JPH09192808A - Roll for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roll excellent in crack resistance, heat resistance, wear resistance and corrosion resistance, in the roll for continuous casting used to transport a high temp. material. SOLUTION: The surface layer part 3 of the roll 1 for continuous casting is coated with a build-up layer of a material provided with the heat resistance, wear resistance and corrosion resistance and U shape grooves 4 are engraved on the circular direction of the coated surface layer part in the same interval pitch and spiral cooling hole 5 is arranged on the surface of a roll barrel part 2. The values of the groove depth D of the U shape groove 4, the pitch (p) of the grooves and the width (h) of projected part of the groove are made to 5<=D<=10 (mm), 10<=p<=20 (mm) and 5<=h<=3p/4(mm). By this method, the developments of crack and wear on the roll surface are reduced and the service life is drastically extended and the machining is easily executed and the manufacturing cost can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting roll used for conveying high temperature materials in continuous casting of steel.

[0002]

2. Description of the Related Art In a continuous casting apparatus, a continuous casting roll such as a pinch roll or a guide roll for continuously drawing a high temperature slab from a mold directly below a tundish and conveying it along a line is It is repeatedly subjected to heating by contact and cooling by cooling water or cooling.

Recently, from the viewpoint of improving the operating efficiency and the thermo-economical efficiency, the so-called direct feed rolling, in which the continuously cast slab is fed to the rolling process without being cooled, is maintained. The trend is toward higher speeds, and along with this, the temperature and speed of continuous casting operations have increased significantly.

The cause of the deterioration of the rolls used for continuous casting or the like is not due to wear, but most of them are due to cracks due to this thermal stress. It has been used that the surface of the roll main body is coated with a built-up layer made of a stainless steel-based alloy material to improve the heat resistance and oxidation resistance of the surface.

As a roll used for these purposes,
For example, there is a continuous casting roll disclosed in JP-A-55-156654. This roll is a roll for continuous casting characterized in that a roll shaft having a cooling water hole in the shaft center part, or a weld overlay having a recess is formed on the outer surface of a sleeve fitted to the roll shaft. .

Further, in the continuous casting roll disclosed in JP-A-62-230462, the surface of the roll body is covered with a composite build-up layer in which metal and ceramic particles are mixed, and this composite build-up layer is formed. It is characterized in that grid-like grooves are formed, and the depth (D) of the grooves is D> t with respect to the layer thickness (t) of the composite overlay layer, and the depth (D 1) or a plurality of grooves having a depth (d) are formed between the grooves of (4), and the depth (d) of the grooves is D> d. is there.

[0007]

By the way, the former continuous casting roll has a roll structure in which cooling water holes are provided only in the axial center portion, and since the high temperature slab is in contact with the roll,
With a cooling structure having only the axial center portion, the cooling function is insufficient, cracks are rapidly generated on the roll surface, and it is difficult to delay the crack generation. Further, in the structure in which a large number of dents are provided on the roll surface, there is a problem in that the machining time for creating the dent shape takes a long time, resulting in high manufacturing cost.

In the latter continuous casting roll, the surface of the roll main body is a composite built-up layer of metal and ceramic particles, and since the high temperature slab comes into contact with the roll, it is a metal system having heat resistance, abrasion resistance and corrosion resistance. Cracks are generated earlier than in the overlay layer, and it is difficult to delay the generation of cracks and prevent crack propagation. Further, forming the grid-shaped grooves has a problem that the machining time is long and the manufacturing cost is high.

In continuous casting of steel and the like, when the continuously cast slab is constantly pulled out and conveyed at about 1000 to 1400 ° C., the surface temperature of the roll is heated to about 400 to 1000 ° C. Under these conditions, conventional rolls undergo thermal fatigue, hot wear, and corrosion as the slab is pulled out and transported, cracks and wear on the roll surface become noticeable, and stable continuous casting operations are performed. Is difficult.

The present invention solves the above-mentioned problems and improves the cooling effect of the roll surface layer portion without performing complicated processing,
Provide a continuous casting roll having excellent cracking resistance, heat resistance, abrasion resistance, and corrosion resistance.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a roll surface layer is coated with a built-up layer of a material having heat resistance, abrasion resistance and corrosion resistance, and the coated surface layer portion is formed in a circumferential direction. U of constant depth
The continuous casting roll is characterized in that character-shaped grooves are formed at equal pitches, and further spiral cooling holes are provided on the surface of the roll body.

Further, in the above continuous casting roll, the groove depth (D) of the U-shaped groove formed in the surface layer of the roll,
The values of the groove pitch (p) and the groove convex width (h) are 5 ≦ D ≦
10 (mm), 10 ≦ p ≦ 20 (mm), p / 4 ≦ h ≦
It is a roll of 3p / 4 (mm).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a continuous casting roll according to the present invention is shown in FIG. 1 (a), a perspective view of the roll outer shape, (b) a roll sectional view showing details of cooling holes, and (c) a groove shape. Will be described with reference to a cross-sectional view showing the details.

