JP5414375B2 - Lance pipe - Google Patents

Description

  The present invention relates to a lance pipe for introducing blown gas into molten aluminum.

  In a holding furnace, in order to remove hydrogen gas and impurities in the molten aluminum, a degassing process is performed in which a blowing gas such as nitrogen gas is introduced into the molten metal, and the hydrogen gas and impurities are blown into the gas bubbles. Has been done.

In order to introduce the blown gas into the molten aluminum, for example, an L-shaped cylindrical lance pipe or the like is used.
As such a lance pipe, for example, a metal pipe body covered with a porous refractory material, or a tip surface part immersed in a molten metal is made of an amorphous refractory containing alumina, magnesia and zirconia. (See Patent Documents 1 and 2 below).

  The material for the lance pipe is 2 to 10% by weight of clay, 1 to 8% by weight of alumina cement having an alumina content of 70% by weight or more, and the balance is made of a material containing a refractory aggregate. There is a fixed refractory composition in which 0.3 to 1.5% by weight of metallic aluminum having a particle size of 100 μm or less and a purity of 99% by weight or more is blended (see Patent Document 3 below).

JP 2008-7848 A Japanese Patent Laid-Open No. 11-256221 JP 2002-274962 A

Since the lance pipe is immersed in a high-temperature molten aluminum, it is required to have excellent heat resistance, corrosion resistance, thermal shock resistance (spalling resistance), and the like.
Conventional lance pipes are mainly made of ceramics or carbon, but ceramic materials are excellent in heat resistance and corrosion resistance. However, if they are immersed in molten metal without preheating, they are prone to cracking due to thermal shock. The carbon material has a problem that it is weak in strength and easily damaged. In particular, the tip of the lance pipe was easily damaged.
For this reason, the product life of the lance pipe is short, the frequency of replacement is high, and the cost is high.

  Therefore, an object of the present invention is to provide a lance pipe that can be used economically.

The lance pipe of the present invention is a lance pipe that introduces a gas blown into molten aluminum. On the tip side of the gas inlet pipe , each surface is made of a porous material, and a cylindrical tip porous portion with both end surfaces closed is removable. The material strength ratio of the gas introduction tube to the tip porous portion is set to 20 to 500.

  It is preferable that the gas introduction tube and the tip porous portion can be joined by an inorganic adhesive and / or screw processing.

  Silicon nitride ceramics, sialon ceramics, silicon carbide ceramics, and silicon nitride bonded silicon carbide refractories can be used as the material for the gas introduction pipe.

  For the tip porous portion, porous carbon having an average pore diameter of 20 μm to 200 μm and a porosity of 30 to 50% can be used.

  In the lance pipe of the present invention, the gas introduction tube and the tip porous portion can be attached and detached, and the strength of the material of the tip porous portion is increased. It is possible to economically replace only the porous part.

  The molten aluminum referred to in the present invention includes molten aluminum alloy.

It is the disassembled perspective view which showed one Embodiment of the lance pipe of this invention. It is sectional drawing of the lance pipe of FIG.

  Hereinafter, an embodiment of the lance pipe of the present invention will be described. However, the scope of the present invention is not limited to this.

  As shown in FIG. 1 or 2, the lance pipe 1 according to an embodiment of the present invention has a shape in which a bottomed cylinder is L-shaped, and includes a gas introduction pipe 2 and a tip porous portion 3 joined thereto. ing.

The gas introduction pipe 2 is formed in a cylindrical shape and has a configuration in which the blown gas flows inside, and can blow the blown gas into the tip porous portion 3.
The tip porous portion 3 is formed in a cylindrical shape with both end faces closed, and each face is made porous, and the blown gas flowing from the gas introduction pipe 2 permeates each face from the inside and passes through the molten metal. It is configured to be blown inside.

The gas introduction tube 2 has a material strength ratio (gas introduction tube strength / tip porous portion strength) to the tip porous portion 3 of 20 to 500, preferably 50 to 200. By setting the material strength ratio within this range, the gas introduction tube 2 is not damaged when the tip porous portion 3 is removed. These strengths can be adjusted by selecting the material.
The material strength can be measured according to a 3-point bending strength test, JIS R2213.

  The gas introduction pipe 2 is preferably formed of ceramics and the tip porous portion 3 is preferably formed of porous carbon. Examples of the ceramic include silicon nitride ceramics, sialon ceramics, silicon carbide ceramics, and silicon nitride bonded silicon carbide refractories.

The tip porous portion 3 preferably has an average pore diameter of 20 μm to 200 μm and a porosity of 30 to 50%. By setting it within this range, the bubble discharge stability is improved.
The average pore diameter can be measured by a mercury porosimeter, and the porosity can be measured by the Archimedes method.

On the distal end side of the gas introduction pipe 2, a thread of the thread portion 4 is formed on the outer peripheral surface, and a circular hole having a thread groove of the thread portion 4 is formed on the peripheral surface of the distal end porous portion 3. These are fastened so that the gas introduction tube 2 and the tip porous portion 3 can be detachably joined. Thus, by providing a screw part so that it can join, gas leakage from a joined part is lost.
In this embodiment, the gas introduction tube 2 and the tip porous portion 3 are joined by the screw portion 4, but joining using an inorganic adhesive made of alumina-silica or the like or joining by fitting may be used. You may join combining suitably the joining by a part, the joining by an inorganic adhesive agent, and the joining by fitting.

  The thickness of the gas introduction tube 2 is preferably 5 mm to 20 mm, and the thickness of the tip porous portion 3 is preferably 10 mm to 50 mm.

