JPH11216539A - Dummy bar head for continuous casting - Google Patents

Abstract

(57) [Problem] To establish a dummy bar head for continuous casting that can simplify the work of installing a sealing material and a coolant in a mold and increase the amount of molten metal injected at the start of casting. SOLUTION: A water passage 6 is provided inside a dummy bar head 1, and the dummy bar head is water-cooled by cooling water passing through the water passage. At this time, if the contact portion 3 with the molten metal is made of copper or a copper alloy, the cooling ability is further improved. Also, the cooling water is sprayed by attaching the spray nozzle 7 to the dummy bar head,
By cooling the joint between the slab and the dummy bar, it is also possible to prevent operational troubles caused by the joint.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dummy bar head which is inserted into a mold of a continuous casting facility at the start of casting.

[0002]

2. Description of the Related Art In continuous casting, at the start of casting, a dummy bar having a dummy bar head attached to the upper end is set so that the dummy bar head is located at a predetermined position in a mold, and molten metal is poured into the mold to form a dummy bar. Then, the cast piece solidified below the mold through the dummy bar is continuously pulled out to perform casting. For example, as disclosed in Japanese Patent Application Laid-Open No. 54-48639, this dummy bar head is made of cast steel, and is provided with a dovetail-shaped recess at a joint with a cast piece. Although the slab and the dummy bar head are fixed in the slab withdrawal direction by the groove-like recess, the slab and the dummy bar head have a structure that can be separated by a relative movement in the lateral direction with respect to the long axis of the slab.

[0003] Between the dummy bar head and the inner wall of the mold,
Since a gap for insertion and withdrawal is provided, a sealing material is provided to close the gap. In addition, in order to prevent erosion of the dummy bar head and promote solidification of the injected molten metal, a steel material or the like is provided as a coolant in a mold in which the dummy bar head is inserted. This work of installing the sealant and coolant must be performed each time casting is started.
Further, 10 to 15 minutes are spent for one operation, which is a cause of a decrease in efficiency of the continuous casting machine.

[0004] In addition, in order to secure the solidification time of the molten metal and to promote the removal of heat from the molten metal to the mold and the dummy bar head, the amount of molten metal injected into the mold at the start of casting is set to the amount of injection in the steady casting state. Significantly less than in comparison. For this reason, it causes a reduction in efficiency due to a delay until reaching a steady casting state and a reduction in quality of a slab at the start of casting.

Furthermore, the temperature of the joint between the slab and the dummy bar head must be controlled by the steel composition and the elapsed time from the start of casting. However, conventionally, the temperature of the joint between the slab and the dummy bar head has been conventionally controlled. Since the cooling was also performed by the secondary cooling water for cooling the slab, the control was not sufficient, so that an operation trouble was sometimes caused by excessive or insufficient cooling. For example, if the cooling is insufficient, pulling out cannot be performed due to extension of a slab portion (hereinafter, this slab portion is referred to as “reed portion”) that fits into the above-mentioned dovetail-shaped depression, breakout due to breakage of a slab solidified shell, and the like. In addition, excessive cooling may make it impossible to pull out the cracked portion due to cracking at the time of straightening.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to simplify the work of installing a sealing material and a cooling material, and at the time of starting casting. An object of the present invention is to provide a dummy bar head capable of increasing a molten metal injection amount.

[0007]

A dummy bar head for continuous casting according to a first aspect of the present invention is characterized in that a water passage is provided therein, and water is cooled by cooling water passing through the water passage.

[0008] A dummy bar head for continuous casting according to a second invention is characterized in that, in the first invention, a contact portion with the molten metal is made of copper or a copper alloy.

A third aspect of the present invention is directed to a dummy bar head for continuous casting according to the second aspect, wherein a surface of copper or a copper alloy is plated.

According to a fourth aspect of the present invention, there is provided a dummy bar head for continuous casting according to the first to third aspects, further comprising a spray nozzle for spraying cooling water.

Since the dummy bar head is water-cooled,
Cooling of the molten metal injected into the mold at the start of casting is promoted, solidification is promoted not only on the contact surface with the dummy bar head but also on the side of the slab that contacts the mold, and a strong solidified shell is formed in a short time. You. Therefore, the injection amount at the start of the injection can be increased, and the state can be shifted to the steady casting state at an early stage. Furthermore, the amount of coolant can be reduced, and the work of installing the coolant is simplified, and the efficiency of the continuous casting machine is improved.

[0012] By making the contact portion of the dummy bar head with the molten metal a copper or copper alloy having high thermal conductivity, heat removal by the dummy bar head is further promoted. However, since copper or copper alloy has low wear resistance, it is preferable to improve the wear resistance by plating the surface with Ni or Cr.

Further, since the cooling water can be sprayed from the spray nozzle attached to the dummy bar head toward the junction between the dummy bar head and the slab, the temperature of the junction between the slab and the dummy bar head is 2 ° C. Without being affected by the next cooling water, it is independently controlled by the steel composition and the elapsed time from the start of casting, etc., and is maintained in an appropriate temperature range.
Operation troubles caused by the alizabeth part are avoided.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an example of an embodiment of a dummy bar head according to the present invention. FIG. 1 is a cross-sectional view of a state inserted into a mold as viewed from the side of the mold. FIG. 2 is a schematic plan view of the dummy bar head. Is a perspective view seen from the S direction in FIG. 1, and FIG. 4 is a schematic side view showing a state where a dummy bar having a dummy bar head of the present invention attached to an upper end is inserted into a continuous casting machine.

