JP2000107843A - Continuous casting roll excellent in cooling power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sticking of scale on a cooling hole by arranging a clamper to a pipe for cooling water, fitting stainless steel-made rings to the clamper, sizing the diameter of the ring to the intermediate size between the outer diameter of the pipe and the diameter of the cooling hole and disposing stainless steel round bars in a space formed with the adjacent rings, the outer diameter of the pipe and the inner wall of the cooling hole. SOLUTION: The clamper 4 projecting to the diameter direction is arranged to the pipe 3 in the inner part of the cooling hole 2 in the continuous casting roll. To the clamper 4, the rings 7-1, 7-2, 7-3 are welded and fixed. The stainless steel round bars 8 are disposed in the spaces between the adjacent rings 7-1 and 7-2 and between the adjacent rings 7-2 and 7-3. The diameter of the stainless steel round bar 8 is sized to >1/2 of the gap size between the outer surface of the pipe 3 and the inner wall of the cooling hole 2 in the continuous casting roll. Applying of knurling or rough shot blasting on the outer cylindrical surface of the stainless steel round bar 8, is desirable because of the improvement of the effect for peeling out the scale.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a cylindrical cooling hole in the direction of the center axis of a roll, inserts a pipe into this hole from one side, opens the opposite end face of the pipe in the cooling hole, and cools the pipe with cooling water. In a continuous casting roll with a structure used as an outgoing flow path or a return flow path, the scale that attaches to and grows on the inner wall of the cooling hole of the roll is suppressed, the cooling capacity is improved, the roll temperature is lowered, and the roll is generated on the roll surface. The present invention relates to a technique for reducing a crack growth rate.

[0002]

2. Description of the Related Art As shown in FIG. 5, in a continuous casting apparatus of a steelmaking facility, molten steel is poured from a ladle 10 into a mold 12 through a tundish 11, and the molten steel is poured into a mold and a continuous casting roll whose inside is cooled by water. 1, the material to be cast, that is, the slab 9 is continuously manufactured by cooling and solidifying with the external spray water disposed between them and pulling them out. The continuous casting roll 1 has a slab of about 2 m / mi.
While correcting the vertical state at a low speed of n or less from a vertical state to a horizontal state that allows easy post-processing, the sheet is drawn and conveyed, and has a role of applying a roll pressure to the slab to finish it to a predetermined thickness. Therefore, the continuous casting roll is subjected to quenching by cooling water spray after contacting the hot slab in one rotation,
While simultaneously receiving the thermal stress and the mechanical bending stress for this repetition, a crack is formed in the roll in the circumferential direction, and the crack develops.

In particular, in recent years, when a full ladle has been cast and a ladle having a different composition is to be cast, molten steel is poured over the tail end of the preceding slab in the mold to continue casting. The operation that is called casting is becoming mainstream. In this case, there is a work of laying a partition iron plate at the seam so that different types of steel do not mix in the mold. At that time, the slab must be stopped for a certain time. This condition is called a machine stop, and the presence of the machine stop makes the thermal stress more severe, and the crack growth speed is increasing.

[0004] Normally, a roll having a diameter of about 400 mm is controlled at a critical depth of a crack of about 40 to 50 mm.
If the crack exceeds this limit, the possibility of breakage of the roll increases, so it is necessary to replace the roll according to the crack depth. In general, since the number of rolls in a continuous casting facility is several hundred in one production line, the cost of replacing and regenerating the rolls is enormous, and extending the life of the rolls is a very important issue. .

In order to reduce the thermal stress generated in the roll, one of the effective means is to reduce the temperature of the roll. In a normal continuous casting roll, a method is used in which a cylindrical hole is formed in the center of the roll in the axial direction, and cooling water is flowed through the hole. As another means, there is a method disclosed in Japanese Utility Model Publication No. 52-56346 in which a spiral cooling groove is provided immediately below the roll surface, and the vicinity of the surface in contact with the slab as a heat input source is cooled to efficiently lower the roll temperature. is there.

[0006]

However, the conventional cooling method has the following disadvantages. That is, the water used for cooling the rolls of the continuous casting equipment is so-called circulating water, which contains a large amount of scale generation sources such as iron oxide powder, calcium, and silica, which adheres to the inner wall of the cooling holes inside the rolls. ·grow up. The growth thickness of this scale is 1
Although it is usually within several mm when used for about a year, the thermal conductivity is extremely low compared to steel because the composition of the scale is mainly composed of oxides, and even a small thickness of the scale leads to a large decrease in cooling capacity. According to the heat conduction analysis results of the present inventors, when the thickness of the scale is 2 mm, the roll surface temperature increases by 70 ° C. as compared with the case without the scale. This temperature difference increases the thermal stress of the roll and has a significant effect on increasing the crack growth rate.

