JP4521266B2 - Manufacturing method of continuous casting mold - Google Patents

Description

The present invention relates to a method for producing a continuous casting mold for casting molten steel.

2. Description of the Related Art Conventionally, a continuous casting mold (hereinafter also simply referred to as a mold) has a mold body made of a plate material made of copper or a copper alloy in order to cast molten steel.
The main component of this plate material is Cu, but in order to increase the strength, for example, some of which Cr and Zr are added, respectively. However, since the molten steel contact surface side of the plate material is worn by the slab and powder obtained by casting the molten steel, for example, a spray coating of a Ni-based self-fluxing alloy is formed (for example, see Patent Document 1). .
Such a sprayed coating is generally formed on a surface of a plate material after blasting. And after forming the sprayed coating on the plate material, a heat treatment of about 1000 ° C., that is, a fusing treatment is performed. In addition, after the fusing process is completed, the plate material is air-cooled (for example, about 20 ° C./min).
Thereby, the thermal spray coating can be remelted, and the adhesion strength between the plate material and the thermal spray coating, which are problematic during thermal spraying, and the strength of the thermal spray coating can be improved.

JP-A-63-35762

However, since the fusing treatment is performed in a high temperature region as described above, the plate material is recrystallized, and the strength of the plate material is reduced by, for example, about 50% compared to the case where the plate material is not treated. For this reason, when casting molten steel using a mold composed of a plate material that has been subjected to fusing treatment, there is a concern that cracks may occur at an early stage, particularly at the meniscus (molten metal surface) portion of the plate material with a large thermal load. Life may be reduced.

The present invention has been made in view of such circumstances, and provides a method for producing a continuous casting mold that can suppress, further prevent, and prevent a decrease in strength of a plate material and maintain stable quality for a longer period of time than before. Objective.

The method for manufacturing a continuous casting mold according to the first invention in accordance with the first object is to form a sprayed coating on the molten steel contact surface side of a plate material made of copper or a copper alloy constituting a mold body for casting molten steel, and to perform heat treatment. In the continuous casting mold manufacturing method to be performed,
While maintaining the cooling state of at least the meniscus part of the plate material, the other part (all except the meniscus part or a necessary part excluding the meniscus part) is heat-treated.
Here, the meniscus portion of the plate means a position in the vicinity of the molten metal surface of the molten steel supplied into the mold body when casting the molten steel.

In the method for producing a continuous casting mold according to the first aspect of the invention, the cooling of the meniscus portion is preferably performed by arranging a water cooling means capable of surface contact with the meniscus portion.
Here, the water-cooling means may protrude from the meniscus portion as long as it can come into surface contact with the meniscus portion of the plate material.

In the method for producing a continuous casting mold according to the first invention, the plate material is a copper alloy containing Cr and Zr, and the temperature of the meniscus portion during the heat treatment of the plate material is 500 ° C. or less. Is preferred.
Here, the copper alloy containing Cr and Zr is a conventionally used chromium zircon copper, and is a precipitation hardening type copper alloy.

In the method for manufacturing a continuous casting mold according to the first aspect of the present invention, since other portions are heat-treated while maintaining the cooling state of at least the meniscus portion of the plate material, the meniscus portion of the plate material which is the most problematic when casting molten steel is used. Adhesion between the plate material and the sprayed coating can be improved while suppressing recrystallization. Thereby, since the strength reduction of the plate material due to recrystallization can be suppressed and further prevented, a continuous casting mold capable of maintaining stable quality for a longer period than before can be manufactured.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is an explanatory view of a method for manufacturing a continuous casting mold according to the first embodiment of the present invention, and FIGS. 2A and 2B respectively apply the method for manufacturing the continuous casting mold. A side view, a front view, and FIG. 3 of the water cooling means are explanatory views of a method for producing a continuous casting mold according to the second embodiment of the present invention.

As shown in FIG. 1, the continuous casting mold manufacturing method according to the first embodiment of the present invention is sprayed on the molten steel contact surface 11 side of a plate material 10 made of a copper alloy constituting a mold body for casting molten steel. A method of performing heat treatment by forming a coating film 12 and heat-treating other parts while maintaining a cooling state of at least a meniscus portion (for example, a range of 1 m from the end of the plate material 10) 13 of the plate material 10. It is. This will be described in detail below.

