Molten iron spheroidizing inoculation method and device in centrifugal casting process of nodular cast iron pipe

Abstract

The invention discloses an iron liquid spheroidizing inoculation method and device in the centrifugal casting process of a nodular cast iron pipe. According to the method, in the centrifugal casting process of the nodular cast iron pipe, a nodulizing inoculant is fed into a throat pipe through a core-spun yarn, molten iron is continuously fed into the core-spun yarn when entering the throat pipe, the nodulizing inoculant enters the throat pipe along with the molten iron, and the molten iron carries the nodulizing inoculant to absorb the nodulizing inoculant in the process of flowing through the throat pipe to achieve nodulizing inoculation; the device comprises a sprue cup, a throat pipe, a runner and a molten iron pouring device, the bottom of the sprue cup is connected with the throat pipe, an outlet of the throat pipe is connected with the runner, and a wire feeding device and the molten iron pouring device are arranged above the sprue cup. The spheroidizing inoculant is absorbed in the throat pipe in the process of flowing along with iron liquid in a cored wire mode, stream spheroidizing inoculation is achieved, the absorptivity of the spheroidizing inoculant is improved, the spheroidizing technological process is shortened to the maximum extent, spheroidizing decline is avoided, the adding amount of the spheroidizing inoculant is reduced, and production efficiency is improved.

Description

Technical Field

[0001] The invention relates to a method and a device for spheroidizing and inoculating molten iron during the centrifugal casting of a ductile iron pipe, belonging to the technical field of spheroidizing and inoculating molten iron. Background Art

[0002] In the current production process of ductile iron pipes, the spheroidization and inoculation treatment of molten iron is currently completed through a specially set up spheroidization treatment station, generally using the following process technologies.

[0003] 1. The flushing method: Processing temperature ≥ 1400°C; suitable for processing large quantities of molten iron, generally exceeding 3 tons per batch. Suitable for alloys with a magnesium content of less than 15%. Using a pit or dam-type spheroidizing ladle, the process can process 0.5-3 tons of molten iron at a temperature of 1400-1430°C. The particle size of the spheroidizing agent should be 10-30 mm, and the mass fraction of the powder should not exceed 10%. Place the spheroidizing agent at the bottom of the ladle and cover it with an inoculant. Initially, flush in 1 / 2-2 / 3 of the molten iron. When boiling is nearing completion, replenish the molten iron and skim off the slag.

[0004] 2. Cover ladle method, suitable for alloy nodulizers with magnesium content less than 15%. A cover-type tundish is installed on the injection ladle to receive the molten iron. The flow rate of the molten iron injected into the ladle is controlled by the diameter of the tundish bottom gate.

[0005] 3. Subcontracting method, suitable for pure magnesium or magnesium coke spheroidizer with 43% magnesium content. The reaction chamber is made of graphite clay and can process raw iron with 0.3% sulfur content at a processing temperature of 1400-1500℃.

[0006] 4. Wire-feed spheroidizing: The suitable spheroidizing agent contains 20%-45% magnesium, 0-6% rare earth, 1.0%-3.0% calcium, 40%-70% silicon, and the remainder iron. An automatic wire feeder is used to evenly feed the cored wire (containing the spheroidizing agent) into the molten iron. The cored wire is a thin iron tube 0.2-0.4mm thick filled with spheroidizing agent. 25-30m of cored wire is required to spheroidize 1 ton of molten iron, and the magnesium absorption rate is 40-50%.

[0007] The aforementioned spheroidization technology suffers from high inoculant consumption, with absorption rates of less than 50% during the process, generating smoke and requiring high-volume fans and dust collectors. The molten iron turnover time is long, and spheroidization degradation is common.

[0008] If ductile iron pipes could be spheroidized during the casting process, it would greatly simplify the molten iron treatment process, reduce spheroidizing agent consumption and emissions, shorten the pipe production process, improve production efficiency, and reduce production costs. However, such a process is currently lacking. Summary of the Invention

[0009] In view of the problems existing in the existing molten iron spheroidization inoculation technology, the present invention provides a molten iron spheroidization inoculation method during the centrifugal casting of ductile iron pipes with a short process, low spheroidizing agent consumption and high production efficiency, and also provides a device for implementing the method.

