JP4460859B2 - Sliding nozzle plate for molten metal - Google Patents

Description

The present invention relates to a sliding nozzle plate which is a part of a sliding nozzle used for controlling the flow rate of molten metal in a molten metal container.

As is well known, the sliding nozzle plate is widely used for controlling the flow rate of the molten metal in the molten metal container. Most of the damage is observed in the vicinity of the molten steel flow passage hole by the molten steel and the range up to the stop zone, and the damage other than this portion is extremely small. High corrosion resistance and wear resistance are not necessary in the parts with little damage, and various downsizing and shape changes have been studied from the past to the present.

There are known techniques for producing such a sliding nozzle plate,
One of them is JP-A-58-188559. In order to prevent mutual displacement between the oval sliding nozzle plate and the outer periphery during work, a metal fitting with studs on the outside is attached to the oval sliding nozzle plate by means such as shrink fitting. By joining the oval sliding nozzle and the outer periphery via the stud, the bonding force between different materials is reinforced.
JP 58-188559 A

In the means of Japanese Patent Application Laid-Open No. 58-188559, which is the above conventional example, the joint strength is improved because the joint is made through the stud, but since the stud portion is cracked when the castable is dried, it is put into practical use. It has not been. In addition, when the actual machine is in use, the vicinity of the molten steel flow passage hole is considered to reach a temperature at which the iron melts, and it is considered that the bonding strength between the oval sliding nozzle and the outer peripheral portion decreases during use. In view of such circumstances, the present invention has an object to improve the bonding strength with an oval sliding nozzle.

The present invention has been made in view of the above points, and in order to solve the above problems, the main part of the plate in the vicinity of the molten metal discharge port of the sliding nozzle plate for controlling the flow rate of the molten metal and the stop zone. Is formed of a fired refractory mainly composed of alumina carbon, and the outer periphery of the sliding nozzle plate outside the fired refractory is formed of a castable refractory, and the outer periphery of the sliding nozzle plate The thermal expansion of castable refractories between 500 and 800 ° C. is in the range of −50 to + 50% of the value of alumina carbon refractories in the main part of the plate, An object of the present invention is to provide a sliding nozzle plate for molten metal, characterized in that a step is provided .

Further, the step provided on the outer periphery of the sliding nozzle plate on the castable refractory and the entire circumference or part of the side surface of the plate main part is 1/3 to 2/3 × from the sliding surface side with respect to the plate thickness d. The present invention provides a sliding nozzle plate for molten metal that is provided at the position d and has a step width of 1/10 to 1 × d.

Furthermore, another object of the present invention is to provide a molten metal sliding nozzle plate provided with two or more stepped portions on the side surface of the castable refractory material on the outer peripheral portion of the sliding nozzle plate and the main portion of the plate.

The sliding nozzle plate for molten metal of the present invention is formed of a fired refractory mainly composed of alumina carbon at the main part of the molten metal flow rate control sliding nozzle plate in the vicinity of the molten metal discharge port and the stop zone. In addition, since the outer periphery of the sliding nozzle plate outside the fired refractory is formed of castable refractory, the main part of the plate, such as the part in contact with the molten metal, has a sufficiently high corrosion resistance and friction resistance. The entire nozzle plate can be reduced in weight and cost, and the outer peripheral shape can be easily changed, and limited resources can be used effectively.
And the thermal expansion of the castable refractory on the outer periphery of the sliding nozzle plate between 500 and 800 ° C. is in the range of −50 to + 50% of the value of the alumina carbon refractory in the main part of the plate. By providing a step on the entire circumference or part of the side surface of the plate, the sliding nozzle plate can be prevented from slipping with the step provided on the entire circumference or part of the side surface of the main part of the plate even in a high temperature state due to the flow of molten metal. It is possible to avoid the risk of leakage steel, and has the same durability as that of a conventional one-piece integrally formed material.

Further, the step provided on the outer periphery of the sliding nozzle plate on the castable refractory and on the entire periphery or a part of the main plate portion is positioned 1/3 to 2/3 × d from the sliding surface side with respect to the plate thickness d. By setting the step width to 1/10 to 1 × d, it is possible to effectively prevent displacement.

Furthermore, by providing two or more steps on the side surfaces of the castable refractory on the outer peripheral portion of the sliding nozzle plate and the main portion of the plate, it is possible to effectively prevent displacement at the two or more steps as described above. it can.

The sliding nozzle plate for molten metal of the present invention is formed of a fired refractory mainly composed of alumina carbon at the main part of the molten metal flow rate control sliding nozzle plate in the vicinity of the molten metal discharge port and the stop zone. In addition, the outer peripheral portion of the sliding nozzle plate outside the fired refractory is formed of castable refractory, and the heat of the castable refractory on the outer peripheral portion of the sliding nozzle plate between 500 and 800 ° C. The expansion is in the range of −50 to + 50% of the value of the alumina carbonaceous refractory in the main part of the plate, and the step is provided on the entire circumference or part of the side surface of the main part of the plate . The example is shown.

