JPS61259868A - Production of nozzle for casting - Google Patents

Abstract

PURPOSE:To extend the life of a casting nozzle having high corrosion resistance and strength by sticking a refractory slurry by a drain casting method to the inside wall surface of said nozzle to a prescribed thickness thereby providing spalling resistance to the inside wall surface and adding also an effect of shielding heat thereto. CONSTITUTION:The hydrated refractory slurry consisting essentially of the pulverous powder of alumina or silica is filled in the calcined nozzle for casting consisting of the high corrosion-resistant and high-strength material such as high alumina, high alumina carbon or high zirconia carbon and is drained after the specified time to form the sticking layer of the prescribed thickness on the inside surface of the nozzle. The layer is thereafter dried or calcined. The fire resistance and spalling resistance which are the disadvantages of the above- mentioned nozzle material are improved and the effect of heat insulation is added by the gaps between the inside wall surface and the slurry, by which the nozzle life is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a casting nozzle that improves spalling resistance without impairing the corrosion resistance of the casting nozzle.

[Prior Art] Since a casting nozzle has a cylindrical shape, rapid heat is applied to the inner wall surface of the nozzle at the start of casting, and thermal stress generated due to a difference in thermal expansion is applied to the outside of the nozzle. Therefore,
It has the drawback of being very easy to break.

Therefore, when a casting nozzle is used for casting molten metal, it is necessary to use a highly corrosion-resistant material for the casting nozzle to ensure stable operation.

[Problems to be solved by the invention Generally speaking, the corrosion resistance and spalling resistance of refractories have a contradictory relationship.0 For example, increasing the amount of silica in a refractory reduces the coefficient of thermal expansion and improves spalling resistance. However, if the strength is increased structurally, the corrosion resistance will be improved, but at the same time, the elastic modulus will increase proportionally, so the spall resistance will deteriorate.

Due to this relationship, the application of highly corrosion resistant materials to maintain spall resistance has been severely restricted.

In order to solve the above problems, a method has been proposed in which the slurry is deposited on the inner wall surface of the nozzle by electrodeposition casting.
This method applies a direct current to the slurry and causes the particles to adhere to the mold by electrophoresis, which is very expensive and cannot be applied to common nozzles for casting molten metal. .

In addition, this electrodeposition casting method has excellent filling properties, and has strong corrosion resistance itself, but since it is integrated with the inner wall surface, it has the effect of improving spalling resistance as a separate structure, and has excellent spalling resistance due to its insulation properties. There were drawbacks such as difficulty in achieving improvement effects.

That is, the current situation is that it is not possible to dramatically improve corrosion resistance in order to maintain spalling resistance.

Means for Solving Problem E] In order to solve the above problems, it is possible to improve the spall resistance at a low cost by performing secondary treatment of sludge on the refractory by a sludge removal method, and also to improve the spall resistance. It has become possible to apply highly corrosion-resistant materials, and it has been discovered that corrosion resistance can be significantly improved, leading to the completion of the present invention.

That is, the present invention provides a method for manufacturing a two-layer casting nozzle, which comprises depositing a refractory slurry to a predetermined thickness on the inner wall surface of the casting nozzle by a slurry removal method.

[Function] The two-layer casting nozzle according to the present invention improves the spall resistance of the casting nozzle body due to the heat insulating effect of the layer of refractory slurry.

The slurry removal method used in the present invention is to watertightly close the lower end of a casting nozzle made of a material with high corrosion resistance and high strength, then inject slurry into the nozzle, and when the slurry has adhered to a predetermined thickness, the remaining slurry will be removed. It consists of discharging. The adhesion thickness of the slurry can be arbitrarily changed by adjusting the viscosity of the slurry.

Although the above-mentioned sludge removal method has a lower filling rate than the conventionally proposed electrodeposition casting method and has a porous structure, the corrosion resistance is slightly inferior, but the spalling resistance improvement effect due to the heat insulation property is large.

Furthermore, since the degree of adhesion between the slurry and the inner wall surface of the casting nozzle is not so good, a gap appears between the inner wall surface and the slurry, and the slurry and the inner wall maintain a relationship as a separate structure.

This gap blocks the rapid heat generated at the start of casting and prevents it from propagating.This heat blocking effect is also added, and the effect of improving the spalling resistance of the casting nozzle manufactured according to the present invention becomes even greater.

Therefore, if the method of the present invention is used, even if a highly corrosion-resistant material such as a high alumina material, a high alumina-carbon material, a high zirconia-carbon material, or a high-strength material is used in the casting nozzle, there will be no thermal spalling at the start of casting. It is durable enough.

