steel stirring with an inert gas in the ladle. The tests were carried out on a cold model of a 30t ladle using particle image velocimetry (PIV) with a high-speed camera to analyse the plume zone formed during the supply of argon and helium as a stirring gas. The similarity criteria for the investigation of stirring processes in cold model in the past were discussed and compared. The modified Morton number was used in this paper to relate the gas flow rate in the model with real objects. The presented results constitute complete documentation of the influence of the plug diameter and gas density on the size of formed gas bubbles and the velocity of gas bubbles rising in different zones of the plume, plume, and spout geometry, including the expansion angle, spout height, open eye area, and gas hold-up.