The sliding nozzle plate 1 is formed by joining an upper plate and a lower plate, and these can be similarly applied. The lower plate 2 will be described with reference to FIGS. 1 to 3. As shown in FIGS. 1 to 3, the sliding nozzle plate 1 has a radius a of the projection 3 for molten steel flow control, a size (radius b) of the stop zone 4, a sliding distance c, and a plate thickness d.
The size is determined from these four values.

In such a sliding nozzle plate 1, the radius a of the protrusion 3, the size of the stop zone (radius b), and the plate main portion 5 at the sliding distance c are formed of a fired refractory material mainly composed of alumina carbon. The sliding nozzle plate 1 outside the fired refractory
The outer peripheral portion 6 is formed of a castable refractory. And it is preferable to provide the required level | step difference 7 and to join to the side surface of this plate main part 5 and its outer peripheral part 6 like FIG. 3, FIG.

When a structure made of two different materials is heated, a difference in expansion occurs, and when the coefficients of thermal expansion of the materials are greatly different, peeling at the material interface and cracking due to stress concentration inside the structure occur. Specifically, in the case of a composite type sliding nozzle plate made of an alumina carbon material having a length of 500 mm and a castable refractory, a general value of the thermal expansion coefficient at 800 ° C. of the alumina carbon material is 0.5. %.

Therefore, the thermal expansion coefficient A of the alumina carbon material at 800 ° C. is set to 0.5%,
Let B be the coefficient of thermal expansion of the castable refractory at 0 ° C. When B = 0.9%, the difference in thermal expansion coefficient (BA) is 0.4%, and 0.4% is 0.8 times (80%) the thermal expansion coefficient A of the alumina carbon material. It corresponds to. A thermal expansion coefficient difference of 0.4% corresponds to 2 mm when considered per 500 mm length. In other words, the outer peripheral portion of the plate expands by 2 mm more than the normal single material plate, and a compressive stress is applied from the outer peripheral portion toward the oval sliding nozzle plate portion at the boundary surface between the two materials. Cracks in the outer periphery with low compressive strength 2
It is considered that the outer peripheral portion is broken to make a gap of mm, and the oval sliding nozzle cannot be fixed.

When B = 0.1%, the thermal expansion coefficient difference (BA) is −0.4%, and −0.4% is −0.8 times the thermal expansion coefficient A of the alumina carbon material ( −80%). A thermal expansion coefficient difference of −0.4% corresponds to −2 mm when considered per 500 mm length. That is, the outer peripheral portion of the plate contracts by 2 mm more than the normal one material plate.
A gap is formed on the boundary surface of the material. If a gap of 2 mm is formed, there is a possibility that the oval sliding nozzle plate 1 is displaced and the molten steel passage hole is partially melted.

The difference between the thermal expansion coefficient B of the castable refractory and the thermal expansion coefficient A of the alumina carbon material is considered to have an allowable range, and was considered as follows. A = 0.5, expansion coefficient difference (B-0.5)
FIG. 5 shows the relationship between the expansion amount C per 500 mm length. When B−0.5 ≧ 0, the outer peripheral portion is affected by expansion, and when B−0.5 <0, the outer peripheral portion is contracted. For practical use of the composite type sliding nozzle plate, the limit that the outer peripheral part does not break is preferably about 1 mm or less, and the limit that the oval type sliding nozzle does not shift due to contraction is about 1 m.
m or less is preferable. From the above, it is desirable that the thermal expansion (between 500 and 800 ° C.) of the castable refractory is within ± 50% of the value of the alumina carbon refractory constituting the main part 5.

The step 7 on the side surface of the oval sliding nozzle plate 1 has a step width e (d / 10 ≦ e ≦ d) at a position d / 2 as shown in FIGS. A step 7 can be provided around the circumference line or part of the circumference line. Step width e is d /
If it is smaller than 10, the effect of preventing the shift is small, and if it is larger than d, there is a risk of skin separation between the outer peripheral portion and the oval sliding nozzle plate. The position of the step 7 is the plate 2
D / 3 to 2d / 3 from the sliding surface side, preferably d / 3 to d / 2.

When a step 7 is provided in a part, it is necessary to provide a step that exhibits an effect of preventing displacement in a state of receiving a surface pressure as shown in FIG. 1, and a step that satisfies f ≧ a / 4 is provided. If the step distance f is smaller than a / 4, the effect of preventing the shift is small. Further, when the step 7 is partly provided, it is preferable to provide two or more steps on the side surface.

