The paper is devoted to the findings of methodology of curing rate of one-component polyurethane sealants. These sealants are widely used in automotive (engineering) industry as mastic sealant for gluing joints and for filling wider gaps between uneven surfaces. As suitable methodology for setting curing rate was suggested measuring the thickness of setting sealant cured in cardboard moulds. It was found that cardboard mould is not a barrier for air humidity that is a curing agent for these types of sealants. The methodology is simple and applicable in industry.
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This paper deals with specific changes in the structure of crossings made of Hadfield's steel, caused by heat and mechanical stress during the welding process, and of rails made of carbon steel. Experiments were undertaken to analyze the sources of damage to the weld joint, established by a post-weld capillary test after machining the weld joints. The analysis demonstrated the presence of welding defects consisting of a phosphide phase and of carbides as a secondary phase. The distribution and amount of this undesirable phase was given by the technical welding parameters employed. It was established that the material is prone to hot tearing only in a very narrow zone inside the heat-affected zone where comprehensive reaustenitization takes place. Initiation of the defects is related to the presence of a phosphide eutectic. A further growth of cracks takes place along the carbide border line; this means that the main factor limiting the use of such welds is attainment of structural degradation. Reducing the thermal effect on the welded components is thus essential for further use of the investigated samples
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