WO2015089959A1

WO2015089959A1 - Hollow cast iron pipe, and vertical continuous casting method and special equipment for same

Info

Publication number: WO2015089959A1
Application number: PCT/CN2014/074859
Authority: WO
Inventors: 许旸; 邓开金
Original assignee: 陕西同心连铸管业科技有限公司
Priority date: 2013-12-18
Filing date: 2014-04-04
Publication date: 2015-06-25
Also published as: CN103706773A

Abstract

Disclosed are a hollow cast iron pipe, and a vertical continuous casting method and special equipment for the same, comprising connecting an L-type continuous casting holding furnace, a rotating magnetic field generator and a crystallizer in series to form a U-shaped channel for allowing flowing of molten iron, and rotating the molten iron in the crystallizer by means of the rotating magnetic field generator. The manufactured hollow cast iron pipe has a standard structure, has no tension band on the wall surface of the inner hole, has a smooth wall surface and fine texture of the interior, has greatly improved dimensional precision, and can interfere with the radial growth of primary dendrite and increase the proportion of equiaxed crystal zone, thereby improving the mechanical properties of hollow cast iron pipe and having a high practical value.

Description

Hollow cast iron pipe and its vertical continuous casting method and special equipment

The invention belongs to the technical field of metal material thermal processing, and particularly relates to a hollow cast iron pipe and a vertical continuous casting method thereof and special equipment.

Background technique

Up to now, the relevant patented technology for drawing cast iron hollow cast pipe has been published, and its technical features are divided into two categories: The first type is horizontal continuous casting scheme: First, the device for producing cast iron pipe by horizontal continuous casting method and its production process, publication number : CN1410188; Second, hollow cast iron profile and horizontal continuous casting device, publication number: CN2589125; Third, a continuous cast production device for hollow cast iron profiles, publication number: CN102228963A. The common feature of the above technical solution is that on the basis of horizontal continuous casting, an inner core crystallizer is added in the middle of the original jacket type crystallizer, and the inner core crystallizer is composed of a water-cooled core and a graphite sleeve, and the two crystallizers are installed concentrically to form An annular gap, after the molten iron in the holding furnace continuously enters the annular space, continuously condenses into a ring-shaped shell, and is continuously drawn out. A potential hidden danger of such a scheme is that when the molten iron condenses out of the shell on the inner core crystallizer, a large contraction force is generated, and the graphite sleeve is tightly hung, and when the shell is drawn, the graphite sleeve will be It has been pulled off. Therefore, such programs are not reasonable and possibility in theory, especially in practice. The second category is the vertical continuous casting scheme. The patents that have been published are mainly KR9001324 (Continous Casting Line of a Cast Iron Tube, Priority number: FR1 9840018084 19841126.) and US4236571 (Process and Installation for the Continuous Casting of Tubular.) As a representative, one of the basic features of this type of technical solution is vertical drawing, and the second is the use of a hot core crystallizer. In order to prevent the graphite of the cold core crystallizer from being broken, this type of technical solution uses a hot core crystallizer, that is, heating the graphite core with a built-in induction coil, or letting molten iron enter the inside of the graphite core, when the molten iron enters the jacket crystallizer and the hot core. After the annular space, the tube is condensed only by the coat crystallizer, and the hot core graphite sleeve is not hooped. Such technical solutions have major defects, because: 1. The hot core of the patent KR9001324 is surrounded by molten iron. The working temperature is also the temperature of molten iron. For ordinary cast iron, this temperature must be around 1300 °C; Patent US4236571 uses the induction coil to heat the graphite core, the temperature must be higher, we know that graphite in molten iron above 1250 °C , will be quickly etched, can not last more than 10 minutes; 2, if the use of materials resistant to hot metal etching (such as β-sialon, α-sialon), and will be rubbed against the inner wall of the condensed pipe, resulting in Pull off. In practice, the temperature of molten iron must fluctuate. It is impossible to ensure that the solidification process of the pipe can just end in the end of the annular space. If it ends earlier, the condensed pipe will hug the hot core. If it ends later, the molten iron will leak out; The inner core is placed in the outer casing mold, and the induction coil is placed in the inner core, which inevitably limits the inner diameter of the drawn pipe. In fact, the inner diameter of the pipe that can be drawn by this scheme cannot be less than 150 mm.

