JPS6257751A - Roll for transfer of hot metallic billet - Google Patents

Abstract

PURPOSE:To prohibit the growth of cracks running in the circumferential direction of a roll and to improve the life of the roll by forming notches along the longitudinal direction of the roll on the roll surface. CONSTITUTION:The many notches 2 are provided to the roll body 1 in parallel with the axial direction thereof. The many cracks 3, 3... are generated on the surface of the roll body 1 upon use and these cracks are going to grow toward the inside of the roll body 1. However, the thermal cracks 4 arising from the thermal stress in the initial stage of using the roll are generated in the bottoms of the notches 2 so as to grow in the longitudinal direction of the notches as there are the notches 2 inscribed along the axial direction of the roll. These thermal cracks 4 do now grow any more after the cracks attain certain depth. On the other hand, the cracks in the circumferential direction arising from the bending stress generated by the roll load collide against the thermal cracks 4 and do not grow any more.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a roll for transferring hot metal pieces, such as a roll for continuous casting, which is used for transferring or rolling hot metal pieces. It is.

<Prior art and its problems> This type of roll has repeated intermittent contact with high-temperature metal pieces, which causes thermal stress caused by heating and cooling, as well as bending stress due to the roll load. Many cracks occur on the surface.

The above thermal stress occurs in all directions on the roll surface, but it has almost no effect beyond a certain depth, and it is the bending stress that causes cracks to grow beyond that depth. Since the bending stress acts in the axial direction of the roll, it causes cracks to grow in the circumferential direction. When cracks that grow in the circumferential direction reach a certain depth, there is often a risk of breakage of the roll, so they are replaced in advance.

However, replacing the rolls will reduce the operating rate of the equipment and increase roll costs. For this reason, various efforts have been made to prevent cracks from occurring and growing in the circumferential direction of the roll. Specifically, the rolls were made of a material with excellent crack resistance, the thermal stress was reduced by internal or external cooling of the rolls, and the depth of the thermal stress reaching inside the rolls was made shallow. However, these efforts
Although the timing of crack initiation and propagation is somewhat delayed, it is still difficult to avoid the occurrence of cracks due to thermal shock.
Once a crack occurs, it gradually increases in size, and therefore improvements are desired.

<Means for solving the problems> The present invention provides a roll for transferring hot metal pieces as described above,
Based on the recognition that the occurrence and growth of cracks is inevitable, this technology aims to significantly extend the service life of rolls by preventing cracks from growing large in the circumferential direction, which could lead to roll breakage. The gist of the present invention is a roll for transferring hot metal pieces, which is characterized by having a large number of notches along the longitudinal direction of the roll on the surface of the circumferential body of the roll that comes into direct contact with the hot metal pieces.

<Examples and Effects> The roll of the present invention will be described in detail below with reference to the drawings showing examples of the present invention.

FIG. 1 shows a roll in which a large number of notches (2) are provided in parallel to the axial direction of the roll body (1), and FIG. 2 shows a sectional view thereof. There is no need to place any restrictions on the shape or size of the notch (2) as long as it has a shape that produces a so-called notch effect and causes stress concentration there.

In the roll of the present invention as shown in FIGS. 1 and 2, as the roll is used, many cracks (3) occur on the surface of the roll body (1) due to the factors mentioned above.

(3), is generated and tries to grow toward the inside of the roll body (1). However, since there are notches cut along the axial direction of the roll, thermal cracks (4) due to thermal stress occur at the bottom of each notch (2) in the initial stage of use of the roll. It occurs along the direction.

In other words, thermal stress acts both in the axial direction and in the circumferential direction, but since there is a notch, cracks (4) occur preferentially there.

Once the thermal crack (4) generated at the bottom of the notch (2) reaches a certain depth, it will not grow any deeper because the influence of thermal stress will almost disappear.

On the other hand, cracks in the circumferential direction caused by bending stress due to roll load occur on the roll surface (between the notches) where the stress is maximum, and as shown in Figure 1, many cracks (3) are independent and cracks. It occurs randomly and tries to grow inside the roll, but when it progresses to a certain depth, it hits the notch (2) or the thermal crack (4) that has occurred at the bottom of the notch, and its direction is at a right angle or at an angle close to a right angle. (below 45 degrees), so it will not grow any larger. Therefore, the depth of the notch is small, or the notch effect is small so that the initial circumferential crack (3) does not grow across the notch or the thermal crack (4) at the bottom of the notch. Now, you should set the notch effect.

Due to this mechanism, even if many cracks (3) occur in the circumferential direction, each crack is prevented from growing to a certain depth and is divided, so that it will not become a large rack that could damage the roll. be.

Note that the notch (2) provided in the roll body (1) may be formed by carving or pressing, but the key is to form the notch (2).
) part has a so-called notch effect, causing stress concentration. (Therefore, the width should not be too wide, but the shape should be one with a pointed bottom or a cross section as shown in Figure 2.) It may have a circular shape, a square shape, etc. Also, the roll body (1
Regarding the notch (2) provided in ), another problem is that if the area occupied by the notch (2) is too large, the surface pressure applied to the roll surface will become large, causing deformation of the notch opening edge or straining the roll itself. Therefore, the proportion of the area occupied by the notch (2) on the roll surface should be about 10% at most.

What is shown in Figure 3 is the roll body (1) and the notch on the surface (2).
is not continuous (, it is provided separately for each certain length)
An example of this form is shown below.

FIG. 4 shows another embodiment of the roll of the present invention,
The cutout (2) is not parallel to (or inclined to) the axis of the roll.

The same (Figure 5 shows a notch that is also inclined to the axis (
2) shows the rolls arranged so that they intersect.

In the rolls shown in FIGS. 4 and 5, the high-temperature metal piece, which is the object to be transferred or the object to be rolled, comes into contact with the recesses formed by the notches (2) one after another, rather than all at once. There is an effect that transfer or ζ rolling can be carried out in a staggered manner. However, the notch (2) is a crack in the circumferential direction (4) that occurs preferentially at the notch (2) or its bottom and remains at a certain depth.
In order to prevent the large growth of 3), it is preferable that the direction be the longitudinal direction of the roll, so the angle between it and the roll axis should be at most 45 degrees.

<Effects of the Invention> As described above, according to the present invention, by forming a notch on the roll surface along the longitudinal direction of the roll, the notch can be easily formed without weakening the strength of the roll itself against bending stress. By making use of the property that thermal cracks are generated preferentially at the bottom and remain within a certain depth, the growth of cracks running in the circumferential direction can be prevented, and as a result, the roll life can be greatly improved. It is possible.

[Brief explanation of drawings]

Figure 1 is a front view of the roll for transferring hot metal pieces of the present invention, Figure 2 is a front view of the roll for transferring hot metal pieces of the present invention;
The figures are cross-sectional views taken along line II-II in Figure 1, and Figures 3 to 5.
The figures are full-length diagrams showing other embodiments of the roll of the present invention. In the figure: (1) Roll body (2) Notch (3) Crack in circumferential direction (4) Heat crack in axial direction Patent applicant: Kuroki Kogyo Co., Ltd. Representative: Noriharu Ariyoshi

Claims (1)

[Scope of Claims] 1. A roll for transferring hot metal pieces, characterized in that the roll that comes into direct contact with high-temperature metal pieces is provided with a large number of notches along the longitudinal direction of the roll on the surface of its circumferential body. 2. The roll for transferring hot metal pieces according to claim 1, wherein the direction of the notch and the roll axis form an angle of 45 degrees or less.