GB2068779A

GB2068779A - Device for spraying cooling agent on steel blooms

Info

Publication number: GB2068779A
Application number: GB8039118A
Authority: GB
Original assignee: Lechler GmbH and Co KG; Mannesmann AG
Current assignee: Lechler GmbH and Co KG; Vodafone GmbH
Priority date: 1980-02-09
Filing date: 1980-12-05
Publication date: 1981-08-19
Also published as: IT8119444A0; CA1165971A; AU539792B2; DE3004864A1; AU6681281A; GB2068779B; BE886955A; FR2475435A1; FR2475435B1; CH651487A5; JPS56122654A; ATA571680A; AT381881B; IT1135251B; BR8100478A; DE3004864C2

Abstract

A cooling spray device for steel blooms, more particularly continuous cast ribbons, comprises a mixing chamber (16) having separate inlets (17, 18) for impellant and cooling agent, with nozzle outlets formed by diametrically opposed prismatic apertures (30, 31) milled in a cylindrical nozzle housing (15) and opening into a cylindrical entry bore (24) into which the mixing chamber (16) opens, the outlets being so directed that the spray is at an acute angle (q) to the radial plane in which the outlets lie, and the coolant entry (18) into the mixing chamber is through a replaceable insertion pipe (19) projecting into the mixing chamber. A continuous casting installation, (Figs. 1, 2, not shown) has one such spray device (14) between each adjacent pair of guide rolls (10) on the upper face of the cast ribbon (12) and successive spray devices are alternately displaced through a certain distance (d) on either side of the central axis (13) of the cast ribbon, with the distance (d) about half the breadth (f) of the unwetted bloom surface. <IMAGE>

Description

SPECIFICATION Device for spraying cooling agent on steel blooms This invention relates to a device for spraying a cooling agent on steel blooms, comprising spray nozzles connected to a mixing chamber having separate inlets for the impellant and the cooling agent, the nozzle outlets being so adapted that the impellant-coolant mixture impinges on the bloom surface in a broad fan and at an acute angle in mutually opposed directions, the nozzle outlets projecting from a common nozzle housing into which the mixing chamber opens, while the coolant union on the mixing chamber is formed by a replaceable insertion pipe projecting into the mixing chamber.The invention is particularly applicable to a continuous casting installation from which blooms emerge in the form of cast ribbons, the nozzles being directed into each gap between successive pairs of guide rolls for the cast ribbon and being directed parallel to the guide roll axes, and the nozzle housing being disposed between the mid-plane of the guide roll axes and the bloom surface.

A device having the significant features specified above forms the subject of prior German Patent Application P 28 1 6 441.2-24. The cited prior Application is concerned substantially with the following problems: 1. The mixture of water, air, steam or gas should be uniformly distributed over the bloom and uniformly accelerated as it is sprayed over the width of the bloom.

2. It should be possible to spray into the roll shadows (i.e., the generally triangular gaps between the bloom surface and the rolls), and simultaneously the clearing action of the mixture stream should remove stagnant water and scale particles from the gaps between the rolls.

3. The water throughput should be adjustable, without of course impairing the spray pattern and without replacing a given nozzle.

The object of the present invention is to provide such a device with an improved performance so that: a) a more extensive heat exchange surface is attained by a broader fan-shaped jet, b) a more intensive cooling action is brought about by smaller droplets and the individual droplets can evaporate more rapidly, while c) droplets which do not evaporate are cleared laterally across the bloom.

In addition, it is intended to simplify the nozzle design.

According to the present invention, these objects are achieved by providing a nozzle housing that is cylindrical or substantially cylindrical and having a cylindrical entry bore, while the nozzle outlets are formed by prismatic milled apertures in the nozzle housing, diametrically opposite each other and each opening radially into the entry bore.

The invention avoids the concept embodied in the device of the prior Patent Application P 28 16 441.2-24 of providing opposed nozzle outlet openings, i.e., openings directed towards each other. This provides the advantageous possibility of broadening the jet to the required extent without mutual interference between the jets (which would ensue with the device of the prior Patent Application).

The concept of the invention, whereby the nozzle construction is so modifed that the jets are no longer directed in opposition to each other, simultaneously leads to a simpler nozzle construction.

Preferaby, the cylindrical entry bore of the nozzle housing is formed as a blind hole having a hemi-spherically shaped inner end, while the milled lateral apertures forming the nozzle outlets open into the hemispherical end-zone of the entry bore in the nozzle housing.

A further preferred feature of the invention consists in that a disc-shaped spinner is provided inside the entry bore in the nozzle housing, in advance of the nozzle outlets. The spinner is preferably adapted so that the previously formed mixture of water and air, which contains a higher proportion of water in the centre of the mixing chamber (considered radially) than in the peripheral zones, is mixed still more intensively. In this way the average droplet diameter can be advantageously reduced.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view (taken from the line I-I in Fig. 2) of part of a cast ribbon passing between guide rolls; Figure 2 is a part sectional view taken from the line ll-ll in Fig. 1; Figure 3 on a larger scale than that of Figs.

