JP2518927B2 - Method of starting forging pressure of cast strand in continuous forging processing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is useful for reducing the internal quality of cast strands obtained by continuous casting, especially for reducing casting defects such as center segregation and center porosity. The present invention relates to a method for starting a forging pressure of a cast strand, which can achieve simplification and compactification of a forging device.

(Prior Art) As a conventional device for continuous forging processing, a hydraulic press type is the mainstream, and a device utilizing such a boosting mechanism as disclosed in JP-A-61-222663 (Caesar system) is used. ), Or a type in which a pair of upper and lower molds equipped with a hydraulic cylinder as shown in Japanese Patent Laid-Open No. 63-49400 are used to uniformly reduce the pressure.

(Problems to be Solved by the Invention) By the way, the conventional apparatus having a mechanism using the hydraulic press system has the following problems.

That is, a very large hydraulic power source and a large number of pipes are required to drive the forging die installed in the device, and the burden of equipment and maintenance becomes enormous.

Since the hydraulic pressure becomes extremely high, the life of the pump and switching valve installed in the device depends on the usage conditions, but it is as short as 2-3 years,
Moreover, the noise during forging processing should exceed 100 horns.

Further, in the case of the hydraulic system, since electric energy is converted into hydraulic pressure and transferred from the pump chamber to the forging device, the energy loss during this period is 20 to 30%, which is not optimal in terms of running cost.

Further, when such a forging pressure device is applied to a multi-strand continuous casting machine, and in a type in which a plurality of forging dies are incorporated in an integrated frame and the same drive source is used, the forging pressure start timing is different for each. Since the strands are almost at the same time, the impact on the equipment at that time is very large, and it is necessary to make not only the forging device but also the auxiliary equipment including it particularly robust, and the rise in equipment cost cannot be avoided. .

The problem that occurs when applying a forging device to a multi-strand continuous casting machine can be somewhat reduced by shifting the forging start time using a device such as that disclosed in JP-A-63-138472. It does not lead to simplification of the equipment, especially when simultaneously pulling out each slab strand, it causes an increase in defective slabs that are not forged due to inconsistencies in the forging pressure start timing. I can't.

It is an object of the present invention to propose a forging pressure starting method that can solve the conventional problems in the hydraulic press system and reduce the equipment capacity of the forging device, that is, achieve satisfactory forging processing without using such expensive equipment. Is.

(Means for Solving the Problem) The present invention is a slab strand that is being drawn and moved by causing a pair of forging dies that vertically sandwich a path line of the slab strand that is drawn from a continuous casting mold to approach and separate from each other. When continuously forging the final solidification zone of
When starting the forging process of the slab strand, the projected reduction length by the forging die is shorter than the projected reduction length obtained when rolling down to the target amount of reduction in one reduction and by the forging die. It is a method for starting the forging pressure of a slab of strands in continuous pressing, characterized in that the forging dies are moved toward and away from each other a plurality of times so as to wrap a known working area, and are pressed to a target reduction working amount.

Further, the present invention is a pulling movement by making a pair of upper and lower forging dies sandwiching each pass line of a cast strand drawn from a plurality of molds arranged in parallel in a multi-strand continuous casting device to approach and separate from each other. When continuously forging the final solidification region of the slab strand in the thickness direction, at the time of starting the forging process of the slab strand, the projection reduction length by the forging die was set as a target with one reduction. Each forging die is made to approach and separate from each other multiple times so as to make it shorter than the projected length obtained when rolling down to the rolling amount and to wrap the known work area by the forging die, and each cast strand Is a method for starting the forging pressure of the continuous cast strand in the continuous forging process, which is characterized in that the forging process time is shifted to a target reduction amount.

Now, the first (a) and (b) shows the main part of the upper half of the cast strand that is pressed down by the continuous forging die, where 1 in the figure is the cast strand and 2 is the forging die. The mold 2 sandwiches the slab strand 1 vertically, and the final solidification area of the slab strand 1 is continuously forged by the mutual approach and separation of the strands 1.

The present invention, when forging the cast strand 1,
The reduction start position is divided into two or more times to reduce the target reduction amount δ. When the present invention is applied to a multi-strand continuous casting machine, the reduction amount δ is also reached until the target reduction amount δ is reached. The rolling reduction is performed in two or more steps. At this time, the casting start time between each strand is controlled by controlling the start time of casting in each mold and the casting speed of the cast strand drawn from the mold. To do.

During the forging process of the slab strand 1, the slab strand 1 is pulled out at a predetermined speed.

(Operation) In a hydraulic continuous forging device, the rolling force of the casting die is generally determined by the rolling amount of the slab strand, the temperature, and the die shape. The area and the hydraulic pressure (hydraulic pressure) of the hydraulic device that controls the reciprocating drive of the forging die 2 are determined. Further, the discharge capacity of hydraulic pressure that determines the speed at which the forging die 2 is reciprocally driven is determined by the reduction cycle and the reduction amount during the forging of the cast strand 1.