  The gas introduction pipe 2 can be formed by cold isostatic pressing, compaction molding, extrusion molding, casting molding, or the like. The tip porous portion 3 can be formed by cold isostatic pressing, press molding, extrusion molding, or the like. Can be formed.

  In the lance pipe 1, the gas introduction pipe 2 is made of a material stronger than the tip porous portion 3, so the gas introduction pipe 2 can be used repeatedly over a long period of time, and these are detachable. The tip porous portion 3 that is easily damaged can be easily replaced.

  Although the lance pipe shown in FIG. 1 or FIG. 2 is formed in an L shape, a T type in which a gas introduction pipe is connected in the vicinity of the middle of the tip porous portion or a gas in the tip porous portion in a straight line. It can also be formed into a straight type connected to the introduction pipe, or a square shape where the tip porous portion is connected to the gas introduction pipe at a predetermined angle.

  Hereinafter, the present invention will be described more specifically based on examples. However, the scope of the present invention is not limited to this example.

  Using the materials described in Table 1 and Table 2 below, the gas introduction pipes of Examples 1 to 3 and 7 and Comparative Examples 1 to 5 were prepared to have an inner diameter of 20 mm and a thickness of 10 mm. It was made of porous carbon with an inner diameter of 30 mm and a thickness of 15 mm. Further, the gas introduction pipes of Examples 4 to 6 and 8 to 11 were prepared to have an inner diameter of 20 mm and a thickness of 5 mm, and the tip porous portion was made of porous carbon to have an inner diameter of 25 mm and a thickness of 15 mm.

(Strength)
The strength was measured according to a three-point bending strength test, JIS R2213.

(Joining)
Screw processing was performed by lathe processing. When screw processing was not performed, it joined by inorganic adhesive or fitting.

(Average pore size)
The average pore diameter was measured with a mercury porosimeter.

(Porosity)
The porosity was measured by Archimedes method.

(test)
Using the lance pipes of Examples 1 to 11 and Comparative Examples 1 to 5, tests were conducted for breakage during tip replacement, aluminum corrosion resistance, gas leakage from the joint, and bubble release stability.

(Damage when replacing tip)
The lance pipe is immersed in molten aluminum at 750 ° C. for 1 week while flowing the blow-in gas, cooled to room temperature, the gas introduction part and the tip porous part are removed, and the gas introduction part is not damaged at that time. It was confirmed visually. The case where damage was not confirmed was evaluated as “◯”, and the case where damage was confirmed was evaluated as “x”.

(Aluminum corrosion resistance)
While flowing the blowing gas, immerse the lance pipe in molten aluminum at 750 ° C for one week, take it out and cool it to room temperature three times. If there is no break, "○". If it breaks, "X". As evaluated.

(Gas leakage from the joint)
The lance pipe was immersed in the water tank, air was fed at 20 L / min, and it was visually confirmed whether gas was leaking from the joint. The case where gas leakage was not confirmed was evaluated as “◯”, and the case where gas leakage was confirmed was evaluated as “x”.

(Bubble release stability)
The lance pipe was immersed in the water tank, air was fed at 20 L / min, and the release of bubbles was visually confirmed. The case where bubbles were uniformly discharged from the entire porous portion was evaluated as “◯”, and the case where bubbles were unevenly distributed was evaluated as “x”.

(Comprehensive evaluation)
There is no breakage at the time of tip replacement, and among the other three evaluation items, two or more are “、 ２”, and there is no breakage at the time of tip replacement, and one of the other three evaluation items is one. If the case is “◯”, there is damage when the tip is replaced, and among the other three evaluation items, if one or more is “◯”, there is damage when replacing the tip, and the other three evaluation items The case where all of was x was evaluated as “x”.

(result)
Examples 1 to 11 were comprehensive evaluations “◎” or “◯”, and were good results.
On the other hand, Comparative Examples 1 to 5 had an overall evaluation of “Δ” or “x”, which was an undesirable result.
From the results of Examples 1 to 11, if the material strength ratio of the gas introduction tube to the tip porous portion is in the range of 25 (Examples 1 to 3) to 475 (Example 4), the gas introduction tube It was confirmed that there was no damage.
From the results of Comparative Examples 1 to 5, it was confirmed that the gas introduction pipe was damaged when the material strength ratio was 6 or 5.
From these results, it is considered that if the strength ratio of the gas introduction tube to the tip porous portion is in the range of 20 to 500, the gas introduction tube is not damaged during tip replacement.

1 Lance pipe 2 Gas introduction pipe 3 End porous part 4 Screw part

Claims (4)

Formed in the lance pipe for introducing a gas blown into the molten aluminum, the distal end side of the gas inlet, each surface is made of a porous, cylindrical tip porous portion of closing the both end faces is provided detachably on L-type and Yes, the lance pipe in which the material intensity ratio of the gas inlet tube for distal porous portion 20-500.   The lance pipe according to claim 1, wherein the gas introduction pipe and the tip porous portion are joined by an inorganic adhesive and / or screw processing.   The lance pipe according to claim 1 or 2, wherein a silicon nitride ceramic, a sialon ceramic, a silicon carbide ceramic, or a silicon nitride bonded silicon carbide refractory is used as a material of the gas introduction pipe.   The lance pipe according to any one of claims 1 to 3, wherein porous carbon having an average pore diameter of 20 µm to 200 µm and a porosity of 30 to 50% is used for the tip porous portion.

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