JPS6210744B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a horizontal continuous casting method.

In conventional horizontal continuous casting equipment, as molten metal from a tundish nozzle flows through a water-cooled mold, the molten metal contacts the inner surface of the mold and is cooled. However, in the mold, the static pressure on the surface layer of the molten metal, which depends on the level of the molten metal in the tundish, differs along the circumferential direction of the mold. That is, the static pressure is small in the upper part of the molten metal, and becomes larger as it goes downward. Therefore, the contact pressure between the surface layer of the molten metal and the inner surface of the mold becomes non-uniform along the circumferential direction of the mold. If the contact pressure is uneven in this way, the molten metal will be cooled unevenly along the circumference inside the mold, and the thermal stress caused by the uneven cooling will cause deformation and vertical cracking of the steel ingot. or the coagulation shell ruptures, resulting in a so-called breakout. Furthermore, since the contact pressure increases as the lower part approaches, uneven wear occurs such that the lower the inner surface of the mold, the greater the amount of wear. Further, when a lubricant is supplied between the inner surface of the mold and the molten metal, the amount of the lubricant supplied becomes unbalanced along the circumferential direction due to the non-uniformity of the contact pressure. Therefore, the lubrication between the outer surface of the molten metal and the inner surface of the mold becomes uneven, leading to destruction of the solidified shell.

The molten metal inside the mold is cooled non-uniformly due to the non-uniformity of the static pressure as described above, and also due to the gap created between it and the inner surface of the mold after the solidification shell is formed. may be done. That is, by contacting the inner surface of the mold and being cooled, the surface layer of the molten metal contracts and forms a solidified shell, but the contraction creates a gap between the surface layer of the molten metal and the inner surface of the mold. However, since the molten metal is displaced downward by its gravity, the gap becomes larger in the upper part of the mold, and the lower part of the molten metal contacts the inner surface of the mold with a large contact pressure. Such non-uniform contact pressure also causes non-uniform cooling of the molten metal.

Some prior art is disclosed in Japanese Patent Application Laid-open No. 53-76130. In this prior art, an electrode is immersed in the molten metal in the tundish, and a direct current is passed through the molten metal to generate a magnetic field perpendicular to and horizontally to the longitudinal direction of the slab within the mold. Gravity compensation is being performed on the slab. In such prior art, it is not possible to make the contact pressure of the molten metal in the mold uniform with the inner circumferential surface of the mold in the circumferential direction. Furthermore, maintenance of the electrodes is troublesome.

An object of the present invention is to provide a horizontal continuous casting method in which the contact pressure between the inner surface of the mold and the outer surface of molten metal is made substantially uniform along the circumferential direction.

In the present invention, a coil is arranged around the outer periphery of a mold tube so that its displacement can be adjusted up and down, this coil is excited with AC power, the thickness of the solidified shell of the cast body is measured, and the thickness of the measured solidified shell is measured. The present invention adjusts the vertical displacement of the coil according to the thickness, and the present invention allows the molten metal in the mold tube to
The electromagnetic force has a distribution corresponding to the distribution of static pressure acting on the surface layer of the molten metal and is applied in the opposite direction to the acting direction of the static pressure, so that sufficient force is applied to the inner surface of the mold tube at the upper part of the molten metal. This is a horizontal continuous casting method characterized by applying contact pressure and making the contact pressure uniform along the circumferential direction of the mold.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall system diagram of an embodiment of the present invention. In this horizontal continuous casting equipment, a tundish 1 is provided with a heating device 2 for stabilizing the temperature of molten steel within the tundish 1. The cast body 4 from the mold 3 is pulled out from the cooling zone 5 by a pulling device 6 in the direction of arrow 8 and cut by a cutting device 7 to obtain an ingot 9. This ingot 9 is conveyed by a roller table 10.

FIG. 2 is an enlarged sectional view of the vicinity of the mold 3,
FIG. 3 is a sectional view taken along the section line - in FIG. 2. The tundish 1 is lined with a refractory material 11 and stores molten metal 12 therein. A tundish nozzle 14 made of a refractory material is fixedly provided at the lower part of the tundish 1. The mold 3 includes a cylindrical copper mold tube 15 forming a passage 16 concentrically continuous with the tundish nozzle 14 . An outward flange 17 is integrally provided at one end in the axial direction of the mold tube 15, and by fixing the outward flange 17 to the tundish 1 with a mounting hardware 18, the mold tube 15 and the tundish nozzle 14 are fixed. are fixedly connected.

