A study of slag corrosion of oxides and oxide-carbon refractories during steel refining

The use of ceramic material as refractories in the manufacturing industry is a common practice worldwide. During usage, for example in the production of steel, these materials do experience severe working conditions including high temperatures, low pressures and corrosive environments. This results in lowered service lives and high consumptions of these materials. This, in turn, affects the productivity of the whole steel plant and thereby the cost. In order to investigate how the service life can be improved, studies have been carried out for refractories used in the inner lining of the steel ladles. More specifically, from the slag zone, where the corrosion is most severe. By combining thermodynamic simulations, plant trails and post-mortem studies of the refractories after service, vital information about the behaviour of the slagline refractories during steel refining and the causes of the accelerated wear in this ladle area has been achieved. The results from these studies show that the wear of the slagline refractories of the ladle is initiated at the preheating station, through reduction-oxidation reactions. The degree of the decarburization process is mostly dependent on the preheating fuel or the environment. For refractories without antioxidants, refractory decarburization is slower when coal gas is used in ladle preheating than when a mixture of oil and air is used. In addition, ladle preheating of the refractories without antioxidants leads to direct wear of the slagline refractories. This is due to the total loss of the matrix strength, which results in a sand-like product. Thermal chemical changes that take place in the slagline refractories are due to the MgO-C reaction as well as the formation of liquid phases from impurity oxides. In addition, the decrease in the system pressure during steel refining makes the MgO-C reaction take place at the steel refining temperatures. This reduces the refractory’s resistance to corrosion. This is a serious problem for both the magnesia-carbon and dolomite-carbon refractories. The studies of the reactions between the slagline refractories and the different slag compositions showed that slags rich in iron oxide lead mostly to the oxidation of carbon/graphite in the carbon-containing refractories. This leads to an increased porosity and wettability and therefore an enhanced penetration of slag into the refractory structure. If the slag contains high contents of alumina and or silica (such as the steel refining slag), reactions between the slag components and the dolomite-carbon refractory are promoted. This leads to the formation of low-temperature melting phases such as calcium-aluminates and silicates. The state of these reaction products during steel refining leads to an accelerated wear of the dolomite-carbon refractory. The main products of the reactions between the magnesia-carbon refractory and the steel refining slag are MgAl2O4 spinels, and calcium-aluminates, and silicates. Due to the good refractory properties of MgAl2O4 spinels, the slag corrosion resistance of the magnesiacarbon refractory is promoted.

'They would never receive you without a husband' : Paradoxical barriers to antenatal care scale-up in Rwanda

OBJECTIVE: to explore perspectives and experiences of antenatal care and partner involvement among women who nearly died during pregnancy ('near-miss'). DESIGN: a study guided by naturalistic inquiry was conducted, and included extended in-community participant observation, semi-structured interviews, and focus group discussions. Qualitative data were collected between March 2013 and April 2014 in Kigali, Rwanda. FINDINGS: all informants were aware of the recommendations of male involvement for HIV-testing at the first antenatal care visit. However, this recommendation was seen as a clear link in the chain of delays and led to severe consequences, especially for women without engaged partners. The overall quality of antenatal services was experienced as suboptimal, potentially missing the opportunity to provide preventive measures and essential health education intended for both parents. This seemed to contribute to women's disincentive to complete all four recommended visits and men's interest in attending to ensure their partners' reception of care. However, the participants experienced a restriction of men's access during subsequent antenatal visits, which made men feel denied to their increased involvement during pregnancy. CONCLUSIONS: 'near-miss' women and their partners face paradoxical barriers to actualise the recommended antenatal care visits. The well-intended initiative of male partner involvement counterproductively causes delays or excludes women whereas supportive men are turned away from further health consultations. Currently, the suboptimal quality of antenatal care misses the opportunity to provide health education for the expectant couple or to identify and address early signs of complications IMPLICATIONS FOR PRACTICE: these findings suggest a need for increased flexibility in the antenatal care recommendations to encourage women to attend care with or without their partner, and to create open health communication about women's and men's real needs within the context of their social situations. Supportive partners should not be denied involvement at any stage of pregnancy, but should be received only upon consent of the expectant mother.

Musikfolkhögskolans utbildningsideologier

I denna artikel redogörs för två delstudier i projektet Musikfolkhögskolans utbildningsideologier. Dels behandlas utbildningsideologier bland svenska folkmusiker under 1920-talet (von Wachenfeldt, Brändström & Liljas, 2012a) och dels ges en bild av hur undervisningen av folkmusiker kan gestalta sig i en samtidskontext (von Wachenfeldt, Brändström & Liljas, 2012b).I projektet som helhet anknyts till ett ideologibegrepp som utvecklats av Sven-Erik Liedman. Han menar att det för varje tid fnns två identiferbara grundformer av ideologi: manifesta och latenta (1997; 2006). Manifesta ide-ologier avser explicita och medvetet formulerade utsagor med ideologiskt innehåll som binder samman verklighetspåståenden, värderingar och nor-mer. Latenta eller frusna ideologier är sådant som fnns under ytan och som tas för givet av fältets aktörer.