A method for controlling scratches during the shearing process of cold-rolled electroplated tinplate

Abstract

The present invention discloses a method for controlling scratches during the shearing process of cold-rolled electroplated tinplate, mainly solving the technical problems of scratch defects, surface corrosion at the scratched parts, and reduction of the aesthetic degree of cold-rolled electroplated tinplate during the shearing process of cold-rolled electroplated tinplate with a tin layer thickness of ≥2.8 g / m 2 The technical solution is as follows: A method for controlling scratches during the shearing process of cold-rolled electroplated tinplate includes the steps of loading and uncoiling, dust removal, straightening, shearing, conveying, and stacking a cold-rolled electroplated tinplate coil to obtain a finished cold-rolled electroplated tinplate; in the shearing step, the shear gap is 10 ± 1% of the thickness of the cold-rolled electroplated tinplate, and the flatness of the blade is ≤0.005 mm; in the conveying step, the sheared cold-rolled electroplated tinplate is conveyed by a belt, and the distance between the forward and backward cold-rolled electroplated tinplates after shearing on the main conveying belt and the overlapping belt is 30 ± 20 mm. The cold-rolled electroplated tinplate of the present invention is used for the preparation of food cans and milk powder cans.

Description

Technical Field

[0001] The present invention relates to a method for controlling scratches on cold-rolled electroplated tin steel sheets, and particularly to a method for controlling scratches during the shearing process of cold-rolled electroplated tin steel sheets. Specifically, it relates to a method for manufacturing cold-rolled electroplated tin steel sheets with high surface quality requirements and no visible scratch defects under visual conditions, and a method for controlling scratches on cold-rolled electroplated tin steel sheets used for food cans and milk powder cans, belonging to the technical field of metal processing. Background Art

[0002] From a microstructural perspective, cold-rolled electroplated tin steel sheets mainly consist of three parts: a surface pure tin layer, an intermediate tin-iron alloy layer, and a base steel layer. Cold-rolled electroplated tin steel sheets combine the advantages of the strength and formability of steel, the non-toxicity, corrosion resistance, solderability of tin, and the beautiful appearance, so they are widely used in packaging industries such as food and milk powder cans.

[0003] Currently, the tin coating amount of cold-rolled electroplated tin steel sheets used in mainstream packaging industries such as food and milk powder cans is mainly ≥2.8 g / m 2 . After the electroplated tin steel coil is produced, it must be cut into steel sheets of specific sizes for further processing (steps such as yellow coating, printing, glazing, slicing, rounding, and welding), and this process is called the shearing process, which can be divided into several steps such as loading and uncoiling, straightening, shearing, conveying, and stacking according to the steps.

[0004] For cold-rolled electroplated tin steel sheets with a tin layer thickness of ≥2.8 g / m 2 , the thickness of the surface pure tin layer is ≥2.0 g / m 2 . Due to the relatively soft texture of metallic tin, scratch defects are extremely likely to occur during the shearing process, resulting in a significant decrease in the aesthetics of cold-rolled electroplated tin steel sheets. The surface of the scratched part is prone to corrosion, and the corrosion resistance is poor, seriously affecting the subsequent processing and use of cold-rolled electroplated tin steel sheets.

[0005] Previously, for tin-coated products used for making food cans, milk powder cans, etc., downstream users had a relatively high tolerance for scratch defects during processing due to the large coating thickness and strong covering ability of the coating film. However, with the development trend of lighter coating weights and more transparent printing in the coating and printing industries, downstream users have put forward higher requirements for appearance, that is, cold-rolled electroplated tin steel sheets have no visible scratch defects under visual conditions.

[0006] In the existing technologies for controlling surface scratches on cold-rolled electroplated tin steel sheets, cold-rolled electroplated tin steel coils with a tin layer thickness of ≥2.8 g / m 2 are extremely prone to scratch defects during processing into cold-rolled electroplated tin steel coils, resulting in a significant decrease in the aesthetics of cold-rolled electroplated tin steel sheets. The surface of the scratched part is prone to corrosion, unable to meet the user's usage requirements, and causing quality objections resulting in losses and compensation.