The dimensions of a commonly used continuous casting roll are as follows: roll diameter φ250-360 mm, roll width 1
It is about 800 to 2200 mm, and as the material used for the roll 1, the roll body 2 is made of heat-resistant steel,
The material of the overlay layer 3a of the surface layer portion 3 is a Ni—Cr-based overlay material having heat resistance and abrasion resistance.

When observing a flat roll as described later, cracks generally occur in the circumferential direction. In the present invention, the crack stress is relaxed by first forming a groove in the circumferential direction. The U-shaped groove 4 formed in the roll 1
Are engraved on the build-up layer 3a on the roll body 2 at a constant depth in the circumferential direction and at equal pitches. The dimensions of the grooves 4 are groove depth (D) and groove pitch (p), respectively. , As the width (h) of the convex portion of the groove, 5 ≦ D ≦ 10 (mm), 10 ≦ p ≦ 20
(Mm) and p / 4 ≦ h ≦ 3p / 4 (mm).

Here, the groove 4 has a U-shaped cross-section so as to avoid the acute groove shape which is vulnerable to cracking and corrosion, to relieve the mechanical and thermal stress applied to the roll surface, and smoothly transmit it to the base material. This is because.

The groove depth (D) is determined from the viewpoints of strength and workability, that the surface overlaying layer 3a is usually laminated to a thickness of 10 to 20 mmt, and that the thermal stress is relaxed. 5-10 mm is suitable.

Further, the groove pitch (p) and the width of the groove protrusion (h)
Similarly, from the viewpoints of strength and workability, relaxation of thermal stress, and the relationship between the groove pitch and the width of the convex portion, the groove pitch was set to 10 to 20 mm, and the width of the convex portion was set to 5 to 15 mm at the maximum.

Thus, by engraving the U-shaped grooves 4 in the circumferential direction of the surface layer build-up layer 3a at equal pitches, when the high temperature slab comes into contact with the roll, the grooves 4 form the surface layer of the roll. The thermal stress generated in 3 is relaxed.

Further, as shown in FIG. 1B, a spiral cooling hole 5 is provided on the surface of the roll body 2. Cooling water enters from the end of the roll shaft and forms a spiral shape on the roll body 2.
By flowing along the front surface, that is, the back surface of the surface layer portion 3, and discharging from the opposite end of the roll shaft, the cooling effect of the entire roll surface layer portion is enhanced.

FIG. 2 shows an example of the arrangement of the cooling holes 5 and the surface layer portion 3 when forming the overlay layer 3a. In FIG. 2 (a), the sealing plate 3b is spirally spread in advance around the cooling holes 5. FIG. 3B shows an example of preventing the molten metal from flowing into the cooling hole 5 by forming a built-up layer 3a from above, and FIG. 3B shows a sleeve 3c fitted on the roll body 2 first. However, an example of forming the overlay layer 3a from above is shown.

As described above, the spiral cooling hole 5 enhances the cooling effect of the entire roll surface layer portion 3, and the U-shaped groove 4 engraved in the circumferential direction further causes thermal stress applied to the roll surface to the groove. The irregularities are absorbed and dispersed, and the thermal stress applied to each part of the roll surface is reduced. In this way, the frequency of the site where thermal stress exceeding the critical stress for crack generation occurs is reduced, crack generation and wear on the roll surface are reduced, and the roll life is greatly extended.

[0023]

[Example] In order to select a groove shape that relaxes the thermal stress on the surface of the continuous casting roll, various tests were performed on the surface of the test roll, and tests for crack resistance and the like were performed. The test conditions, test methods, test results, etc. will be described below.

An outline of the test apparatus is shown in FIG. In the figure, the test roll 11 and the pressure-reducing roll 12 are laterally opposed to each other to apply the pressure reduction, and the high-frequency heating device 13 heats the test roll 11 from above, and the test water 11 is cooled by the cooling water spray device 14 below. . Reference numeral 15 is a thermoviewer.

[0025]

[Table 1]

In the test procedure, the high-frequency heating device 13 and the cooling water sprinkling device 14 are used to adjust the inlet and outlet temperatures of the test roll 11 (the material to be heated) so that the temperature reaches a predetermined condition value, and the rolls are continuously connected. Operate and observe the occurrence and progress of cracks due to thermal strain. The test evaluation items are observed and measured every 500 times of the number of tests. The materials used for the test (build-up material) and the test results are shown in Tables 2 and 3,
It is shown in FIG. In Tables 3 and 4, a roll having a U-shaped groove with a pitch of 10 mm and a width of 5 mm engraved in the circumferential direction is the embodiment of the present invention, and the other rolls are the comparison rolls.

