KR100707785B1 - Method and device for manufacturing continuous cast products - Google Patents

Abstract

The continuous casting operation uses a soft reduction action on the molten core of the cast material. The shaping section u only a pair of rollers (23) with the pull forces (Z) on the cast material as the control value. The comparison between nominal a actual values is used to set the ratio between the position of the paired rollers (23) and the peak (S) of the soft zone, so tha the cast strand is hardened throughout directly in the roller gap between the two rollers (24,25).

Description

METHOD AND DEVICE FOR MANUFACTURING CONTINUOUS CAST PRODUCTS}

1 is a view of a first embodiment of an apparatus according to the invention with roller pairs fixedly arranged along a cast strand conveying passage;

Figure 2 shows a variant of the device according to figure 1 with a fixedly arranged second roller pair which can optionally be operated;

3 is a view of a second embodiment of the device according to the invention with a pair of rollers which can be moved along the cast strand conveying passage and arranged on top of the calibration section;

4 shows a variant of the device according to FIG. 3 with roller pairs movable along a cast strand conveying passage arranged in the lower part of the calibration section;

5 is a schematic view of the method according to the invention in combination with a drive roller pair;

6 is a side view of a device with a roller pair and a drive roller pair;

7 is a cross-sectional view taken along the dividing line A-A of the device according to FIG. 6;

8 is a cross-sectional view taken along the dividing line B-B of the device according to FIG. 6;

9 is a cross-sectional view of a device with a track; And

10A and 10B are schematic views of roller pairs with two different roller diameters.

The present invention provides a procedure in which the liquid core of the casting is transformed by the continuous casting manufacturing method. The present invention also relates to a method of guiding and supporting a mold, a strand removed by a continuous casting device in a curved form, and a method of aligning and moving along a casting strand feed passage to reduce deformation of the casting. This method of reducing deformation is known as the concept of soft reduction.

During continuous casting, the continuously cast strand solidifies on the layer of strand solidification formed in the mold, which solidifies in the direction of strand center during detachment. At this time, the alloy component is accumulated on the solidified front surface. This accumulation results in central segregation in the fully solidified strand, which results in heterogeneity and imbalance in the strand cross section.

An electronic whisk is known as a way to influence the solidification process, which imposes a flow motion on the melt. Stirring in the second cooling stage or the last stage of the continuous casting unit produces a bead-shaped solidified structure and reduces segregation of the core.

Another way to prevent segregation on the solidification front and increase core density is soft reduction. Strands that have not yet solidified yet, and thus the method of rolling the core part which is still liquid. EP 0 603 330 B1 discloses a process for deforming a liquid core part of a casting product and forming a steel plate with continuous casting and a method of forming a block. This transformation takes place in the cast-strand transfer passage between the point where the area is not yet completely solidified and the product is completely solidified, where the concentration of solid particles in the liquid core is 10% and 80%, respectively. do. For this purpose a device is recommended which covers the inner and outer segments of the curved roller table section. Segments inside the curve are more fluid than segments outside. There is an additional roller in the roller cage perpendicular to the roller of the segment, which is likewise compressed in the direction of the casting axis.

Furthermore, longer, thinner liquid cores that regulate themselves lead to more porosity and segregation. This is limited in using the advantages of high speed casting due to deterioration in quality.

An object of the present invention is an apparatus and method for producing strand products having uniform properties across strand cross sections by preventing segregation and at the same time increasing the density of the core portion. This method and apparatus can be applied, in particular, to high speed foundry facilities and to facilities with molds to the final standard. This problem is solved by the method and apparatus characterized by the features of claim 1. More preferred embodiments are disclosed in the claims that follow.

