ES2671472T3 - Crystallizer for continuous casting and production method - Google Patents

Abstract

Crystallizer for continuous casting comprising at least one wall (11) provided, on its external surface during use (15), with a plurality of grooves (16) each of which opens outwards and has an extension mainly longitudinal, a longitudinal metal bar (18) is inserted into each of said grooves (16) and extends in at least a part of the length of the respective groove (16), which closes said groove (16) towards the outside and that defines with it a channel (19) for the passage of a refrigerant fluid, characterized in that said longitudinal metal bars (18) are joined to said wall (11) of the crystallizer by welding them on at least part of the internal edges of said grooves (16).

Description

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DESCRIPTION

Crystallizer for continuous casting and method for its production Field of the invention

The present invention relates to a crystallizer for continuous casting provided with a plurality of channels made in its walls and through which a cooling liquid is passed.

In particular, the crystallizer can be used in the field of steel manufacturing for casting metal products of any type and section, such as billets or plugs, preferably with a square or rectangular section, but also polygonal in general, such as roughing for beams , or round. However, applications of the crystallizer for casting thin, medium or thick plates are not excluded.

The crystallizer to which the present invention is applied can be of the tubular type or of the plate type.

Background of the invention

Crystallizers are known for casting billets or plugs, which have a tubular body in which the liquid metal is cooled. It is also known to provide the tubular body, in the thickness of its walls and in at least part of its longitudinal extension, with a plurality of channels, of suitable shape and size for the passage of a cooling fluid. The channels can be interconnected with each other to define a closed cooling circuit.

The operations for carrying out the cooling channels in the length of the crystallizer, either tubular or with plates, are particularly complex and uneconomic in terms of time and equipment used. In fact, they require complex drilling and finishing operations to define the passageways that optimize the flow of the cooling fluid. The result is high costs and long times to produce the crystallizer.

Crystallizers are also known which comprise one or more plates defining the casting channel through which the molten metal to be cast is passed.

Solutions are also known in which the plates, on the surface that is external during use, are provided with a plurality of grooves that extend, open outwardly, along the longitudinal extent of the crystallizer.

A known solution provides that a longitudinal bar is associated with each groove to define a channel for the passage of a cooling fluid.

Each longitudinal bar has a height of its cross section that is less than the depth of the groove. Thus, when the longitudinal bar is inserted into the groove, the thickness of the longitudinal bar, together with the bottom wall of the groove, defines a transit section for the cooling fluid.

The longitudinal bars can be attached to the plate either by mechanical interference or by placing another plate on top of the first plate, to contain the longitudinal bars.

These fixing solutions are not only quite complex to obtain, but they are also not very reliable in terms of mechanical and hydraulic joint of the cooling fluid that is passed through the channels.

In addition, the operations to close the grooves are particularly uneconomic in terms of production times and costs.

The refrigerant fluid can reach a pressure of approximately 20 bar, which, in case the longitudinal bars are not correctly attached, can cause leaks.

GB 2055644 A describes a solution in which inserts, made of a plastic material, such as silicone resin or the like, are introduced into a crystallizer plate having open slots to the outside. The function of the inserts, with a shape that matches the shape of the grooves, is to divide the coolant stream, defining a U-shaped channel oriented towards the casting cavity of the molten metal. The plastic insert is closed from the outside by a first metal closure strip and then a metal alloy with low melting point that, once solidified, seals the insert.

The stable position of the plastic insert is guaranteed by the fact that the free edges of the groove made in the plate are deformed above the corresponding edges of the metal strip, generating a partial mechanical interference.

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An aim of the present invention is to simplify and reduce the production times of a crystallizer for continuous casting.

Another purpose of the present invention is to prevent refrigerant fluid leaking through the crystallizer.

Another purpose of the present invention is to improve a method of producing a crystallizer for continuous casting of the type indicated above that is simple and quick to produce, and which allows to reduce the production costs of the crystallizer.

The applicant has devised, tested and carried out the present invention to overcome the deficiencies of the state of the art and to obtain these and other purposes and advantages.

Summary of the invention

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other features of the invention or variants of the main inventive idea.

According to the above purposes, a crystallizer for continuous casting according to the present invention, used for casting molten metal, comprises at least one wall provided, on its surface that is external during use, of a plurality of grooves, each of which is open to the outside and with a mainly longitudinal extension.

By mainly longitudinal extension it is meant that the groove extends in a substantial part, equal to at least 50% of the total crystallizer length.

