Lost foam casting process for double-bell-and-spigot grey cast iron thin wall pipe fittings and sand box for process

Abstract

The invention relates to the lost foam casting field, in particular to a lost foam casting process for double-bell-and-spigot grey cast iron thin wall pipe fittings and a sand box for the process. The sand box for the process achieves the application of the lost foam casting process in the field of grey cast iron thin wall pipe fitting production. The process includes the steps of bead particle pre-foaming, mold building and molding, white mold drying and bonding, coating, drying, packaging, negative-pressure pouring, going out of a box and polishing. The mold building and molding procedure includes the steps of mold closing-filling of EPS bead particles-inflating of steam, curing of the EPS bead particles and white mold molding-filling of cooling water for cooling-die opening and white mold taking. The packaging procedure includes the steps of pouring bottom sand in the sand box to be compact in a vibration mode, scrapping flat, inserting a vertical core bar in the bottom sand, enabling the vertical core bar to be perpendicular to a bottom plate of the sand box, using the vertical core bar as the central axis to place the dried pipe fitting white mold on the bottom sand, filling dry sand in the sand box to be compact in a vibration mode, covering a polyethylene film on the sand box to wait for being poured. The lost foam casting process is reasonable in improvement, suitable for processing high-precision and high-quality grey cast iron thin wall pipe fittings and double-bell-and-spigot grey cast iron thin wall pipe fittings with lengths of above 1.5 meters.

Description

technical field [0001] The invention relates to the field of lost foam casting, in particular to a process of lost foam casting of double-socket gray cast iron thin-walled pipe fittings and a sand box for the process. 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 ...

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

Especially when the lost foam casting process is used to produce thin-walled pipe fittings with double sockets and sockets with a length of more than 1.5 meters, the core formed by the negative pressure of dry sand inside the mold tube is relatively long. The strength and rigidity of the dry sand core are destroyed, and it is easy to collapse the box, resulting in the product being scrapped

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