JP2022177469A - Manufacturing method for thin casting piece, and twin roll-type continuously casting apparatus - Google Patents

Abstract

To provide a manufacturing method for a thin casting piece that can suppress a thickness of a thin casting piece from becoming thinner when starting casting, so as to start casting stably.SOLUTION: A manufacturing method for a thin casting piece, which supplies molten metal to a molten metal pool section formed of a pair of rotary cooling rolls and a pair of side weirs and forms and grows solidifying shells on peripheral surfaces of the cooling rolls so as to manufacture a thin casting piece, includes a side weir preheating step of heating the side weirs when starting casting, where gas around the side weirs is suctioned, in at least an area where surface temperatures of the side weirs are 400°C or higher, in the side weir preheating step.SELECTED DRAWING: None

Description

The present invention provides a thin cast strip manufacturing method for manufacturing thin cast strips by supplying molten metal to a molten metal pool formed by a pair of cooling rolls and a pair of side weirs, and a twin roll type continuous casting apparatus. It is about.

As a method for producing a thin cast piece of metal, a cooling roll having a water cooling structure is provided inside, molten steel is supplied to a molten metal pool formed between a pair of rotating cooling rolls, and molten steel is applied to the peripheral surface of the cooling roll. A twin-roll continuous casting machine that forms and grows a solidified shell, joins the solidified shells formed on the outer peripheral surfaces of a pair of cooling rolls at roll kiss points, and rolls them down to produce a thin cast slab with a predetermined thickness. is provided.

When casting is started in the twin roll continuous casting method described above, the temperatures of the cooling rolls and the side dams are low, so the molten metal solidifies in the vicinity of the side dams, and base metal is generated and grown on the surface of the side dams. tends to be easier.
In addition, since the molten metal flow tends to stay in the vicinity of the width end of the molten metal pool portion, for example, if a solidified piece formed on the surface of the cooling roll is separated by the injected molten steel flow and floats in the molten metal, this may occur. The solidified pieces agglomerate in the vicinity of the width end of the molten steel pool and deposit on the surface of the side dam, promoting the growth of bare metal.

When this ingot grows and fuses with the solidified shell on the peripheral surface of the rotating chill roll at the end of the chill roll, the ingot is peeled off from the surface of the side weir and is bitten into the roll kiss point together with the solidified shell. sent downwards. At this time, when trying to pass the thick base metal, the gap between the rolls temporarily expands beyond the original thickness of the thin cast strip, and in the part where the base metal is not involved (for example, the central part in the width direction), It contains a lot of solidified molten steel. This is called a hot band. Since this hot band is fragile at high temperatures, it may break due to the weight of the thin cast slab.

In order to prevent breakage due to hot bands and to achieve stable casting, it is important to prevent generation of bare metal on the side weirs. A hot band is likely to occur when the molten metal level is unstable, and the base metal generated in the side weir is peeled off. Similarly, it tends to occur while the molten metal level rises in the initial stage of casting. This is because the molten steel contacts and cools the surface of the side dam, which has not been in contact with molten steel until then, and base metal is likely to be generated.
Here, as a method for preventing breakage of thin cast slabs due to hot bands, for example, Patent Document 1 discloses that the side dams are sufficiently preheated to suppress the generation of ingots on the surface of the side dams at the start of casting. A means to do so has been proposed.

JP-A-62-124051

By the way, in the twin roll continuous casting method described above, if deposits are present on the surface of the cooling rolls, the deposits may act as heat transfer resistance and reduce the thickness of the thin cast slab. For this reason, conventionally, the surface of the cooling roll is pickled to remove deposits on the surface of the cooling roll before starting casting.
However, even if the surface of the cooling roll is sufficiently pickled, the thickness of the thin cast slab corresponding to one rotation of the roll becomes thin at the start of casting, and the thin cast slab breaks, sometimes making it impossible to start casting. . In particular, δ-solidification steel has a low high-temperature strength, so thin cast slabs tend to break easily.

The present invention has been made in view of the circumstances described above, and is capable of suppressing the thickness of a thin cast slab from being thinned at the start of casting, thereby enabling stable casting to be started. and a twin roll type continuous casting apparatus.

