JPH03204145A - Method and apparatus for horizontal rotary continuous casting - Google Patents

Abstract

PURPOSE:To stably produce a continuously cast billet having good quality without solidified segregation and solidified shrinkage hole by pressurizing the continuously cast slab before completely solidified in a groove for casting with a roll type screw down apparatus at the time of continuously casting the molten steel while rotating an endless ring type mold having the groove of narrow width for casting. CONSTITUTION:The molten steel in a ladle 1 is poured into a rotating mold 5 having the annular groove of narrow width for casting from a nozzle 4 through an intermediate vessel 3 and cooled and solidified while rotating the mold 5 to the arrow mark 8 direction without oxidizing the surface with non-oxidizing atmospheric means 9 to make the continuously cast billet 12. In this case, the rolling reduction is executed at >= 1% draft to the continuously cast billet 6, the inner part of which is not yet solidified, with the roll type screw down apparatus 11 under condition within the range of 0.5 - 1 solidified ratio. To unsolidified molten metal part in the continuously cast billet 6, the development of solidified segregation and solidified shrinkage hole is prevented with pressurizing and after drawing out the continuously cast billet 12 having small cross sectional area and excellent quality and structure from the annular mold 5 with a cast billet drawing straightening device 13, this is cut 14 to the prescribed length.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to continuous casting of molten metal, mainly molten steel, and particularly to a horizontal rotation continuous casting apparatus and casting method for casting small cross-section slabs.

(Prior Art) A horizontal rotating groove method is a method for continuously casting small cross-section slabs. In this horizontal continuous casting method, one side of the cross section is lO~100mm.
It is suitable for casting slabs with small cross-sections, such as squares, and is characterized by low equipment costs and high productivity.
59, US Pat. No. 3,478,810, and Japanese Patent Publication No. 13785/1985.

U.S. Pat. No. 3,284,859 discloses a continuous casting apparatus equipped with an annular rotary cooling mold having a tub-shaped cross section, with the long side of the tub facing a metal supply device. This mold is formed with a casting groove into which molten metal is supplied from a gate device. The mold is driven to rotate around a vertical axis. A forced cooling device is provided which is poured into the mold.

The solidified slab is continuously withdrawn from the casting groove from a point located 200-270' from the injection point and fed to a continuous mill apparatus.

This mold is a groove type with an open top, and has a cooling structure with the remaining three sides made of copper alloy, etc., so the cooling of the top is weaker than the other three sides, and solidification is delayed. 6 Normally molten metal During the transformation from the molten state to the solid state, it exhibits shrinkage (solidification shrinkage) and concentration of solute elements (caused by partitioning into solid and liquid). Therefore, if solidification shrinkage occurs as solidification progresses mainly from the bottom and side surfaces, the slab will have a concave shape upon completion of solidification. In addition, the shape of the slab on the upper surface side is not constant because the molten metal surface on the upper surface side is undulated due to the influence of the pouring flow. Furthermore, since it solidifies in a horizontal state, the pushing vortex effect is low, and the molten metal supply performance is poor, and the molten metal is not replenished to match the solidification shrinkage, and solidification shrinkage holes are unavoidably likely to occur. Since this is the final solidification part, solute elements are concentrated and component segregation occurs.

The concave shape of the slab causes the corners to collapse in the subsequent rolling process, leaving continuous defects in the product in the rolling direction, and the presence of component segregation.

This means that the mechanical properties differ depending on the location within the cross section of the slab. Moreover, if solidification shrinkage holes exist, they will not disappear during the rolling process and will result in a product defect. Such slabs cannot be put to practical use in today's world, where product quality is becoming increasingly strict.

To solve these problems, Japanese Unexamined Patent Publication No. 61-195756 and Utility Model Application No. 62-11384
There is one described in Publication No. 3.

