JPH0499118A - Vacuum reaction vessel - Google Patents

Abstract

PURPOSE:To increase gas-liquid interface area without blowing a gas and to improve a degassing reaction velocity by reducing atmospheric pressure in contacting with the free surface of a molten metal flowing through on adjacent trough state flowing passage of the molten metal. CONSTITUTION:Main body 11 of a vacuum reaction vessel 10 is wholly formed as the rectangular basin shape, and by covering the vessel 10 with a cover 18, the inner part of the treating system is held airtightly, and further, the gas exhaust duct 19 is arranged at the suitable position in the cover 18. The inner part of this main body 11 is sectioned into the trough-state molten metal flowing passage 15 with plural partitions 12 and formed so that the flowing passage 15 at the downstream side is surely adjacent to the flowing passage 15 at the upstream side across the partition 12 from an inlet of flow 13 to an outlet of flow 14. The pressure in this vacuum reaction vessel 10 is reduced to about 1Torr, and the molten steel 2 is supplied into the vessel 10 and allowed to flow slowly in the flowing passage 15 at about 2.5m/min flowing velocity. [C] in the molten steel 2 is sufficiently reacted with [O] under the reduced pressure and a large quantity of carbon monoxide gas 4 is generated. By this method, the free surface A of the molten steel is widened and degassing reaction is efficiently executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a vacuum reaction vessel for degassing and refining molten metal under reduced pressure.

[Conventional technology] Recently, there has been an increase in demand for ultra-low carbon steel and ultra-low nitrogen steel with carbon and nitrogen contents adjusted to extremely small amounts, and degassing refining methods have been developed as a technology for quickly and stably melting these steels. Attention has been paid. The degassing refining method introduces molten steel into a vacuum reaction vessel,
This is a refining technology that degasses molten steel under reduced pressure. Although there are various types of vacuum reaction vessels, there is a need to further improve the reaction rate within the vessels in order to cope with an increase in throughput.

A conventional vacuum reaction vessel, like an RH degassing tank or a DH degassing tank, has a vertical cylindrical main body and has a dip tube in the lower tank of the main body. In the case of degassing treatment, molten steel is sucked up into a tank through a dipping pipe, splash is generated under reduced pressure, and [C], [N], etc. in the molten steel are gasified and then exhausted.

[Problem to be solved by the invention] However, since conventional vacuum reaction vessels have a vertical cylindrical shape, there is a certain limit to increasing the surface area (free surface area), and if this continues, the reaction rate will decrease. It is relatively small, and it is generally difficult to improve the degassing rate, etc. For this purpose, gas is blown into the molten steel in the tank to increase the gas-liquid interface area and improve the degassing rate. but,
There is a drawback that the blowing of gas causes a large amount of wear and tear on the refractories, and the unit consumption of the refractories increases. In particular, when ultra-low carbon steel or ultra-low nitrogen steel is melted, the refractory lining of the container suffers from significant erosion, and the refractory lining must be frequently repaired, resulting in high costs.

This invention was made in view of the above circumstances, and an object of the present invention is to provide a vacuum reaction vessel that can increase the gas-liquid interface area and improve the reaction rate without blowing gas. do.

[Means for Solving the Problems] The degassing reaction rate under reduced pressure is controlled by the free surface area A of the molten metal in the container and the amount V of the molten metal, as shown in the following equation (1).

-d c/d t -KX (A/V)X ([C
ko - [C ko, ) ... (1) Above (
As is clear from equation 1), as the free surface area A of the molten metal increases and as the amount V of the molten metal decreases, the degassing reaction rate increases. By the way, when the amount V of molten metal is reduced, the amount of heat loss through the passage walls increases, and the temperature of the molten metal drops significantly. Therefore, the amount of molten metal cannot be reduced below a certain amount. For this reason, it is conceivable to increase the free surface area A of the treated molten metal to increase the degassing reaction rate.

In order to increase the free surface area of the molten metal to be treated and increase the degassing reaction rate, the inventors conducted various studies on the shape of the degassing reaction tank, and as a result, they designed a wide and shallow molten metal flow path. I came up with the idea of forming it in the shape of a gutter.

The vacuum reaction vessel according to the present invention has a trough-like molten metal flow path through which molten metal having a free surface flows, and a pressure reducing means for reducing the pressure of the atmosphere in contact with the free surface of the flowing molten metal, It is characterized in that the flow paths are adjacent to each other.

[Function] In the vacuum reaction vessel according to the present invention, since the molten metal passage is formed in the shape of a gutter, the ratio of the free surface area A to the molten metal JIV increases, and the degassing reaction rate increases.

As shown in FIG. 3, when the molten metal 2 flows slowly through the trough-like passage 15, the amount of molten metal becomes relatively small because the passage 15 is shallow, but the molten metal surface 3, which forms the gas-liquid interface, Since it is wide, the free surface area A becomes large, and [C and [0] in the molten metal react and a large amount of carbon monoxide gas 4 is generated.

