JPS61144244A - Continuous casting installation - Google Patents

Abstract

PURPOSE:To prevent the generation of defects in a molten metal by providing heat resistance to a mold ring, forming the mold ring of a material having the heat conductivity smaller than the heat conductivity of a mold cylinder and disposing the mold ring near the position where the solidification begins in the mold. CONSTITUTION:A recess 49 is formed near the end of the mold cylinder 41 on a tundish 31 side and the mold ring 50 is press-fitted and fixed therein. The ring 50 is formed of the material having the high heat resistance and the heat conductivity lower than the heat conductivity of the cylinder 41. A molten steel 34 through a hole part 53 when a billet BL is intermittently drawn by pinch rollers 57. Since the ring 50 has the small heat conductivity, the molten steel 34 is slowly cooled. The generation of surface defects and internal defects of the billet BL is thus prevented.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a continuous casting system (q).

BACKGROUND OF THE INVENTION FIG. 9 is a simplified cross-sectional view of a prior art continuous casting facility 1. The continuous casting equipment 1 is a molten metal w1.
A refractory material 5 is provided on the inner wall surface of the tundish 3, which includes a tundish 3 for heating and storing 2, and a liquid-cooled mold 4 fixed to the tundish 3. The tundish 3 is also provided with heating means such as an induction heating coil (not shown).

In the reservoir 6 surrounded by the refractory material 5 of the tandish 3,
Molten @2 is stored and maintained in a molten state by the heating means.

A tundish nozzle 7 is provided on the mold 4 side of the tundish 3, and is closely attached to the mold 4 via a bonding ring 9 made of a heat-resistant material.

The mold 4 includes a mold cylinder 10 that is an inner cylinder, and a water-cooled jacket 12 that is an outer cylinder that is coaxial with the mold cylinder 10 and forms a space 11 between it and the mold cylinder IO. The water cooling jacket 12 is provided with a water injection hole 13 for injecting cooling water, and a discharge port 14 for discharging the cooling water that has circulated through the space 11 and has been heated. A partition member 1 is provided in the space 11.
5 is provided. The partition member 15 includes a right cylindrical portion 16 coaxial with the mold tube 10 and a support member 17 provided around the outer periphery of the right cylindrical portion 16 in the circumferential direction.

This mold tube 10 is formed from copper Cu or a copper alloy. Steel alloys include chromium (Cr) steel, beryllium (
Be) steel, Cobal) (Co) copper, etc. are used. Copper or copper alloys have high thermal conductivity, so they melt f! 42 can be easily cooled, and an increase in temperature of the mold [10 due to contact with the molten steel 2 can be suppressed. Here mold tube 1
The softening temperature of the material used for 0 is below 500C,
Thermal conductivity is 200-300 kcal/mhC.

A plate ring 18 is fixed to the end of the connecting ring 9 on the mold 4 side and fixed to the inner peripheral surface 10aK of the mold cylinder 10. The plaque ring 18 is made of, for example, boron nitride (BN) or silicon nitride (s 13N4 ).
and formed from materials such as sialon.

The molten steel 2 in the tundish 3 passes through the tundish nozzle 7 and the holes 7a, 9a of the joining ring 9, flows into the mold 4, is cooled and molded, and then drawn out. The slab 19 that is pulled out at this time is moved by pinch rollers 20 that are provided oppositely to sandwich the slab 19.
It is pulled out in the direction of arrow C1 in FIG.

FIG. 10 is a graph showing a state in which the pinch roller 20 in FIG. vj9 is driven intermittently. The pinch roller 20 intermittently moves the slab 19 forward, stops, retreats, and stops in sequence, and pulls out the slab 19 in the direction of arrow C1.

The pinch roller 20 is driven intermittently as described above, and is designed to take out the slab 19 intermittently.

11C is an enlarged sectional view of the vicinity of the tundish nozzle 7 in FIG.
It is a sectional view taken from -1 [11]. As previously mentioned,
The pinch roller 20 that pulls out the slab 19 is driven intermittently. Therefore, at time to in FIG. 10, the solidified shell 21 cooled and solidified into the shape shown in FIG.
0FI! Move at time t1 of J, and move as shown in FIG.
becomes the state of

Next, new molten steel 2 is supplied from the tundish nozzle 7 and welded to the end 21a of the solidified shell 21 on the welding ring 9 side. On the other hand, the vicinity of the outer periphery of the newly supplied molten a2 is located on the wall surface 18 of the plate ring 18 on the mold cylinder 10 side.
al and the mold cylinder 10, and the 11th
K solidifies as shown in region b1 in Figure (2). The portion b1 of the solidified shell 21 is further cooled by the mold cylinder 10. In this way, as the solidified shell 21 moves in the direction of the arrow C1 in FIG. 9, it is gradually removed by the inner circumferential surface 10a of the mold cylinder 10, and the thickness of each part thereof becomes gradually thicker.

