Method for preventing edge portion of steel coil from overflowing and bending during batch annealing

Abstract

A method for preventing an edge portion of a steel coil from overflowing and bending during batch annealing. When steel coils are stacked and piled, a dual-ring convection body consisting of an inner convection ring (3) and an outer convection ring (4) is provided between upper and lower steel coils; each of the inner convection ring (3) and the outer convection ring (4) consists of a ring body and a plurality of fan-shaped blocks uniformly provided on the ring body in a circumferential direction; the upper surfaces and lower surfaces of the fan-shaped blocks all protrude from the ring body and are flat surfaces; the inner convection ring (3) and the outer convection ring (4) are coaxially arranged; and the sizes of the inner convection ring (3) and the outer convection ring (4) are determined according to specific portions and widths of overflow edges on the steel coils, such that both the inner convection ring (3) and the outer convection ring (4) come into contact with flat end faces of the steel coils in areas without the overflow edges. The inner convection ring (3) and the outer convection ring (4) are used in cooperation to replace existing convection disks of an integrated structure, so that steel coils can be piled and stacked in a bell furnace in such a way that overflow edges are completely avoided, thereby eliminating the phenomenon of the overflow edges bending.

Description

A method for preventing overflow and bending of the edge of hood-annealed steel coil Technical Field

[0001] The present invention relates to the technical field of hood annealing, and in particular to a method for preventing overflow and bending of a hood annealed steel curling portion. Background Art

[0002] Bell annealing is a heat treatment method that eliminates work hardening of cold-rolled steel strip and improves mechanical properties. After cold rolling, the strip enters a bell-type furnace for annealing. As shown in Figure 1, coils 1 are stacked vertically in the bell-type furnace. A convection plate 2 is placed between the upper and lower coils 1 to maintain unimpeded flow of the annealing medium (hydrogen) within the furnace hood between the stacked coils 1, ensuring uniform temperature throughout the annealing process. Because the leading and trailing ends of the hot-rolled strip are rolled under tension, camber is easily generated. After cold rolling, multiple layers of 10-35 mm high (along the coil axis or strip width) overflow edges are formed on the coil core, outer ring, and weld seams. Since the steel coils are stacked vertically in the bell-type furnace, the overflowing edges of the steel coils in contact with the convection plate are bent under the extrusion of the steel coils, and the bent parts are intertwined up and down and layer by layer. When the annealed steel coils are uncoiled in the next process, namely the leveler, the bent and connected parts are torn, which seriously affects the production efficiency, yield rate and operator safety of the leveler unit.

[0003] A Chinese utility model patent, authorized with publication number CN 206143274 U, discloses a "convection plate structure" consisting of an upper plate, a middle plate, and a bottom plate. The upper plate is provided with an inner groove, a middle groove, and an outer groove, extending from the inside to the outside. The bottom plate is provided with an inner groove, a middle groove, and an outer groove, extending from the inside to the outside. The inner groove of the upper plate and the inner groove of the bottom plate are identical in position and shape. The middle groove of the upper plate and the middle groove of the bottom plate are identical in position and shape. The outer groove of the upper plate and the outer groove of the bottom plate are identical in position and depth. The radial length of the outer groove of the upper plate is greater than that of the outer groove of the bottom plate. The grooves on both sides of the convection plate weaken the overall strength of the convection plate, making it prone to deformation during use. In addition, the groove depth on each side of the convection plate is relatively shallow (only 7 mm in the embodiment). For the overflow edge of the steel coil greater than 7 mm, compression bending will still occur during the annealing process. Therefore, it is impossible to completely avoid the bending of the overflow edge of the strip.

