EP0101224B1

EP0101224B1 - Water jet nozzle assembly

Info

Publication number: EP0101224B1
Application number: EP19830304367
Authority: EP
Inventors: Sadao Ebata
Original assignee: Kawasaki Steel Corp
Current assignee: JFE Steel Corp
Priority date: 1982-08-10
Filing date: 1983-07-28
Publication date: 1988-02-10
Also published as: AU546810B2; DE3375647D1; EP0101224A2; EP0101224A3; FI832833A0; AU1747983A; FI832833A; FI73001B; FI73001C

Description

This invention relates to a water jet nozzle assembly, and more particularly to a nozzle assembly for jetting cooling water against under- sides of materials such as steel plates and the like for cooling the materials.
In steel manufacture, steel plates are treated to improve their mechanical properties by rapidly cooling them from high temperatures or the red heated condition i.e. by a so-called "hardening" or "quenching" or rapid cooling treatment. In this treatment, cooling water is jetted against the upper and under surfaces of the steel plates to be cooled. In this case, particular precautions must be taken in order to cool the undersides of the plates effectively.
The cooling water jetted from nozzles onto the upper surface of the steel plates will stay thereon for the required period of time, so that the overall upper surfaces are cooled in a substantially uniform and effective manner. In contrast herewith, on the under-sides of the steel plates however, the cooling effect occurs only at locations where the jetted water initially impinges. After the water has impinged against the underside surface, it immediately drops away from the surface and thereafter it does not cool the surface. It is therefore difficult to cool the undersides of the plates uniformly and effectively.
There have been various kinds of nozzles in the prior art such as spray nozzles, circular opening nozzles, laminar flow nozzles and the like. These nozzles do not provide a satisfactory solution to the problem. For example FR-A-2 005 744 discloses an assembly for applying coolant to the underside of plate material comprising a header to receive coolant under pressure and provided with a plurality of apertures whereby coolant can flow out of the header in the form of a plurality of jets. The jets of coolant flow in the same direction and are deflected against the underside of the plate material by a curved plate mounted adjacent to the apertures. However once the coolant has imnpinged on the underside of the plate material and dropped away, its cooling action is finished.
Further when cooling steel plates in strip mill lines, it is difficult to arrange cooling nozzles under the plates because of the short distance between adjacent table rollers over which the plates are trained.
It is a principal object of the present invention to provide an improved water jet nozzle assembly which is capable of effectively and rapidly cooling the undersides of plate materials.
It is another object of the present invention to provide a water jet nozzle assembly adapted to be arranged in a small space such as between table rollers of steel strip mill lines without affecting the cooling capacity.
According to the present invention there is provided a water jet nozzle assembly for location under plate material to apply water to the underside thereof to cool the same comprising an elongated header supplied with cooling water under pressure, means for removing water from the header in the form of a plurality of jets, and a guide means to deflect the jets so that water impinges on said underside characterised in that the means for removing water from the header is such as to form a first plurality of said jets flowing in a first direction and a second plurality of said jets flowing in a second direction which is generally opposite to said first direction and two of said guide means are provided, one for said first plurality of jets and one for said second plurality of jets so that after impinging on said underside water from the jets deflected by the first guide means and water from the jets deflected by the second guide means both flow along the underside towards one another and join together priorto falling away from said underside and recombining with water flowing in said first and second directions.
In a preferred embodiment of the invention, the header is in the form of a hollow cylinder formed along both sides at a mid level with a plurality of apertures in substantially horizontal alignment with each other and spaced by substantially equal intervals to form the means of removing water from the header. Water flowing through these apertures forms said first and second pluralities of jets and the first and second directions of flow are substantially horizontal. The two guide means are in the form of two elongated curved plates having a substantial quadrant-shaped cross-section which are secured to the cylinder below the apertures.
In a further preferred embodiment of the invention the header is in the form of a U-shaped trough. In this case an elongated curved plate is arranged on the U-shaped trough so as to close its top and so that the free longitudinal edges of the curved plate extend upwardly. The means of removing water from the header comprises a plurality of apertures formed in the bottom of the curved plate at substantially equal intervals and diverter plates arranged above the respective apertures so that the jets of water flowing up out of the header via the apertures are diverted and flow in first and second opposite directions which are substantially horizontal directions.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which:

Fig. 1 is a partial sectional plan view of a first embodiment of a water jet nozzle assembly according to the invention;
Fig. 2 is a side view of the assembly shown in Fig. 1;
Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1;
Fig. 4 is a sectional view illustrating the cooling operation of the assembly shown in Figures 1 to 3;
Fig. 5 is a partial sectional plan view of a second embodiment of a water jet nozzle assembly according to the invention;
Fig. 6 is a sectional view taken along line VI-VI in Fig. 5;
Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 6;
Fig. 8 is a sectional view illustrating the cooling operation of the assembly shown in Figures 5 to 7; and
Fig. 9 is a cross-sectional view of a third embodiment of a water jet nozzle assembly according to the invention.

