RU2100142C1 - Process of manufacture of low-carbon steel ingots - Google Patents

Abstract

FIELD: foundry, manufacture of low-carbon ingots of increased purity of cleaning from gases and endogenous nonmetal inclusions. SUBSTANCE: process is based on deoxidizing capability of carbon while removing reaction products thanks to reduction of their partial pressure in system in agreement with known dependence $$$ since reduction of partial pressure P<Mv>co<D> leads necessarily to decrease of oxygen and carbon dissolved in metal. In this case iron is reduced and carbon oxide is removed from system. Ingot mould has shape of bottle and bottom casting makes it possible to provide for tight connection to vacuum pump. Suction pumps are switched on from start of filling of ingot moulds. Process does not require any changes of melting and casting technology. Process can be used to manufacture of specifically low-carbon steel, to cast ingots with large relation of length to cross-section as billets for rolling. EFFECT: increased efficiency of process.

Description

 The invention relates to methods for manufacturing ingots of low-carbon steel of high purity from gases and endogenous non-metallic inclusions.

 For the manufacture of parts by stamping and particularly complex drawing, low-carbon boiling steel is used, since it is more plastic than quiet due to the low carbon content and the absence of silicon.

 The main disadvantage of the finished sheet of this steel is the delamination associated with the presence of non-metallic inclusions and dissolved gases. In this case, boiling steel is poured into the through molds with the flow of metal from above or from below (by siphon method). Boiling steel is deoxidized in the furnace or in the ladle only with manganese. The quality and structure of the boiling steel ingot depends on the self-deoxidation process during casting, due to the boiling process of the metal in the mold. The boiling intensity is regulated by the addition of an intensifier or deoxidizer. After boiling, the top of the ingot is covered with a heavy lid or corked in another way. This is currently accepted technology.

For the purpose of additional purification of metal from gases and non-metallic inclusions, various methods are known for out-of-furnace treatment of liquid metal in vacuum [1] In a vacuum, the deoxidizing ability of carbon increases. The gaseous deoxidation product is removed, which ensures a cleaner steel. It is recognized that evacuation gives the greatest effect in the treatment of boiling steel [2]
The following vacuum treatment methods are known:
degassing in the bucket;
portion degassing (DH process);
circulation degassing (RH-process);
Jet degassing during overflow from bucket to bucket and other more complex processes [3]
In all these cases, the boiling steel turns to quiet before casting begins.

 The disadvantages of all these methods is the need for a special vacuum chamber, additional time and temperature of the metal for processing, as well as secondary oxidation during filling of the ingot.

 Known methods of evacuating a metal stream when filling a mold in a specially equipped chamber are used to process single ingots, and a wide cone of dispersion of the metal stream is obtained, which is also a disadvantage.

There is also a known method of manufacturing steel ingots, involving the evacuation of boiling steel during the filling of molds of bottle type siphon and in the process of crystallization of the ingot by hermetically connecting the top of the molds through covers (or plugs) with a vacuum system [4]
This method does not allow to obtain ingots in a stream of unlimited quantities with a high degree of purification from gases and non-metallic inclusions.

 The objective of the invention is the expansion of technological capabilities of the method, obtaining cleaner from gases and non-metallic inclusions, more ductile metal in the stream of an unlimited number of ingots, eliminating the disadvantages that occur when using known methods of out-of-furnace treatment of boiling metal.

 In FIG. 1 shows a device for implementing the method; in FIG. 2 is a side view of a mold connected to an evacuation unit; in FIG. 3 same, top view.

 The essence of the method lies in the fact that boiling steel melted by conventional technology is poured into ingots under vacuum directly in the process of filling molds of the bottle type through siphon wiring. The prepared molds of the bottle form are connected through a cast-iron stopper 2 to the evacuation unit through a permanent wiring 3. A group of molds, simultaneously filled with metal, are included in the vacuum system from the moment the filling starts. The capacity of the evacuation pump is at least 4.0 liters per second of generated gases per ton of simultaneously processed metal. After filling the molds and holding for 5 to 20 minutes, depending on the weight of the ingot, the vacuum is turned off.

 The method allows to simplify smelting somewhat, since it does not require a supply of temperature during processing, a special vacuum chamber is not needed, since it is combined with a mold, it does not require changes in the usual technology for steel smelting and casting, and it eliminates secondary metal oxidation during casting. Permanent wiring from the vacuum pump unit allows you to process an unlimited number of ingots.

 The method can be used to obtain a particularly low-carbon metal by adjusting the depth of the vacuum, as well as for casting ingots with a large ratio of height to cross section as a blank for hire.

Claims (1)

 A method of manufacturing low-carbon steel ingots, including evacuation of boiling steel during the filling of molds of bottle type with a siphon and in the process of partial crystallization of the ingot, by tightly connecting the top of the molds through plugs with a vacuum system, characterized in that during the steel evacuation process the average pumping speed of the resulting gases is maintained not less than 4 l / s for each ton of simultaneously processed metal.

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