EP1197721B1 - Cooled furnace roller, in particular for a roller hearth furnace - Google Patents

Abstract

A furnace roller for transporting of a continuously cast stock of a continuously casting plant through a temperature equalizing and heating furnace and including a rotatable arbor supported outside of the furnace and having cooling medium channels provided in its interior, a plurality of tires supported on the arbor and forming a transporting plane for the transported stock, at least one clamping ring provided between a tire and the arbor and formed of metal or alloy having a maximum possible thermal conductivity and susceptible to both cold and hot deformation, and at least one steel sleeve provided sidewise of the clamping ring.

Description

The invention relates to a coolable oven roll for transporting continuous casting material a continuous casting plant by means of a heatable temperature compensation / reheating furnace, comprising a rotationally drivable, mounted outside the furnace Shaft, in particular with internal coolant channels, and with on arranged the shaft by means of a receiving bore forming a conveyor plane Carrying rings for the cargo.

In roller hearth furnaces of continuous casting plants, for example, thin slabs are formed Rolling temperature preheated. The promotion of rolling stock or slabs through the roller hearth furnaces is done by oven rolls in different designs. The roller hearth furnace is usually in line between casting machine and rolling mill and is characterized by its function as a heating, balancing and and buffer zone. Due to the types of load of furnace rolls during the kiln operation showed the existing in the prior art types of furnaces different lengths of life on.

The physical dimensions of such a furnace and its facilities for heat application, eg. Burner, are designed so that the furnace exit the Thin slabs have the required rolling temperature. It is a uniform Temperature distribution in the slab over its length, width and height at the kiln outlet unconditional requirement for subsequent rolling. The Oven length allows the inclusion of several thin slabs, which after casting - With different casting speeds - separated from the cast strand become.

The transport of such thin slabs takes place within the furnace via driven Furnace rollers. These are at a certain kiln height at a level the transport height, arranged at predetermined distances from each other. The dimensions the roles are - relatively speaking - characterized in that the Diameter of the support rings and the shafts small compared to the length of the rollers is.

The transport rollers in the roller hearth furnace can be equipped with a water cooling system be arranged or as a so-called. Dry rolls without cooling device be.

The usual construction of a water-cooled roll comprises a plurality of support rings in axial distance on the water-cooled shaft. The latter is between the Tragringen insulated with refractory material, this insulating layer almost as well Thick is how the outer diameter of the support rings.

The shaft is stored outside the furnace and there with connections for the internal shaft cooling Mistake. This internal cooling is achieved by a pipe with circular cross section, which is arranged concentrically in the shaft. Through this flows in cooling water, the tube passes through to the opposite side of the Furnace and flows on the other side into the annular gap between tube and shaft, flows through this and finally leaves the shaft on the inflow side. in the Annular gap between shaft and inserted pipe can become internals in the farthest Are located, which serve to fix the tube in the radial position and to increase the flow velocity of the water in the annular gap.

The applied to the roller axle support rings are usually made Casting material and are made of high temperature nickel or cobalt base alloys produced. The shaft is preferably made of heat-resistant steels.

The water cooled rolls are given priority, but not exclusively in the Heating zone used a roller hearth furnace. They are alternating in the transport direction equipped with a different number of support rings. Usually The waves are equipped with four or five support rings, usually alternately. The support rings are in the transport direction of a roll with four Carrier rings to the role with five carrier rings arranged on different lines. For the role with four support rings applies that in each case two support rings on a shaft half whereas on the reel with five support rings one in the middle of the reel, the others relative to those on the roll with four support rings outwards are arranged.

In the prior art, the support rings on the shaft usually by welds secured against axial displacement. The torque can be over known Shaft-hub connections, such as Feather keys or also over welds be transmitted.

Due to the thermal expansion of the support ring material during heating and during operation loosens the seat of the support rings on the shaft. By bending stress the furnace roll and the intended higher heat dissipation from the Carrier ring surface to the cooling water of the shaft inside result mainly in the heating phase, thermal stresses in the welds, which increase with time their destruction and unusability of the furnace roller can lead.