Referring to Figs. 1-3 illustrating the first embodiment of the invention, the water jet nozzle assembly 1 mainly comprises a header 2 and guide means in the form of plates 3. The header 2 is in the form of an elongated cylinder having a substantially horizontal axis and having an inner cross-sectional area such as to jet supply water substantially uniformly over its length. The header 2 is provided at one end (the right end as viewed in Figs. 1 and 2) with a flange 2a adapted to be connected to a conduit (not shown) for supplying the water under pressure and is closed at the other end by a closure disc 2b.
The header 2 is provided in its sidewalls with a plurality of apertures 2c in alignment with each other and parallel with the axis of the header 2. The apertures 2c have diameters of, for example, the order of 3-10 mm and are spaced apart by substantially equal intervals.
Water emanating from the apertures 2c is in the form of a first plurality of jets flowing in a first direction and a second plurality of jets flowing in a second direction which is opposite to the first direction. These jets are turned upward by means of the guide plates 3 (later described) to form an upward water flow in the form of a film or laminate. Although the apertures are shown to be circular, they may be square, rectangular or the like. Moreover, although the first and second directions are horizontal in this embodiment, these directions may be slightly oblique relative to the horizontal provided that they are generally opposite to one another.
The guide plates 3 are in the form of elongated plates curved so as to be quadrant shaped in section i.e. as if they were obtained by dividing a circular pipe along its generators into four equal parts. The guide plates 3 are secured to the outer surface of the sidewalls of the header 2 so that one longitudinal edge of the guide plate is adjacent to the lower edges of the apertures 2c and the other longitudinal edge of the plate extends upwardly towards the underside of the material to be cooled.
The guide plates have curved smooth upper surfaces and are secured to the header 2 such that tangential lines to the curved upper surfaces of the guide plates at the lower edges of the apertures are aligned with the first and second directions in which the water jets from the apertures 2c flow. The guide plates may be secured to the header by welding.
The guide plates 3 serve to turn upwards the water jets flowing from the apertures 2c and to widen the water flow to form flowing films by gathering together the respective jets of water.
Referring now to Fig. 4 illustrating the operation of the water jet nozzle assembly according to the invention, the water flows W₁, W₂ and W₃ formed by the action of the guide plates on the jets from the apertures 2c of the header 2 are cooling a plate material 4 trained along table rollers 5.
The water supplied into the header 2 is jetted from the apertures 2c in horizontal directions and guided and turned along the curved upper surfaces of the guide plates 3 upwards towards the material 4 to be cooled. The upward flow is supplemented by recovered water from flow W₃, later mentioned, and forms the water flows W, which impinge against the lower surface of the material 4 to be cooled.
When the water flow W, collides against the lower surface of the material, the flow W, is divided into two halves W₂ and W₃. W₂ flows along the lower surface away from the water jet nozzle 1 to cool the material 4 and then falls away and W₃ flows along the lower surface in a direction opposite to W₂ to cool the material 4 and then collides against the water flow W'₃ coming from the opposite direction so that the water flows W₃ and W'₃ combine with each other and then fall away onto the water jet nozzle assembly 1 and are recovered. When the united water flows W₃ and W'₃ fall onto the centre of the water jet nozzle assembly 1, the water splits and fows in separate directions along the outer surfaces of the header 2 and onto the guide plates 3 where it combines with new water jetting from the apertures 2c, respectively, and is energized by the new water jets to form water flows W, flowing upward towards the material 4.
With this arrangement, the amount of water supplied or water jetted from the apertures 2c is substantially equal to the amount of the water W₂ which is consumed or wasted after being used for cooling. Accordingly, the amount of recovered water W₃ reused is also substantially equal to the amount of water jetted from the apertures 2c. These amounts of water are indicated in the following equation. (water flow: W,) = (water flow jetted from apertures 2c) + (water flow W₃) = (water flow jetted from the apertures 2c) x 2 Namely, the water flow cooling the material 4 is twice the supplied water flow.
It is well known that the cooling rate of the material increases as the amount of cooling water increases. Accordingly, the water jet nozzle assembly constructed as above described according to the invention can cool material very effectively and rapidly in comparison with nozzles of the prior art, because 2 litres of jetted water are applied to the plate material for each litre of water supplied to the header. In one experiment for measuring the cooling capacity of a water jet nozzle assembly according to the invention, the cooling rates of steel plates from a temperature of 800°C to 500°C with a flow rate of 500 l/min.m² of cooling water were approximately 1.5 times those obtained using conventional spray nozzles under the same condition.
In the above embodiment, the water flow W, is directed vertically upward and the flows W₂ and W₃ are substantially equal in amount. In other words, the reused water ratio is 1 (one), that is, (total amount of flow W₂)/(total amount of supply water flow) = 1. However, the guide plates 3 may have sections which are somewhat more than a quadrant, so that the free upper ends of the guide plates are inclined towards each other as shown in phantom lines in Fig. 3. With this arrangement, the water flows W₁ are also inclined towards each other, resulting in (water flow W₃) ) (water flow W₂). In this case, it will be understood that the reused water ratio is more than one, so that more effective and rapid cooling can be carried out.