JP-A-61-195756 discloses that when casting using an endless ring mold, static pressure of molten steel is applied to the unsolidified part of the slab at an appropriate angle in the casting direction, so that the solidified shell on the upper surface side is It has been pointed out that there is an appropriate range for preventing denting and for the angle of inclination depending on the casting speed. Indeed, according to a reproduction experiment conducted by the present inventors, the concavity was improved up to the stage where a solidified shell was formed on the upper surface of the slab and the liquid phase still remained, and there was even a tendency for it to swell upward, clearly indicating that the effect was I was able to confirm something. However, as the solidification progressed further, the solidified shell on the upper surface side again became depressed. This is due to the contraction that occurs upon completion of solidification, as described above. Moreover, what is more fatal is that when the cast slab was cut out and the cross section was observed, there were many solidification shrinkage holes.

Therefore, it was found that improving the slab surface by tilting was not very effective. Furthermore, due to the increase in static pressure of molten steel due to inclination, no improvement in the feeder effect during solidification shrinkage can be expected, and it is clear that there is no industrial use value.

On the other hand, the one described in Japanese Utility Model Application Publication No. 62-113843 is
It is mainly intended for molding the upper surface of a slab, and mechanically flattens the unevenness that occurs during casting.

According to this, it is expected that the upper surface of the slab will appear smooth, but the surface of the slab to which pressure is applied will react with oxygen in the air and form an oxide layer (scale). Therefore, scale is generated on the surface which is originally uneven, so even if it is rolled down, it remains as slab defects and there is no effect of rolling down.Furthermore, solidification shrinkage pores and segregation are inevitably formed, so the surface 6 Surface defects, which determine the quality of the final product more than defects, can be improved by taking care of the slab, if you are prepared for a slight decrease in yield, so it is first necessary to develop a means to improve solidification shrinkage holes or segregation. is important.

In addition, the same publication includes a description of the shrinkage holes, that is, solidification shrinkage holes, but when reducing the shrinkage holes using a reduction device,
Although it is essential to clarify the progress state of coagulation, that is, the coagulation rate (solid fraction) and rolling conditions, there is no quantitative clarification.

In the above points, the publication lacks specificity from the standpoint of practical and industrial production, and does not provide effective means.

(Problems to be Solved by the Invention) An object of the present invention is to use a continuous casting device for molten metal in which a mold having an endless grooved ring mold with an open upper part rotates in the horizontal direction. When casting slabs with small cross-sections, such as square slabs, in order to maximize low equipment costs and high productivity, solidification segregation and solidification shrinkage pores, which are the biggest problems in casting principles, can be completely ignored in terms of quality. The goal is to provide a means to improve the results.

(Means for Solving the Problems) The gist of the present invention is to use a small-section continuous casting device for molten metal in which a ring mold with an open top and an endless groove rotates in the horizontal direction, and a slab reduction device is installed on the top of the slab. Horizontal rotary continuous casting, which is provided in the upper open part of the mold after the solidification completion position and/or in the cooling zone, and is characterized in that the final solidification part solid fraction is in the range of 0.5 to 1 and the reduction is performed at a reduction rate of 1% or more. method, and
In a small-section continuous casting machine for molten metal in which an endless grooved ring mold with an open top rotates horizontally, a slab reduction device consisting of rolls or a surface reduction device is installed at the top open part of the mold after the solidification of the top surface of the slab is completed. or/and a horizontal rotary continuous casting device, characterized in that the cooling zone is provided with a homogeneous ratio of the final solidified part in the range of 0.5 to 1; Horizontal rotary continuous casting device characterized by having a tapered roll whose speed is the same throughout the area, horizontal rotary continuous casting device characterized by having a rolling device with a roll whose roll diameter changes in the roll axis direction, and rolling device. A horizontal rotary continuous casting device characterized in that the roll is a roll and the roll is a part of a spherical shell having a radius of curvature equal to the radius of the rotating mold, and a rolling device is provided with a driving means, and the rolling device is synchronized with the slab rotation speed. This is a horizontally rotating continuous casting device that is characterized by:

(Function) Hereinafter, the function of the present invention will be explained in detail using the drawings.

First, FIG. 1 specifically shows the process in which molten metal is cast.

