JPH0336619B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a continuously cast slab production apparatus that can produce slabs free of center segregation and center porosity.

[Prior art] In recent years, in continuous casting methods, center segregation inside the slab has been dispersed and dissipated by electromagnetically stirring the unsolidified molten steel inside the slab or applying light pressure to the solidified end of the slab. Attempts have also been made to prevent bulging.

[Problems to be solved by the invention] According to the above electromagnetic stirring method and light reduction method, center segregation can be improved to some extent, but it is still incomplete, and the problem is that no improvement effect on center porosity can be expected in particular. There is.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an apparatus for manufacturing continuously cast slabs that can obtain cast unevenness without center segregation or center porosity.

[Means for Solving the Problems] A feature of the present invention is that a light rolling device is disposed on the movement line of the slab, and further downstream thereof, the slab is forged in the thickness direction immediately after solidification. It is unique in that it incorporates a press device. To be more specific, the slab drawn out from the continuous casting machine is placed downstream of the continuous casting machine from a position slightly upstream of the crater end of its liquidus line to a position slightly downstream of the crater end of its solidus line. A light reduction device is installed that reduces the thickness of the slab by an amount corresponding to the solidification shrinkage by reducing the entire area in the thickness direction.Further downstream of this light reduction device, the solid phase of the slab is It is characterized by the provision of a press device that presses the downstream side of the wire in the thickness direction.

[Operation] A liquid phase, a solid-liquid coexistence phase, and a solid phase are generated from upstream to downstream inside the slab that is moved after being guided out of the continuous casting machine. The tips of the liquidus line and solidus line, which are the boundaries between these phases, are called crater ends. In the continuously cast slab production apparatus with the above configuration, the entire area from a position slightly upstream of the crater end of the liquidus line of the slab to a position slightly downstream of the crater end of the solidus line is subjected to light reduction. The device reduces the thickness of the slab by an amount corresponding to the solidification shrinkage by reducing the thickness in the thickness direction, thereby preventing bulging and preventing the flow of highly concentrated molten steel in which solid and liquid coexist. In addition, by pressing the slab immediately after solidification in the thickness direction using a press device, center porosity (fine-grained voids) inside the slab is compressed and eliminated.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG.

In Fig. 1, 1 is a mold of a continuous casting machine;
Reference numeral 2 denotes a roller apron, from which a slab P having a thickness of about 250 mm is continuously drawn out from the mold 1.
Pa is the liquid phase inside the slab, that is, molten steel, Pb is the solid-liquid coexisting phase, Pc is the solid phase, Ea is the crater end of the liquid phase, and Ec is the crater end of the solid phase.

In this device, since the slab P solidifies and shrinks when it changes from a liquid to a solid, the solidus crater end Ec is moved downstream of the continuous casting machine from a position slightly upstream of the liquidus crater end Ea. A light rolling down device 3 is provided so that a range up to a slightly downstream position can be lightly rolled down. Further, a press device 4 is provided immediately downstream of the light reduction device 3 so that the slab P immediately after solidification can be forged.

The light reduction device 3 of this embodiment has the upper side of the forge P,
A plurality of rollers 5 are arranged on the lower side in the direction of movement of the slab P, and these rollers 5 are pressed against the surface of the slab P by a hydraulic cylinder 6 with an appropriate and predetermined force. It is. In addition, the press device 4
The anvil 7 is disposed above and below the slab P, and the anvil 7 is pushed down or pushed up by a hydraulic cylinder 8 to forge the slab P.

In the slab manufacturing apparatus having such a configuration, the following slab P is manufactured. The slab P is guided downward from the mold 1 of the continuous casting machine. Then, internal coagulation starts almost before the location where the light reduction device 3 is located. From the start of internal solidification until the entire slab is solidified, light reduction is applied by the light reduction device 3 to reduce the thickness of the slab P by an amount equivalent to solidification shrinkage. The reduced dimension is, for example, 1 mm or more for a thickness of 250 mm. Thereafter, the press device 4 presses the slab P immediately after solidification in the thickness direction to eliminate center porosity.