[0004] The Chinese utility model patent with authorization announcement number CN 201746581 U discloses "a convection plate for a bell-type furnace", which includes a connecting plate, a plurality of upper fan-shaped blocks, and a plurality of lower fan-shaped blocks; the upper fan-shaped blocks are fixed to the upper end face of the connecting plate, and the upper fan-shaped blocks are arranged at intervals along the circumference, so that the inner end faces of the upper fan-shaped blocks form an upper circular hole; the lower fan-shaped blocks are fixed to the lower end face of the connecting plate, and the lower fan-shaped blocks are arranged at intervals along the circumference, so that the inner end faces of the lower fan-shaped blocks form a lower circular hole; the centers of the upper and lower circular holes are located on the same axis; the aperture of the lower circular hole is larger than that of the upper circular hole. The annular space enclosed by the lower and upper fan-shaped blocks can completely contain the overflow edge of the inner ring of the steel coil, thereby eliminating the convection plate indentation defect on the surface of the steel coil. The convection plate still adopts an integral structure, and the overflow edge is avoided by the annular space enclosed by the lower and upper fan-shaped blocks. However, the overflow edge it targets is caused by uneven winding of the first few turns of stainless steel raw coils (usually around four turns). This overflow edge is typically 20mm high, with the highest being around 30mm. This means it's only effective against overflow edges at the core and the outer edges of the coil. In actual production, steel coils typically have overflow edges at the core, center, and outer edges. Using the aforementioned convection plate cannot avoid the central overflow edge, and therefore cannot completely eliminate the bending of the overflow edge.

[0005] Summary of the Invention

[0006] The present invention provides a method for preventing the overflow and bending of the edges of steel coils during hood-type annealing. An inner convection ring and an outer convection ring are used to replace the existing convection disk with an integral structure. The diameter, width and height of the inner and outer convection rings are determined according to the specific position of the overflow edge of the steel coil (including the coil core, the middle part and the outer part) and the radial width, so that the steel coils can be stacked in the hood-type furnace completely avoiding the overflow edge, thereby eliminating the bending phenomenon of the overflow edge.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preventing overflow and bending of the edges of hood-type annealed steel coils. When the steel coils are stacked, a double-ring convection body consisting of an inner convection ring and an outer convection ring is arranged between the upper and lower steel coils. The inner convection ring and the outer convection ring each consist of a ring body and a plurality of fan-shaped blocks uniformly arranged on the ring body along the circumference. The upper and lower surfaces of the fan-shaped blocks both protrude outside the ring body and are flat. The inner convection ring and the outer convection ring are coaxially arranged. The sizes of the inner and outer convection rings are determined according to the specific position and width of the overflow edge on the steel coil, so that the inner and outer convection rings both contact the flat end surface of the steel coil in the area without overflow edge.

[0009] Furthermore, the method of preventing the curling of bell-annealed steel from overflowing and bending according to the present invention specifically comprises the following steps:

[0010] 1) Determine the location and size of the overflow edge of the steel coil;

[0011] Including the overflow edge of the coil core and its width range, the middle overflow edge and its width range, and the outer overflow edge and its width range; the width refers to the radial dimension of the overflow edge along the coil, and the width range refers to the minimum and maximum radial dimensions of the overflow edge along the circumference of the coil;

[0012] 2) Determine the dimensions of the inner and outer convection rings;

[0013] The inner and outer convection rings are manufactured according to the location and size of the overflow edge of the steel coil; the inner diameter of the inner convection ring is larger than the maximum radial dimension of the overflow edge of the steel coil core; the outer diameter of the inner convection ring is smaller than the minimum radial dimension of the overflow edge in the middle of the steel coil; the inner diameter of the outer convection ring is larger than the maximum radial dimension of the overflow edge in the middle of the steel coil, and the outer diameter of the outer convection ring is smaller than the minimum radial dimension of the overflow edge on the outer side of the steel coil; the thickness of the inner and outer convection rings are equal, and both are larger than the maximum dimension of the overflow edge relative to the axial direction of the steel coil;

[0014] 3) After cold rolling, the steel coils are bundled;

[0015] Each steel coil is bundled with two longitudinal straps wrapped around the outer ring and two transverse straps passing through the coil core. When bundling, the longitudinal straps are tightened without leaving any allowance, while the transverse straps are left with a loose allowance of 80 to 100 mm.

