EP0443304B1 - Cooling device for a moving cylindrical object - Google Patents

Abstract

The cooling device comprises a tubular rectilinear conduit (1) pierced with a plurality of passages (C1.01,...,C8.12) arranged in plane rings (C1,...,C8) perpendicular to the longitudinal axis of the conduit (1) and angularly offset with respect to one another. Seen in the direction of movement of the cylindrical element, each passage belonging to any one of the rings (C1,...,C8), with the exception of the first (C1), is located substantially at the centre of the circumferential distance separating the generatrices of the tubular conduit (1) which pass via two angularly successive passages in the set of rings preceding the ring in question. The set of rings may be divided into groups (G1, G2, G3) which follow one another in the direction of movement, each group comprising a number of rings which is sufficient to include a passage located at the centre of each of the circumferential distances separating the generatrices which pass via two angularly successive passages in the set of rings preceding the group in question. <IMAGE>

Description

The present invention relates according to the preamble of claim 1 to a device for cooling a cylindrical element in movement, such as a metal tube, making it possible to operate a homogeneous cooling of this cylindrical element.

The following description refers more particularly to the cooling of a steel tube at the outlet of a reducing rolling mill. It goes without saying that this particular application was chosen only for the simple purpose of illustrating the invention without any limiting effect with regard thereto. The device of the invention can be used for cooling any type of cylindrical element, solid or hollow, made of ferrous or non-ferrous metal, capable of undergoing the considered treatment.

The expression “cylindrical element in movement” is understood here to mean a product of elongated shape, for example a bar or a tube, which moves by translation along its longitudinal axis without turning around this axis.

Already known from document EP-A 0 366 639 (Art. 54 (3) EPC), a device for cooling a cylindrical element in movement, which comprises an envelope disposed around a perforated tubular conduit, with which it forms an annular chamber surrounding the cylindrical element to be cooled. The tubular conduit has perforations providing passage to the coolant of the cylindrical element. The perforations are arranged in flat rings perpendicular to the longitudinal axis of the tubular conduit, at equal distance in each ring, and each ring is angularly offset with respect to the neighboring ring.

In the most common variant of this known device, the various perforation rings are angularly offset with respect to each other by a constant angle and they are also equidistant in the longitudinal direction of the tubular conduit. In this way, the perforations are arranged in regular helices in the wall of this tubular conduit. This device makes it possible to operate a cooling, possibly intense, of the cylindrical element which passes through it.

In industrial practice, however, it is found that the intensity of this cooling is not always distributed uniformly along the periphery of the cylindrical element. This may result in heterogeneity in the microstructure of the surface layer of this element. This effect is particularly noticeable during the quenching and self-tempering treatment of tubes of relatively small thickness, for example less than 5 mm. Indeed, the presence of islands of returned martensite having the desired thickness is observed, formed at the locations of the surface of the tube cooled by the water jets coming from the perforations which constitute the first crowns encountered by the tube. Between these islands, the thickness of the returned martensite layer may be less, and sometimes even zero, which adversely affects the properties and therefore the behavior of the tube.

The object of the present invention is to provide a cooling device of the aforementioned type, in which the perforations are arranged so as to guarantee the homogeneity of the intensity of the cooling over the entire periphery of the cylindrical element in movement.

According to the present invention, a device for cooling a cylindrical element in movement, which comprises a straight tubular conduit open at its ends, inside which passes said cylindrical element to be cooled, said tubular conduit being pierced with a plurality passages arranged in flat rings, perpendicular to the longitudinal axis of said tubular conduit and angularly offset with respect to each other, is characterized in that, seen in the direction of travel of said cylindrical element, each passage belonging to any one of said crowns, with the exception of the first, is located substantially in the middle of the circumferential distance separating the generatrices of said tubular conduit which pass by two angularly successive passages in the set of crowns preceding said arbitrary crown.

According to a particular embodiment of this device, all of said crowns comprise the same number of passages and they are preferably arranged at equal distance from each other.

