Blowing lance tip

Abstract

A blowing lance tip includes a central stirring gas-supply tube, an inner coolant-inlet tube ending, at one end thereof facing the bath, in a second front wall and having a central opening, an outer coolant-outlet tube, a heat exchange space, and a stirring gas-outlet pipe leading from each opening in the front wall, wherein the second front wall has, at the central opening, an edge which is curved in axial cross-section such that a height (H3) is defined between a leading face of said edge and the third front wall, and such that, in the heat exchange space, a predetermined minimum height (H1) is present on the side facing the central opening.

Claims

1. A blowing lance tip for bath stirring, comprising: a central tube configured for supplying stirring gas, closed at a bath end by a first front wall provided with at least two openings; an internal tube forming with the central tube a first annular cavity for flowing a cooling liquid and ended at the bath end by a second front wall, having a central opening and one passage orifice per opening provided in said first front wall; an external tube forming with the internal tube a second annular cavity for flowing the cooling liquid and closed at the bath end by a third front wall having one outlet orifice per opening provided in said first front wall and having an internal surface comprising a tapered central area which is directed towards said central opening and which has a curved enveloped surface in an axial section; a heat exchange space located between a) said second front wall and said third front wall and b) said central opening and said second annular cavity, and in which the cooling liquid flows; and an injector leaving each opening in said first front wall and extending to said corresponding outlet orifice passing through said corresponding passage orifice in a cooling liquid-tight manner, wherein said second front wall has an edge in an axial section at the central opening which is curved such that a height (H3) is defined between a front of said edge and said third front wall, wherein in the heat exchange space a minimum predetermined height (H1) is present on a side of said central opening, such that a ratio H1/H3 is between 5% and 80% and wherein said second front wall has a surface turned towards the bath end which is substantially sinusoidal, said heat exchange space having a maximum height Hmax between a central area of the second front wall and the third front wall.

2. The blowing lance tip according to claim 1, wherein a distance R is perpendicular to a longitudinal axis L of the blowing lance tip between said front of the edge of the second front wall and the longitudinal axis L, said distance R being such that a ratio R/H3 is between 20% and 150%.

3. The blowing lance tip of claim 1, wherein the external tube has external surfaces, the blowing lance tip having a predetermined external diameter (Dext) measured between said external surfaces and wherein said edge of the second front wall is defined by a thickness (e1) such that a ratio e1/Dext is between 5% and 30%.

4. The blowing lance tip of claim 1, further comprising a pillar comprising a first end (E1) linked to a central area of an external surface of the first front wall and a bath end (E2) linked to the central area of the internal surface of the third front wall.

5. The blowing lance tip of claim 4, wherein the pillar has a thinned part (I) between said first and second ends (E1 and E2) linked to the central area, which has a predetermined length L1 and an axial section decreasing in such a way that the pillar forms a continuous curved section with the central area of the internal surface of the third front wall.

6. The blowing lance tip of claim 5, wherein said thinned part I of the pillar has a minimum predetermined diameter D3 at said second end (E2) and said central area of the internal surface of the third front wall has a height h and a base b so a ratio h/(b-D3) is between 20% and 120.

7. The blowing lance tip of claim 1, wherein a deflector is substantially centered in central stirring gas supply tube.

8. The blowing lance tip of claim 1, wherein the injector has a revolution axis (m) oriented obliquely with respect to a longitudinal axis (L) of the blowing lance tip.

9. The blowing lance tip according to claim 1, wherein the ratio H1/H3 is between 5% and 75%, 5% and 70%, 5% and 65%, 5% and 60%, 10% and 60%, 15% and 60%, 20% and 60%, 25 and 60%, between 25% and 55%, or 30% and 55%.

10. The blowing lance tip according to claim 1, wherein the ratio H1/H3 is between a range between 30% and 55%.

11. The blowing lance tip according to claim 2, wherein the ratio R/H3 is between 30% and 140%, 30% and 130%, 40% and 130%, 50% and 130%, 60% and 120%, 60% and 110%, or 70% and 110%.

12. The blowing lance tip according to claim 2, wherein said distance R being such that a ratio R/H3 is between a range of 70% and 110%.

13. The blowing lance tip according to claim 3, wherein the ratio e1/Dext is between 7% and 25%, 7% and 20%, or 7% and 15%.