[0016] 4) Bell-type furnace charging;

[0017] a. Place the first layer of convection rings on the hearth of the bell-type furnace; the centers of the inner and outer convection rings in the first layer are aligned with the center of the hearth;

[0018] b. Place the first steel coil on the first convection ring; align the axis of the first steel coil with the center of the first convection disk;

[0019] c. Place a second layer of convection rings on the first steel coil; the centers of the inner and outer convection rings in the second layer are aligned with the center of the first steel coil;

[0020] d. Place the second steel coil on the second convection ring; align the axis of the second steel coil with the center of the second convection disk;

[0021] e. Place a third layer of convection rings on the second steel coil; the centers of the inner and outer convection rings in the third layer are aligned with the center of the second steel coil;

[0022] f. Place the third steel coil on the third convection ring; align the axis of the third steel coil with the center of the third convection disk;

[0023] g. Place a fourth layer of convection rings on the third steel coil; the centers of the inner and outer convection rings in the fourth layer are aligned with the center of the third steel coil;

[0024] h. Place the fourth steel coil on the fourth convection ring; align the axis of the fourth steel coil with the center of the fourth convection disk.

[0025] Furthermore, the inner convection ring and the outer convection ring are made of stainless steel, carbon structural steel or low alloy steel.

[0026] Furthermore, the heights of the inner convection ring and the outer convection ring are ≥80 mm.

[0027] Furthermore, the sizes of the inner convection ring and the outer convection ring are pre-processed into a variety of specifications for selection according to different inner diameters and outer diameters.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) The method of the present invention can completely avoid the bending phenomenon of overflow edges within a height of 40 mm when stacking bell-annealed steel coils;

[0030] 2) The method of the present invention prevents the coil's overflowing edge from bending during the bell annealing process, thereby improving the production efficiency of the next process, the skin-pass mill, and reducing downtime caused by strip edge tearing during coil uncoiling to zero.

[0031] 3) The method of the present invention can prevent the overflow edge of the steel coil from bending during the hood annealing process, and eliminate waste caused by strip tearing during the leveling machine production, thereby improving the yield rate;

[0032] 4) The overall area of ​​the double-ring convection body composed of the inner convection ring and the outer convection ring is smaller than the convection plate of the overall structure in the furnace, which improves the heat flow conductivity in the furnace and is conducive to improving the annealing quality and efficiency of the steel coil;

[0033] 5) The convection ring adopts a split structure. The total weight of the inner and outer convection rings is much smaller than the convection plate of the integral structure, which reduces the cost of spare parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a schematic diagram of an existing bell-type annealing furnace using a convection plate for stacking steel coils.

[0035] FIG2 is a front view of the double-ring counterflow body according to an embodiment of the present invention.

[0036] FIG3 is a side view of FIG2 .

[0037] FIG4 is a schematic diagram of the placement of the inner convection plate and the outer convection plate according to the present invention.

[0038] FIG5 is a schematic diagram of steel coil bundling according to the present invention.

[0039] FIG. 6 is a side view of FIG. 5 .

[0040] Figure: 1. Steel coil 2. Convection plate 3. Inner convection ring 4. Outer convection ring 5. Coil core overflow edge 6. Middle overflow edge 7. Outer overflow edge 8. Longitudinal strapping 9. Horizontal strapping DETAILED DESCRIPTION

[0041] The present invention discloses a method for preventing the overflow and bending of the edges of hood-type annealed steel coils. When the steel coils are stacked, a double-ring convection body consisting of an inner convection ring 3 and an outer convection ring 4 is arranged between the upper and lower steel coils (as shown in Figure 2); the inner convection ring 3 and the outer convection ring 4 are both composed of a ring body and a plurality of fan-shaped blocks uniformly arranged on the ring body along the circumferential direction, and the upper and lower surfaces of the fan-shaped blocks both protrude outside the ring body and are flat; the inner convection ring 3 and the outer convection ring 4 are coaxially arranged; the sizes of the inner convection ring 3 and the outer convection ring 4 are determined according to the specific position and width of the overflow edge on the steel coil, so that the inner convection ring 3 and the outer convection ring 4 are both in contact with the flat end surface of the steel coil in the area without overflow edge (as shown in Figure 4).

