US 12,128,474 B2
Method for preparing negative pressure film-covering frozen sand mold
Haoqin Yang, Nanjing (CN); Zhongde Shan, Nanjing (CN); Qinjiang Liu, Nanjing (CN); Jianpei Shi, Nanjing (CN); Dandan Yan, Nanjing (CN); and Shijie Dong, Nanjing (CN)
Assigned to NANJING UNIVERSITY OF AERONAUTICS AND ASTRONAUTICS, Nanjing (CN)
Appl. No. 18/037,783
Filed by NANJING UNIVERSITY OF AERONAUTICS AND ASTRONAUTICS, Nanjing (CN)
PCT Filed Sep. 5, 2022, PCT No. PCT/CN2022/117063
§ 371(c)(1), (2) Date May 19, 2023,
PCT Pub. No. WO2023/221341, PCT Pub. Date Nov. 23, 2023.
Claims priority of application No. 202210533241.7 (CN), filed on May 17, 2022.
Prior Publication US 2023/0398601 A1, Dec. 14, 2023
Int. Cl. B22C 9/12 (2006.01); B22C 9/03 (2006.01)
CPC B22C 9/126 (2013.01) [B22C 9/03 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A method for preparing a negative pressure film-covering frozen sand mold, comprising:
step 1: numerically cutting a frozen sand blank mixed with water directly in a low-temperature machining environment through a numerical model-free freeze casting technology based on a cutting shaping principle to obtain upper and lower boxes of a sand mold, wherein in step 1, the frozen sand mold is provided with an air extraction hole, wherein the air extraction hole is directly drilled out on a side wall of the sand mold by numerically controlled machining;
step 2: fixing the prepared frozen sand mold in an air extraction sand box that matches the sand mold in size, and brushing a surface of a mold cavity of the sand mold of the upper and lower boxes with a layer of thermal insulation coating;
step 3: heating a thin film at 70° C. until softened to cover the surface of the mold cavity of the sand mold brushed with the thermal insulation coating;
step 4: covering an outer surface of the sand mold with a back film to seal the sand box; and
step 5: starting a vacuum pump to provide vacuum suction force, so that the thin film tightly adheres to the sand mold; covering the upper and lower boxes of the sand mold with a film under negative pressure, and then closing the upper and lower boxes to obtain an integral sand mold, wherein the thin film comprises polyester amine fibers, wherein a junction of a parting surface and the thin film is bound with an adhesive tape.