[0010] The method for spheroidizing molten iron during the centrifugal casting of ductile iron pipes of the present invention is:

[0011] During the centrifugal casting process of ductile iron pipe, a spheroidizing inoculant is fed into the throat of the pipe via a cored wire. As the molten iron enters the throat, the cored wire is continuously fed, allowing the spheroidizing inoculant to enter the throat along with the molten iron. The molten iron, carrying the spheroidizing inoculant, absorbs the spheroidizing inoculant as it flows through the throat, achieving spheroidization and inoculation. The spheroidized and inoculated molten iron then flows through a launder into a high-speed rotating pipe mold. Centrifugal force forms the cast pipe, while inclusions in the molten iron drift toward the inner wall before solidifying, resulting in a clean, dense pipe structure.

[0012] Before the molten iron enters the throat pipe (before pouring begins), the cored wire fed into the throat pipe is equal in length to the throat pipe to ensure the spheroidization inoculation effect of the initial molten iron.

[0013] The inner diameter and length of the throat pipe should ensure that the cored wire and the molten iron are spheroidized and inoculated in the throat pipe.

[0014] The device for realizing the above-mentioned molten iron spheroidization inoculation method adopts the following technical solutions:

[0015] The device includes a pouring cup, a throat, a launder, and a molten iron pouring device. The bottom of the pouring cup is connected to the throat, and the throat outlet is connected to the launder. A wire feeder and a molten iron pouring device are located above the pouring cup. The inner diameter of the throat is adapted to the molten iron pouring flow rate required for forming the cast pipe.

[0016] The molten iron pouring device includes a ladle and a pouring mechanism, the ladle being connected to the pouring mechanism. The ladle is fan-shaped. The ladle and pouring mechanism are mounted on a mobile vehicle. The mobile vehicle has drive wheels disposed on a track, and the mobile vehicle reciprocates along the track along a predetermined path. The mobile vehicle is provided with a sliding rail, and the ladle is placed on the sliding rail and is hinged to the mobile vehicle via a hinge.

[0017] The molten iron pouring mechanism utilizes a gear transmission mechanism comprising a motor, a gear, and a ring gear. The motor is mounted on a mobile vehicle, the gear is mounted on the motor's rotating shaft, and the ring gear is positioned outside the molten iron ladle, with the gear and the ring gear meshing with each other. The motor drives the molten iron ladle through the meshing transmission of the gear and the ring gear, causing it to rotate and tilt, thereby pouring the molten iron. The tilt angle of the molten iron ladle is controlled by controlling the motor's speed and rotation time, thereby achieving the desired pouring effect.

[0018] The wire feeding device and the pouring cup are installed on the mobile vehicle, and the cored wire is extended into the throat pipe through the wire feeding device (wire feeding machine).

[0019] The runner extends into the pipe mold, which is then rotated by a rotating device. The cored wire is fed into the throat pipe through a wire feeder. The molten iron in the ladle is poured into the pouring cup. Simultaneously, the wire feeder continuously conveys the cored wire and mixes it with the molten iron. The outer layer of the cored wire dissolves, and the spheroidizing inoculant is absorbed as it flows through the throat pipe with the molten iron, achieving flow-based spheroidization. The magnesium-sulfide compound particles (generated by the spheroidizing inoculant) produced during this process float to the inner wall of the cast pipe during high-speed centrifugal casting, without affecting the quality of the pipe.

[0020] The pouring speed of the pouring ladle is based on maintaining a certain liquid level in the pouring cup; the feeding speed of the core wire matches the rotation speed of the molten iron ladle, and is calculated based on the proportion of spheroidizing inoculant added to the molten iron.