[0042] Furthermore, the method of preventing the curling of bell-annealed steel from overflowing and bending according to the present invention specifically comprises the following steps:

[0043] 1) Determine the location and size of the overflow edge of the steel coil;

[0044] It includes the core overflow edge and its width range, the middle overflow edge and its width range, and the outer overflow edge and its width range; the width refers to the radial dimension of the overflow edge along the steel coil, and the width range refers to the minimum and maximum radial dimensions of the overflow edge along the circumference of the steel coil;

[0045] 5) Determine the dimensions of the inner and outer convection rings;

[0046] The inner and outer convection rings are manufactured according to the location and size of the overflow edge of the steel coil; the inner diameter of the inner convection ring is larger than the maximum radial dimension of the overflow edge of the steel coil core; the outer diameter of the inner convection ring is smaller than the minimum radial dimension of the overflow edge in the middle of the steel coil; the inner diameter of the outer convection ring is larger than the maximum radial dimension of the overflow edge in the middle of the steel coil, and the outer diameter of the outer convection ring is smaller than the minimum radial dimension of the overflow edge on the outer side of the steel coil; the thickness of the inner and outer convection rings are equal, and both are larger than the maximum dimension of the overflow edge relative to the axial direction of the steel coil;

[0047] 6) After cold rolling, the steel coils are bundled;

[0048] Each steel coil is bundled with two longitudinal straps wrapped around the outer ring and two transverse straps passing through the coil core. When bundling, the longitudinal straps are tightened without leaving any allowance, while the transverse straps are left with a loose allowance of 80 to 100 mm.

[0049] 7) Bell-type furnace charging;

[0050] a. Place the first layer of convection rings on the hearth of the bell-type furnace; the centers of the inner and outer convection rings in the first layer are aligned with the center of the hearth;

[0051] b. Place the first steel coil on the first convection ring; align the axis of the first steel coil with the center of the first convection disk;

[0052] c. Place a second layer of convection rings on the first steel coil; the centers of the inner and outer convection rings in the second layer are aligned with the center of the first steel coil;

[0053] d. Place the second steel coil on the second convection ring; align the axis of the second steel coil with the center of the second convection disk;

[0054] e. Place a third layer of convection rings on the second steel coil; the centers of the inner and outer convection rings in the third layer are aligned with the center of the second steel coil;

[0055] f. Place the third steel coil on the third convection ring; align the axis of the third steel coil with the center of the third convection disk;

[0056] g. Place a fourth layer of convection rings on the third steel coil; the centers of the inner and outer convection rings in the fourth layer are aligned with the center of the third steel coil;

[0057] h. Place the fourth steel coil on the fourth convection ring; align the axis of the fourth steel coil with the center of the fourth convection disk.

[0058] Furthermore, the inner convection ring and the outer convection ring are made of stainless steel, carbon structural steel or low alloy steel.

[0059] Furthermore, the heights of the inner convection ring and the outer convection ring are ≥80 mm.

[0060] Furthermore, the sizes of the inner convection ring and the outer convection ring are pre-processed into a variety of specifications for selection according to different inner diameters and outer diameters.

[0061] The present invention discloses a method for preventing the overflow and bending of the edges of steel coils during hood-type annealing. The method replaces the existing integral convection disk by a double-ring combined convection body composed of an inner convection ring and an outer convection ring. The convection body is arranged between the upper and lower two steel coils of the vertical stack. The method can simultaneously avoid the overflow edge of the core, the overflow edge of the middle and the overflow edge of the outer side of the two steel coils, will not squeeze the overflow edge of the steel coil, and eliminates the conditions for the overflow edge of the strip to bend during the annealing process, thereby ensuring the smooth progress of the leveling process and improving the yield rate.

[0062] The inner convection ring is smaller than the outer convection ring. During furnace loading, the inner convection ring is placed first, followed by the outer convection ring in the same double-ring convection flow path. The outer convection ring is placed outside the inner convection ring. Both convection rings contact the flat end surfaces of the upper and lower coils where there is no overflow.

[0063] The inner diameter of the inner convection ring is larger than the sum of the inner diameter of the steel coil and the thickness of the coil core overflow edge, thereby avoiding the core overflow edge of the steel coil. The outer diameter of the inner convection ring is smaller than the diameter of the innermost layer of the steel coil middle overflow edge, thereby avoiding the middle overflow edge of the steel coil.

