JP5958810B2 - Ingot casting method - Google Patents

Description

  The present invention relates to an ingot casting method, and more particularly to an ingot casting method that can reduce defects in a steel ingot generated in a mold when a molten metal is poured from below into a ingot mold through a runner. .

  The so-called bottom casting, in which the molten metal in the ladle is poured into the mold from the inlet provided on the bottom of the ingot casting mold through the runner, causes defects due to mixing of gas and foreign matter compared to top casting. It is known as a difficult ingot casting method.

  In Patent Document 1, in continuous casting, the molten steel weight in the tundish is measured, and the amount of molten steel injected from the ladle into the tundish is controlled so that the rate of increase of the molten steel maintains a predetermined value. A control device is shown.

JP-A-5-50203

  By the way, in the above pouring casting, the injection of molten metal is conventionally performed by manual operation based on the experience of field workers, but it is problematic that defects such as inclusion defects and surface cracks occur in the manufactured steel ingot. The solution was requested.

  Therefore, the present invention solves such problems, and an object of the present invention is to provide an ingot casting method that can effectively prevent the occurrence of defects such as inclusion defects and surface cracks in bottom casting.

Inclusion defects, surface cracks, and other defects are mainly caused by film breakage or winding of ingot powder during casting, or by indefinite speed casting. Therefore, in the first invention, a valve body (21) for opening and closing the top is provided at the pouring spout (11) on the bottom of the ladle, and the bottom of the ingot casting mold (4) from the pouring spout (11) through the runner (32) In the pouring type ingot casting method in which molten metal is supplied from the inlet (41) to the ingot casting mold (4), the valve element (21) is fully opened in the initial casting step (I). In the subsequent bottom drawing step (II), the valve body (21) is closed to a predetermined opening, and in the subsequent main body casting step (III), the critical surface flow velocity of the molten metal in the ingot casting mold (4) is the critical velocity. The valve body (21) is controlled to be opened and closed so as to maintain the hot water rising speed so as to be contained within the hot water rising process (IV) after the main body casting process (III), and the hot water rising speed in the main body casting process (III). to open and close control the valve body (21) so as to maintain a smaller rate than In addition, a plurality of the ingot casting molds (4) are provided, and it is detected whether or not the molten metal (M) in the ingot casting mold (4) has reached the hot water level at the start of the hot water and the full hot water surface level. A single hot-water surface detection sensor (6) is provided, and the hot-water surface detection sensor (6) is movably held in the three-dimensional space by the movement driving means (D), so that each ingot mold (4) It can be moved to a position directly above.

In the first invention, hot water clogging in the runner is prevented in the initial step. Then, the bottom jet flow is suppressed in the subsequent bottom drawing step, and further, the surface flow rate of the molten metal is suppressed in the main body casting step, thereby preventing film breakage or entrainment of the agglomerated powder. And in a main body casting process and a hot-water-feeding process, the pouring speed is controlled to a fixed speed. By performing such a process, the occurrence of inclusion defects and surface cracks in the cast ingot, segregation at the top of the ingot, pipe defects, and the like is effectively prevented. Moreover, the molten metal level in several ingot casting molds can be detected with a single molten metal level detection sensor.

  The reference numerals in the parentheses indicate the correspondence with specific means described in the embodiments described later.

  As described above, according to the ingot casting method of the present invention, it is possible to effectively prevent the occurrence of defects such as inclusion defects and surface cracks.

It is a fragmentary sectional side view which shows the whole structure of the ingot forming apparatus which enforces this invention method. It is a schematic side view of the agglomeration apparatus which attached the movement drive means to which a hot_water | molten_metal surface detection sensor is moved. It is a schematic plan view of the agglomeration apparatus which attached the movement drive means to which a hot_water | molten_metal surface detection sensor is moved. It is a figure which shows the relationship between a hot water rising speed and the surface flow velocity of a molten metal. It is a figure which shows the time-dependent change of the casting speed controlled by a control apparatus.