According to another characteristic of the invention, said rings are divided into successive groups in the direction of travel of said cylindrical element, each group comprising a number of rings sufficient for said group to have a passage located in the middle of each of the circumferential distances separating the generators which pass through two angularly successive passages in the set of crowns preceding said group.

In a manner known per se, said tubular conduit can be surrounded by an envelope with which it forms an annular chamber coaxial with the cylindrical element to be cooled.

According to another variant, the perforations of said tubular conduit can be connected, individually or in any number, to means for supplying coolant, such as flexible pipes and flow control valves.

Fig. 1

montre une vue en perspective d'un conduit tubulaire réalisé conformément à l'invention; et la

Fig. 2

présente une vue développée d'une portion du conduit tubulaire de la Figure 1, précisant les dispositions relatives des passages dans les différentes couronnes.

Other features of the invention may also appear in the description which follows, devoted to a particular embodiment of the device of the invention which is illustrated in the accompanying drawings, in which the

Fig. 1

shows a perspective view of a tubular conduit produced in accordance with the invention; and the

Fig. 2

presents a developed view of a portion of the tubular conduit of Figure 1, specifying the arrangements relative passages in the different crowns.

These figures constitute schematic representations, deliberately limited to the perforated tubular conduit proper, and in which the same elements are always designated by the same references.

Figure 1 shows a perspective view of a tubular conduit (1), provided with eight rings (C1 - C8) each comprising twelve equidistant passages. These passages are numbered from the upper generator (2) of the tubular conduit (1), taken as a reference generator; they are counted clockwise, seen in the direction of the arrow (3) indicating the direction of travel of the cylindrical element, and they are designated by the marks (C1.01, C1.02, ... C1. 12; C2.01, C2.02 ...; ...; C8.01, C8.02 ...) according to the crown to which they belong.

The relative arrangement of the coolant passages will be described with reference to the portion of said tubular conduit (1), delimited by a bold line in the drawing of Figure 1. Due to the axial symmetry of the tubular conduit on the one hand and of the cylindrical element on the other hand, it is clear that this arrangement is repeated over the entire periphery of said tubular conduit (1).

The above-mentioned portion of the tubular conduit (1) is shown in a view developed in FIG. 2.

In the axial direction, the portion shown comprises the eight aforementioned rings (C1 - C8); in the circumferential direction, considered at the first ring (C1), it extends from the first passage (C1.01), located on the reference generator (2), to the middle of the distance separating the passages (C1.04 ) and (C1.05). As the crowns each include twelve passages in the example shown, two neighboring passages, in the same crown, are separated by an arc of 30 °, and the portion shown in Figure 2 covers an arc of 105 °.

In general, a ring comprising n passages leads to an angular spacing α = 360 ° / n between two neighboring passages.

The first crown (C1) serves as a reference for the arrangement of the passages of the following crowns. In all the crowns, the passages (Ci.01 to Ci.12) are distributed uniformly; only the angular offset of the crowns varies to meet the above condition.

The second ring (C2) is arranged in such a way that its passages (C2.01 to C2.12) are respectively located in the middle of an arc separating two neighboring passages from the first ring. The second ring is therefore offset by an angle of 15 ° clockwise from the first ring. The assembly formed by the first and second rings has a uniform distribution of the coolant passages, which are thus angularly spaced 15 °, if one looks in the direction of the arrow (3). The second ring (C2) thus constitutes, by itself, a first group (G1) of rings whose passages are located in the middle of the circumferential distances separating the generatrices which pass through two angularly successive passages in all of the preceding crowns, according to the feature of the present invention.

Similarly, the crown (C3) is offset from the reference crown (C1), by an angle, here 22 ° 30 ', that each of its passages (C3.01 to C3.12) is located in the middle of a circumferential distance separating the generatrices which pass through two angularly successive passages in the set of crowns (C1) and (C2); in this example, the passage (C3.01) is located between (C2.01) and (C1.02), (C3.02) is located between (C2.02) and (C1.03), etc.

