Stacking structure for steel coils in bell-type furnace and steel coil charging and discharging method

Abstract

A stacking structure for steel coils in a bell-type furnace and a steel coil charging and discharging method. Stacked steel coils are separated by multiple convection blocks (4), the convection blocks (4) being placed to avoid locations of outside towers, and both the upper surface and the lower surface of each convection block (4) being provided with grooves (5). In the present invention, integrated convection plates (2) are modified into the form of a free combination of multiple convection blocks (4), as each convection block (4) has a simple structure, is convenient to manufacture and lightweight, and can be arranged as required in order to be more adaptable and flexible, thus helping to rationally regulate a gas volume and ensuring that outside towers of steel coils will not be folded at any position by squeezes. In addition, the convection blocks (4) can be placed just by workers without the need for a hoist, such that the auxiliary time is significantly shortened during steel coil charging and discharging processes, thus effectively improving the production efficiency of bell-type furnaces.

Description

A steel coil stacking structure in a bell-type furnace and a method for loading and unloading steel coils Technical Field

[0001] The present invention relates to the technical field of bell-type furnace production, and in particular to a steel coil stacking structure in a bell-type furnace and a method for loading and unloading the steel coils. Background Art

[0002] Hood annealing is a heat treatment method for annealing cold-rolled strip in a hood furnace in a stacked form. It can eliminate the work hardening of the cold-rolled strip and obtain good mechanical properties. After cold rolling, the strip is coiled into a steel coil and then enters the hood furnace. The steel coil is stacked in the hood furnace in an upright coil. A convection plate is usually placed between the upper and lower steel coils to ensure that the annealing medium (hydrogen) in the furnace hood flows smoothly between the stacked steel coils, so that the overall temperature of the steel coil is uniform throughout the annealing process (as shown in Figure 1). The convection plate generally consists of a middle plate with a center hole and radial fan plates evenly and spaced on the front and back of the middle plate. An air duct is formed between adjacent fan plates on the same surface.

[0003] To address the problem of conventional convection plates being unable to adjust the hot air flow rate, Chinese invention patent publication number CN 217922238 U discloses a "convection plate for a bell-type annealing furnace." The convection plate comprises a central connecting plate with removable fan-shaped assemblies mounted in an annular array at both the top and bottom ends. An annular groove is centrally defined on the outer edge of the central connecting plate, within which a fixed ring is rotatably mounted. A plurality of fan-shaped plates (II) are configured in an annular array on the outer edge of the fixed ring. These fan-shaped plates are movably mounted within the fan-shaped assemblies. The fan-shaped assemblies include a first fan-shaped plate disposed on one side of the outer edge of the central connecting plate, a central fan-shaped through groove formed toward the side of the central connecting plate, and a second fan-shaped plate movably mounted within the fan-shaped through groove. The fixed ring also includes an annular groove (I) at both the top and bottom ends. This design allows for adjustment of the gap between two adjacent fan-shaped plates, breaking through the limitation of a single function and facilitating operator adjustment of the hot air flow rate.

[0004] Some cold-rolled medium-width steel strip is produced by welding two small raw material coils together into a single large coil. Due to plate-shaped issues such as sickle bends at the ends of the raw material, a certain amount of overflow edge always exists at the weld seam. During annealing using existing convection plates, the overflow edge is easily folded due to the mutual compression between the coil and the convection plate, causing sticking during the high-temperature heat treatment process. This can lead to localized strip degradation or scrapping, seriously affecting product quality and yield. To address this issue, Chinese invention patent publication number CN 201459205 U discloses a "convection plate for a cold-rolled bell-type annealing furnace." The convection plate comprises a gear-shaped center plate with a central hole, multiple front sector plates fixed to the front of the center plate, and multiple rear sector plates fixed to the rear of the center plate. The front and rear sector plates are radially arranged and correspond to the teeth on the outer edge of the center plate. Grooves are provided on the front and rear sector plates to correspond to the annular overflow edge at the weld seam of the steel strip coil. However, in actual production, the overflow edge on the steel strip not only appears at the weld, but also has different sizes and shapes. Therefore, the technical solution of opening a groove corresponding to the overflow edge on the convection plate is obviously impractical.

