Casting method

Abstract

To provide a stopper for casting which is low in replacement frequency in a long life, and can reduce total cost by long-term operation.SOLUTION: A stopper 4 for casting is liftably provided so as to be inserted from above a container 1 storing a molten steel when outflowing molten steel 2 through a nozzle 3 provided in a bottom part of the container 1 from the container 1, injecting the molten steel 2 into a casting mold 8 provided below the container 1 and performing casting, and opens / closes the nozzle 3 and injects the molten steel 2 to the casting mold 8 from the container 1 and stops the injection. The stopper 4 for casting is formed of an alumina-carbon-based refractory, is constituted as an integrated object, and the shape of the tip has an R shape adapted to the nozzle 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention is a casting Regarding the manufacturing method. [Background technology]

[0002] During casting, the molten metal flows out of a molten metal container through a nozzle formed at the bottom of the container and is poured into a mold. To stop the molten metal from flowing out of the nozzle, the nozzle is closed with a casting stopper made of a refractory material (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 59-87968 Summary of the Invention [Problem to be solved by the invention]

[0004] When producing cast steel, molten steel at high temperatures of around 1500 to 1600°C is used as the molten metal, so casting stoppers are made of relatively inexpensive refractory bricks, such as ZrO2-SiC bricks, which are heat-resistant to molten steel and are replaced once per use as consumables. Furthermore, because this type of refractory brick has low strength, the casting stopper is made up of multiple divided pieces bonded together.

[0005] However, even if the refractory bricks constituting the casting stopper are inexpensive, if the casting stopper is replaced each time, the total cost may become high due to the cost of the refractory material and the labor cost for assembling the casting stopper, when considering long-term operation.

[0006] The present invention is long The object of the present invention is to provide a casting method that can reduce the total cost of long-term operation. [Means for solving the problem]

[0007] The present invention provides the following means (1) to (5).

[0008] (1) A casting method comprising storing molten steel in a vessel, causing the molten steel to flow out of the vessel through a nozzle provided at the bottom of the vessel, and pouring the molten steel into a bottomed mold provided below the vessel, a casting stopper made of an alumina-carbon refractory material and configured as an integral body, the tip of which has an R-shaped end conforming to the nozzle, the casting stopper being inserted into the container from above and attached to a liftable arm; lowering the casting stopper via the arm and storing molten steel in the vessel with the casting stopper closing the nozzle; raising the casting stopper to inject the molten steel in the vessel into the bottomed mold provided below the vessel for casting; and A casting method characterized by repeating multiple times the steps of storing molten steel in the vessel and pouring the molten steel in the vessel into the bottomed mold of the vessel to cast it without replacing the casting stopper.

[0009] (2 )one After the completion of the first casting, the casting stopper is removed, the tip of the casting stopper is ground to have an R shape that fits the nozzle, and the ground casting stopper is attached to the nozzle, and the next casting is performed. (1) Casting method.

[0010] (3) A casting method according to (2), characterized in that after one casting run is completed, the tip of the casting stopper is kept raised from the nozzle, and after cooling, the casting stopper is removed.

[0011] (4) A casting method according to (2) or (3), characterized in that the casting stopper is attached to the arm via a core material by a nut, and the casting stopper is fixed when the nut is removed.

[0012] (5) Using one of the casting stoppers The casting is carried out , the casting stopper was removed Each time, The tip of the casting stopper Lengthwise The wall thickness was measured and The aforementioned The casting method according to any one of (2) to (4), characterized in that repeated use of the casting stopper is stopped when the wall thickness becomes less than 10 mm. [Effects of the Invention]

[0013] According to the present invention Ba, longA casting method is provided that can reduce the total cost of production. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a cross-sectional view showing a state in which molten steel is poured into a mold for casting. [Figure 2] 1 is a cross-sectional view showing a casting stopper according to an embodiment of the present invention. [Figure 3] FIG. 1 is a front view showing a conventional casting stopper. [Figure 4] 10 is a photograph showing the appearance of a casting stopper of a comparative example after one charge of casting. [Figure 5] 10 is a photograph showing the appearance of the casting stopper of the example after casting 30 charges. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below. FIG. 1 is a cross-sectional view showing a state in which molten steel is poured into a mold for casting.