A longitudinal metal bar is inserted into each of said grooves and extends at least a part of the length of the respective groove, which closes the groove towards the outside and which it defines with it, on the side facing the casting cavity of molten metal, a channel for the passage of a cooling fluid.

According to one aspect of the present invention, the longitudinal metal bars are joined to the crystallizer wall by welding them on at least a part of the internal edges of said grooves.

In particular, a formulation of the invention provides that welding is carried out in correspondence with the outward-facing end portion of the internal edges of each groove.

In another formulation of the invention, each weld is defined by a corresponding weld bead, there are advantageously two weld seams provided opposite, and advantageously of identical length, at each opposite inner edge of each groove.

In a formulation of the invention, the longitudinal bars are made of a metal selected from copper, copper and silver or bronze.

In another formulation of the invention, the longitudinal metal bars are obtained using a lamination or drawing process.

In another formulation of the invention, the welding of the longitudinal metal bars and the corresponding portions of the crystallizer walls is a laser welding.

With the present invention, it is possible to define an intimate and permanent coupling of the wall and the longitudinal bars that guarantees a suitable mechanical resistance, equally distributed throughout the coupling area of the two components, which practically become a single structure.

In other words, thanks to the integration, essentially in a single body, of the longitudinal metal bars with the crystallizer walls, and thanks to the fact that the longitudinal metal bars occupy the entire space of the slots, except the one provided for the passage of the coolant, at the end of the production process, the crystallizer has a degree of stiffness that is essentially comparable to what it had before the grooves were made thereon.

The welding of the wall and the longitudinal bars, in correspondence with the grooves, guarantees the mechanical and hermetic seal of the channels, even when the working pressures to which the cooling fluid is subjected during use are very high.

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The present invention also relates to a method of manufacturing a crystallizer for continuous casting comprising:

- making, at least one wall of a crystallizer, a plurality of grooves each of which opens outwards and has a mainly longitudinal extension, and

- insert in each of the grooves a longitudinal metal bar that extends at least a part of the length of the respective groove, which closes the groove towards the outside and which defines with it a channel for the passage of a cooling fluid.

According to some embodiments of the invention, the method comprises introducing the longitudinal metal bars in a single body with the crystallizer walls by welding the longitudinal metal bars in portions of the internal edges of the grooves.

Brief description of the drawings

These and other features of the present invention will be apparent from the following description of an embodiment, given as a non-restrictive example with reference to the accompanying drawings, in which:

- fig. 1 is a cross-sectional view of a tubular crystallizer according to the present invention, according to a first embodiment;

- fig. 2 is a cross-sectional view of a crystallizer according to the present invention, according to a second embodiment;

- fig. 3 is an application of the invention to a plate type crystallizer, according to a second embodiment;

- fig. 4 is an enlarged view of detail "D" in fig. one;

- fig. 5 is a sectional view of a variant of fig. 3.

To facilitate understanding, the same reference numbers have been used, whenever possible, to identify identical common elements in the drawings. It is understood that the elements and features of one embodiment can be conveniently incorporated into other embodiments without further clarification.

Detailed description of some embodiments

With reference to figs. 1, 2 and 3, crystallizers for continuous casting according to the present invention are described by way of example.

More precisely, figs. 1 and 2 refer to tubular crystallizers for continuous casting of metallic products with a respectively square and round section, while fig. 3 refers to a crystallizer with plates for continuous casting of metallic products with a rectangular section.

In particular, the crystallizers 10 comprise at least one wall 11 defining at least a part of a casting channel 12 through which the molten metal is passed during use.

With reference to fig. 1, the crystallizer 10 is provided with four walls 11 made in a single body together to define a tubular body 13 with a rectangular cross section, in this case square. However, it is not excluded that, in other embodiments, the walls 11 are different components reciprocally connected to each other by suitable connection means and / or are different in number, for example to define the desired sections of the metallic product to be obtained.

With reference to fig. 2, the crystallizer 10 comprises a single wall 11, cylindrical in shape, to define the tubular body 13 with a circular cross-sectional shape.

With reference to fig. 3, the crystallizer 10 is of the type with plates, for the production, for example, of thick, conventional or thin plates, and comprises pairs of at least two walls 11 as shown, arranged opposite each other to define the channel of cast metal casting.

Each wall 11 may be made of copper or its alloys, such as an alloy of copper and silver or an alloy of copper-chromium-zirconium or copper-nickel-beryllium.