[0005] A bell annealer typically loads four coils at a time, requiring three convection trays to be placed between them. During loading and unloading, the convection trays are stacked and hoisted out by an overhead crane, which takes approximately 10 minutes to complete. Therefore, stacking and hoisting the convection trays alone can take up to 60 minutes to anneal a single batch of coils, significantly impacting the bell annealer's production efficiency.

[0006] Summary of the Invention

[0007] The present invention provides a steel coil stacking structure in a bell-type furnace and a method for loading and unloading steel coils. The convection plate of the overall structure is improved into a form of free combination of multiple convection blocks. The convection blocks have a simple structure, are easy to make, and are light in weight, and can be placed as needed. Compared with the convection plate, the convection blocks are more flexible and maneuverable, which is conducive to the reasonable adjustment of the gas volume and can ensure that the overflow edge of the steel coil will not be folded due to squeezing at any position. In addition, the placement of the convection blocks does not require the participation of a crane and can be completed manually. The auxiliary time of the steel coil loading and unloading process is greatly reduced, effectively improving the production efficiency of the bell-type furnace.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A steel coil stacking structure in a bell-type furnace, wherein the stacked steel coils are separated by multiple convection blocks; the convection blocks are placed away from the position where the overflow edge is located, that is, the vertical surfaces of the steel coils in contact with the convection blocks are all planes without overflow edges; the upper and lower surfaces of the convection blocks are both flat, and the upper and lower surfaces are both provided with grooves.

[0010] Furthermore, a number of convection blocks are evenly placed along the circumferential direction between two adjacent groups of overflow edges of the steel coil.

[0011] Furthermore, the convection block has a length of 150 to 300 mm, a width of 100 to 200 mm, and a height of 60 to 100 mm.

[0012] Furthermore, the horizontal cross-section of the convection block is polygonal, circular, elliptical or other regular shapes; polygons include rectangles, triangles, trapezoids and hexagons, and other regular shapes include bows, crescents, spindles, waist drums, plum blossoms and stars.

[0013] Furthermore, the convection block is placed at an angle such that the angle between its axis and the radial direction of the steel coil is minimized while avoiding the overflow edge.

[0014] Furthermore, the groove is a semicircular groove or a long groove with a semicircular end, and the height of the groove is 5 to 10 mm.

[0015] Furthermore, the grooves are arranged in parallel with an interval of 15 to 20 mm.

[0016] Furthermore, the grooves on the upper surface and the grooves on the lower surface are arranged in a one-to-one correspondence or in an alternating manner.

[0017] A bell-type furnace steel coil unloading method comprises the following steps:

[0018] 1. The process of loading steel coils:

[0019] 1) Before loading the furnace, the operator shall place the convection block on the top of the upper vertical surface of each steel coil without overflowing edge according to the overflowing edge of each steel coil;

[0020] 2) Use an overhead crane to lift the steel coils stacked with convection blocks one by one and stack them on the furnace platform; no convection block is placed on the vertical surface of the last steel coil;

[0021] 3) The overhead crane lowers the inner cover and outer cover in sequence and places them on the furnace platform, and the steel coil loading process is completed;

[0022] 2. The process of steel coil coming out of furnace:

[0023] 1) Use an overhead crane to lift and remove the inner and outer covers;

[0024] 2) Use an overhead crane to lift each steel coil on the furnace platform one by one and place it on the ground or on a transport vehicle;

[0025] 3) The operator uses a clamp to remove the convection block on the vertical surface of the steel coil, and the steel coil unloading process is completed.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The convection plate of the integral structure is improved to a form of free combination of multiple convection blocks. The convection blocks have a simple structure, are easy to manufacture, are light in weight, and can be placed as needed;

[0028] 2) Compared with the convection plate, the convection block is more flexible and convenient for adjusting the gas volume, and can ensure that the overflow edge of the steel coil will not be squeezed and folded at any position;

[0029] 3) The placement of the convection blocks can be done manually without the involvement of a crane. The auxiliary time of the steel coil loading and unloading process is greatly reduced, effectively improving the production efficiency of the bell-type furnace;

[0030] 4) The convection blocks are placed in a dispersed manner, so that they can be freely stacked at the non-overflow edge of the steel coil facade. No matter where the steel coil overflows, there will be no squeezing or folding.