As described above, the first plate ring 18 is in contact with the liquid-cooled mold cylinder lO, and the wall surface 18a of the plate ring 18 has a structure that is extremely easily cooled.

As mentioned above, the new melt 8 is discharged from the tundish nozzle 7.
12 is supplied and welded to the end 21a of the solidified shell 21 on the joining ring 9 side, but if this is insufficient, a so-called witness mark crack will be formed over the circumferential direction of the outer peripheral surface of the slab 19. will be formed.

The process by which this witness mark crack occurs will be explained. Referring to FIG. 11(3), the portion 11 of the end 21a of the solidified shell 21 on the connection ring 9 side is remelted by the newly supplied molten steel 2.

This molten Wi2 begins to solidify in the portion indicated by the imaginary line 22, increasing its thickness. At this time, if the temperature of the newly supplied molten copper 2 is low, or if the molten copper 91R2 is excessively cooled by the plate ring 18 or near the plate ring 18 of the mold cylinder 10, the thickness of the solidified steel Ik21 is too thick. In this case, the remaining portion of the end portion 21a/2
will not dissolve again and will burn. In such a case, gFJ12 is applied along the circumferential direction of the surface of the slab 19 that has been drawn out.
The witness mark crack 23 shown in the figure is formed.

Said part l! The lower the degree of re-dissolution of No. 1, the greater the value of the depth d of the witness mark crank shown in FIG. 13.

The slab 19 having such witness mark cracks 23 has a problem in that it is likely to cause surface defects during subsequent rolling or forging processes.

Problems to be Solved by the Invention It is an object of the present invention to solve the above-mentioned problems and to provide continuous casting equipment that can prevent the occurrence of surface defects in cast metal.

SUMMARY OF THE INVENTION The present invention provides that molten metal from a tundish is injected into
In the continuous casting equipment equipped with a cooled mold, the mold includes: a mold ring that contacts molten metal and is placed near a solidification start position; and a mold cylinder that contacts the metal that has passed through the mold ring; This continuous casting equipment is characterized in that the mold ring is made of a material that is heat resistant and has a lower thermal conductivity than the mold cylinder.

The molten metal in the working tundish flows into a liquid-cooled mold. Inside the mold, the mold and the molten metal passing through the mold are in contact.
Therefore, the molten metal in the mold is cooled and solidified starting from the outer periphery.

Here, a mold ring was provided around the axis of the mold near the end on the tundish side of the part where the mold came into contact with the molten metal. The mold ring is formed from a material that has a low thermal conductivity compared to the material that forms the portion of the mold that is in contact with the molten metal. Therefore, the molten gold m flowing into the mold from the tandish is
Unnecessarily rapid cooling can be prevented and slow cooling can be achieved.

Embodiment FIG. 1 is a simplified sectional view of continuous casting equipment 30 according to an embodiment of the present invention. A fireproof wall 32 made of a heat-resistant material such as alumina or magnesia is provided on the inner wall surface of the tundish 31 of the continuous casting equipment 30.
A solution 34 is stored in a storage part 33 within the tank 1 .

A tundish nozzle 37 made of a refractory material is provided near the bottom 36 of the tundish 31 so as to penetrate through the reservoir 33 and the outside of the tundish 31 in order to take out the molten steel 34 . A front ring 38 and a connecting ring 3 are attached to the outer end 37H of the tundish nozzle 37.
9 are respectively fixedly provided in this order. A mold 40 is provided fixed to the connection ring 39.

As shown in FIG. 1, a recess 49 is formed around the axis of the mold tube 41 near the end of the mold tube 41 on the tundish 31 side of the mold 40 having the configuration shown in FIG. A mold ring 50 is press-fitted into this recess 49 and fixed.

The inner circumferential surface 50a of this mold ring 50 is configured to integrally form a smooth inner circumferential surface with the inner circumferential surface 41a of the mold cylinder 41. That is, the mold tube 41 and the mold ring 50 constitute a mold wall 51.

