Papers by Keyword: Bloom

Abstract: The paper presents the results of the research for the reasons of the formation of a brownish bloom on a light clinker brick during its operation. In the work course, the clinker bricks, their mineralogical composition, the nature of the secondary brick coloring and the base materials were tested during bricklaying. It was established that 2 factors caused incrustation. Firstly, the site on which the clinker brick was laid was characterized by a level of alkali soil water close to the surface, and the surface evaporation prevailed over the soil absorption in the warm period of the year. That is all soil water-dissolved salts migrated to the surface of the brick along well-permeable sand joints between the bricks. Secondly, ferrous minerals, including hematite, which was subjected to hydration with the formation of iron hydroxides, and also reacted with sulphates of groundwater with the formation of iron sulphates, were found in the foundation under the brick. This confirms the higher sulfur content in incrustation areas and the presence of a film similar to crystalline hydrates. The analysis of the research allowed us to develop the recommendations for the performance of paving various types of sites with clinker bricks, to develop measures to eliminate an existing bloom, and also to defend the “honor and dignity” of light bricks.

Abstract: A mathematical heat transfer model was built to simulate temperature, shell growth and phase transformations in continuous casting based on the technical conditions of the bloom caster of some steelmaking plant. The simulation result is coincided with the measurement. The effects of the operation parameters including casting speed, bloom size and steel melt superheat on the solidification process were discussed and the means of enhancing the bloom temperature was brought forward. The research results have been applied in the practical manufacture process to compute the best casting speed, to control the flow rate of secondary cooling water and to optimize the spray pattern of secondary cooling zone. The bloom quality and productivity could be improved.

Abstract: Many eutrophic lakes are threatened by cyanobacterial blooms. The bloom-forming cyanobacteria are capable of nuisance growth and produce toxins, resulting in serious threats to water safety and human health. This paper summarized physiological and ecological characteristics of bloom-forming cyanobacteria in their annual life cycle, internal regulation mechanisms and environmental factors for blooms formation. In winter, dormant period is regarded as the continuation of cyanobacteria populations, which conserve “seed bank” for the following year. In spring, recruitment can be defined as an inoculation of overwintering cyanobacteria to the pelagic phase after growth recovery under suitable conditions. Temperature, resuspension and bioturbation had been recognized to be the main driving factors for recruitment. Shortly after recruitment, cyanobacteria establish dominance by fast growth rate and colony enlargement strategy. Under suitable meteorological and hydrological conditions, cyanobacterial colonies aggregate and float up to form heavy blooms, which can lead to water supply crisis and ecological disaster. From late autumn, blooms disaggregate and decline. The sinking process is not only a periodic life cycle but also an irregular mechanical movement. Cyanobacteria accumulation areas in late autumn might highly related to the first occurence locality of blooms in the following year. This information could provide valuable information for the prediction and prevention of cyanobacterial blooms, so as to establish a more stable and healthy ecosystem in lakes.

Abstract: Soft reduction has been proved to be the best way to minimize center segregation and eliminate center porosity. Aiming at determining optimum soft reduction parameter for variation steel grades and different process conditions, a thermal-mechanical coupled FEM(Finite Element Method) model was developed to analyze the deformation behavior of the given bloom under the operation of soft reduction technology. The mechanical strain / stress of the bloom cross-section, especially the stain /stress around the solidification front, under the application of soft reduction are obtained. Considering the high temperature mechanical properties of the given steel grade GCr15 (with chromium content of 1.40~1.65 percent and carbon content of 0.95~1.05 percent) and strain/stress distribution in the section thoroughly, the proper soft reduction parameter are determined.

Abstract: Steady increase of requirements to quality an axial zone continuously cast blooms stimulated in last time development of principles of its deformation at the end of solidifications with the purpose of suppression of axial porosity and segregation: soft reduction or mechanical soft reduction. The technology of soft reduction is one of the most effective ways of improvement quality of internal layers continuously cast blooms. In this case the central part of section of continuously cast blooms is in liquid or liquid-solid condition (mushy zone). At the same time, in practice now there are, at least, some original technical decisions for realization of this method.

Abstract: This paper has studied the formation mechanism of frame-shaped segregation in 40Cr wire rod rolled from bloom by means of the composition measurement, the electron microscopic observation and the energy spectrum analysis method. The results show that the frame-shaped segregation in wire rod originated from the positive segregation in columnar-to-equiaxed grain transition zone of bloom. The main influence factors are the solidification behavior of liquid steel in columnar-to-equiaxed grain transition zone, the temperature gradient of different solidification regions in bloom, the diffusion rate of the solute and inclusions in transition zone and so on. It may reduce the frame-shaped segregation by improving the purity of liquid steel, adopting the electromagnetic stirring in secondary cooling zone and enhancing the cooling intensity of the secondary cooling zone.

Abstract: This paper has analyzed the solidification structure and thermodynamic state of bloom by means of the electron microscopy observation and heat transfer model, and studied the cracking mechanism and influence factors in the cogging process of 40Cr bloom. The results show that the main cracking reasons are the unreasonable secondary cooling scheme, the high reheating temperature in the bloom surface, the coarser grain and widmanstatten structure of the bloom subsurface. When the bloom is conveyed from the steel mill to rolling mill, the bloom may crack for the phase transition stress and thermal stress, some micro-cracks occur in the bloom surface, furthermore, the crack will expand when it is heated in the heating furnace and rolled in the cogging mill, the cracking occurs in bloom eventually. In order to reduce the bloom cracking in the cogging process, it must optimize the secondary cooling system, reduce the cooling intensity, and adopt the thermal insulation, hot delivery and hot charge process. If the bloom can not be conveyed in the hot delivery and hot charge mode, it should be conveyed to the slow cooling pit.

Abstract: In-line oxygen sensors have been developed for the glass melt and for the float bath. Glass melt oxygen sensors are used for the continuous monitoring of the oxidation state (or redox) of the glass melt and are very important for the control of many glass melt and glass product properties such as radiative heat transfer, fining, foaming, forming and optical characteristics. Too high oxygen levels in the float bath can be prevented by using both oxygen sensors in the tin melt and the atmosphere above it. Oxygen related defects on the glass sheet surface such as dross, tin pick-up, bloom and tin drips are reduced or even prevented. Moreover, expensive hydrogen gas can be saved by a more effective dosage.