The applicant's previously filed patents (CN 100479948C and CN 201371225Y) disclose a new technical solution for vertical coreless continuous casting. The jacket type crystallizer is vertically installed, and the time difference from the outside to the inside in the crystallizer by the condensation process, and the stepwise thickening from the bottom to the top, the tube is pulled up step by step when condensing a certain thickness of the pipe. . The other end of the holding furnace is continuously poured with molten iron to keep the molten iron in the crystallizer always filled, and the liquid level is maintained near the height of the upper flange, so that the condensation process from the outside to the inside Conducted without interruption. Such a scheme has the following drawbacks: First, the temperature of the molten iron in the crystallizer gradually decreases from bottom to top, the temperature on the top surface of the uppermost portion is the lowest, the fluidity of the molten iron is deteriorated, and the inner wall of the formed core is rough; Since the continuous casting process is "pull-pause-pull-pause-..." alternately, and the pause time is several times or even ten times longer than the drawing time, the molten iron level is relatively stationary in the die at the time of the pause, and the diameter The solidification speed is very large, so at this height position, the wall thickness of the pipe is obviously thickened, and macroscopically, there is a bamboo-shaped annular boss (or "hoist") on the inner wall of the pipe. The superposition of the above two defects makes the dimensional accuracy of the inner hole of the continuous casting hollow cast pipe greatly reduced. It has been verified that the height of the hoop is 3_8mm on the continuous casting pipe with outer diameter of 100-200mm and wall thickness of 10-20mm, so that the inner diameter is The error is as high as 6-16. On the continuous casting pipe with the outer diameter of 200mm or more and the wall thickness of 20 or more, the height of the hoop is 5-10mm, so that the inner diameter size error is 10_20mm. Such a serious dimensional error makes the continuous casting hollow cast pipe The market application value has dropped significantly. The third is due to the high cooling rate of the water-cooled crystallizer (the average cooling rate is 4-5 times that of centrifugal casting and about 30 times that of sand casting), which causes the molten iron in the mold. The radial temperature gradient is so large that the primary dendrite is very developed and can penetrate almost the entire wall. Concomitantly, the grain boundaries and graphite sheets in the cast structure are mostly parallel to the radial direction. The tangential strength of the cast tube is greatly reduced. Fourth, there is no strong convection in the molten iron column in the crystallizer, and the solute distribution gradient is large, resulting in a large difference in the inner and outer layers of the tube wall, and the uniformity of the structure and properties is deteriorated. The existence of the above four defects indicates that although the cast iron hollow cast pipe can be drawn by the vertical continuous casting method, the dimensional error of the inner hole is too large from the shape of the pipe, which is far from the technical level of "near net forming". From the microscopic point of view, the primary primary dendrite is too developed, the proportion of equiaxed crystal structure is too small, and the tangential strength of the material is relatively Low; In terms of composition and performance, the inner and outer layers of the pipe wall are inconsistent. The above defects have become the bottleneck in the development of the vertical continuous casting method, so it is necessary to improve. Summary of the invention

Technical problem solved by the invention: Providing a hollow cast iron pipe and a continuous casting method thereof and special equipment

The L-shaped continuous casting holding furnace, the rotating magnetic field generator and the crystallizer are connected in series to form a U-shaped channel for the flow of molten iron, and the molten iron is continuously injected from one end of the U-shaped channel, and the refractory flowing through the inside of the rotating magnetic field generator The tube, which enters the graphite sleeve of the crystallizer, begins to solidify from the outside to the inside, and finally the steel pipe drawn by the mechanical traction roller vertically pulls out the hollow cast iron profile.

The technical scheme adopted by the invention: The vertical continuous casting method of the hollow cast iron pipe adopts the L-type continuous casting holding furnace together with the rotating magnetic field generator and the crystallizer to form a U-shaped channel for the flow of molten iron, and the molten iron in the molten iron pouring bag is from the L-shaped The left-end inlet of the U-shaped channel of the continuous casting holding furnace is continuously injected, flows through the rotating magnetic field generator and enters the crystallizer, and the rotating magnetic field generated by the rotating magnetic field generator drives the high-speed rotation of the molten iron surrounded by the magnetic field to drive the molten iron in the crystallizer to rotate. The high-speed rotating molten iron condenses from the outside to the inside in the crystallizer, and then the steel pipe drawn by the mechanical traction roller vertically pulls out the hollow cast iron pipe.

