JPH11104795A - Immersion nozzle for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the thermal stress cracking of the upper end of the immersion nozzle, being caused by the difference between the materials of a nozzle part and a nozzle body (AG part) as well as to realize the lightening and the reduction of cost. SOLUTION: In the case of this nozzle, the immersion nozzle 1 is made by joining the upper end face of a nozzle body (AG part) 3 composed of alumina- carbon base refractory on the bottom end face of the nozzle part 2 composed of zirconia bricks, and the joint mortar is inserted into the joint clearance formed on the joint face. Further, in this case, a cylindrical iron skin 6 is attached around the side part centering the joint face, and the mortar is inserted into the clearance to combine both materials. The combined product is preferable because the joint strength of the nozzle part 2 and the nozzle body (AG part) 3 and the gas sealing property on the joint face can be kept high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an immersion nozzle used for continuous casting of molten steel.

[0002]

2. Description of the Related Art Conventionally, immersion nozzles used for continuous casting are properly used depending on the type of steel (for example, killed steel and semi-killed steel). In general, since the killed steel has a low oxygen level in molten steel, an alumina-carbon refractory containing flammable graphite is also used in the nozzle portion. Therefore, since the immersion nozzle body and the nozzle portion are made of the same material, both can be integrally formed.

However, since the semi-killed steel has a high oxygen level in the molten steel, the nozzle portion of the alumina-carbon refractory has a large melt damage. Therefore, a zirconia brick which does not contain graphite and has excellent wear resistance is used here. Therefore, as a result of being different in material from the nozzle body (AG part) made of an alumina-carbon material, it cannot be integrally formed. As shown in FIG. The structure was enclosed by the upper end surrounding part 3a of the main body (AG part) 3.

[0004]

The immersion nozzle for semi-killed steel having the above-mentioned structure has a low linear thermal expansion coefficient between a nozzle portion made of zirconia material and a nozzle body (AG portion) made of alumina-carbon material. Due to the large difference, the upper end surrounding portion 3a of the nozzle body (AG portion) often suffered from a crack, which caused an operational trouble. In addition, the presence of the upper end surrounding portion 3a has a drawback that the structure of the immersion nozzle is complicated and large, the weight is heavy and the cost is high.

[0005] The present invention has been made in view of the current situation of the immersion nozzle for semi-killed steel as described above.
Immersion nozzle for continuous casting, which prevents the upper end of the nozzle body (AG part) from cracking due to the difference in material between the nozzle part and the nozzle body (AG part), and at the same time reduces weight and reduces cost It is intended to provide.

[0006]

In order to achieve the above object, in a continuous casting immersion nozzle according to the present invention, a lower portion of the nozzle and an upper portion of the nozzle body are surface-bonded to each other to cover the outer periphery of the side surface of the nozzle portion. A structure in which the surrounding part is omitted is adopted. That is, as shown in FIG. 1, the upper end face of the nozzle body (AG section) made of alumina-carbon refractory was joined to the lower end face of the nozzle section made of zirconia brick via a joining mortar layer.

Accordingly, the outer periphery of the side surface of the nozzle portion is not built in the surrounding portion of the nozzle body as in the related art,
It is possible to effectively prevent a crack in the surrounding portion at the upper end of the nozzle body due to the difference in the material. In addition, as a result of the simplified structure of the joint, the weight and cost of the immersion nozzle can be advantageously reduced. In this case, the diameter of the nozzle part that fits with the tip of the stopper is designed to be the minimum size necessary for fitting,
The diameter of the entire immersion nozzle can be reduced.

In practicing the present invention, it is preferable that the lower end surface of the nozzle portion is formed in a convex shape and the upper end surface of the nozzle body (AG portion) is formed in a concave shape which can be fitted thereto. It is preferable because both can be easily joined. In this case, the protruding length of the convex shape is set to be slightly smaller than the height of the entire nozzle portion, for example, 1/6 of the height of the entire nozzle portion.
About. Even with such a small height, since a stepped portion can be formed, it is advantageous in that molten steel can be prevented from blowing out from between the two. Further, it is desirable to form the step portion at a position of about 1/2 of the thickness of the nozzle body from the viewpoint of preventing cracks.

At this time, as shown in FIG. 2, if a joint clearance of 1 to 2 mm is formed between both end portions, as a countermeasure against expansion and press cracking of a step portion (a dowel / uneven portion) constituting a joint portion. It is valid. Usually, a joint mortar is inserted into the joint clearance, and the nozzle portion and the nozzle body (AG portion) are firmly fixed via the mortar layer.

