Technique for casting gray cast iron thin-wall pipe fitting evanescent die

Abstract

The invention relates to the field of casting evanescent dies, in particular to the technique for casting a gray cast iron thin-wall pipe fitting evanescent die. The purpose that the technique for casting the evanescent die is applied to the field of gray cast iron thin-wall pipe fitting production is achieved. The technique for casting the gray cast iron thin-wall pipe fitting evanescent die comprises the steps of bead pre-foaming, die manufacturing and forming, white die drying and bonding, coating, drying, encasing, vacuum-assist pouring and out-casing and grinding. The die manufacturing and forming comprises that the steps of operating a make-up machine to close the die, filling a model of the make-up machine with EPS beads obtained in the step of bead pre-foaming, filling the model of the make-up machine with steam, cured EPS beads and the formed white die, filling the model of the make-up machine with cooling water to be cooled and operating the make-up machine to open the die and taking out the white die. The technique is improved reasonably, the defect of caliber of a gray cast iron thin-wall pipe fitting can be effectively avoided, the quality of the gray cast iron thin-wall pipe fitting is improved, and the technique is suitable for being used for manufacturing a high-precision and high-quality gray cast iron thin-wall pipe fitting.

Description

technical field [0001] The invention relates to the field of lost foam casting, in particular to a lost foam casting process of gray cast iron thin-walled pipe fittings. Background technique [0002] At present, the gray cast iron thin-walled pipe fittings (wall thickness 3-4mm) on the market are mostly produced by sand casting method. The production of thin-walled pipe fittings by sand casting method has the following technical problems: 1. For thin-walled pipe fittings with complex structures, it is difficult to make cores, and it is difficult to take out the core bone after casting. It can only be interrupted and scrapped, and the core bone needs to be continuously made for reproduction; 2. The positioning is not accurate during the casting process, and it is easy to form core lifting during the production pouring process, resulting in uneven wall thickness of the pipe fittings; 3. For longer types of pipe fittings, such as 1.5m double-socket thin-walled pipe fittings and...

AI Technical Summary

Problems solved by technology

The production of thin-walled pipe fittings by sand casting method has the following technical problems: 1. For thin-walled pipe fittings with complex structures, it is difficult to make cores, and it is difficult to take out the core bone after casting. It can only be interrupted and scrapped, and the core bone needs to be continuously made for reproduction; 2. The positioning is not accurate during the casting process, and it is easy to form core lifting during the production pouring process, resulting in uneven wall thickness of the pipe fittings; 3. For longer types of pipe fittings, such as 1.5m double-socket thin-walled pipe fittings and long sides For straight and curved thin-walled pipe fittings, it is more difficult to cast clay sand wet mold, and clay sand dry mold casting process is required. The core drying furnace used in sand dry casting is a waste of energy, and the clay sand dry casting process is already an outdated process to be eliminated in the foundry enterprise access system of the Ministry of Industry and Information Technology and the Ministry of Industry and Information Technology [2010] to eliminate some industrial product process catalogs

For thin-walled castings with a wall thickness of only 3-4mm, the uneven density of the casting white mold directly leads to uneven strength and stiffness at the corresponding parts of the white mold, which makes it difficult to control the roundness of the white mold when sticking the mold. It is easy to cause caliber defects (oval or out of round) of pipe fittings, which not only brings great difficulty in correcting the caliber in subsequent processes such as mold sticking, coating, drying, and boxing molding, but also makes it difficult to guarantee product quality; it also seriously wastes EPS. Bead raw material, this may be the reason why few manufacturers in China use the lost foam casting process to produce thin-walled pipe fittings

In addition, there is a non-negligible problem in the production of gray cast iron thin-walled pipe fittings by the lost foam casting process-"coating blistering" of the white mold of the pipe fittings, that is, after the white mold is coated with a refractory coating, the coating surface appears when it is dry. Some coating protrusions of different sizes and irregular distribution will be broken with a light pressure of fingers, forming a cavity between the coating and the white mold; this phenomenon directly affects the surface quality of the product

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