The embodiment described below is merely an example, and various design improvements made by those skilled in the art without departing from the gist of the present invention are also included in the scope of the present invention.
FIG. 1 shows the configuration of an ingot forming apparatus for carrying out the method of the present invention. In FIG. 1, a ladle 1 is provided with a pouring port 11 on the bottom surface, and the pouring port 11 is opened and closed by a slide nozzle 21 as a valve body. Immediately below the pouring port 11, the upper end of the injection pipe 31 erected on the surface plate 3 is open, and the lower end of the injection pipe 31 communicates with the runway 32 formed in the surface plate 3. .

  A plurality of runners 32 are branched and formed (one of them is shown in FIG. 1), and the ends of each runner 32 open to the bottom surface of each ingot casting mold 4 installed on the surface plate 3. It communicates with the inlet 41. The molten metal M in the ladle 1 opens the slide nozzle 21 of the pouring spout 11 to reach the inlet 41 on the bottom of each ingot mold 4 from the injection pipe 31 through the runner 32, and into the ingot mold 4 from below. Is poured into (bottom pour).

  The ladle 1 is provided with a load cell 51 for detecting its weight, and its output signal is inputted to the control device 5. In the control device 5, the change in the amount of remaining hot water in the ladle 1 is measured from the output signal, and the casting speed in each ingot casting mold 4 is calculated based on this change. A drive cylinder 22 is connected to the slide nozzle 21, and the slide nozzle 21 is opened and closed by the output signal of the control device 5 via the drive cylinder 22. The opening degree of the slide nozzle 21 is fed back to the control device 5 by the opening degree detection sensor 23.

  A molten metal level detection sensor 6 is located above the ingot casting mold 4, and the molten metal level detection sensor 6 detects the molten metal level of the molten metal M in the ingot casting mold 4 and controls it based on the detection signal. In the apparatus 5, it is determined whether or not the molten metal M has reached a level of hot water or full injection. The molten metal level detection sensor 6 is shared by the plurality of ingot casting molds 4. More specifically, for example, an eddy current distance sensor is used as the molten metal level sensor 6, and the molten metal level sensor 6 can be moved up and down suspended downward from the traveling carriage 7 constituting the movement drive means D as shown in FIG. The push-pull chain 71 is held at the lower end.

  As shown in FIG. 3, the traveling carriage 7 is placed on a parallel sub-rail 72 and is movable along the sub-rail 72. The sub-rail 72 has a plurality of structures arranged on one side of the ladle 1. It is supported by guide rails 73 extending in parallel on both sides of the lump mold 4 so as to be movable along this. Thereby, the hot-water surface sensor 6 can move freely in the three-dimensional space that covers the mold arrangement region on one side of the ladle 1.

  In the present embodiment, as shown in FIG. 3, ten ingot casting molds 4 are arranged on the surface plate 3, and five of these are positioned symmetrically. The runners 32 (FIG. 1) leading to the respective ingot casting molds 4 can be appropriately blocked at the portion communicating with the mold 4 when the molten metal level in each mold 4 rises to the full injection level. Yes.

  When the ingot-making process is started, the controller 5 causes the traveling carriage 7 to be positioned directly above the first ingot-molding mold 4, and the molten-metal level detection sensor 6 can detect the molten-metal level in the ingot-molding mold 4. The molten metal surface height is measured. When the measurement is finished, the hot water level detection sensor 6 is raised and the traveling carriage 7 is moved to a position immediately above the next ingot casting mold 4. Then, the molten metal level detection sensor 6 is lowered to a predetermined position where the molten metal level can be detected, and the molten metal level is measured.

  In this way, for the five ingot molds 4 within the movable range of the traveling carriage 7, the measurement of the molten metal surface height of any one mold 4 is sequentially repeated for each group of different molten metal surface heights. . Then, when it is detected that a predetermined level of hot water or full hot water is reached, the molten metal is replenished or supplied, or the hot water passage 32 leading to the mold 4 is blocked and the supply of the molten metal is stopped. Here, only the molten metal level of the ingot casting mold 4 in the right half part of FIG. 3 within the movable range of the traveling carriage 7 is measured, but the same shaped mold 4 at the symmetrical position in the left half part is also usually used. Since the level of the molten metal is the same, the same operation is performed on the corresponding ingot casting mold 4 in the left half when the molten metal supply is shut off due to the filling of each mold 4 in the right half or full filling. .