An outward flange 19 is fitted into the other end of the mold tube 15 through a seal member 20 in a fluid-tight manner. A cylindrical frame 21 that surrounds the mold tube 15 and extends toward one end in the axial direction is fixed to this outward flange 19, and an outward flange 22 is integrally attached to the end of this frame 21. provided. In addition, the mounting hardware 18 includes
A cylindrical frame 23 that surrounds the mold tube 15 and extends toward the other end in the axial direction and is concentric with and has the same diameter as the frame 21 is fixed. An outward flange 24 facing the flange 22 is integrally provided at the end of the frame 23 .
Both flanges 22 and 24 are connected to the bolt 27 with an outward facing collar 26 provided integrally with the storage box 25 interposed therebetween.
and are connected by a nut 28. Furthermore, ring-shaped seal members 29 and 30 are interposed between both flanges 22 and 24 and both surfaces of the outward facing collar 26, thereby forming a cooling liquid passage 31 surrounding the mold tube 15. A liquid supply pipe 32 for supplying cooling liquid, such as cooling water, is connected to one frame 21, and the other frame 23
A drain pipe 33 for draining cooling water is connected to.

A storage box 25 made of a non-magnetic steel plate such as austenitic stainless steel is provided in the coolant passage 31 to house the electromagnetic field generating means 34 . This storage box 25 is provided integrally with an inner cylindrical portion 36 that surrounds the mold tube 15 by forming an annular gap 35 between it and the outer surface of the mold tube 15, and at both ends of the inner cylindrical portion 36 in the axial direction. end plate portions 37 and 38 extending outward in the radial direction; and an outer cylinder portion 39 having both axial ends fixedly connected to the end plate portions 37 and 38, respectively, and surrounding the inner cylinder portion 36. . A storage space 40 that is liquid-tightly sealed from the cooling liquid passage 31 is formed in the storage box 25, and a dry gas or a cooling liquid having an insulating effect is sealed or circulated within this storage space 40.

The electromagnetic field generating means 34 includes a substantially annular coil 41 that surrounds the mold tube 15 in the storage space 40, and a support frame 4 that supports the coil 41.
2, and is provided so as to be freely displaceable in the vertical direction within the storage box 25. An induced current absorbing plate 34' is provided inside the electromagnetic field generating means 34 to prevent a reverse induced current from flowing when the excitation current decreases.

A guide hole 43 extending vertically is bored at the top of the outward facing collar 26 of the storage box 25 . Further, a pair of guide holes 44 and 45 extending vertically are formed in the lower part of the outward facing collar 26 at symmetrical positions with respect to a vertical plane including the axis of the storage box 25, respectively. Trunnion shafts 46, 47, 48 are respectively fixed to the support frame 42, and these trunnion shafts 46, 47, 48 are inserted into the guide holes 43, 44, 45 so as to be freely displaceable along the axis. A cable lead-in hole 49 is concentrically formed in the trunnion shaft 46, and a cable (not shown) for supplying exciting current to the coil 41 is inserted through the cable lead-in hole 49.

The trunnion shaft 46 has outward flanges 22, 24.
The trunnion shaft 4 protrudes outward between the
An external thread 50 is cut into the outer end of 6 . A disk-shaped rotating member 51 is screwed into this external screw 50. At the top of the frame 23, a support member 52 is provided.
is fixed to the supporting member 52 and the flanges 22 and 24. A receiving seat 53 is provided between the support member 52 and both flanges 22 and 24 to prevent vertical displacement of the rotating member 51 and to allow rotational movement around the trunnion shaft 46. provided.