Specifically, the following steps are included:

1) Sparkling preheats the U-shaped channel to make the bottom surface temperature greater than 80CTC;

2) Hold the upper end of the steel pipe with the outer diameter slightly smaller than the inner diameter of the graphite sleeve with a mechanical pulling roller located directly above the crystallizer, and insert the lower end of the steel pipe into the graphite sleeve to reach the middle position of the crystallizer; a spiral groove is formed on the inner wall surface of the lower end of the steel pipe, so that the molten iron is immersed in cold solidification and integrated into the steel pipe;

3) Melt and dispose of the appropriate molten iron, 150CTC is put out, poured into the hanging bag, inoculated, and then poured into the molten iron pouring bag, the hydraulic cylinder works to tilt the molten iron pouring bag, and the molten iron is gradually injected into the U-shaped channel;

4) When the molten iron level in the U-shaped channel is slightly higher than the middle position of the crystallizer and immersed in the spiral groove at the lower end of the steel pipe, the pouring is stopped, and the pre-cooling pause time is determined according to the diameter of the hollow cast pipe to be drawn, and the molten iron is in the crystallizer at this time. The solidification starts from the outside to the inside, and the mechanical traction roller starts to be pulled after the pre-cooling pause time is over, and after the drawing starts, the molten iron pouring bag controlled by the hydraulic cylinder continuously casts molten iron into the U-shaped channel to make the liquid in the mold. The surface is always at a height above the middle;

5) After pulling out the hollow cast pipe of 1-2 meters, start the rotating magnetic field generator to rotate the molten iron in the crystallizer;

6) When the steel pipe for seeding rises and the lower end exceeds the mechanical traction roller 1-2 meters, the cutting mechanism above the mechanical traction roller cuts the hollow casting pipe and is unloaded and placed on the ground;

7) According to the wall thickness condition of the cut pipe, adjust the drawing parameters and the magnetic field strength to achieve the wall thickness and inner hole precision of the required hollow cast pipe;

8) At the end of drawing, after all the molten iron in the molten iron pouring bag is poured out, open the plug of the iron leakage hole, drain all the molten iron, and turn off the rotating magnetic field generator and the traction machine power supply.

9) When the temperature of the L-type continuous casting holding furnace is lowered to near room temperature, turn off the inlet pipe of the crystallizer and the rotating magnetic field generator.

Also provided is a hollow cast iron pipe, comprising a pipe body having a fine inner structure, The inner wall of the tube is a smooth surface without a bamboo-like ferrule, and the flatness error of the smooth surface is less than

2mm.

A special device for vertical continuous casting of hollow cast iron pipe is provided, which has a crystallizer, a rotating magnetic field generator and an L-type continuous casting holding furnace, and the left end of the L-shaped continuous casting holding furnace is placed at the lower end of the molten iron pouring bag, the rotating magnetic field The generator is fixed on the upper end surface of the right end of the L-type continuous casting holding furnace, and the crystallizer is fixed on the upper end surface of the rotating magnetic field generator, and forms a U-shaped channel for the flow of molten iron together with the left end of the L-type continuous casting holding furnace.

Wherein, the crystallizer comprises a graphite sleeve and a steel water cooling sleeve, wherein the graphite sleeve is pressed into the steel water cooling jacket, and the upper end surface of the graphite sleeve and the steel water cooling sleeve is provided with a mold upper flange, and the steel water cooling sleeve a lower end surface of the mold is provided with a lower flange of the mold and a lower end of the graphite sleeve extends out of the lower flange of the mold; the rotating magnetic field generator comprises a water cooling sleeve, a refractory tube and an excitation coil, and the water cooling sleeve is inserted into the inner hole of the excitation coil, The refractory tube is inserted into the inner hole of the water cooling sleeve and the refractory cotton is interposed between the two, the upper end surface of the water cooling sleeve and the excitation coil is provided with a magnetic field generator upper flange, and the water cooling sleeve and the lower end surface of the excitation coil are provided with a magnetic field generator The lower end of the refractory tube protrudes from the lower flange of the magnetic field generator; the L-shaped continuous casting holding furnace comprises an L-shaped seat body, the L-shaped seat body is provided with a passage, and the lower end of the graphite sleeve passes through the magnetic field generator The flange is connected with the upper port of the refractory pipe, and the lower end of the refractory pipe communicates with the end port of the passage to form a U-shaped passage for the molten iron to flow, and the connecting bolt passes through the lower flange of the crystallizer, the upper flange of the magnetic field generator and the magnetic field generator Lan, The crystallizer and the rotating magnetic field generator are integrally connected, and the lower flange of the magnetic field generator is fixedly connected with the right end of the L-shaped seat body through a stainless steel connecting plate, and the right side of the L-shaped seat body is provided with a drain hole and used The stopper is tight.

Further, the water cooling jacket is made of a polytetrafluoroethylene material; Made of jadeite stone material.

Further, the water-cooling jacket is a spiral water-cooling jacket, comprising a body with a spiral groove and a cylindrical outer wall, and the two are transiently integrated, and the cylindrical outer wall is sleeved from one end of the body with the spiral groove to form a closed spiral water channel. The upper and lower portions of the cylindrical outer wall are formed with screw holes.

