JPS6134126A - Treating method for molten aluminum and its alloy - Google Patents

Abstract

PURPOSE:To improve degassing efficiency, by contriving the relation in arrangement of a porous plug and an impeller, and the impeller shape, etc. CONSTITUTION:The porous plug 16 for blowing treating gas into molten metal is set at the bottom of a molten metal treating vessel 10, and the impeller 18 is set just above the plug 16 therein with a prescribed space. Long wings 18b opposed to the plug 16 are provided radially to the impeller 18, a den 18c for dispersing babbles to spaces between the wings 18b is formed at center part thereof. Space between the impellr 18 and the plug 16 is set to 5-20mm., revolution number of the impeller 18 is set to 500-1,000rpm, Ar+0.1Cl<2> is used as treating gas, intake quantity and gaseous pressure are set to 3-15L/min, 1-5kg/cm<2> respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a molten metal processing apparatus for molten aluminum and aluminum alloys.

(Prior art) When molten aluminum and aluminum alloys are kept in the atmosphere as molten metals, gases (mainly H2) are released over time.
gas).

Therefore, when semi-continuously casting refined molten metal, the remaining molten metal is exposed to the atmosphere for a long time at the end of casting, so if it is cast as is, the ingot will contain a large amount of gas and its quality will deteriorate. A problem arises.

For this reason, conventionally, as shown in FIGS. 3 and 4, a porous plug 3 and an impeller 4 are attached to a pipe 2 in which a processing gas introduction passage 1 is formed, and the processing gas is supplied from the pipe 2. is made into fine bubbles by a porous plug 3 and blown into the molten metal, while a rotating impeller 4
A molten metal processing apparatus has been proposed in which the degassing efficiency is improved by cutting and dispersing these bubbles (see Japanese Utility Model Publication No. 56-45875).

However, since the conventional molten metal processing equipment is configured to introduce processing gas while rotating the impeller 4 through the pipe 2, it is necessary to connect a rotation motor and a processing gas supply device to the pipe 2. Because of this, there was a problem that the connection structure became complicated.

In addition, the impeller 4 has four short blades 41], . Because of this configuration, the stirring range is narrow, and therefore, in reality, most of the bubbles blown out from the porous plug 3 are caused by the impeller 41.
Since the impeller 4 is blown into the molten metal without being cut or dispersed, it is necessary to install a plurality of impellers 4 at short intervals W, which limits the improvement in degassing efficiency.

(Objective of the Invention) The present invention has been made to solve the above-mentioned conventional problems, and in particular, by making improvements to the arrangement relationship between the porous plug and the impeller, as well as the shape of the impeller, etc., the degassing efficiency can be improved. Its basic purpose is to achieve two goals.

(Structure of the Invention) For this reason, the present invention provides a porous plug that blows a processing gas into the molten metal at the bottom of a molten metal processing tank, and a porous plug that is directly connected to the porous plug in the processing tank. Impellers are installed at intervals of It is composed of

(Effects of the Invention) According to the present invention, impellers are installed at predetermined intervals directly above the porous plugs installed at the bottom of the molten metal processing tank, and the impellers are provided with long blades, and a recess is formed in the center of the blades. Because the bubbles are blown out from the porous plug, they are finely cut by the recesses and blades, dispersed over a wide area, and blown into the molten aluminum, increasing the degassing efficiency. As a result, the quality of the ingot becomes stable and the yield improves.

Furthermore, since the degassing efficiency is increased, the processing time for molten metal can be shortened, thereby improving productivity and reducing manufacturing costs.

Furthermore, since the rotation of the impeller and the supply of processing gas can be performed in separate systems, there is no need to complicate the connection structure as in the past.

Furthermore, since the degassing efficiency is high, the number of impellers is small and the size is compact, so there is less absorption of gases that are processed immediately before the continuous casting machine and after the process.

(Example) As shown in FIG. 1, the molten metal processing tank 1 () is provided with a molten metal supply port 11 at the upper left side in the figure, a molten metal discharge port 12 at the upper right side, and Discharge port 1 in treatment tank 10
A baffle plate 13 is provided near the second side, and the inside of the processing tank 10 is divided into a processing chamber 14 and a discharge chamber 15.

At the center of the bottom of the processing chamber 14 of the processing tank 10 is a porous plug 1 that blows processing gas into the molten metal in the form of fine bubbles.
6 is installed.

The processing gas (inert gas) blown from the porous plug 16 is Ar + N= + Freon.

