JPS6133747A - Roll for continuous casting machine - Google Patents

Abstract

PURPOSE:To relieve thermal stress and to extend the life of a roll by engraving spiral grooves to the roll surface, fixing bellows having many nozzle holes to the inside of the grooves to close the grooves and providing a water feed hole and discharge hole communicating with the hermetic water passages of the roll to both ends of the grooves in the axial direction of the roll. CONSTITUTION:The roll 1 is made into the construction in which the spiral grooves 5 are provided to the roll surface and in which the water feed hole 6 and discharge hole 6a communicating with the cooling water hole 4 at the roll center are provided to both ends of the grooves. The bellows 8 having the many nozzle holes 7 are welded to the grooves 5 to close the open parts of the grooves 5, thereby constituting the hermetic passages to the roll surface. The bellows 8 are made freely expandable and shrinkable to absorb the thermal expansion of the roll 1 and are attached in the position lower than the roll 1 surface to prevent the contact with a billet. The bellows 8 are made of a stainless steel in consideration for corrosion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a roll for a continuous casting machine used as a pinch roll or the like of a continuous casting machine.

[Conventional technology]

The pinch rolls of continuous casting machines are used to apply pulling force to continuously cast slabs by rotating very slowly, and because the rotation speed is slow,
Even if cooling water is supplied inside the roll, the contact surface with the continuously cast slab reaches a very high temperature, and due to these high thermal loads and high a-weights, cracks occur on the surface of the roll □, and as these cracks develop, the roll may break. Problems were occurring frequently. This roll breakage not only causes the continuous casting machine to stop operating, but also requires a large cost for replacing the rolls.

Conventionally, the type of pinch roll in which a cooling water hole 4 is provided in the center of the roll, as shown in FIG. 2, has been mainly used.

In rolls using this type of cooling system, the temperature on the roll surface reaches as high as 500 to 600°C, and the temperature near the cooling water holes is about 1
Since a large temperature gradient occurs between the roll and the roll, the amount of stress fluctuation that occurs during roll rotation reaches 100 kg/mrrf or more. In addition, because the roll rotation is slow, the part where the platform surface contacts the slab reaches a high temperature almost equivalent to the slab temperature, which causes cracks to occur on the roll surface, the crack propagation speed is fast, and the life is short. There are some difficulties.

Therefore, we focused on the fact that about 90% of the roll surface stress is thermal stress, and adopted external cooling of the roll by water sprinkling to reduce the roll surface stress by reducing the temperature gradient within the cross section of the roll. It is being done.

However, as shown in Fig. 3, since there is a roll frame 3 near the roll 1, it is often impossible to provide external water cooling to the contact area between the roll 1 and the slab 2; leading to heat load.

As an attempt to solve such problems,
50637 has a technology that uses a sleeve-type roll outer peripheral surface that undergoes repeated thermal cycles, and that grooves are carved in the circumferential direction on the outer surface to release local thermal stress, and that durability is improved by selecting the material. Disclosed. Since this technology relies on external cooling, there is a limit to the relaxation of thermal stress, and =
Not applicable to integral rolls.

As another solution, Japanese Utility Model Publication No. 52-56346 discloses a water-cooled roll in which cooling grooves are provided on the back surface of the sleeve. This roll cools the inner wall of the sleeve, reducing thermal stress, but since continuous casting rolls are used at extremely low rotation speeds (for example, 1 revolution/min), the temperature difference between the outer and inner surfaces of the sleeve is greater than that of the slab. is still large at the contact position, and the local heat load is extremely large.

[Problem that the invention seeks to solve]

In view of the above circumstances, the present invention does not reduce the roll surface temperature using an external water cooling nozzle, but rather guides cooling water from within the roll to the roll surface to alleviate thermal stress in a wooden manner.
The object is to provide a roll that can achieve a long life.

[Means for solving problems]

The stress generated by the roll is dominated by thermal stress, and the stress value is determined by the temperature gradient of the cross section of the roll.

In the present invention, a spiral groove is carved on the circumference of the roll surface, and a bellows having a large number of nozzle holes is fixed in the groove to close the open part of the groove. This roll for a continuous casting machine is characterized in that a water supply hole for introducing cooling water and a drainage hole communicating with the closed channel are respectively provided in the roll. The roll of the present invention is characterized in that by adopting a cooling method in which cooling channels made of such spiral grooves are formed on the roll surface, the temperature gradient in the cross section of the roll is decisively reduced and the generated stress is alleviated. This is a roll for continuous casting machines.