Further, a through hole is formed in the circumferential wall of the upper and lower ends of the exciting coil, and the inlet pipe and the outlet pipe of the water jacket are inserted from the through hole and screwed into the screw hole on the outer circumference of the cylindrical outer wall.

Compared with the prior art, the L-type continuous casting holding furnace, the rotating magnetic field generator and the crystallizer are connected in series to form a U-shaped channel for the flow of molten iron, and the rotating magnetic field generator is used to rotate the molten iron in the crystallizer. The hollow cast iron pipe produced has a regular shape and no ferrule on the inner wall surface. The wall surface is smooth and the internal structure is fine, the dimensional accuracy is greatly improved, and the radial growth of the primary dendrite is disturbed, and the proportion of the equiaxed crystal zone is increased. The mechanical properties of the hollow cast tube have very high practical value. DRAWINGS

Figure 1 is a schematic structural view of the present invention;

2 is a schematic structural view of a rotating magnetic field generator of the present invention. detailed description

An embodiment of the present invention will now be described with reference to Figs.

Vertical continuous casting method for hollow cast iron pipe, using L-type continuous casting holding furnace 3 and rotating magnetic The field generator 2 and the crystallizer 1 together form a U-shaped channel 5 through which the molten iron 6 flows, and the molten iron 6 in the molten iron pouring bag 4 is continuously injected from the left end entrance of the U-shaped channel 5 of the L-type continuous casting holding furnace 3, and flows through the rotation. The magnetic field generator 2 re-enters the crystallizer 1, and the rotating magnetic field generated by the rotating magnetic field generator 2 drives the molten iron 6 surrounded by the magnetic field to rotate at a high speed, and the molten iron 6 in the crystallizer 1 is rotated, and the high-speed rotating molten iron 6 is in the crystallizer 1 The steel pipe 8 which is condensed from the outside to the inside and then pulled by the mechanical pulling roller 7 pulls the hollow cast iron pipe vertically upward.

Specific steps are as follows:

Preparation: Press the graphite sleeve 9 into the steel water jacket 10 to form the crystallizer 1; the graphite sleeve 9 is about 30 mm longer than the steel water jacket 10, and protrudes from the hole of the lower flange 12 of the mold, which will be prefabricated. A good refractory tube 14 is inserted into the polytetrafluoroethylene water-cooling jacket 13 and is tightly packed with refractory cotton 22; the upper end surface of the refractory tube 14 is lower than the magnetic field generator shared by the exciting coil 15 and the Teflon water-cooling jacket 13 The upper flange 16 is about 30 mm, which is equivalent to the length of the protruding end of the graphite sleeve 9. The lower end surface of the refractory tube 14 is about 50-60 mm longer than the end surface of the lower flange 17 of the magnetic field generator, and also forms an extended end. Applying high temperature resistant zircon powder between the protruding end of the graphite sleeve 9 and the mating end surface of the refractory tube 14, inverting the crystallizer 1, and placing the rotating magnetic field generator 2 on the protruding end of the graphite sleeve 9, and then generating a magnetic field The lower flange 17 is sleeved on the refractory tube 14. Finally, the lower mold flange 12 is connected to the magnetic field generator upper flange 16 and the magnetic field generator lower flange 17 by four stainless steel connecting bolts 20 to form a whole. . At the same time, on the right end plane of the L-type continuous casting holding furnace 3 (on the lower end plane), the circular hole on the stainless steel connecting plate 21 which is connected to the L-shaped seat body 18 in advance is taken as the outer diameter, and the stepped hole is repaired downward. The center is the outlet of the passage 19 on the L-shaped continuous casting holding furnace 3, the stepped hole depth is 50-60 mm; the refractory soil is smashed into strips, and the disk is at the bottom end surface of the stepped hole; Lifting the crystallizer 1 and the rotating magnetic field generator 3, inserting the protruding end of the refractory tube 14 into the stepped hole, and fastening the magnetic field generator lower flange 17 to the stainless steel connecting plate 21; removing the U-shaped channel 5 due to the pressing operation The excess refractory mud is extruded; the debris falling into the U-shaped channel 5 is cleaned from the iron leakage hole 23, and is sealed with the plug 24; the crystallizer 1 and the rotating magnetic field generator inlet and outlet pipes are installed and connected. The rotating magnetic field generator 3 and the wires of the current regulating cabinet can be officially put into use after the above preparation work is completed:

1) Sparkling preheats the U-shaped channel 5, so that the bottom surface temperature is greater than 80CTC;

2) holding the upper end of the steel pipe 8 having an outer diameter slightly smaller than the inner diameter of the graphite sleeve 9 by the mechanical pulling roller 7 located directly above the crystallizer 1, and inserting the lower end of the steel pipe 8 into the graphite sleeve 9 to reach the middle position of the crystallizer 1; a spiral groove is formed on the inner wall surface of the lower end, so that the molten iron 6 is cold-solidified after being immersed, and is integrated with the steel pipe 8;

