KR20000073349A - Ingot mold for continuous casting of molten metal, particularly for forming rectangular- or square-section steel billets - Google Patents

Abstract

The casting conduit 2 of the ingot mold 1 having a substantially rectangular cross section for continuous casting of molten metal according to the present invention has a radius of curvature of two portions 8 and 9, that is, a rounded inner edge 5. A first portion 8 having a variable inner cross-section gradually decreasing in the direction of flowing molten metal along the 2), and a rounded inner edge connected to the first portion 8, for a subsequent rolling operation may be It is divided into a second part 9 having a constant inner cross section with a radius of curvature. By designing the first portion of the cast conduit 2 in accordance with the present invention, the metal is prevented from being separated from the wall of the mold 1, in particular the edge 5, as it cools and shrinks through the conduit, thereby degrading the quality of the product. Casting speed is increased.

Description

INGOT MOLD FOR CONTINUOUS CASTING OF MOLTEN METAL, PARTICULARLY FOR FORMING RECTANGULAR- OR SQUARE-SECTION STEEL BILLETS}

The present invention relates to an ingot mold for continuous casting of molten metal, in particular for forming steel billets of rectangular or square cross section.

A billet or ingot is a continuous casting of molten metal, especially steel, in a conduit-shaped mold (ingot mold) followed by rolling (so-called "casting and direct rolling"). Can be molded. This technology allows for a significantly higher production rate and good quality products-due to the process of molten metal cooling and solidifying in the mold-which limits the maximum production rate and the range of products that can be produced from the same mold. Several drawbacks are currently being raised.

In other words, continuous casting in an ingot mold where the molten metal is cooled to start solidification is known to cause defects in the finished product. More specifically, the cooling that occurs by dissolving the material transferring heat to the wall of the mold is sufficiently effective only when the material is in contact with the wall, so that a surface layer of solid metal (so-called "skin") is formed and the material forms the mold. It gradually increases when it passes. However, when the material solidifies, it shrinks and separates from the mold's wall, especially the inner edge, thereby forming an air pocket between the metal surface and the mold's wall, which reduces the amount of heat to be released and slows the solidification process. . Thus, the metal surface (solid layer) continues to grow except for corners at which heat is not sufficiently released, only partially solidifying the molten metal and creating defects in the finished product.

It also increases the likelihood that cracks will form at the edges due to undesired stresses on the metal surface when falling away from the walls of the mold.

In other words, the obtained steel sheets have a low torsional strength, which is very likely to form cracks along the edge in the longitudinal direction, and the surface temperature is very nonuniform, all of which cause problems in subsequent rolling steps, resulting in a finished product. Quality deteriorates naturally.

In order to overcome these disadvantages, the casting speed can be kept relatively low to cool the material as uniformly as possible. It is also known to reduce the radius of curvature of the inner edge of the mold to reduce the formation of air bags while keeping the casting speed so high.

When casting only one type of material, it is possible to reduce the separation of the metal surface from the walls of the mold by improving the mold geometry, for example by using a properly tapered mold. However, this solution cannot be applied to molds that produce materials with different characteristics (eg different types of steel).

Finally, some known molds have a specific cross section for the molten metal passageway, for example with a concave wall. However, this type of mold reduces the separation problem but also cannot increase the casting speed beyond a certain limit.

It is an object of the present invention to provide an ingot mold for continuous casting of metal material designed to overcome the above-mentioned drawbacks typically associated with known molds. In particular, it is an object of the present invention to effectively cool the molten metal along all points and the entire length of the mold to prevent the metal from separating from the walls of the mold and even the edges of the mold, and to produce the highest quality products that can be rolled immediately. It is to provide an ingot mold that can be cast by.

In the present invention, a longitudinally longitudinal cast conduit through which molten metal passes and is cooled, wherein the cast conduit has a substantially rectangular cross section and is formed by paired first and second walls standing side by side substantially parallel. In an ingot mold for continuous casting of molten metal, in particular a rectangular or square cross section, wherein the paired first and second walls are substantially perpendicular to each other and form four inner edges. And the cast conduit comprises at least a first portion having a rounded inner edge and an inner cross section that gradually changes from each longitudinal axial first end, wherein the molten metal at each first end is each longitudinal axis opposite the first end. Supplied toward the second end of the direction; The change in the cross section of the at least first portion is determined by a continuous and corresponding corresponding change in the radius of curvature of the rounded inner edge; The radius of curvature is reduced from the maximum value of the first end to the minimum value of the second end.

More specifically, the change in the cross section of the at least first portion of the cast conduit is for regenerating thermal contraction of the molten metal when molten metal passes through the at least first portion.

Ingot molds of a particular design according to the present invention effectively cool the molten metal along all surface points of the mold, i.e. the inner edge and the entire length. Indeed, the workpiece always remains in contact with the mold's walls, i.

Thus, the metal is prevented from separating from the walls, i.e., edges, of the mold without having to keep the casting speed too low. Cooling inside the mold according to the present invention is effectively achieved, due to the material having the desired properties (especially no internal stress at the edges and a uniform surface temperature), immediately rolling out the product exiting the conduit without the need for any intermediate process. can do. In addition, the same mold can be used to produce different materials, for example different types of steel, while at the same time ensuring high quality product production and maintaining high production rates.