[0021] The present invention uses a cored wire method to allow the spheroidizing inoculant to be absorbed in the throat pipe as the molten iron flows, thereby realizing flow-based spheroidizing inoculation, improving the absorption rate of the spheroidizing inoculant, shortening the spheroidizing process to the maximum extent, avoiding spheroidizing decay, reducing the amount of spheroidizing inoculant added, and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic structural diagram of an iron liquid spheroidizing inoculation device during the centrifugal casting of a ductile iron pipe.

[0023] The components include: 1. cored wire, 2. wire feeder, 3. pouring cup, 4. throat, 5. top mouth, 6. hinge shaft, 7. molten iron, 8. molten iron ladle, 9. gear, 10. moving carriage, 11. sliding rail, 12. moving platform, 13. launder, 14. rail, 15. pipe mold, and 16. rotating device. DETAILED DESCRIPTION

[0024] like Figure 1 As shown, the molten iron spheroidizing and inoculating device of the present invention comprises a pouring cup 3, a throat pipe 4, a launder 13 and a molten iron pouring device. The bottom of the pouring cup 3 is connected to the throat pipe 4, the outlet of the throat pipe 4 is connected to the launder 13, and a wire feeder 2 and a molten iron pouring device are arranged above the pouring cup 3. The launder 13 is in the shape of a trough with an open top. The inner diameter of the throat pipe 4 is adapted to the molten iron pouring flow rate required for the cast pipe forming. The inner diameter and length of the throat pipe are matched with the molten iron pouring efficiency, and should ensure that the cored wire and the molten iron are spheroidized and inoculated in the throat pipe. The wire feeder 2 is a prior art.

[0025] The molten iron pouring device includes a ladle 8 and a molten iron pouring mechanism. The ladle 8 is connected to the molten iron pouring mechanism, and both are arranged on a mobile car 10. The mobile car 10 is provided with a sliding rail 11. The ladle 8 is placed on the sliding rail 11 and is hinged to the mobile car 10 through a hinge shaft 6. The ladle 8 is connected to the molten iron pouring mechanism. The molten iron pouring mechanism drives the ladle 8 to rotate around the hinge shaft 6 to achieve the pouring of molten iron. The sliding rail 11 guides the movement of the ladle 8. The ladle 8 is fan-shaped and can achieve quantitative pouring. The mobile car 10 is placed on a moving platform 12 through the driving wheels at its bottom. The moving platform 12 is provided with a steel rail 14 (travel track). The mobile car 10 moves back and forth along the steel rail 14 on the moving platform 12.

[0026] The molten iron pouring mechanism utilizes a gear transmission mechanism, comprising a motor (not shown), gear 9, and a ring gear. The motor is mounted on a mobile vehicle 10, and gear 9 is mounted on the motor's rotating shaft. The ring gear is positioned outside the arc of the molten iron ladle 8, with gear 9 meshing with the ring gear. The motor, a servo motor, drives gear 9, which in turn rotates the ladle 8 through meshing transmission, causing it to tilt and pour out.

[0027] The wire feeder 2 and the pouring cup 3 can also be arranged on the mobile vehicle 10.

[0028] The operation process of the above-mentioned molten iron spheroidizing inoculation device is as follows.

[0029] The spheroidizing agent cored wire 1 is placed on the wire feeder 2 and inserted into the throat 4 of the pouring cup 3 through the wire feeder 2. Before the molten iron 7 enters the throat 4 (before pouring begins), the cored wire 1 fed into the throat 4 is equal in length to the throat 4 to ensure the spheroidizing effect of the initial molten iron.

[0030] The mobile vehicle 10 moves along the rail 14 on the moving platform 12 to the molten iron melting furnace and pours the molten iron 7 into the molten iron ladle 8. The mobile vehicle 10 moves toward the pipe mold 15, so that the flow channel 13 extends into the pipe mold 15, and the pipe mold 15 rotates under the drive of the rotating device 16.