3) Melt and dispose of the appropriate molten iron, about 150CTC is put out, poured into the hanging bag, inoculated, and then poured into the molten iron pouring bag 4, the hydraulic cylinder 25 works to tilt the molten iron pouring bag 4, and the molten iron 6 is gradually injected into the U Specifically, when the molten iron 6 in the molten iron pouring bag 4 is nearing completion, the next set of molten iron is poured into the hanging bag by the hanging bag, and the hydraulic cylinder 25 is lowered when pouring, but still needs to be U. The molten iron 6 is cast at the inlet end of the type channel 5 to ensure that the molten iron level in the U-shaped channel 5 is constant, and the interval between the hanging bag and the molten iron 6 in the molten iron pouring bag 4 is less than the effective working time of the inoculant and the spheroidizing agent used. 1/2;

4) When the molten iron level in the U-shaped channel 5 is slightly higher than the middle position of the crystallizer 1 and immersed in the spiral groove at the lower end of the steel pipe 8, the pouring is stopped, and the dwell time is determined according to the diameter of the hollow cast pipe to be drawn, and the pause time is based on experience. Can be determined as follows: According to the diameter of the pipe to be drawn

( Φ ) size determines the time to pause to, ( Φ ^ 100mm, to ^ lO seconds; Φ ^ 200mm When, t. 15 seconds; C ^300mm, t. 20 seconds, and so on), at this time, the molten iron 6 solidifies from the outside to the inside in the crystallizer 1, and after the end of the pre-cooling pause time, the mechanical pulling roller 7 is started to be pulled, the initial step of the drawing step is 40 mm, and the drawing is performed. After the start, the molten iron pouring bag 4 controlled by the hydraulic cylinder 25 continuously casts molten iron into the U-shaped passage 5, so that the liquid level in the crystallizer 1 is always maintained at a height above the middle portion thereof, and the hanging bag is intermittently poured into the molten iron bag 4 Supplementing molten iron 6, the intermittent time is less than half of the effective time of the molten iron;

5) After pulling out the hollow cast pipe of 1-2 m, start the rotating magnetic field generator 2 to rotate the molten iron 6 in the crystallizer 1. The initially drawn 1-2 m hollow cast pipe contains defects such as impurities, cold partitions and pores, which cannot be used. The subsequent hollow cast pipe has no defects and becomes a highly dense hollow cast pipe;

6) When the steel pipe 8 for seeding rises and the lower end thereof exceeds the mechanical pulling roller 7 and the cutting mechanism above it, the hollow cast pipe is cut; when the lower end of the steel pipe 8 rises to the height position of the mechanical pulling roller 7, the newly formed hollow The cast pipe itself replaces the steel pipe 8, and becomes a drawing guide rod. The breaking mechanism above the mechanical pulling roller 7 cuts the hollow casting pipe according to the required length and unloads it to the ground position;

7) During the drawing process, according to the wall thickness of the hollow cast tube and the smoothness of the inner wall surface observed after the break, adjust the drawing parameters and the strength of the rotating magnetic field at any time to obtain the required wall thickness and as good as possible. Lightness. The thickness of the pipe wall is adjusted by the drawing parameter, and the drawing parameters include: "occupation ratio" (ie, the ratio of the drawing time to the pause time), the adjustment range is 1. 2~0. 1; the pulling step, the adjustment range 30 ~50mm; hot metal tapping temperature, adjustment range 1520~ 1450 °C (ball iron), 1460~1400 °C (grey iron); crystallizer water intake, reference to the outlet water temperature, adjustment range 40 °C ~ 70 °C If you want to thicken the pipe wall, you can take it separately The above four measures can also be combined to reduce the occupancy ratio, reduce the pulling step, reduce the temperature of molten iron, and increase the water inflow of the mold. If the wall is to be thinned, the opposite measures are taken. The smoothness is adjusted by the intensity of the rotating magnetic field and varies from 250 Gs to 500 Gs. Depending on the inner diameter of the cast tube, the rotating magnetic field produces a V-shaped liquid level of different heights and a different degree of flushing of the liquid/solid interface. Under the premise of eliminating the flatness of the bamboo-shaped hoop and the inner wall surface by 2mm, the magnetic field strength should be reduced as much as possible to reduce the influence of the flushing on the propelling speed of the liquid-solid interface.

8) At the end of drawing, after all the molten iron 6 in the molten iron pouring bag 4 is poured out, open the plug 24 of the iron leakage hole 23, vent all the molten iron, and turn off the rotating magnetic field generator 2 and the power of the tractor.