With the above embodiment, the header 2 and the two guide plates 3 are arranged side by side in a horizontal line, so that the two water flows W₁ directed upwards along the upper surfaces of the guide plates 3 are properly spaced apart from each other. The water jet nozzle assembly according to the embodiment is therefore most suitable for cooling plate materials in slabbing mill lines whose table rollers are sufficiently spaced that such water jet nozzle assemblies can be located therebetween without any trouble.
With this water jet nozzle assembly, however, the header 2 is arranged between the two guide plates 3 and it has a relatively large diameter so that the overall width L of the nozzle assembly is fairly large which makes it impossible to use it for cooling plate materials in strip mill lines whose table rollers are not sufficiently spaced.
Referring to Figs. 5-7 illustrating a second embodiment of the invention suitable for use in such strip mill lines, the water jet nozzle assembly 11 mainly comprises a header 15 in the form of a U-shaped trough, a guide plate 12, and diverters 13. The guide plate 12 has a substantially semicircular cross-section and is substantially horizontally arranged on the header 15 integrally therewith to close its upper open side. Each half of the guide plate 12 constitutes a guide means to upwardly deflect, in a smooth manner, water jetted into the bottom of the plate from the header. Its cross-sectional shape may be semicircular, deep U-shaped, or shallow or widened U-shaped. The guide plate is formed in its bottom with a plurality of apertures 12a communicating with the interior of the header 15 for jetting cooling water supplied to the header 15. The apertures 12a are preferably circular having diameters of, for example, 3-10 mm and are spaced apart by equal intervals. However, the apertures may be square or rectangular or longitudinally elongated slits orthe like.
The diverters 13 comprise spacers 14 integrally formed therewith which serve to support the diverters 13 above the respective apertures 12a of the guide plate and are welded to the guide plate to form clearances G between the guide plate and the diverters. The diverters 13 serve to form the water upwardly flowing from the header via the apertures 12a into first and second pluralities of jets flowing in first and second opposite directions which are substantially horizontal directions.
The header 15 uniformly distributes the supply water and jets it from the apertures 12a. In this embodiment, the header is shown to be box- shaped in cross-section and directly welded to the underside of the guide plate. However, the shape of the header 15 is not limited to that shown in the drawing.
Referring to Fig. 8 illustrating the operation of the water jet nozzle of the second embodiment, the water flows W1, W₂ and W₃ formed by the action of the guide plate 12 on the jets from the diverters 13 are cooling a plate material 16 trained on table rollers 17.
The water supplied into the header 15 is upwardly guided through the apertures 12a and then divided at the diverters 13 to form first and second pluralities of jets in opposite horizontal directions. The horizontal jets are deflected by the upper surfaces of the guide plate so as to impinge against the underside of the plate material 16.
With this embodiment, the water flows W₁, W₂ and W₃ and W' flow in substantially the same manner as in the first embodiment with the exception that the united water flows W₃ and W' fall onto the diverters and then flow in separate directions on the diverters and the guide plate 12 where they combine with new water jets from the apertures 12a.
In this embodiment, the water flow cooling material 16 is twice the suplied water flow in the same manner as in the first embodiment. According ly, the water jet nozzle of this embodiment can cool material no less effectively than the first embodiment. In an experiment, it has been found that the cooling rate of a water jet nozzle of the second embodiment is also about 1.5 times that obtained using conventional spray nozzles.
Moreover, the guide plate 12 may have a cross section which is more than semicircular so that the free upper ends of the guide plate are inclined towards each other as shown in phantom lines in Fig. 7. In this way the water flows W₁ are inclined towards each other, thereaby increasing the reused water flow to carry out a more effective cooling as in the first embodiment.
Fig. 9 illustrates a third embodiment of the invention which is a slight modification of the second embodiment. In this case the water jet nozzle assembly 31 includes modified diverters 33. Each diverter 33 comprises a circular disc and a spacer 34 forming a hollow cylinder closed at its upper end by the circular disc and formed with through-holes 34b perpendicular to an axial hole 34a. The hollow cylinders are inserted and fixed in a plurality of apertures formed in the bottom of the guide plate 32 along its length at equal intervals such that the through-holes 34b extend in transverse directions with respect to the length of the guide plate 32 and the lower edges of the through-holes 34b are in line with the upper surface of the guide plate 32.
With the arrangement shown in Fig. 9, the water flows guided through the axial holes 34a are jetted through the through-holes 34b along first and second opposite horizontal directions and further advanced along the upper surface of the guide plate 32 which deflects their directions upwards towards the material to be cooled. The flows and cooling operation thereafter are substantially the same as those explained with respect to Fig. 8.
As can be seen from the above description, the water jet nozzle assembly according to the invention is capable of effectively cooling the under- sides of plate materials and is applicable to cooling zones having not only wider table pitches as in slab mill lines but also narrower table pitches as in strip mill lines.