Molten metal is injected from a molten metal filling 1 into an intermediate container 3 using an injection amount control device 2, and is injected into an endless groove type rotary mold 5 through an injection nozzle 4. A molten metal backflow prevention weir 7 is provided in the mold 5, and the molten metal is cast only in a casting direction 8, and becomes a slab 6 as it solidifies. Next, if necessary, a non-oxidizing atmosphere maintaining means 9 is provided on the upper surface of the slab to prevent quality deterioration due to oxidation of the molten metal on the upper surface side. During this time, the molten metal is solidifying preferentially from the sides and bottom of the slab, but eventually the top side also solidifies.
A solidified shell is formed and reaches the slab reduction device 11. The slab is
A reduction is applied from the upper surface side by the reduction device 11, and the suction force of the concentrated liquid phase due to the solidification contraction pores and negative pressure caused by the solidification contraction generated in the previous solidification process is eliminated. That is, the solidification shrinkage pores that occur in the slab due to rolling are closed, and center segregation is improved. At the same time, the slab surface also becomes smooth. By maintaining a non-oxidizing atmosphere, the upper surface side is free from the influence of scale on the surface and is in good condition.

Further, the slab is rolled down to become a slab 12 in good condition, which is taken out of the continuous caster from the rotary mold by a slab pulling and straightening means 13, and cut into a length that can be rolled by a cutting machine 14. It is also possible to arrange a rolling mill downstream of the casting apparatus and perform rolling directly after or without cutting.

FIG. 1 shows a mold in which a roll rolling device is provided on the upper surface of the mold, and one or more rolling devices may be provided. In addition, the rolling device driving means includes a roll bearing, a hydraulic cylinder for adding a rolling blade,
It has a structure that can utilize the repulsive force of wedges and springs. Since the roll is brought into close contact with the slab by the reduction blade, it automatically rotates as the mold rotates, that is, as the slab advances, but it is also possible to configure it in combination with an external rotation drive device such as an electric motor. In these configurations, it is preferable that an electric motor for rotating the roll is provided, and a double rolling mechanism including a hydraulic cylinder and a spring is used to facilitate the operation of the rolling blade.

FIG. 2 shows a device in which the rolling down device 11 and the driving means 18 for the rolling down device are also provided on the slab outlet side. In this case, it can be constructed in combination with the slab pulling straightening means 13. Also,
The rolling down device may be installed either inside the mold or on the outlet side of the continuous casting machine, and does not necessarily need to be installed on both sides.

FIG. 3 is a bird's-eye view showing the relationship between the rolling down device 11, the mold 5, and the slab 6.

FIG. 4(a) shows a case where a tapered roll is used in the rolling down device 11. In this case, the roll rotation axis is inclined due to the taper, but the speed of the slab on the inner and outer sides of the mold is There is always a speed difference between the outer and inner sides of a zero-rotation mold due to the radius difference, and if a rolling device is introduced here, the speed difference at the rolling part will cause the inside of the slab to The deformation state is different between the circumferential side and the outer circumferential side,
Slippage occurs on either the inner or outer periphery, causing scratches. Therefore, by tapering the rolls of the rolling down device, it is possible to completely prevent flaws caused by speed differences, and to obtain good slabs. Fig. 4 fbl, fc) shows the details of the cross section A-A of the rolling down device, and the details before and after rolling down the slab (cross section A-A,
It is a figure which shows typically the shape change of the slab of cross section BB), and the prevention process of the solidification shrinkage hole.

FIG. 5 fat is an example in which a drum-shaped roll is used instead of a tapered roll. This makes it possible to preferentially reduce the central portion of the width of the slab, which is necessary to prevent solidification shrinkage holes and segregation, and allows effective reduction. Figure 5 (b)
~ (el is the same as in Fig. 4. Fig. 6 shows rolls for more effective and flexible rolling. The endless groove type horizontal rotating continuous casting machine according to the present invention has a ring-shaped mold. Therefore, when a roll is used as the rolling down device, the shapes of the mold groove and the rolling roll can only be designed within a range that does not interfere with each other.When designing or modifying the device, it is determined by its geometric dimensions. It is difficult to always maintain the quality of slabs of all metals, sizes, and grades. As a solution to this problem, there is a solution shown in FIG. 6 (ta+).

