JP2013223887A - Process for producing steel long product by continuous casting and rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a simpler plant design, and more cost-effective operation.SOLUTION: In a process for producing steel long products by continuous casting of steel to form billets and bloom strands (5), and subsequent rolling of the billet and bloom strand, molten steel is made to flow into a continuous casting permanent mold (3). A cast billet and bloom strand (5) are directly fed to a rolling train (20) substantially without subsequent heating. Accordingly, this makes a plant design simpler, and enables more cost-effective operation.

Description

  The present invention relates to a method for producing a long steel product according to the preamble of claim 1 and to a continuous casting permanent mold for this method.

  Cast strands produced by continuous casting are cut into individual billets or blooms, cooled to room temperature, and then reheated in a rolling mill into bar, wire, and other long steel products It is known to roll.

  It is also known to place a high-temperature (about 600 ° C.) cast billet in the rolling furnace in order to perform reheating before the subsequent rolling.

  In order to save energy and increase production, solutions have been sought for a long time that could enable continuous casting plants and rolling trains, preferably casting and rolling strands to be connected directly. .

  In this case, the throughput, speed, temperature and temperature distribution (continuous casting surface / center) at the casting plant outlet and the differences between them at the rolling row inlet are the main problems.

  The minimum feed rate at the entrance of the rolling mill train is in no case less than 4.2 m / min in order not to overload the rollers thermally due to the long contact time with the rolling stock. Furthermore, the billet at the entrance of the rolling train should have a temperature suitable for rolling (1150 to 1250 ° C.) both on its surface and at its center. In particular, the surface temperature should be distributed as uniformly as possible.

  According to EP 0 761 327 B1, a cast strand produced in a continuous caster is sent to a temperature maintenance / preheating device, which is then heated in another temperature equalization / high speed heating device before being guided to a rolling row One method is known.

  One drawback in this case is that the costs for installing and operating the reheating device are relatively high.

EP0761327B1 EP0498296B2

  The object that forms the basis of the present invention is to propose a method that allows simpler plant design and more cost-effective operation.

  According to the invention, this object is achieved by a method having the features of claim 1.

  Preferred further developments of this method according to the invention and the preferred continuous casting permanent mold for this method form the subject of the dependent claims.

  Surprisingly, as known from EP 0498296B2, when using a continuous casting permanent mold, the billet and bloom strands produced by high-speed continuous casting can be used without additional heating. It is possible to send directly to the rolling row. The mold cavity of the permanent mold for continuous casting is such that at least two contour line portions of the contour line of the cavity cross section at the end portion on the injection side of the permanent mold correspond to the contour line portion at the end portion on the strand outlet side of the permanent mold. Compared to the above, a cross-sectional expansion portion that forms a bulge is formed. The curving height of the bulge is reduced along the strand feeding direction, so that during the casting operation, the strand shell formed in the mold cavity is deformed as the permanent mold is fed, and thus In this way, uniform cooling and shell growth and uniform temperature distribution are ensured along the strand profile, which allows for high continuous casting speeds that can be introduced directly into the rolling row. Also, the temperature ratio of the cast strands at the outlet of the casting plant is suitable for introduction into the rolling row, and in any case it is possible to adjust the temperature, but no heating is required.

  Today it is practically possible to cast a strand having a square cross section in the construction range of 120 to 130 mm at a speed of about 6 m / 6 minutes. According to the shape of the permanent mold cross-section according to EP 0498296B2, a uniform temperature on the surface without the cold end which had to be heated up to now, either inductively or by a gas burner at the front of the rolling row Strands having a distribution are produced. At the same time, this configuration greatly maintains the technical casting advantage (better surface / volume ratio for the same weight per meter) of a square cross-section as opposed to a circular cross-section.

  In one particularly preferred embodiment of a continuous casting permanent mold for the method according to the invention, the outline of the substantially circular mold cavity cross section is divided into at least three outline parts of substantially the same dimensions on the injection side. Each of these outline portions has a cross-sectional extension as a bulge of the mold cavity on the injection side. The curved height of the bulge is reduced in all of the contoured portions along the direction of strand travel, at least over the partial length of the mold cavity.

  With regard to another advantageous embodiment of the continuous casting permanent mold for the method according to the invention, the outline of the polygonal, preferably square, mold cavity cross-section, on the injection side, between the corners, the mold A cavity having a profile portion having a cross-sectional extension in the form of a bulge, wherein the bulge's curved height is at least part of the length of the mold cavity, and all of the profile portion along the direction of strand travel. Reduce with.

  A method according to the invention for producing a long steel product, wherein the billet and bloom strands produced in a continuous casting permanent mold are rolled into a rolling row without substantial additional heating. A process that can be fed directly and rolled to produce a long product enables simple plant design and cost-effective operation.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. This drawing is merely schematic.

1 is a schematic view of a continuous casting plant operating according to the method according to the invention with rolling rows. FIG.

  FIG. 1 has a casting ladle 1, an intermediate container 2 (tundish), a permanent mold 3 cooled by water, and a strand bending device 6 for drawing the strand 5 by a roller 6 ′ and bending it into a horizontal state. The structure of a continuous casting plant 10 which is known per se is schematically shown. According to the invention, after this, the strand 5 is fed directly to a rolling mill row 20 having a plurality of rolling mill units 21 having rolling rollers 22. This type of rolling mill row 20 and rolling mill are known and will not be described in further detail.

