The surface quality of huge bore valves has been improved by changing the matches of molding sand, and increasing the hardness of sandmould and controlling the quality of the coal ash.
通过改进型砂配方，提高砂型紧实度和煤粉质量，是提高大口径阀门铸件表面质量的有效途径。
2
Thus we got a conclusion that increasing the velocity of pressing can increasing the hardness of sandmould surface.