Method for preventing bending crack of middle plate during processing

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to a method for preventing a middle plate from bending crack in machining, which comprises the following steps of: a, optimizing hot rolling burr scaling; b, the shearing temperature of the steel plate is controlled, specifically, an air mist cooling module is installed above the steel plate to be cooled, and a plurality of cooling sprayers are adjusted; c, placing the steel plate: placing the steel plate to be treated in the shear blade device; d, circle shear adjustment: adjusting the horizontal gap of the circle shear and the overlap amount of upper and lower shear blades. According to the method, by optimizing the hot rolling burr size, controlling the shearing temperature, reasonably adjusting the horizontal gap of the circle shear and adjusting the overlapping amount, the shearing quality is improved, the quality objection is reduced, and huge economic benefits are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for preventing bending and cracking of a middle plate during processing. Background Art

[0002] The finishing line of the 3000mm medium and thick plate unit consists of a circular shear, a guillotine cross shear and a sampling and sizing shear. The cutting specifications of the circular shear are

[0003] 6~30×1500~2500×4000~18000mm, the tensile strength of the steel plate should meet σb≤710N / mm 2 , shear force 800KN.

[0004] The disc shear adopts magnetic centering and laser marking device, and uses two sets of upper and lower shear blades in the form of discs to rotate and shear both sides of the steel plate. With the increase in the production proportion of thicker steel plates, the disc shear exposes some shearing quality problems when shearing steel plates ≥20mm, causing cracks to appear on the edges of the original sheared edges of the steel plates during the reel bending process of the user. The cracking position of the steel plate appears at the edge of the steel plate, perpendicular to the length direction of the steel plate, and extends to the width direction of the steel plate, showing a triangular crack, and the crack stops inside the steel plate. Due to the quality objections caused by the bending cracks of the original sheared edges of the steel plates, huge economic losses are caused. Therefore, a method for preventing the bending cracks of medium plates is proposed to address the above problems. Summary of the invention

[0005] The object of the present invention is to provide a method for preventing bending cracks in middle plate processing, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] As an optional solution of the method for preventing bending and cracking of the middle plate processing described in the present invention, the steps of the method for preventing bending and cracking of the middle plate processing are as follows:

[0008] a. Optimize the hot rolling burr measurement;

[0009] b. Control the shear temperature of the steel plate: install the wind-mist cooling module above the steel plate to be cooled, and adjust multiple cooling nozzles.

[0010] c. Steel plate placement: Place the steel plate to be processed inside the shearing device;

[0011] d. Disc shear adjustment: adjust the horizontal gap of the disc shear and the overlap of the upper and lower shear blades.

[0012] Preferably, in step d: when the thickness of the steel plate is between 6 and 13 mm, the horizontal gap of the disc shear is adjusted to 0.5 to 1.5 mm, and the overlap of the upper and lower shear blades is adjusted to 0 to -4 mm; when the thickness of the steel plate is between 14 and 21 mm, the horizontal gap of the disc shear is adjusted to 1.5 to 3.0 mm, and the overlap of the upper and lower shear blades is adjusted to -5 to -2.5 mm; when the thickness of the steel plate is between 22 and 25 mm, the horizontal gap of the disc shear is adjusted to 2.0 to 5.0 mm, and the overlap of the upper and lower shear blades is adjusted to -9 to -4 mm.

[0013] Preferably, in step a, the hot-rolled burr lengthening is as follows: when the finished steel plate width is ≤2200 mm, the hot lengthening is 90-110 mm; when the finished steel plate width is >2200 mm, the hot lengthening is 100-120 mm.

[0014] Preferably, the shearing temperature of the disc shear is controlled between 140 and 180°C.

[0015] Preferably, before the shearing device performs the shearing process, the steel plate is temperature-controlled by starting the wind-mist cooling device, and then the steel plate is automatically transported to the inside of the shearing device for shearing.

[0016] Preferably, the shearing blade diameter of the shearing blade device is Shear blade thickness 70 ~ 80mm, shear blade material H13K, shearing speed 0.2 ~ 1.0m / s, cutter disc axial adjustment amount: ± 10mm, main drive motor power AC frequency conversion N = 160kW, 2 units, main drive reducer transmission ratio 65, cutter disc gap adjustment transmission motor power 2 × 3kW, cutter disc gap adjustment transmission reducer transmission ratio is 65, cutter disc overlap adjustment transmission motor power 3kW, cutter disc overlap adjustment transmission reducer transmission ratio 41 × 50.

