JP4844447B2 - Joints for continuous casting of different steel types and continuous casting method of steel - Google Patents

Description

  The present invention provides a joint metal to be used for a joint portion between a preceding charge and a subsequent charge when casting a subsequent charge of different steel types in succession to the casting of the preceding charge during continuous casting operation of steel, and The present invention relates to a continuous casting method of used steel.

  In continuous casting of steel, the molten steel in the ladle is once poured into the tundish, and with a predetermined amount of molten steel staying in the tundish, the molten steel in the tundish is passed through an immersion nozzle installed at the bottom of the tundish. Are injected into each mold. In a continuous casting facility that performs such a continuous casting operation, in order to improve productivity, it is necessary to continuously cast a large number of charged molten steels without interruption. Continuous casting of a large number of charges is called continuous continuous casting (also called “continuous casting”).

  In the case of continuous casting of the same steel grade, cast continuously while changing the tundish or immersion nozzle according to the life of the tundish used (mainly the time limit for using the immersion nozzle installed at the bottom of the tundish). However, in recent small-lot, multi-product steel product configurations, continuous casting of the same steel type alone does not improve the productivity of continuous casting machines. (Referred to as “continuous casting of different steel types”).

  In the case of continuous casting of different steel types, the molten steel component in the tundish is changed by exchanging the tundish at the time when the steel type is changed, but the pre-charged molten steel exists in the mold. When the subsequent charge is injected into the mold in the state where the preceding charged molten steel exists, both are mixed in the mold. In addition, the discharge flow from the immersion nozzle also penetrates deeply into the unsolidified layer of the slab, that is, it penetrates to the lower side of the mold, so the component mixing part does not fit only in the mold, and the part below the mold Furthermore, it expands to the upper part of the mold. Naturally, this component mixing part cannot be a steel product and is scrapped. Therefore, in order to suppress this component mixing part in a narrow range, many seams made of partition iron plates have been proposed and are actually used.

In Patent Document 1, a joint metal plate composed of a flat, V-shaped, or semi-cylindrical partition iron plate and a pair of mounting rods erected on the upper surface side of the partition iron plate is provided at the bottom of the tundish. An apparatus is disclosed that is installed in a mold by a pressing bar attached to. Japanese Patent Application Laid-Open No. H10-228688 discloses a joint metal member composed of a support and a V-shaped steel material for a partition iron plate, which is provided at the lower end of the support and is stacked in a vertical direction. Japanese Patent Application Laid-Open No. H10-228667 discloses a joint metal piece formed of a partition iron plate formed in a V shape and a connecting member formed of a flat plate standing on the partition iron plate. Further, in Patent Document 4, a shielding plate having an area equivalent to the cross-sectional shape of a slab is formed by immersing one end in molten steel of the preceding charge, casting the other end in molten steel of the subsequent charge, and in the middle portion in the vertical direction. A provided seam hardware is disclosed.
JP 2004-174515 A JP 2006-239731 A Japanese Patent Laid-Open No. 2-197355 JP-A-64-83346

  In recent years, for the purpose of expanding the productivity of continuous casting equipment, carbon that has not been subject to continuous casting of different steel types due to reasons such as low strength at high temperatures, easy cracking, and risk of breakout. Almost all steel grades have become subject to continuous casting of different steel grades until reaching high carbon steel with a content of about 0.8% by mass.

  In conventional continuous casting of different steel types, it was an important issue to reduce the mixing range of components, but in the case of steel types with weak high-temperature strength, the risk of fracture at the joints is high, and the risk of fracture is low. Avoidance became the most important issue. That is, a seam fitting that secures the joint strength of the seam portion has been required. In recent years, vertical bending type continuous casting machines having a vertical portion of several meters directly under the mold have been widely used for the purpose of reducing oxide-based nonmetallic inclusions, and in particular, vertical bending type continuous casting machines. In the upper straightening band (bending portion), there is a high risk of breakage of the joint portion, and it is important to secure the joining force of the joint portion.

  From this point of view, when the above prior art is verified, the joints according to Patent Documents 1 to 3 are all intended to reduce the component mixing portion. The “strut” and the “connecting member” of Patent Document 3 cannot secure the joining force of the joint portion.