[0027]

[Table 2]

The test results are shown in Tables 3 and 4 below. Table 3,
4, a comparative example using a flat roll as it is, a comparative example in which a cross U-shaped groove is engraved,
Is a comparative example with micro-patterning on the roll surface,
Are examples of the present invention in which U-shaped grooves are engraved in the circumferential direction.

From these results, without processing (flat roll), two cracks of about 50 mm were formed in the circumferential direction after 2000 rotations, and these cracks are considered to be cracks due to thermal fatigue of the surface layer portion.

In machining (coarse U-groove roll),
No crack was generated even at 7,000 rotations.

In machining (roll of medium U-groove), about 50 cracks of about 1 mm, which are considered to be caused by thermal fatigue, are formed at the bottom of the U-groove at 7,000 rotations, but it is considered that the crack suppressing effect is the greatest. To be

In machining (roll with a fine U-shaped groove), about 50 cracks of about 1 mm, which are considered to be caused by thermal fatigue, are formed at the bottom of the U-shaped groove at 3000 revolutions. Cracking is rapid and the effect of groove depth on thermal fatigue is poor.

In MP-1 (micropatterning on the roll surface), about 20 rotations in the circumferential direction have already been reached after 1000 rotations.
It is considered that two 0 mm cracks are generated, and this is because the micropatterning depth is as shallow as 50 μm, so that the crack generation is promoted rather than the crack suppression.

In machining (5 mm wide U-shaped groove with a circumferential pitch of 10 mm), 700-
No cracks occurred even at 0 rotation. Approximately 1 m due to thermal fatigue in the axial direction at the surface layer of the convex roll at 3000 rotations
About 20 cracks of m occur.

In machining (5 mm width U-shaped groove with a circumferential pitch of 15 mm), 650 was formed in the crack-determining concave portion.
One crack of about 100 mm is generated in the circumferential direction at 0 rotation. In addition, about 5 mm of cracks of about 1 mm are generated in the axial direction of the roll surface layer portion of the convex portion due to thermal fatigue at the time of 5500 rotations.

In machining (5 mm width U-shaped groove with 20 mm pitch in the circumferential direction), 6500 was formed in the concave portion that became the crack-controlling portion.
When rotating, one crack of about 100 mm is generated in the circumferential direction, but it has a great effect of suppressing cracking as compared with the above flat roll.

According to the above test results, the roll of the embodiment of the present invention in which a U-shaped groove having a width of 5 mm and a pitch of 10 mm is engraved in the circumferential direction does not generate cracks even at 7,000 rotations and has an effect of suppressing crack resistance. It is excellent and easy to process compared to a roll in which grooves are engraved in the cross direction of the roll or micro patterning.

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

As described above, in the continuous casting roll of the present invention, U-shaped grooves are engraved in the circumferential direction, and the groove depth, groove pitch, and groove projection width are limited. As a result, cracking and wear on the roll surface are reduced, and roll life is significantly extended. Also, machining is easier than rolls with grooves in the cross direction or micro patterning, and machining time is shortened. Therefore, the manufacturing cost can be reduced.

By providing spiral cooling holes on the surface of the roll body, the cooling effect of the entire surface layer of the roll is strengthened, and the thermal stress applied to each part of the roll surface is reduced. Cracking and wear are reduced and roll life is significantly extended.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a continuous casting roll according to the present invention, in which (a) is a perspective view of the outer shape of the roll, (b) is a roll sectional view showing details of cooling holes, and (c) is It is a detailed sectional view of a U-shaped groove.

2A and 2B show an example of how the cooling holes and the surface layer portion are fitted together when forming the overlay layer. FIG. 2A is a sectional view when a seal plate is used and FIG. 2B is a sectional view when a sleeve is used.

FIG. 3 is a schematic side view showing the outline of a roll test apparatus.

[Explanation of Codes] 1 roll for continuous casting 2 roll body part 3 surface layer part 3a overlay layer 3b seal plate 3c sleeve 4 U-shaped groove 5 cooling hole 11 test roll 12 pressing roll 13 high frequency heating device 14 cooling water spraying device 15 Thermo viewer

[Procedure amendment]

[Submission date] June 7, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

[Fig. 2]

Claims (2)

[Claims] 1. A surface layer of a roll is coated with a build-up layer of a material having heat resistance, abrasion resistance and corrosion resistance, and a U-shaped groove having a constant depth is circumferentially formed on the surface layer coated. A continuous casting roll characterized by being engraved at regular intervals and further having spiral cooling holes on the surface of the roll body. 2. The values of the groove depth (D), the groove pitch (p), and the groove convex width (h) of the U-shaped groove formed on the surface layer of the roll are 5 ≦ D ≦ 10 (mm). ), 10 ≦ p ≦ 20
The continuous casting roll according to claim 1, wherein (mm) and p / 4≤h≤3p / 4 (mm).