[0016] Vessel 1 is a vessel in which molten steel 2 is stored, and is constructed by lining a refractory material on a steel shell. A nozzle 3 for discharging the molten steel 2 is provided at the bottom of vessel 1. A casting stopper 4 for closing the molten steel outlet hole of nozzle 3 is provided inside vessel 1. Casting stopper 4 is supported by an arm 5, and arm 5 is configured to be raised and lowered together with casting stopper 4 along a support column 6 outside vessel 1 by an elevating mechanism (not shown). The molten steel in vessel 1 is formed by melting scrap, ferroalloy, etc., using, for example, high-frequency heating. All steel types typically used as cast steel are applicable, regardless of the steel type.

[0017] A mold 8 is provided below the container 1. The mold 8 is formed by mixing molding materials consisting of sand, resin, hardener, etc. in a continuous mixer, filling the mixture into a metal frame 9 with a model inserted therein, and setting a core.

[0018] As shown in FIG. 2, the casting stopper 4 is shaped like a long rod (for example, about 800 to 1000 mm in length and 90 to 110 mm in diameter), with a hole 4a formed in the center along the longitudinal direction, and a core material 11 inserted into the hole 4a. The upper part of the core material 11 is attached to the arm 5 with a nut 7. In other words, the casting stopper 4 is attached to the arm 5 via the core material 11 with the nut 7. A spacer 12 is interposed between the arm 5 of the core material 11 and the casting stopper 4.

[0019] The casting stopper 4 is made of an alumina-carbon refractory material and is constructed as a single unit. The tip of the casting stopper 4 has an R-shape (e.g., R50) that fits the nozzle 3 so that the nozzle 3 is not blocked by the molten steel 2 flowing into the tip of the casting stopper 4, or so that the molten steel does not flow out.

[0020] The alumina-carbon refractory material constituting the casting stopper 4 preferably has a composition of 30-35 mass% carbon (C) and 57-62 mass% alumina (Al2O3). Silicon carbide (SiC) may also be added in a range of 4.0-5.0 mass%. The total amount of C and Al2O3 is 87-97 mass%, with the remainder consisting of SiC, if added, and unavoidable impurities. The unavoidable impurities include Cr, Fe, Mn, etc. Furthermore, the thickness of the tip of the casting stopper 4 during use is preferably 10 mm or more. This makes it possible to reduce the likelihood of damage to the casting stopper 4 during casting.

[0021] When the molten steel 2 in the vessel 1 is poured into the mold 8 for casting, the nozzle 3 is closed by the casting stopper 4, and the mold 8 is positioned below the vessel 1. Next, the casting stopper 4 is raised by an elevation mechanism (not shown), and the nozzle 3 is opened as shown in FIG. 1, and the molten steel 2 in the vessel 1 is poured into the mold 8.

[0022] After the molten steel 2 has been poured into the mold 8, the casting stopper 4 is lowered to close the nozzle 3, thereby completing the casting process.

[0023] This type of casting is performed repeatedly for one container, but conventionally, it has been common practice to replace the casting stopper after each casting, and the casting stopper has been made of a relatively inexpensive refractory brick, such as a ZrO2-SiC refractory brick, that has enough fire resistance to withstand a single casting. Furthermore, this type of refractory brick is not strong enough to form a long casting stopper as a single unit, so as shown in Figure 3, the casting stopper 4' is made up of multiple divided pieces (three sleeves 21 and a head 22) bonded together.

[0024] However, even if the refractory bricks constituting the casting stopper are inexpensive, if the casting stopper is replaced each time, the cost of the refractory material will be high when long-term operation is taken into consideration. In addition, when the labor cost for assembling the casting stopper is added, there is a risk that the total cost will be high.

[0025] Therefore, in the present invention, contrary to conventional technical wisdom, the casting stopper is designed to have a long life and be used repeatedly. An alumina-carbon refractory, which has higher heat resistance and strength, is used as the material for the casting stopper, and the casting stopper is constructed as a single unit. That is, although the alumina-carbon refractory is expensive in terms of material cost, it has a longer life than conventional refractory bricks and can be used repeatedly. Furthermore, because the casting stopper is constructed as a single unit, assembly work for the casting stopper is not required. This makes it possible to reduce the total cost for long-term operation below the cost of the conventional refractory plus the labor cost for assembling the casting stopper.

