Diffusion article

Abstract

A diffusion component for impregnating molten steel with a gas includes a barrier having a first side and a second side, a through-hole formed within the barrier, the through-hole connecting the first side to the second side, and a porous element arranged within the through-hole such that the flow of molten steel passes over the porous element. At least one flow disrupter is arranged relative to the porous element and configured to promote non-laminar flow of molten steel passing through the through-hole.

Claims

1. A method for removing non-metallic inclusions from molten steel within a tundish, the tundish including a barrier that divides a tundish volume into a steel receiving volume and a steel dispensing volume, the method comprising: directing the molten steel through at least one tunnel formed in the barrier wherein an outlet of the at least one tunnel is flared; emitting a wall of gas bubbles along an entire width of the at least one tunnel, whereby non-metallic inclusions within the molten steel attach to the gas bubbles and are carried to a surface region of the molten steel; and creating non-laminar flow of the molten steel as the molten steel flows through the at least one tunnel, whereby the non-laminar flow causes intermixing of the gas with the molten steel.

2. The method according to claim 1, wherein emitting the wall of gas comprises dispersing the gas through a porous element.

3. The method according to claim 2, wherein dispersing the gas through the porous element comprises using a porous element that spans the entire width of the at least one tunnel.

4. The method according to claim 1, wherein directing the molten steel through the at least one tunnel comprises decreasing a velocity of molten steel exiting the at least one tunnel relative to a velocity of molten steel entering the at least one tunnel.

5. The method according to claim 1, further comprising deflecting the gas bubbles away from the barrier along a surface of the molten steel.

6. The method according to claim 1, wherein emitting a wall of gas bubbles comprises emitting at least one of a Nitrogen gas or an Argon gas.

7. The method according claim 1, wherein creating non-laminar flow comprises subjecting the flow of molten steel to a flow disrupter arranged within the at least one tunnel.

8. The method according to claim 7, wherein subjecting the flow of molten steel to a flow disrupter comprises causing the molten steel to pass over a surface having surface irregularities.

9. The method according to claim 7, wherein subjecting the flow of molten steel to a flow disrupter comprises causing the molten steel to pass over a surface having a series of peaks and valleys.

10. The method according to claim 7, wherein subjecting the flow of molten steel to a flow disrupter comprises causing the molten steel to pass over a surface having at least one of an undulating contour or a sinusoidal contour.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein:

(2) FIG. 1 is a side cross-sectional view of a diffusion component in accordance with an embodiment of the invention arranged within a tundish;

(3) FIG. 2 is a front cross-sectional view of diffusion component in accordance with an embodiment of the invention arranged within a tundish;

(4) FIG. 3 is a detailed view of the diffusion component in accordance with an embodiment of the invention; and

(5) FIG. 4 is an enlarged view of a lip portion of the diffusion component in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

(6) Referring now to the drawings wherein the showing is for illustrating a preferred embodiment of the invention only and not for limiting the same, the invention will be described with reference to the figures.

(7) As discussed herein, re-oxidation of liquid steel in a tundish readily occurs and creates non-metallic inclusions. A device and method in accordance with the invention can enhance removal of such inclusions.

(8) Referring initially to FIGS. 1 and 2, illustrated is a tundish 10 that includes a plurality of sidewalls 12a, 12b, 14a, 14b each connected to a bottom wall 16 to define an interior space 18. As shown in the exemplary embodiment, the sidewalls may be angled relative to each other to define trough, although other configurations are possible. A refractory material 20 is arranged adjacent each side and bottom wall to insulate the walls from molten steel within the tundish 10.

(9) Arranged within the interior space 18 is a diffusion component 22 in accordance with the present invention. The diffusion component 22 may include and/or be formed of refractory materials to enable the diffusion component to withstand the temperatures encountered with molten steel. As can be best seen in FIG. 2, the diffusion component 22 spans between walls 14a and 14b, which divides the interior space of the tundish 10 into a first sub-space 18a and a second sub-space 18b. Lifting means, such as clasps 23, provide a means for installing and removing the diffusion component 22 from the tundish 10. As will be described in further detail below, the diffusion component 22 exposes the molten steel to gas that attaches to inclusions in the steel, whereby the gas then carries the inclusions to an upper layer of the molten steel.

(10) A baffle 24 is also arranged within the interior space 18 of the tundish 10 and spans between walls 14a and 14b to define a third sub-space 18c, the baffle including a tunnel 26 that enables transfer of molten steel between the second and third sub-spaces. While three sub-spaces 18a, 18b, 18c are illustrated, more or fewer sub-spaces may be utilized depending on the specific application requirements. A submerged entry nozzle 28 is arranged in a bottom portion of the third sub-space 18c for removal of molten steel from the tundish 10 for further processing

(11) In operation, molten steel from a ladle (not shown) enters the first sub-space 18a of the tundish 10 via a ladle shroud 29 and fills the first subspace 18a. The steel flows from the first sub-space 18a to the second sub-space 18b via a through-hole 32 formed in the diffusion component 22. As the molten steel flows through the through-hole 32, an inert gas, such as argon or nitrogen, is emitted from a porous element 34 arranged in a bottom portion of the through-hole 32. A wall of bubbles is formed in the through-hole 32, and all of the molten steel passes through this wall of bubbles, thus eliminating blind spots. The inclusions 30 (FIGS. 3 and 4) in the molten steel attach to gas bubbles 31 and are carried to an upper layer 33 of the molten steel, thereby facilitating removal of the inclusions 30 from the molten steel. The molten steel then flows from the second sub-space 18b to the third sub-space 18c via the tunnel 26 within the baffle 24. Since the tunnel 26 is arranged below the upper layer of molten steel, the inclusions 30 are trapped in the second sub-space 18b. The “filtered” molten steel in the third sub-space 18c exits the tundish 10 through the submerged entry nozzle 28 for further processing.