The pivot member 51 is provided with a lever 54 extending radially outward, to the outer end of which a piston rod 56 of a cylinder 55 is pin-coupled. Therefore, by driving the cylinder 55 to expand and contract, the rotating member 51 moves toward the trunnion shaft 46.
The trunnion shaft 46 moves up and down by rotating around the . That is, the trunnion shaft 46 is prevented from rotating around the axis by the pair of trunnion shafts 47 and 48 at the lower part of the support frame 42, and only vertical movement along the guide hole 43 is permitted.
Since the rotating member 51 is prevented from being displaced in the vertical direction, the trunnion shaft 46 moves up and down in accordance with the rotating movement of the rotating member 51, thereby raising and lowering the electromagnetic field generating means 34 in the storage space 40. do.

FIG. 4 is a diagram showing the static pressure distribution in the surface layer of the molten metal 12 in the mold 3 when the cross-sectional shape is circular. As shown in FIG. 4a, static pressure acts on the surface layer of the molten metal 12, which increases toward the bottom. That is, as shown in FIG. 4b, a static pressure that is inversely proportional to the height acts on the molten metal 12 in the mold 3, so the static pressure shown in FIG. 4b is applied to the surface layer of the molten metal 12. Static pressure corresponding to the distribution acts. As is clear from FIG. 4a, the molten metal 12
A virtual circle 60 centered at a position 59 slightly below the center position 58 of the molten metal 12 is formed on the surface layer of the molten metal 12.
, but a static pressure acts along a curve 61 that slightly bulges laterally from the virtual circle 60.

If the static pressure is uneven along the circumferential direction of the molten metal 12 as shown in FIG. becomes. Therefore, in the present invention, the difference in static pressure is compensated for by the electromagnetic force generated by the coil 41 of the electromagnetic field generating means 34, and the contact pressure is made substantially uniform along the circumferential direction of the molten metal 12.

Referring to FIG. 5, the center position 5 of the molten metal 12
The coils are arranged corresponding to a perfect circle 66 centered at a position 62 slightly displaced upward from 8. Then, since the electromagnetic force acting on the surface layer of the molten metal 12 is inversely proportional to the distance from the coil, it becomes larger as it moves downward, as shown by the solid arrow. However, this electromagnetic force distribution corresponds to a curve 65 that is considerably concave in the lateral direction from a virtual circle 64 centered at a position 63 below the center position 58. Here, as described above with reference to FIG. 4, the static pressure distribution has a shape slightly bulging in the lateral direction from the virtual circle 61. Therefore, if the electromagnetic force having the distribution shown in FIG. 5 is used to compensate for the difference in static pressure along the circumferential direction of the molten metal 12, the contact pressure at the top and bottom of the molten metal 12 will be equalized. However, the contact pressure on both sides of the molten metal 12 will be greater than on the upper and lower parts.

Therefore, the coil 41 is shaped as shown in FIG. 6, and a curve 6 similar to the curve 61 in FIG.
A distribution of electromagnetic force corresponding to 7 is generated. In other words, the shape of the coil 41 is the perfect circle 66 described above.
It has a substantially elliptical shape that is slightly concave in the lateral direction, and its center is slightly displaced upward from the center position 58 of the molten metal 12. By doing this, the distribution of electromagnetic force is shown by a curve 67. Since the curve 67 is similar to the static pressure distribution curve 61 in FIG. 4, the contact pressure obtained by subtracting the electromagnetic force from the static pressure is distributed in the circumferential direction of the mold 3 as shown by the dashed arrow in FIG. It becomes uniform along the line. In addition,
The electromagnetic force of the coil 41 is selected such that sufficient contact pressure is applied to the inner surface of the mold tube 15 above the molten metal 12.

As described above, even if the shape of the coil 41 is slightly concave in the horizontal direction from the perfect circle 66 and the center is shifted upward from the center position 58 of the molten metal 12, in reality, the molten metal 12 The contact pressure along the circumferential direction may become slightly uneven. Therefore, at the exit end of the mold 3, a first
As shown in the figure, a solidification thickness gauge 68 measures the thickness of the solidification shell formed on the surface layer of the molten metal 12.
A plurality of are provided in the circumferential direction. mold tube 1
Since the contact pressure to the inner surface of the molten metal is approximately proportional to the thickness of the solidified shell, by measuring the solidified thickness with the plurality of solidified thickness gauges 68, the distribution of the contact pressure of the molten metal along the circumferential direction can be determined. It can be almost measured. Therefore, the cylinder 55 is driven to expand and contract via the control means 69 so that the solidified thickness measured by each solidified thickness gauge 68 is approximately equal. As a result, the electromagnetic field generating means 34 is vertically displaced within the storage space 40, so that the distribution of electromagnetic force acting on the surface layer of the molten metal 12 can be subtly changed. Therefore, the molten metal 1 to the inner surface of the mold tube 15
It becomes possible to always make the contact pressure of 2 uniform along the circumferential direction.