According to the method disclosed in Japanese Utility Model Publication No. 52-56346, when there is no scale adhesion, the roll surface temperature can be reduced by 300 ° C. or more as compared with the case of the center cooling hole.
However, in practice, scale adhesion and
The effect of growth is large, and the desired effect has not been obtained. Further, since this roll has a structure in which a cooling hole is provided in the vicinity of the surface, the size of the cooling hole is inevitably smaller than that in the case where a single hole is provided at the center due to the limitation on the strength of the roll body. . Therefore, particularly in a line having poor water quality, a trouble has occurred in which the hole is closed at a scale that has grown from the entire inner wall of the cooling hole toward the center. In addition, the roll has another drawback that the production and reproduction costs are high, and it is difficult to use the roll on a full-scale production line.

Therefore, the present invention has no these disadvantages.
An object of the present invention is to provide a continuous casting roll that is inexpensive, simple, and has excellent cooling ability that can prevent scale adhesion and growth.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist of the continuous casting roll according to the present invention having excellent cooling ability is as follows.

[0010] A cylindrical cooling hole is provided in the roll central axis direction,
In a continuous casting roll having a structure in which a pipe is inserted into this hole from one side and the opposite end face of the pipe is opened in the cooling hole, and the pipe is used as a flow path or a return flow path for cooling water,
Provide a steady rest that protrudes in the radial direction with respect to the pipe, and attach a stainless steel ring having a diameter approximately between the pipe outer diameter and the roll cooling hole diameter to the steady rest,
A stainless steel round steel having a diameter exceeding 1/2 of the gap between the pipe outer surface and the roll cooling hole inner wall is arranged in a space formed by the axially adjacent ring and the ring and the pipe outer surface and the cooling hole inner wall. Continuous casting roll with excellent cooling capacity.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Normally, a continuous casting roll is driven by a driving roll rotated by an electric motor to maintain the roll spacing, that is, the slab thickness, and to pull out the slab, and only to have a role of maintaining the roll spacing. It consists of a non-driving roll without a source.

According to the present invention, a cylindrical cooling hole is provided in the center axis direction of the roll, a pipe is inserted into this hole from one side, the opposite end face of the pipe is opened in the cooling hole, and the pipe is connected to a cooling water passage. Alternatively, this is performed for a drive roll having a structure used as a return flow path.

Hereinafter, the structure and operation principle of the present invention will be described with reference to FIGS.
A description will be given based on FIG.

Referring to FIG. 4, a description will be given of a normal cooling structure of the drive roll.

A pipe 3 is inserted into a cooling hole 2 provided in the direction of the central axis of the continuous casting roll 1 as a flow path for cooling water. The steady rest 4 is welded and fixed to the pipe so that the pipe does not bend and eccentric inside the cooling hole.
When cooling water flows from the cooling water inlet 13 to the rotary joint 5 in this state, the water is discharged into the cooling hole of the roll through the inside of the pipe as shown by an arrow in the drawing, and then the inner wall of the roll cooling hole and the outer surface of the pipe are removed. It returns to the rotary joint through the space and is discharged from the discharge port 14.

Next, referring to FIG. 1, a description will be given of a technique for preventing scale adhesion on the inner wall of a roll cooling hole according to the present invention.

Stainless steel rings 7-1, 7-2, 7-3 are fixed to the pipe steady rest 4 by welding. The diameter of the center of the ring in the radial direction is set to a value approximately halfway between the cooling hole diameter and the pipe outer diameter. The stainless steel round steel 8 is arranged in the space between the adjacent rings 7-1 to 7-2 and between the rings 7-2 to 7-3.

In this state, when the roll rotates in actual operation, the stainless steel round bars 8 are arranged in a free state in FIGS. 2 and 3, so that the adjacent rings 7-1 to 7-2 are used.
In the space between and between 7-2 and 7-3, the roll is turned and improved along the inner wall of the roll. By doing so, the scale that tends to adhere and grow on the inner wall of the roll is suppressed. Here, the diameter of the stainless steel round steel should be larger than 1/2 of the gap between the roll cooling hole inner wall and the pipe outer surface, and larger than the gap between the ring outer surface and the cooling hole inner wall and the gap between the ring inner surface and the pipe outer surface. The dimensions prevent the stainless steel round steel from coming out of the space and moving in the axial direction, moving to the return flow path side of the rotary joint, and closing the flow path.

