EP1189004B1 - Water cooled furnace roller - Google Patents

Abstract

Water-cooled furnace roll comprises a shaft (3) which rotates outside of the furnace with cooling channels (4, 5); and supporting rings (7) arranged on the shaft using a bore (1) and forming a conveying plane. The contact surfaces on the inner diameter of the bore of the ring and/or on the outer diameter of the shaft are in the form of a polygonal profile with fitting surfaces (6, 6') of an approximate constant diameter as weak thickness. Preferred Features: The deviation of the fitting surfaces from the ideal circle is 4-5%. The supporting rings is made of one or more individual rings.

Description

The invention relates to a water-coolable oven roll for conveying cargo, eg. Continuous casting of a continuous casting, by a roller hearth warming furnace, comprising a rotatable, outside the furnace mounted shaft, in particular with internal coolant channels, and arranged on the shaft by means of a receiving bore , a conveying plane forming carrier rings for the cargo.

In roller hearth furnaces of continuous casting plants, for example, thin slabs are preheated to rolling temperature. The promotion of the rolling stock or slabs by roller hearth furnaces is done by furnace rollers in different versions. The roller hearth furnace is usually in line between the casting machine and rolling train and is characterized by its function as a heating, compensation and buffer zone. Due to the types of loading of furnace rolls during furnace operation, the existing in the prior art types of furnaces have different lengths of life.

The spatial dimensions of such a furnace and its heat-applying devices, for example, burners, are designed such that the furnace outlet Thin slabs have the required rolling temperature. In this case, a uniform temperature distribution in the slab over its length, width and height at the exit of the kiln unconditional condition for subsequent rolling. The oven length allows the inclusion of several thin slabs, which are separated after casting - with different casting speeds - from the cast strand.

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

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

The usual construction of a water-cooled roller comprises a plurality of support rings at an axial distance on the water-cooled shaft. The latter is insulated between the support rings with refractory material, this insulating layer is almost as thick as the outer diameter of the support rings.

The shaft is stored outside the furnace and provided there with connections for internal shaft cooling. This internal cooling is achieved by a tube with a circular cross section, which is arranged concentrically in the shaft. Through this cooling water flows, the tube passes through to the opposite side of the furnace and flows on the other side into the annular gap between the tube and shaft, flows through it and finally leaves the shaft on the inflow side. In the annular gap between the shaft and the inserted pipe, internals can be widely used 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 support rings applied to the roller axle are usually made of cast material and are made of high temperature nickel or cobalt base alloys. The shaft is preferably made of heat-resistant steels.

The water-cooled rolls are used primarily but not exclusively in the heating zone of a roller hearth furnace. They are equipped in the transport direction alternately with a different number of support rings. Usually, the waves are equipped with four or five support rings, usually alternately. The support rings are arranged in the transport direction of a role with four support rings to the role with five support rings on different lines. For the role with four support rings is that in each case two support rings are located on a shaft half, whereas on the role with five support rings one in the middle of the roll, the others are arranged offset relative to those on the role with four support rings outwards.

In the prior art, the support rings on the shaft are usually secured by welds against axial displacement. The torque can be achieved via known shaft-hub connections, such as e.g. Passing feathers or be transmitted via welds.

Due to the thermal expansion of the support ring material during heating and during operation, the seat of the support rings loosens on the shaft. By bending stress of the furnace roller and the intended higher heat dissipation from the support ring surface to the cooling water inside the shaft result, especially in the heating phase thermal stresses in the welds that can lead over time to their destruction and uselessness of the furnace role.

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

Contact between the support ring and the water-cooled shaft dissipates heat from the support ring surface, significantly reducing the surface temperature of the support rings. The more heat is removed, the cooler the support ring surface becomes. The cooler the support ring surface, the lower the tendency to scale up tinder.

During the production, for example, of thin slabs, hot steel comes into contact with oxygen in the atmosphere. As a result, the steel surface is oxidized to form scale. Such scale formation basically takes place wherever oxygen in the surrounding gas medium is available for reaction with a steel surface.

During transport of a thin slab through the furnace, scale separates from the slab surface and is removed by scale flaps in the lower part of the roller hearth furnace. On the other hand, however, even on contact between the thin slab and the furnace roller in the roller hearth furnace, scale can adhere to the support ring surface and form growths there, which impress into the thin slab underside and appear as surface defects on the rolled hot strip depending on the depth. Such errors then lead to the committee and thus represent a serious quality problem for the plant operators.

The document DE 40 22 768 describes roller table rollers for conveying and guiding a workpiece by a heating oven comprising shafts whose ends are rotatably supported in bearings. These form wheel-like support devices in the longitudinal direction of the shaft at a distance from each other on the outer periphery are fixed, wherein the radially outermost surfaces of the wheel-like support devices serve as a support for the workpiece, while this is passed through the heating oven. The wheel-like support devices consist of a hub, which communicates via ribs with a rim-like, continuous wreath. The ribs are separated by open spaces to reduce their cross-sectional area and thereby impede heat flow from the rim to the hub. The hub consists of a plurality of angularly spaced cores comprising a nose-like portion and a head portion. A weld only connects the nose-like portions to the shaft so that the head portions may shift with respect to the shaft due to differential expansion and flexing. Means for thermally insulating the shaft are essentially the portions between adjacent wheel-like support devices and the walls of the furnace. The means for rotating the shaft are located outside the furnace.