In these figures, a dummy bar head 1 is shown.
Is formed by connecting a head body 2 and a molten metal contact portion 3 that comes into contact with the molten metal when inserted into the mold 12 by a reinforcing member 4. Then, a water passage 6 is formed between the head body 2 and the molten metal contact portion 3, and the water passage 6 is a water passage 6 a in the head body 2.
The cooling water flows in the order of the water channel 6a, the water channel 6, and the water channel 6b, and the dummy bar head 1 is water-cooled.
The molten metal contact portion 3 forms a dovetail-shaped recess 9 as a connecting means with a cast piece.

The head body 2 is made of cast steel, and the molten metal contact portion 3 is made of cast steel, copper, or a copper alloy. By making the molten metal contact portion 3 made of copper or a copper alloy, the cooling ability can be enhanced. When the molten metal contact portion 3 is made of copper or a copper alloy, it is preferable to improve the wear resistance by applying a plating layer 5 of Ni, Cr, or the like to the surface.

A spray nozzle 7 is arranged on a side surface of the head main body 2, and the spray nozzle 7 is connected to a water passage 8 in the head main body 2.
The spray is sprayed from the spray nozzle 7 toward the joint between the dummy bar head 1 and the slab. Since the spray nozzle 7 is disposed in the groove 10 provided on the side surface of the head main body 2, it is difficult to insert the dummy bar head 1 into the mold 12 and to pass through the guide roll 17 and the pinch roll 18 of the continuous casting machine. Also, when the dummy bar head 1 is pressed by the pinch roll 18, the dummy bar head 1 is not deformed due to the pressure reduction.

A drum 14 is provided on a dummy bar storage table 13 above a transfer table 16 of the continuous casting machine. A cable 15 wound around the drum 14 is connected to the dummy bar head 1 via a dummy bar 11, and the cable 15
A water supply / drainage channel for the dummy bar head cooling water and a water supply channel for the spray water are provided therein. The cable 15 is detachable on the way.

The dummy bar head 1 to be water-cooled as described above is inserted into a predetermined position in the mold 12, and a refractory sealing material 19 is embedded in a gap between the molten metal contact part 3 and the mold 12. A coolant (not shown) such as the above is installed, and the injection into the mold 12 is started. Since the dummy bar head 1 is water-cooled, cooling of the molten metal poured into the mold 12 is promoted, and a strong solidified shell is formed in a short time.

However, if the cooling of the dummy bar head 1 is excessively performed, a chipped portion of the dummy bar head 1 may be lost at the time of straightening the slab.
Operation trouble occurs. The present inventors investigated the four types of steel having a yield point or proof stress of 20 to 50 kgf / mm ² , and examined the tensile strength of the cast slab at the time of straightening and the presence or absence of defects in the bent part. The investigation was performed by measuring the temperature of the altar section using a thermocouple embedded in the dummy bar head 1, calculating the heat transfer based on the measured temperature value, the data on the high-temperature tensile strength of the steel, and visually checking the altar section for defects. A survey was conducted. FIG. 5 shows the results of the investigation.

As shown in FIG. 5, the defects in the bent portion are prevented and the tensile strength is 15 kgf / mm ² when the slab tensile strength at the time of straightening is about 15 to 23 kgf / mm ² for each steel type.
If the ratio is less than ² , elongation of the beak portion occurs, and if the tensile strength exceeds 23 kgf / mm ² , the bead portion is lost due to cracking. The slab temperature at which the tensile strength falls within this proper range is, for example, 30 kgf /
In the case of a mm ² steel 920~1230 ℃, 40kgf /
In the case of mm ² steel, the higher the strength of the steel, the higher the temperature and the narrower the temperature range so as to be 1800 to 1320 ° C. Therefore, in order to prevent defects in the sliver portion, it is preferable to control the cross-sectional average temperature of the slab portion of the slab in each steel type to a slab temperature range in which the tensile strength is in an appropriate range as shown in FIG. As a specific control method, the heat transfer calculation is performed by changing the cooling water amount, and the cooling water amount within an appropriate range may be obtained in advance.

The spray of the cooling water from the spray 7 is performed at least when the dummy bar head 1 is pulled out.
After passing through the lower end position of the mold 12. When the spray 7 is sprayed in the mold 12, the cooling water is heated by the injected molten metal, and there is a danger of steam explosion, which is extremely dangerous.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the dummy bar head shown in FIG. 1, a case where a molten metal contact portion is made of an Ag-containing copper alloy (Examples 1 and 2) and a case where it is made of cast steel (Example 3) will be described below. . In each embodiment, the thickness of the molten metal contact portion is 30 mm.
It is. For comparison, casting using a conventional dummy bar head (conventional example) was also performed.