According to this embodiment, since the molten metal 12 contacts the inner surface of the mold tube 15 with uniform pressure along the circumferential direction, the molten metal 12 is uniformly cooled along the circumferential direction, and the mold tube 15 wears unevenly. There's nothing to do. Furthermore, even if the surface layer of the molten metal 12 shrinks due to cooling and forms a solidified shell, the electromagnetic force becomes stronger as it moves downward, so the gap between the surface of the solidified shell and the inner surface of the mold tube increases. It is maintained almost uniformly along the circumferential direction. Therefore, even after the solidification shell is formed, the molten metal is cooled almost uniformly along the circumferential direction. Furthermore, since the electromagnetic field generating means 34 is provided within the coolant passage 31, the heat from the molten metal 12 is prevented from having an adverse effect on the coil 41, and the coil 41 is prevented from having an adverse effect on the coil 41.
Since the heat generated by the coil 41 is radiated to the cooling water, the coil 41 does not overheat. Moreover, coil 41
Since it is housed in a storage space 40 filled with dry gas, it is safe without any electrical leakage.
Furthermore, instead of sealing in dry gas, insulating oil or the like may be circulated through the coil box to also have a cooling effect. A relatively narrow gap 35 is formed between the storage box 25 and the outer surface of the mold tube 15, but since the cooling water flows through this gap 35 at a relatively high speed, cooling efficiency is improved.

Note that a lubricant (not shown) is applied to the inner surface of the mold tube 15 to lubricate the surface layer of the molten metal 12 and the inner surface of the mold tube 15. Since the contact pressure on the inner surface of the tube 15 becomes uniform along the circumferential direction, the amount of lubricant consumed becomes approximately equal along the circumferential direction.

As another embodiment of the present invention, a surface thermometer may be provided at the outlet of the mold 3 in place of the solidification thickness gauge 68 described above. Another effect of the present invention is that the centering effect of the mold and solidification shell of the foot roller at the mold outlet end used in a vertical continuous casting machine can be achieved by providing the electromagnetic force generating device of the present invention in the mold. It can be obtained in a non-contact manner.

As yet another embodiment of the present invention, the mold tube 15 may be configured to have a rectangular cross section perpendicular to the axis. In this case, static pressure having a distribution as shown in FIG. 7 acts on the surface layer of the molten metal 12. That is, as shown in FIG. 7b, since static pressure is inversely proportional to the height, a static pressure acts on the surface layer of the molten metal 12, which becomes larger toward the bottom as shown in FIG. 7a. Therefore, as shown in FIG. 8, if a coil 41 having a shape that is approximately symmetrical to the curve 72 showing the static pressure distribution in FIG. The result is as shown by curve 73 in FIG. That is, an inwardly concave electromagnetic force distribution is obtained on both sides of the molten metal 12. If the static pressure in FIG. 7a is compensated for by the electromagnetic force given by such a curve 73, the contact pressure on both sides of the molten metal 12 will be relatively large. Therefore, if the shape of the coil 41 is made to be slightly recessed inward from both sides of the curve, the electromagnetic force distribution at that time becomes a curve 74 shown by a broken line. This curve 74 is similar to the curve 72 showing the static pressure distribution in FIG. can be made almost uniform over the entire circumference.

As another embodiment of the present invention, the electromagnetic field generating means 3
4 may not be provided in the coolant passage 31 of the mold 3, but may be arranged outside the mold 3 in the radial direction, surrounding the mold 3. However, in this case, since the distance between the electromagnetic field generating means 34 and the surface layer of the molten metal 12 is relatively large, the power supplied to excite the coil 41 is relatively large.