The mold body has a pair of short piece members arranged at a predetermined interval and a pair of long piece members arranged so as to sandwich the pair of short piece members from both sides. As a result, the portion surrounded by the pair of short piece members and the pair of long piece members has a substantially rectangular shape (for example, a square or a rectangle) in a plan view. Corresponding slabs are produced.
Each of the short piece member and the long piece member is composed of a plate material 10 made of a copper alloy and a stainless back plate (not shown) attached to the back side of the plate material 10.
Various treatments of the plate material 10 will be described below.

First, Ni electroplating is performed on the molten steel contact surface 11 side of the plate material 10 (the surface side facing the plate material 10 at the time of assembling the mold body), except for the upper part when the mold body is configured. The copper alloy constituting the plate material 10 is called chromium zircon copper containing Cr and Zr, and is a precipitation hardening type copper alloy. In addition, as content of Cr and Zr, it is Cr: 0.5 mass% or more and 1.5 mass% or less, for example, Zr: 0.08 mass% or more and 0.30 mass% or less.
Then, a blasting process is performed on the plating surface, and further, a thermal spray coating 12 made of a metal (alloy) or ceramics according to the application of the mold body is formed, and then a heating process of about 1000 ° C., that is, a fusing process is performed.

When performing this fusing process, the water cooling means 14 is disposed on the meniscus portion 13 of the plate 10. As shown in FIGS. 1, 2 (A) and 2 (B), the water cooling means 14 includes a plate-shaped water cooling jacket (also referred to as a water cooling plate) 15 disposed on the molten steel contact surface 11 side of the plate member 10, and the plate member 10. And a support plate 16 disposed on the other side of the plate 10. The plate 10 is disposed so as to sandwich the plate 10 from both sides, and then is positioned by a plurality of bolts 17 and nuts 18 attached to both sides of the plate 10 in the width direction. Is fixed.
The water cooling jacket 15 is made of copper or a copper alloy, the width W1 is wider than the width W2 of the plate 10 (for example, 20 cm or more and 50 cm or less wider than the width W2), and the length L is at least the meniscus portion of the plate 10. 13 is a length covering the vertical direction (for example, 30 cm or more and 100 cm or less), and the thickness thereof is, for example, 3 cm or more and 10 cm or less.

A zigzag water guide hole (not shown) is formed inside the water cooling jacket 15, and a water supply port 19 and a water discharge port 20 of the water guide hole are provided in the side wall portion 21 of the water cooling jacket 15. A water supply pipe 22 is connected to the supply port 19, and a water discharge pipe 23 is connected to the water discharge port 20. When the water cooling jacket 15 is used, a pump (not shown) is operated and the cooling water is continuously supplied to the water supply pipe 22 so that the cooling water passes through the water guide hole and then the water discharge pipe 23. Discharged from. Since the water cooling jacket 15 can be brought into surface contact with the plate material 10, the cooling efficiency of the plate material 10 can be increased.
Further, the support plate 16 is made of stainless steel, the width thereof is substantially the same as that of the water cooling jacket 15, the length thereof is equal to or longer than that of the water cooling jacket 15, and the thickness thereof is, for example, 1 cm or more and 5 cm or less. Yes.

After the water cooling means 14 is arranged so that the surface 24 of the water cooling jacket 15 covers the meniscus portion 13 of the plate member 10, the position is fixed using a plurality of bolts 17 and nuts 18, and the water cooling means 14 is mounted. The plate material 10 in a state of being put is inserted into a heat treatment case 25 made of, for example, steel or refractory.
Then, after the plate material 10 is charged into the heat treatment case 25, the inside is filled with an inert gas (preferably argon gas), and this is charged into an electric furnace (not shown) to perform a fusing process.
Since the cooling water is supplied to the cooling jacket 15 before the fusing process is started, the cooling state of at least the meniscus portion 13 of the plate 10 is maintained. For this reason, a normal fusing process is performed on the plate material 10 other than the meniscus portion 13 (other parts).