9) When the temperature of the L-type continuous casting holding furnace is lowered to room temperature, turn off the inlet pipe of the crystallizer 1 and the rotating magnetic field generator 2, and end the drawing.

Of course, in the specific drawing process, since the graphite sleeve 9 and the refractory tube 14 are wearing parts, after a cycle is used, it is necessary to replace the new one. The special equipment needs to consider the easy removal and convenience of the graphite sleeve 9 and the refractory tube 14. Installability.

The hollow cast iron pipe prepared by the above method has a fine inner structure of the pipe body, and the inner wall of the pipe body is a smooth surface without a bamboo-shaped hoop, and the flatness error of the smooth surface is less than 2 mm.

A special equipment for vertical continuous casting of hollow cast iron pipe is also provided, which has a crystallizer 1, a rotating magnetic field generator 2 and an L-type continuous casting holding furnace 3, and the left end of the L-shaped continuous casting holding furnace 3 is placed at the lower end of the molten iron pouring bag 4. The rotating magnetic field generator 2 is fixed on the right end surface of the L-type continuous casting holding furnace 3, and the crystallizer 1 is fixed on the upper end surface of the rotating magnetic field generator 2, and forms a molten iron together with the left end of the L-type continuous casting holding furnace 3. 6 circulating U-shaped channel 5. The crystallizer 1 comprises a graphite sleeve 9 and a steel water jacket 10, and the graphite sleeve 9 is pressed into the steel water jacket 10, and the upper end surface of the graphite sleeve 9 and the steel water jacket 10 is provided with a mold upper flange 11 a lower end of the steel water jacket 10 is provided with a lower mold flange 12 and a lower end of the graphite sleeve 9 extends out of the lower mold flange 12; the rotating magnetic field generator 2 includes a water cooling jacket 13, a refractory tube 14 and an exciting coil 15, The water cooling jacket 13 is preferably made of polytetrafluoroethylene material and the water cooling jacket 13 is a spiral water cooling jacket, and the refractory tube 14 is preferably made of corundum mullite material; the water cooling jacket 13 is inserted into the inner hole of the exciting coil 15, the refractory tube 14 is inserted into the inner hole of the water cooling jacket 13 and between the two is provided with a refractory cotton 22, the upper end surface of the water cooling jacket 13 and the excitation coil 15 is provided with a magnetic field generator upper flange 16, and the water cooling jacket 13 and the excitation coil 15 are provided at the lower end surface. There is a magnetic field generator lower flange 17 and the lower end of the refractory tube 14 protrudes from the magnetic field generator lower flange 17; the water cooling jacket 13 is a spiral water cooling jacket, including a spiral grooved body 28 and a cylindrical outer wall 29 and the transitional fit therebetween In one piece, the cylindrical outer wall 29 is nested from one end of the body 28 with the spiral groove a closed spiral channel, the upper and lower portions of the cylindrical outer wall 29 are provided with screw holes, and the outer circumference of the excitation coil 15 is formed with a through hole, and the inlet pipe 26 of the water cooling jacket 13 and the outlet The water pipe 27 is inserted into the through hole and screwed into the screw hole of the outer circumference of the cylindrical outer wall 29. The refractory tube 14 is used as the circulating molten iron 6, and the water-cooling sleeve 13 protects the exciting coil 15 from high temperature damage. The exciting coil 15 is required to ensure that the magnetic field strength acting on the core of the molten iron is greater than 500 Gs, so as to be able to drive the molten iron to rotate and pull different hollow cast pipes. The required magnetic field strength can be controlled by adjusting the current. The rotating magnetic field causes the molten iron 6 in the crystallizer 1 to rotate at a high speed, and when the rotational speed reaches the value required for the centrifugal force formula of the vertical centrifugal casting, a V-shaped liquid surface is formed in the crystallizer 1.

After the rotating magnetic field generator 2 is started, the rotating magnetic field drives the rotating magnetic field generator 2 The molten iron 6 rotates, which in turn drives the molten iron 6 in the crystallizer 1 to rotate. This rotational motion produces the following effects:

1. The convection and heat transfer processes required to solidify the molten iron 6 are mutated, reducing the temperature gradient in the radial direction and the axial direction of the molten iron column, strengthening the characteristics of layered solidification, facilitating equiaxed crystal nucleation, survival and Growing

2. The rotating scouring of molten iron 6 interrupts the rapid growth of dendrites once, and enlarges the proportion of equiaxed crystal structure; interferes with the mass transfer process, homogenizes the distribution of components in molten iron, avoids segregation of components, and reduces the inner and outer layers of gold in the wall Difference in organization;

