The reasons are as follows:
(1) The true density of fused ceramic sand is relatively large. The kinetic energy of sand particles with the same diameter and speed during core shooting is 1.28 times that of silica sand particles, which can improve the compactness of the sand core. According to the osmotic pressure formula of mechanical sand sticking: p=28cosa/r (where 8 is the surface tension of metal liquid, a is the wettability angle of liquid metal and mold, r is the mold pore radius), the pore radius r between sand particles of dense sand core is small, which can resist sand sticking back.
(2) The round shape of fused ceramic sand can improve the fluidity of coated sand, reduce sand resistance and kinetic energy loss during core shooting, ensure the filling effect of core shooting, so as to reduce the pore radius r between sand particles and resist sand sticking.
(3) Fused Ceramic sand has low thermal expansion, reduces the pressure on the thin sand core at high temperature, and improves the stability of the thin sand core at high temperature.
(4) Fused Ceramic sand has a large specific heat capacity. With the same volume, it can absorb more heat from molten iron, reduce the fluidity of molten iron, and crust earlier, so as to resist sand sticking. The inspection after pouring found that the problems of sand sticking and notch were eliminated.
Stomatal Case Analysis
The pores are large in volume, smooth on the inner surface, with metallic luster or oxide skin. The tail of pear shaped pores is directional. They are typical invasion pores and are concentrated above the water jacket core. It can be determined that the invasion pores are caused by the excessive gas generation of the water jacket core. As the coated sand core forming the channel cavity during pouring is deeply buried in the molten iron, it is difficult to exhaust, and the gas tends to accumulate in the cavity and form a higher pressure. When the gas pressure PC > p&+pp+pg, an invading gas pore is formed.
Measures to solve air holes and implementation effect according to the analysis, reducing the air generation of water jacket core can solve the problem of invasive air holes. The requirements in this case include two aspects: reducing the gas generation and maintaining the current strength.
Fused Ceramic sand has good grain shape and angular coefficient<1.1, approximately spherical. Compared with silica sand, less resin can meet the strength design requirements. The coated sand is made by mixing fused ceramic sand and silica sand in a certain proportion, which significantly reduces the gas generation, which significantly improved the qualified rate of castings.
Conclusion of Fused Resin-coated Ceramic Sand in Automobile Engine Cylinder
Thin wall and light weight of engine cylinder block is the core idea of engine design. Compact and complex structure is the normal characteristics of future cylinder castings. The application of Fused Resin-coated Ceramic Sand in the casting of automobile engine cylinder block can effectively eliminate and reduce the casting defects such as oil channel core deformation, cylinder barrel gap, sand sticking, air hole, wall thickness out of tolerance, and improve the casting quality.
The experience of using fused Resin-coated Ceramic Sand to solve the casting defects of cylinder block has accumulated experience for dealing with more difficult casting technical challenges in the future, and also provided technical reserves for the full realization of vertical casting thin-walled cylinder block.