一、前言 长期以来,我厂铸钢车间一直采用石灰石砂作型砂生产铸钢件。石灰石砂有其优点:易清砂,减轻工人的体力劳动,消除工人矽肺病等。但也存在缺点:铸件易产生气孔、裂纹、缩沉,表面凸凹不平。随着大型机组产量的增加,要求超声波探伤的铸件越来越多,这些缺点显得更加突出。所以,必须寻找一种新的材料以克服上述缺点,降低成本, I. Foreword For a long time, our factory cast steel workshop has been using limestone sand for the production of castings steel. Limestone sand has its advantages: easy to clear sand, reduce manual labor, workers to eliminate silicosis and so on. But there are also disadvantages: easy to produce porosity, cracks, shrinkage, uneven surface. With the increase of the production of large-scale units, more and more castings are required for ultrasonic flaw detection. These shortcomings are even more conspicuous. Therefore, we must find a new material to overcome the above shortcomings, reduce costs,