排列三定胆最准的方法后三

简介：There are three reasons. First, although iron mold cannon casting has greatly improved the efficiency of cannon casting and saved costs, it has changed from one mold and one cannon in clay mold casting to one mold with multiple cannons. But its shortcomings are also very serious. Because the iron mold conducts heat quickly and the castings condense quickly, the cannons cast are all made of white iron.