SU596361A1 - Method of centrifugal casting of iron tubes - Google Patents

Description

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This invention relates to the field of ferrous metallurgy, in particular, to the production of cast iron pipes.

A known method for producing centrifugal pipes from gray cast iron, in which the cast iron smelted in a cupola is sewn into a rapidly cooled rotating metal form with one jet 3

The known method does not make it possible to produce pipes with the same structure throughout the wall thickness, since the first metal layers harden to form cement due to intense water cooling, and the internal ones that are not subjected to intensive cooling harden to form a perlite ferrite structure.

There is also known a method for producing centrifugal tubes, which includes pouring metal with two jets — feeding one jet directly onto the mold surface and the other onto the melt layer formed by the first jet 2.

However, this method of casting also does not allow obtaining pipes with the same structure throughout the wall thickness, as it is characterized by a high rate of crystallization of the metal flooded with the first jet. Under these conditions, a cement-peritoneous structure is formed in the outwardly thick metal. In usual short-term annealing, the cementite disintegrates, and graphite inclusions acquire a compact form, similar to the form of carbon of annealing ductile iron. This explains the high strength properties of the outer layer of pipes having a pearlite structure after annealing.

The metal of the layer formed by the second stream is deprived of such a means of stabilizing carbides as the high rate of crystallization, as it falls on the molten metal of the first layer. After crystallization, it has a perlite-ferritic structure, which, after annealing, turns into a ferritic one with large inclusions of lamellar graphite. Structural heterogeneity of cast iron affects the mechanical properties of pipes.

The closest in technical essence is a method of centrifugal casting of cast-iron pipes, which includes feeding the cast iron of the same composition into the form with two jets with a predetermined consumption of one of them from the total consumption of metal and introducing additives into the first of the jets.

The disadvantage of this method is the poor mechanical properties of the cast pipes.

The purpose of the invention is to improve the mechanical properties of pipes by equalizing their structure during the casting process.

This goal is achieved by the fact that carbide stabilizers are used as additives, and they are introduced into the second jet.

The metal consumption for casting the first layer of pipes is set within 40-60% of the total metal consumption. During the formation of the outer layer, the thickness of which is more than 60% of the pipe wall, it does not undergo a stabilizing intensive cooling throughout the entire core: a bin, and - during the formation of this rylomee. 40% :; metal, the second layer is tested / not; only exposure to SiC BOpeiata; . stabilizers,: but - and effects of - water cooling, .pch 5 / bringing a stable carbide, e: device. annealing .

To carry out the method of obtaining centrifugally cast I pipes in a cupola or induction furnace, sulfur iron is smelted. Then, in a separate container, a part of smelted / cast iron (6040%) is treated with stabilizers a can (chrome, tungsten, molybdenum, etc.). A part of smelted cast iron (40-60%) and cast iron treated with a stabilizer of carbides is cast separately along a chute with a partition. Cast iron stabilizer carbide can be processed on the gutter.

Using the described method improves the quality of pipes, i.e. improves their mechanical properties by equalizing their structure in the process of pouring and reduces the metal intensity of pipes by 10%, which causes an annual effect in the amount of 150,000 rubles.

Claims (2)

1.Ivanov.G. et al., Production of Cast Iron Pipes, M., Metallurgists, 1975, p. 104-116. 2. German patent number 576216, cl. In 22.D 13/02, 1933.