Further, in addition to the above configuration, a tubular steel shell is extrapolated to a side peripheral surface including a joint between the nozzle portion and the nozzle body (AG portion), and the cylindrical steel shell and the side peripheral surface are inserted. It is also possible to fill and fix the joining mortar in the gap formed between the nozzle and the nozzle, and by adopting such a configuration, the connection retention between the nozzle portion and the nozzle body (AG portion) and the gas sealing property can be improved. preferable.

As a material of the nozzle portion, 90% by weight or more of ZrO ₂ as a main component and CaO or Y as a stabilizer are used.
Zirconia raw materials containing ₂ O ₃ in an amount of not more than 10% by weight are particularly suitable, and these raw materials are used alone or in combination of two or more at the time of molding. Further, an alumina-carbon-based raw material having a conventional composition is applied as it is to the nozzle body (AG section).

The joining mortar must have high adhesive strength and hot bending strength from room temperature to high temperature and excellent corrosion resistance (melting resistance to molten steel). , Various mortars known in the art,
For example, sodium silicate and aluminum phosphate, or any alumina mortar containing phenol rate Gin as a binder but can be used, inter alia Al ₂
Phenol resin is added at an external ratio of 1 to the inorganic component consisting of a mixture of O ₃ 80% by weight or more and graphite 20% by weight or less.
Mortars blended in a range of 0% by weight or more and 50% by weight or less are excellent in the above-mentioned properties and are particularly suitable.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a structure of a continuous casting immersion nozzle according to the present invention and a mounting state thereof during use. The immersion nozzle 1 has an upper end connected to a tundish 14 via a tuyere brick 18, and a lower end penetrating a turn dish seat plate 15 and immersed in a mold 13. The immersion nozzle 1 includes a nozzle portion 2 made of zirconia brick and a nozzle body 3 made of an alumina-carbon refractory joined to a lower end surface thereof through a joining mortar layer A.

When the nozzle 2 is opened by the vertical movement of the stopper 17, the molten steel 16 passes through the nozzle body 3 and flows out of the tip dipping part 4 into the mold 13.

FIG. 2 is an enlarged sectional view showing the structure of the peripheral portion of the joint between the nozzle portion 2 and the nozzle body 3. As shown in FIG. As shown in the drawing, the nozzle portion 2 is formed in an inverted conical shape, and has a funnel-shaped through hole 7 (17 mmφ) formed in the center thereof.
Is designed to have a minimum size (100 mmφ) necessary for fitting. The lower end face 9 of the nozzle portion 2 is formed in a convex shape, and can be fitted to a concave upper end face 10 of the nozzle body 3 described later.
A joint clearance 11 of mm is formed. In this case, the total length of the through-hole 7 and the inclination of the funnel-shaped opening 8 are completely the same as those of the conventional immersion nozzle shown in FIG. 3, and there are no operational changes.

The nozzle main body 3 is a cylindrical refractory having an upper portion formed to have a diameter corresponding to the lower diameter of the nozzle portion 2 and a lower immersion portion 4 having a slightly smaller diameter. 4 is made of an alumina-carbon refractory except that the outer periphery of 4 is covered with a zirconia brick (ZG portion).
The outer peripheral portion is covered with a heat insulating material 5. The diameter of the central through hole 7 of the nozzle main body 3 is
The diameter is the same as the diameter of the
It is set so that there is no extreme change part on the way. this is,
This is for minimizing cracks caused by molten steel. Further, at the upper end of the nozzle body 3, there is formed a concave portion into which the convex portion of the nozzle portion 2 can be fitted, and the position of the step portion is set to a half of the inner and outer diameters.

A 1.5 mm-thick cylindrical stainless steel shell 6 is extrapolated to the side peripheral surface including the joint between the nozzle section 2 and the nozzle body (AG section) 3. The joint mortar A is filled and fixed in the gap 12 formed between the side peripheral surface and the gap 12 so as to improve the gas sealing property.

The joining mortar filled in the gap 12 and joint clearance 11 is a composition comprising an inorganic component containing 85% of Al ₂ O ₃ and 13% of graphite and 20% of phenol resin in an external ratio. The mortar is abbreviated as below, and is filled into the gap 12 and the joint clearance 11, and then heated and cured at a temperature of about 200 ° C. for 6 hours to be joined. In this mortar, the amount of alumina is particularly increased from the viewpoint of corrosion resistance.