14. The blowing lance tip according to claim 3, wherein the ratio e1/Dext is a between 7% and 15%.

15. The blowing lance tip of claim 6, wherein the ratio h/(b-D3) is between 20% and 110%, 30% and 110%, 30% and 100%, 40% and 100%, 40% and 90%, 45% and 85%, or 50% and 80%.

16. The blowing lance tip of claim 6, wherein the ratio h/(b-D3) is between a range of 50% and 80%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other details and advantages of the invention will become clearer from the following description, which is not limiting, and by referring to the appended drawings.

(2) FIG. 1 is a front view of the lance tip.

(3) FIG. 2 shows a sectional view following the line II-II of FIG. 1, in a particular embodiment of the lance tip according to the invention.

(4) FIG. 3 represents a detail of a lance tip according to the invention, to illustrate the characterising part of the invention.

(5) FIG. 4 represents a view similar to that of FIG. 2, of a variation of a blowing lance tip according to the invention.

(6) FIG. 5 represents a detail of a lance tip according to the invention, to illustrate the method for measuring the parameters necessary for an advantageous embodiment of the invention.

(7) In the figures, similar or identical elements bear the same references.

DETAILED DESCRIPTION

(8) FIG. 1 shows the third front wall 12 of the lance tip 1 which is turned towards the bath. According to this embodiment, the lance tip 1 has six stirring gas outlet orifices 13 placed in a ring around a central area 14 of the third front wall 12.

(9) FIG. 2 shows the lance tip according to the present invention wherein the stirring gas is supplied via the central tube 2. This central tube 2 is closed by a front wall 3 directed towards the bath provided with at least two openings 4.

(10) An internal tube 5 is arranged in a coaxial manner around the central tube 2 in order to form an annular cavity 6 between them, for supplying the cooling liquid in the direction of arrow F.sub.1. This internal tube 5 is ended by a front wall 7 which is known as a separator. This front wall 7 is provided with a central opening 8 and an orifice 9 in alignment with each opening 4 in the central tube 2. The separator 7 according to the present invention has a particular geometry and arrangement with respect to the third front wall 12 which will be outlined below.

(11) An external tube 10 is arranged coaxially around the internal tube 5. This external tube forms an annular cavity 11 with the internal tube 5, which is used for the exit of the cooling liquid in the direction of arrow F.sub.2. This external tube is closed by a front wall 12 which faces the bath to be stirred and comprises an internal surface 30. As shown in FIG. 2, the internal surface 30 of the third front wall 12 is provided with a tapered central area 14 which is directed towards the central opening 8 and which has a curved envelope surface in axial section.

(12) The front wall 12 is also provided with an outlet orifice 13 in alignment with each opening 4 provided in the front wall 3 and with each passage outlet 9 provided in the front wall 7. In each of these aligned outlets and openings, an outlet conduit 17 is arranged for the ejection of stirring gas outside the lance tip. The revolution axes m of the conduits 17 are advantageously obliquely arranged with respect to the longitudinal axis L of the lance tip.

(13) The cooling of this front wall 12 is ensured by the circulation of the cooling liquid in the heat exchange space 16 which is situated between the separator 7 and the internal surface 30 of the front wall 12. In the illustrated embodiment, the cooling liquid coming from the cavity 6 passes through the central opening 8 into the heat exchange area 16 following arrow F.sub.3. The liquid then flows outwardly in the direction of arrow F.sub.2, namely towards cavity 11.

(14) In FIG. 3, the separator 7 according to the present invention is substantially flat and substantially parallel to the internal surface 30 of the third front wall 12. This separator 7 has a central opening 8, a curved axial section edge 18. A minimum diameter of the central opening 8 may then be measured from the front 19 of the edge 18 of the separator 7. The tangent passing by this front 19 and parallel to the longitudinal axis L of the lance tip allows the smallest diameter of the central opening 8 to be measured.