In order to solve the above-described problems, the present inventors have made intensive studies and obtained the following findings.
As a result of examining the surface of the cooling roll before starting casting, it was found that the binder component (mainly carbon) of the side dam was adhered as deposits.
That is, as shown in Patent Document 1, the side dams are installed next to the chill roll before casting and are heated to about 1300°C. It is thought to have adhered to It was also found that the volatilization of the binder component is accelerated when heated to 400° C. or higher.

The present invention has been made based on the above findings, and the method for producing a thin cast strip according to the present invention is a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs. A method for producing a thin cast slab by supplying a metal to form and grow a solidified shell on the peripheral surface of the cooling roll to produce a thin cast slab, wherein the side dam is preheated to heat the side dam before starting casting. In the side dam preheating step, gas around the side dam is sucked at least in a region where the surface temperature of the side dam is 400° C. or higher.

According to the method for manufacturing a thin cast slab having the configuration described above, the side dam preheating step for heating the side dam is provided before casting is started. In the above region, since the gas around the side dams is sucked, it is possible to prevent the volatilized binder component from adhering to the cooling roll surface when the side dams are preheated.
Therefore, it is possible to prevent the thickness of the thin cast slab from becoming thin at the start of casting, and to start casting stably.

Here, in the method for producing a thin cast strip of the present invention, in the side dam preheating step, in a region where the surface temperature of the side dam is 800° C. or higher, suction of gas around the side dam is stopped. is preferred.
In this case, in a region where the surface temperature of the side dam is 800° C. or higher, the suction of the gas around the side dam is stopped, so that the temperature drop of the side dam due to the suction can be suppressed, and the side dam can be sufficiently heated. A high-temperature state can be achieved, and generation of base metal at the start of casting can be sufficiently suppressed. In addition, since the binder component of the side weir volatilizes sufficiently in the temperature range of 400°C to 800°C, even if the gas suction is stopped in the region of 800°C or higher, the adhesion of the binder component to the chill roll surface is suppressed. can do.

Further, in the method for producing a thin cast strip of the present invention, the thin cast strip may be delta-solidification steel.
δ-solidification steel has low high-temperature strength, so it is a type of steel that tends to cause breakage of thin cast slabs at the start of casting. Therefore, by applying the thin cast slab manufacturing method of the present invention, it is possible to suppress the thickness of the thin cast slab from becoming thin at the start of casting. can do.

The twin-roll continuous casting apparatus of the present invention supplies molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs to form and grow a solidified shell on the peripheral surface of the cooling rolls. A twin-roll continuous casting apparatus for producing thin-walled cast slabs, comprising: side dam preheating means for heating the side dam before starting casting; temperature measuring means for measuring the surface temperature of the side dam; It is preferable to include suction means for sucking ambient temperature gas of the side weir in a region where the surface temperature of the side weir is 400° C. or higher.

According to the twin-roll continuous casting apparatus having this configuration, before starting casting, the side dam preheating means for heating the side dam, the temperature measuring means for measuring the surface temperature of the side dam, and at least the surface of the side dam are heated. and a suction means for sucking the ambient temperature gas of the side dams in a temperature range of 400° C. or higher. adhesion of the binder component can be suppressed.
Therefore, it is possible to prevent the thickness of the thin cast slab from becoming thin at the start of casting, and to start casting stably.

As described above, according to the present invention, there is provided a method for manufacturing a thin cast slab, which is capable of suppressing reduction in the thickness of the thin cast slab at the start of casting and allowing stable start of casting; A twin roll continuous casting apparatus can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an example of a twin-roll continuous casting apparatus according to an embodiment of the present invention; FIG. 2 is a cross-sectional explanatory view of the vicinity of a molten steel pool portion in the twin-roll continuous casting apparatus shown in FIG. 1; FIG. 2 is a perspective explanatory view of the vicinity of a molten steel pool portion in the twin-roll continuous casting apparatus shown in FIG. 1; FIG. 2 is an explanatory view showing a molten steel pool and base metal in the twin-roll continuous casting apparatus shown in FIG. 1; (a) shows the shape of the molten steel pool, and (b) shows the base metal formed on the surface of the side weir. 1 is a schematic explanatory diagram of side dam preheating means, temperature measuring means, and suction means in a twin-roll continuous casting apparatus according to an embodiment of the present invention; FIG. (a) is a side view, and (b) is a front view.