3. For the drawing of each step, when the drawing is just finished, the molten iron 6 in the graphite sleeve 9 has the lowest height, but the amount of the molten iron 6 is also the least. At a fixed rotational speed, the V-shaped liquid surface The height difference is the largest. As the molten iron 6 is continuously injected during the pause, the molten iron 6 increases and the V-shaped liquid level difference gradually decreases. This fluctuation in the level difference of the liquid surface eliminates the bamboo-like annular boss (hoop) formed by the solidification of the surface layer on the inner wall of the pipe during the drawing pause; and the continuous scouring of the liquid-solid interface by the rotation of the molten iron column , the inner wall of the pipe is smooth, the circumferential direction is uniform, and the inner diameter dimensional accuracy is greatly improved.

The L-type continuous casting holding furnace 3 comprises an L-shaped base body 18, and the L-shaped seat body 18 is formed with a passage 19, and the lower end of the graphite sleeve 9 is connected to the upper port of the refractory tube 14 through the upper flange 16 of the magnetic field generator. The lower end of the refractory tube 14 communicates with the end of the passage 19 to form a U-shaped passage 5 through which the molten iron 6 flows. The connecting bolt 20 passes through the lower mold flange 12, the magnetic field generator upper flange 16 and the lower flange 17, and will The crystallizer 1 and the rotating magnetic field generator 2 are integrally connected, and the magnetic field generator lower flange 17 is fixedly coupled to the right end of the L-shaped base body 18 through a stainless steel connecting plate 21, and the right end side of the L-shaped base body 18 is formed. There are iron holes 23 and plugs 24 plug tight.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and all equivalent changes made by the claims of the present invention should be included in the scope of the claims of the present invention. .

Claims

1. Vertical continuous casting method for hollow cast iron pipe, characterized in that: L-type continuous casting holding furnace (3) and rotating magnetic field generator (2) and crystallizer (1) together form a U-shaped flow for supplying molten iron (6) Channel (5), molten iron (6) in the hot metal pouring package (4) is continuously injected from the left end entrance of the U-shaped channel (5) of the L-type continuous casting holding furnace (3), flowing through the rotating magnetic field generator (2) Entering the crystallizer (1), the rotating magnetic field generated by the rotating magnetic field generator (2) drives the molten iron (6) surrounded by the magnetic field to rotate at a high speed, driving the molten iron in the crystallizer (1)

(6) Rotating, high-speed rotating molten iron (6) Condensing from the outside to the inside in the crystallizer (1), and then drawing the hollow cast iron pipe vertically upward through the steel pipe (8) pulled by the mechanical pulling roller (7).

2. A method of preparing a continuous casting of a hollow cast iron pipe according to claim 1, comprising the steps of:

1) Spitfire preheating U-shaped channel (5), so that the bottom surface temperature is greater than 80CTC;

2) Hold the upper end of the steel tube (8) with the outer diameter slightly smaller than the inner diameter of the graphite sleeve (9) with the mechanical pulling roller (7) located directly above the crystallizer (1), and insert the lower end of the steel tube (8) into the graphite sleeve (9). Arriving at the middle position of the crystallizer (1); a spiral groove is formed on the inner wall surface of the lower end of the steel pipe (8), so that the molten iron (6) is immersed in cold solidification and integrated with the steel pipe (8);

3) Melt and dispose of the appropriate molten iron, about 150CTC, put it into the hanging bag, inoculate it, and then pour it into the molten iron pouring bag (4). The hydraulic cylinder (25) works to tilt the molten iron pouring bag (4). Gradually inject molten iron (6) into the U-shaped channel (5);

4) When the height of the molten iron in the U-shaped channel (5) is slightly higher than the middle position of the crystallizer (1) and immersed in the spiral groove at the lower end of the steel pipe (8), the casting is stopped, according to the hollow casting to be drawn. The tube diameter determines the pre-cooling pause time, at which time the molten iron (6) starts to solidify from the outside to the inside in the crystallizer (1), and after the pre-cooling pause time ends, the mechanical pulling roller (7) is started to be pulled, and after the drawing starts, , the molten iron pouring bag (4) controlled by the hydraulic cylinder (25) continuously casts molten iron into the U-shaped channel (5), so that the liquid level in the crystallizer (1) is always maintained at f3⁄4 degrees above the middle portion;

5) After pulling out the hollow cast pipe of 1-2 m, start the rotating magnetic field generator (2) to rotate the molten iron in the crystallizer (1);

6) When the steel tube (8) for seeding rises and the lower end exceeds the mechanical traction roller (7) 1-2 m, the breaking mechanism above the mechanical traction roller (7) works, the hollow casting tube is cut off, and the cylinder is unloaded. On the ground;

7) According to the wall thickness of the cut pipe, adjust the drawing parameters and the magnetic field strength to achieve the wall thickness and inner hole precision of the required hollow cast pipe;

8) At the end of drawing, after all the molten iron (6) in the molten iron pouring bag (4) is poured out, open the plug (24) of the iron leakage hole (23), drain all the molten iron, and turn off the rotating magnetic field generator ( 2) And the tractor power supply.