The joining mortar A needs to have a sufficient adhesive strength from normal temperature to high temperature, and
When set into the tuyere brick, bending stress due to contact with the tuyere brick 18 and other impacts acts, and during operation, stress due to molten steel flow and thermal shock is applied. However, these stresses must be sufficiently eliminated. Therefore, the tensile adhesive strength and the hot bending strength of the mortar A were measured by the following methods. Tensile adhesive strength: With respect to the immersion nozzle obtained by bonding the end faces by the above method, the strength of the joint was measured using a tensile load tester. In this case, the fracture was more likely to occur in the nozzle body (AG portion) than in the joint surface, and it could withstand a tensile load of 800 kg or more. Hot bending strength measurement method: A rectangular parallelepiped sample piece having a cross section of 25 × 25 mm is cut out from an alumina-carbon refractory (hereinafter abbreviated as “AG brick”), which is a material of the nozzle body (AG section), and mortar is applied to the cross section. A is applied and joined, and 200
Cured at ° C. Next, the hot bending strength of each bonded sample was measured by the method shown in FIG.

FIG. 5 is a graph showing the results, and also shows the results of two conventional mortars (B and C) for comparison. According to this, the mortar A used in the example has a lower strength at 800 ° C., but has a higher strength than other conventional mortars, and has a strength of 1400 ° C. close to a practical temperature.
The strength was improved and the most excellent results were obtained. Here, the mortar B is an alumina-carbon mortar containing a phosphoric acid binder, and the mortar C is a siliceous mortar containing an organic binder.

Since the joining mortar comes into direct contact with molten steel, its corrosion resistance was measured by the following method. Corrosion resistance measurement method: As shown in FIG. 6, a 3 mm joint was provided on an AG brick, a mortar was applied between the joints, and then heated in a high-frequency induction furnace under a test condition of 1600 ° C. × 1 hour × 2 times. The amount of erosion was measured.

Table 1 shows the results. The measured values of the AG brick and the conventional mortar (B and C) are also shown for comparison. According to this, it was found that the mortar A used in the example suffered only about twice the amount of erosion of the AG brick itself, and was also the most excellent in corrosion resistance.

[0021]

[Table 1]

Table 2 shows the composition and typical physical properties of the zirconia brick and the alumina-carbon refractory used in this example, classified by use site. In this table, the material of the immersion nozzle for killed steel is also described for reference.

[0023]

[Table 2]

In the conventional immersion nozzle shown in FIG. 3, since the material of the nozzle part 2 and the material of the nozzle body (AG part) 3 are different, the outer periphery of the nozzle part of the zirconia brick is made to correspond to the nozzle body (AG part).
(AG brick). As shown in Table 2, the zirconia brick has a larger linear expansion coefficient than the alumina-graphite refractory, so that the nozzle portion expands greatly during the hot process, and the alumina-graphite refractory outside the nozzle is cracked and recovered after use. The immersion nozzle has a deep crack (150-170) reaching from the upper end to the lower end of the nozzle receiving brick.
mm). However, in the nozzle of the present invention, since the AG brick covering the outer periphery of the nozzle portion was removed and a nozzle portion having a structure as shown in FIG.
No trace of insertion of molten steel 16 was observed, and no generation of a crack was observed.

FIGS. 7 and 8 show the quality of the gas sealing property of the joint depending on the presence or absence of the cylindrical iron sheath 6 in the present invention. While stopcock a central through-hole 7 of both the nozzle portion 2 from the opening, cutting the nozzle body (AG unit) 3 in the length of the moderate, from here into water while adding air pressure of 2 Kg / cm ² It was immersed to observe the occurrence of bubbles. Air leakage from the joint is not observed regardless of the presence or absence of the tubular steel 6, but when the tubular steel 6 is not used (FIG. 7), air bubbles passing through the porous zirconia brick are observed. Was.
However, as shown in FIG. 8, the air bubbles from the zirconia bricks are effectively suppressed by the extrapolation of the tubular iron shell 6,
Almost no.

The weight of the immersion nozzle described in this embodiment is 16.9 kg, and the weight of the conventional nozzle (21.
0 kg), it is reduced to about 80%. Furthermore, due to the simplification of the structure, the manufacturing cost per unit was reduced to about 75% of the conventional product. Further, in a bloom tundish, since a large number of immersion nozzles are used at the same time, the cost reduction effect can be said to be extremely large.