Figure 6 (Al is a plan view with the rolling down device installed; the roll is curved along the radius of the mold. In other words, the roll is part of a spherical surface equal to the radius R of the mold. , the width of the roll is equal to the slab width W as shown in the figure (bl), so there is no interference with the mold as shown in Fig. 6fc, and the radius r of the rolling roll can be set arbitrarily. Being able to arbitrarily change the radius of the reduction roll enables the reduction gradient (reduction speed) given to the slab and the stable bite of the reduction roll.In other words, the reduction roll and Let the horizontal distances between the initial contact point and roll kiss point of the slab be Ll and L2 (Ll > L
x) and the amount of reduction is δ, the reduction gradient is δ/L,
, δ/L, (δ/L1<δ/L,), and the roll radius is increased (by doing so, the rolling gradient becomes smaller.Furthermore,
By increasing the roll radius, it is possible to increase the amount of reduction that can be bitten. This roll radius is not particularly regulated and may be any value, but approximately 5% to 30% of the mold radius is sufficient.

FIG. 7 is a block diagram showing a method for controlling the speed of the rolling down device when a driving means is added to the device. When operating the mold drive means 16, the rolling device drive means 18, and the drawing straightening device drive means 19, the reduction ratio of each device is taken into consideration, and a ratio converter is provided upstream of each drive means control device to control the slab. It becomes possible to operate in synchronization with the speed.

Furthermore, if matching is possible using a mechanical conversion ratio (eg, gear ratio, sprocket ratio, etc.), the ratio converter can be omitted since the ratio to be given to the ratio converter is l.

Figure 8 (al) is a bird's-eye view of the rolling part when a surface rolling down device is used as the rolling down device. Figure 8 (bl, (c))
This is a diagram showing a section A-A in the casting direction of the same figure (at). This is a view that presses the surface reduction device against the slab by a driving means 18 such as a hydraulic device. It has a structure that gives vibration or rocking motion to the surface pressure lowering device by giving reciprocating motion.The vibration and rocking motion are phases.The drive means 18 for the pressure lowering device includes a spring mechanism, an eccentric cam mechanism, a link, etc. It is possible to configure it by a mechanism or the like.

FIG. 9 schematically shows the timing of rolling down and the principle of quality improvement by rolling down. Reduction is performed after the upper surface of the slab has solidified, but even in this case, a liquid phase still exists inside.

However, as the solidification progresses, the passage area decreases, making it difficult for the liquid phase to move easily, making it impossible to replenish the liquid phase to match the solidification shrinkage, resulting in solidification shrinkage pores. In addition, impurity components in the liquid phase immediately before completion of solidification are concentrated, which causes segregation. Therefore, a reduction roll is used to deform the material from the outside by an amount corresponding to the amount of solidification shrinkage. In addition, it is possible to cause liquid phase flow as shown in the figure by pressure reduction.
The concentrated liquid phase can be squeezed. Regarding the rolling position, as shown in the figure, it cannot be rolled down in principle until solidification on the upper surface side is completed.

Fig. 1O is a diagram explaining the optimum rolling timing when using the continuous casting method of the present invention, in which (a) is a cross section in the longitudinal direction at the center of the width of the slab, and Fbl in the figure is a horizontal plane of the slab. The solidification progress state of a cross section in the longitudinal direction at a height two-thirds from the bottom surface was determined by numerical calculation using carbon steel as an example. The possible rolling position varies depending on the type of cast metal, casting speed (V), degree of casting superheat (difference ΔT between casting temperature and liquidus temperature), etc., but can be easily estimated by calculation. In the figure, the solid phase ratio is shown as a parameter; 0 indicates a completely liquid phase state, 1 indicates a completely solid phase state, and intermediate values indicate the ratio of solid phase to liquid phase.