The basic idea of the invention is that a pair of rollers that cause deformation so that the liquid core tip is always in the roller gap causing deformation, that is, the strand lies along the casting strand conveying passage so that the strands are completely solidified during the deformation phase in the space between the two rollers. It is a control method using a strand feed force as a control value for adjusting the position of the liquid core tip with respect to the position of and the position of the roller clearance. Strand feed force is a value that depends on the given roller adjustment force, deformation thickness and material intrinsic value. The set value is the strand feed force when the liquid core tip is in the roller clearance. When the actual value deviates from the set value, the relative position between the liquid core tip and the roller clearance can be adjusted by changing the casting speed in the first embodiment and by changing the roller pair position relative to the strand in the second embodiment. In the third embodiment, the relative position between the liquid core tip and the roller clearance can be adjusted through the parameters of the casting speed and the mobility of the roller pair lying along the casting strand feed passage. As a whole, the change of the solidification position caused by, for example, a change in the casting temperature through heating or a change in the solid state temperature by fine adjustment of the alloy can be detected and automatically corrected by the control method.

For the device, it is proposed to make the diameter of the rollers between 400 and 1,800 mm. By selecting the diameter of the roller larger than the normal diameter of the drive roller, the optimum soft reduction can be achieved by the relatively gentle contact angle and the compressed length, and the change of the conveying force can be reliably detected.

The gentle contact angle and the compressed length can at the same time compensate for the volume reduction upon final solidification due to the movement of the still liquid core to the rear when a large volume moves backward. This advantage is not achieved in a soft reduction system having multiple roller pairs according to the prior art. In addition, in known multiple roller systems it is not possible to rule out that final solidification takes place between two adjacent roller pairs, with the same effect as normal final solidification without soft reduction.

For the device, the thickness of the cast strand can be greatly reduced by only one roller pair by selecting a roller of large diameter. This thickness reduction can be reduced to 12-15 mm without causing internal damage to the strand in the actual operating area. The extension of the cast strand at the solidification front is reduced through soft reduction adjustment. The roller diameter determines the degree of sharpness of the soft reduction zone and the resulting extension limits and compression.

The drive roller pair is provided below the deformation roller pair below the strand, and the strand feed force is determined from the torque of the drive roller pair.

Other details and advantages of the present invention are described below.

(Example)

1 to 4 show different arrangements of the first and second embodiments of the device according to the invention. In FIG. 1, the continuous casting apparatus 1 which has the mold 2 and the curved casting strand conveyance path 3 is shown in simplified form. The cast strand conveying passage 3 typically consists of a cooling section 4 and an elongate and straightening section 5 arranged adjacent to the lower part of the cooling section 4. According to the invention the soft reduction process is not by means of multiple roller pairs or roller cages but by roller pairs 6 consisting of upper and lower rollers 7, 8 arranged in a fixed manner. In the lower part of the strands, a pair of driving rollers for calibration is arranged as upper and lower driving rollers 10 and 11 after the roller pair 6 for reduction. Each roller device 12, 13 is shown very briefly.

In Fig. 2, corresponding components are designated by the same reference numerals. Along with the first roller pair 6 and the drive roller pair 9, the second roller pair 14 and the corresponding drive roller pair 15 are arranged along the cast strand conveying passage and the first set of roller pairs 6, 9. ) In front of it. The change in casting speed controls the formation of the liquid core tip in the casting strand, thereby allowing complete solidification at all times in the gaps between the pair of rollers to compress the optimal core and avoid center segregation. In the second roller pair, optionally the first or second roller pair performs soft reduction of the liquid core tip. At this time, the pair of lower rollers 20 are selectively present.

A second embodiment of the present invention is described with reference to FIGS. 3 and 4. Here, it is with respect to the roller pair 16 which can move along the address strand conveyance path with the corresponding drive roller pair 17. This position change is explained by the roller pairs 16 ', 17'. Behind the roller pair 16 at the bottom of the strand is a straightening portion 18 consisting of two drive roller pairs 19 and 20.

4 shows an implementation form with a movable roller pair 21 arranged behind the corrector 18. This movement path is controlled according to the strand feed force according to the invention. This furnace is likewise dependent on the casting speed. When the casting speed is low, it is possible to use a small moving path (Fig. 3), and when the casting speed is large, the moving path should be larger (Fig. 4).