  According to the joint metal article according to Patent Document 4, the upper and lower protrusions are cast up and down in the preceding charge and the subsequent charge, and there is a possibility that the joining force of the joint part can be secured. However, it is necessary to install a “shielding plate” having an area corresponding to the cross-sectional shape of the slab at the middle part in the vertical direction of the joint piece. In the case of a slab continuous casting machine, the width of the slab exceeds 2 m. Therefore, such a large shielding plate having almost the same area as the inner space of the mold must be installed in the mold, and it must be said that installation in a short time is extremely difficult. . Note that the “shielding plate” in Patent Document 4 is not cast in the molten steel, but is a member that separates the preceding charged molten steel from the subsequent charged molten steel.

  The present invention has been made in view of the above circumstances, and the object of the present invention is easy to install in a mold, and secures the joint strength of the seam portion even in a steel type having a low high-temperature strength, Providing joints for continuous casting of different steel types that can stably carry out continuous casting of different steel types without causing operational troubles such as breakout due to breakage of the joints, and joints for continuous casting of different steel types It is to provide a method for continuous casting of steel using steel.

The joint for joint casting of different steel types according to the first invention for solving the above-mentioned problem is performed when casting a slab slab of a subsequent charge of a different steel type in succession to casting of a slab slab of a preceding charge. Continuous casting of different steel types used for the joint part of the preceding charge and the subsequent charge, in which the molten steel of the subsequent charge injected into the mold covers the solidified shell of the preceding charge to form a solidified shell to form a seam portion. It is a joint piece for use, and one end is immersed in the preceding charge and the other end is immersed in the subsequent charge, and a portion immersed in the preceding charge side of the supporting column protrudes from the long side of the mold with respect to the supporting column. includes a lower joint portion provided Te, the site to be immersed in a subsequent charge side of the strut, and the upper bonding portion provided to protrude from the mold long side with respect to the column, the seam portion reinforcement structure consisting of, One, attached to the lower end portion of the strut, partition iron plate for suppressing the mixing of molten steel, and includes a prevention plate dent collapse solidified shell attached via a connecting plate to the partition iron plate, said post, said The lower joint portion and the upper joint portion are cast and fixed to a solidified layer connected to a solidified shell formed by cooling a long copper plate, and strengthen the joint strength of the joint portion. It is.

The joint for continuous casting of different steel types according to the second aspect of the invention is the joint for reinforcing the joint of different types of steel according to the first invention, wherein the joint for different casting of the different steel types is composed of the strut, the lower joint, and the upper joint. These two sets are integrated and configured as a pair .

The joint for continuous casting of different steel types according to the third invention is the tip of the protruding portion of the lower joint when the joint for continuous casting of different steel types is installed in a mold in the first or second invention. The partition iron plate is configured to be arranged in a horizontal gap connecting the long side copper plate and the mold .

A steel continuous casting method according to a fourth aspect of the present invention is a continuous casting method of steel in which casting of subsequent charges of different steel types is performed in succession to casting of the preceding charge, and injection of the preceding charge into the mold is completed. After that, the drawing of the slab is stopped, and in this state, the joint for joint casting of different steel types according to any one of the first to third inventions is immersed in the preceding charge in the order of the column and the lower joint. Then, after the upper joint is held at a position above the molten steel surface, injection of the subsequent charge into the mold is started.

  According to the joint for joint casting of different steel types according to the present invention having the above configuration, the lower joint is cast and fixed in the molten steel of the preceding charge, while the upper joint is cast in the molten steel of the subsequent charge. In this state, even if tensile stress is applied to the seam due to straightening stress or drawing resistance of the slab, the struts function as reinforcing members and the joint strength of the seam is strengthened. Therefore, breakout caused by this crack can be prevented, and even different steel grades such as high carbon steel with low high-temperature strength can be cast continuously. It becomes possible to do. Moreover, when a partition iron plate is provided in the lower end part of the support | pillar, in addition to the said effect, a component mixing range can be reduced significantly. And since the joint material for continuous casting of different steel types according to the present invention is finally cast inside the slab, it is not necessary to strictly define the dimensional relationship with the mold, and it can be easily installed in the mold. It can be carried out.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1-3 is a figure which shows one example of embodiment of this invention, and is the schematic which shows the state which installed the joint for different steel types continuous casting which concerns on this invention in the casting_mold | template of a slab continuous casting machine, 1 is a schematic view seen from the mold short side, FIG. 2 is a schematic view seen from the mold long side, and FIG. 3 is a schematic view seen from above the mold. In these drawings, reference numeral 11 is a long mold copper plate, 12 is a short mold copper plate, 13 is molten steel, 14 is a molten steel surface, and 15 is a solidified shell.