  The mold cavity 3 ′ of the permanent mold 3 has at least two contour line portions of the contour line of the cavity cross section at the end portion on the injection side of the permanent mold corresponding to the contour line at the end portion on the strand exit side of the permanent mold. Compared to the portion, a cross-sectional expansion portion in the form of swelling in the mold cavity 3 ′ is formed. Details of the cross-section extension are not shown.

  The continuous casting speed of the strand 5 is at least 4.2 m so as not to exceed the permissible contact time between the strand and the roller at the entrance of the rolling mill row and therefore not inappropriately shorten the service life of the roller. Advantageously, it is / min.

  The temperature ratio at the outlet of the continuous casting plant 10 for introduction into the rolling mill train is precisely adjusted so that the strands can be rolled optimally. However, in any case, passive temperature equalization can be performed without supplying any external energy.

  The mold cavity cross section of the continuous casting permanent mold is substantially formed as a configuration having four round corners. The configuration of the four round corners is based on a square or rectangle, and has a relatively large arc-shaped radius range (radii) in the corner (corner) region. On the exit side of the strands, these arcuate radius ranges are advantageously about 20 to 40 mm in the corner region when the mold cavity cross section length or width is 120 to 180 mm.

  For example, for a 120 mm configuration with 4 round corners, an edge rounding of about 25 mm and a continuous casting speed of 5.2 m / min, and for a 180 mm 4 circle configuration, about 40 mm End rounding and a casting speed of at least 4.2 m / min can be achieved.

  The discharge portion 11 of the intermediate container 2 disposed above the permanent mold 3 is preferably a conventional slide closure 15 which is preferably a slide closing portion 15 for accurate adjustment of the amount of molten steel flowing into the permanent mold. An adjustment device is present. The adjustment of the filling level height of the molten mass in the permanent mold 3 is effected according to the inlet speed of the first rolling strand (so-called master / slave operation), for this purpose an adjusting device 13 and a filling level measuring device. 14 is provided on the permanent mold 3. With this adjustment, a substantially constant filling height should be achieved in the permanent mold. Furthermore, advantageously, in order to obtain the steel bath surface as smooth as possible in the permanent mold, a refractory immersion pipe is provided which is attached to the inflow control device and protrudes into the permanent mold.

  The cast billet strand substantially forms a configuration with four rounded corners, and the roundness of this strand corresponding to this configuration is directly due to the sufficiently high casting speed without active subsequent heating. Rolling is selected, that is, strands with the temperature distribution required for rolling are produced, in which the cast strands are sent infinitely to the mill row without being divided into pieces.

1 ladle; 2 intermediate container (tundish); 3 permanent mold; 3 'mold cavity;
5 strand; 6 strand warping device; 6 'roller;
20 rolling mill rows; 21 rolling mill units; 22 rolling rollers.

Claims (11)

Continuous casting of steel to form billet and bloom strands, and continuous rolling of these billet and bloom strands to form long products such as steel bars or steel wires A method for producing a product, wherein the molten steel is poured into a continuous casting permanent mold,
The cast billet and bloom strands are sent directly to a rolling mill row with substantially no subsequent heating,
A filling level measuring device for adjusting the filling level height of the molten steel of the permanent mold according to the speed of introduction of the strand into the rolling mill row, and further discharging the intermediate container disposed above the permanent mold The part is provided with an adjustment device, preferably a slide closure, for precise adjustment of the molten steel to be flowed into the permanent mold, and adjustment of the filling level of the molten mass in the permanent mold, A method for producing a long steel product, characterized in that it is carried out according to the speed of entry of the rolling mill row into the first roller stand.   The method of claim 1, wherein the cast billet strand substantially forms a configuration with four rounded corners.   The rounded configuration with the four round corners is such that a sufficiently high casting speed produces a strand with the temperature distribution required for rolling that can be directly rolled without active subsequent heating. The method according to claim 2, wherein the method is selected according to the configuration.   The method of claim 1, wherein the cast billet strand is in a substantially circular form. The continuous casting permanent mold forms a mold cavity that opens at both ends, and the mold cavity of the continuous casting permanent mold has at least two contours of the contour line of the cavity cross section at the end on the injection side of the permanent mold. The line portion forms a cross-sectional expansion portion that swells compared to the corresponding contour line portion at the end of the permanent mold on the strand exit side, and the curved height of the bulge is reduced along the strand feeding direction. Thus, during the casting operation, the strand outer shell formed in the mold cavity is deformed as the permanent mold is fed, and uniform cooling and shell growth and uniform temperature distribution result in the strand profile. Achieved along with the
A method according to any of claims 1 to 4, characterized in that   6. A method according to any one of the preceding claims, characterized in that the continuous casting speed is at least 4.2 m / min.   7. A method according to any one of claims 1 to 6, characterized in that commercial grade concrete steel is used.   7. A method according to any one of the preceding claims, characterized in that high quality steel is used.   The polygonal, preferably quadrangular outline of the mold cavity cross-section has an outline portion that forms a cross-sectional extension of the mold cavity in the form of a bulge at all between the corners on the injection side, 9. A bulge curved height is reduced at all of the contour portions along the direction of strand travel over at least a partial length of the mold cavity. A permanent mold for continuous casting for the method according to claim 1.   The mold cavity cross section of the continuous casting permanent mold has a quadrangular or rectangular shape, and substantially forms a configuration having four round corners with an arcuate radius range in the corner region. The permanent mold for continuous casting according to claim 9.   With respect to the continuous casting permanent mold, on the strand exit side, the arcuate radius range in the corner region is about 20 to 40 mm when the thickness or width of the mold cavity cross section is 120 to 180 mm. The permanent mold for continuous casting according to claim 10, wherein

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