A conical surface 50b whose inner diameter increases toward the tundish 31 side is formed on the inner peripheral surface of the mold ring 50 near the end on the tundish 31 side. The mold ring 50 has a uniform outer diameter in the axial direction, and the length Ll in the MM direction is equal to the length Ll of the slab BL, which will be described later.
It is made to be relatively longer, for example, 2 to 3 times longer than the amount of displacement during the period W1 in FIG.

The mold ring 50 is made of a material with low thermal conductivity but high heat resistance, such as ceramic or heat-resistant sea bream. In addition to the method of press-fitting a ring-shaped object as described above, the mold ring can be formed by thermally spraying a material into the recess 49 in the case of ceramics, or by thermal spraying or plating in the case of nails. 50 can also be formed.

The conomold ring 50 is made of a heat-resistant metal such as Inconel or Hastelloy, or ceramics.

As for ceramics, 5t3N4 type or AI! 2
03 type or BN type is used.

The thermal conductivity of heat-resistant metals and ceramics is 3 to 3, respectively.
50X10 kcal/mm, sec, C and lX
10 kcal! /mm, sec, and C are also used. Furthermore, these materials have a melting point of 1000° C. or more, which is far superior to the copper alloy used in the subsequent mold tube 41.

A plate ring 52 is provided between the mold ring 50 and the connection ring 39.

The plate ring 52 has a conical shape with a hole 53 along the axis, and a boundary 54 between a radially outer side portion 52a and an end portion 52b on the mold 40 side is the inner peripheral surface of the mold ring 50. The groove is formed so as to coincide with the boundary between the conical surface 50a and the conical surface 50b.

The slab BL pulled out from the mold 40 to the right in Fig. 1
is pulled out along the axial direction by vinci sailors 57 which are provided opposite to each other with the slab BL in between. The pinch roller 57 is driven in a state similar to that described in FIG. v110. That is, as the pinch roller 57 rotates in the direction of arrow C7, the slab BL is pulled out in the direction of arrow C5. Pinch roller 57 then stops for a predetermined period of time. Next, the pinch roller 57 rotates in the direction of arrow C6, and the slab BL is pushed back in the direction of arrow C8.Next, the pinch roller 57 stops for a predetermined period of time.The above series of operations is performed for one cycle. As a result, the slab BL is intermittently pulled out in the direction of arrow C5.

As described above, the plate ring 52 is attached via the mold ring 50 without directly contacting the water-cooled mold cylinder 41, so that it is not excessively cooled.

Therefore, the melt flowing from Tanditsh 31 @34
Naturally, when passing through the hole 53, cooling at the end 52b of a certain plaque ring 52 is suppressed at one solidification start point, and no solidification is formed on the end surface 52b.

For this reason, the lengths of /1 and /2 in Fig. 11 (3) described above are shortened, and the molten steel that has flowed in during the next stroke is completely welded, resulting in a surface with good surface quality and no witness mark cracks 23. You can get slabs.

Moreover, since the molten steel 34 is cooled slowly, it is uniformly cooled and a slab BL with good dimensions and shape can be obtained. Further, as described above, since the S solidified shell 58 is uniformly and slowly cooled, the occurrence of internal defects such as internal clutter is prevented.

FIG. 2 is a sectional view of the vicinity of the mold ring 50 of the continuous casting equipment 30 according to another embodiment of the present invention.

This embodiment is similar to the previous embodiment, and corresponding parts are given the same reference numerals. The points to note in this example are:
The outer peripheral surface 50d of the mold ring 50 has a tapered shape in which the radius of curvature gradually decreases from the tundish side to the right side in FIG. 2. That is, the mold ring 50 has a substantially conical shape having a hole 50c along the axis.

The melt 5434 that has passed through the hole 53 of the plaque ring 52 comes into contact with the mold ring wall 50a and begins to be cooled. At this time, since the mold ring 50 is formed into the above-described shape, the temperature of the inner wall surface 50a of the mold ring 50 gradually decreases from the boundary point 54 to the right side in FIG.

That is, since the molten steel 34 is gradually cooled to a stronger degree, it can be cooled slowly without being subject to rapid temperature changes.

The materials and physical properties of the mold tube 41 and mold ring 50 in this embodiment are similar to those in the embodiment shown in FIG.

Figures 4 and 13 are cross-sectional views of the vicinity of the mold ring 50 of a continuous casting installation 430 according to yet another embodiment of the present invention. This embodiment is similar to the previous embodiment, and corresponding parts are given the same reference numerals. What is noteworthy about this embodiment is that the outer peripheral surface 50d around the axis of the mold ring 50 has multiple grooves 59a, 59b, +*@, 59n(
f? The reference numeral ``a'' is 59). Further, the concave groove 59
It is installed nearby.