The post-published European patent application EP 1 134 531 A1 discloses a disk roll for roller hearth furnaces for heating Wärmgut. On a rotatable, internally cooled support tube a plurality of axially spaced from each other on the support tube arranged support rings is arranged. These sit on two lateral support elements and are detachably connected thereto. To improve the durability and to simplify the disassembly of the support ring, the support elements in the circumferential direction on rounded ridges, which are distributed at a distance from each other on the circumference of the support elements and engage in correspondingly shaped recesses in the support rings.

The document EP 0 633 815 B1 describes a furnace roll for supporting a heated workpiece having a rotatable shaft for receiving a coolant, a number of axially spaced support rings being mounted thereon. A thermally resistant insulating agent that surrounds the Axially mounted shaft extends axially between the support rings, wherein the insulating means has an outer surface which extends radially over at least a considerable part of the radius of a pair of support rings. The insulating means is secured in the shaft by anchoring means with protruding terminal ends disposed radially inwardly of the outer surface of the insulating means. The spacer is made of a metal which allows for the pourable insulating a voltage drop in the thermal expansion of the anchoring means and deflection of the furnace roller.

The document DE 38 07 240 C1 describes a roller hearth furnace for heating slabs, blocks, billets, sheets and the like warm goods, the furnace chamber is formed with a longitudinally extending roller table. The oven has a hot upper oven room, and a sub-furnace room, and in between a hearth with recesses. The roller table is stored substantially in the lower furnace space below the hearth and protrudes only with small sections of its furnace rollers through the recesses of the hearth floor above its level. At least the projecting into the hot zone roller sections with their treads on which the warm goods is transported, made of particularly heat-resistant material which, composed of segments into a ring, the furnace rollers encase on the peripheral surface. Cleaning devices free the running surfaces of the furnace rollers from scale caking.

Based on the aforementioned prior art, the present invention seeks to provide means for further improvement of the heat transfer between support rings and shaft, thereby increasing the heat dissipation from the support rings to the shaft and to extend the availability of the support rings with reduced growth of scale and at the same time to ensure a reliable, secure torque transmission between support rings and shaft and to achieve greater flexibility in their arrangement with reduced effort when applying the support rings on the shaft.

To solve the problem is provided in a coolable furnace roller specified in the preamble of claim 1 with the invention that for the production of an optimal metallic contact for a possible unhindered heat transfer between the support ring and shaft, the contact surfaces on the inner diameter of the receiving bore of the support ring and / or on Outer diameter of the shaft in the form of a polygonal profile with mating surfaces of approximately constant diameter are designed as so-called weak equal thickness.

With great advantage, in this embodiment of the transitional region between the support ring and the shaft, the small deviation of the direct dodge from the ideal round, the circular shape, causes an automatic tightening of the support ring seat on the shaft during torque transmission. In this case also the contact surface of both the support ring, and the shaft is plastically and elastically deformed, which has a significant increase in the contact surfaces result, and as a further advantage results in a significantly improved heat conduction or a significantly improved heat transfer between the support ring and shaft.

In this case, the inner diameter of the support ring, which becomes larger as a result of thermal expansion, is also compensated by the relative rotation with respect to the shaft. Overall, the surface temperature of the furnace roll is reduced in the design according to the invention due to the increased contact surface of the support ring and shaft and more intimate metallic contact and increases their availability, and reduces the risk of pick-up formation on the surface.

Further advantages result from the fact that the distances between the support rings on the shaft are freely selectable. Thus, the structure of the furnace roller is extremely flexible and can be optimally adapted to the respective stresses.

In addition, the design is simplified, because no additional parts are required for torque transmission shaft / support ring.

In addition, with the use of thin inserts, which additionally increase the heat conduction in the contact area shaft / support ring, the heat transfer can be further improved.

Further advantageous embodiments of the invention are provided according to the subclaims.

Figur 1

einen Tragring in Ansicht mit geschnittener Welle und Paßflächen eines schwachen Gleichdicks, im montierten Ausgangszustand

Figur 2

den Tragring gemäß Fig. 1 im Betriebszustand nach Erwärmung;

Figur 3

Tragring und Welle in Ansicht und z.T. geschnitten, mit Paßsitz als Gleichdick mit ca. 1,7 mm Abweichung von der Kreisform, im Wärmeschaubild.

Details, features and advantages of the invention will become apparent from the following explanation of some schematically illustrated in the drawings Ausführungsbeispiete. Show it:

FIG. 1

a support ring in view with cut shaft and mating surfaces of a weak Gleichdicks, in the mounted initial state

FIG. 2

the support ring of Figure 1 in the operating condition after heating.

