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研究了发泡石膏铸型制备过程中各试验因素对石膏混合浆料胶凝硬化时间、室温抗压强度、流动半径和发泡率的影响。结果表明,石膏混合浆料的胶凝硬化时间与水料比成正比,石英粉、高岭土、硅藻土、NaCl和MgSO4石膏辅料的添加提高了石膏铸型的室温抗压强度。随着水温升高,石膏混合浆料的胶凝硬化时间、室温抗压强度、流动半径和发泡率均呈现先上升后下降的趋势。以十二烷基硫酸钠作发泡剂,在硬水环境下仍可以制得发泡率为80%的发泡石膏铸型。低搅拌速度短时间下,发泡剂难以发泡完全;长时间高搅拌速度下,气泡易破碎消失,在转速为2000r/min经4min搅拌时石膏发泡最好。根据试验工艺参数制得了发泡石膏铸型并进行了热烘烤,在715℃下浇注了ZL114A合金铸件,热烘烤过程中发泡石膏铸型无开裂,同时铸件满足实际使用要求。
The effects of various test factors on the gelling time, compressive strength at room temperature, flow radius and foaming rate of the gypsum mixed slurry were studied. The results show that the gelling time of gypsum slurry is proportional to the ratio of water to material. The addition of quartz powder, kaolin, diatomite, NaCl and MgSO4 gypsum improves the room temperature compressive strength of gypsum mold. With the increase of water temperature, the gelation hardening time, compressive strength at room temperature, flow radius and foaming rate of gypsum mixed slurry all showed the tendency of first increasing and then decreasing. With sodium dodecyl sulfate as foaming agent, foamed gypsum mold with 80% foaming rate can be obtained in hard water environment. Low stirring speed for a short time, the foaming agent is difficult to foaming completely; long time high stirring speed, the bubble easily broken disappear, at a speed of 2000r / min gypsum foam mixing 4min best. According to the experimental parameters, a foamed gypsum mold was prepared and hot baked. The ZL114A alloy castings were cast at 715 ℃. The foamed gypsum molds did not crack during the hot bake process, and the castings met the actual requirements.