[0026] Next, a casting method using an alumina-carbon refractory material as the casting stopper will be described.

[0027] As described above, with the mold 8 positioned below the vessel 1 containing the molten steel 2 and the nozzle 3 blocked by the casting stopper 4, the casting stopper 4 is raised to pour the molten steel 2 into the mold 8, performing one casting. The casting stopper 4, which had been attached to the arm 5 via the core 11 with the nut 7, is then removed from the arm 5 by removing the nut 7. The appearance of the casting stopper is checked, and if there are no problems, the R shape of the tip of the casting stopper 4 is polished to match the nozzle 3, for example, to an R of 50. The casting stopper 4 is then reattached to the arm 5 via the core 11 with the nut 7, and the next casting is performed. This casting process is repeated multiple times.

[0028] When grinding the tip of the casting stopper 4, if its R shape does not fit the nozzle 3, for example, if the R of the tip becomes too small, molten steel 2 will flow into the space between the casting stopper 4 and the nozzle, and at the time of the next casting, the remaining molten steel will solidify, causing an inconvenience in that the molten steel will not flow out of the nozzle 3 even if the casting stopper 4 is raised.

[0029] It is preferable to measure the thickness of the tip of the casting stopper 4 each time it is removed, and continue to use it if the thickness is 10 mm or more, and stop using it if it is less than 10 mm. The thickness of the tip of the casting stopper 4 can be determined by measuring the total length of the casting stopper 4 after polishing.

[0030] After casting is completed, it is preferable to move the casting stopper 4 above the nozzle 3 and hold it there, and then remove the slip casting stopper 4 after it has cooled. This is because if the nozzle 3 is kept closed with the casting stopper 4 after casting, the tip of the casting stopper 4 may be welded to the nozzle 3, and the casting stopper 4 may break when it is removed.

[0031] When removing the nut 7 that fastens the casting stopper 4, it is preferable to remove it while the casting stopper 4 is fixed. This is because if the nut 7 is tightly fastened when removing it, the casting stopper 4 may rotate when turning the nut 7, which may cause force to be applied to the casting stopper 4 and result in breakage. The casting stopper 4 can be fixed by clamping the support column 6 with an appropriate jig, for example.

[0032] As described above, in this embodiment, an alumina-carbon refractory having higher heat resistance and strength is used as the material for the casting stopper 4, and the casting stopper 4 is constructed as a single unit. After each casting run, the casting stopper 4 is removed and polished so that the R-shaped tip of the stopper fits the nozzle 3. This prevents problems such as molten steel solidifying between the nozzle 3 and the casting stopper 4 or the casting stopper 4 failing to stop the outflow of the molten steel 2, resulting in leakage of the molten steel 2. In this way, the casting stopper can be repeatedly used for a desired number of casting runs, and the labor costs associated with assembling the casting stopper are eliminated. Therefore, considering long-term operation, the total cost can be reduced compared to the conventional method, which requires replacing the stopper after each casting run and assembling the casting stopper.

[0033] Furthermore, when the casting stopper 4 is used repeatedly, the thickness of the tip of the casting stopper 4 is measured each time the casting stopper 4 is removed, and if the thickness is 10 mm or more, repeated use is continued, and if the thickness is less than 10 mm, repeated use is stopped, thereby making it possible to reliably grasp the limit of repeated use of the casting stopper 4.

[0034] Furthermore, after casting is completed, the casting stopper 4 can be moved and held above the nozzle 3, and then removed after it has cooled. Alternatively, the casting stopper 4 can be removed while being fixed in place, thereby avoiding the problem of the casting stopper 4 breaking, and increasing the number of times the casting stopper 4 can be reused, up to 30 times or more, thereby further reducing the total cost. [Example]

[0035] Examples of the present invention will be described below. Here, the steel types used for casting were 0.5Cr1MoFC, a cast iron, SCH11, a heat-resistant steel, and TNCM-1, a high-alloy steel.