[0017] Preferably, the shearing blade device comprises a transport roller, an upper disc shearing blade and a machine body, a steel plate is arranged inside the machine body, and a uniformly distributed transport roller connected to the frame is arranged at the bottom of the steel plate, an upper disc shearing blade and a lower disc shearing blade connected to the machine body are also arranged on both sides of the steel plate, and a lower support type electromagnetic disk connected to the frame is also arranged on one side of the machine body;

[0018] A chute fixedly connected to the machine body is provided below the steel plate, and two sets of edge shear blades connected to the frame are provided at one end of the chute, a tray is provided on one side of the edge shear blades, and a hopper is provided at the bottom of the tray, and a wind and mist cooling module is provided on the outer side of the steel plate.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The shearing quality of the disc shear of the present invention is greatly improved, the cross-section smoothness is significantly improved, the shearing hooks and burrs are greatly reduced, and at the same time, the quality objections of shearing processing bending and cracking caused by shearing quality are greatly reduced, and the quality objections are greatly reduced, thereby ensuring economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic diagram of the structure of a shearing blade device and a wind-mist cooling module for a method of preventing bending and cracking during mid-plate processing.

[0022] In the figure: 1. transport roller; 2. lower support electromagnetic disk; 3. upper disc shearing blade; 4. lower disc shearing blade; 5. machine body; 6. chute; 7. edge shearing blade; 8. hopper; 9. tray; 10. wind-mist cooling device; 11. atomizing air duct; 12. hollow frame; 13. steel plate. DETAILED DESCRIPTION

[0023] Example 1: Please refer to Figure 1 , the present invention provides a technical solution:

[0024] a. Optimize the hot rolling burr measurement;

[0025] b. Control the shear temperature of the steel plate: install the wind-mist cooling module above the steel plate to be cooled, and adjust multiple cooling nozzles.

[0026] c. Steel plate placement: Place the steel plate to be processed inside the shearing device;

[0027] d. Disc shear adjustment: adjust the horizontal gap of the disc shear and the overlap of the upper and lower shear blades.

[0028] In order to further optimize the above technical scheme, in step d: when the thickness of the steel plate is between 6 and 13 mm, the horizontal gap of the disc shear is adjusted to 0.5 to 1.5 mm, and the overlap of the upper and lower shear blades is adjusted to 0 to -4 mm; when the thickness of the steel plate is between 14 and 21 mm, the horizontal gap of the disc shear is adjusted to 1.5 to 3.0 mm, and the overlap of the upper and lower shear blades is adjusted to -5 to -2.5 mm; when the thickness of the steel plate is between 22 and 25 mm, the horizontal gap of the disc shear is adjusted to 2.0 to 5.0 mm, and the overlap of the upper and lower shear blades is adjusted to -9 to -4 mm.

[0029] In order to further optimize the above technical solution, in step a, the hot rolled burr length is as follows: when the finished steel plate width is ≤2200mm, the hot length is 90-110mm; when the finished steel plate width is >2200mm, the hot length is 100-120mm.

[0030] In order to further optimize the above technical solution, the shearing temperature of the disc shear is controlled between 140 and 180°C.

[0031] In order to further optimize the above technical solution, before the shearing device performs shearing, the steel plate is temperature-controlled by starting the wind and mist cooling device, and then the steel plate is automatically transported to the inside of the shearing device for shearing.

[0032] Furthermore, the shearing blade diameter of the shearing blade device is Shear blade thickness 70 ~ 80mm, shear blade material H13K, shearing speed 0.2 ~ 1.0m / s, cutter disc axial adjustment amount: ± 10mm, main drive motor power AC frequency conversion N = 160kW, 2 units, main drive reducer transmission ratio 65, cutter disc gap adjustment transmission motor power 2 × 3kW, cutter disc gap adjustment transmission reducer transmission ratio is 65, cutter disc overlap adjustment transmission motor power 3kW, cutter disc overlap adjustment transmission reducer transmission ratio 41 × 50.

[0033] The shearing blade device comprises a transport roller 1, an upper disc shearing blade 3 and a body 5. A steel plate 13 is arranged inside the body 5, and the bottom of the steel plate 13 is evenly distributed with a transport roller 1 connected to the frame. The upper disc shearing blade 3 and the lower disc shearing blade 4 connected to the body 5 are also arranged on both sides of the steel plate 13. A lower support type electromagnetic disk 2 connected to the frame is also arranged on one side of the body 5.

