Improvement Of Gas-Evolution Tester For Foundry Sand

Gas-evolution is an important index offoundry sandin the casting process. There are two methods ofmeasuring the gas-evolutionof foundry sand: the pressure testingmethod and the volume testingmethod. At present, some practical testers are developed to measure thegas-evolution according tothe principle of pressure testing method. However, there are many deficienciesduring testing. For emample, the gas-evolution tester need to keep the balance between the atmospheric pressure andthe pressure of the whole system, butthe pressure will lead to thechange of water level inthe calibration tube when the foundry sand was heated andthus the gas was generated, whichwill cause a larger error and poorer data accuracy.For the above situation, the traditional gas-evolution testerwas improved in this paper.According to the latest national standard GB/T2684-2009 aboutthe amount andthe velocity of foundrysand gas-evolution in 2009 and the need of the actual situation and the experiment, thetesterwas improvedbased onthe equation of gas state. The foundry sand samplewas heated in thehigh-temperature decompositionfurnaceunder the control ofcomputer, and the voltage signal of the gas-evolution was real-time monitored and accurately measuredby a high precision diffused-silicon pressure sensor. Subsequently, the measuring results are recorded andthe gas-evolution offoundry sandwas calculatedby computer.The test principles and the realization ways of improved gas-evolution tester for foundry sandaremianlypresented in this paper. The PCI8360 V data acquistion card of ZHONGTAIcompanywas used to acquired the data, and the software ofgas-evolution tester was written by VB. After debugging,the gaswas injected into the decompostion tube by the constant volume injection atdecomposition temperature of foundry sand, which was simulated the gas-evolution the foundry sand. Simultaneously, the pressure was measured by the diffused-silicon pressure sensorand computer, and a model of calculating the gas evolution was got by the regression analysis method. Based on this, the experiments on the improved gas analyzer were performedto validate the accuracy. The experimental results showed that the error was below 2 %, and the root mean square error was below 0.4, and the coefficient of variation was about 0.02. This proved that the improved tester has a high precision, good stability, convenient operation.