[0007] In the existing control technology, due to the single uncoiling method during shearing, the uncoiling method is not selected in combination with the coating thickness on the upper and lower surfaces of cold-rolled electroplated tinplate; there is inevitably floating ash (mainly tin oxide) on the surface of cold-rolled electroplated tinplate, which is likely to accumulate in the straightening machine roller box during the shearing process to form hard objects and cause scratches; during the shearing process, the wear of the scissor edges is aggravated, and the burr degree of the shearing surface of cold-rolled electroplated tinplate becomes heavier, causing stacking scratches; the relative displacement during the lap joint of the front and rear strip steel during the conveying process causes scratch defects; during the stacking process, the lack of an air cushion or unreasonable setting of the compressed air pressure causes scratch defects. The above are the prone points and key points of scratch defects caused by the existing technology.

[0008] The Chinese patent with the application publication number CN201227654Y discloses a scratch-proof throwing plate for a transverse cutting unit, and the Chinese patent with the application publication number CN108425139A discloses a method for eliminating the scratch defects on the high-tin surface of K-plate. The Chinese patent with the application publication number CN203033423μ discloses a scratch-proof device for coated tinplate, which focuses on the improvement of equipment such as throwing plates, roller diameter correction matching, and transition bridge plates.

[0009] In the existing technology, there is a lack of an effective control method for the surface scratches of cold-rolled electroplated tinplate. Summary of the Invention

[0010] The purpose of the present invention is to provide a scratch control method for the shearing process of cold-rolled electroplated tinplate, mainly to solve the technical problems of scratch defects, surface corrosion at the scratch parts, and reduction of the aesthetics of cold-rolled electroplated tinplate during the shearing process of cold-rolled electroplated tinplate with a tin layer thickness of ≥2.8 g / m 2 The method of the present invention realizes the manufacture of cold-rolled electroplated tinplate with high surface quality.

[0011] The technical idea of the present invention is that through years of research, the applicant has found that the surface scratches during the shearing of cold-rolled electroplated tinplate are mainly affected by the shearing process parameters. The applicant optimizes the problem of easy scratch generation of cold-rolled electroplated tinplate with different thickness tin coatings by setting the shearing uncoiling method according to the principle of the thick coating surface facing up, prevents scratches caused by the accumulation of black ash in the straightening machine by arranging dust removal rollers at the entrance of the straightening machine, reduces scratches during the shearing operation by controlling the warping degree, reduces scratches during the stacking process by controlling the burr value of the shearing surface, avoids scratches caused by the lap joint of strip steel on the conveyor belt by setting the conveying parameters, and further prevents scratches generated during the stacking process by reasonably setting the compressed air pressure; through the control of each key point in the shearing process, the requirements of no directly visible scratch defects, L warp ≤ 20 mm (suspension method), and burr value of the shearing surface ≤ 20 μm for the cold-rolled electroplated tinplate after shearing are achieved under visual conditions.

[0012] The technical solution adopted by the present invention is a scratch control method for the shearing process of cold-rolled electroplated tinplate, and the method includes:

[0013] Steps of feeding, uncoiling, dust removal, straightening, shearing, conveying and stacking a cold-rolled electroplated tin steel sheet coil to obtain a finished cold-rolled electroplated tin steel sheet; the thickness of the cold-rolled electroplated tin steel sheet is 0.18 - 0.50 mm, and the thickness of the tin plating layer on the surface of the cold-rolled electroplated tin steel sheet is 2.8 - 5.6 g / m 2 , and the coatings on the upper and lower surfaces of the cold-rolled electroplated tin steel sheet are coatings with equal thickness or different thicknesses;

[0014] In the feeding and uncoiling step, when the thick plating surface faces upward, the uncoiling is carried out by the upper uncoiling method; when the thick plating surface faces downward, the uncoiling is carried out by the lower uncoiling method;

[0015] In the dust removal step, a sticky dust removal roller with automatic cleaning is arranged at the entrance of the straightening machine. The viscosity value of the dust removal roller is 1.75 ± 0.2 N, the cleaning cycle of the dust removal roller is 3 ± 1 hour, and the cleaning time is 3 ± 2 minutes;

[0016] In the straightening step, the insertion amount at the entrance of the straightening machine is 4.2 ± 2.2 mm, and the insertion amount at the exit of the straightening machine is 2.1 ± 2.1 mm;

[0017] In the shearing step, the shear gap amount is 10 ± 1% of the thickness of the cold-rolled electroplated tin steel sheet, the flatness of the blade is ≤ 0.005 mm, the shearing speed of the shear is 50 - 80 cuts / minute, and the length of the steel sheet after shearing is 600 - 1050 mm;

[0018] In the conveying step, the sheared cold-rolled electroplated tin steel sheet is conveyed by a belt. The distance between the front and rear cold-rolled electroplated tin steel sheets after shearing on the main conveying belt and the overlapping belt is 30 ± 20 mm, and the speeds of the main conveying belt and the overlapping belt are 60 ± 28 m / min;

[0019] In the stacking step, when the cold-rolled electroplated tin steel sheet is transported to the stacking lifting table through the overlapping belt, it is assisted by blowing with compressed air, and the pressure of the compressed air is 3 - 5 kg.