EMBODIMENT OF THE INVENTION Below, the manufacturing method of the thin cast piece which is embodiment of this invention, and a twin-roll continuous casting apparatus are demonstrated with reference to attached drawings. In addition, this invention is not limited to the following embodiment.
Here, the thin cast slab 1 manufactured in this embodiment is made of steel of various compositions, and has a width of 500 mm or more and 2000 mm or more and a thickness of 1 mm or more and 5 mm or less.
It should be noted that the thin cast slab 1 produced in this embodiment is made of δ-solidification steel in which a δ-phase (δ-Fe) is crystallized as primary crystals during solidification. Examples of the δ-solidifying steel include carbon steel having a carbon content of 0.53 mass% or less, Cr-based stainless steel, and the like.

Next, the twin-roll continuous casting apparatus 10 used in the thin-walled cast product manufacturing method of the present embodiment will be described.
As shown in FIG. 1, a twin roll continuous casting apparatus 10 of this embodiment includes a pair of chill rolls 11, 11, pinch rolls 12, 12 and 13, 13 for supporting a thin cast slab 1, and a pair of It holds the molten steel 3 supplied to the molten steel pool portion 16 defined by the side dams 15 arranged at the widthwise ends of the cooling rolls 11, 11 and the pair of cooling rolls 11, 11 and the side dams 15. and a pouring nozzle 18 for supplying the molten steel 3 from the tundish 17 to the molten steel pool portion 16.

Further, in the twin roll continuous casting apparatus 10 of the present embodiment, a chamber 20 is arranged above the molten steel pool portion 16 and the cooling rolls 11, 11, as shown in FIG.
Since the chamber 20 slides on the cooling roll 11 , a sealing member 25 is arranged between the chamber 20 and the cooling roll 11 to prevent outside air from entering. As the sealing member 25, a refractory fiber sheet, a small brush, or the like can be used.
In the twin-roll continuous casting apparatus 10 of the present embodiment, cooling A brush roll 27 for cleaning the surface of the roll 11 is provided.

In this twin-roll continuous casting apparatus 10, the molten steel 3 is cooled by contacting the rotating chill rolls 11, 11, thereby forming solidified shells 5, 5 on the peripheral surfaces of the chill rolls 11, 11. , solidified shells 5, 5 respectively formed on a pair of cooling rolls 11, 11 are pressed against each other at roll kiss points, whereby a thin cast strip 1 having a predetermined thickness is cast.
The surface of the cooling roll 11 is cleaned by the brush roll 27 each time the cooling roll 11 rotates.

Here, as shown in FIGS. 3 and 4 , a molten steel pool portion 16 is defined by disposing a side weir 15 on the end surface of the cooling roll 11 .
As shown in FIG. 4(a), the molten steel pool portion 16 has two bottom surfaces formed by the peripheral surfaces of the pair of cooling rolls 11, 11, side surfaces held by the surfaces of the side dams 15 on both sides, It has a wedge-shaped shape surrounded by a pair of cooling rolls 11, 11 and a pair of side dams 15 and a rectangular hot water surface.

The molten steel 3 in the molten steel pool portion 16 is originally solidified on the peripheral surface of the cooling roll 11 and drawn downward as a thin cast piece 1 . However, the surface of the side weir 15 forming the side surface of the molten steel pool portion 16 is cooled because it is in direct sliding contact with the end portion of the cooling roll 11, so that the side surface of the molten steel pool portion 16 is cooled as shown in FIG. Ingots 7 tend to form on the surface of the side dam 15 forming the . In particular, the base metal 7 near the sliding contact line with the cooling roll 11 is likely to be connected, and if it irregularly coalesces with the thin cast piece 1 and bites into the cooling roll 11, a hot band may occur, which may cause breakage.

Therefore, in the twin-roll continuous casting apparatus 10 of the present embodiment, as shown in FIGS. A temperature measuring means 31 for measuring the surface temperature of the weir 15 and a suction means 32 for sucking gas around the side weir 15 are provided.

Here, in this embodiment, the side dam preheating means 30 is an electric heater. Also, the temperature measuring means 31 is a thermocouple inserted into the protective tube.
The suction means 32 has a hood disposed above the side weir 15 and is configured to suck the volatilized binder component (gas) from the side weir 15 .

The above-described side dam preheating means 30, temperature measuring means 31, and suction means 32 are detachable, and are installed before starting casting to heat the side dam 15 to a predetermined temperature (for example, 1300° C. or higher). After heating up to , the side dam preheating means 30, the temperature measuring means 31, and the suction means 32 are removed, and as shown in FIG. .