[0027]

As described above, the continuous casting immersion nozzle of the present invention has a structure in which the upper end face of the nozzle body (AG section) is joined to the lower end face of the nozzle section via the joining mortar layer as described above. The crack at the upper end of the immersion nozzle due to the difference can be effectively prevented. In addition, since the diameter of the nozzle portion to be fitted to the tip of the stopper can be designed to be small, the structure of the joining portion is simplified, and the weight and cost of the nozzle can be reduced.

Further, in the present invention, a tubular steel shell is extrapolated to a side peripheral surface including a joint portion between a nozzle portion and a nozzle body (AG portion), and a space between the cylindrical steel shell and the side peripheral surface is formed. When the joining mortar is filled and fixed in the gap formed in the nozzle, the connection holding property between the nozzle portion and the nozzle body (AG portion) is enhanced, and at the same time, the gas sealing property is improved.

Further, since the above configuration is employed, the nozzle portion can be formed using a stabilized high-concentration zirconia raw material, so that the durability of the immersion nozzle and the improvement in steel quality are guaranteed. .

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a continuous casting immersion nozzle according to the present invention and a mounted state during use.

FIG. 2 shows a nozzle part and a nozzle body (AG) of the immersion nozzle.
Cross-sectional view showing the structure of the periphery of the junction with the

FIG. 3 is a diagram showing the structure of a conventional immersion nozzle for continuous casting and the mounting state during use.

FIG. 4 is an explanatory diagram related to a method for measuring hot bending strength.

FIG. 5 is a graph showing measurement results of hot bending strength.

FIG. 6 is an explanatory diagram relating to a corrosion resistance measuring method.

FIG. 7 is a view showing a situation during an air leak test for an immersion nozzle having no tubular iron shell.

FIG. 8 is a diagram showing a situation during an air leak test for an immersion nozzle having a cylindrical iron shell.

[Explanation of symbols]

 1: immersion nozzle 2: nozzle part 3: nozzle body (AG part) 6: tubular steel 9: lower end face 10: upper end face 11: joint clearance 12: gap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Ishiura 1-1-66, Funamachi, Taisho-ku, Osaka-shi, Osaka Inside Nakayama Steel Works, Ltd. (72) Inventor Kazuhiro Sasaki 1-1-1, Funamachi, Taisho-ku, Osaka-shi, Osaka No.66 Inside Nakayama Steel Works Co., Ltd. (72) Inventor Yoichi Ise 1-166 Funamachi, Taisho-ku, Osaka City, Osaka Inside Nakayama Steel Works

Claims (5)

[Claims] 1. An upper end face of a nozzle body (AG section) made of an alumina-carbon refractory is joined to a lower end face of a nozzle section made of zirconia brick via a joining mortar layer. Immersion nozzle for continuous casting. 2. A nozzle body (AG section) comprising a convex lower end surface of a nozzle portion made of zirconia brick and an alumina-carbon refractory, one end of which is formed so as to be fitted to the lower end surface of the nozzle. An immersion nozzle for continuous casting characterized by being joined to a concave upper end face via a joining mortar layer having a thickness of less than 2 mm. 3. The immersion nozzle for continuous casting according to claim 1, wherein the nozzle portion and the nozzle body (AG) are provided.
By externally inserting a tubular steel shell on the side peripheral surface including the joint portion with the part, and filling and fixing a joining mortar into a gap formed between the cylindrical steel shell and the side peripheral surface, An immersion nozzle for continuous casting that has improved connection retention between the nozzle portion and the nozzle body (AG portion) and gas sealability. 4. The nozzle portion is made of ZrO as a main component.
_{2 in an amount} of 90% by weight or more and CaO or Y ₂ O _{3 as} a stabilizer.
The immersion nozzle for continuous casting according to claim 1, wherein the zirconia brick raw material containing the zirconia brick material in an amount of 10% or less by weight is used alone or in combination of two or more kinds. 5. The bonding mortar contains phenolic resin in an external ratio of 10% by weight or more and 50% by weight or less with respect to an inorganic component composed of a mixture of 80% by weight or more of Al ₂ O _{3 and} 20% by weight or less of graphite. The immersion nozzle for continuous casting according to claim 1, wherein the immersion nozzle is blended within a range.