Any refractory material that can be turned into slurry can be used as the refractory slurry in the method of the present invention, but there are problems with the productivity and cost of producing the slurry, and the slurry is melted and mixed into the molten metal in the early stages of casting. Therefore, it is preferable to consider the operating conditions to be used when making a selection.

In the method of the present invention, the slurry is poured into a nozzle molded body for casting. The molded body is usually a fired product, but it can also be poured into a base and fired. Further, it is possible to cast the product into a fired product and remove the slurry and then re-fire it, or to just pour it into the fired product and dry it, which can be selected as appropriate depending on the purpose.

As the thickness of the slurry increases, the effect of improving spall resistance increases, but in order to increase the thickness of the inner wall surface, the slurry must remain in the casting nozzle for a long time or be treated to increase its viscosity. Otherwise, operations such as heating the casting nozzle are required, which reduces the productivity of slurry production.

Therefore, it is preferable to appropriately select the thickness depending on the manufacturing aspect and the required degree of improvement in spall resistance.

[Example] The present invention will be further explained with reference to Examples below.

For the injection nozzle, a mixture of alumina raw material + atomized clay was made using a friction press into an outer diameter of 145 mmφ x inner diameter of 65 mmφ x height of 180 m.
It is molded into a nozzle shape of
It was fired at 600°C. The resulting insert nozzle had the component ratios listed in (A) and (B) in Table 1 below.

The characteristics of the obtained insert nozzle are also listed in Table 1.

and 1 Takumi L 45% by weight of zircon fine powder of 325 mesh or less, 50~
A slurry consisting of 45% by weight of 100 mesh zircon grains and 10% by weight of water was injected into the inner hole of an insert nozzle having the component ratio (B), and after standing for 5 minutes, the remaining slurry was discharged.

The resulting insert nozzle was coated with a fire-resistant slurry having a component ratio (P) shown in Table 1 to a thickness of 3 mm.

Various properties of the obtained insert nozzle are also listed in Table 1.

Insert nozzle (a) An insert nozzle having the component ratio (A) shown in Table 1 was used for continuous casting of steel, but casting was discontinued during 3 of the planned 5 series due to melting.

(b) An insert nozzle with the component ratio (B) in Table 1 was used for casting steel, but vertical cracks occurred at the start of casting.
Couldn't use it.

(c) When the insert nozzle manufactured in Example 1 was used for continuous casting of steel, no cracking occurred at the initial stage of casting, and it could withstand up to nine continuous castings.

Air seal pipe (i) Add 10% pitch to a composition containing 43% alumina, 30% silica, 5% silicon carbide, and 20% graphite.
After adding and kneading, rubber press (1500kg/0m
2) Outer diameter 200mmφ x inner diameter 1001φ x height 10
A nozzle of 00m+++ was molded, packed in coke please, and fired at 1100°C in a tunnel kiln to obtain an air seal pipe. This air seal pipe had the component ratio (C) shown in Table 1.

(ii) Add 10% phenol to a composition consisting of 73% alumina, 6% silica, 3% silicon carbide, and 18% graphite.
% added and mixed, rubber press (1500kg/a
m2) outer diameter 2001φ x inner diameter 1001φ x height 10
A nozzle with a diameter of 0.00 mm was molded, packed in a coke pleat, and fired at 1100° C. in a tunnel kiln to obtain an air seal pipe. This air seal pipe had the component ratio (D) shown in Table 1.

The properties of the obtained air seal pipes (C) and (D) are also listed in Table 1.

200 mesh or less fused silica 80% by weight and water 20%
A slurry consisting of % by weight was injected into the inner hole of an air seal pipe having a component ratio (D), and after standing for 10 minutes, the remaining slurry was discharged.

The obtained air seal pipe has the component ratio (Q>
A fire-resistant slurry with a thickness of 41 mm was deposited.

Various properties of the obtained air seal pipe are also listed in Table 1.

Air seal pipe (a) When an air seal pipe having the compounding ratio (C) shown in Table 1 was used for the molten steel between the ladle and the tundish, the immersion part was fused in the middle of 3 of the planned 4 series, so casting was stopped.

(b) When an air seal pipe having a blending ratio (D>) shown in Table 1 was used, vertical cracking occurred at the start of casting and casting could not be carried out.

(e) When the air seal pipe manufactured in Example 2 was used, no spalling occurred and it could withstand up to 12 continuous castings.

[Effects of the Invention] By providing a casting nozzle excellent in both spall resistance and corrosion resistance according to the present invention, it has become possible to cast molten metal extremely stably compared to conventional methods.

Claims (1)

[Claims] A method for producing a two-layer casting nozzle, which comprises depositing a refractory slurry at a predetermined thickness on the inner wall surface of the casting nozzle by a slurry removal method.