A method for producing a thin cast strip according to the present embodiment using the twin roll continuous casting apparatus 10 described above will be described below.

First, before starting casting, side weirs 15 are arranged at the ends of the pair of cooling rolls 11 , 11 . Then, as shown in FIG. 5, the side weir preheating means 30 is used to heat the side weir 15 (preheating step).
At this time, a temperature measuring means 31 for measuring the surface temperature of the side weir 15 is arranged, and a suction means 32 is arranged above the side weir 15 .

In this preheating step, gas around the side weir 15 is sucked by the suction means 32 in a region where the surface temperature of the side weir 15 measured by the temperature measuring means 31 is at least 400° C. or higher.
In this embodiment, it is preferable to stop the gas suction by the suction means 32 in a region where the surface temperature of the side weir 15 is 800° C. or higher.

Here, when the side dam 15 is heated, the binder component (mainly carbon) contained in the side dam 15 volatilizes. In particular, the binder component volatilizes in a temperature range of 400° C. or higher. In addition, volatilization of the binder component is accelerated in the range of 400° C. or higher to 800° C. or lower.

Therefore, in the present embodiment, in a region where the surface temperature of the side dam 15 measured by the temperature measuring means 31 is at least 400° C. or higher, the gas generated from the side dam 15 is sucked by the suction means 32 so that the side dam 15 is It suppresses the adhesion of the binder component volatilized from the cooling roll 11 to the surface of the cooling roll 11 .
In the region where the surface temperature of the side dam 15 is 800° C. or higher, when the suction of gas by the suction means 32 is stopped, the temperature drop of the side dam 15 due to the suction can be suppressed, and the side dam 15 can be brought to a high temperature state. can be efficiently preheated.

After the side dam 15 is heated to a predetermined temperature (for example, 1300° C. or higher), the side dam preheating means 30, the temperature measuring means 31, and the suction means 32 are removed.
Then, the side weirs 15 are pressed against the end surfaces of the cooling rolls 11, 11 to form molten steel pool portions 16. As shown in FIG. The molten steel 3 is supplied to the molten steel pool portion 16, and the cooling rolls 11, 11 are driven to rotate, so that the thin cast slab 1 is continuously cast.

According to the thin cast strip manufacturing method of the present embodiment configured as described above, in the side dam preheating step for heating the side dam 15 before starting casting, at least the surface temperature of the side dam 15 reaches 400°C. In the above region, since the gas around the side dam 15 is sucked, the binder component volatilized when the side dam 15 is preheated can be sucked, and the binder component on the surface of the cooling roll 11 can be sucked. adhesion can be suppressed.
Therefore, it is possible to prevent the thickness of the thin cast slab 1 from becoming thin at the start of casting, and to start casting stably.

Further, in the present embodiment, in the side dam preheating process, when the suction of gas around the side dam 15 is stopped in the region where the surface temperature of the side dam 15 is 800° C. or higher, the side dam 15 is It can be sufficiently heated to a high temperature state, and generation of base metal 7 at the time of casting can be sufficiently suppressed.

Furthermore, in the present embodiment, when the thin slab 1 is δ-solidification steel, even if the thin slab is δ-solidification steel with low high-temperature strength, it is possible to suppress the thickness of the thin slab from becoming thin at the start of casting. , the casting can be started stably.

According to the twin roll continuous casting apparatus of this embodiment, before starting casting, the side dam preheating means 30 for heating the side dam 15, the temperature measuring means 31 for measuring the surface temperature of the side dam 15, and at least the side In the region where the surface temperature of the weir 15 is 400° C. or more, the suction means 32 for sucking the gas around the side weir 15 is provided, so that the binder component volatilized when the side weir 15 is preheated can be sucked. , and adhesion of the binder component to the cooling rolls 11, 11 can be suppressed. Therefore, it is possible to prevent the thickness of the thin cast slab 1 from becoming thin at the start of casting, and to start casting stably.