Here, the first reduction in forging, that is, the reduction at the reduction start position of the cast strand 1 is as shown in FIGS. 1 (a) and 1 (b) during the second and subsequent reductions, that is, during steady forging. The contact area between the slab strand 1 and the forging die 2 is much larger than the rolling reduction, so if the rolling force of the forging machine is not adjusted to the required forging pressure at the rolling start position, the target rolling amount will be obtained. Can't reach up.

Therefore, the rolling force of the forging device is usually determined according to the first forging pressure.

However, since this forging pressure is the second and subsequent forging pressures, it is sufficient to secure the reduction amount (d) of the lapping margin as shown by the broken line, as is clear from FIG. 1 (a). This did not require as much rolling force as it did the first time, which caused an increase in equipment costs.

As shown in FIGS. 1 (a) and 1 (b) above, the necessary reduction force during steady forging is at the portion corresponding to the feed amount l _f of the forging die (hatched portion in the figure), that is, the projected length l. The corresponding rolling force is P, and the projected length l _S at the start of forging
When the rolling force corresponding to is P _S , the normal P _S / P is about 1.2 to 1.5.

According to the present invention, when the forging process of the slab strand 1 is started, the forging die is not subjected to a process such that the forging process start position of the slab strand 1 reaches the target reduction amount with a single forging pressure. It is designed to perform the forging process by dividing the amount of the pressing process into a plurality of times.By this, the contact area between the slab strand and the forging die can be reduced, and thus the required rolling capacity of the forging device can be reduced. Further, since the amount of forging processing per one time becomes small, the apparatus itself can be simplified and made compact, and the equipment cost related thereto can be advantageously reduced.

FIGS. 2 (a), (b) and (c) show the case where the forging pressure starting position of the slab strand is reduced in three steps. The reduction region at each reduction stage and the projected reduction length of the forging die 2 are shown.
Since l ₁ , l ₂ and l ₃ are all considerably shorter than the projected reduction length l _S in Fig. 1 (b), which shows the case where forging is performed with one reduction, the required reduction force is naturally reduced. Will be done.

In the forging process in the multi-strand continuous casting machine, the rolling start timing of each forging die can be shifted, as shown in Fig. 3 (a).
It is convenient to use a device as shown in (b). In the figure, the numbers 3 and 3'are positioning cylinders, 4 is an upper cylinder pedestal, 5 and 5'are joint beams, 6 is a crankshaft, and 7 and 7 '.
Is a guide column, and 8 is a drive source with a reducer,
By feeding oil to the upper and lower positioning cylinders 3 and 3'and actuating the drive source 8, the respective forging devices are structured so as to sequentially start the reduction.

However, if such a device is used to reduce the rolling start position of the cast strand to a predetermined rolling amount at one time, the load on the device is large and it is difficult to simplify it. In order to reduce hydraulic capacity, when forging pressure is started sequentially for each strand, when the tips of the strands are aligned, when a certain forging die is performing reduction processing, other forging die systems perform reduction processing. Since it does not exist, there is a disadvantage that the part pulled out at that time becomes a cut-off part that is not forged. Therefore, in the present invention, forging processing is performed according to the following procedure.

First, as shown in FIGS. 4 (a) and 4 (b), the tip (most bottom portion) of the slab strand 1 has a quality problem, so l ₀
Since the part (usually about 400 to 600 mm) is cut off as a crop, the forging pressure area is on the upstream side. Here, if the forging speed is V _C , the forging pressure period is t, and the number of reduction divisions at the forging pressure start position is n, the shift amount f for preventing the forging dies from overlapping with each other is f = V _C · t
・ It can be indicated by n.

Therefore, if the tips of the slab strands reach each forging die with a staggered distance of at least f or more, each strand is aligned with the cut-off amount l ₀ of the bottommost portion, and the decrease in yield is minimized.

Incidentally, in order to ensure the quality of the continuous casting slab obtained by continuous forging, it is necessary to reach the forging device within a certain time of the slab strand drawn from the continuous casting mold,
This control is possible by shifting the casting start time with a sliding nozzle or the like. When the start time at the time of pouring cannot be controlled sufficiently, it can be dealt with by adjusting the pouring speed within the allowable range that can ensure quality.

The above-mentioned number of times of forging processing is preferably as large as possible in order to reduce the rolling capacity in the apparatus, but from the viewpoint of slab quality, since it does not reach the target rolling amount up to n-1 times, it may become a cut-off portion. However, in practice, it is preferable to reach the target reduction amount in about 2 to 4 times.

In the case of a type in which the amount of reduction of the forging die 2 can be adjusted with a hydraulic cylinder (see Japanese Patent Application No. 63-138472), the reduction at the forging pressure starting position is performed multiple times as shown in FIG. By doing so, the feed amount S of the die per cylinder is smaller than δ / n as compared with the normal rolling reduction, so that the hydraulic capacity can be reduced to 1 / n.

Here, the hydraulic capacity refers to the maximum value of the supply flow rate of the hydraulic source, and refers to the flow rate of the hydraulic pump or, when using the accumulator together, the accumulator including the supply flow rate. In this invention, the total amount of supplied oil is the same even if the number of times of reduction is divided, but the reduction rate per one time of the mold, that is, the hydraulic flow rate (instantaneous value) of the cylinder is
Since it can be reduced to 1 / n, the required capacity of the hydraulic pump and accumulator can be advantageously reduced.