[0031] 5) The decentralized convection blocks are small and lightweight, allowing them to be manually stacked on the steel coils' facades before loading. They can then be manually removed from the facades after the coils leave the furnace. Therefore, no crane is required to lift or remove the convection blocks during loading or unloading, eliminating the need for three stacking and removal steps. This saves approximately 60 minutes of time during each loading and unloading process. Based on an average annual loading and unloading of 6,708 furnaces in a large cold rolling hood annealing shop, this saves a total of 6,708 hours, increasing the hourly production capacity of a single furnace to 1.82 tons / h and increasing annual production capacity by 12,207.34 tons.

[0032] 6) The use of distributed convection blocks increases the permeability between the upper and lower layers of steel coils in the furnace, allowing for smoother flow of the annealing medium (hydrogen) between the stacked steel coils. This improves the fluidity of hydrogen between the layers of steel coils in the bell-type annealing furnace, shortening annealing time, improving product performance, and reducing annealing medium (hydrogen, blast furnace gas, coke oven gas, and nitrogen) consumption (based on the aforementioned large cold rolling bell-type annealing shop, this reduces consumption by approximately RMB 2 million annually). Furthermore, the overall temperature of the steel coils is more uniform throughout the annealing process.

[0033] 7) Taking the example of placing 6 convection blocks between the vertical surfaces of 2 steel coils, the total weight is 82 kg, which is 1072 kg less than the weight of one convection plate (1154 kg). Based on the aforementioned large cold rolling hood-type annealing workshop, the purchase cost of the convection plates can be saved by RMB 5 million; at the same time, the safety risks of equipment damage and personal injury caused by the deformation and falling of the convection plates are eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic diagram of steel coils stacked using conventional convection trays.

[0035] FIG2 a is a front view of the steel coil stacking structure in the bell-type furnace according to the present invention.

[0036] FIG2 b is a schematic diagram of the convection block of the present invention being placed to avoid the overflow edge.

[0037] FIG3 a is a top view of the convection block according to the present invention.

[0038] FIG. 3 b is a front view of FIG. 3 a .

[0039] In the figure: 1. Steel coil 2. Convection plate 3. Overflow edge 4. Convection block 5. Groove DETAILED DESCRIPTION

[0040] As shown in Figures 2a and 2b, the present invention describes a steel coil stacking structure in a bell-type furnace, in which multiple convection blocks 4 are used to separate the stacked steel coils 1; the convection blocks 4 are placed away from the position where the overflow edge 3 is located, that is, the vertical surfaces of the steel coils 1 in contact with the convection blocks 4 are all planes without the overflow edge 3; as shown in Figures 3a and 3b, the upper and lower surfaces of the convection blocks 4 are both planes, and both the upper and lower surfaces are provided with grooves 5.

[0041] Furthermore, a number of convection blocks 4 are evenly placed along the circumferential direction between two adjacent groups of overflow edges 3 of the steel coil 1 .

[0042] Furthermore, the convection block 4 has a length of 150 to 300 mm, a width of 100 to 200 mm, and a height of 60 to 100 mm.

[0043] Furthermore, the horizontal cross-section of the convection block 4 is polygonal, circular, elliptical or other regular shapes; polygons include rectangles, triangles, trapezoids and hexagons, and other regular shapes include bows, crescents, spindles, waist drums, plum blossoms and stars.

[0044] Furthermore, the convection block 4 is placed at an angle such that the angle between its axis and the radial direction of the steel coil 1 is the smallest while avoiding the overflow edge 3 .

[0045] Furthermore, the groove 5 is a semicircular groove or a long groove with a semicircular end, and the height of the groove 5 is 5 to 10 mm.

[0046] Furthermore, the grooves 5 are arranged in parallel with an interval of 15 to 20 mm.

[0047] Furthermore, the grooves on the upper surface and the grooves on the lower surface are arranged in a one-to-one correspondence or in an alternating manner.