  By the way, the cause of film breakage or entrainment of the agglomerated powder is that the surface flow velocity of the molten metal M in the agglomerated mold 4 becomes excessive. The surface flow velocity is proportional to the hot water rising speed in the ingot casting mold 4. Therefore, as shown in FIG. 4, if the hot water rising speed is suppressed to a critical hot water speed corresponding to the critical surface flow velocity that causes film breakage or entrainment of the agglomerated powder as shown in FIG. Generation of defects such as defects and surface cracks can be prevented. Note that the pouring speed eventually has a one-to-one correspondence with the casting speed, and managing the pouring speed manages the casting speed.

  FIG. 5 shows the change over time in the casting speed due to the opening control of the slide nozzle 21 performed by the control device 5 in the ingot forming process. In the initial process I of the ingot-making process, the slide nozzle 21 is fully opened in order to prevent hot water clogging in the runner 32. Therefore, during this time, the casting speed is not substantially controlled, and the casting speed is set according to the amount of molten metal injected from the fully opened slide nozzle 21.

  In the bottom throttling step II subsequent to the initial step I, the opening of the slide nozzle 21 is set to, for example, 40% to 80%, preferably 50% to 70%, and the bottom jet flow from the inlet 41 of the ingot casting mold 4 is performed. Suppress. Also in this case, the casting speed is not substantially controlled, and the casting speed is set according to the amount of molten metal injected from the slide nozzle 21 having a predetermined opening. If the opening of the slide nozzle 21 is smaller than 40%, hot water may be clogged, and if the opening is larger than 80%, there is a risk that the film of the agglomerated powder may be cut or caught.

  In the main body casting process III subsequent to the bottom drawing process II, the opening degree of the slide nozzle 21 is controlled so as to obtain a hot water rising speed equal to or lower than the critical hot water rising speed, that is, a casting speed. As a result, it is possible to avoid defects such as inclusion defects and surface cracks in the cast steel ingot body.

  In the hot water casting process IV following the main body casting process III, the opening of the slide nozzle 21 is set so that the casting speed is 10 to 60%, preferably about 30% of the casting speed in the main body casting process III until full casting. To control. This prevents segregation of the top of the steel ingot cast and occurrence of pipe defects.

DESCRIPTION OF SYMBOLS 1 ... Ladle, 11 ... Pouring spout, 21 ... Slide nozzle (valve), 3 ... Surface plate, 32 ... Runway, 4 ... Ingot casting mold, 41 ... Inlet, 5 ... Control device, 6 ... Hot water level detection Sensor: 7 ... Moving carriage, D ... Movement drive means, I ... Initial process, II ... Bottom drawing process, III ... Main body casting process, IV ... Feeding water process.

Claims (1)

A pouring type ingot that has a valve body that opens and closes it at the pouring port on the bottom of the ladle and supplies molten metal from the pouring port through the runner to the ingot casting mold. In the casting method, the valve body is fully opened in the initial casting process, the valve body is closed to a predetermined opening in the subsequent bottom drawing process, and the critical surface flow velocity of the molten metal in the ingot casting mold in the subsequent body casting process. The valve body is controlled to open and close so as to maintain the hot water rising speed within the critical speed, and the hot water rising speed after the main body casting process is maintained at a speed lower than the hot water rising speed in the main body casting process. The valve body is controlled to be opened and closed , and a plurality of the ingot casting molds are provided, and it is detected whether or not the molten metal in the ingot casting molds has reached the hot water level at which the hot water starts and the full hot water surface level. Single hot water level detection Capacitors are provided, the molten metal surface detection sensor is held movable in three-dimensional space by moving the drive means, ingot-making method of casting adapted to be moved to a position immediately above each ingot mold.

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