[0034] A chute 6 fixedly connected to the machine body 5 is also provided below the steel plate 15, and two sets of edge shearing blades 7 connected to the frame are provided at one end of the chute 6, a tray 9 is also provided on one side of the edge shearing blades 7, and a hopper 8 is provided at the bottom of the tray 9, and a wind and mist cooling module is also provided on the outer side of the steel plate 15.

[0035] In order to find out the cause of bending and cracking of steel plates during reprocessing, the following tests are first carried out:

[0036] 1 Test of the original shear edge of the steel plate without angular transverse cracks

[0037] In order to find out the reason why the original sheared edge of the steel plate cracks during the reprocessing process, a series of tests were carried out under laboratory conditions using a 25mm thick longitudinal sample of a steel plate to simulate user conditions. The sample was 350mm long and 50mm wide. One side along the length was the original sheared edge of the disc shear, and the other side was machined. The test conditions exceeded the standard requirements for the cold bending process performance of steel plates, that is, the test standard bending core diameter was adjusted from the standard D=3a (a is the thickness of the steel plate) to a larger bending core diameter of 128mm.

[0038] Experiment 1: The original shearing edge of the disc shear was retained and the bending test was performed. Half of the bending surfaces of the six specimens were the upper surface of the disc shearing surface, and the other half were the lower surface. The test results showed that the three specimens with the shearing plate surface as the lower surface, that is, the bending surface with shearing hooks, all cracked. The cracks were generated from the original shearing edge in the thickness direction from the outside to the inside, and were basically cracked through in the thickness and width directions. The shearing plate surface was the upper surface and was intact after bending.

[0039] Experiment 2: The shear edges of the disc were processed to be smooth with a processing depth of 2 to 3 mm. A bending test was performed and all six specimens were intact after bending.

[0040] Experiment 3: The original shear edge was retained, and the specimens were kept at 250℃ for 1.5h for bending test. The results of the 6 specimens after bending were the same as those in Experiment 1, that is, the lower surface of the bending surface with shear hooks were cracked, and the cracks were all caused by the original shear edge of the disc shear cracking from the outside to the inside in the thickness direction, and no cracks occurred on the upper surface of the bending surface.

[0041] Experiment 4: Specimens with burrs. The burrs were removed by machining and the drum-shaped widened part was bent. All 6 specimens were intact. The flame-cut edges and the drum-shaped widened part were retained and bent. No cracks or cracks occurred on the drum-shaped widened side of the 6 specimens. The cutting tumors left on the flame-cut edges had cracks with a width of 2mm and a depth of 3mm within the clamping range, but they did not expand in the thickness and width directions.

[0042] 2 Test on the existence of transverse cracks on the original shear edge of the steel plate

[0043] A 14mm steel plate with angular transverse cracks on the edge was used to investigate the cracking of the original shear edge under bending test conditions. At the same time, the changes in the morphology of the angular transverse cracks were observed. In order to examine its ability to withstand bending, the test used different bending centers with D of 73, 50, 30, and 20 mm.

[0044] In experiment 1, the original shear surface of the disc shear was retained, and 6 specimens with D of 73, 50, and 30 mm were used for bending tests. Regardless of whether the bending surface was the upper or lower surface of the shear, the specimens were intact; among the 4 specimens with D of 20 mm, 2 specimens with the bending surface being the upper shear surface were not cracked, and 2 specimens with the bending surface being the lower shear surface had small angular cracks of 1 to 3 mm on the shear edges. The cracks did not extend in the thickness and width directions, indicating that the stress concentration caused by the shearing and tearing parts of the shear surface is different.

[0045] Experiment 2: Bending test with corner transverse cracks and burrs retained. The original corner transverse cracks all cracked in the bending area, and as the diameter of the bending center decreased, the cracking degree and number of the corner transverse cracks increased, but did not expand in the thickness and width directions, and basically kept the original crack morphology unchanged.

[0046] Experiment 3: Corner transverse cracks, the burrs were processed to the cracks. The results were the same as those in Experiment 2 above, indicating that corner transverse cracks can directly lead to cold bending cracks, but their ability to expand in the width and thickness directions is limited.

[0047] Conclusion

[0048] Result 1: When the steel plate with the original shear edge thickness is bent and deformed, even if the bending and deformation conditions are very loose, it can also cause cracks from the edge, and the crack propagation ability is strong, and the crack can crack through the entire thickness of the steel plate, and the crack length is long;

[0049] Result 2: The main reason for the cracking of the edge of the reprocessed bending deformation is the stress concentration caused by the shear hooks and burrs on the original shear surface of the steel plate;

[0050] Result 3: When bending, steel plates with angular transverse cracks can directly lead to cold bending cracks, and as the diameter of the bending center decreases, the cracking degree and number of angular transverse cracks increase, but the expansion capacity along the thickness and width directions is limited, and the morphology of the original cracks is basically kept unchanged.

