JPH0452210A - Hearth roll for heat treatment - Google Patents

Abstract

PURPOSE:To efficiently lower temp. of the whole roll without using water for cooling by assembling a heat conductive bar having good heat conductivity to shaft center of a roll, exposing end parts to out of roll shaft ends and cooling with fins, etc. CONSTITUTION:In a hearth roll 2 for heat treatment of metal strip, etc., barrel part of this hearth roll 2 is made to hollow and the heat conductive bar 1 composed of the metal having good heat conductivity, passing through the shaft center of hearth roll and exposing to out of the shaft end, is arranged under non-contacting condition with inner wall in the barrel part, and heat radiated parts in the fins 10, etc., are arranged in the exposed part at out of the shaft end of this heat conductive bar 1. Further, as lowering of cooling effect at the time of stepping, is considered, injection of cooling air is desirable to execute with an air nozzle 7 for cooling.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a hearth roll for a heat treatment furnace suitable for use in a high-temperature atmosphere.

<Prior Art> The main problems that occur in hearth rolls used in high-temperature atmospheres are deformation such as bending and bearing damage.

Conventionally, to solve this problem, (1) use of high mit heat steel for the hearth roll body;
(2) water cooling of the roll shaft, (3) near the bearing including the bearing box (a) water cooling (jacket type), and (b) air cooling (finned case).

Furthermore, in Japanese Utility Model Application Publication No. 63-40601, a movable heat pipe is inserted into a hollow part extending in the axial direction of the hearth roll, and the roll temperature is adjusted by bringing one end of the heat pipe into contact with the inner wall of the roll at the location where heat is to be removed. In addition, Japanese Patent Laid-Open No. 62-7249 reports a technique in which a plurality of heat pipes are embedded in the roll surface layer to make the temperature of the roll surface uniform.

However, when heat-resistant steel is used for hearth rolls, its thermal conductivity is low (compared to ordinary steel, Ni-Cr steel is about l/l/
2), it is inevitable that the roll temperature will rise.

In addition, when water-cooling the vicinity of the roll shaft or bearings,
Ancillary equipment for cooling water supply and drainage is required (2)
There are problems such as there is a high risk of problems such as water clogging and water leakage, and (3) (+) and (2) related to (2), maintenance and management require a lot of cost and effort.

Furthermore, in the case of air cooling using fins, the cooling effect is indirect and small, and although it is effective in protecting the bearing, it is hardly effective against roll deformation and the like.

In addition, when using a heat pipe, the temperature range that the heat pipe can handle is a maximum of 200 to 300°C on the pipe surface. Therefore, it is difficult to say that it is practical in terms of reliability and safety of the equipment, and the installation of equipment involves a great deal of cost.Therefore, cooling methods using heat pipes require high-temperature operation where bending of the hearth rolls becomes a problem. This method is not suitable for furnaces.

<Problems to be Solved by the Invention> The purpose of the present invention is to reduce bending of hearth rolls and damage to roll bearings used in furnaces operating at high temperatures by a relatively simple means that does not rely on water cooling or heat pipes. An object of the present invention is to provide a hearth roll for a heat treatment furnace.

<Means for Solving the Problems> The present invention provides a hearth roll for a heat treatment furnace for metal strips, etc., by making the body of the hearth roll hollow so that the heat that passes through the center of the hearth roll and is exposed to the outside of the shaft end is prevented. A heat extraction rod made of a metal with good conductivity is provided without contacting the inner wall of the body, and a heat dissipation part such as a fin is provided on the exposed part outside the shaft end of the heat extraction rod. This is a hearth roll for heat treatment furnaces.

<Function> According to the present invention, a heat extraction rod made of a metal with good thermal conductivity is incorporated into the roll axis, and the end on the opposite high temperature side is exposed outside the roll axis end and cooled by fins, etc. Therefore, the temperature of the high temperature side and the entire roll can be efficiently lowered without using water for cooling.

In addition, since the parts used for cooling are a single unit, such as a metal rod with good thermal conductivity, the equipment is simple, the risk of trouble is low, and it can be used almost maintenance-free.

In addition, in the present invention, the heat extraction bar is incorporated in a non-contact state with the inner wall of the hearth roll body, so heat transfer from the roll to the heat extraction bar is mainly through radiation, resulting in uniform cooling of the roll body. becomes possible. Conversely, when the heat extraction rod is in contact with the inner wall of the roll body, the contact portion moves due to the difference in thermal expansion coefficient between the heat extraction rod and the roll, resulting in non-uniform contact state. As a result, differences in heat transfer occur, leading to roll bending. Therefore, the distance between the heat extraction rod and the inner wall of the roll must be such that they do not come into direct contact due to mutual expansion.

By the way, it is desirable that the inner surface of the roll body and the surface of the heat extraction rod be black-treated to increase the emissivity.

The material for the rod is Cu, ^Z, M, which has a high thermal conductivity α.
Select from among g, Ag, etc., taking into account the operating temperature and cost.

You can use one piece with both ends through, but you can use two pieces as shown in Figure 1.
Separation is more practical because the heat extraction rod has lower heat resistance than the roll body and deforms faster than the roll body. Furthermore, when deformation (bending) occurs due to the large cross-sectional area for heat transfer, there is strong interference at the insulating material at the end of the roll shaft. If it is divided into two parts, this interference will hardly be a problem. In addition, it is easier to replace if it is divided into two parts.

Next, the present invention will be explained in more detail with reference to Examples.

<Example> FIG. 1 is a schematic diagram showing an embodiment of the present invention.

The heat extraction rod 1 transfers heat from the high temperature section to the opposite high temperature section (cooling side) and lowers the temperature of the roll 2. The heat extraction rod 1 is held at the end of the roll 2 via a heat insulating material 9. 3 is a bearing, and 4 is a bearing box.

In this example, the heat extraction rod I is divided into left and right parts at the center of the roll. The cooling capacity is increased by attaching fins 10 to each cooling side. Since the roll normally rotates, cooling is automatically promoted by attaching fins, etc., but since the cooling effect may be reduced when the roll is stopped, it is desirable to blow cooling air through the cooling air nozzle 7.

<Effects of the Invention> Since the hearth roll of the present invention can efficiently lower the roll temperature without water cooling the inside of the roll shaft,
It is easy to maintain and manage without problems such as water clogging and water leakage that occur when using water. Therefore, it can be maintenance free.

Additionally, since no water is used, there is no need for additional supply and drainage equipment, making it possible to significantly reduce costs during facility construction.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. ...Heating rod, ···bearing, ・Furnace body insulation material, ...cooling air ...Insulation material. 2...roll, 4...Bearing box, 6...Furnace body shell, Zuru, 8...control valve,

Claims (1)

[Claims] In hearth rolls for heat treatment furnaces such as metal strips,
The body of the hearth roll is made hollow, and a heat extraction rod made of a metal with good thermal conductivity is provided through the axis of the hearth roll and exposed outside the shaft end without contacting the inner wall of the body, and A hearth roll for a heat treatment furnace, characterized in that a heat dissipation part such as a fin is provided on an exposed part outside the shaft end of the heat extraction rod.