In this case, the compression amount (forging pressure amount) should be approximately 20 mm or more compared to 250 mm. The amount of forging pressure is set to such an extent that center porosity can be eliminated, and since this device uses a press device, extremely large reductions can be easily achieved. According to the above-mentioned slab manufacturing apparatus including the light reduction device 3 and the press device 4, the material of the manufactured slab P can be completely metallurgically sound.

That is, by lightly reducing the entire area from a position slightly upstream of the crater end Ea of the liquidus line to a position slightly downstream of the crater end Ec of the solidus line using the light reduction device 3, the metallurgical effect is as follows. First, the liquidus region (crater end Ea of the liquidus line)
The concentrated molten steel is squeezed out under light pressure in the upstream region, reducing the solute concentration.
(the part between Ea and the crater end of the solidus Ec)
Micro-segregation is finely dispersed by light reduction of the solidus region (the part downstream of the crater end Ec of the solidus line), which promotes the diffusion of micro-segregation. It will be done.

Immediately after the above-mentioned light reduction, strong reduction is performed by forging by the press device 4.
As a metallurgical effect, deformation of the center segregated grains occurs, promoting further diffusion of the center segregation, and an increase in hydrostatic compressive stress at the center of the slab P, which is effective in crimping the center porosity. It is done with purpose.

As described above, the above-mentioned device is configured to continuously perform light reduction near the crater end and subsequent forging as a series of operations, thereby achieving fine dispersion of segregation and centering. The porosity is effectively crimped and a completely metallurgically sound slab is obtained.

In addition to the above-described light reduction device 3, devices such as those shown in FIGS. 2 and 3, for example, can be used.

The one shown in FIG. 2 is of an endless track type, in which a pair of tracks 9 are arranged above and below a slab P, and a plurality of blocks 10 are attached to the outer periphery of each track 9. By pressing the peripheral surface against the upper and lower surfaces of the slab P and rotating the orbit 9 as the slab P moves, the slab P is lightly rolled down.

In addition, the one shown in FIG. 3 has a pair of block groups 11 and 12 combined in a comb-like shape on the upper and lower sides of the slab P, respectively, and these block groups 11 and 12 are alternately arranged on the upper and lower surfaces of the slab P. By pressing, the slab P is lightly rolled down.

It may be possible to use a rolling roll as the press device 4, but if the rolling roll is used, the amount of rolling cannot be made very large due to the restriction of biting, so a sufficient effect cannot be obtained. On the other hand, as mentioned above, the press device 4 using forging pressure
If this method is adopted, there is no restriction due to the biting amount as is the case with rolling rolls, so the reduction amount can be set freely and sufficiently large, and the contact length of the anvil 7 with respect to the slab P can also be reduced to the same degree as the contact distance when using rolling rolls. The center porosity can be secured to be large compared to the length, and therefore a sufficient crimp effect of center porosity can be obtained.

[Effects of the Invention] According to the device of the present invention, the light reduction device can reduce the entire area from a position slightly upstream of the clay end of the liquidus line of the slab to a position slightly downstream of the clay end of the solidus line. The slab is rolled down in the thickness direction to reduce the thickness of the slab by an amount commensurate with the solidification shrinkage, and
Since the pressing device presses the slab downstream of the crater end of the solidus line in the thickness direction, center segregation and center porosity can be effectively prevented. Furthermore, since the center porosity can be improved immediately after solidification, the amount of rolling reduction in the subsequent rolling process can be reduced, and the number of stands can be reduced.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing one embodiment of the present invention, and FIGS. 2 and 3 are side views showing other examples of the light reduction device. P...Slab, Pa...Liquid phase, Pb...Solid-liquid coexistence phase,
Pc...solid phase, Ea...crater end of liquid phase, Ec
... solid phase crater end, 1 ... mold of continuous casting machine, 3 ... light reduction device, 4 ... press device.

Claims (1)

[Claims] 1. Downstream of the continuous casting machine, cast slabs drawn out from the continuous casting machine are spread over the entire area from a position slightly upstream of the crater end of the liquidus line to a position slightly downstream of the crater end of the solidus line. A light reduction device is installed that reduces the thickness of the slab by an amount equal to the solidification shrinkage by rolling it down in the thickness direction, and further downstream of this light reduction device, a crater at the solidus line of the slab is installed. A continuous slab manufacturing device characterized by being equipped with a press device that presses the downstream side of the end in the thickness direction.