By applying knurling or rough shot blasting to the cylindrical surface of the stainless steel round steel, it is possible to further enhance the effect of peeling off the scale that grows on the inner wall of the roll cooling hole 2. Ring 7-
2, 7-3 are halved to surround the pipe and are welded and fixed to the steady rest 4 like a welded portion 15 to facilitate assembly, and then the rings are welded and fixed to each other like a welded portion 16. Is also good. However, in this case, finish so that there is no protrusion of the welded portion between the rings so that the end face of the stainless steel round steel 8 is not caught by the welded portion between the rings and does not rotate smoothly in the space. I have to put it. In addition, a steel having corrosion resistance similar to stainless steel can be used for the ring and the round steel.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific examples of the continuous casting roll according to the present invention having excellent cooling performance will be described below.

The roll is made of JIS SNCM415.
13Cr stainless steel with a thickness of 5 mm weld-welded on the surface layer of the forged material, body length 2300 mm, body diameter 400 m
m, center cooling hole diameter 60 m. The pipe is made of SUS
304, SU as outer pipe with 34mm outer diameter
4mm thick, 25mm long, 11mm high made of S304
Is welded and fixed to a pipe as shown in FIG. The axial spacing between the steady rests in the axial direction is 1210 mm. The ring is made of SUS304 and has an outer diameter of 48.6m
m, the inner diameter was 43 mm, and the thickness was 7 mm. After being halved and fixed by welding to the steady rest of the pipe, the rings were welded and connected, and the surface on the side where the stainless steel round steel was arranged was smoothly finished with a hand grinder. Stainless steel round steel is S
US304, diameter 9mm, length 1190mm,
Knurling was performed on the cylindrical surface.

The average rotation speed of the roll is 0.8 rpm.
m, the flow rate of the cooling water is about 2 m / sec.

Five rolls of the present invention were incorporated into an actual line and traced over one year. As a method of confirming the effect, the rotary joint of the roll was removed every month online, and the inside of the cooling hole was visually observed. The crack depth was measured every three months with a crack meter.

As a result, the scale adhesion thickness on the inner wall of the cooling hole of the conventional roll after one year of use was 3 to 4.5 mm on average. The maximum depth of the crack was 30 to 45 mm. On the other hand, as for the roll of the present invention, as a result of regularly checking the state of scale adhesion, the thickness was stable at 0.5 to 1 mm, and no further growth was observed. In addition, the depth of the crack was 17 to 25 mm at the maximum after one year, and was reduced to about 1 / 1.8 compared with the conventional case.

[0025]

EFFECT OF THE INVENTION By applying the roll of the present invention, the roll production cost increase is substantially zero, the scale adhesion growth on the inner wall of the cooling hole provided in the roll central axis direction is suppressed, the crack growth rate is reduced, and the roll life is reduced. Was able to be extended about 1.8 times.

[Brief description of the drawings]

FIG. 1 shows the structure of a continuous casting roll of the present invention.
FIG. 3 is an axial cross-sectional view showing the inside of a cooling hole in an enlarged manner.

2 is an enlarged cross-sectional view at right angles to an axis inside a cooling hole showing a structure of a continuous casting roll of the present invention, and is a cross-sectional view corresponding to a cross section AA in FIG. 1;

FIG. 3 is an enlarged cross-sectional view at right angles to an axis inside a cooling hole showing a structure of a continuous casting roll of the present invention, and is a cross-sectional view corresponding to a cross section BB of FIG.

FIG. 4 is an axial sectional view showing a conventional internal cooling structure of a driving roll.

FIG. 5 is a diagram showing an outline of a configuration of a continuous casting facility.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 continuous casting roll 2 continuous casting roll cooling hole 3 pipe 4 steady rest 5 rotary joint 6 bearing 7 ring 8 stainless steel round bar 9 slab 10 ladle 11 tundish 12 mold 13 cooling water inlet 14 outlet 15 welding part (ring Welding to steady rest) 16 Welded part (weld between rings)

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yasunori Miyamoto 1 Kimitsu, Kimitsu City Inside the Nippon Steel Corporation Kimitsu Works (72) Inventor Masao Ichiki 1 Kimitsu, Kimitsu City Nippon Steel Corporation F term in Tsu Works (reference) 4E004 LC03

Claims (1)

[Claims] 1. A cylindrical cooling hole is provided in the roll center axis direction, a pipe is inserted into this hole from one side, the opposite end face of the pipe is opened in the cooling hole, and the pipe is connected to a cooling water going flow path or return. In a continuous casting roll having a structure used as a flow path, a steady rest that protrudes in the radial direction with respect to the pipe is provided, and a stainless steel ring having a diameter approximately between the pipe outer diameter and the roll cooling hole diameter is provided on the steady rest. A stainless steel round steel having a diameter exceeding 1/2 of the gap between the pipe outer surface and the roll cooling hole inner wall is disposed in the space formed by the ring and the ring and the pipe outer surface and the cooling hole inner wall which are axially adjacent to each other. A continuous casting roll with excellent cooling performance.