(12) With additional reference to FIG. 3, the exemplary diffusion component 22 is shown in more detail. The diffusion component 22 is formed as a barrier that is dimensioned to fit within the tundish 10 from one sidewall to another sidewall. The diffusion component 22 includes a first side 22a and a second side 22b, where the through-hole 32 connects the first side 22a to the second side 22b, e.g., the through-hole forms a tunnel. In one embodiment, a cross-sectional area of the through-hole 36 is at least two times a cross-sectional area of the submerged entry nozzle 28. This size relationship ensures that a flow capacity of the through-hole 32 meets or exceeds a flow capacity of the submerged entry nozzle 28.

(13) In one embodiment, the diffusion component 22 includes a first portion 23a having a first wall thickness, a second portion 23b having a second wall thickness (the portion in which the through-hole 32 is formed), and a third portion 23c having a third wall thickness, where the second wall thickness and the third wall thickness are each greater than the first wall thickness. The third portion 23c may include a radiused section 23d that transitions from a first direction to a second direction that is generally orthogonal to the first direction. An advantage of such transition is that the inclusions 30 are directed away from the diffusion component 22 and along an upper surface of the molten steel.

(14) The through-hole 32 may take various shapes. For example, in one embodiment a cross section of the passage 32c between an inlet 32a of the through-hole 32 and an outlet 32b of the through-hole 32 tapers linearly, becoming larger at the outlet 32b relative to the inlet 32a (e.g., the passage 32c connecting the inlet to the outlet is tapered such that a surface area at the outlet 32b is larger than a surface area at the inlet 32a). In another embodiment, the outlet 32b of the through-hole 32 is flared, e.g., the region of the passage 32c just before the outlet 32b exponentially increases in size. The tapered and flared features of the through-hole 32 have the effect of decreasing a velocity of molten steel as it exits the outlet 32b relative to a velocity of molten steel entering the inlet 32a. This slowing down of the flow can prolong the time the molten steel is exposed to the gas and thus promote attachment of inclusions 30 to the gas 31.

(15) The porous element 34 is arranged along a bottom portion of the through-hole 32 such that the flow of molten steel passes over the porous element 34. The porous element may be formed from alumina, alumina-silicate, alumina-chromia, or magnesia based permeable refractory. The permeability could be organized randomly or directionally.

(16) The porous element 34 may correspond to a shape of the through-hole 32. For example, if the through-hole is rectangular, the porous element may be in the form of a rectangular element having a width that spans the entire width of the through-hole 32. This ensures that no blind spots exist within the through-hole and that all of the molten steel passing through the through-hole is exposed to the gas. The length of the porous element 34 can span at least a portion of the length of the through-hole 32. In one embodiment, the length of the porous 34 element is the same as the length of the through-hole 32 (e.g., from the input to the output of the through-hole). In another embodiment, the length of the porous element is less than a length of the through-hole.

(17) A chamber 38 may be arranged beneath the porous element 34 and configured to receive an inert gas via a conduit 40, the conduit extending to an exterior region of the diffusion component 22. The conduit 40 may be at least partially embedded within the diffusion component between the first side 22a and the second side 22b. The chamber 38 evenly provides the received gas to the porous element 34, which creates a wall of bubbles within the through-hole 32.

(18) To ensure all molten steel passes through the gas emitted from the porous element 34, the porous element 34 spans an entire width of the through-hole 32. In one embodiment, the through-hole 32 has a generally rectangular shape. However, other shapes are possible, such as an oval or circular shape, so long as the porous element 34 is configured to create a wall of gas through which substantially all of the molten steel passes as it moves from the first side 22a to the second side 22b of the diffusion element 22. The porous element 34 may span the entire length of the through-hole 32. For example, the porous element may begin at the inlet 32a and span through the passage 32c to the outlet 32b. Alternatively, the porous element 34 may span a portion that is less than an entire length of the through-hole 34. However, the porous element should be of sufficient length to create a wall of gas bubbles within the through-hole 32. For example, the porous element 34 may be approximately 12-14 inches in length.

(19) Arranged relative to the porous element 34 is at least one flow disrupter 42, which is configured to promote non-laminar flow of molten steel passing through the through-hole 32. The one or more flow disrupters 42 may take on various configurations. For example, the flow disrupters 42 may be formed in a surface of the porous element 34 as surface irregularity, e.g., a sharp change in the surface contour of the porous element 34. Alternatively or additionally, the flow disrupters 42 may be formed in at least one of a surface of the porous element, a bottom wall, sidewall or top wall of the through-hole 32, and/or may be positioned parallel or perpendicular to the flow of molten steel. Each flow disrupter may include one or more surfaces having a series of peaks and valleys. The peaks and valleys may form a surface contour that is undulating and/or sinusoidal. As the molten steel passes through the through-hole 32, the flow disrupters 42 create turbulence that promotes better inter-mixing of the steel and the gas, thus promoting better attachment of the inclusions 30 with the gas bubbles 31.

(20) The present invention thus provides more a uniform mixing and interacting of the gas with the molten steel, thereby facilitating better removal of inclusions from the molten steel.

(21) The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purposes of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.