In this fusing process, since the processing temperature is high, the meniscus portion 13 of the plate 10 being cooled also rises in temperature, but the amount of cooling water supplied so that the temperature is 500 ° C. or less. Adjust with a pump.
Here, when the temperature of the meniscus portion 13 of the plate member 10 exceeds 500 ° C., recrystallization occurs and the strength may be reduced. On the other hand, the lower limit is not specified because there is no problem even at room temperature, but in reality, it is about 100 ° C., and further about 200 ° C.
From this, in order to suppress and further prevent a decrease in the strength of the meniscus portion 13 of the plate member 10, the temperature is preferably set to 470 ° C. or lower, more preferably 450 ° C. or lower.

The plate material 10 that has been subjected to the fusing treatment by the above method is taken out of the electric furnace together with the heat treatment case 25, and the plate material 10 is further taken out of the heat treatment case 25. Then, after the cooling water is continuously supplied until the temperature of the entire plate 10 becomes, for example, 500 ° C. or less, the plate 10 is further cooled to about room temperature and used for assembling the mold body.
As described above, the meniscus portion 13 of the plate member 10 is always kept in the cooling state even during the fusing process, so that the influence of the temperature due to the fusing process is small, and the strength reduction can be suppressed and further prevented.

Next, a method for manufacturing a continuous casting mold according to the second embodiment of the present invention will be described.
As shown in FIG. 3, the continuous casting mold manufacturing method according to the second embodiment of the present invention is sprayed on the molten steel contact surface 31 side of a plate 30 made of a copper alloy constituting a mold body for casting molten steel. In this method, the coating film 32 is formed and heat treatment is performed. After the heat treatment is performed on the plate 30, the water cooling treatment is further performed at a cooling rate of 10 ° C./second or more. This will be described in detail below.

First, the plate material 30 having the sprayed coating 32 formed on the molten steel contact surface 31 side is charged as it is into a heat treatment case 33 made of, for example, steel or refractory by the above-described method. Then, after charging the plate material 30 into the heat treatment case 33, the inside is filled with an inert gas (preferably argon gas), this is charged into an electric furnace, and is heated at about 1000 ° C., that is, Perform the fusing process.
Then, the plate material 30 after the fusing process is taken out from the electric furnace together with the heat treatment case 33, and after the plate material 30 is taken out from the heat treatment case 33, it is directly put into a water storage tank (not shown) and subjected to water cooling treatment.

In the water cooling treatment, the cooling rate of the plate 30 is set to 10 ° C./second or more.
Here, when the cooling rate of the plate 30 is less than 10 ° C./second, the crystal grains are coarsened and the strength may be reduced. On the other hand, the upper limit is not specified because there is no problem even if it is larger, but in reality it is about 700 ° C./second, and further about 500 ° C./second.
For this reason, in order to suppress the strength reduction of the plate member 30, the cooling rate is preferably 50 ° C./second or less, more preferably 100 ° C./second or less (desirably 200 ° C./second or less).
The plate material 30 manufactured by the above method is used for assembling the mold body.
Thus, since the water-cooling process is performed on the plate material 30 after the fusing process, the solution of the crystal grains in the cooling process can be sufficiently formed, and the decrease in strength can be suppressed.

Next, examples carried out for confirming the effects of the present invention will be described.
Here, a plate material in which the meniscus portion of the plate material is locally cooled (temperature: 450 ° C.) and a rapid cooling after the heat treatment (cooling rate: 50 ° C./second) on the basis of the plate material not subjected to heat treatment (fusing treatment) Each of the physical property values was examined by using the obtained plate material as an example and using a conventional heat-treated material that is not cooled as a comparative example.

As is apparent from Table 1, the conventional heat-treated material has a 0.2% proof stress reduced by about 50% and a tensile strength by about 30% compared to a plate material that has not been heat-treated. As a material of the main body, an undesirable result was obtained.
On the other hand, by locally cooling the meniscus part of the plate material that is out of the application range of the thermal spray coating, both 0.2% proof stress and tensile strength are obtained in the same value as the plate material not subjected to heat treatment. It was confirmed that the strength reduction could be completely prevented. In addition, by rapidly cooling the plate material after the heat treatment, it is possible to recover the 0.2% proof stress to 85% and the tensile strength to 91% as compared with the plate material not subjected to the heat treatment by further aging. It could be confirmed.