Furthermore, since the molten metal passages 15 are arranged adjacent to each other, there is little heat loss through the walls of the passages, and a drop in the temperature of the molten metal 2 is prevented.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

Fig. 1 is a plan view schematically showing a vacuum reaction vessel according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of a molten metal passage in the vacuum reaction vessel, and Fig. 3 is a molten metal passage in the vacuum reaction vessel. FIG.

The main body 11 of the vacuum reaction vessel 10 is entirely formed in the shape of a rectangular basin, lined with a refractory material, and covered with an iron shell on the outside. The main body 11 is covered with a lid 18 to keep the inside of the processing system airtight. An exhaust duct 19 is provided at a suitable location on the lid 18, and gas within the processing system is exhausted through the exhaust duct 19.

The inside of the main body 11 is partitioned into a crank shape by a plurality of partitions 12, and a gutter-like molten metal passage 15 is formed from an inlet 13 to an outlet 14.

That is, it is formed so as to be adjacent to the downstream passage 15 or the upstream passage 15 with the partition 12 in between. Each of the inlet 13 and the outlet 14 is connected to a molten steel ladle (
It is connected to a supply section and a return section (not shown). The molten steel supply section is provided with a device (not shown) that applies a force to the molten steel from the molten steel ladle toward the inlet 13.

The main body 11 of the vacuum reaction vessel has a size of 4 m in length x 4 m in width, and the flow path 15 has a width of 1 m and a depth of about 014 m.

Next, a case will be described in which ultra-low carbon steel is melted using the vacuum reaction vessel 10 described above.

The molten steel 2 before treatment is in an undeoxidized state and has a [C] content of about 30
0ppIll, [0] amount is approximately 6001)I)II.

The molten steel ladle is carried into a degassing facility, and the molten steel supply section and return section are connected to the inlet 13 and the outlet 14, respectively. The pressure inside the vacuum reaction vessel 10 is reduced to about 1 Torr, and the molten steel in the pot is supplied to the vessel 10. At this time, the molten steel 2 passes through the passage 1
Since the flow is carried out slowly at a flow rate of 2.5 m/min in the molten steel 5, the [C] in the molten steel fully reacts with [0] under reduced pressure while flowing, and a large amount of -carbon oxide gas 4 is produced. Occur. Furthermore, since the flow passages 15 are adjacent to each other on the upstream and downstream sides, the amount of heat radiated from the entire processing system is small.

In Figure 4, the horizontal axis shows the flow distance, and the vertical axis shows the molten steel [C]
It is a graph diagram showing the results of sampling and investigating the transition of the decarburization reaction at each part of the gutter. As is clear from the figure, the amount of [C] can be reduced to 15 ppm, the level of ultra-low carbon steel, with decarburization treatment of 15 m, and under the conditions of this example, decarburization treatment takes only 6 minutes.

In the above embodiment, only one trough-like molten metal passage was provided, but the present invention is not limited to this, and the structure may be such that two or three tiers of passages are stacked. When the trough-like flow path has a multi-stage structure, the amount of heat loss of the molten steel is further reduced.

[Effects of the Invention] According to the present invention, since the molten metal flow path is formed in the shape of a gutter, the free surface area A of the treated molten metal can be widened, and the degassing reaction rate can be dramatically increased.

Therefore, ultra-low carbon steel and ultra-low nitrogen steel can be produced in a short time.

In addition, in order to reduce the amount of molten metal V, the depth of the molten metal is made shallow and the flow velocity in the passage is slowed down, which reduces wear and tear on the refractory lining and reduces the unit consumption of refractories. .

Furthermore, since the gas that was blown in to increase the gas-liquid interface area can be made unnecessary, operating costs can be reduced.

Furthermore, since the molten metal passages are arranged adjacent to each other, the amount of heat loss is reduced, and the temperature drop of the molten metal can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a plan view schematically showing a vacuum reaction vessel according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of a molten metal passage in the vacuum reaction vessel, and Fig. 3 is a molten metal passage in the vacuum reaction vessel. FIG. 4, which is a longitudinal cross-sectional view of the road, is a graph diagram for explaining the effects of the embodiment of the present invention. 10; vacuum reaction vessel, 12. Partition, 13; Inlet, 1
4. Outlet, 15. Molten metal flow path, Applicant's representative Patent attorney Takehiko Suzue Figure 3 Wakukei distance (m) Figure 4

Claims (1)

[Claims] a trough-like molten metal passageway through which molten metal flows, having a free surface;
1. A vacuum reaction vessel comprising a pressure reducing means for reducing the pressure of an atmosphere in contact with a free surface of flowing molten metal, and wherein the molten metal flow paths are adjacent to each other.