Claims

1. A water jet nozzle assembly for location under plate material to apply water to the underside thereof to cool the same comprising an elongated header supplied with cooling water under pressure, means for removing water from the header in the form of a plurality of jets, and a guide means to deflect the jets so that water impinges on said underside characterised in that the means (2c) (12a, 13) (34a) for removing water from the plurality of said jets flowing in a first direction and a second plurality of said jets flowing in a second direction which is generally opposite to said first direction and two of said guide means (3) (12) (32) are provided, one for said first plurality of jets and one for said second plurality of jets so that after impinging on said underside water from the jets deflected by the first guide means and water from the jets deflected by the second guide means both flow along the underside towards one another and join together prior to falling away from said underside and recombining with water flowing in said first and second directions.

2. A water jet nozzle assembly as claimed in claim 1 wherein the header is in the form of a horizontally arranged hollow cylinder (2) and said means for removing water from the header comprises a plurality of apertures (2c) extending along one side of the header in substantially horizontal alignment with each other and spaced apart by substantially equal intervals and a second plurality of apertures (2c) extending along the opposite side of the header in substantially horizontal alignment with each other and spaced apart by substantially equal intervals whereby said first and second directions of flow are substantially horizontal and each guide means is in the form of an elongated curved plate (3) having a substantially quadrant shaped cross-section which is secured to said cylinder below said apertures (2c).

3. A water jet nozzle assembly as claimed in claim 2, wherein the free ends of the plates (3) are inclined towards each other.

4. A water jet nozzle assembly as claimed in claim 1 wherein the header is in the form of a horizontally arranged U-shaped trough (15) (35) which is closed at its top by an elongated curved plate (12) wherein said means for removing water from the header comprises a plurality of substantially equally spaced apertures (12a) formed in the botton of the curved plate (12), and diverters (13) arranged above the respective apertures (12a) to cause jets of water to flow in said first and second directions which are substantially horizontal and wherein each half of the curved plate (12) constitutes one of said guide means.

5. A water jet nozzle assembly as claimed in claim 4, wherein the free ends of the curved plate (12) are inclined towards each other.

6. A water jet nozzle assembly as claimed in claim 4 or 5, wherein each diverter comprises a hollow cylinder (34) having its upper end closed by a circular disc (33), said hollow cylinder (34) being formed with horizontal through-holes (34b).