自硬-微波加热复合硬化硅酸盐粘结剂砂性能研究

Study on Performance of Silicate Binder Sand by Self-Hardening and Microwave-Heating

针对自硬硅酸盐粘结剂砂用于铸铁件时存在硬化速度慢、对环境湿度敏感、砂型(芯)强度低、溃散性差四个问题,本文选择一种新型硅酸盐粘结剂,以陶瓷砂为原砂,在采用固化剂自硬的基础上,还通过微波加热以及添加粉末促硬剂,进行了复合硬化工艺的研究。首先,研究了微波加热工艺参数对型砂试样性能的影响,确定了优化微波加热工艺:加热功率为900 W、加热时间为180 s;而后,选用了三种粉末促硬剂进行优化,得到的最佳粉末添加剂优化方案为粘结剂2.2%、微硅粉0.2%、氧化铝0.2%、石英粉0.06%。结果表明,该组优化方案相比较不加入粉末添加剂,使砂型(芯)1 h强度提高至1.86 MPa,24 h强度提高至2.17 MPa,98%RH吸湿强度提高至1.45 MPa,800℃残留强度降低至0.75 MPa,其常温强度值和残留强度值分别达到和接近自硬树脂砂的水平。

There are four problems in the application of traditional water glass to cast iron,such as slow hardening speed,sensitive to ambient humidity,low strength of sand mold(core)and poor collapsibility.Therefore,a different silicate binder was selected to study the effect of composite hardening process on the performance of specimens using ceramic sand as raw sand.First of all,the effect of microwave heating power and time on the properties of molding sand samples were studied.The microwave heating power and time has been determined on 900 W and 180 s,respectively.Then three powder additives were selected,the optimal composition is as follows:binder 2.2%,micro-silica powder 0.2%,alumina 0.2%,quartz powder 0.06%.The results showed that compared with the sand core without powder additives,the strength of 1 h sand increased to 1.86 MPa,the hygrometric strength of 98%RH increased to 1.45 MPa,the strength of 24 h increased to 2.17 MPa,and the residual strength of 800℃decreased to 0.75 MPa,The strength and residual strength of the sand at room temperature reached and approached the level of self-hardening resin sand respectively.