[0048] The method for unloading steel coils from a bell-type furnace according to the present invention comprises the following steps:

[0049] 1. The process of loading steel coils:

[0050] 1) Before loading the furnace, the operator shall place the convection block on the top of the upper vertical surface of each steel coil without overflowing edge according to the overflowing edge of each steel coil;

[0051] 2) Use an overhead crane to lift the steel coils stacked with convection blocks one by one and stack them on the furnace platform; no convection block is placed on the vertical surface of the last steel coil;

[0052] 3) The overhead crane lowers the inner cover and outer cover in sequence and places them on the furnace platform, and the steel coil loading process is completed;

[0053] 2. The process of steel coil coming out of furnace:

[0054] 1) Use an overhead crane to lift and remove the inner and outer covers;

[0055] 2) Use an overhead crane to lift each steel coil on the furnace platform one by one and place it on the ground or on a transport vehicle;

[0056] 3) The operator uses a clamp to remove the convection block on the vertical surface of the steel coil, and the steel coil unloading process is completed.

[0057] The steel coil stacking structure in a bell-type furnace of the present invention solves the following three problems:

[0058] First, it solves the problem of coil overflow edges being squeezed and folded in a bell-type annealing furnace. Since the hot-rolled strip is rolled at both ends without tension, it is prone to camber. After cold rolling, multiple groups (each with multiple layers) of overflow edges exceeding the target coil width by 10 to 35 mm are generated on the coil core, outer ring, and weld seam on both sides of the coil. Since the coils are stacked vertically in the bell-type furnace, typically separated by an integral convection plate, the overflow edges bend at the contact point between the upper and lower coils due to the compression. The bent overflow edges interlock with the upper and lower layers of the convection plates. When the coils exit the bell-type furnace and are unrolled in the next process, the strip tears at the bent and interlocked locations, seriously affecting the smoothing process and the final yield. By adopting the stacking structure for steel coils in the bell-type furnace described in the present invention, the integral convection plate is replaced by multiple convection blocks, allowing the overflow edges to be flexibly avoided when stacking the coils, effectively preventing squeeze and folding of the overflow edges.

[0059] Second, it solves the problem of the production efficiency of the hood-type furnace being affected by the stacking and lifting of the convection plate. As mentioned above, when a convection plate with an integral structure is used, it takes 60 minutes just to stack and lift out the convection plate to complete the annealing process of a furnace of steel coils, which has a significant impact on the production efficiency of the hood-type annealing furnace. The present invention uses dispersed convection blocks, which are small in size and light in weight. They can be manually stacked on the upper surface of the steel coil before the steel coil is loaded into the furnace; and they can be manually removed from the steel coil after the steel coil is taken out of the furnace. Therefore, during the process of loading and unloading the furnace, there is no need to separately lift and stack or lift and remove the convection plate. Each loading and unloading process can save 60 minutes of auxiliary time, greatly improving the production efficiency of the hood-type furnace.

[0060] Third, it solves the problem of poor gas circulation during hood annealing. By adopting the convection blocks described in the present invention, they can be freely placed according to the gas flow conditions in the furnace, and convection blocks with grooves of different shapes and directions can be selected as needed to ensure the air flow permeability between the upper and lower steel coils in the furnace. The annealing medium (hydrogen) flows more smoothly between the stacked steel coils, and the overall temperature of the steel coils is more uniform during the entire annealing process.

[0061] As shown in FIG2a and FIG2b, when the steel coil stacking structure in the bell-type furnace of the present invention is adopted, the furnace loading process of the steel coils (taking four steel coils as an example) is as follows:

[0062] 1. Before loading the furnace, the operator shall place the convection blocks on the upper surfaces of the three steel coils without overflow edges according to the overflow edges of each steel coil.

[0063] 2. Use an overhead crane to sequentially lift the three coils stacked with convection blocks and stack them on the furnace platform. The fourth and final coil to be loaded into the furnace does not require a convection block. This is because the height of the convection blocks between each coil is greater than the maximum length of the coil's overflow edge, leaving ample height clearance for the overflow edge to prevent it from being squeezed or folded.

[0064] 3. The overhead crane lowers the inner cover and outer cover in turn and places them on the furnace platform, and the steel coil loading process is completed.

[0065] The process of steel coils being unloaded from the furnace is as follows:

[0066] 1. Use an overhead crane to lift and remove the inner and outer covers.

[0067] 2. Use an overhead crane to lift the four steel coils on the furnace one by one and place them on the ground or on a transport vehicle.