(15) The height taken along the tangent passing by the front 19 and parallel to the longitudinal axis L of the lance tip and measured between said front 19, and the internal surface 30 of the third front wall 12 corresponds to the height H3 as indicated in FIG. 3. The height H1 is, in turn, measured, parallel to the revolution axis m of the injectors 17, between the surface turned towards the bath 20 of the separator 7 and the internal surface 30 of the third front wall 12, on the side of the central opening 8. This height H1 defines a minimum passage height for the cooling liquid in the heat exchange space 16 at the central opening 8. In the volume contained in the cone passing through the revolution axes of the injectors, H1 is the minimum height of the water passage along the internal surface of the third front wall in the heat exchange space. According to the present invention, the ratio H.sub.1/H.sub.3 is advantageously between 30% and 55%.

(16) The curved axial section of the edge 18 of the separator 7 advantageously accompanies the cooling liquid during its convergence in the central opening 8. In addition, as shown in FIG. 3, the edge 18 of the separator 7 has a positive fit with the tapered central area 14 of the internal surface 30 of the third front wall 12. The liquid is therefore kept in contact with the internal surface of the third front wall 12, which is the most exposed to the thermal stresses. Consequently, a flow of cooling liquid with reduced disturbances and cavitation phenomena may be obtained and maintained along its path. The cooling liquid thus calmed may then calmly bypass the obstacles which the injectors 17 form in the heat exchange space 16 before leaving the tip by the second annular cavity 11 following arrow F.sub.2.

(17) The external diameter D.sub.ext of the lance tip 1 according to the present invention corresponds to the diameter measured between the external surfaces of the external tube 10, as represented in FIG. 2.

(18) Generally, a thickness of the separator 7 is measured between the surface 21 turned towards the first front wall 3 and the surface turned towards the bath 20 of the separator 7.

(19) The thickness e1 of the edge 18 of the separator 7 is therefore measured parallel to the revolution axis m of the injector 17 in the continuity of the minimum height H1 of the heat exchange space 16 at the central opening 8. This thickness allows the separator to occupy a consistent volume in the lance tip and allows, in combination with the curve section of the edge 18, a flow of the cooling liquid with reduced disturbances and good acceleration to be maintained. Preferably the ratio e1/D.sub.ext is between 5% and 15%,

(20) In a particular embodiment of the lance tip represented in FIG. 3, the surface turned towards the bath 20 of the separator 7 is substantially sinusoidal. In the event of the surface turned towards the bath 20 of the separator 7 having a substantially sinusoidal form, the maximum thickness e1 is measured between the surface 21 turned towards the first front wall 3 and the tangent passing by the minimum of the concave part of the surface turned towards the bath 20. On the contrary, a minimum thickness is measured between the surface 21 turned towards the first front wall 3 and the tangent passing by the maximum of the convex part of the surface turned towards the bath 20.

(21) This means that the separator 7 also has its thickness e1 at the central opening 8, a substantially minimum thickness in its centre so the heat exchange space 16 has a substantially maximum height H.sub.max in the centre of the separator 7. The object of this maximum height H.sub.max is to allow more space for the cooling liquid during its passage in the region of the injectors 17 in the heat exchange space 16.

(22) FIG. 4 represents a particular embodiment of the lance tip according to the present invention. In this embodiment, a central pillar 22 of particular configuration is present in the centre of the central opening 8.

(23) The pillar 22 has a first end E1 on the side of the first front wall 3 and a second end E2 linked to the central area 14 of the internal surface 30 of the third front wall 12. This pillar preferably has a thinner part I between the first end E1 and the second end E2 which allows a continuous curved surface 23 to be formed with the tapered central area 14 of the internal surface 30 of the third front wall 12. In this way, the cooling liquid coming from the first annular cavity 6 following arrow F.sub.1 moves along the upper face 21 of the separator 7 where it shall bypass the injectors which form a first obstacle in the path of the liquid and then converge in the central opening 8. The pillar 22 present in the centre of this central opening 8 then allows the cooling liquid to be guided towards the internal surface 30 of the third front wall 12 or the thinned part I of the pillar ensures the passage of the liquid between this pillar 22 and the edge 18 of the separator 7, following arrow F.sub.3. Furthermore, the connection of the tapered central area 14 of the internal surface 30 of the third front wall 12 with the pillar 22 has a continuous curved surface 23 ensuring a progressive rotation of the liquid following arrow F.sub.3. The turbulences in the cooling liquid then arriving in the heat exchange space 16 are reduced and the liquid may calmly bypass the injectors occupying a significant volume in the heat exchange space 16. In this example, the calories accumulated in the front wall 12 exposed to the molten liquid bath are transferred to the pillar 22 whose surface of contact with the cooling liquid is increased thanks to its thinned part I, which improves the metal/liquid thermal transfer.