The method for producing a thin cast slab and the twin-roll continuous casting apparatus, which are embodiments of the present invention, have been specifically described above, but the present invention is not limited to these. Modifications can be made as appropriate without departing from the technical idea of the invention.
For example, in the present embodiment, as shown in FIG. 1, a twin-roll continuous casting apparatus provided with pinch rolls has been described as an example. may

Further, in the present embodiment, the side dam preheating means is configured by an electric heater, but the configuration of the side dam preheating means is not particularly limited, and other heating means may be applied.
Furthermore, in the present embodiment, the thermocouple inserted in the protective tube is used as the temperature measuring means 31, but the configuration of the temperature measuring means is not particularly limited, and other temperature measuring means can be applied. good too.
In addition, in the present embodiment, the suction means 32 has been described as having a hood disposed above the side dam 15, but is not limited to this, and is configured to be capable of sucking the volatilized binder component from the side dam. It is sufficient if it is

The results of experiments conducted to confirm the effects of the present invention will be described below.
A thin-walled cast piece of carbon steel having a low high-temperature strength and a carbon content of 0.53 mass% or less was produced using the twin-roll continuous casting apparatus shown in the above-described embodiment.

The conditions common to the method for producing thin cast slabs are shown below.
Width of cooling roll: 400mm
Cooling roll diameter: 600mm
Molten steel depth in the molten steel pool: 190mm
Thin cast slab thickness: 2.0 mm
Width of thin cast slab: 400 mm
Casting speed: 40m/min
Casting atmosphere: Ar gas

Then, before starting casting, the side dam was preheated using the side dam preheating means, the temperature measuring means, and the suction means described in the present embodiment. Casting was started when the surface temperature of the side dam reached 1300°C.
At this time, in the temperature range of the surface temperature of the side weir shown in Table 1, the gas around the side weir is sucked by the suction means.

Then, the thickness of the thin cast slab at the start of casting (for one rotation of the cooling roll) and the thickness of the thin cast slab at steady state were measured.
If the thickness of the thin cast slab at the start of casting (for one rotation of the cooling roll) is less than 80% of the thickness of the thin cast slab at steady state, "x" A case in which the thickness of the thin cast slab during rotation) was 80% or more of the thickness of the thin cast slab at steady state was evaluated as "good".

Comparative Examples 1 and 2 in which gas was sucked from the vicinity of the side dams in a region where the surface temperature of the side dams was from room temperature to less than 400°C when preheating the side dams, and no gas was sucked during preheating of the side dams. In Comparative Example 3, the thickness of the thin cast slab at the start of casting (for one rotation of the chill roll) was reduced.
On the other hand, in Example 1-12, in which the gas around the side dam was sucked in a region where the surface temperature of the side dam was 400° C. or higher during the preheating of the side dam, at the start of casting (the temperature of the cooling roll There was no significant difference between the thickness of the thin-walled slab at one rotation) and the thickness of the thin-walled slab at steady state.
Furthermore, in the present invention examples 1-3, 5-7, and 9-11, in which the suction of gas around the side weir was stopped in the region where the surface temperature of the side weir exceeded 800°C when preheating the side weir, the hot band was able to be sufficiently suppressed.

From the above results, according to the present invention, a method for manufacturing a thin cast slab, which can suppress a decrease in the thickness of the thin cast slab at the start of casting and can start casting stably, and It has been confirmed that it is possible to provide a twin roll continuous casting apparatus.

1 thin cast slab 3 molten steel 10 twin roll type continuous casting device 11 cooling roll 15 side weir 16 molten steel pool section 30 side weir preheating means 31 temperature measuring means 32 suction means

Claims (4)

A thin cast slab is produced by supplying molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs to form and grow a solidified shell on the peripheral surface of the cooling rolls. A manufacturing method of
Before starting casting, a side dam preheating step for heating the side dam is provided. In this side dam preheating step, gas around the side dam is sucked at least in a region where the surface temperature of the side dam is 400° C. or higher. A method for producing a thin-walled cast piece, characterized by: 2. The production of a thin cast slab according to claim 1, wherein in the side dam preheating step, suction of gas around the side dam is stopped in a region where the surface temperature of the side dam is 800° C. or higher. Method. 3. The method for producing a thin cast strip according to claim 1, wherein the thin cast strip is delta-solidification steel. A twin roll type in which molten metal is supplied to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, and a solidified shell is formed and grown on the peripheral surface of the cooling rolls to produce thin cast slabs. A continuous casting apparatus,
side dam preheating means for heating the side dam before starting casting; temperature measuring means for measuring the surface temperature of the side dam; and a suction means for sucking the gas of the twin roll continuous casting apparatus.

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