[0064] The inner diameter of the outer convection ring is larger than the outermost diameter of the overflow edge of the middle of the steel coil, thereby avoiding the overflow edge of the middle of the steel coil. The outer diameter of the outer convection ring is smaller than the innermost diameter of the overflow edge of the outer side of the steel coil, thereby avoiding the overflow edge of the side of the steel coil.

[0065] For the same cold rolling mill, the weight of the raw coil and the rolled coil is generally constant. When the same mill produces strip of the same width, the location of the rolled coil's overflow edge is essentially the same. However, the location of the rolled coil's overflow edge may vary for different cold rolling mills. The location of the overflow edge may also vary when the same cold rolling mill produces strips of different widths.

[0066] For the overflow edge caused by special requirements of merging or splitting coils, its position on the steel coil will also change. Therefore, the range of variation of the overflow edge position should be considered when designing the double-ring convection body. If the overflow edge position exceeds the normal variation range, several sets of inner and outer convection rings with different specifications and sizes can be designed and manufactured in advance and selected according to needs.

[0067] In actual production, double-ring convection bodies are used for steel coils with overflow edges; for steel coils without overflow edges, convection plates with an integral structure can still be used.

[0068] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the protection scope of the present invention is not limited to the following examples.

[0069] [Example]

[0070] In this embodiment, the following technical measures are taken to prevent the edge of the bell-annealed steel coil from overflowing and bending:

[0071] 1. Determine the position of the overflow edge of the steel coil at the end surface of the steel coil, as shown in Figure 4;

[0072] 1. The first set of overflow edges from the center of the steel coil outward is the core overflow edge 5, which corresponds to the diameter range of the steel coil is 610 to 1400 mm.

[0073] 2. The second set of overflow edges extending from the center of the steel coil outward, namely the middle overflow edges 6, corresponds to a steel coil diameter range of 1680 to 1880 mm.

[0074] 3. The third set of overflow edges from the center of the steel coil to the outside is the side overflow edge 7, and the corresponding steel coil diameter range is 2160 to 2200 mm.

[0075] 2. Determine the plane size and thickness of the double-ring contralateral body, as shown in Figures 2 to 4;

[0076] 1. The inner diameter D1 of the inner convection ring 3 is 1400 mm, and the outer diameter D2 is 1680 mm.

[0077] 2. The inner diameter D3 of the outer flow ring 4 is 1880 mm, and the outer diameter D4 is 2160 mm.

[0078] 3. The thickness of the inner convection ring 3 and the outer convection ring 4 are both 80 mm, and the distribution of the fan-shaped blocks thereon is shown in FIG2 .

[0079] 3. Determine the material of the double ring counterfluid.

[0080] In this embodiment, the inner convection ring and the outer convection ring are both made of stainless steel 1Cr18Ni9Ti.

[0081] 4. Bundling of steel coils after cold rolling, as shown in Figures 5 and 6;

[0082] Two longitudinal straps 8 are used around the outer ring of the coil; one transverse strap 9 is used on each side of the coil core. The purpose of the strapping is to prevent the coils from loosening during loading and stacking. The longitudinal straps around the outer ring of the coil should be tightened without any gaps. The transverse straps across the coil core should have a 90mm margin to prevent them from breaking under compression during loading.

[0083] 5. Bell-type furnace charging is vertical coil stacking. The specific process is as follows:

[0084] 1. Place the first layer of double-ring convection bodies on the bell-type furnace table. In this first layer, align the center of the inner convection ring with the center of the table and drop it down, while align the center of the outer convection ring with the center of the table. Once placed, the circular space within the inner diameter of the inner convection ring is reserved for the overflow edge of the core at the lower end of the first coil; the annular space between the inner and outer convection rings is reserved for the overflow edge in the middle of the lower end of the first coil; and the space outside the outer diameter of the outer convection ring is reserved for the overflow edge on the outside of the lower end of the first coil. This ensures that all overflow edges of the lower end of the first coil are not squeezed, preventing them from bending.

