KR20030090705A - Method and device for cooling and guiding a beam blank in a curved secondary cooling zone of a beam blank caster - Google Patents

Abstract

The apparatus for cooling and guiding the beam blank 12 in the curved secondary cooling zone 24 of the beam blank caster 10 is interposed with groove means, for example, consisting of a plurality of axially spaced annular grooves 66. And an inner arc web support roller 46 having a cylindrical support surface 64 therein. This groove means overflows behind the inner web support roller 46 by flowing a sufficient amount of coolant in the axial direction under the inner web support roller 46 through the inner channel 42 of the beam blank 12. It is designed to prevent the coolant blockage that generates the. This coolant overflow can cause quenching of the inner surface tips 52 ', 52 "of the flanges 16', 16", which causes lateral cracks of these tips during calibration of the beam blank 12. It can also be seen.

Description

Method and device for cooling and guiding a beam blank in a curved secondary cooling zone of a beam blank caster}

Since the 1960s, the steelmaking industry has continuously cast near-net-shape parts (near-net-shape), forging or casting, in a nearly complete state that does not require a final process such as machining. The production method by processing is well known. The part consists of a web and two flanges and has a cross-sectional shape of a dog bone, which is called a beam blank.

Conventional beam blank casters comprise a continuous casting mold with a subcooled copper mold that forms a steel strand with a solidified skin surrounding the core that remains molten. Solidification of this strand is completed by spray cooling in the secondary cooling zone, where the beam blank is guided along a curved path on the vertical plane, so that the flange of the blank is also vertical. The beam blank is an inner circumferential channel defined between the vertical flanges of the so-called inner arc face (i.e. concave) side of the curved web along this curved path, and the outer arc face of the curved web (i.e. It can be seen that the outer surface channel defined between the vertical flanges of the convex surface) is formed. An extraction and straightening device, located behind the secondary cooling zone, unfolds the curved beam blank and pushes it onto the horizontal emission table.

Apparatus for guiding beam blanks in the curved secondary cooling zone of the beam blank caster typically define a curved path for the beam blank while avoiding bulging of the cell by the internal molten steel ferrostatic pressure. It includes a set of guide and support rollers that cooperate with each other. The plurality of web inner surface support rollers are supported on the inner surface channel on the web inner surface, while the plurality of web outer surface support rollers are supported on the outer surface channel on the web outer surface. In addition, the guide roller is supported on the transverse side and the tip of the flange.

Strand spray cooling in the secondary cooling zone is achieved by a plurality of cooling water spray nozzles. The nozzle here is a standard spray nozzle or a so-called air mist nozzle. These spray nozzles are arranged around the strands to provide mainly coolant (in the form of coolant-air spray particles, respectively) to the perimeter of the bulkiest section of the beam blank, i.e. the flange and web and the inner and outer surface connections between the flanges. It is supposed to spray. Some of the coolant is evaporated in contact with the hot surface of the beam blank. Cooling water that has not evaporated falls off the outer surface, while in the inner surface flows axially through the inner surface channel of the beam blank.

Even when optimizing the cooling and support of the strands in the secondary cooling zones, the beam blank caster has more complex problems due to the dog bone cross-section of the beam blank, which has been the subject of a high cost research program so far in continuous casting technology. It is a well known fact. For example, complex computer programs have been developed to selectively control coolant flow to other areas of the beam blank under the influence of various variables. The arrangement and size of guide rolls are constantly being reconsidered to better support the beam blanks in the continuous casting zone.

Despite these constant efforts to optimize the strand cooling and support conditions of the beam blank casters, some major drawbacks still have not been eliminated. This major drawback is the formation of transverse cracks at the inner surface flange tip, for example when the beam blank is calibrated in the calibration device. This transverse crack is found in particular in beam blanks with a wide cross section and high strength, but not limited to such beam blanks. The disadvantage of lateral splitting is thought to be due to undesirably quenching at the flange tip, but it is not yet possible to reliably avoid these cracks by controlling the choice of cooling water spraying in more diverse ways. Do.

U.S. Patent No. 3,923,093 discloses a continuous casting apparatus having various cross-sectional shapes such as bloom, billet and "dog bone" in various proportions. In this casting apparatus the guide rolls are arranged at stages formed along the path of the metal to be continuously cast. The position of the guide rolls at each end can be adjusted to fit different cross-sectional shapes between the guide rolls. It can be seen that this patent does not contain any teaching in the specification relating to lateral crack prevention at the inner surface flange tip of the beam blank.