Simply by way of a non-restrictive example of the present invention, the wall 11 has a thickness between 15 mm and 35 mm.

According to some embodiments of the present invention, which can be combined with the embodiments described herein, at least one wall 11 of the crystallizer 10 is provided with a surface that is internal during use 14, which defines part of the casting channel 12, and a surface that is external during use 15, opposite to the surface that is internal during use 14.

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Some embodiments provide that the surface that is internal during use 14 of the wall 11 can be coated with a coating layer with the function of increasing wear resistance, and also allowing a low friction slip of molten metal. Simply by way of example, the coating layer is made of a material comprising an alloy of chromium or nickel and chromium.

Each wall 11 is provided, on its surface which is external during use 15, with a plurality of grooves 16, each of which is open towards the outside and has a mainly longitudinal extension. The longitudinal extension of the grooves 16, according to the possible embodiments, substantially coincides with the direction in which, during use, the metallic material is cast.

The grooves 16 are separated from each other by protruding portions 17, each of which defines the side walls of two adjacent grooves 16.

According to the possible embodiments, the grooves 16 may have a cross-sectional shape selected from a group comprising rectangular, circular, polygonal, curved or a combination thereof.

A longitudinal metal bar 18 is inserted into each of the slots 16 and extends in at least a part of the length of the respective slot 16, which closes the slot 16 outwards and defines with it a channel 19 for the passage of a cooling fluid

Simply by way of example, channels 19 can be configured to withstand pressure stresses exerted by the coolant of approximately 20 bar.

According to the possible embodiments, the longitudinal metal bars 18 have a cross-sectional shape and sizes that are at least partially coupled with a part of the cross-section of the grooves 16.

According to possible embodiments, see for example fig. 4, the longitudinal metal bars 18 have a height H of their cross section that is less than the total depth P of the slots 16. This allows defining, between the thickness of the longitudinal metal bar 18 and the bottom of the groove 16, the Useful passage section for cooling fluid in channels 19.

According to the possible embodiments, the longitudinal metal bars 18 may have an essentially rectangular cross-sectional shape, although it is not excluded that in other embodiments it may be different, for example, triangular, polygonal, curved or a combination of the above. .

According to the possible embodiments, the longitudinal metal bars 18 can be inserted into the grooves 16 with interference.

In other embodiments, the longitudinal metal bars 18 can be inserted into the grooves 16 with clearance.

According to the possible formulations of the present invention, the longitudinal metal bars 18 may be made of a material selected from the group comprising copper, copper and silver or bronze.

The longitudinal metal bars 18 can be manufactured by rolling or drawing.

According to the possible embodiments, the longitudinal metal bars 18 are joined to or are an integral part with the walls 11 by welding means in correspondence with the portions of the internal edges of the grooves 16. In this way, the longitudinal metal bars 18 are solidly join the walls 11.

According to a possible embodiment of the present invention, for example, shown in fig. 4, the longitudinal metal bars 18 are connected to the walls 11 by means of welding cords 20 made in correspondence with at least a part of the interface zone between the longitudinal metal bars 18 and the grooves 16.

The weld seams 20 are made in correspondence with the sides or side edges of the grooves 16 and extend from the surface that is external during use 15 inwards. This guarantees the hydraulic joint of the cooling fluid circulating in the channels 19.

According to the possible embodiments, it can be provided that the weld seams 20 are parallel on both opposite side edges of each of the grooves 16; they can also have a depth of weld penetration between 3 mm and 10 mm, preferably between 4 mm and 7 mm, even more preferably between 5 mm and 6 mm.

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In possible implementations of the present invention, the weld seams 20 have a width between 2 mm and 8 mm, preferably between 2 mm and 6 mm, more preferably between 3 mm and 5 mm.

In some embodiments, the weld beads 20 extend over a good portion of the total length of the longitudinal metal bars 18, for example, in a length between 60% and 100% of the total length of the longitudinal metal bars 18.

A preferred embodiment of the present invention provides that the welding beads 20 extend continuously over the entire length of the crystallizer 10, that is, the entire length of the wall 11. In this way it is possible to increase the efficiency of the mechanical and hydraulic joint of the longitudinal metal bars 18.

The longitudinal metal bars 18 become an integral part or single wall body 11. This gives the crystallizer 10 a great mechanical stiffness that can become essentially comparable to that of a crystallizer known as described above, which has holes made directly in the thickness of the crystallizer 10.