In both Examples 1 to 3 and the conventional example, the steel type cast was the above-mentioned 30 kgf / mm ² steel and the slab thickness was 2
The present invention is applied to a dummy bar head of a continuous slab casting machine having a slab width of 50 mm and a slab width of 950 mm. In Examples 1 and 2,
A 3 mm-thick Ni plating layer was applied. Cooling by the spray nozzle was performed only in Example 2, and the spray nozzle was installed at a position 100 mm from the joint between the dummy bar head and the slab. Table 1 shows the operating conditions of Examples 1 to 3 and the conventional example, and FIG. 6 shows the amounts of the dummy bar head cooling water and the spray cooling water. Dummy bar head cooling water amount is 480t
/ Hr, and the spray cooling water amount was gradually decreased according to the slab drawing length, and stopped after drawing 12 m from the start of casting. It should be noted that if the cooling water amount is as shown in FIG. 6, it has been previously confirmed that the slab tensile strength at the time of straightening is within an appropriate range.

[0025]

[Table 1]

FIG. 7 shows the measurement results of the transition of the thickness of the solidified shell from the start of casting in Examples 1, 2 and the conventional example. The thickness of the solidified shell was determined by the sulfur print method with iron sulfide added as a tracer at predetermined time intervals. A, B, and C in FIG.
The measured values of the solidified shell thickness at the positions indicated by A, B, and C, where A is the position in contact with the mold on the long side of the slab, B is the position on the long side of the slab and in contact with the mold immediately above the dovetail-shaped depression, C Is a position in contact with the dummy bar head.

As shown in FIG. 7, when the dummy bar head is cooled, the cooling is greatly promoted, the thickness of the solidified shell is increased, and the second embodiment using spray water cooling is also used.
In Example 1, cooling was further promoted than in Example 1, and a strong solidified shell was formed. As a result, in the conventional method, ten iron rods, three spring steels, and 300 g of iron coins were installed in the mold as the coolant, but in Examples 1 and 2, the coolant in the mold was completely omitted. As a result, the installation work of only the sealing material was performed, and the installation work was greatly reduced.

In the prior art, the slab drawing speed at the start of casting is stopped without drawing until one minute has elapsed from the start of casting into the mold, and then stopped at a drawing speed of 0.3 m / min for 30 seconds. Drawing, and then 0.1 m /
min, the drawing speed is increased to 1.6% of the steady speed.
It took 8 minutes to reach m / min, but in Examples 1 and 2, it stopped without pulling out until 1 minute passed from the start of casting into the mold, and then stopped at a steady speed of 1.6.
The speed could be increased to m / min at a stretch, and the efficiency of the continuous casting machine could be greatly improved.

FIG. 8 shows the result of investigating the effect of the thickness of the solidified shell on the composition of the contact portion of the molten metal. In Example 3 using cast steel, a slight solidification delay was observed as compared with Example 1 using a copper alloy. However, the cooling capacity was greatly increased as compared with the conventional example, and it was confirmed that the effect was sufficiently exhibited even when the molten metal contact portion was cast steel. Note that FIG.
It is a measurement of the solidified shell thickness at the location.

[0030]

According to the present invention, the cooling inside the mold at the start of casting can be enhanced, and as a result, the work of installing the coolant can be omitted, and the slab is drawn at the start of casting. The speed can be set to the steady drawing speed early,
The efficiency of the continuous casting machine can be greatly increased.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view showing an example of an embodiment of a dummy bar head according to the present invention.

FIG. 2 is a schematic plan view showing an example of an embodiment of a dummy bar head according to the present invention.

FIG. 3 is a perspective view of a dummy bar head as viewed from a direction S in FIG. 1;

FIG. 4 is a schematic side view showing a state where a dummy bar having the dummy bar head of the present invention attached to an upper end portion is inserted into a continuous casting machine.

FIG. 5 is a diagram showing the results of an investigation on the relationship between data on the high-temperature tensile strength of steel and the presence or absence of defects in the fins.

FIG. 6 is a diagram showing a dummy bar head cooling water amount and a spray cooling water amount in the example of the present invention.

FIG. 7 is a diagram showing a change in the thickness of a solidified shell from the start of casting in comparison with an example and a conventional example.

FIG. 8 is a diagram showing the influence of the thickness of the solidified shell by the composition of the molten metal contact portion in the continuous casting practiced in the present invention in comparison with a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dummy bar head 2 Head main body 3 Melt contact part 4 Reinforcement material 5 Plating layer 6 Water path 7 Spray nozzle 8 Water path 9 Dovetail-shaped depression 10 Groove 12 Mold 12 Mold 19 Sealing material

Claims (4)

[Claims] 1. A dummy bar head for continuous casting, wherein a water passage is provided therein, and water is cooled by cooling water passing through the water passage. 2. The dummy bar head for continuous casting according to claim 1, wherein the contact portion with the molten metal is made of copper or a copper alloy. 3. The dummy bar head for continuous casting according to claim 2, wherein plating is applied to a surface of said copper or copper alloy. 4. The dummy bar head for continuous casting according to claim 1, further comprising a spray nozzle for spraying cooling water.