Non-limiting embodiments of the invention will be described by way of example with reference to the accompanying drawings.

1 is a perspective view schematically showing an ingot mold for molten metal continuous casting according to the present invention.

2 is a plan view schematically showing a molten metal inlet section of the mold illustrated in FIG.

1 and 2, the components are intentionally shown to emphasize the main features of the present invention in an unbalanced manner, with reference numeral 1 designating a molten metal, for example steel, in cross section. The ingot mold continuously cast in the form of a rectangular slab is shown as a whole.

The mold 1 comprises a cast conduit 2 elongated in the longitudinal direction through which molten metal passes; The conduit (2) has a substantially rectangular cross section and is formed by a pair of first walls (3) and second walls (4) of a predetermined size standing side by side in parallel; The paired walls 3, 4 are perpendicular to each other and form four edges 5.

In the illustrative example shown in FIG. 1, the conduit 2 is curved into a flat wall 3 and a wall 4 having a predetermined curvature, but, as described, can be longitudinally oriented, for example straight. Is clear. In either case, the conduit 2 extends in a predetermined direction substantially parallel to the pair of flat walls 3.

In the present invention, the conduit (2) is each first longitudinal end portion (7) to which molten metal is supplied, comprising: a first portion (8) having a variable inner cross section; And a continuous second portion 9 having a constant inner cross section and terminating at the second end 10 of the conduit 2 through which the molten metal is discharged. The first portion 8 is each formed by an intermediate section of the conduit 2 which is a cross section through which the molten metal is supplied from the first portion 8 and also a cross section through which the molten metal is supplied into the second portion 9. It extends longitudinally to the second end 11 in a predetermined length.

The edges 5 formed by the paired walls 3, 4 are internally rounded along the entire length of the conduit 2; The radius of curvature of the edge 5 gradually changes along the first portion 8 and continues to decrease from the maximum value R ₁ of the end 7 to the minimum value R ₂ of the opposite end 11, and the second portion Maintain a constant value R ₂ along the entire length of (9); The selected minimum value R ₂ of the radius of curvature of the edge 5 is the optimum value for continuously rolling the metal discharged from the cast conduit 2.

The radius of curvature of the edge 5 gradually changes along the first part 8, correspondingly to the cross-sectional view of the part 8. More specifically, the change in cross section is obtained by each funnel-shaped portion 12 of the four edges 5 of the portion 8; Four funnel-shaped portions 12 project laterally past the walls 3, 4 and extend longitudinally from the end 7 of the portion 8 to the end 11 and end of the portion 8. Tapered towards (11), so that it is formed by a pair of parallel walls 3, 4, but as described above it changes in the longitudinal axis and decreases in area from the end 7 to the end 11 as described above. Has

The end 11 of the part 8 has a rectangular cross section without protrusions and coincides with a constant cross section of the second part 9.

The cross-sectional change of the first part 8 is for regenerating the heat shrink of the metal as it is supplied and cooled along the part 8. To this end, in a preferred embodiment of the present invention, the cross-sectional change of the first portion 8 and the corresponding change of the radius of curvature of the inner edge 5 are not linear changes.

Further, the longitudinal extension of the variable-section first portion 8 is preferably approximately equal to the extension of the constant-section second portion 9. In a preferred embodiment, the longitudinal extension of the first part 8 is, for example, 95% or less of the longitudinal extension of the second part 9.

In a general embodiment, as a non-limiting example, the lengths of the first part 8 and the second part 9 are L ₁ = 450 mm and L ₂ = 600 mm, respectively; This length is measured along an axis parallel to the flat wall 3 (as opposed to the longitudinal axis of the conduit 2, which can be curved as shown in FIG. 1), as in the other distances described below.

As such, the radius of curvature of the edge 5 at the molten metal input end 7 is R ₁ = 11 mm; From the end 7 of the intermediate section 13 of the part 8 (see FIG. 1) to the distance L ₃ = 240 mm (also measured along an axis parallel to the flat wall 30), the radius of curvature is at a median of 10.4 mm. Suppose; At the end 11 of the part 8 (ie the distance L ₁ = 450 mm from the end 7 or the distance L ₄ = 210 mm from the intermediate section 13), the radius of curvature is equal to the minimum value R ₂ = 10 mm, This is maintained up to the output end 10 of the conduit 2 along the entire length of the second part 9. Thus, the ratio between the change in radius of curvature and the distance from the molten metal input end 7 of the part 8 is not constant along the part 8 but decreases along the distance from the end 7: in the example shown. In this case, the intermediate section 13 divides the part 8 into first and second parts 14 and 15 of different lengths, the ratio being approximately 0.0025 along the part 14 having a length L ₃ = 240 mm. (Where the radius of curvature is reduced from 11 mm to 10.4 mm) and approximately 0.002 (where the radius of curvature is further reduced from 10.4 mm to 10 mm) along the portion 15 having a length L ₄ = 210 mm.