The present invention relates to a method and apparatus for cooling and guiding a beam blank in a curved secondary cooling zone of a beam blank caster.

1 is a cross-sectional view along a beam blank with a curved secondary cooling zone;

FIG. 2 is a cross-sectional view of the beam blank in the curved secondary cooling zone of the beam blank caster of FIG. 1, showing an inner surface web support roller; FIG.

Figure 3 is an enlarged detail of the inner surface web support roller of Figure 2;

(Purpose of invention)

It is an object of the present invention to provide a solution which can reliably avoid transverse cracking at the aforementioned inner surface flange tip. According to the invention this solution is an improved method and an improved apparatus for cooling and guiding the beam blank in the curved secondary cooling zone of the beam blank caster respectively as defined in claims 1 and 6 respectively. It is composed by.

(Summary of invention)

Firstly, the present invention provides for the inner surface of the inner surface cooling water to flow over the tip of the flange instead of evaporating axially through the inner surface channel of the beam blank (usually made as large as possible to best support the web) The fact that the web support roller blocks the coolant flow in the inner channel leads to the advantage of finding the supercooled tip of the flange supercooled. In other words, the inner surface tip of the flange is undesirably immersed by the coolant overflow because of the dam effect of the inner surface web support roller. This quenching hardens the inner tip of the flange so that the inner tip of the flange is very susceptible to lateral crack formation during bending beam blank correction. It can be seen that the larger the cross section of the beam blank, the greater the amount of water has to be sprayed on the inner surface connection between the flange and the web, and the more likely the quenching of the flange inner surface tip due to the coolant overflow is observed. . This situation is exacerbated by the fact that as the beam blank portion grows, the web must be better supported, i.e. the web support roller is as large as possible, where the support roller is a nearly perfect dam element in the inner channel of the beam blank. Works.

The present invention also proposes a solution for effectively avoiding the unwanted quenching of the flange inner surface tip by overflow of the cooling water behind the inner surface web support roller designed as large as possible to support the web in the best possible condition. It can also be seen that it has advantages. This solution is designed to allow a sufficient amount of coolant to flow in the axial direction through the inner channel through the inner web support roller under the inner web support roller, thereby preventing a coolant blockage that causes an overflow behind the inner web support roller. It is provided with a cylindrical support surface which comprises a groove means, and thus prevents the quenching of the inner surface tip of the flange by overflow cooling water. An effective side effect of the groove means is to improve the cooling performance of the inner surface web support roller, which of course has a positive effect on the service life.

The groove means consists for example of a plurality of axially spaced annular grooves or helical grooves.

The groove means preferably have a chamfered or curved edge surface as the cloth surface with the cylindrical support surface. This chamfered or curved edge surface prevents surface scratches on the inner web surface of the beam blank when the grooved inner surface web support roller is pressed against the inner surface web surface.

The invention will now be described with reference to the accompanying drawings by way of example.

In FIG. 1 reference numeral 18 denotes a tundish, ie refractory, molten steel distributor, which receives molten steel from a furnace ladle (not shown) into a vertical continuous casting mold 20 in a controlled manner. It is supposed to release. This mold contains a supercooled copper mold (not shown) that forms a beam blank 112 as a steel strand having a solidified outer cell surrounding the core that remains in the molten state. Partially solidified beam blank 12 at the outlet of the copper mold is guided by a foot roller portion 22 to a curved secondary cooling zone 24 where the blank solidification is directed to spray cooling. Is completed by. (It should be noted that the term "spray cooling" herein also includes conventional traditional spray cooling and so-called "air mist cooling".) At the outlet of the secondary cooling zone 24, the beam blank 12 is curved The beam blank 12 is passed through an extraction and calibration device 26 that calibrate before guiding it onto the horizontal emission table 28.

The secondary cooling zone 24 comprises several guide and spray cooling units 30 ₁ , 30 ₂ , 30 ₃ and 30 ₄ . Each of the guide and cooling sections 30 ₁ , 30 ₂ , 30 _3, and 30 ₄ includes a frame 32 that supports a plurality of guide and support rollers 34, 36. These guide and support rollers 34, 36 cooperate with each other to establish a curved path for the beam blank 12 on a vertical plane (ie, the plane of FIG. 1). Another purpose of the guide and support rollers 34 and 36 is to support the solidification cell of the beam blank 12 so as to prevent bulging by iron positive pressure of the internal molten steel.

