砂型铸造水基自干涂料的工艺特性

Process Characteristics of Water-based Self-curing Coatings for Sand Casting

分析了砂型铸造水基自干涂料的流变特性和发气特性,研究了涂层厚度和分次施涂对涂料自干固化速度的影响规律。结果表明:新型水基自干涂料兼有触变性流体和假塑性流体特征,触变率适中,涂刷指数较高,涂刷性好,流平性和抗流淌性的综合平衡性优良,可以同时满足各种施涂方法的流变性要求;水基自干涂层自干速度随涂层厚度的降低呈近似线性提高,厚涂层最好在保证其表面质量的前提下尽量一次性施涂;新型水基自干涂料发气量与普通水基烘干型涂料相当,但是发气速度几乎比后者慢1倍,为消除铸件气孔缺陷提供了良好条件。

The rheological and gas evolution characteristics of water-based self-curing coatings for sand casting were analyzed and the influence of coating thickness and graded coating on the self-curing rate of coating was studied. The results show that the new water-based self-curing coating has both the characteristics of thixotropic fluid and pseudoplastic fluid,which has moderate thixotropy rate and high brushing index, good brushability and excellent comprehensive balance of flow-leveling and anti-flowability. It can meet the rheological requirements of various coating methods. The self-curing speed of the water-based self-curing coating increases in an approximately linear manner with the decrease of its thickness. Thick coating should be best to paint at one time in the premise of ensuring its surface quality. The gas evolution volume of the new water-based self-curing coating is approximately equal to that of ordinary water-based baking coatings, but the gas evolution speed of self-curing coatings is almost half as that of the latter, which provides good conditions for preventing gas hole defect of castings.