There are Ar+CL, N2+C, C2, etc., and Ar0o and 1 cρ are particularly preferable.

The amount of suction gas is preferably 3 to 15 ρ/min; if it is less than 3, the treatment tank will not be filled with fine bubbles and the degassing efficiency will be reduced; if it exceeds 15, the bubbles will coalesce. There is a problem that the degassing efficiency decreases.

Moreover, the gas pressure is preferably 1 to 5 kg/cm2,]
If it is less than 5, there will be a problem that gas will not come out due to pressure loss within the porous plug, and if it exceeds 5, there will be a problem that bubbles will tend to coalesce and the degassing efficiency will decrease.

Directly of the porous plug 16 of the processing chamber 14, a carbon steel plate is installed at a predetermined distance from the porous plug 16 at the lower part of the rotating shaft 17 that vertically passes through the second part of the processing tank 10. The impeller 18 is removed by τ1.

This interval is preferably in the range of 5 to 20 degrees; if it is less than 5, there is a problem that the bubble diameter increases and the degassing efficiency decreases, and if it exceeds 20, the bubble dispersion by the impeller becomes insufficient. There is a problem that degassing efficiency decreases.

As shown in FIGS. 2(a) and 2(l), the impeller 18 includes a large-diameter disk-shaped seat portion 18a, and the seat portion 18a.
Long wings 1811°..., 18b are provided radially at a predetermined angle on the lower surface of the porous plug 16, facing the porous plug 16.
A recess 18c is formed in the center of each of the blades 18b, . . . , 18b to disperse air bubbles between the blades 181), .

The blades 18b, . . . , 18b are preferably long 12-blade blades or the like, in which the blade length is much longer than the blade height h.This widens the stirring range, so that fine air bubbles can be formed. The impellers can be cut and dispersed over a wide area, eliminating the need to install multiple impellers at short intervals W as in the past.

The impeller 18 is rotated by a variable speed electric motor 19 connected to the rotating shaft 17.

The rotation speed of this impeller is preferably 500 to 1000 rp+n, and if it is less than 500, there is a problem that fine bubbles cannot be dispersed throughout the treatment tank and degassing efficiency decreases.
If it exceeds 1,000, there is a problem that the dispersion of fine bubbles becomes uneven and the degassing efficiency decreases.

The table below shows the test results of a practical test conducted using the molten metal processing apparatus configured as described above.

○ Casting temperature 710-720℃ ○ Gas measurement is based on the telegas method.

1 or less margin 1 According to the above test results, the processing conditions of TES) No. 11) [Cff12 flow rate 0.002 (Nm3/h)
, A, r flow rate 1.0 (Nm'/l+), Ar pressure 1
, 5 (kg/cm2), impeller rotation speed 7 ('l
O(rpm) ] had the highest degassing efficiency, at 59%.

[Brief explanation of drawings]

Figure 1 is a side view of the molten metal processing apparatus according to the present invention, and Figure 2 (
a) is a bottom view of the impeller, Fig. 2(b) is Fig. 2(a)
3 is a side view of a conventional molten metal processing apparatus, and FIG. 4 is a sectional view showing the structure of the impeller and porous plug shown in FIG. 3. 10... Molten metal processing tank, 14... Processing chamber, 1
6... Porous plug, 17... Rotating shaft,
1. impeller, 181]... feather, 18
c... recess, 19... electric motor, L...
interval. Patent applicant: Kobe Steel, Ltd.
Entered patent attorney, previously mentioned 葆 and 2 others □-/Yari), X ~
, ♂l'+14+-1 〒Ej (□i-1'
11i(゛ ・ 1゛・ ・ ・ ・
・□Figure 2 (0) ″″ □Pi l□ Figure 3

Claims (2)

[Claims] (1) A porous plug for blowing processing gas into the molten metal is installed at the bottom of the molten metal processing tank, and an impeller is installed in the processing tank directly above the porous plug at a predetermined distance from the porous plug. Molten aluminum and aluminum alloy, characterized in that the impeller is provided with long blades facing the porous plug in a radial manner, and a recess is formed in the center of the blade to disperse air bubbles between the blades. molten metal processing equipment. (2) The distance between the above impeller and the porous plug is 5 to 2
0 mm, and the rotation speed of the impeller is 500 to 100.
While setting the processing gas to 0 rpm, Ar+0.1Cl
_2, the suction gas amount is 3 to 15 l/min, and the gas pressure is 1 to
The molten aluminum and aluminum alloy molten metal processing apparatus according to claim 1, wherein the weight is set to 5 kg/cm^2.