JPH10305357A - Interpolation type dipping nozzle for continuous molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent alumina from depositing to an interfitting part of an interpolation type dipping nozzle and also to give and keep an enough strength to control a molten steel stream caused by a stopper. SOLUTION: In the interpolation type dipping nozzle to control the molten steel stream by a closing motion of the nozzle stopper (not illustrated) at a top end of a nozzle hole, the dipping nozzle 1 is constituted to be divided to a nozzle main body 2 and a sheet like refractory 3, which intercombines with an interfitting hollow part 2a arranged at an upper part of the main body 2. The sheet like refractory 3 is formed with a defined form brick of a gas permiable material without carbon. The nozzle main body 2 and the sheet like refractory 3 are combined through a mortar layer. The volume ratio of the mortar set layer part 4 to a gas pool part 5 between the nozzle main body 2 and the sheet like refractory 3 is in a range of 10:1-1:10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insert-type immersion nozzle for continuous casting, which is inserted into the bottom of a molten metal container to adjust the outflow of molten metal by opening and closing the upper end of an immersion nozzle hole by a nozzle stopper. .

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, when molten steel is poured into a mold c from a ladle a through a tundish b at a steel mill or the like, a dipping nozzle d is provided at the bottom of the tundish b for the purpose of preventing oxidation of the molten steel. Is used. The immersion nozzle d is an excellent Al ₂ O ₃ -C material in spalling resistance as the body, structure arranged ZrO ₂ -C are commonly employed in the contact portion between the strong mold powder corrosive.

[0003] The immersion nozzle includes an extrapolation type immersion nozzle used directly or through a collector nozzle and a slide gate for a molten metal flow control device mounted outside a molten metal container (not shown). As shown in the figure, the nozzle is roughly divided into an insertion type dipping nozzle d which is inserted into the bottom of the molten metal container b and the upper end of the hole f of the dipping nozzle d is opened and closed by a nozzle stopper e to adjust the flow rate of the molten metal.

[0004]

However, in the interpolation type immersion nozzle, alumina inclusions generated by Al deoxidation in steel easily adhere to a portion (fitting portion) where the immersion nozzle and the stopper are fitted. There is a problem that it is difficult to control the outflow of molten steel.

[0005] As the origin of alumina causing the adhesion of alumina, it is conceivable that 1) a reaction product of a refractory and molten steel, and 2) alumina generated from a molten steel component due to a decrease in temperature of the molten steel.

1) Regarding the reaction product between the refractory and the molten steel, in a high-temperature refractory, SiO ₂ used as a refractory raw material or between SiO ₂ and C contained as impurities of the refractory raw material. The reaction of equation (1) occurs. And the generated SiO gas: described as (g) below.
And CO (g) diffuse to the interface between the nozzle and the molten steel, and react with Al in the molten steel according to the equations (2) and (3) to produce alumina on the working surface of the nozzle and melt on the nozzle surface. And the starting point of adhesion of Al ₂ O ₃ inclusions in the steel. (The underlined substances are in the state of being melted in molten steel.
same as below. ) SiO ₂ (s) + C (s) = SiO (g) + CO (g) (1) 3SiO (g) +2 Al = Al ₂ O ₃ (s) +3 Si (2) 3CO (g) +2 Al = Al ₂ O ₃ (s) +3 C (3) In the above formula, (s) represents a solid.

In this case, in order to eliminate the reaction of the formula (1), the inner hole of the immersion nozzle is coated with a refractory material containing no C, that is, Al is added to the surface layer of the runner of the immersion nozzle.
Japanese Unexamined Patent Publication No. 51-54836 discloses a continuous casting immersion nozzle provided with a refractory to which ₂ O ₃ , MnO ₂ , MgO, CaO, and SiO ₂ are added alone or in combination.

However, S which is preferred in this publication
In the region of 90 to 99 wt% of iO ₂ , alumina is generated on the operation surface of the nozzle by the reaction shown in the equation (4), similarly to the equations (1) to (3), and fused to the nozzle surface to form Al _{2 in} steel. O ₃
This is the starting point for inclusions.

3SiO ₂ (s) +4 Al = 2Al ₂ O ₃ (s) + 3Si (4) Al ₂ O containing no more than 5% by weight of SiO _2
3 (or MgO, ZrO ₂ ) is a carbonless high alumina refractory having a content of 90% by weight or more.
JP-A-5-154628 discloses an alumina clinker having an alumina content of 90% by weight or more, an alumina content of 70% by weight or more, a carbon content of less than 1% by weight, and a silica content of It has a refractory composition of less than 1% by weight and a particle size of 0.21 mm or less of 20-70.
A continuous casting nozzle bore having a particle size configuration occupying% is disclosed.