[0085] 2. Drop the first steel coil onto the first layer of double-ring convection disk. Align the center of the first steel coil with the center of the first layer of double-ring convection disk and drop it.

[0086] 3. Place a second layer of double-ring convection fluid on the upper end surface of the first steel coil. In the second layer of double-ring convection fluid, the center of the inner convection ring is aligned with the center of the first steel coil, that is, the inner convection ring is placed on a circular plane with a diameter of 1400-1680mm on the upper end surface of the first steel coil; the center of the outer convection ring is aligned with the center of the first steel coil, that is, the outer convection ring is placed on a circular plane with a diameter of 1880-2160mm on the upper end surface of the first steel coil. The circular space within the inner diameter of the inner convection ring is sufficient to accommodate the overflow edge of the core of the upper end surface of the first steel coil and the overflow edge of the core of the lower end surface of the second steel coil; the annular space between the inner and outer convection rings is sufficient to accommodate the overflow edge of the middle of the upper end surface of the first steel coil and the overflow edge of the middle of the lower end surface of the second steel coil; the space outside the outer diameter of the outer convection ring is sufficient to accommodate the overflow edge of the outer side of the upper end surface of the first steel coil and the overflow edge of the outer side of the lower end surface of the second steel coil.

[0087] 4. Drop the second steel coil onto the second layer of double-ring convection fluid. Align the center of the second steel coil with the center of the second layer of double-ring convection fluid and drop it.

[0088] 5. Place a third layer of double-ring convection fluid on the upper end surface of the second steel coil. In this third layer of double-ring convection fluid, the center of the inner convection ring is aligned with the center of the second steel coil, i.e., the inner convection ring is placed on a circular plane with a diameter of 1400-1680mm on the upper end surface of the second steel coil. The center of the outer convection ring is aligned with the center of the second steel coil, i.e., the outer convection ring is placed on a circular plane with a diameter of 1880-2160mm on the upper end surface of the second steel coil. The circular space within the inner diameter of the inner convection ring can simultaneously accommodate the overflow edge of the core of the upper end surface of the second steel coil and the overflow edge of the core of the lower end surface of the third steel coil; the annular space between the inner and outer convection rings can simultaneously accommodate the overflow edge of the middle of the upper end surface of the second steel coil and the overflow edge of the middle of the lower end surface of the third steel coil; the space outside the outer diameter of the outer convection ring can simultaneously accommodate the overflow edge of the outer edge of the upper end surface of the second steel coil and the overflow edge of the outer edge of the lower end surface of the third steel coil.

[0089] 6. Drop the third steel coil onto the third layer of double-ring convection fluid. Align the center of the third steel coil with the center of the third layer of double-ring convection fluid and drop it.

[0090] 7. Place a fourth layer of double-ring convection fluid on the upper end surface of the third steel coil. In this fourth layer of double-ring convection fluid, the center of the inner convection ring is aligned with the center of the third steel coil, i.e., the inner convection ring is placed on a circular plane with a diameter of 1400-1680mm on the upper end surface of the third steel coil. The center of the outer convection ring is aligned with the center of the third steel coil, i.e., the outer convection ring is placed on a circular plane with a diameter of 1880-2160mm on the upper end surface of the third steel coil. The circular space within the inner diameter of the inner convection ring can simultaneously accommodate the overflow edge of the core of the upper end surface of the third steel coil and the overflow edge of the core of the lower end surface of the fourth steel coil; the annular space between the inner and outer convection rings can simultaneously accommodate the overflow edge of the middle of the upper end surface of the third steel coil and the overflow edge of the middle of the lower end surface of the fourth steel coil; and the space outside the outer diameter of the outer convection ring can simultaneously accommodate the overflow edge of the outer edge of the upper end surface of the third steel coil and the overflow edge of the outer edge of the lower end surface of the fourth steel coil.

[0091] 8. Drop the fourth steel coil onto the fourth layer of double-ring convection fluid. Align the center of the fourth steel coil with the center of the fourth layer of double-ring convection fluid and drop it.

[0092] In this embodiment, the number of coils stacked for bell-type annealing is 4, and no double-ring convection fluid is placed on the fourth coil, and the coil stacking process is completed.