FIG. 3

Support ring and shaft in view and partially cut, with snug fit as equal thickness with about 1.7 mm deviation from the circular shape, in the heat chart.

Fig. 1 shows the support ring 7 with cut shaft 3 in the assembled starting state with snug fit 6 with a slight deviation of a polygonal profile of the circular shape of a few millimeters. It is a so-called weak "equal thickness".

The shaft 3 has in its tubular cavity a central coolant channel 4, and a peripheral coolant ring channel 5.

Fig. 2 shows the support ring 7 with the cut shaft 3 in the operating state under load by torsional stress, as well as in the heated state.

The preferred embodiment of the same thickness provides that the deviation of the mating surfaces 6, 6 'from the ideal round, the circular shape, a self-locking in a torque transmission between the support ring 7 and shaft 3 corresponds. This deviation of the mating surfaces 6, 6 'from the ideal round can - depending on the design and stress in mechanical and / or thermal nature - be about 1 to 5 mm.

The support ring 7 is about Gleichdick-fitting tolerances 6, 6 'purely mechanically pushed onto the shaft 3 and jammed by relative rotation with the shaft 3, wherein the attachment of the support ring 7 on the shaft 3 according to the principle of surface enlargement by deformation of the contact surfaces 6, 6 'takes place.

At least the deviation of the mating surfaces 6, 6 'from Idealrund should be slightly larger than the thermal expansion of the inner diameter of the receiving bore 1 of the support ring 7 during operation of the furnace. This receiving bore 1 forms the inner contact surface 6 with the mating surface 6 'of the shaft third

Next, the invention provides that the metallic contact is made over the same thickness either over the entire width of the furnace roll or over their sub-areas. The support ring 7 may be one or more pieces, or be made of individual rings.

In the manufacture of the furnace roller thin inserts, for example. From silver foil between support ring 7 and shaft 3, in particular in its multi-part design or film of a resistant and highly heat conductive metal such as CuNiBe, be inserted.

Fig. 3 shows an embodiment of the invention, according to which formed as a polygon profile with constant diameter equal thickness so weak fitting tolerances between the contact surfaces on the inner diameter of the support ring 7 and the outer diameter of the shaft 3, that a rotation of support ring 7 and shaft 3 due to the transfer of a Torque leads to a comparatively large elastic-plastic deformation.

At the deformation regions 6, 6 'prevail optimum metal contacts with ideal heat conduction conditions, and allow an unhindered Wäre mefluß from the support rings 7 in the shaft 3, as can be seen from the heat diagram of Figure 3.

Claims (8)

1. Water-coolable furnace roller for conveying transport stock, for example cast strip material of a continuous casting plant, through a roller hearth heating-up furnace, comprising a shaft (3), which is drivable in rotation and mounted outside the furnace, particularly with internally disposed coolant channels (4, 5), and with carrier rings (7) which are arranged on the shaft (3) by means of a receiving bore (1) and which form a conveying plane, characterised in that the contact surfaces at the internal diameter of the receiving bore (1) of the support ring (7) and/or at the external diameter of the shaft (3) are formed in the form of a polygonal profile with fit surfaces (6, 6') of approximately constant diameter as a so-called weak orbiform curve.
2. Furnace roller according to claim 1, characterised in that the deviation of the fit surfaces (6, 6') from ideal roundness, the circular form, corresponds with a self-locking in the case of torque transmission between carrier ring (7) and shaft (3).
3. Furnace roller according to claim 1 or 2, characterised in that the deviation of the fit surfaces (6, 6') from ideal roundness is approximately 4 to 5%.
4. Furnace roller according to one or more of claims 1 to 3, characterised in that the deviation of the fit surfaces (6, 6') from ideal roundness corresponds at least with the amount of thermal expansion of the internal diameter of the receiving bore (1) of the carrier ring (7) during operation of the furnace.
5. Furnace roller according to one or more of claims 1 to 4, characterised in that the metallic contact is produced by way of the orbiform curve either over the entire width of the furnace roller or over part regions thereof.
6. Furnace roller according to one or more of claims 1 to 5, characterised in that the carrier ring (7) is of single-part or multi-part construction or produced from individual rings.
7. Furnace roller according to one or more of claims 1 to 6, characterised in that thin shims, for example of silver foil or foil of a wear-resistant and highly heat conductive metal, such as, for example, CuNiBe, are inserted between carrier ring (7) and shaft (3).
8. Furnace roller according to one or more of claims 1 to 7, characterised in that the orbiform curve formed as a polygon profile with constant diameter has such weak fit tolerances between the contact surfaces at the internal diameter of the receiving bore (1) of the carrier ring (7) and the outer diameter of the shaft (3) that twisting of carrier ring (7) and shaft (3) as a consequence of transmission of a torque leads to a comparatively substantial elastic-plastic deformation.

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