5 schematically shows a control method combined with a drive roller pair 22. The roller pair 23 is disposed on the cast strand product with an initial thickness D ₁ and a reduced thickness D ₂ . The roller pair is adjusted to lie against the spacer member or to a standard thickness. The lower rollers 24, 25 as well as the upper rollers of the soft reduction rollers can be controlled in relation to the adjustment force P and the moving path thereof (the control device is schematically shown by reference numeral 26). The force Z required to transfer the strand is defined by the adjustment force P, the thickness difference and the material intrinsic value, and is calculated as the torque M _d necessary for the rollers 27 and 28 of the drive roller 22. At this time, the set value is a transfer force generated when the liquid core tip S to the solidification end portion are present in the gap between the rollers 24 and 25. When a difference occurs between the actual value and the set value, the positional relationship between the roller pair and the liquid core tip is corrected by changing the casting speed or changing the position of the roller pair 23.

6 shows the configuration of the soft reduction apparatus from the side. The soft reduction and drive roller pairs 23 and 22 are arranged in the common frame structure 29. The movement path and the adjustment of the force are made by the two hydraulic cylinders 32 and 33 acting on the roller rotation shafts 30 and 31, which are clearly shown in the A-A cross section of FIG. 34 denotes a compression core portion between both rollers 24 and 25.

FIG. 8 shows a cross-sectional view taken along line BB of FIG. 6. The adjustment of both drive roller pairs 27 and 28 is made via hydraulic cylinders 36 and 37. The rollers 27 and 28 are provided with drives 38 and 39, respectively, and the drive torque M _d of this drive is used as the actual magnitude for the strand feed force Z. According to the second embodiment, the frame structure 29 having the soft reduction roller pair 23 and the drive roller pair 22 can move along the cast strand conveying passage. It can move along the cast strand conveying passage according to FIG. 9. This can be achieved by means of FIG. 9, in particular via drive wheels 40, 41 arranged on both sides of the frame structure 29. The driving wheels are connected to the frame structure in the tracks 42 and 43 along the casting strand conveying path.

Depicting rollers 400 mm in diameter and rollers 1,500 mm through FIGS. 10A and 10B enables controlled core compression with the aid of relatively large rollers.

According to the formula I _d = (d / 2 * Δh), where I _d = length of compression, d = diameter, Δh = thickness reduction, the length of compression becomes longer for the same Δh and increasing d and the contact angle over this length of compression It is clear that (α) becomes smaller. The longer the compression length and the smaller the contact angle, the smoother the contact angle becomes, the smaller the extension of the solidification front of the strand core and the longer the reduction section. This works advantageously for core compression. Satisfactory core density is possible with rollers of 400 to 1,800 mm in diameter.

By the method and apparatus of the above structure, a steel plate and a lump can be subjected to a soft reduction process. In particular, profiled rectangular, square or round cast strands can be compressed in the core portion. The device can be installed in a new installation and at the same time an additional installation in an existing installation.

Claims (9)

Casting the casting strand of steel having a liquid core by continuous casting when leaving the casting die, The casting core is guided through the deformation gap of the deformation roller pair to deform the liquid core of the casting strand, and is defined by the set adjustment force (P) of the deformation roller pair 23, the deformation thickness of the casting strand (ΔD), and the material intrinsic value. Determining the strand feed force Z as the actual value, Comparing the actual value with the set value defined as the strand feed force when the liquid core tip S is accurately positioned in the deformation gap, and And adjusting the relative position between the liquid core tip and the strain gap so that complete solidification occurs within the strain gap, based on the difference between the actual value and the set value. The method of claim 1, wherein the position of the liquid core tip (S) is adjusted according to the casting speed. The method of claim 1, wherein the position of the strain roller pairs (23) is adjusted by moving the strain roller pairs in the longitudinal direction of the cast strand. delete delete delete delete delete delete

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