However, these materials are mainly intended to suppress the adhesion of alumina originating from the reaction product between the refractory and the molten steel, and cannot suppress the adhesion of alumina generated due to a decrease in the temperature of the molten steel.

2) With respect to alumina produced by lowering the temperature of the molten steel, the oxygen dissolving ability of the molten steel decreases due to the lowering of the temperature, and the released oxygen causes the reaction of Al in the molten steel with the formula (5) to produce alumina. This is the starting point of the adhesion of Al ₂ O ₃ inclusions.

[0012] _{2 Al +3 O = Al 2 O} 3 (s) ... (5) a method alumina deposition of origin to the reaction products of these refractories and the molten steel, both alumina deposition of generated by the temperature drop of the molten steel to suppress Various methods have been disclosed for providing a slit space between a porous nozzle inner hole and a main body, and blowing an inert gas into molten steel through pores of the inner hole to prevent nozzle blockage.

The porous nozzle inner hole material is Al
₂ O ₃ —SiO ₂ —C materials are widely used.
Also, as a prior art, in terms of steel quality, in an alumina / graphite gas injection type continuous casting immersion nozzle, the composition of the inner body corresponding to the gas injection portion is 5 wt% or less of silica, 30 to 80 wt% of alumina, and 5% of graphite. ~ 50w
JP-A-3-208917, characterized in that the inert gas discharge portion of the inner hole of the nozzle body formed of a carbonaceous refractory has air permeability,
Immersion nozzle for continuous casting characterized by being laminated by a refractory material not containing a carbon source.
No. 613 is known.

However, when a refractory not containing a carbon source is laminated on the inner hole of the nozzle body formed of the refractory containing carbon, the refractory containing no carbon generally has a higher thermal expansion coefficient than the refractory containing carbon. Since it is large, there is a disadvantage that an external carbon-containing refractory is destroyed due to a difference in thermal expansion at a high temperature.

When a carbon-containing refractory and a carbon-free refractory are laminated, the following disadvantages also occur.

In the insertion type immersion nozzle, the immersion nozzle fitting portion, which plays an important role in adjusting the flow rate of the molten metal by opening and closing the upper end of the immersion nozzle hole by the nozzle stopper, is required to have strength capable of withstanding the impact of the stopper. Is done.

The optimum firing temperature of the carbon-containing refractory material (the firing temperature at which the required strength is developed) is 700 to 1200 ° C.
On the other hand, the optimum firing temperature of the refractory material containing no carbon is 1300 ° C. or more. A carbon-containing refractory material and a carbon-free refractory material are simultaneously
When fired at 000 ° C., the refractory material containing no carbon becomes insufficiently fired (insufficient sintering) and cannot obtain sufficient strength.

That is, in the case of the porous portion and the main body portion integrated type, it is well known that conventional porous materials such as Al ₂ O ₃ -C and ZrO ₂ -C do not have the strength required for the insertion type immersion nozzle fitting portion. obtained to be as, for porous material is optimum firing temperature as Al ₂ O ₃ or high alumina is much higher than that of the main body portion of the Al ₂ O ₃ -C quality, sufficient strength becomes insufficient sintering is I can't.

Therefore, if a refractory material containing no carbon is laminated on the fitting part, the fitting part will not be strong enough to withstand the impact of the stopper, and the fitting part will be damaged during use, which will hinder the control of the molten steel flow.

Further, when a porous amorphous refractory is applied to a once manufactured immersion nozzle, the strength may not be sufficient until the refractory applied after sintering after contact with molten steel may lead to troubles in the early stage of casting. There is.

[0021]

SUMMARY OF THE INVENTION The present invention is to prevent the adhesion of alumina to the fitting portion of the above-mentioned insertion type immersion nozzle by blowing gas, and to provide a fitting portion having sufficient strength for controlling the flow of molten steel by the stopper. SUMMARY OF THE INVENTION It is an object of the present invention to provide an insertion type immersion nozzle for continuous casting having a nozzle stopper which is inserted into the bottom of a molten metal container to discharge molten metal. A refractory for a sheet in which an immersion nozzle is fitted in a fitting recess provided in an upper part of a nozzle body in a continuous casting in which the flow of molten metal is controlled by opening and closing an upper end of a nozzle hole. The refractory for a sheet is formed of a fixed fired brick made of a material having air permeability and not containing carbon, and a mole is provided between the nozzle body and the refractory for a sheet. Characterized by being fixedly fitted through Le. Claim 2 is the invention according to claim 1,
The ratio of the volume of the mortar set portion and the volume of the gas pool portion interposed between the nozzle body and the sheet refractory is set to 1
The ratio is 0: 1 to 1:10.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is a cross-sectional view of a single insertion type immersion nozzle 1 for continuous casting according to the present invention. The nozzle body 2 has a tubular and elongated shape, and an appropriate nozzle provided on the upper part of the nozzle body 2. The sheet refractory 3 mounted in the fitting recess 2a having a depth is separately manufactured and set. FIG. 1 shows an unset state.