The welding operations of the welding cords 20 can be carried out automatically, for example, using numerical control techniques that guarantee precision and production speed. During the welding operations of the welding cords 20, it is possible to use a shielding gas to protect the welding bath, so that it does not come into contact with oxygen and, therefore, oxidation is avoided. Alternatively, welding can be carried out in an environment with controlled atmosphere.

Possible embodiments of the present invention may provide that the wall 11 is preheated before welding. Preheating can take place up to a maximum temperature of approximately 300 ° C, preferably between 150 ° C and 250 ° C. It is quite evident that the intensity of the heating must be such that it does not modify the microcrystalline structure of the materials and their mechanical properties.

The welding cords 20 can be manufactured using one of the welding techniques selected from a group comprising laser or fiber laser welding and electronic lightning welding.

Fiber laser welding can allow wavelengths of less than or equal to 1 pm to be achieved, particularly effective for manufacturing weld seams 20 in copper materials or alloys thereof.

From the experiments carried out, the applicant has observed that it is possible to obtain weld seams 20 with a depth sufficient for the purpose, for example 5 mm, since with somewhat limited powers, for example of the order of 6-10 kW , and therefore relatively economical, the speed of advance is properly established.

Laser welding allows the thermal energy of the welding to be located only in the interface areas between the wall 11 and the longitudinal metal bars 18, limiting the extent of the superheated areas. By properly regulating the power supplied and the focal point of the laser welding beam, it is possible to control the depth or penetration of the weld.

With this welding technique it is possible to achieve high working speeds, for example between 100 mm / s and 200 mm / s, which ensures that the crystallizer 10 can be obtained quickly.

According to a variant described using fig. 4, in correspondence with at least a part of the interface area between the longitudinal metal bars 18 and the grooves 16, that is, in correspondence with the portions of the internal lateral edges of the grooves 16, it is envisaged to apply a welding material strong 24, suitable for making the longitudinal metal bars 18 integral with the sides of the grooves 16.

The brazing material 24 can be applied in at least a certain part of the interface areas between the longitudinal metal bars 18 and the slots 16. In particular, it can be provided that the brazing material 24 is applied in at least one of the external surfaces of the longitudinal metal bars 18 and / or on the lateral sides of at least a part of the grooves 16.

According to possible implementations of the invention, brazing material 24 can be applied using spray techniques.

Once the brazing material 24 has been applied in at least some of the interface zones between the slots 16 and the longitudinal metal bars 18, the latter are inserted in the slots 16 in the position they will assume during normal use.

Subsequently, at least the interface zones between the slots 16 and the longitudinal metal bars 18 are

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they heat to melt the strong solder material 24 and to perform the welding.

According to the possible embodiments, it can be provided that, during the heating stage, the entire wall 11 on which the longitudinal metal bars 18 are provided can be heated. In other embodiments, it can be provided that during the heating stage, the crystallizer 10 is heated.

Some embodiments provide that heating is carried out at a temperature between 200 ° C and 650 ° C. It is quite evident that the intensity of the heating must be such that it does not modify the microcrystalline structure of the materials and their mechanical properties.

For brazing operation, heating can be carried out in a heating oven.

The brazing material 24 can be selected from a group comprising alloys with a base of tin, lead, copper, silver, zinc or combinations thereof.

In possible embodiments, the grooves 16 have an essentially rectangular cross-sectional shape, possibly with rounded upper portions, although other sectional shapes are not excluded.

Simply by way of non-restrictive example of the present invention, if the grooves 16 are rectangular, they can have a width between 5 mm and 12 mm and a depth between 7 mm and 15 mm.

According to other embodiments, for example, described with reference to fig. 3, at least some of the grooves 16, in at least one side wall thereof, have a support shoulder 21 against which the longitudinal metal bar 18 rests during use.

According to a possible embodiment, the support shoulder 21 can protrude with respect to the side walls defining the grooves 16 at a distance S between approximately 0.3 mm and 2 mm, preferably between 0.3 mm and 1 mm, even more preferably between about 0.3 mm and 0.7 mm.

According to the possible solutions, the support shoulder 21 can be made directly when the groove 16 is made, with a single material removal operation.

Simply by way of example, it can be provided that the support shoulder 21 is made by milling using a milling tool having shaped teeth to define the support shoulder 21.