In this exemplary embodiment, the change in the radius of curvature of the edge 5 is in contrast to the linear function of the distance from the molten metal input 7 of the conduit 2 when the molten metal is cooled. It is clear that the cross-sectional change of is reproducible (thus a function of the heat shrinkage of the metal).

It is clear that the size of the paired walls 3, 4 can be chosen to obtain a finished product of the desired size. In particular, in order to form square-section steel pieces, the ratio between the width of the flat wall 3 and the width of the curved wall 4 is preferably 1: 1.01.

However, it is obvious that the ingot mold as described above can be variously changed without departing from the spirit of the appended claims.

The ingot mold of the present invention effectively cools the molten metal to prevent the metal from separating from the walls, i.

Claims (11)

Longitudinal longitudinally shaped cast conduits 2 through which molten metal is cooled, wherein the cast conduits 2 have a substantially rectangular cross-section and are paired substantially parallel in parallel to the first walls 3 and second. Formed by the wall 4, wherein the paired first wall 3 and the second wall 4 are substantially perpendicular to each other and form four inner edges 5; In continuous casting, in particular ingot molds for forming slabs having a rectangular or square cross section, The cast conduit 2 comprises at least a first portion 8 having a rounded inner edge 5 and an inner cross-section that gradually changes from each longitudinal first end 7, wherein the melt is formed at the first end. Metal is supplied toward each longitudinal second end 11 opposite the first end; The change in the cross section of the at least first portion (8) is determined by a continuous and corresponding corresponding change in the radius of curvature of the rounded inner edge (5); The radius of curvature is continuous casting ingot mold of the molten metal characterized in that the reduction to a minimum value (R ₂₎ of said second end (11) from the maximum value (R ₁₎ of said first end (7). The molten metal according to claim 1, wherein the change in the cross section of the at least first portion (8) of the cast conduit (2) is partially solidified when the molten metal passes through the at least first portion (8) and partially solidifies. Ingot mold for continuous casting of molten metal, characterized by regenerating the thermal contraction of. 3. The change according to claim 1, wherein the change in the cross section of the at least first portion 8 and the corresponding change in the radius of curvature of the rounded inner edge 5 are defined in the at least first portion 8. Ingot mold for continuous casting of molten metal, characterized in that it is a nonlinear function of the distance from the first end (7). 4. The pair according to claim 1, wherein the change of the cross section of the at least first portion is provided with the at least first portion 8 and protrudes transversely. Obtained by four funnel-shaped portions 12 located at the four edges 5 formed by the walls 3, 4; The funnel-shaped portion 12 extends transversely about 1/10 of the width of the walls 3, 4, from the first end 7 to the second of the at least first portion 8. Extend longitudinally to the end 11; The funnel-shaped portion 12 is tapered towards the second end 11 with the at least first portion 8 having a substantially rectangular cross section without protrusions, ingot mold for continuous casting of molten metal. . 5. The melt according to claim 1, wherein the minimum value R ₂ of the radius of curvature is an optimum value for the subsequent rolling of the solidified metal discharged from the cast conduit 2. 6. Ingot mold for continuous casting of metal. The method according to any one of claims 3, 4 and 5, wherein the change in the radius of curvature of the edge 5 between the two predetermined cross sections of the at least first portion 8 and the predetermined cross section. The at least first portion along the first portion 14 of the at least first portion 8 being approximately 0.0025 along the distance between the first and second portions in a direction in which the molten metal flows in the cast conduit 2. Approximately 0.002 along second portion 15 of (8); The ingot mold for continuous casting of molten metal, characterized in that the second portion (15) has a longitudinal extension that is approximately 12% shorter than the longitudinal extension of the first portion (14). The cast conduit (2) according to any one of the preceding claims, wherein the cast conduit (2) has a substantially rectangular inner cross-section of a constant area, with each right-extending extension of the paired walls (3, 4). A second portion 9 formed; The second portion (9) is connected to the at least first portion (8) and has a molten metal input cross section (11) coinciding with the molten metal output cross section of the at least first portion (8); The second portion 9 is characterized in that the radius of curvature is constant along the entire longitudinal extension of the second portion 9 and also has a rounded inner edge 5 equal to the minimum value of the radius of curvature R ₂ . Ingot mold for continuous casting of molten metal. 8. The ingot mold for continuous casting of molten metal as claimed in claim 7, wherein said at least first portion (8) has a longitudinal axis extension substantially equal to the longitudinal axis extension of said second portion (9). 9. The ingot mold for continuous casting of molten metal as claimed in claim 8, wherein said at least first portion (8) has a longitudinal extension in shorter than the longitudinal extension of said second portion (9). 10. The casting conduit (2) according to any one of the preceding claims, wherein the cast conduit (2) is curved; The first walls 3 in pairs that are substantially parallel next to each other are flat; The ingot mold for continuous casting of molten metal, characterized in that the second walls (4) in pairs standing substantially parallel side by side have a predetermined bend. The melting according to claim 10, wherein the ratio between the width of the flat wall of the paired first wall 3 and the width of the curved wall of the paired second wall is 1: 1.01. Ingot mold for continuous casting of metal.