The details of the state in which the sheet refractory 3 is set in the fitting concave portion 2a are shown in FIGS. 2A and 2B by enlarging two examples of the upper structure of FIG. The refractory for sheet 3 is made of a fixed fired brick made of a material having air permeability and not containing carbon, and the joint between the nozzle body 2 and the refractory for sheet 3 has a trapezoidal shape whose diameter is reduced downward. A mortar set portion 4 is provided at both ends of the joint, and a gas pool portion 5 is provided so as to be sandwiched between the mortar set portions 4 on both sides. Here, the mortar set portion 4 refers to a portion where the mortar is applied and filled, and the gas pool portion 5 refers to a space portion connected to the slit 6. The curved surface area 3a where the upper part of the sheet refractory 3 is largely opened is formed on the contact surface with the nozzle stopper, and the lower small diameter area 3b is formed on the inner pipe part.

A slit 6 is formed in the nozzle body 2 below the gas pool section 5 in the longitudinal direction communicating with the gas pool section 5, and the slit 6 extends from the outer periphery of the nozzle body 2 to the slit 6. A vertically drilled socket 7 allows communication with the outer periphery of the nozzle body 2. Therefore, the slit 6 is a passage for flowing gas from the socket portion 7 for introducing the inert gas to the brick of the fitting concave portion 2a having air permeability.

FIG. 2 (A) shows an example of the mortar set part 4: gas pool part 5 = 2: 5, and FIG. 2 (B) shows an example of the mortar set part 4: gas pool part 5 = 3: 2. However, in the case of FIG. 2B in which the mortar set portion 4 is large, it is difficult for the gas indicated by the dotted arrow to come out from the fitting concave portion 2a.

As described above, when the volume ratio of the mortar set portion 4 to the gas pool portion 5 is larger than 10: 1, the gas does not sufficiently turn to the back of the fitting recess 2a, so that the fitting recess 2a is formed.
Gas is no longer required, and the effect of suppressing alumina adhesion is reduced, which is not preferable.

Conversely, the mortar set section 4 and the gas pool section 5
And the volume ratio with. If the ratio is less than 1:10, the sealing surface of the mortar becomes small, the seal is broken during casting, and gas leaks from joints.
Since the bonding surface of the sheet refractory 3 (the fixed-form fired brick) mounted on the fitting recess 2a is small, the sheet refractory 3 may be detached from the nozzle body 2 during casting, which is not preferable. Therefore, the volume ratio of the mortar set part 4: gas pool part 5 may be in the range of 10: 1 to 1:10, and preferably 3: 1 to 1: 3.

[0029]

Since the present invention is constructed as described above, the following effects can be obtained.

1) According to the first aspect of the present invention, (1) The difference in thermal expansion between the material of the carbon-containing immersion nozzle body and the material of the refractory for the fitting concave sheet not containing carbon is determined by the joint. It is possible to prevent the nozzle body from cracking during absorption by absorption.

(2) The refractory for a sheet having a fitting recess sufficient for controlling the flow of molten steel is imparted by fitting a refractory for a sheet having air permeability and containing no carbon into the fitting recess. Can be.

(3) Since the appropriate setting of the gas pool is facilitated, the inert gas can be effectively supplied to the fitting recess, which contributes to the prevention of the adhesion of alumina to the fitting recess. it can.

2) According to the second aspect of the present invention, there is no gas leakage from the sealing surface, and the effect of suppressing alumina adhesion can be further improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a single insertion type immersion nozzle for continuous casting according to the present invention.

2 (A) and 2 (B) are enlarged detailed views each showing two examples of the upper structure of FIG. 1 in half.

FIG. 3 is an explanatory view showing a conventional continuous casting facility around an immersion nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Immersion nozzle 2 Main body 2a Fitting concave part 3 Refractory for sheet 4 Mortar set part 5 Gas pool part 6 Slit 7 Socket part

Claims (2)

[Claims] 1. An insertion type immersion nozzle for continuous casting in which molten metal flows out by being inserted into the bottom of a molten metal container and the upper end of a nozzle hole is opened and closed by a nozzle stopper to control the outflow of molten metal. The nozzle is divided into a nozzle body and a refractory for a sheet fitted in a fitting recess provided at an upper portion, and the refractory for the sheet is fixedly fired using a material having air permeability and containing no carbon. An insertion-type immersion nozzle for continuous casting, wherein the nozzle is formed of a brick and is fitted and fixed between the nozzle body and the refractory for a sheet via a mortar. 2. The ratio between the volume of the mortar set portion and the volume of the gas pool portion interposed between the nozzle body and the refractory for a sheet is set to a ratio of 10: 1 to 1:10. Immersion nozzle for continuous casting.