Some embodiments provide that the grooves 16 can be carried out by means of chip removal operations, for example using a multi-tooth milling tool to reduce actuation times.

In particular, the groove 16 is defined by a first portion 22, more internal during use in the thickness of the wall 11, and a second portion 23, wider than the first portion 22, which opens directly outwards and with a shape and size that essentially matches those of the longitudinal metal bar 18.

The limited width of the first portion 22 allows defining the support shoulder 21 on which the longitudinal metal bar 18 rests.

The first portion 22 of the groove 16 defines the usable passage section of the cooling fluid.

The presence of the support shoulder 21 makes it possible to define a support for the precise and uniquely determined placement of the longitudinal metal bars 18. This allows all the longitudinal metal bars 18 to be placed in the same position within the groove 16, ensuring that the channels are obtained. 19 since they all have the same passage section for the cooling fluid.

It is clear that modifications and / or additions of parts can be made to the crystallizer 10 for continuous casting and to the method of manufacturing the crystallizer 10 as described above, without departing from the scope and scope of the present invention.

It is also clear that, while the present invention has been described with reference to some specific examples, one skilled in the art will be able to achieve without doubt many other equivalent forms of crystallizer 10 for continuous casting and the method of manufacturing crystallizer 10, which has the characteristics set forth in the claims and, therefore, all are within the field of protection thus defined.

Claims (12)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 1. Crystallizer for continuous casting comprising at least one wall (11) provided, on its surface that is external during use (15), of a plurality of grooves (16) each of which opens outwards and has a mainly longitudinal extension, a longitudinal metal bar (18) is inserted into each of said slots (16) and extends at least a part of the length of the respective slot (16), which closes said slot (16) towards the exterior and defining with it a channel (19) for the passage of a cooling fluid, characterized in that said longitudinal metal bars (18) are joined with said wall (11) of the crystallizer when welding them on at least a part of the edges internal of said slots (16). 2. Crystallizer according to claim 1, characterized in that welding cords (20) are provided in correspondence with said parts of the internal edges of said grooves (16). 3. Crystallizer according to claim 2, characterized in that said weld seams (20) extend from the surface that is external during use (15) into said wall (11) and are present in pairs on the inner sides oriented of each slot (16). 4. Crystallizer according to claim 2 or 3, characterized in that said weld beads (20) extend at least a part of the total length of said longitudinal bars (18). 5. Crystallizer according to claim 1, characterized in that a strong welding material (24) is provided in correspondence with at least a part of the internal edges of said grooves (16). 6. Crystallizer according to any of the preceding claims, characterized in that, in at least one of its side walls, at least some of said grooves (16) have a support shoulder (21) against which said longitudinal metal bar ( 18) during use. 7. Crystallizer according to any of the preceding claims, characterized in that each of said slots (16) is defined by a first portion (22), which during use is more internal in the thickness of the wall (11), and by a second portion (23) with a width greater than that of the first portion (22), which opens directly to the outside and has a shape and sizes that are essentially coupled with those of said longitudinal metal bar (18). 8. Crystallizer according to any of the preceding claims, characterized in that said longitudinal metal bars (18) have a cross-sectional shape and sizes that are at least partially coupled with part of the cross-section of said grooves (16). 9. Method of manufacturing a crystallizer for continuous casting comprising the manufacture, on at least one wall (11) of a crystallizer (10), a plurality of slots (16) each of which opens outwards and has a mainly longitudinal extension, and the introduction into each of said slots (16) of a longitudinal metal bar (18) that extends essentially at least a part of the length of the respective slot (16), which closes said slot ( 16) towards the outside and defining with it a channel (19) for the passage of a refrigerant fluid, characterized in that it provides that said longitudinal metal bars (18) join with said walls (11) when welding them in correspondence with portions of the internal edges of said grooves (16). A method according to claim 9, characterized in that said integration provides manufacturing of welding cords (20) using one of the welding techniques selected from a group comprising laser welding, fiber laser welding and electronic ray welding. Method according to claim 9, characterized in that said integration envisages applying a strong welding material (24) in at least a part of the internal edges of said grooves (16), and subsequently heating at least interface areas in order of carrying out welding. Method according to any one of claims 9 to 11, characterized in that during the realization of said grooves (16), a support shoulder (21) is made in at least some of said grooves (16), and why during the inserting one of said longitudinal metal bars (18) into one of said grooves (16), said longitudinal metal bar (18) is placed against said support shoulder (21).