Determine the sand mold configuration, casting material and pouring mode, that is, these influencing factors have been determined; In addition, the parameters such as pouring temperature and pouring speed have a great influence on theprocess. The two factors of pouring temperature and pouring speed will be discussed respectively.
(1) According to the selected stepped scheme, the effects of pouring temperature and pouring speed on the filling and solidification process of sand casting are studied. The filling time, internal gate solidification time, total solidification time and shrinkage size are compared respectively. It is found that the temperature has little effect on the filling time, while the solidification time increases gradually with the increase of temperature. It is determined that the appropriate pouring temperature of the reducer box is 1400 ℃. The pouring speed has little effect on the solidification time, and the mold filling time decreases with the increase of pouring speed. The optimal pouring speed is 6.8kg/s.
(2) The shortcomings of the sandscheme of the reducer box body are improved. A riser is added at the arc boss, the diameter of the riser at the upper end of the sand casting is increased, a riser is added at the rectangular boss and the boss at the upper end of the sand casting, a buffer zone is set at the connection between the lower transverse sprue and the direct sprue, and a cold iron is added at the support plate inside the reducer box, and the pouring temperature is 1400. C. The pouring speed is 6.8kg/s. The step scheme after the improvement of the gating system is simulated and the final defects are observed. Compared with the original step scheme, the shrinkage cavity and porosity casting defects are significantly reduced.
(3) On the basis of the improved stepped scheme, the structure of sand casting is improved, and the fillet radii between the two-phase walls of arc boss are increased from 5mm, 6mm and 14mm to 10mm, 12mm and 20mm; The fillet radius of the intersection of the two walls at the rectangular boss and the circular boss is 17 mm and increased to 30 ram; The thin wall of the inner lower support plate ofis increased from lomm to 15mm, and the thick wall is reduced from 30mm to 25mm. The results show that changing the size of the fillet reduces the defects at the intersection of the two walls; Change the size of the internal support plate to basically eliminate the defects at the internal support plate.