1 and 2 is an exploded view of a cooling device (with some parts partly sectioned) in accordance with the invention and for use as indicated in Figs. 1 and 2; Figure 4 is a view of the nozzle housing seen at the bottom of Fig. 3, looking in the direction of the arrow A; Figure 5 is a section taken on the line V-V in Fig. 3; and Figure 6 is a plan view of the spinner half of which can be seen in the sectioned half of the nozzle housing in Fig. 3.

Figs. 1 and 2 show pairs of opposed parallel guide rolls 10 and 11 in a continuous casting machine for steel blooms. Each steel bloom 1 2 passes between the guide rolls 10 and 11 of each pair, and successive pairs of guide rolls are disposed with relatively small intermediate spacings a. A cooling device 1 4 is directed towards the upper face of the steel bloom 1 2 between each adjacent pair of guide rolls 10.

As shown in more detail in Fig. 3, the cooling device 1 4 comprises a nozzle housing 1 5 and a mixing chamber 1 6 having a lateral union 1 7 to admit an impellant, for example air, and a coaxial union 1 8 for coolant, for example water.

As Fig. 3 further shows, the coolant union 1 8 is substantially adapted as a tubular insert 1 9 projecting into the tubular mixing chamber 16. A fixing nut 20 having an internal thread 21 is welded to the upper end of the tubular insert 19. The nut 20 and the thread 21 are used to fix the tubular insert 1 9 on a corresponding thread 22 on the mixing chamber 1 6. An external thread 23 is provided on the upper end of the nut 20, for connection to a coolant supply line, normally for example with the aid of a cap nut.The coolant, water, is admitted into the tubular insert 1 9 at 23 and passes thence into the mixing chamber 1 6 at a flow rate which is precisely determined by the internal diameter of the tubular insert 1 9.

Thus, by replacing a given tubular insert 1 9 by one of larger or smaller diameter, it is a simple matter to adjust the flow rate of cooling water independently of the flow rate of air entering the mixing chamber 1 6 at 1 7 and independently of the geometry of the nozzle housing 1 5. Since the tubular insert 1 9 can be replaced with ease, various flow rate ratios of coolant to impellant can be selected with corresponding ease without interfering in any way with the nozzle housing 1 5 itself. Moreover, no adjustments need be made for this purpose in the pressure settings of the coolant supply line on the one hand or the impellant supply line on the other.

By reason of the relatively large cross-section of the mixing chamber 16, friction losses in the mixture advancing to the nozzle are kept low, with the advantageous effect of raising the exit velocity.

A further advantage in the same sense accrues from the fact that the stream of mixed coolant and impellant in the nozzle housing 1 5 is divided into two separate streams. As Fig. 3 further shows, the nozzle housing 1 5 has a cylindrical entry bore 24, in the form of a blind hole. The entry bore 24 has two shoulders, and an internal thread 25 at its upper end meshes with a corresponding external thread 26 on the mixing chamber 16. The blind hole 24 contains a disc-shaped spinner 27, which is supported axially on a shoulder 28 in the blind hole 24 of the nozzle housing 1 5. Fig. 6 shows the spinner 27 in plan view.

Its circular periphery has four milled radial notches 29 spaced at angles of 90 to each other. The spinner 27, in conjunction with the arrangement and construction already described, brings about still more intensive mixing in the mixture of water and air already present in the mixing chamber 16, whereby the average droplet diameter in the jets emerging from the nozzle housing 1 5 can be advantageously reduced still further. It will be eeen by reference also to Figs. 4 and 5, that the nozzle has two outlets formed by two diametrically opposed prismatic milled apertures 30 and 31 in the nozzle housing 15.

The apertures 30 and 31 are milled so that they penetrate into the blind-hole entry bore 24 in the nozzle housing 15, in a hemispherical end-zone 32 of the entry 24 to form two nozzle outlets 33, the shape of each of which is shown particularly clearly in Fig. 4.

The prismatic milled apertures 30 and 31 are inclinced at an angle y (Fig. 3) of 5" relative to their respective planes of symmetry about the horizontal plane of the bloom surface. The nozzle outlets 33 produce two broad fan jets directed in opposite directions (see Figs. 1 and 2). The two fan jets extend in plan view (Fig. 1) over a larger angle a and at right angles thereto (Fig. 2) over a smaller angle ss.

