The assembly and welding process of investment casting impeller includes wax mold trimming, wax mold cleaning, wax mold inspection and wax mold assembly and welding.
a. Wax mold trimming and cleaning
The excess flash and burr on the wax mold shall be removed, the wax injection port shall be flattened, and other parts shall not be trimmed. It is not allowed to damage the working surface of the investment casting impeller during trimming.
Prepare a neutral soap solution with a concentration of 0.2% ~ 0.3%. The temperature of the soap solution is 20 ~ 25 ℃. Firstly, clean the module in the soap solution, remove the oil stain on the surface with a soft brush, and then clean it in 20 ~ 25 ℃ water to ensure the coating performance of the wax mold surface.
b. Wax mold inspection
Welding can only be carried out after the wax mold is inspected to be qualified, and assembly welding is not allowed for unqualified wax molds. Wax mold inspection includes appearance quality inspection (100% of wax mold shall be subject to appearance inspection, and the surface shall be free of shrinkage, crack, wrinkle and bulge) and size inspection (100% of wax mold shall be subject to size and shape inspection), and the molding process shall be supervised.
c. Wax mold assembly and welding
The wax mold assembly and welding of the whole investment casting impeller part shall be completed with the help of the previously designed welder assembly, and the welding process shall be positioned with the help of the positioning ring with a diameter of 425.15 ± 0.25mm and the arc of the edge part of the investment casting impeller. During the assembly and welding of investment casting impeller blades, the uniform arrangement of investment casting impeller blades can be ensured through the sample plate and measuring the maximum chord length between each investment casting impeller blade. The welding temperature is about 80 ℃, and the weld must be smooth without wax spots, concave joints and false welding. The assembly and welding process of investment casting impeller blade is shown in the figure. The specific assembly and welding process of investment casting impeller blade is as follows:
(1) First, place 54 investment casting impeller blades that have been pressed, trimmed and passed the inspection on the tooling as shown in figure a), and use rubber band for simple positioning.
(2) The investment casting impeller blade is strictly inspected. After placement, the positioning part of the arc of the investment casting impeller blade shall be completely consistent with the circular arc surface of the positioning ring. If individual investment casting impeller blades are not in good agreement with the positioning ring, they can be re placed after measurement and trimming.
(3) After meeting the requirements, the joint part on the upper surface of the impeller investment mold can be welded. The welding part shall have sufficient strength, tight fitting, flat surface and no weld beading, as shown in figure a).
(4) In order to weld the joint part of the investment casting impeller blade on the lower surface, after the upper surface welding is qualified, install the lower cover plate and fasten it with the fastening device. After turning over, open the upper cover plate to weld the gap at the joint part on the other side of the investment mold, as shown in Figure b).
(5) After assembly and welding, install the lower cover plate again and fasten it. In order to ensure firm fastening and prevent the deformation of the investment mold during fastening, thin paper soaked with mold material can be placed between the upper and lower cover plates and the impeller investment mold. As shown in Figure C)
(6) As shown in Figure d), after all the work is completed, the parts between the upper and lower cover plates, pressing plates and fastening nuts shall be filled with mold materials to prevent the immersion of hardening liquid during the coating of reinforcing layer and reduce the strength of the surface layer hexyl silicate coating.