(24) Furthermore, the pillar 22 advantageously has a second part II of predetermined length L2 connecting said thinned part I and said first end E1, said second part II having a circular transversal section defined by a predetermined diameter D2, constant along the length L2, such that the ratio D2/D.sub.ext is advantageously between 10% and 15%.

(25) In fact, the pillar 22 being formed of a material of good thermal conductivity, the heat rising from the bath and transferring to the third front wall 12 and its central area 14 where it may then be led by the pillar 22 towards the cooling liquid. The latter moving around the pillar 22 ensures constant catchment of the heat of the third front wall 12. In order to optimise this, the parts most exposed to the bath, namely the third front wall 12 and the pillar 22, are produced in wrought copper which ensures better thermal conductivity than cast copper.

(26) Advantageously, the first thinned part I is further characterised by a predetermined diameter D1 which gradually changes from diameter D2 at the connection with the second part II to a value preferably between 60% and 80% of D2 at the second end E2 of the pillar 22. The diameter D1 of the thinned part I of the pillar 22 thus progressively reduces as it moves along the longitudinal axis L of the lance tip towards the bath until reaching a minimum value, then called D3 corresponding to the second end E2 of the pillar.

(27) Preferably, the continuous curved surface 23 between the thinned part I of the pillar 22 and the tapered central area 14 of the internal surface 30 of the third front wall 12 is characterised by a radius of curvature greater than or equal to 30% of diameter D2 in the second part II of the pillar 22.

(28) In the embodiment presented in FIG. 4, the separator 7 and the thinned part I of the pillar 22 facing each other have a positive fit, thus ensuring the most delicate accompaniment of the cooling liquid possible. In fact, the edge 18 of the separator 7 and the thinned part I of the pillar 22 allow a path to be formed for the cooling liquid, reducing the turbulences in the liquid.

(29) A deflector 24 may also be placed in the centre of the tube 2 for supplying stirring gas. This deflector 24 allows the gas leaving the central conduit 2 to be appropriately derived for engaging in the injectors 17.

(30) FIG. 5 represents a detail of the tapered central area 14 in order to clarify the method for measuring the parameters relative to this central area 14 of the internal surface 30 of the third front wall 12. The height h is measured between the plane tangent 32 of the internal wall 30 of the lance tip perpendicular to the longitudinal axis L and the parallel plane 31 tangential to the top of the tapered central area 14. If an additional element in the tapered central area 14 is provided at the top of this, such as, for example, pillar 22, the plane 31 remains in the position that it would adopt if this additional element did not exist. The top of the tapered central area 14 coinciding with the transversal section of the thinned part I of pillar 18 having a minimum diameter D3, the plane 31 also passes by this section of minimum diameter D3 of the pillar 22.

(31) The base b is located in the plane tangent 32 of the internal wall 30. It is contained by the intersection points 33 with the extension of the internal wall 30.

(32) Advantageously, the tip according to the invention has a ratio h/(b-D3) between 50% and 80%. Therefore, in the event where no additional element, such as, for example, a pillar, is present in the central area 14, D3 is zero and the ratio h/b is preferably between 50% and 80%.

(33) FIG. 5 also represents distance R for the cooling liquid passage taken perpendicularly to the longitudinal axis L of the tip in the central opening 8. When no pillar is present in the central opening 8, the distance R is measured between the front 19 of the separator 7 and the longitudinal axis L, this distance for the cooling liquid passage is then labelled R.sub.1 and corresponds to the minimum radius of the central opening 8. When a pillar 22 is present in the central opening, the liquid passage distance R is then measured between the separator 7 front 19 and the external surface of the thinned part I of pillar 22, the distance is then labelled R.sub.2. In these two scenarios, this distance for the cooling liquid passage is such that the ratio R/H3 is preferably between 70% and 110%, with R corresponding to R1 in the absence of a pillar or corresponding to R2 in the presence of a pillar.

(34) It is understood that the present invention is in no way limited to the embodiments described above and that modifications may be applied without leaving the scope of the appended claims.