Modelling of the heating process massive batch
At technological processes of metallurgy and machine industry is metals heating one of the most important operations have influence on production in term of the efficiency, quality and costs. Charge inner temperature is an important variable in the heating process, because allows to determine the phase of the material treatment (change in the structure of the material). Currently, charge inner temperature is not measured for the following reasons: the design of the furnace (moving charge), destruction of a sensor during the process, the increased cost of furnace operation etc. This article describes a method for modelling the temperature in the charge, which is a steel coil. The method calculates the charge inner temperature by measured charge surface temperature in the annealing process. The resulting accuracy is evaluated by statistical methods.
Graphic presentation of selected thermochemical properties of substances in Matlab using service oriented architecture
This contribution deals with the disclosure of the thermochemical properties of individual substances by using a service-oriented architecture through a web service that is implemented in the client environment MATLAB. The basic principles of service-oriented architecture and its use by web service are described and a specific web service that provides different thermochemical properties such as molar heat capacity, enthalpy, entropy, and the like is listed. The following describes the design and implementation of functions for the MATLAB client environment, which makes it easy to obtain, to elaborate and to make available the thermochemical properties provided by the web service. Solution of application interface is based on taking advantage of graphic user interface support MATLAB and mentioned web service. Application interface consists of parameters for identification of substance, temperature's scope and step, graph size and x-axis ticketing density as well as if appropriate of file name in which calculated graph course is in graphics format. Finally, specific examples are shown using created functions and graphics interface. Possibilities of potential uses are discussed.
Hygroscopic Expansion of some Casting Investments
CREDIT is generally given to Taggart1 for introducing the cast gold inlay to the dental profession. Although he realized that gold shrinks when cooled from molten state to solid state of room temperature, the investment available to him did not supply sufficient compensation. In 1910, Van Horn2 published a paper dealing with a method by which he obtained the compensation by means of wax expansion. The next major research in connection with this problem was the work of Coleman3 at the National Bureau of Standards. He determined the gold shrinkage to be 1.25 per cent and presented a casting technic with compensation values of quantitative nature. The total compensation for the gold shrinkage was obtained by the combination of the setting and thermal expansion of the mold. This procedure is the general practice followed at the present time for compensation. There are some disadvantages to this method. Skinner has indicated the difficulty of obtaining smooth castings and the improper compensation for the casting shrinkage.4 It has been found by Hollenback5 and Scheu6a that castings made at a high temperature are rougher than those made at a low temperature (450° C.), depending upon the great difference in thermal expansion between plaster of Paris and silica, which causes a poor union of the fine particles. This may also result in friability and there may be some warpage due to the differential expansion. A method which provides sufficient compensation at a low mold temperature is the hygroscopic casting technic.b Wilson7 showed that certain plasters expand as much as 0.0044 inch to the inch by taking up moisture from the air. With this information at hand, Scheula, b tested some commercial investment to determine what results the addition of moisture would have. He found6b: (1) All of the casting investments that were tested expanded. (2) The thicker the mix, the greater the expansion. (3) A mix with hot water expanded more than one with cold water. (4) The time at which the mix is placed in the water is of great importance. It was found that if the mix is placed in the water early, it would not expand so much as when placed in a little later. It was also found that if the mix was placed in the water after a certain time, it could not expand to the maximal amount. (5) The temperature of the water in which the mix is placed is important, for two reasons; (a) the temperature of the water controls slightly the expansion of the investment, and (b) water at a temperature of 1000 F. slightly softens the wax pattern so that the fine margins are not marred while expansion is taking place. The mix should remain in the water at least 20 minutes to obtain the full expansion, after which time no further expansion is obtained.