9) When the temperature of the L-type continuous casting holding furnace (3) is lowered to near room temperature, turn off the inlet pipe of the crystallizer (1) and the rotating magnetic field generator (2).

3. The hollow cast iron pipe prepared by the vertical continuous casting method according to claim 1, comprising: a pipe body having a fine inner structure, wherein the inner wall of the pipe is a smooth surface without a bamboo-shaped hoop, The flatness error of the entire surface is less than 2 mm.

4. The special equipment for vertical continuous casting of hollow cast iron pipe according to claim 1, characterized by: having a crystallizer (1), a rotating magnetic field generator (2) and an L-type continuous casting insulation Furnace (3), the left end of the L-type continuous casting holding furnace (3) is placed at the lower end of the molten iron pouring package (4), and the rotating magnetic field generator (2) is fixed on the right end surface of the L-shaped continuous casting holding furnace (3) The crystallizer (1) is fixed on the upper end surface of the rotating magnetic field generator (2), and together with the left end of the L-type continuous casting holding furnace (3) constitutes a U-shaped channel (5) through which the molten iron (6) flows.

5. The special equipment for vertical continuous casting of hollow cast iron pipe according to claim 4, characterized in that: the crystallizer (1) comprises a graphite sleeve (9) and a steel water cooling jacket (10), the graphite sleeve ( 9) Pressed into the steel water cooling jacket (10), the upper end surface of the graphite sleeve (9) and the steel water cooling jacket (10) is provided with a mold upper flange (11), and the steel water cooling jacket (10) lower end surface The lower flange of the mold (12) is provided and the lower end of the graphite sleeve (9) extends out of the lower flange of the mold

(12); the rotating magnetic field generator (2) comprises a water cooling jacket (13), a refractory tube (14) and an exciting coil (15), and the water cooling jacket (13) is inserted into the inner hole of the exciting coil (15). The refractory tube (14) is inserted into the inner hole of the water-cooling sleeve (13) with refractory cotton (22) interposed therebetween, and the upper end surface of the water-cooling sleeve (13) and the excitation coil (15) is provided with a magnetic field generator Lan (16), the water cooling jacket (13) and the excitation coil (15) have a lower magnetic field generator flange (17) on the lower end surface and a lower end of the refractory tube (14) protruding from the magnetic generator lower flange (17); The L-type continuous casting holding furnace (3) comprises an L-shaped seat body (18), the L-shaped seat body (18) is provided with a passage (19), and the lower end of the graphite sleeve (9) passes through the magnetic field generator Lan (16) is connected to the upper port of the refractory pipe (14), and the lower end of the refractory pipe (14) communicates with the end port of the passage (19) to form a U-shaped passage (5) for circulating molten iron (6), and the connecting bolt (20) Pass through the lower flange of the mold

(12) a magnetic field generator upper flange (16) and a magnetic field generator lower flange (17), the crystallizer (1) and the rotating magnetic field generator (2) are integrally connected, and the magnetic field generator lower flange

(17) fixedly connected to the right end of the L-shaped seat body (18) through the stainless steel connecting plate (21) The L-shaped seat body (18) has a drain hole (23) on the right end side and is plugged with a plug (24).

The special equipment for vertical continuous casting of hollow cast iron pipe according to claim 5, characterized in that: the water-cooling jacket (13) is made of polytetrafluoroethylene material; and the refractory pipe (14) is made of corundum Made of stone material.

7. The special equipment for vertical continuous casting of hollow cast iron pipe according to claim 6, wherein: the water cooling jacket (13) is a spiral water cooling jacket, and comprises a body with a spiral groove.

(28) and the cylindrical outer wall (29) and the transitional integration of the two, the cylindrical outer wall (29) is nested from the end of the body (28) with the spiral groove to form a closed spiral water channel, the cylindrical shape The upper and lower portions of the outer wall (29) are provided with screw holes.

The special equipment for vertical continuous casting of hollow cast iron pipe according to claim 7, characterized in that: the outer circumference of the excitation coil (15) is provided with a through hole, and the water-cooling sleeve (13) The inlet pipe (26) and the outlet pipe (27) are inserted from the through holes and screwed into the screw holes on the outer circumference of the cylindrical outer wall (29).