[0068] 3. The operator uses a special clamp to remove the convection blocks on the vertical surfaces of three steel coils, and the steel coil unloading process is completed.

[0069] 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.

[0070] [Example]

[0071] In this embodiment, a steel coil stacking structure in a bell-type furnace is used for furnace loading.

[0072] As shown in Figures 3a and 3b, in this embodiment, the convection block 4 is a rectangular parallelepiped structure with a length of 200 mm, a width of 150 mm, and a height of 70 mm. Seven semicircular grooves 5 are defined on the upper and lower surfaces of each convection block 4. The grooves 5 are 5 mm high and are spaced 18 mm apart longitudinally along the convection block 4. The axes of the grooves 5 are parallel to the width of the convection block 4.

[0073] When loading the furnace, the convection blocks 4 are placed between two adjacent groups of overflow edges 3 on the vertical surface of the steel coil 1. In this embodiment, three convection blocks are evenly placed along the circumferential direction between the two adjacent groups of overflow edges, and the distance between two adjacent convection blocks is approximately 120 degrees.

[0074] The stacking angle of each convection block can be adjusted according to the distance between two adjacent groups of overflow edges at its location, so as to minimize the angle between the axis direction of the convection block and the radial direction of the steel coil while avoiding the overflow edges.

[0075] As shown in FIG. 2 b , taking the convection blocks 4 stacked on a steel coil 1 as an example, the overflow edges 3 on the steel coil 1 are divided into three groups, and a total of six convection blocks 4 are stacked.

[0076] 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 steel coil stacking structure in a bell-type furnace, characterized in that: Multiple convection blocks are used to separate the stacked steel coils; the convection blocks are placed away from the overflow edge, that is, the vertical surfaces of the steel coils in contact with the convection blocks are all planes without overflow edges; the upper and lower surfaces of the convection blocks are both planes, and both the upper and lower surfaces are provided with grooves.

2. The steel coil stacking structure in a bell-type furnace according to claim 1, characterized in that: Several convection blocks are evenly placed along the circumferential direction between two adjacent groups of overflow edges of the steel coil.

3. The steel coil stacking structure in a bell-type furnace according to claim 1, characterized in that: The convection block has a length of 150 to 300 mm, a width of 100 to 200 mm, and a height of 60 to 100 mm.

4. The steel coil stacking structure in a bell-type furnace according to claim 1, characterized in that: The horizontal cross-section of the convection block is polygonal, circular, elliptical or other regular shapes; polygons include rectangles, triangles, trapezoids and hexagons, and other regular shapes include bows, crescents, shuttles, waist drums, plum blossoms and stars.

5. The steel coil stacking structure in a bell-type furnace according to claim 1, characterized in that: The convection block is placed at an angle such that the angle between its axis direction and the radial direction of the steel coil is the smallest while avoiding the overflow edge.

6. The steel coil stacking structure in a bell-type furnace according to claim 1, characterized in that: The groove is a semicircular groove or a long groove with a semicircular end, and the height of the groove is 5 to 10 mm.

7. The steel coil stacking structure in a bell-type furnace according to claim 1, characterized in that: The grooves are arranged in parallel with an interval of 15 to 20 mm.

8. The steel coil stacking structure in a bell-type furnace according to claim 1, characterized in that: The grooves on the upper surface and the grooves on the lower surface are arranged one by one or alternately.

9. A method for unloading a steel coil from a furnace according to any one of claims 1 to 8, characterized in that: The steps include:

1. The process of loading steel coils: 1) Before loading the furnace, the operator shall place the convection blocks on the top of the upper surface of each steel coil without overflow edge according to the overflow edge of each steel coil; 2) Use an overhead crane to lift the steel coils stacked with convection blocks one by one and stack them on the furnace platform; no convection block is stacked on the vertical surface of the last steel coil; 3) The overhead crane sequentially lowers the inner cover and the outer cover and places them on the furnace platform, and the steel coil loading process is completed; 2. The process of steel coil coming out of furnace: 1) Use an overhead crane to lift and remove the inner and outer covers; 2) Use an overhead crane to lift each steel coil on the furnace platform one by one and place it on the ground or on a transport vehicle; 3) The operator uses a clamp to remove the convection block on the vertical surface of the steel coil, and the steel coil out of the furnace process is completed.

Images