[0093] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preventing the overflow and bending of the edge of a hood-annealed steel coil, characterized in that: When the steel coils are stacked, a double-ring convection body consisting of an inner convection ring and an outer convection ring is arranged between the upper and lower steel coils; the inner convection ring and the outer convection ring are both composed of a ring body and a plurality of fan-shaped blocks uniformly arranged on the ring body along the circumferential direction, and the upper surface and the lower surface of the fan-shaped blocks both protrude outside the ring body and are flat; the inner convection ring and the outer convection ring are coaxially arranged; the sizes of the inner convection ring and the outer convection ring are determined according to the specific position and width of the overflow edge on the steel coil, so that the inner convection ring and the outer convection ring are in contact with the flat end surface of the steel coil in the area without overflow edge.

2. A method for preventing overflow and bending of the curled edge of hood-annealed steel according to claim 1, characterized in that: The specific steps include: 1) Determine the location and size of the overflow edge of the steel coil; It includes the overflow edge of the coil core and its width range, the middle overflow edge and its width range, and the outer overflow edge and its width range; the width refers to the radial dimension of the overflow edge along the steel coil, and the width range refers to the minimum radial dimension and the maximum radial dimension of the overflow edge along the circumference of the steel coil; 2) Determine the size of the inner and outer convection rings; The inner convection ring and the outer convection ring are processed according to the position and size of the overflow edge of the steel coil; wherein the inner diameter of the inner convection ring is larger than the maximum radial dimension of the overflow edge of the steel coil core; the outer diameter of the inner convection ring is smaller than the minimum radial dimension of the overflow edge in the middle of the steel coil; the inner diameter of the outer convection ring is larger than the maximum radial dimension of the overflow edge in the middle of the steel coil, and the outer diameter of the outer convection ring is smaller than the minimum radial dimension of the overflow edge on the outer side of the steel coil; the thickness of the inner convection ring and the outer convection ring are equal, and both are larger than the maximum dimension of the overflow edge relative to the axial direction of the steel coil; 3) After cold rolling, the steel coils are bundled; Each steel coil is bundled by setting two longitudinal straps wrapped around the outer ring and two transverse straps passing through the steel coil core; when bundling, the longitudinal straps are tightened without leaving any margin, and the transverse straps are left with a loose margin of 80 to 100 mm; 4) Bell-type furnace charging; a. Place the first layer of convection rings on the furnace table of the bell-type furnace; the centers of the inner convection ring and the outer convection ring in the first layer of convection rings are aligned with the center of the furnace table; b. Place the first steel coil on the first convection ring; the axis of the first steel coil is aligned with the center of the first convection disk; c. Place the second layer of convection rings on the first steel coil; the inner convection ring and the outer convection ring in the second layer of convection rings The centers are aligned with the center of the first steel coil; d. Place the second steel coil on the second convection ring; the axis of the second steel coil is aligned with the center of the second convection disk; e. Place a third layer of convection rings on the second steel coil; the centers of the inner convection ring and the outer convection ring in the third layer of convection rings are aligned with the center of the second steel coil; f. Place the third steel coil on the third convection ring; align the axis of the third steel coil with the center of the third convection disk; g. Place a fourth layer of convection rings on the third steel coil; the centers of the inner convection ring and the outer convection ring in the fourth layer of convection rings are aligned with the center of the third steel coil; h. Place the fourth steel coil on the fourth convection ring; the axis of the fourth steel coil is aligned with the center of the fourth convection disk.

3. A method for preventing overflow and bending of the curled edge of hood-annealed steel according to claim 1 or 2, characterized in that: The inner convection ring and the outer convection ring are made of stainless steel, carbon structural steel or low alloy steel.

4. A method for preventing overflow and bending of the curled edge of hood-annealed steel according to claim 1 or 2, characterized in that: The height of the inner convection ring and the outer convection ring is ≥80mm.

5. A method for preventing overflow and bending of the curled edge of hood-annealed steel according to claim 1 or 2, characterized in that: The sizes of the inner convection ring and the outer convection ring are pre-processed into various specifications for selection according to different inner diameters and outer diameters.

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