In turn the crown (C4) is offset, with respect to the reference crown (C1), by an angle such, here 7 ° 30 ', that each of its passages (C4.01 to C4.12) is located in the middle of the circumferential distance separating the generators which pass through two other angularly successive passages in the set of crowns (C1) and (C2); in this example, the passage (C4.01) is located between (C1.01) and (C2.01), (C4.02) is located between (C1.02) and (C2.02), etc.

Therefore, all of the passages of the crowns (C3) and (C4) ensure the division of all the circumferential distances separating the generators which pass through the passages of all of the preceding crowns; they thus lead to a uniform distribution of the coolant passages, with spacing distances between these passages equal to a quarter of the distance separating two passages from the reference ring (C1). The crowns (C3) and (C4) therefore constitute a second group (G2) of crowns respecting the characteristic of the present invention. It should also be noted that the rings (C3) and (C4) can be interchanged without modifying the overall distribution of passages at the exit of the second group (G2).

The same reasoning shows that the circumferential distances separating the passages from the set of crowns (C1 to C4) can in turn be divided in two, this time by means of four successive crowns (C5 to C8). These four passage crowns, the order of which can be modified without disadvantage, constitute a third group (G3) of crowns meeting the fundamental condition of the present invention.

It is obviously possible to further increase the angular distribution density of said passages in the tubular conduit (1). It suffices to add one or more other groups of crowns after the aforementioned groups. By way of example, an extension of the tubular conduit (1) is shown diagrammatically in axis, where the position of the first passages belonging to two crowns (C9) and (C10) of a fourth group has been indicated. (G4). According to the reasoning explained above, this group (G4) must include eight crowns to ensure an additional and complete division, according to the present invention, of all the circumferential distances existing at the exit of the group (G3).

The great advantage of the subdivision of the crowns into successive groups, which has just been described, is that it ensures compliance with the basic condition of the invention each time one of said groups of crowns is complete.

The arrangement of the coolant passages in the tubular conduit (1) leads to a uniform angular distribution of these passages, seen in the direction of travel of the cylindrical element to be cooled. This results in uniform intensity cooling, even in the case of thin tubes.

Without departing from the scope of the claims, the invention is not however limited to the embodiment which has been described and illustrated. In particular, at least part of the passages belonging to at least two crowns of the same group could be gathered in the same crown without losing the advantage of subdivision by group. This gathering could even relate to at least part of the passages belonging to different groups, if the above-mentioned advantage is renounced. It is also possible, without departing from the scope of the invention, to modify the axial distances between the various crowns so as to arrange the passages along helical lines while respecting the conditions of the present invention.

Claims (5)

1. Device for cooling a moving cylindrical element, which includes a rectilinear tubular conduit (1) which is open at its ends, inside which the said cylindrical element to be cooled passes, the said tubular conduit (1) being perforated with a plurality of passages (C1.01,..., C8.12) arranged in plane rings (C1,...,C8), perpendicular to the longitudinal axis of the said tubular conduit (1) and angularly offset with respect to one another, characterized in that, seen in the direction of passing of the said cylindrical element, each passage belonging to any one of the said rings (C1,...,C8), with the exception of the first (C1), is located substantially to the centre of the circumferential distance separating the generatrices (2) of the said tubular conduit (1) which pass via two passages which are angularly successive in the set of rings preceding the said any one ring.
2. Device according to Claim 1, characterized in that all the said rings (C1,...,C8) comprise the same number of passages.
3. Device according to either of the preceding claims, characterized in that the said rings (C1,...,C8) are arranged at an equal distance from one another.
4. Device according to any of the preceding claims, characterized in that the said rings are divided into groups (G1, G2, G3) which succeed one another in the direction of passing of the said cylindrical element, each group comprising a number of rings which is sufficient for the said group to include a passage located in the centre of each of the circumferential distances separating the generatrices which pass via two passages which are angularly successive in the set of rings preceding the said group.
5. Device according to any of the preceding claims, characterized in that the said tubular conduit (1) is surrounded by a casing with which it forms an annular chamber coaxial with the said cylindrical element.

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