A major reason for the failure of a furnace roller is the damage or destruction of the roller insulation, because just because the welds the high oven temperatures are directly exposed.

Contact between the support ring and the water-cooled shaft absorbs heat from the Support ring surface dissipated and thereby the surface temperature of the Support rings significantly reduced. The more heat is dissipated, the cooler it gets Support ring surface. The cooler the support ring surface, the lower the inclination to growths of tinder.

During the production, for example, of thin slabs, hot steel comes with oxygen the atmosphere in contact. As a result, the steel surface is under formation oxidized by scale. Such scale formation basically occurs everywhere where oxygen in the surrounding gas medium reacts with a Steel surface is available.

During the transport of a thin slab through the furnace, tinder falls off the Slab surface and is by Zunderklappen in the lower part of the roller hearth furnace away. On the other hand, but also in contact between thin slab and oven roll in the roller hearth furnace, tinder stick to the support ring surface and there form growths, which einruükken in the thin slab bottom and depending on the depth on the rolled hot strip as a surface defect appear. Such errors then lead to the committee and thus set serious quality problem for plant operators.

The document EP 0 633 815 B1 describes a furnace roll for supporting a heated workpiece, which has a rotatable inner shaft for receiving a coolant having a number of axially spaced support rings are attached to this. A thermally resistant insulating agent that um the shaft is mounted, extends axially between the support rings, wherein the insulating means has an outer surface extending radially over at least a considerable part of the radius of a support ring pair extends. The insulating agent is secured in the shaft by anchoring means, with protruding Ends radially inward from the outer surface of the insulating means are arranged. The spacer is made of a metal which for the castable insulating a voltage drop in the thermal expansion the anchoring means and deflection of the furnace roller allows.

The document DE 38 07 240 C1 describes a roller hearth furnace for heating of slabs, blocks, billets, sheets and the like warm goods, whose Furnace space is formed with a longitudinally extending roller table. The oven has a hot upper oven room, and a lower oven room, and in between a stove floor with recesses. The roller table is essentially in the sub-furnace space stored below the hearth floor and protrudes only with small sections its furnace rolls through the recesses of the hearth floors above its level. At least the roller sections projecting into the hot zone with their running surfaces, on which the warm goods are transported, are made of particularly heat-resistant Material which, composed of segments into a ring, the Cover the furnace rollers on the peripheral surface. Release cleaning devices the running surfaces of the oven rolls of troublesome scale caking.

EP-A-1 189 004 proposes to improve the Heat transfer between support rings and shaft, in particular the heat dissipation from the support rings to increase the shaft and thus the availability To extend the support rings with reduced growth of scale and at the same time to ensure a safe torque transmission, as well as at reduced Workload greater flexibility in applying the support rings on the shaft, before, that the shaft at least at the receiving areas the support rings outer seats to form a polygonal Has cross-section, and that each support ring with polygonal positively locking inner mating surfaces is formed.

Based on the aforementioned prior art, the invention has the object basis, means for further improving the heat transfer between Specify support rings and shaft, thereby removing the heat from the Wear rings to increase the shaft significantly and the availability of the support rings to extend with reduced growth of scale and at the same time a reliable, safe torque transmission between support rings and shaft too ensure and with reduced workload when applying the Wear rings on the shaft to achieve greater flexibility in their arrangement.

To solve the problem is in a coolable oven roll in the preamble of Claim 1 specified type provided with the invention that for the production an optimal metallic contact for an unhindered heat transfer between the support ring and shaft at least one clamping ring made of metal or of a metal alloy having both the highest possible thermal conductivity, as also suitable for cold and hot deformation, and by thermal Longitudinal extent of steel bushes sliding over the shafts when cold under pressure plastically to the perfect investment of the associated Surface parts deformed and with the shaft torsionally stable and torque transmitting is connected.