[0051] Therefore, the main reason for cracking at the edge of the reprocessed steel plate is that the circular shear originally sheared the edge of the lower surface of the steel plate, which generated a stress concentration crack source and expanded during the reprocessing and extension process. According to the national standard GB / T232-2024 "Metallic Material Bending Test Method", when the steel plate is cold bent, the stress concentration on the edge of the specimen must be treated. However, downstream manufacturing industries such as boilers and pressure vessels, especially private enterprises, often ignore the requirements of the cold bending inspection standards. During the reprocessing of the steel plate, the stress concentration phenomenon at the edge of the original sheared edge is not considered, resulting in edge cracking when the steel plate is bent and deformed.

[0052] The adjustment of the overlap between the upper and lower shear blades of the circular shear is related to the shearing thickness. As the thickness increases, the overlap decreases accordingly. Increasing the overlap is conducive to increasing the shearing part of the steel plate and reducing the shearing tearing part. However, when the overlap is too large, it may cause the steel plate to bend locally, the plate head to buckle down, and it is easy to get stuck. If the overlap is too small, the plate edge will jump out from the top of the chute. In severe cases, the steel plate cannot be sheared, and even cause parking or repeated shearing. In order to avoid friction between the shear blades of the circular shear, a certain horizontal gap should be ensured between the upper and lower shear blades. The horizontal gap depends on the strength and thickness of the steel plate. As the thickness and strength of the steel plate to be sheared increase, the horizontal gap increases appropriately. If the shear gap is too large or too small, it may cause uneven cutting sections, resulting in fish scales, layered defects or hooks in the shear section, affecting product quality.

[0053] Effect of shear temperature

[0054] During the entire shearing process, a reasonable and stable shearing temperature is crucial to adjusting the shear blade overlap and horizontal gap. If the shearing temperature is too high, the shear blade gap is difficult to adjust, and the edge is prone to shear hooks after shearing; if the temperature is too low, steel jams frequently and the edge quality is prone to stratification. Tests show that when the steel plate is in the range of 140-180℃, there are looser gap and overlap adjustment values, and the shearing quality can be guaranteed.

[0055] Effect of trimming amount

[0056] Under the same shear blade gap conditions, large trimming amount is prone to shear section quality defects, while small trimming amount is prone to shear hooks. At the same time, small trimming amount makes it impossible to cleanly remove the original steel plate corner transverse cracks after shearing, resulting in edge cracks. In addition, due to the uneven shearing amount on both sides, the force on the edge of the steel plate is uneven, causing stress concentration and affecting the quality of the steel plate edge.

[0057] Therefore, when the cutting blade diameter is Shear blade thickness 70 ~ 80mm, shear blade material H13K, shear speed 0.2 ~ 1.0m / s, cutter disc axial adjustment: ± 10mm, main drive motor power AC frequency conversion N = 160kW, 2 sets, main drive reducer transmission ratio 65, cutter disc gap adjustment transmission motor power 2 × 3kW, cutter disc gap adjustment transmission reducer transmission ratio 65, cutter disc overlap adjustment transmission motor power 3kW, cutter disc overlap adjustment transmission reducer transmission ratio 41 × 50, the process of adjusting the horizontal gap and overlap of the disc shear blade;

[0058] Adjustment of the horizontal clearance and overlap of the disc shear blades

[0059]

[0060] The shearing temperature of the disc shear is controlled at 140-180°C;

[0061] Hot burr measurement:

[0062] Finished product width ≤2200mm, hot state measurement 90~110mm;

[0063] Finished product width>2200mmHot state measurement 100~120mm

[0064] The wind-mist cooling module comprises a wind-mist cooling device 10 , an atomizing air duct 11 and a hollow frame 12 . The output end of the wind-mist cooling device 10 is connected to the hollow frame 12 , and the outer side of the hollow frame 12 is connected to multiple groups of atomizing air ducts 11 .

[0065] The wind-mist cooling device 10 includes a water pump device and an air pump device.

[0066] In order to ensure a reasonable shearing temperature, it is necessary to increase the cooling speed of the steel plate after rolling so that the shear gap can be adjusted easily and conveniently and the shearing quality can be more stable. The atomizing air duct 11 arranged at the output end of the wind-mist cooling device 10 utilizes the wind with lower pressure, flow and flow rate generated by the air pump, and the water with certain pressure, flow and flow rate is mixed and sprayed by a special nozzle to form uniformly dispersed and refined droplets, which are blown to the steel plate, thereby reducing the temperature of the steel plate. After trying the wind-mist cooling device, the shearing temperature of the 25mm steel plate can be reduced from the original 190-250°C to 140-180°C.