  As shown in FIGS. 1 to 3, the joint 1 for continuous casting of different steel types according to the present invention includes a support column 2 extending in the vertical direction, and a lower joint provided at a lower portion of the support column 2 and protruding vertically from the support column 2. A portion 3 and an upper joint portion 4 provided on an upper portion of the support column 2 and projecting vertically from the support column 2. In the joint 1 according to the present invention, the lower joint 3 is immersed and fixed in the preceding charge of different steel types, the upper joint 4 is immersed and fixed in the subsequent charge, and the support 2 is joined to the joint. Play a role to increase strength. In order to increase the joint strength, in the joint hardware 1 of the present embodiment, a total of four sets of joint portion reinforcing structures composed of combinations of the support column 2, the lower joint portion 3, and the upper joint portion 4 are arranged in the width direction in the mold. Is arranged. Specifically, as shown in FIGS. 2 and 3, two pairs of seam portion reinforcing structures are paired and installed at two locations in the width direction of the slab. The two sets of joint portion reinforcing structures are integrated by two connecting members 5 attached to both side surfaces of both struts 2 and connecting members 6 attached to the upper portions of both upper joints 4. . On the upper surface side of the connecting member 6, a handle 7 is installed for conveyance or installation in a mold.

  The lower end of the column 2 extending further downward from the lower joint 3 is connected to the partition iron plate 8. The partition iron plate 8 is a combination of two steel plates welded together in a V shape, and the shape projected onto the horizontal plane is smaller than the thickness and width of the slab and can be easily immersed in an unsolidified layer in the mold. It has possible dimensions. The solidified shell falling prevention plates 9 are attached to the partition iron plate 8 at two locations in the slab width direction via connecting plates 10. The solidified shell collapse prevention plate 9 is for contacting the solidified shell 15 in the mold and preventing the solidified shell 15 from collapsing toward the inside of the mold, and when the joint 1 is installed in the mold. It is comprised so that it may be arrange | positioned in the vicinity of the molten steel surface 14 in a casting_mold | template, and is arrange | positioned in the approximate middle position of the lower junction part 3 and the upper junction part 4. FIG. The shape of the partition iron plate 8 is not limited to the V shape, and may be a flat plate shape, a semi-cylindrical shape, or the like.

The members constituting the joint 1 of the present invention are all made of steel, and the joining method of the members is joining by welding or joining by bolts or screws. Here, each dimension of the support | pillar 2, the lower junction part 3, and the upper junction part 4 is demonstrated with reference to FIG. The reason for defining the dimensions of the support column 2, the lower joint portion 3, and the upper joint portion 4 is to secure these strengths. The column 2 has a plate thickness of 20 mm to 30 mm, preferably 25 mm to 30 mm, and a width (W ₁ ) of 50 mm to 90 mm. The lower joint portion 3 has a thickness of 20 mm to 30 mm, preferably 25 mm to 30 mm, a width (W ₂ ) of 20 to 50 mm, and a length (L ₁ ) of 90 mm to 12 mm. The upper joint portion 4 has a thickness of 20 mm to 30 mm, preferably 25 mm to ₃₀ mm, a width (W ₃ ) of 30 to 70 mm, and a length (L ₂ ) of 130 mm to 170 mm. However, the length (L ₂ ) of the upper joint portion 4 is desirably determined according to the thickness of the slab, and is preferably about 90 to 100 mm smaller than the thickness of the slab. Therefore, when the thickness of the slab is, for example, 300 mm, the length (L ₂ ) may be about 200 mm.

The gap length (L ₃ ) between the lower joint 3 and the upper joint 4 is 100 mm to 160 mm. In the joint 1 of the present invention, the lower joint portion 3 must be fixed to the preceding charge, and the upper joint portion 4 needs to be fixed to the subsequent charge. When the gap length (L ₃ ) is less than 100 mm, This is because there is a possibility that the part 3 and the upper joint part 4 cannot be separately installed in the preceding charge and the subsequent charge. On the other hand, if the gap length (L ₃ ) exceeds 160 mm, the upper joint 4 may protrude into the molten steel of the subsequent charge and melt by the heat of the molten steel of the subsequent charge. When the upper joint portion 4 is dissolved, the function as an anchor is not exhibited, and the strut 2 cannot exhibit strength.