Therefore, the heat transfer of the mold ring 50 was made to be low near the tundish 31 and high on the side opposite to the tundish 31. As a result, supercooling of the molten fi 34 can be prevented. Continuous casting installation 3 in this example
The basic configuration of 0 and the materials forming each component are v
This is similar to the embodiment shown in Figure I1.

FIG. 4 shows a continuous casting apparatus i3 according to still another embodiment of the present invention.
FIG. 2 is a cross-sectional view of the vicinity of mold ring 5o of No. 0. This embodiment is similar to the previous embodiment, and corresponding parts are given the same reference numerals. What is noteworthy about this embodiment is that one end 6Q of the mold ring 50, whose cross section along one axis is in the shape of an abbreviated character, is welded to the t'' mold tube 41.This welding has little thermal distortion. Electron beam welding is effective.

In addition, the mold ring 50 is attached to the mold cylinder 41 as described above.
Continuously visited equipment 30 times to perform busy welding and form one piece.
When assembling the mold 41 and the mold ring 5
0 can be omitted.

The mold wall 51 configured in this way is, for example, the first
A cooling effect similar to that of the mold wall 51 in the illustrated embodiment can be achieved.

FIG. 5 is a sectional view of the vicinity of a mold ring 50 of a continuous casting equipment 30 according to still another embodiment of the present invention, and FIG. 6 is a side view of the mold ring 50 from the tundish 31 side. This embodiment is similar to the embodiment described above, and corresponding parts are provided with the same reference numerals. The noteworthy points of this example are:
The mold ring 50 is designed to have the function of a plaque ring. Part 7 rung section 61! The bolt 63 is screwed into the screw hole 64 of the mold cylinder 41 through the drilled through holes 62a, 62b, . . . , 62m.

As a result, the mold ring 50 is
It can be fixed to 1.

A protrusion 65 that protrudes radially inward around the axis is formed at the end of the inner peripheral surface 50a of the mold ring 50 on the tundish side, and this protrusion 65 has the function of a plaque ring. The outer circumferential surface 50d of the mold ring 50 is tapered from the seventh rank portion 61 side toward the opposite side of the tundish. Therefore, as described above, the mold ring 50 is connected to the mold tube 41k.
When fixing with the bolts 63, the mutually tapered outer peripheral surfaces 5°d and 41a of the mold ring 5o and the mold cylinder 41
can be contacted with great force.

Further, due to the shape of the mold ring 50, v
A slow cooling effect similar to that obtained in the embodiment shown in J2 can be obtained.

Further, as described above, since the mold ring 5o is fixed to the mold cylinder 41 with the bolt 63, only the plaque ring and the mold ring 50, which are subject to heavy wear, can be easily replaced.

FIG. 7 shows a continuous casting installation 11 of still another embodiment of the present invention.
30 is a sectional view of the vicinity of the mold ring 50. This embodiment is similar to the embodiments described above, and corresponding parts are given the same reference numerals. What should be noted about this embodiment is that the plate ring 52 shown in FIG. A layer 67 made of a heat-resistant and wear-resistant material is formed on a portion of the inner circumferential surface 41a near the mold ring 50 and on the inner circumference wJ50a of the mold ring 5o. More specifically, a recess 49 is formed near the end of the inner peripheral surface 41a of the mold f141 on the tundish 31 side. A mold ring 50 is welded to the Ni portion of the mold tube 41 on the tundish 31 side. At this time, a heat-resistant material is used for the mold tube 41,
Mold ring 50 is of similar material to that described in the illustrated embodiment.

A layer 67 made of ceramic, heat-resistant steel, or the like is formed on the recess 49 and the inner circumferential surface 41a of the mold ring 41 that is continuous with the recess 49. This ceramic and heat-resistant and wear-resistant material are the same materials as those described in the example illustrated in v11, and the method of forming them is also similar.

The portion L2 of the layer 67 thus formed functions as a plaque ring, and the portion L3 functions as a mold ring. If this layer 67 is worn out, this layer 67
You only need to repair 7.

The mold wall 51 obtained in this manner can have the same effect as that obtained in the embodiment shown in the first figure.

In this embodiment, the mold tube 41 and the mold ring 5
0, but it is also possible to form the mold tube 41 into a shape that includes the mold ring 50 and form the layer 67 of the heat-resistant and wear-resistant material on the inner circumferential surface 41a. good.