[0067] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. The above is only a preferred implementation of the present invention. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the protection scope of the present invention.

Claims

1. A method for preventing bending cracks in middle plate processing, characterized in that: Here are the steps: a. Optimize the hot rolling burr measurement; b. Control the shear temperature of the steel plate: install the wind-mist cooling module above the steel plate to be cooled, and adjust multiple cooling nozzles. c. Steel plate placement: Place the steel plate to be processed inside the shearing device; d. Disc shear adjustment: adjust the horizontal gap of the disc shear and the overlap of the upper and lower shear blades.

2. A method for preventing bending cracks in middle plate processing according to claim 1, characterized in that: In step d: when the thickness of the steel plate is between 6 and 13 mm, the horizontal gap of the disc shear is adjusted to 0.5 to 1.5 mm, and the overlap of the upper and lower shear blades is adjusted to 0 to -4 mm; when the thickness of the steel plate is between 14 and 21 mm, the horizontal gap of the disc shear is adjusted to 1.5 to 3.0 mm, and the overlap of the upper and lower shear blades is adjusted to -5 to -2.5 mm; when the thickness of the steel plate is between 22 and 25 mm, the horizontal gap of the disc shear is adjusted to 2.0 to 5.0 mm, and the overlap of the upper and lower shear blades is adjusted to -9 to -4 mm.

3. A method for preventing bending cracks in middle plate processing according to claim 1, characterized in that: In step a, the hot-rolled burrs are measured as follows: when the finished steel plate width is ≤2200 mm, the hot-state measurement is 90 to 110 mm; when the finished steel plate width is >2200 mm, the hot-state measurement is 100 to 120 mm.

4. A method for preventing bending cracks in middle plate processing according to claim 1, characterized in that: The shearing temperature of the disc shear is controlled between 140 and 180°C.

5. A method for preventing bending cracks in middle plate processing according to claim 1, characterized in that: Before the shearing device performs shearing, the temperature of the steel plate is controlled by starting the wind and mist cooling device, and then the steel plate is automatically transported to the inside of the shearing device for shearing.

6. A method for preventing bending cracks in middle plate processing according to claim 1, characterized in that: The shear blade diameter of the shearing blade device is φ950~φ1015mm, the shear blade thickness is 70~80mm, the shear blade material is H13K, the shearing speed is 0.2~1.0m / s, the axial adjustment amount of the cutter disc is: ±10mm, the main transmission motor power AC frequency conversion N=160kW, 2 units, the main transmission reducer transmission ratio is 65, the cutter disc gap adjustment transmission motor power is 2×3kW, the cutter disc gap adjustment transmission reducer transmission ratio is 65, the cutter disc overlap adjustment transmission motor power is 3kW, and the cutter disc overlap adjustment transmission reducer transmission ratio is 41×50.

7. A method for preventing bending cracks in middle plate processing according to claim 1, characterized in that: The shearing blade device comprises a transport roller (1), an upper disc shearing blade (3) and a body (5); a steel plate (13) is arranged inside the body (5); and the bottom of the steel plate (13) is provided with a transport roller (1) connected to the frame and evenly distributed; an upper disc shearing blade (3) and a lower disc shearing blade (4) connected to the body (5) are also arranged on both sides of the steel plate (13); and a lower support type electromagnetic disk (2) connected to the frame is also arranged on one side of the body (5); A chute (6) fixedly connected to the machine body (5) is also provided below the steel plate (13), and two sets of edge shear blades (7) connected to the frame are provided at one end of the chute (6), a tray (9) is also provided on one side of the edge shear blades (7), and a hopper (8) is provided at the bottom of the tray (9), and a wind mist cooling module is also provided on the outer side of the steel plate (13).

8. A method for preventing bending cracks in middle plate processing according to claim 1, characterized in that: The wind-mist cooling module comprises a wind-mist cooling device (10), an atomizing air duct (11) and a hollow frame (12); the output end of the wind-mist cooling device (10) is connected to the hollow frame (12), and the outer side of the hollow frame (12) is connected to multiple groups of atomizing air ducts (12).

9. A method for preventing bending cracks in middle plate processing according to claim 8, characterized in that: The wind-mist cooling device (10) comprises a water pump device and an air pump device.

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