FIG. 2 shows a cross section along the beam blank 12 in such a guide and cooler 30 ₁ . The curved beam blank 12 has its own vertical flanges 16 ', 16 ", and the curved web 14 of the blank has an inner arc surface 38 (i.e. concave surface) and an outer arc surface 40 (i.e. It should be noted that the curved beam blank 12 is consequently a so-called inner surface channel (< / RTI > defined between the vertical flanges 16 ', 16 " 42 and an outer circumferential channel 44 defined between the vertical flanges 16 ′ and 16 ″ on the outer circumferential surface 40 side of the curved web 14.

Reference numeral 46 denotes an inner surface web support roller supported on the inner surface web surface 38 in the inner surface channel 42. The outer surface web support roller 48 supported on the outer surface web surface 40 in the outer surface channel 44 is schematically shown in dashed lines in FIG. 2. In addition to the inner and outer web support rollers 40, some or all of the guide and spray cooling sections 30 ₁ to 30 ₄ are positioned on the inner surface tips 52 'and 52 "of the flanges 16' and 16". Surface flange support rollers 50 ', 50 "supported on the outer surface flange support rollers 54', 54" supported on the outer surface tips 56 ', 56 "of the flanges 16', 16". And transverse guide rollers 58 ', 58 "supported on the transverse outer surfaces 60', 60" of the flanges 16 ', 16 ".

Spray cooling of the beam blank 12 in the secondary cooling zone 24 is accomplished by a plurality of cooling water spray nozzles 62 (or spray ramps). The spray nozzles 62 are arranged over the entire length of the secondary cooling zone 24 around the beam blank 12 so that the circumferential surface of the largest portion of the beam blank 12, i.e., the flanges 16 ', 16 "and It is intended to spray primarily cooling water or air mist on the inner and outer surface connections between the web 14 and the transverse outer surfaces 60 'and 60 "of the flanges 16' and 16". It should be noted that the term "nozzle" is used to encompass not only standard spray nozzles but also so-called "air mist nozzles" which form air-water mists.) The portion of the coolant sprayed onto the beam blank 12 The vaporized water comes into contact with the hot surface, while the non-evaporated cooling water falls off the outer surface, while in the inner surface it enters the inner surface channel 42 of the beam blank 12.

According to an important feature of the invention, the inner-surface web support roller 46 comprises a cylindrical support surface (denoted entirely by reference numeral 64) in which the annular groove 66 is regularly sandwiched. These axially spaced grooves 66 are designed as groove means for flowing a sufficient amount of coolant through the channel between the rotating inner surface web support roller 46 and the inner surface 38 of the web 14. The cooling water behind the web support roller 46 is prevented from excessive blockage. Another advantage of the present invention is that in the beam blank caster according to the prior art, the inner surface tips 52 ', 52 "of the flanges 16', 16" are often as large as possible to support the web 14 in the best possible condition. Coolant in inner channel channel 42 such that inner surface web support roller 46 to be produced flows over the inner surface tip 52 ', 52 "of flange 16', 16" over a major portion of inner surface coolant. The fact that it blocks the flow makes it possible to find it unnecessarily quenched. This undesired quenching phenomenon hardens the inner surface tips 52 ', 52 "of the flanges 16', 16", so that the tips correct the bent beam blank 12 in the extraction and straightening device 26. During this time, they become very sensitive to the formation of transverse cracks. In conclusion, an overflow occurs that prevents an excessive amount of coolant behind the inner web support roller 46 and thus quenches over the inner surface tips 52 ', 52 "of the beam blank 12. By designing the axially spaced grooves 66 to prevent them from being formed, transverse cracks are generated in the inner surface tips 52 ', 52 "of the flanges 16', 16" during calibration of the beam blank 12. The side effect of the grooves 66 in the inner surface web support roller 46 is to improve the cooling performance of the inner surface web support roller 46, which of course has a positive effect on the life of the support roller itself. I can see that.