Then, the result of having examined the fatigue life of a board | plate material is demonstrated.
When casting molten steel, thermal stress is generated in the plate due to the thermal load during casting, and the surface of the plate near the meniscus portion having a particularly high temperature slightly reaches the plastic region. At this time, the plate is subjected to repeated hot and cold loads. For this reason, cracks occur on the surface of the plate material due to low cycle fatigue failure. Further, the lower the 0.2% proof stress, the more plastic strain occurs and the fatigue life decreases.
Therefore, for the above four types of plate materials, the amount of strain generated near the surface of the plate surface by elasto-plastic FEM analysis under general heat load conditions (maximum temperature of the meniscus portion of about 350 ° C.) and restraint conditions ( Elastic strain + plastic strain), and fatigue life was compared by Manson's common gradient method.

As is clear from Table 2, the plate material obtained by locally cooling the meniscus portion of the plate material has less strain (0.12%) than the conventional heat-treated material, and is equivalent to the plate material that has not been heat-treated. Numerical values were obtained. For this reason, the fatigue life was 152 times that of the conventional heat-treated material, and it was confirmed that the life of the plate material can be very long.
In addition, the plate material that is rapidly cooled after the heat treatment and further uses the subsequent aging has less strain (0.15%) than the conventional heat treatment material, and is less than the plate material that is not heat-treated. As a result, a slight decrease was obtained. For this reason, the fatigue life was 47 times that of the conventional heat-treated material, and it was confirmed that the life of the plate material could be extended.
As described above, the plate material of the present embodiment can greatly improve the fatigue life as compared with a normal heat-treated plate material, and can produce a continuous casting mold capable of maintaining stable quality for a longer period than before.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, the case where the manufacturing method of the continuous casting mold of the present invention is configured by combining a part or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention. Further, the shape of the opening of the mold body can be variously changed according to the cross-sectional shape of the slab to be manufactured.
In the above embodiment, the case where the plate material processed in the above embodiment is used as the plate material of each short piece member and each long piece member of the mold main body has been described. However, each short piece member and each long piece member It is also possible to use a plate material that has been processed in the above embodiment as any one of the plate materials.

And in the said embodiment, although the width | variety, length, and thickness of a board | plate material, a water cooling jacket, and a support plate were described, these numerical values are not limited to this, The mold main body which casts molten steel Various changes can be made according to the specifications.
Furthermore, in the said embodiment, although the case where the board | plate material was comprised with the copper alloy containing Cr and Zr was demonstrated, you may comprise with the copper alloy in which another element is contained, and others as a copper alloy. Of course, it is possible to make it from a copper alloy of the above, or even from copper alone.

It is explanatory drawing of the manufacturing method of the casting mold for continuous casting which concerns on the 1st Embodiment of this invention. (A), (B) is the side view and front view of the water cooling means which apply the manufacturing method of the casting mold for continuous casting, respectively. It is explanatory drawing of the manufacturing method of the casting mold for continuous casting which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

10: plate material, 11: molten steel contact surface, 12: sprayed coating, 13: meniscus portion, 14: water cooling means, 15: water cooling jacket, 16: support plate, 17: bolt, 18: nut, 19: water supply port, 20 : Water discharge port, 21: Side wall, 22: Water supply pipe, 23: Water discharge pipe, 24: Surface, 25: Heat treatment case, 30: Plate material, 31: Molten steel contact surface, 32: Thermal spray coating, 33: Heat treatment case

Claims (3)

In the method for producing a continuous casting mold for performing a heat treatment by forming a thermal spray coating on the molten steel contact surface side of a plate material made of copper or copper alloy constituting a mold body for casting molten steel,
A method for producing a casting mold for continuous casting, characterized in that at least a meniscus portion of the plate material is maintained in a cooled state while other portions are heat-treated. 2. The method for producing a continuous casting mold according to claim 1, wherein the cooling of the meniscus portion is performed by arranging a water cooling means capable of surface contact with the meniscus portion. 3. The method for manufacturing a continuous casting mold according to claim 1, wherein the plate material is a copper alloy containing Cr and Zr, and the temperature of the meniscus portion during the heat treatment of the plate material. The manufacturing method of the casting mold for continuous casting characterized by making it 500 degrees C or less.

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