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Production process of casting manhole cast iron

by admin HipatiaPress (2018-09-17)

All castings, including manholes, were made in large mills called mills. Scrap steel enters the foundry, melts and blends and forms pig iron. The molding process consists of báo giá n?p gang h? ga five steps, molding, mold preparation, melting / filling, cooling and finishing.

1- Door models are carved of wood or are made of aluminum. Aluminum molds are used for large workshops because of greater durability. The designs are slightly larger than the finished manholes to allow for shrinkage when the castings cool. Each manhole cover has two molds, one for the top face of the manhole cover and one for the bottom face. The upper half of the sewer cover is usually decorated with some basic patterns, woven patterns, or concentric circles. The bottom half of the mold is simply flat, or can be designed in three-dimensional web form.
? Prepare the mold
Sand molds are made by placing two halves of the manhole cover on a box called a mold. Green sand is stuffed into the molds to create two molds. The top molds contain holes for melting iron and vents allowing the gas to escape the mold. For a drain, the vent can be created by placing a piece of wood vertically on the mold and removing it once the sand has been tucked into. Using mobile rollers allows the molten metal to be molded in multiple locations to help prevent gaps formed during the final molding process.
After the samples are removed, the bottom of the mold is a hollow image of the top and bottom of the manhole cover. The bottom and top of the mold are assembled in a large metal frame.
4- The casting is made of sandstone with a chemical resin called thermoset, which means it must be heated to become fixed. This process has several advantages, such as that the mold can be built very quickly and requires less labor. These types of molds are ideal for automation when needing to perform a large amount of work. However, conventional manholes do not need to be manufactured to the level of automation.
? Filling / filling
5. Ceramic ovens, arc furnaces, reactors, induction hobs, and crucibles are commonly used to melt steel scrap for the manufacture of cast iron. Scrap steel is placed in the furnace and melted at about 2,700 ° F (1,500 ° C).
6- The metal, the necessary flame is then added to the molten iron. The purpose of the ignition is to bond to the impurity that produces the "slag". Because slag is slightly lighter than iron, it floats on top of molten iron and can be removed.
7. Melted iron is collected into a large metal basin. Workers cast iron scraps into the sand mold. When the casting cools and contracts, the excess metal is filled in the mold. Because the temperature of the molten iron b?ng giá n?p h? ga is much higher than the temperature of the organic material in the green sand, the organic material burns and uses up all the oxygen in the mold. This prevents the oxidation of the manhole cover.
? Cooling
8- It takes about an hour and a half for the metal to cool to get out of the mold. The n?p h? ga composite complete cooling takes about a day.
9- In large foundries, cold molds and molds are placed on a furnace and shaken until all the sand is shaken. In a small foundry, the same process can be done by workers with a wire brush.
10- Handling of used sand from molds is difficult because of very large quantities. After each use, the sand is classified in the filter tower to remove all the slag that is mixed in it.
? Complete
11 - With complex casting details, finishing works is a big part of the job. But the manhole cover does not need much, mainly removing the rollers, surface rinsing, using a reamer to ensure that the lid stays flat in its frame.