Solidification period

It is only when starting the operation of the press that the container is heated up, this being done as a rule by steam, to a temperature of about 100 °C. The molten lead must not be poured into a cold container as this would cause cracks in the steel. Prior to and during the solidification period the container is cooled with steam. If the heat elemination is not sufficient, hot water is passed through the steam ducts the temperature of the water must not be below 80 °C to avoid thermal stresses. 

On account of what has been said in the foregoing, these presses destined for the production of rubber-insulated cable and rubber hoses, may be charged with solid cylindrical lead billets instead of molten lead. Thus the solidification periods are eliminated and a substantial increase in production is achieved. 

Applicability Limitation Vitrification was originally tested as a means of solidification/immobilization of low level radioactive materials. It may also be useful for forming barrier walls. This latter use needs testing and evaluation to determine how uniform the wall would be and to evaluate the stability of the material over a period of time. 

During cooling, a point D is reached where the internal air temperature decreases less quickly for a period. This represents the solidification of the plastic and because this process is exothermic, the inner air cannot cool so quickly. Once solidification is complete, the inner air cools more rapidly again. Another kink (point E) may appear in this cooling curve and, if so, it represents the point where the moulding has separated from the mould wall. In practice this is an important point to keep consistent because it affects shrinkage, warpage. 

Computer simulation applied to problems of crystal growth and solidification is a very strongly growing field at present. There are currently over two hundred publications per year appearing on these subjects. Clearly, it is impossible to give a completely fair review of all the ideas emerging over a period of several years. To facihtate the orientation of the reader, we have... 

A concern raised during full scale operations of the CHEMFIX process was the possibility of contaminant leaching from freshly treated, moist material. During normal processing procedures, treated material would be transferred directly onto the solidification cell. It would be this material that exhibited the potential for contaminant leaching in those 48 hours it took to physically solidify. To determine when the metals were actually bound in the product matrix, a TCLP analysis was done on a series of treated samples over a period of curing times. The results are illustrated in Table 4. 

Convection in Melt Growth. Convection in the melt is pervasive in all terrestrial melt growth systems. Sources for flows include buoyancy-driven convection caused by the solute and temperature dependence of the density surface tension gradients along melt-fluid menisci forced convection introduced by the motion of solid surfaces, such as crucible and crystal rotation in the CZ and FZ systems and the motion of the melt induced by the solidification of material. These flows are important causes of the convection of heat and species and can have a dominant influence on the temperature field in the system and on solute incorporation into the crystal. Moreover, flow transitions from steady laminar, to time-periodic, chaotic, and turbulent motions cause temporal nonuniformities at the growth interface. These fluctuations in temperature and concentration can cause the melt-crystal interface to melt and resolidify and can lead to solute striations (25) and to the formation of microdefects, which will be described later. 

Tverdokhleb, G., Gulyaev-Zaitsev, S. 1966. Kinetic peculiarities of milk fat solidification at different temperatures and various cooling periods. Proc. 17th Int. Dairy Congr. (Munich) C 2, 283-287. 

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