Also, it is not necessary to surround the mold tube 15 with a single coil over the entire length of the mold 3.
The mold tube 15 may be surrounded by a plurality of coils along the axial direction of the mold 3. Further, as shown in FIG. 9, a coil 7 is attached to a core 75 extending in the axial direction of the mold tube 15.
A plurality of electromagnetic field generating means 77 formed by winding 6
may be arranged at intervals in the circumferential direction of the mold tube 15, and the induced current absorbing plate 77' may be arranged inside. In this case, the electromagnetic field generating means 77 may be arranged in the same shape as the coil 41 shown in FIG. 8 above, or the power supplied to each electromagnetic field generating means 77 may be adjusted to An electromagnetic force distribution similar to the curve 74 shown by the broken line may be formed.

FIG. 10 is a perspective view of another embodiment of the invention. This embodiment shows a case where the mold tube 15 is configured in a flat rectangular shape that is short in the vertical direction, and the vertical distance l1 is extremely small compared to the widthwise distance l2. In such a case, as shown in FIG. 11, there is little change in the static pressure on both sides of the surface layer of the molten metal 12. Therefore, an induced current absorbing plate 80' is arranged only below the mold tube 15 together with an electromagnetic field generating means 80 formed by winding a coil 79 around a core 78. Then, an upward electromagnetic force acts on the lower part of the molten metal 12, as shown by the broken line arrow in FIG. Therefore, the relatively large static pressure at the lower part of the mold tube 15 is compensated for, and a substantially uniform contact pressure can be obtained over the entire circumference of the mold tube 15.

FIG. 12 is a sectional view of still another embodiment of the present invention. In this embodiment, the tundish nozzle 14 protrudes from the tundish 1 relatively long, and the tundish nozzle 14 and the mold 3
An electromagnetic field generating means 82 surrounding the boundary 81 is provided near the boundary 81, and an induced current absorbing plate 82' is arranged inside the electromagnetic field generating means 82. The electromagnetic field generating means 82 includes a first coil 83 surrounding the vicinity of the boundary 81 and a second coil 84 . The first coil 83 is concentric with the axis of the tundish nozzle 14 and the mold 3, and generates a magnetic force for compensating the static pressure of the surface layer of the molten metal 12 near the boundary 81. Further, the second coil 84 is arranged eccentrically above the axis of the tundish nozzle 14 and the mold 3, and compensates for the differential pressure between the upper and lower portions of the molten metal 12 near the boundary 81.

Due to the electromagnetic field of the electromagnetic field generating means 82, the boundary 8
Molten metal 12 passing near 1 is reduced in diameter and constricted radially inward. Therefore, near the boundary 81, the molten metal is prevented from coming into contact with the portion of the duplication nozzle 14 near the mold 3.
Therefore, the solidified shell is prevented from sticking to the tundish nozzle 14, and the cast body 4 can be continuously pulled out.

In such horizontal continuous casting equipment, a lubricant is supplied between the inner surface of the mold tube 15 and the surface layer of the molten metal 12. That is, the tundish nozzle 14 has a ring-shaped header 85.
A nozzle 8 is formed in the header 85 toward the radially inward side of the tundish nozzle 14.
6 is formed. A lubricant 88 is supplied to the header 85 via a conduit 87. In addition, the nozzle 86
is located forward in the drawing direction from the position 89 where the molten metal 12 separates from the tundish nozzle 14. The lubricant 88 is mainly composed of powders of CaO, SiO ₂ and Al ₂ O ₃ and is further mixed with powders having good electrical conductivity such as pure iron and Co. Lubricant 8 mixed with such powder having good electrical conductivity
8, an electromagnetic force directed inward in the radial direction of the tundish nozzle 14 and mold tube 3 acts on the powder having good electrical conductivity by the electromagnetic field generating means 82, thereby causing the lubricant 88 to It is attached to the entire outer peripheral surface of the reduced diameter molten metal 12. Therefore, the reduced diameter molten metal 12 is transferred to the passage 1.
The lubricity with the part that first comes into contact with 6 is improved.