  A method of continuously casting different types of steel using the joint 1 according to the present invention thus configured will be described with reference to FIGS.

  When the injection of the preceding charge into the mold is completed, the tundish (not shown) used for casting the preceding charge is moved from above the mold. Then, the molten steel surface 14 in the mold is lowered slightly below the normal position where continuous casting is performed, and the drawing of the slab is stopped there. In this state, the joint 1 according to the present invention is prepared above the mold through human power or a charging device, and then immersed in the molten steel 13 in the mold. The partitioning iron plate 8, the support 2, and the lower joint 3 are immersed in this order, and the solidified shell collapse prevention plate 9 is in the same position as the molten steel surface 14 so that the upper joint 4 is positioned above the molten steel surface 14. Soak until. The joint 1 is held at the position such that the solidified shell fall-preventing plate 9 comes into contact with the solidified shell 15 or a solidified phase is formed around the solidified shell fall-preventing plate 9. The molten steel 13 in contact with the partition iron plate 8, the support column 2 and the lower joint portion 3 is cooled, and a solidified layer is formed around the partition iron plate 8, the support column 2 and the lower joint portion 3. Since the partition iron plate 8 has a small heat capacity, a part of the partition iron plate 8 may be dissolved.

  After that, a new tundish is placed at a predetermined position above the mold, and a subsequent charge having a molten steel composition different from that of the preceding charge is poured into the tundish from a pan (not shown), and a predetermined amount of the molten steel is charged to the tundish. When the water accumulates, injection from the tundish into the mold is started. The molten steel of the subsequent charge newly injected into the mold forms a solidified shell so as to cover the solidified shell 15 of the previous charge, thereby forming a seam portion. This seam portion is also called a “step pouring portion” because of its shape.

  When molten steel of the subsequent charge is injected into the mold and the molten steel surface 14 in the mold reaches a predetermined position, drawing of the slab is resumed. The upper joint 4 is immersed in the molten steel of the subsequent charge as the subsequent charge is injected into the mold. Then, the upper side of the support column 2 that was in contact with the space when the joint 1 is placed in the mold and the periphery of the upper joint portion 4 are cooled in contact with these, so that A solidified layer of charge is formed.

  The solidified layer formed around the support column 2, the lower bonding portion 3, and the upper bonding portion 4 is connected to the solidified shell formed by cooling the long copper plate 11, and the support column 2, the lower bonding portion 3, and the upper bonding portion. Around 4, a solidified layer is formed earlier than other portions, and the support column 2, the lower joint portion 3, and the upper joint portion 4 are cast into the solidified layer and are in a fixed state. Thereby, the lower junction part 3 and the upper junction part 4 exhibit the function as an anchor.

  After the slab drawing is resumed, the slab drawing speed is gradually increased until a predetermined drawing speed is reached. When the predetermined drawing speed is reached, casting is continued at the drawing speed. By this drawing, the joint portion, that is, the step pouring portion passes through the mold and enters the secondary cooling zone.

  The slab passing through the secondary cooling zone is subjected to tensile stress due to pulling resistance with the mold due to slab drawing, and tensile stress due to straightening for bending or unbending the slab. 3 is cast and fixed in the molten steel of the preceding charge, and the upper joint 4 is cast and fixed in the molten steel of the subsequent charge, and even if tensile stress is applied to the joint portion in this state, The support | pillar 2 functions as a reinforcement member and the joining force of a joint part is strengthened. By strengthening this joining force, cracks and cracks do not occur at the joint, and therefore breakout caused by the cracks and cracks can be prevented, and high-temperature strength such as high carbon steel is low. Even if it is a steel type, it becomes possible to carry out casting of different steel types continuously. Moreover, since the partition iron plate 8 is provided in the lower end part of the support | pillar 2, in addition to the said effect, reducing a component mixing range significantly is achieved.

  The present invention is not limited to the above description, and various modifications are possible. That is, in the above description, the two sets of the joint portion reinforcing structure composed of the combination of the support column 2, the lower joint portion 3 and the upper joint portion 4 are integrated as a pair. And may be attached to the partition iron plate 8. Further, three or more sets of the seam strengthening structures may be integrated as one.