In the endless channel type horizontal rotary continuous casting method of the present invention, the lowest internal solid fraction at the time when rolling is possible is 05, and the method of the present invention allows rolling to be performed within the solid phase ratio range of 0.5 to 1.0. It can be carried out. Usually, to prevent solidification segregation and solidification shrinkage pores,
Appropriate reduction timing can be estimated depending on whether or not the liquid phase can pass through the metal in a semi-solidified state. Further, the solid phase rate through which the liquid phase can pass is actually measured as the flow limit solid phase rate, and the value is often around 0.6 to 0.7. Therefore, it can be said that the present invention is theoretically capable of applying a reduction in a wide range of 0.5 to 1.0, and is also effective in preventing defects during solidification of metal6 (Example) For casting The metal used was carbon steel shown in Table 1. Since casting was carried out using independent charges in both Examples and Comparative Examples, the composition ranges are shown.

Table 1 (Common to Examples and Comparative Examples) Weight%
The casting and rolling conditions are shown below.

Example 1 ■ Casting Casting method % formula % Casting size knee 40mm Mold radius R: 1000mm Casting speed V ・7.0m/min Molten steel superheat degree △T・36°C Mold material: Copper alloy rolling down device: Tapered roll rolling radius r: 150mm Roll width W: 40mm Light reduction casting, reduction rate 1-15% ■Hot rolling heating temperature holding time Rolling ratio Cooling after rolling: 1150℃: 2hr: 1.8 (≠40mm → φ32mm): Air cooling Example 2 ■ Casting Casting method: Endless groove type horizontal continuous casting machine Casting size: φ40mm Mold radius R: 1000mm Casting speed V: 7.0m/min Molten steel superheat degree △T
: 36℃ Mold material, copper alloy rolling device: Surface reduction (rolling length: 200mm) Light reduction casting: Reduction rate 1 to 15% ■ Hot rolling heating temperature holding time Rolling ratio Cooling comparison example 1 after rolling ■ Casting Casting method Casting size Mold radius R Casting speed V Molten steel superheating degree △T Mold material reduction device: 1150℃: 2hr: 1.8 (φ40mm→φ32mm): Air cooling: Endless groove horizontal continuous casting machine: φ40mm: 1000mm: 7.0m/ min: 36℃: Copper alloy: None Light reduction casting: None ■Hot rolling heating temperature holding time Rolling ratio Cooling after rolling: 1150℃: 2hr: 1.8 (φ40mm→φ32mm): Air cooling comparative example 2 ■Casting Curved Mold continuous casting machine (current CC) casting size
: 350mm x 560mm machine radius :
12 mR Casting speed: 0.9m/min Molten steel superheating degree = 25℃ Mold material: Copper alloy light reduction casting: None Hot rolling heating temperature: 1150℃ Holding time: 2hr Rolling ratio: 244 (350mmX 560mm -1φ32+nm) rolling Post-cooling: The solid fraction of the slab during rolling in the air-cooled example is about 0.68, as shown in FIG.

FIG. 11 is a diagram showing the solidification shrinkage pore area ratio and segregation degree of slabs obtained in Example 1.2 and Comparative Example 1.2. The rolling reduction rate O is the average value of Comparative Example 1, and the other values are the average values of Example 1.2. From this, the rolling reduction is 1% or more, preferably 5%.
It can be seen that by applying the above reduction, both the solidification shrinkage pores and the degree of segregation are significantly improved.

FIG. 12 shows the quality characteristics of the final product of the steel bar obtained by further rolling the slab. The horizontal axis is plotted using carbon equivalent to normalize component variations. Note that the values of Example 1.2 are for the case where the slab was manufactured from a slab that was rolled at a rolling reduction rate of 5%. Comparative Example 2 is the quality range currently achieved on a commercial production basis.6 Examples 1 and 2 are all equivalent to or higher than the quality level achieved in Comparative Example 2, that is, current commercial production. It can be seen that excellent characteristics can be achieved. Furthermore, considering that the rolling ratio in Example is 1.8 and the rolling ratio in Comparative Example 2 is 244, it can be seen that the method of the present invention makes it possible to reduce the rolling ratio, that is, to significantly reduce the number of rolling mills. It can be said that this is an extremely effective casting method not only for improving quality but also for simplifying production equipment. On the other hand, although Comparative Example 1 is an example in which the reduction during casting is omitted, the cross-sectional shrinkage rate of the product, that is, the reduction of area, is low, so it can be said that reduction during casting is essential for improving product quality.

