机制砂粒形和级配优化试验研究

Optimization of Particle Shape and Gradation of Machine-Made Sand

为优化机制砂粒形和级配,以立式棒状搅拌磨机为整形设备,研究了介质种类、介质配比、磨机转速、料球比等整形参数对机制砂粒形的影响,并借助光学显微镜和图像处理软件,对比分析了整形机制砂与未整形机制砂的级配特性和粒形特性。结果表明:氧化锆球整形效果优于钢球和氧化铝球;在直径6 mm和8 mm氧化锆球质量比1∶1、磨机转速300 r/min、料球比1∶3、矿浆体积分数62.5%条件下整形,整形机制砂中片状颗粒质量分数和+0.15 mm粒级产率分别为4.5%和84.98%;整形机制砂具有更好的密实度和棱角性,能达到GB/T 14684—2022中Ⅰ类砂要求,其级配、粒形均优于未整形机制砂;粗粒级颗粒轮廓形状和棱角性改善程度大于细粒级颗粒。在适宜条件下,立式棒状搅拌磨可明显改善机制砂粒形、优化较粗的颗粒级配。

In order to optimize the particle shape and gradation of machine-made sand,a vertical bar stirring mill was adopted for shaping tests.The effects of medium type,medium ratio,mill rotation speed and material/ball ratio on the particle shape of machine-made sand were investigated.The gradation and shape characteristics of unshaped and shaped sands were comparatively analyzed by using optical microscopy and image processing software.The results show that the shaping effect of zirconia medium is better than that of steel or alumina medium.With the zirconia balls with diameter of 6 mm and 8 mm in a mass ratio of 1∶1,rotation speed of 300 r/min,feed/ball mass ratio of 1∶3 and pulp volume fraction of 62.5%,the milling process results in the shaped sand with fineness of+0.15 mm 84.98%and flake granule accounting for 4.5%.The shaped machine-made sand has better compactness and angular characteristics,and it is qualified as the type I sand according to the standard GB/T 14684—2022,with better gradation and particle shape compared to the unshaped sand.The contour shape and angular characteristics of coarse granules can be greatly optimized than those of fine particles.It is concluded that under suitable conditions,a vertical bar stirring mill can obviously improve the shape of machine-made sand and optimize coarser grain composition.