However, if the contact pressure at which the surface layer of the molten metal 12 comes into contact with the inner surface of the mold tube 15 in the mold tube 15 is uneven along the circumferential direction, the lubricant 88 may be applied along the inner surface of the mold tube 15. Supply becomes uneven. Therefore,
As shown in FIG. 2 above, the electromagnetic field generating means 34 is provided surrounding the mold tube 15.
Then, as in each of the above embodiments, the molten metal 1
An electromagnetic force acts on the mold tube 15, so that the contact pressure of the molten metal against the inner surface of the mold tube 15 becomes substantially uniform along the circumferential direction. Therefore, the amount of lubricant 88 supplied becomes substantially uniform along the circumferential direction, improving lubricity.

As described above, according to the present invention, an electromagnetic force having a distribution corresponding to the static pressure distribution is applied to the molten metal in the mold to compensate for the static pressure, so that the molten metal does not reach the inner surface of the mold. The contact pressure becomes substantially uniform along the circumferential direction. Therefore, uneven cooling of the molten metal, deformation, cracking, breakout, etc. of the steel ingot caused by the non-uniformity of the contact pressure is prevented, and uneven wear on the inner surface of the mold is prevented. Furthermore, when lubricant is supplied, the supply amount is substantially uniform along the circumferential direction, improving lubricity.

In particular, according to the present invention, a coil is arranged around the outer periphery of the mold tube and this coil is excited by alternating current power, so there is no need to provide an electrode within the molten metal in the prior art described above. The excellent effect of this is that maintenance is extremely easy.

Moreover, according to the present invention, the contact pressure on the inner surface of the mold tube is approximately proportional to the thickness of the solidified shell, and therefore, by measuring the thickness of the solidified shell, the contact pressure can be determined. be able to.
This solidified thickness corresponds to the surface temperature of the cast body, and therefore, the solidified thickness can be determined by measuring the surface temperature of the cast body using a surface thermometer as described above. , from which the contact pressure can also be determined. In this way, by adjusting the vertical displacement of the coil in accordance with the measured thickness of the solidified shell, sufficient contact pressure is applied to the inner surface of the mold tube at the top of the molten metal, and the contact pressure is It becomes possible to make it uniform along the circumferential direction of the mold. Therefore, it becomes possible to obtain a high quality cast body.

[Brief explanation of the drawing]

Fig. 1 is an overall system diagram of an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the vicinity of the mold 3, Fig. 3 is a sectional view taken from the cutting plane line - in Fig. 2, and Fig. 4 is A diagram showing the static pressure distribution in the surface layer part of the molten metal 12 in the mold 3, FIG. 5 is a diagram showing the electromagnetic force distribution,
FIG. 6 is a diagram showing the electromagnetic force distribution due to the coil 41,
FIG. 7 is a diagram showing the static pressure distribution in another embodiment of the present invention, FIG. 8 is a diagram showing the electromagnetic force distribution, FIG. 9 is a sectional view of another embodiment of the present invention, and FIG. 10 is a diagram showing the electromagnetic force distribution. FIG. 11 is a perspective view of another embodiment of the invention, FIG. 11 is a diagram showing static pressure distribution and electromagnetic force distribution in the embodiment of FIG. 10, and FIG. 12 is a sectional view of another embodiment of the invention. 1...Tandatetsuyu, 3...Mold, 12
... Molten metal, 14 ... Tandate nozzle,
15...Mold tube, 34, 77, 80,
82... Electromagnetic field generating means, 41, 76, 79...
coil.

Claims (1)

[Claims] 1. A coil is disposed on the outer periphery of the mold tube so that its displacement can be adjusted up and down, and this coil is excited with AC power to measure the thickness of the solidified shell of the cast body. The vertical displacement of the coil is adjusted according to the thickness of the solidified shell, and the molten metal in the mold tube has a distribution that corresponds to the distribution of static pressure that acts on the surface layer of the molten metal. Apply an electromagnetic force in the opposite direction to the mold tube so that sufficient contact pressure acts on the inner surface of the mold tube at the top of the molten metal and that the contact pressure is uniform along the circumferential direction of the mold. Characteristic horizontal continuous casting method.