The inventive construction of shaft and support ring with intermediate layer a clamping ring of a good thermal conductivity as well as deformable Metal or a metal alloy becomes an optimal metallic contact between created the mutually associated surfaces of support ring and shaft, which creates the highest possible heat transfer and at the same time a quality of connection between the support ring and shaft results, which with that of a Shrink fit is comparable and results in a maximum of torsional stability.

An embodiment of the measure according to the invention provides that the clamping rings consist of a copper-wrought alloy according to DIN 17 666.

However, in addition to copper, they can also be made of a high thermal conductivity and comparatively soft copper / silver alloy.

A further embodiment of the invention provides that a support ring with an opposite his rim thickened hub is formed, which on both sides annular Has recesses for receiving a pair of clamping rings. In order to the contact area between the support ring and shaft is further increased and thus the heat flow from the support ring in the shaft further improved and at the same time the torque transmission continues to be strengthened.

An even further improvement in heat transfer and in the Torque transmission can be achieved in that the hub with a axially continuous receiving bore provided with a fit, e.g. a snug fit, is designed for a one-piece insertable clamping ring.

Figur 1

im Schnitt einer mit der Mittelachse der Welle zusammenfallende Schnittebene ein Endteil einer kühlbaren Ofenrolle umfassend eine Welle mit innen liegenden Kühlmittelkanälen und einem außen zwischen Stahlbuchsen angeordneten, mit eingelegten Klemmringen versehen Tragring;

Figur 2

eine Ausführung eines Teils der Ofenrolle mit einem durch Anordnung einer Nabe im Bereich der Aufnahmebohrung verbreiterten Sitz eines Tragringes mit axial durchgehender Aufnahmebohrung und einem einstückig eingesetzten Klemmring, ebenfalls im Schnitt einer axialen Schnittebene;

Figur 3

einen Tragring mit verbreiterter Nabe und beiderseits ringförmigen Ausnehmungen zur Aufnahme eines Paares von Klemmringen, ebenfalls im Axialschnitt.

Further embodiments of the invention are provided according to the subclaims. Details, features and advantages of the invention will become apparent from the following explanation of some schematically illustrated in the drawings embodiments. Show it:

FIG. 1

in the section of a cutting plane coinciding with the central axis of the shaft, an end portion of a coolable furnace roller comprising a shaft with internal coolant channels and a support ring arranged externally between steel bushes and provided with inserted clamping rings;

FIG. 2

an embodiment of a part of the furnace roller with a widened by arranging a hub in the region of the receiving bore seat of a support ring with axially continuous receiving bore and a clamping ring used in one piece, also in section of an axial sectional plane;

FIG. 3

a support ring with widened hub and both sides annular recesses for receiving a pair of clamping rings, also in axial section.

The illustrated in Fig. 1 end portion of a coolable oven roll 1 for the transport of Continuous casting material of a continuous casting plant by means of a heatable temperature compensation / reheating furnace, comprises a rotationally drivable, outside the Furnace mounted shaft 3 with internal coolant channels 4, 5. On the shaft 3 and lying outside are by means of a receiving bore 6 a conveying plane x-x forming support rings 7 arranged for transport. The support ring 7 has the Form of a circular disc and is in a preferred embodiment on his peripheral transport surface equipped with a carbide armor 12. Of the Support ring is pushed with a fitting hole 6 on the shaft 3 and takes in circular recesses 11, 11 'clamping rings 8, 8' on. These consist of Copper or of a metal alloy having both the highest possible thermal conductivity, as well as suitability for cold and hot deformation. Next to this side Clamping rings are pushed onto the shaft 3 steel bushings 9, 9 'and first in the cold state with comparatively low axial pressure through a terminal Clamping nut 13 brought against the clamping rings 8 for positive engagement.