[0031] The motor in the molten iron pouring mechanism is activated, driving the ladle 8 upward via a gear transmission, causing the molten iron 7 to pour from the upper opening 5 into the pouring cup 13. Simultaneously, the wire feeder 2 continuously feeds the cored wire 1 toward the throat pipe 4, where it mixes with the molten iron, dissolving the outer layer of the cored wire. The spheroidizing inoculant is absorbed as the molten iron passes through the throat pipe 4, thus achieving continuous spheroidization. The magnesium sulfide particles (generated by the spheroidizing inoculant) produced during this process float to the inner wall of the cast pipe during high-speed centrifugal casting and do not affect the quality of the pipe.

[0032] The tilting speed of the molten iron ladle 8 is based on maintaining a predetermined liquid level height of the pouring cup 3, and the feeding speed of the cored wire 1 delivered by the wire feeder 2 is calculated according to the molten iron flow rate and the addition ratio of the spheroidizing inoculant.

[0033] The particles can be precipitated before solidification by appropriately increasing the temperature of the molten iron and increasing the rotation speed of the tube mold 14 .

Claims

1. A method for spheroidizing molten iron during centrifugal casting of ductile iron pipes, characterized in that: During the centrifugal pouring process of ductile iron pipes, the spheroidizing inoculant is fed into the throat pipe through the cored wire. When the molten iron enters the throat pipe, the cored wire is continuously fed into the pipe, so that the spheroidizing inoculant enters the throat pipe along with the molten iron. The molten iron carries the spheroidizing inoculant and absorbs the spheroidizing inoculant in the process of flowing through the throat pipe to achieve spheroidization inoculation.

2. The method for spheroidizing molten iron during centrifugal casting of ductile iron pipes according to claim 1, wherein: Before the molten iron enters the throat pipe, the cored wire fed into the throat pipe is equal in length to the throat pipe.

3. The method for spheroidizing molten iron during centrifugal casting of ductile iron pipes according to claim 1, wherein: The inner diameter and length of the throat pipe enable the cored wire and the molten iron to be spheroidized and inoculated in the molten iron in the throat pipe.

4. A device for spheroidizing molten iron during the centrifugal casting of ductile iron pipes, characterized by: It includes a pouring cup, a throat, a flow channel and a molten iron pouring device. The bottom of the pouring cup is connected to the throat, the throat outlet is connected to the flow channel, and a wire feeding device and a molten iron pouring device are arranged above the pouring cup.

5. The device for spheroidizing molten iron during centrifugal casting of ductile iron pipes according to claim 4, characterized in that: The molten iron pouring device comprises a molten iron ladle and a molten iron pouring mechanism, and the molten iron ladle is connected to the molten iron pouring mechanism.

6. The device for spheroidizing molten iron during centrifugal casting of ductile iron pipes according to claim 4, characterized in that: The molten iron ladle is fan-shaped.

7. The device for spheroidizing molten iron during centrifugal casting of ductile iron pipes according to claim 4, characterized in that: The molten iron ladle and the molten iron dumping mechanism are arranged on a moving vehicle. A driving wheel is arranged at the bottom of the moving vehicle, and the driving wheel is placed on a walking track.

8. The spheroidizing inoculation device for centrifugal pouring of molten iron for ductile iron pipes according to claim 7, characterized in that: The moving vehicle is provided with a sliding rail, and the molten iron ladle is placed on the sliding rail and is hinged to the moving vehicle through a hinge shaft.

9. The device for spheroidizing molten iron during centrifugal casting of ductile iron pipes according to claim 4, characterized in that: The molten iron dumping mechanism adopts a gear transmission mechanism, including a motor, a gear and a gear ring. The motor is installed on the mobile vehicle, the gear is installed on the rotating shaft of the motor, and the gear ring is arranged outside the molten iron ladle. The gear and the gear ring are meshed.

10. The device for spheroidizing molten iron during centrifugal casting of ductile iron pipes according to claim 7, characterized in that: The wire feeding device and the pouring cup are installed on the mobile vehicle.

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