The advantage of extending the jet over a wide angle a is to be seen in that within a short distance from the nozzle outlet the entire breadth of the free bloom surface seen in the casting direction 1 3 - is covered with spray. The advantage of extending the jet over the angle ss consists in that the incidence zone of the spray jet on the bloom surface -- see in the jet direction 34 - is increased. The planes of the fan jets extending over the angle a lie parallel to the bloom surface.In other words, a larger proportion of the exposed bloom surface between guide rolls 10- denoted by the dimension c in Fig. 1 - is covered with a shorter distance from the nozzle housing 1 5 than can be achieved with the device of the prior Application P 28 1 6 441.2-24. These advantages, based on the angles a, P and y, significantly improve the uniformity of bloom cooling. The above advantages appertain to each fan jet individually.The distinction between the fan jets produced by a device in accordance with the invention and by the prior device of P 28 1 6 441.2-24 is substantially characterised in that individual fan jets are produced, having a broad extent (angle a) and little widening at right angles thereto (angle P), whereas the device of the prior Application P.28 1 6 441.2-24 produces somewhat flattened oval jets from approximately circular initial jets.

Another significant distinction from the prior device of P 28 16 441.2-24 consists in that the nozzle housing 1 5 is located no further than 1 50 mm from the nozzle-facing end of the tubular insert 1 9 in the mixing chamber 1 6. This dimension b is shown in Fig. 3. It relates of course to the assembled state of the individual components and not as shown exploded in Fig. 3.

Figs. 1 and 2 also disclose a further significant feature of the invention. This consists in that the successive spray devices 1 4 arrayed in the casting direction 1 3 are alternately displaced through a distance dfrom the central axis 35 of the cast ribbon, first to the left and then to the right. The lateral displacement d of each spray device 14 is adjusted accord ing to the width e of the spraying gap. In fact, as Fig. 2 shows, it amounts to about half the breadth fof the unsprayed bloom surface.

Since the spray device in the next guide-roll gap is displaced over the same distance d on the other side of the central axis 35, the entire breadth of the bloom 1 2 is covered with liquid by a pair of cooling devices 14.

To summarise, the following significant advantages accrue from the device of the invention: The prismatic apertures 30, 31 forming the nozzle outlets 33, each spraying outwards from the central axis of the mixing chamber 16, produce fan jets the angular dimensions (a and ss) of which can be adjusted by varying the geometry of the entry bore 24 and of the apertures 30, 31. This facilitates a more uniform coverage of the bloom surface requiring cooling. The mixing chamber 1 6 in conjunction with the spinner 27 in the nozzle housing 1 5 produces more effective mixing between the water and air, thereby reducing the droplet size in the spray jets. The smaller droplets in the spray jets ensure more intensive cooling of the bloom surface, since the individual droplets evaporate more rapidly. Finally, the device of the invention has the special advantage that the two spray jets do not intersect, but are both directed outwardly. This facilitates a very simple nozzle housing construction.

Claims

1. A device for spraying a cooling agent on steel blooms, comprising spray nozzles connected to a mixing chamber having separate inlets for the impellant and the cooling agent, the nozzle outlets being so adapted that the impellant-coolant mixture impinges on the bloom surface in a broad fan and at an acute angle in mutually opposed directions, the nozzle outlets projecting from a common nozzle housing into which the mixing chamber opens, while the coolant union on the mixing chamber is formed by a replaceable insertion pipe projecting into the mixing chamber, the nozzle housing being cylindrical or substantially cylindrical and having a cylindrical entre bore, while the nozzle outlets are formed by two prismatic milled apertures in the nozzle housing, diametrically opposite each other and each opening radially into the entry bore.

2. A device as in Claim 1, wherein the nozzle outlets are milled at an angle of 2-10", preferably 5 , relative to the bloom surface.

3. A device as in Claim 1 or Claim 2, wherein the cylindrical entry bore in the nozzle housing is a blind hole having a hemispherical end-zone.

4. A device as in Claim 3, wherein the milled apertures forming the lateral nozzle outlets open into the hemi-spherical end-zone of the entry bore in the nozzle housing.

5. A device as in any one of the preceding Claims, wherein a disc-shaped spinner is provided in front of the nozzle outlets in the entry bore in the nozzle housing.

6. A device as in any one of the preceding Claims, wherein the nozzle housing is mounted at a distance of no more than 1 50 mm from the nozzle end of the tubular insert in the mixing chamber.

7. A continuous casting installation from which blooms emerge in the form of cast ribbons passing between successive pairs of guide rolls, with a device as in any one of the preceding Claims between each adjacent pair of guide rolls on the upper surface of the cast ribbon, and successive spray devices are alternately displaced through a certain distance on either side of the central axis of the cast ribbon.

8. An installation as in Claim 7, wherein the lateral displacement of the spray devices is about half the breadth of the unwetted bloom surface.

9. A device for spraying a cooling agent on steel blooms and substantially as hereinbefore described with reference to Figs. 3 to 6 of the accompanying drawings.

1 0. A continuous casting installation substantially as hereinbefore described with reference to the accompanying drawings.