If then under the influence of strong heating, for example. By some 100 ° C, the bushings 9, 9 'experience a thermal elongation, they practice against the clamping rings 8, 8 'an extremely high axial pressure, under the influence of the clamping rings 8 elastically deformed and for perfect metallic contact with the associated surface parts of clamping ring 8 and shaft 3 are brought. In order to Both the heat conduction between these components of the furnace roller 1 to the utmost intensified, as well as the torque transmission improved.

Figure 2 shows an embodiment of the article of the invention, wherein the Support ring 7 is formed with a relation to its rim 7 'thickened hub 10. This can either, as shown in Fig. 3, both sides annular Have recesses 11, 11 'for receiving a pair of clamping rings 8, 8', but it can also be provided with an axially continuous receiving bore 6 ' be with a fit, e.g. a snug fit, for a one-piece use Clamping ring 8 'may be formed.

In a further embodiment and improvement of the furnace roller 1 can to prevent the formation of a heat transfer hindering oxide layer to each other in contact metal surfaces of the clamping rings 8 and the receiving bore 6, this with an electroplated noble metal layer, or coated with nickel.

As already mentioned, the steel tube pieces which can be pushed on the shaft 3 at the end are the sleeve 9 as shown in Fig. 1 with the shaft end 3 'axially adjustably held by the screw 13.

reference numeral

1

furnace roller

3

wave

4

Coolant channel

5

Coolant channel

6

Receiving bore / fitting bore

7

support ring

7 '

Rim of the support ring

8th

clamping ring

9

steel bushing

10

hub

11

recess

12

Hardfacing

13

Clamping nut / screw connection

Claims (8)

1. Coolable furnace roller (1) with the transport of continuously cast material of a continuous casting plant through a heatable temperature-balancing/heating-up furnace, comprising a shaft (3) drivable in rotation and mounted outside the furnace, particularly with internally disposed coolant channels (4, 5), and with support rings (7), which are arranged on the shaft by means of a receiving bore (6) and which form a conveying plane, for the material to be transported, characterised in that for producing an optimum metallic contact for a heat transfer, which is as unobstructed as possible, between support ring (7) and shaft (3) at least one clamping ring (8) of metal or of a metal alloy is used with not only a highest possible thermal conductivity, but also suitability for cold and hot deformation, and is deformed by thermal expansion in length of steel bushes (9, 9'), plastically under pressure for complete contact of the mutually associated surface parts and is connected with the shaft (3) in a manner stable in torsion and capable of transmitting torque.
2. Furnace roller according to claim 1, characterised in that the clamping rings (8, 8') consist of a wrought copper alloy according to DIN 17 666.
3. Furnace roller according to claim 1, characterised in that the clamping rings (8, 8') consist of copper, copper alloy or an alloy of similar reshaping strength or of a highly heat-conductive and comparatively soft copper/silver alloy.
4. Furnace roller according to one or more of claims 1 to 3, characterised in that a support ring (7) is constructed with a hub (10) which is thickened relative to its rim (7") and which has at both sides annular recesses (11, 11') for reception of a pair of clamping rings (8, 8').
5. Furnace roller according to one or more of claims 1 to 4, characterised in that the hub (10) is provided with an axially continuous receiving bore (6') which is constructed with a fit, for example a snug-fit, for a clamping ring (8') insertable in one piece.
6. Furnace roller according to one or more of claims 1 to 5, characterised in that for preventing creation of an oxide layer, which obstructs heat transfer, at the mutually contacting metal surfaces of the clamping rings (8) or the receiving bore (6) these are coated with a noble metal layer able to be applied by plating or with nickel.
7. Furnace roller according to one or more of claims 1 to 6, characterised in that the steel tube pieces, which can be pushed on end onto the shaft (3), of the bushes (9) are retained on the shaft end (3') by a screw connection (13) or clamping nut to be axially adjustable.
8. Furnace roller according to one or more of claims 1 to 7, characterised in that the support ring (7) is coated at its peripheral transport surface with a hard metal running layer (12).

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