  Further, in the above description, the joint portion reinforcing structure composed of the combination of the support column 2, the lower joint portion 3 and the upper joint portion 4 is integrated with the partition iron plate 8, but the joint portion reinforcing structure and the partition iron plate 8 are combined. It is not necessary to integrate, and it is also possible to use only the joint reinforcement structure composed of a combination of the support 2, the lower joint 3, and the upper joint 4 as the joint 1 for different steel type continuous casting. However, in this case, although the joint strength of the seam portion is strengthened, the mixing range of the molten steel components becomes wide, so that point must be noted. Therefore, when the joint portion reinforcing structure and the partition iron plate 8 are separated, first, the partition iron plate 8 to which the solidified shell fall-preventing plate 9 is attached is installed in the mold, and then the support column 2 and the lower joint portion 3 are installed. The seam reinforced structure composed of the combination of the upper joints 4 may be installed on the partition iron plate 8. The solidified shell collapse prevention plate 9 and the partition iron plate 8 do not contribute to the strengthening of the joint strength of the joint portion, so that no problem is caused even if separated. When the joint portion reinforcing structure and the partition iron plate 8 are separated, the mass of the joint 1 is reduced, and there is an advantage that it can be easily installed in the mold by human power. However, when the seam strengthening structure and the partition iron plate 8 are separated, it is preferable to integrate two or more sets of seam strengthening structures in order to ensure stability during installation in the mold. .

It is the schematic which looked at the joint metal object concerning this invention installed in the casting_mold | template of a slab continuous casting machine from the casting_mold | template short side. It is the schematic which looked at the joint metal fitting based on this invention installed in the casting_mold | template of a slab continuous casting machine from the casting_mold | template long side. It is the schematic which looked at the joint metal object concerning this invention installed in the casting_mold | template of a slab continuous casting machine from the upper direction of the casting_mold | template. It is a figure which shows the relationship of each magnitude | size of a support | pillar, a lower junction part, and an upper junction part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Joint metal | metal | money 2 Support | pillar 3 Lower joint part 4 Upper joint part 5 Connection member 6 Connection member 7 Handle 8 Partition iron plate 9 Solidification shell fall prevention plate 10 Connection plate 11 Mold long side copper plate 12 Mold short side copper plate 13 Molten steel 14 Molten steel surface 15 Solidified shell

Claims (4)

When casting slab slabs with different charge grades following the casting of slab slabs with prior charge, the molten steel with subsequent charges injected into the mold covers the solid shell of the previous charge. A joint for continuous casting of different steel types used for a joint portion of a preceding charge and a subsequent charge , forming a solidified shell to form a joint portion ,
A strut whose one end is immersed in the preceding charge and the other end is immersed in the following charge, and a lower joint provided at the portion immersed in the preceding charge side of the strut and projecting on the long side of the mold with respect to the strut A portion that is immersed in the subsequent charge side of the support column, and an upper joint provided to protrude from the long side of the mold with respect to the support column, and a seam portion reinforcing structure comprising :
And a partition iron plate for suppressing mixing of molten steel attached to the lower end of the support column, and a solidified shell collapse prevention plate attached to the partition iron plate via a connecting plate ,
The strut, the lower joint, and the upper joint are cast and fixed in a solidified layer connected to a solidified shell formed by cooling the long copper plate, and strengthen the joint strength of the joint. Features a joint for continuous casting of different steel types. The joint member for continuous casting of different steel types is formed by integrating two pairs of joint reinforcement structures composed of the support column, the lower joint, and the upper joint as a pair. The joint for continuous casting of different steel types according to 1. When the joint for continuous casting of different steel types is installed in a mold, the partition iron plate is arranged in a horizontal gap connecting the tip of the protruding portion of the lower joint and the long copper plate of the mold. The joint for continuous casting of different steel types according to claim 1 or 2, characterized in that it is formed . This is a continuous casting method of steel in which subsequent charges of different steel types are cast continuously after casting of the preceding charge, and after the injection of the preceding charge into the mold is finished, the drawing of the slab is stopped, and in this state The joint for continuous casting of different steel types according to any one of claims 1 to 3 is immersed in a preceding charge in the order of a support and a lower joint, and the upper joint is above the molten steel surface. A method for continuously casting steel, characterized by starting injection of a subsequent charge into a mold after being held in position.

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