Co <sub> 2 </ Sub> Sodium Silicate Sand To Promote Hard Technology

CO₂ sodium silicate sand holds a leading post in the cast steel industry of our country. It is more superior other sodium silicate sand in the cost, efficiency, operation. But in the winter this kind of sand have many problems what bring greatly troublesome for the factory, such as the low hardening speed, low intensity, and the large gas consumption. Therefore, this topic research goal is to study the hardened process or the hardening agent what is adequate for the CO₂ hardening sodium silicate sand in low temperature.First, analyzing and comparing the hardened mechanism of the sodium silicate sand, then obtaining two common rules in the hardening process of sodium silicate: the hydrolysis process and dehydration process. The former is physical hardening, and the latter is chemistry hardening. The two processes have the close relationship with the temperature. Therefore, to improve the hardening speed and the intensity of the sodium silicate sand, considering adopting the method of CO₂ physical hardening and chemistry hardening.Secondly, choosing the methods of CO₂ physical hardening, it mainly is heating hardening, blending the gas hardening, and replacing hardening. For this purpose, designing a gas heater as well as a set of air flush system, then carrying on a series of experiments including CO₂ hardening, the CO₂ mixed air hardening, CO₂-air replacing hardening which preheating or the non-preheating. In order to improve the hardening effect of sodium silicate, the gas rate of flow, process of air puffing, time of gas puffing as well as the pinhole spacing of the plunging tube has been carried out the systemic experiment, and building a mathematic model of main parametric between hardening depth and the gas rate of flow, process of air puffing, time of gas puffing as well as the pinhole spacing of the plunging tube. Moreover, carrying out an exploration on various hardening agent in the field of chemistry hardening, then it has developed one kind of new hardening agent of sodium silicate. Meanwhile, it has used orthogonal design method to choose the main technological parameters or more excellent plan, and carried out contrast and analysis with FeSO₄.The experimental result indicated that: the heater and the system can apply to practice successfully; through the CO₂ mixed air to enhance the hardening the speed of sodium silicate is not good; adopting the CO₂ preheating hardening or CO₂- air replacing hardening of the preheating or non-preheating not only can improve the hardening speed of the sodium silicate sand, but also save 50% CO₂; when temperature is 18℃, and the humidity 5%RH, the superior process which the non-preheating CO₂- air replacing hardens sodium silicate sand is: the amount of sodium silicate is 6%, and the Time interval is 30s. At the same condition, the superior process of the preheating CO₂-air replacing hardening includes 6% sodium silicate and the time interval is 10s. The new sodium silicate hardening agent to a great extent can improve the hardening speed of sodium silicate sand. The first hardening strength compared to CO₂ sodium silicate sand has enhanced 92.5% in the same time, enhanced 26% compared to the FeSO₄, and the drying intensity is nearly to CO₂ sodium silicate sand. But the intensity after of 24 hours is somewhat low; it waits for the further research.Finally, using scanning electron microscope and X diffraction to examine and research the different kinds of sodium silicate sand. It has confirmed the temperature comes into being higher, the more compact organization, but also increasingly easy to lead to a crack. It demonstrated to enhance the hardened speed of the sodium silicate sand should choose the appropriate temperature. When the flow amount of CO₂ is 25L/min and the pressure is 0.15MPa, the better temperature is 35℃.