In the production of the sliding nozzle plate 1, for example, a casting frame having the same shape as the outer peripheral line of the sliding nozzle plate made of castable is prepared, and the oval type sliding nozzle plate is installed at a predetermined position. Castable refractories within ± 50% of the thermal expansion (500 to 1200 ° C.) of alumina carbon refractories can be poured, dried, and molded. And the sliding surface of this molded object is grind | polished and finished smoothly.

Thus, since the composite type sliding nozzle plate produced has a step on the side surface of the oval type sliding nozzle plate, the oval type sliding nozzle plate shifts to the non-sliding surface side due to the surface pressure between the plates during use. That doesn't happen. In the conventional method, when the molten metal passes through the molten steel passage hole, the composite sliding nozzle plate may reach a temperature at which the metal melts. If the oval sliding nozzle plate is displaced when the plate is used, molten metal may leak from the gap to the non-sliding surface. However, in the present invention, the effect of preventing displacement can be sufficiently exhibited even at the temperature at which the metal melts. The risk of leaking steel can also be avoided.

Examples of the present invention will be described below. The value of the lower plate 2 of the sliding nozzle plate 1 was determined as follows according to the use conditions. As shown in FIGS. 1 to 4, g = 500 mm,
In designing a sliding nozzle plate with h = 200 mm, a = 50 mm, b
= 35 mm, c = 220 mm, d = 45 mm. a and d are sized according to the user's operating conditions. b was set larger than the size of the molten steel passage hole, and c was set with reference to the distance that the plate slides. In the oval type sliding nozzle plate 1, the plate main part 5 is made of a fired refractory using a raw material mainly composed of alumina carbon, the outer peripheral part 6 is made of a castable refractory, and the outer peripheral part 6 is made of a castable refractory. Created. In the case of the upper plate, c = 100 mm can be set because the stop zone 4 is not necessary.

In particular, as shown in FIGS. 2 and 3, a step 7 is provided on the side surface of the oval type sliding nozzle plate 1, and the step 7 is provided in the vicinity of the middle in the height direction. 22 for d = 45 mm
. The position is 5 mm. The range where the step 7 is provided is the strength to be fixed (sliding nozzle pre).

The sizes of the two casting frames in the figure were set to g = 500 mm and h = 200 mm, and the shape was matched to the outer peripheral line of the irregular sliding nozzle plate shown in FIG. The casting direction may be either the sliding surface side or the non-sliding surface side. Although it was cast from the sliding surface side this time, because of the convex dowel plate, a bottom plate with a 70 mm hole larger than radius a = 50 mm was produced and used as a casting frame. Thereafter, the positions of the molten steel passage hole and the stop zone were precisely aligned, and an oval sliding nozzle plate was installed and fixed. The castable refractory was fixed so that the cast surface was horizontal while being vibrated and dried. After drying, the sliding surface was polished so that the sliding surface became smooth.

The composite type sliding nozzle plate obtained by the above procedure was subjected to a heating test using an oxygen propane burner. Even after heating, the oval type sliding nozzle plate was fixed without coming off, and cracks were seen on the oval type sliding nozzle plate sliding surface after heating, but it was almost the same as one material plate.

The sliding nozzle of the present invention can be applied with good durability to the use of flow rate control of molten metal flow in molten metal containers such as converters and tundishes in the metallurgy field by producing an upper plate and a lower plate based on the above-mentioned purpose.

The bottom view of the lower plate of the sliding nozzle of one embodiment of the present invention, Plan view as above, Side sectional view with the top and bottom reversed, An enlarged cross-sectional view of the same step, The relationship figure of the thermal expansion amount and expansion coefficient difference of a castable refractory and an alumina carbon material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sliding nozzle 2 ... Lower plate 3 ... Projection part 4 ... Stop zone 5 ... Main part of plate 6 ... Outer peripheral part 7 ... Step

Claims (3)

Sliding nozzle for controlling the flow rate of molten metal The main part of the plate in the vicinity of the molten metal discharge port and the stop zone is made of a fired refractory mainly composed of alumina carbon, and sliding outside the fired refractory The outer periphery of the nozzle plate is made of castable refractory ,
The thermal expansion of the castable refractory at the outer periphery of the sliding nozzle plate between 500 and 800 ° C. is in the range of −50 to + 50% of the value of the alumina carbon refractory in the main part of the plate. A sliding nozzle plate for molten metal, characterized in that a step is provided on the entire circumference or part of the nozzle. Positions 1/3 to 2/3 × d from the sliding surface side with respect to the plate thickness d, the step provided on the outer periphery of the sliding nozzle plate and the entire or part of the side surface of the main part of the plate. The sliding nozzle plate for molten metal according to claim 1, wherein the step width is 1/10 to 1 × d. The sliding nozzle plate for molten metal according to claim 1 or 2, wherein two or more steps are provided on the side surfaces of the castable refractory and the plate main portion on the outer periphery of the sliding nozzle plate.

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