The structure of the roll of the present invention is shown in FIGS. 1(a) to (C).

FIG. 1(a) is a front view of an embodiment of the present invention, and FIG. 1(b) is a front view of an embodiment of the present invention.
) is a detailed view of part A in the figure, and (C) is a partial vertical cross-sectional view of the figure (a). A spiral groove 5 is provided on the surface of the roll l, and
The structure has a cooling water supply hole 6 and a drainage hole 6a, which communicate with the cooling water hole 4 at the center of the roll, at both ends thereof.

A bellows 8 having a large number of nozzle holes 7 is attached to the spiral groove 5 as shown in FIG. 1(b).

The bellows 8 is attached by welding to the spiral groove 5. The bellows 8 closes the open part of the spiral groove 5, and the closed groove 5 is connected to the water supply hole 6 and the drain hole 6a as described above. shall be.

The bellows 8 can be easily attached by providing a stepped portion on the side wall of the spiral groove 5.

In the above example, the roll is a two-body roll, but the present invention is not limited to this, and may be a so-called sleeve type roll assembled by shrink-fitting a sleeve to the roll base. In this case, the above-mentioned spiral groove may be provided in the sleeve.

[Effect]

The roll of the present invention is provided with a spiral groove on the roll surface and has bellows 8.
The opening is closed, and the bellows 8 is provided with a nozzle hole.
Since the roll surface is directly cooled with cooling water by the water flowing through the spiral grooves and the water discharged from the nozzle, cooling can be ensured and thermal stress caused by the temperature difference between the roll surface and the inside of the roll can be minimized.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1(a) to (C). A spiral groove 5 is provided on the surface of the roll 1, and a bellows 8 is attached to the spiral groove 5 to form a closed channel on the surface of the roll.

The bellows 8 is expandable and contractible to absorb thermal expansion of the roll 1. Further, the bellows 8 is structured to have a plurality of nozzle holes 7 in order to jet cooling water onto the roll surface. The cooling water 9 flows from the cooling water hole 4 at the center of the roll through the water supply hole 6 to the water channel of the spiral groove 5, and the return water flows into the cooling water hole 4 again from the drainage hole 6a.

Further, the mounting position of the bellows 8 is set slightly lower than the surface of the roll 1 to prevent contact with the slab 2.

Furthermore, the material of the bellows 8 is preferably stainless steel or the like in consideration of corrosion resistance.

〔Effect of the invention〕

By employing this embodiment, it is possible to reduce the surface temperature of the roll 1 to 200'0 or less without installing an external water cooling nozzle. As a result, as shown in FIG. 6, the amount of surface stress fluctuation is approximately the same for a 700 mmφ roll as compared to a conventional roll without external water cooling, and the life is 2 to 3 times longer.

Therefore, it is possible to reduce the roll replacement cost, which has been a problem in the past, and to achieve stable operation of the continuous casting machine. Furthermore, since the grooves constituting the cooling channels on the surface are spiral grooves, the contact area with the slab does not change significantly, and there is no change in the function as a pinch roll.

[Brief explanation of the drawing]

FIG. 1(a) is a front view of an embodiment of the present invention, and FIG. 1(b) is a front view of an embodiment of the present invention.
) Detailed view of part A in the figure, (C) is a partial vertical sectional view of the figure (a),
Figure 2 is a front view of a conventional roll. Figure 3 is (a) a front view and (b) side view of a pinch roll stand. Figure 4 is the relationship between the depth from the roll surface and the roll surface stress variation. This is a graph showing. 1... Roll 2... Slab 3... Roll frame 4... Cooling water hole 5... Groove
6...Water supply hole 6a...Drain hole

Claims (1)

[Claims] 1 A spiral groove is carved on the circumference of the roll surface, a bellows having a large number of nozzle holes is fixed in the groove to close the open part of the groove, and the closed channel and the closed channel are formed at both ends of the roll in the axial direction. A roll for a continuous casting machine, characterized in that a water supply hole and a drainage hole for communicating cooling water are provided.