The forging die used in the present invention is not particularly limited in its shape, but a tapered one is preferable from the viewpoint of preventing internal cracking of the cast strand.

(Example) A cast strand having a thickness of 270 mm was cast at a casting speed of 0.8 m / mi.
While setting to n and performing continuous casting, forging was performed near the solidification completion point so that the target reduction amount was 50 mm on one side.

In the forging die used at this time, the angle of the inclined part was 20
The amount of movement of the die was divided into three, with the amount of one die forging being 20 mm, taking into consideration the initial clearance of 10 mm until the target amount of reduction on one side reaches 50 mm. FIG. 6 (a) shows details of the forging process procedure. As a result of the forging process according to the above conditions, the required rolling force in the forging device is about 1000 tons in the case of the conventional forging process under the same conditions as shown in FIG. It was confirmed that it could be reduced to 750 tons.

In addition, as a result of investigating the internal quality of the obtained slab, it was found that it was no different from the one subjected to forging processing according to the conventional procedure.

Next, using a 4-strand continuous casting machine, cast strands (S45C, S50C) with a thickness of 270 mm and a width of 340 mm are cast.
Forging was started according to the following conditions while casting in the range of V _C : 0.57 to 0.63 m / min (reference value V _C0 : 0.6 m / min).

Reduction amount (one side): δ = 50 mm (initial clearance 100 mm) Number of reductions: X = 3 Forging die amount adjustment cylinder feed amount per stroke: S = 20 mm Forging cycle t: 10 sec Shift amount f _min : X ・ V _C・ t = 285〜315 It is possible to set the shift amount between strands of cast slab drawn from the continuous casting mold to a value close to f _min , and the slab obtained is shown in Table-1. It was confirmed that there was no problem in quality as shown in. In addition, by making the forging pressure start position of the preceding strand earlier than usual l _{0 as} necessary, the crop length could be suppressed to the usual 600 mm even when the difference between the following strands was smaller than f _min . .

In terms of equipment capacity, the reduction force was reduced by about 25% (700 tons → 520 tons) and the hydraulic capacity (required flow rate) was reduced by about 40% compared to the case where all the strands were simultaneously reduced.

[Effects of the Invention] Thus, according to the present invention, the reduction capacity of the forging device and the capacity of the drive mechanism for setting the reduction amount of the forging die are significantly reduced without adversely affecting the internal quality of the continuous cast slab. It is possible to reduce the construction cost.

Further, according to the present invention, the cut-out portion not subjected to the forging processing can be made almost equal to the cut-out portion generated by the conventional forging processing, so that the reduction in the yield can be suppressed as much as possible.

[Brief description of drawings]

1 (a) (b), 2 (a) (b) (c) are explanatory views of the forging process according to the present invention, and 3 (a) (b) are installed in a multi-strand continuous casting machine. And FIG. 4 (a) and FIG. 4 (b) are explanatory views of the forging pressure procedure of the cast strand obtained by the multi-strand continuous casting machine, and FIG. 5 shows the main part of the forging machine. FIGS. 6 (a) and 6 (b) are diagrams showing details of forging processing in the example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Fujimura 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (no address) Inside the Mizushima Steel Works, Kawasaki Steel Co., Ltd. (72) Koichi Kushida 1-shima-shima Kawasaki, Kurashiki-shi, Okayama Prefecture Chome (No house number) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor ▲ Yoshi ▼ Moto Yoshio Mizushima Kawasaki Dori, Kurashiki City, Okayama Prefecture (No house number) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor Oil Susumu Hara 1-chome, Mizushima Kawasaki-dori, Kurashiki City, Okayama Prefecture (no address), Kawasaki Steel Co., Ltd. Mizushima Steel Works (56) References JP-A-62-192241 (JP, A)

Claims (2)

(57) [Claims] 1. A final solidification zone of a slab strand that is being drawn and moved by making a pair of casting molds vertically sandwiching a pass line of the slab strand drawn from a continuous casting mold, to make the final solidification region of the slab strand that is being drawn and moved. In the continuous forging in the direction, when the forging of the slab strand is started, the projection reduction obtained by the forging die during the single reduction is the projection reduction obtained when the target reduction amount is reached. Casting in continuous forging processing characterized by shortening the length and making the forging dies approach and separate a plurality of times so as to wrap the already processed area by the forging dies and reduce the amount to a target reduction amount. How to start forging pressure for one strand. 2. A pair of upper and lower forging dies sandwiching each pass line of a slab strand drawn from a plurality of molds arranged in parallel in a multi-strand continuous casting apparatus are brought close to and separated from each other during the drawing movement. When continuously forging the final solidification region of the slab strand in the thickness direction, when the forging process of the slab strand is started, the projected reduction length by the forging die is targeted at one reduction. Shorten the projected length obtained when rolling down to the rolling amount and make each forging die approach and separate from each other multiple times so as to wrap the known work area by the forging die, and A method for initiating forging of a slab of strands in continuous forging, characterized by shifting the forging time to a target amount of reduction.