As shown in the enlarged detail view of FIG. 3, the annular groove 66 is a two-sided sidewall 68 ′ and 68 ″ as the fabric surface between the side walls 68 ′ and 68 ″ and the cylindrical support surface 64. It has two chamfered and curved annular edges 70 ', 70 ". These chamfered and curved cloth backings 70', 70" have an inner surface web surface 38 of the beam blank 12. Helps to avoid surface scratches.

Referring again to Figure 2, it should be noted that the inner surface web support rollers 46 are also at their ends being chamfered edges 72 ', 72 ". These chamfered edges 72', 72 &Quot;) over the entire width without fear of causing surface flaws on the curved web-flange connections 76 ', 76 " when the beam blank 12 or web support roller 46 is forced to move in the lateral direction. It can be seen that it is possible to operate with the web support roller 46 in contact with the flat central portion of the web surface 38.

The dimensions of the channeled coolant flow groove 66 will be determined by the coolant flow that must flow through the channel between the rotating inner surface web support roller 46 and the inner surface 38 of the web 14. Excessive amount of coolant behind the surface web support roller 46 is blocked. Typical groove dimensions are, for example, as follows: width 10-20 mm, depth 3-12 mm. The width of the annular cylindrical support surface 64 present between two consecutive grooves 66 is usually in the range of 10-20 mm. This annular cylindrical support surface 64 can, however, be wider if the number of grooves required to prevent coolant overflow causing quenching is small.

Claims (9)

In order to define a curved path for the beam blank 12, it is supported on the inner surface web surface 38 in the inner surface channel 42 and at least one extends the web over substantially the entire width of the inner surface web surface 38. The web (with the aid of an inner surface web support roller 46 having a guiding cylindrical support surface 64 and an outer surface web support roller 48 supported on the outer surface web surface 40 in the outer surface channel 44) 14) guiding; Spraying coolant onto the beam blank (12); And two transverse flanges defining the web 14 having the inner surface 38 and the outer surface 40, and defining the inner surface channel 42 and the outer surface channel 44. In the method of cooling and guiding the beam blank 12 consisting of 16 ', 16 "in the curved secondary cooling zone 24 of the beam blank caster 10, Overflow is provided behind the at least one inner surface web support roller 46 by flowing a sufficient amount of coolant in the axial direction under the at least one inner surface web support roller 46 through the inner surface channel 42. And groove means designed to prevent the resulting coolant blockage. According to claim 1, Wherein said groove means in said cylindrical support surface (64) has a chamfered or curved edge surface (70 ', 70 ") as a cloth surface to said cylindrical support surface (64). The method according to claim 1 or 2, Said groove means comprising a helical groove in said cylindrical support surface (64). The method according to claim 1 or 2, Said groove means comprising a plurality of axially spaced annular grooves (66) in said cylindrical support surface (64). Spraying means for spraying cooling water onto the beam blank (12); At least one having a cylindrical support surface 64 supported on the inner surface web surface 38 in the inner surface channel 42 and guiding the web over substantially the entire width of the inner surface surface 38. Inner surface web support roller 46; And An outer surface web support roller (48) supported on the outer surface web surface (40) in the outer surface channel (44); The inner surface web support roller 46 and the outer surface web support roller 48 cooperate with each other to define a curved path for the beam blank 12, Two transverse flanges 16 ', 16 defining the web 14 having the inner surface 38 and the outer surface 40, and the inner surface channel 42 and the outer surface channel 44; In the apparatus for cooling and guiding the beam blank (12) consisting of ") in the curved secondary cooling zone (24) of the beam blank caster (10), The cylindrical support surface 64 of the at least one inner surface web support roller 46 allows a sufficient amount of coolant to flow in the axial direction through the inner surface channel 42 under the inner surface web support roller 46. And groove means designed to prevent a blockage of the coolant which causes an overflow behind said inner surface web support roller (46). The method of claim 5, And said groove means in said cylindrical support surface (64) having a chamfered or curved edge surface (70 ', 70 ") as a back surface to said cylindrical support surface (64). The method according to claim 5 or 6, The groove means comprising a helical groove in the cylindrical support surface (64). The method according to claim 5 or 6, Said groove means comprising a plurality of axially spaced annular grooves (66) in said cylindrical support surface (64). The method according to any one of claims 5 to 8, And the inner arc web support roller (46) is chamfered at both ends of the edge surface (72 ', 72 ").