(Effects of the Invention) As shown above, solidification segregation and solidification shrinkage, in which quantity is also important in terms of quality, can be achieved by using a small-section continuous casting device for molten metal in which an endless grooved ring mold with an open top rotates horizontally. Holes can be prevented by reducing the slab during the casting process. moreover,
The present invention not only improves product quality, but also simplifies the manufacturing process, which in turn can significantly reduce manufacturing costs, making it an extremely useful invention industrially.

[Brief explanation of drawings]

Fig. 1 is a plan view showing a horizontal rotary continuous casting device of the present invention, Fig. 2 is a plan view showing an example of a horizontal rotary continuous casting device of the present invention in which a reduction device is provided on the continuous caster side, and Fig. 3 is Figure 4 shows an example in which a roll is used as the rolling device. Figure 4 is a diagram showing an example in which a tapered roll is used in the rolling device. Figure 5 is an example in which a roll is used in the rolling device and the roll diameter changes in the roll axis direction. Figure 6 shows an example in which a roll is used as a rolling device, and the roll shape is a part of a spherical surface, and Figure 7 shows a case in which a rolling device and a casting device are used in combination, and each device is Fig. 8 is a diagram showing the case where a surface reduction device is used as the reduction device, and a diagram showing a case where only the reduction blade acts on the surface reduction device and a case where the surface reduction device is moved. A diagram showing the progress of solidification and the installation position of the rolling down device in the horizontal rotary continuous casting apparatus of the present invention. Figure 10 is a diagram explaining the optimum rolling down timing of the continuous casting method of the present invention. Figure 11 shows an example. FIG. 12 is a diagram showing an example and a comparative example. l... Molten metal ladle, 2... Injection amount control device. 3... Intermediate container, 4... Injection nozzle, 5... Endless groove rotary mold, 6... Slab, 7... Molten metal backflow prevention weir, 8... Casting direction, 9... ... Non-oxidizing atmosphere holding means, 10... Non-oxidizing atmosphere medium introduction part, 11...
- Slab rolling device, 12... Slab, 13... Slab drawing straightening means, 14... Cutting machine, 15... Injector driving means, 16... Mold driving means, 17... - Rotary power transmission member, 18... Drive means for the lowering device, 19...
Driving means for a slab drawing straightening device.

Claims (6)

[Claims] (1) Using a small-section continuous casting device for molten metal in which an endless grooved ring mold with an open top rotates horizontally, the slab lowering device is installed at the top open part of the mold or/and after the top solidification position of the slab. Provided in the cooling zone, the final solidification part solid fraction is 0
．． A horizontal rotation continuous casting method characterized by performing reduction at a reduction rate of 1% or more in the range of 5 to 1. (2) In a small-section continuous casting device for molten metal in which an endless grooved ring mold with an open top rotates in the horizontal direction,
A slab reduction device consisting of a roll or a surface reduction device is provided in the mold upper open part or/and cooling zone after the solidification completion position of the slab top surface so that the final solidification part solid fraction is in the range of 0.5 to 1. Horizontal rotating continuous casting equipment. (3) The horizontal rotary continuous casting apparatus according to claim 2, wherein the rolling down device is a tapered roll whose entire contact area with the slab has the same speed. (4) The horizontal rotary continuous casting apparatus according to claim 2, wherein the rolling down device is a roll whose diameter changes in the axial direction of the roll. (5) The horizontal rotary continuous casting apparatus according to claim 2, wherein the rolling down device is a roll, and the roll is a part of a spherical shell having a radius of curvature equal to the radius of the rotary mold. (6) The horizontal rotary continuous casting apparatus according to claim 2, characterized in that a driving means is added to the rolling down device and synchronized with the rotational speed of the slab.