[0036] First, a comparative casting stopper having the structure shown in Fig. 3 was fabricated using ZrO2-SiC refractory bricks with a composition of 40-50 mass% SiC and 40-50 mass% ZrO2, and casting was carried out with molten steel of the above steel type in a vessel using the casting stopper. As a result, as shown in the photograph in Fig. 4, the comparative casting stopper suffered from corrosion, oxidation, impregnation of elements, etc., and could not be used repeatedly.

[0037] In contrast, an example casting stopper of the one-piece construction shown in Fig. 2 was produced using an alumina-carbon refractory having a composition of 30-35 mass% C, 57-62 mass% AlO, and 4.0-5.0 mass% SiC, and casting was carried out with molten steel of the above steel type in a vessel using the casting stopper. As a result, no melting damage, oxidation, impregnation of components, etc. were observed in the example casting stopper.

[0038] Next, a one-piece casting stopper made of alumina-carbon refractory was repeatedly used for casting multiple charges. Before repeated use, the casting stopper was removed from the vessel and polished so that the R shape of the tip of the casting stopper became R50, which matched the nozzle 3. This enabled the casting stopper to be repeatedly used for casting more than 10 charges without causing nozzle clogging or molten steel leakage.

[0039] When the casting stopper was removed after 20 charges, it broke. Analysis revealed no inclusion of elements such as base metal or slag on the cross section of the casting stopper, and it was confirmed that no cracks existed before the breakage. Therefore, it was speculated that the cause of the breakage of the casting stopper was welding between the casting stopper and the nozzle after casting and before removal. In addition, when the nut was removed after 20 charges, the nut was tightly tightened, so force was applied to the casting stopper, causing it to break.

[0040] To prevent breakage of the casting stopper due to welding between the casting stopper and the nozzle, the casting stopper is moved and held above the nozzle after casting is completed, and is removed after cooling. Also, to prevent force from being applied to the casting stopper when removing the nut, the casting stopper is fixed while the nut is removed. As a result, breakage of the casting stopper is prevented.

[0041] After taking the above measures, the thickness of the tip of the casting stopper was measured when it was removed, and when the thickness was less than 10 mm, it was determined that the casting stopper had reached the end of its life and repeated use was discontinued.

[0042] As a result, by using the casting stopper of the example, which is a one-piece body made of an alumina-carbon refractory, it was possible to perform casting of 30 or more charges. As shown in the photograph in Figure 5, the casting stopper of the example showed almost no melting damage even after casting of 30 charges, and was in a usable condition. [Explanation of symbols]

[0043] 1; Container 2. Molten steel 3; Nozzle 4. Casting stopper 5; Arm 6;Support pillar 7; Nut 8;Mold 9;Gold frame 11; Core material

Claims

1. A casting method comprising storing molten steel in a vessel, causing the molten steel to flow out of the vessel through a nozzle provided at the bottom of the vessel, and pouring the molten steel into a bottomed mold provided below the vessel, a casting stopper made of an alumina-carbon refractory material and configured as a single unit, the tip of which has an R-shaped end that fits the nozzle, the casting stopper being inserted into the container from above and attached to a liftable arm; lowering the casting stopper via the arm and storing molten steel in the vessel with the casting stopper closing the nozzle; raising the casting stopper to inject the molten steel in the vessel into the bottomed mold provided below the vessel for casting; and A casting method characterized by repeating multiple times the steps of storing molten steel in the vessel and pouring the molten steel in the vessel into the bottomed mold of the vessel to cast it without replacing the casting stopper.

2. A casting method as described in claim 1, characterized in that after one casting is completed, the casting stopper is removed, the tip of the casting stopper is ground so that its shape becomes an R-shape that fits the nozzle, the ground casting stopper is attached, and the next casting is performed.

3. 3. The casting method according to claim 2, wherein after one casting run is completed, the tip of the casting stopper is maintained in a raised position from the nozzle, and the casting stopper is removed after being cooled.

4. 4. The casting method according to claim 2, wherein the casting stopper is attached to the arm by a nut via a core member, and the casting stopper is fixed when the nut is removed.

5. The casting method according to any one of claims 2 to 4, characterized in that the casting is performed using one casting stopper, the thickness of the tip of the casting stopper in the longitudinal direction is measured each time the casting stopper is removed, and repeated use of the casting stopper is stopped when the measured thickness becomes less than 10 mm.

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