FIG. 8 shows continuous casting equipment 30 according to still another embodiment of the present invention.
FIG. 3 is a cross-sectional view of the vicinity of the mold ring 50 of FIG. This embodiment is similar to the previous embodiment, and corresponding parts are given the same reference numerals. A notable feature of this embodiment is that a heating means 68 for heating the plaque ring 52 is provided outside the plaque ring 520 in the radial direction. break ring 52
The mold tube 41 is made of the same material as in the first illustrated embodiment.

A recess 49 is provided on the tundish 31 side of the mold tube 41, and a layer 67 of ceramic, heat-resistant material, etc. is formed in this recess 49. This layer 67 serves as a mold ring. Further, a heating means 68 made of, for example, an electric resistor is provided between the plate ring 52 and the auxiliary member 55. This heating means 68 heats the break ring 52 to prevent the melt #I34 in the hole 53 from being overcooled. Further, at the end of the mold tube 41 on the tundish 31 side, a layer 6 is provided as a mold ring as described above.
7 was formed. Therefore, the end face 52 of the break ring
The R of the solidified shell formed in a can be reduced.

Therefore, the continuous casting equipment 3 having the above-mentioned configuration
0 too, 1st v! The same effect as the embodiment shown in J can be obtained. - In this example, the layer 67 may not be formed. Alternatively, the break ring 52 may be formed of a metal material such as a heat-resistant material, and the heating means 68 may be an induction fill to heat the break ring 52 by induction.

Further, in each of the above embodiments, for example, the plate ring 5
2, a stirring device (not shown) may be provided to stir the molten steel 34. The vicinity of the outer periphery of the molten steel 34 near the plate ring 52 is cooled by the tundish nozzle 37, the connection ring 39, and the plate ring 52. At this time, if the molten steel 34 is stirred by the above-mentioned stirring device, the cooled portion at the outer periphery will be mixed with the hot molten steel 34 at the center, thereby preventing overcooling of the outer periphery. can.

In addition, in each of the above embodiments, by providing the inner surface of the mold ring 50 with a taper in which the cross-sectional area becomes smaller toward the side opposite to the tundish, it is possible to cool the solidified shell 58 uniformly, and thus to uniformly cool the slab, thereby improving the cross-sectional shape accuracy. Excellent slabs can be obtained. Particularly in the case of the embodiment shown in Fig. 4\S5, mold rings with different taper amounts can be selected from the same mold 40.

Effects According to the present invention as described above, the mold ring is provided near the end of the mold cylinder on the tundish side and near the solidification start position of the molten metal.

This mold ring is made of a material with much lower thermal conductivity and higher heat resistance than the mold cylinder. Therefore, the growth of a solidified shell that is formed by cooling on the end face of the plate ring and the formation of the mold ring. As a result, it was possible to prevent surface defects and internal defects in the molten metal.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the vicinity of the mold 40 of a continuous casting equipment 30 according to an embodiment of the present invention, and FIG. 2 is a sectional view of the vicinity of the plate ring 52 of a continuous casting VN 30 of another embodiment of the present invention.
FIG. 43 is a sectional view of the vicinity of the mold ring 50 of continuous casting equipment 30 according to still another embodiment of the present invention, and FIG. 4 is a sectional view of the mold ring 50 of continuous casting equipment 30 according to still another embodiment of the present invention.
FIG. 5 is a sectional view of the vicinity of the mold ring 50 of still another embodiment of the present invention. FIG. 6 is a side view of the mold ring 50 of FIG. 5, and FIG. 7 is a still another embodiment of the present invention. FIG. 8 is a sectional view of the vicinity of the mold ring 50 of another embodiment of the present invention, FIG. 9 is a sectional view of the vicinity of the mold ring 50 of another embodiment of the present invention, and FIG. FIG. 10 is a graph for explaining the operation of the pinch roller 20 in FIG. Diagram to explain the coagulation state of 2, @
FIG. 12 is a diagram for explaining the state of surface defects in the slab 19 of FIG. 9, and FIG. 13 is a diagram for explaining the witness mark crack.

Claims (1)

[Scope of Claims] A continuous casting facility equipped with a mold into which molten metal flows from a tundish and is liquid-cooled, the mold comprising: a mold ring that is in contact with the molten metal and is placed near a solidification start position; and a mold tube with which the metal that has passed through the mold ring contacts, the continuous casting equipment characterized in that the mold ring is formed from a material that is heat resistant and has a lower thermal conductivity than the mold tube. .