[0020] The burr value of the shear surface of the finished cold-rolled electroplated tin steel sheet produced by the method of the present invention is ≤ 20 μm; measured by the hanging method, the L warp of the finished cold-rolled electroplated tin steel sheet is ≤ 20 mm; there are no scratch defects visible to the naked eye on the surface of the finished cold-rolled electroplated tin steel sheet under visual conditions.

[0021] The reasons for adopting the production process of the present invention are as follows:

[0022] 1. Setting of the uncoiling method

[0023] According to the coating thickness of the incoming cold-rolled electroplated tin steel coil, the present invention selects the upper uncoiling or lower uncoiling method, aiming to use the side with the thicker tin layer as the upper surface for production. Specifically, for cold-rolled electroplated tin steel coils with equal coating thickness, the upper uncoiling method is adopted; for cold-rolled electroplated tin steel coils with different coating thicknesses, if the coating thickness of the upper surface is larger, the upper uncoiling method is adopted, and if the coating thickness of the lower surface is larger, the lower uncoiling method is adopted. By adopting this production method, for cold-rolled electroplated tin steel coils with different coating thicknesses, it avoids the contact between the thick coating surface and mechanical devices such as the roll system, belt or turning plate of the shearing unit, which helps to eliminate the problem of easy scratching of the thick coating.

[0024] 2. Setting of dust removal parameters

[0025] There is inevitably floating ash (mainly tin oxide) on the surface of cold-rolled electroplated tin steel plates, and the degree increases with the increase of the tin plating amount of the cold-rolled electroplated tin steel coil. The straightening machine roller box of the shearing unit is a closed space, and the aggregation of floating ash will form hard objects, which easily cause scratches on the cold-rolled electroplated tin steel plates during the straightening process. Conventional shearing units need to actively clean the straightening machine roller box regularly or passively and irregularly, which affects production efficiency and increases the workload.

[0026] The present invention arranges sticky dust removal rollers with automatic cleaning at the entrance of the straightening machine, with a total of three pairs of dust removal rollers, one for use and one for standby, equipped with an automatic cleaning device. The cleaning liquid is industrial alcohol with a purity of 97±2%. It removes floating ash by physical adhesion, prevents the aggregation of floating ash in the straightening roller box, and improves the cleanliness of the surface of cold-rolled electroplated tin steel plates; the viscosity value of the dust removal rollers is 1.75±0.2N. If the viscosity is too large, it will affect the operation of the cold-rolled electroplated tin steel plates, and if it is too small, it will affect the effect of removing floating ash. Through reverse inspection and testing, the ash removal effect is the best within this viscosity value range, and the degree of black ash is ≤2 levels.

[0027] When the dust removal roller surface is saturated with adsorbed floating ash, it will affect the dust removal effect, and the dust removal rollers need to be cleaned regularly. When one pair of rollers is being cleaned, the other two pairs of rollers are performing dust removal. Repeat this process to maintain the state of the roller surface. The cleaning cycle of the dust removal rollers is 3±1 hours, and the cleaning time is 3±2 minutes, which can be set according to the degree of floating ash on the surface of the incoming cold-rolled electroplated tin steel plates.

[0028] 3. Setting of straightening parameters

[0029] After the unstraightened cold-rolled electroplated tin steel coil is sheared, the steel plate has warping along the length direction, called L warp. The steel plate in an arched shape in the length direction will rub against mechanical devices such as the roll system, belt or turning plate of the shearing unit, causing scratch defects. The insertion amount range at the entrance of the straightening machine is 4.2±2.2mm, and the insertion amount range at the exit is 2.1±2.1mm, realizing full straightening of the steel strip, which helps to eliminate scratches caused by warping; the straightened steel plate is measured by the hanging method, and the L warp of the cold-rolled electroplated tin steel plate is ≤20mm.

[0030] 4. Setting of Shearing Parameters

[0031] The function of shearing is to cut the cold-rolled electroplated tin steel coil into steel plates of a predetermined length. As the wear of the shearing blade edge intensifies, the burr degree of the shearing surface will become heavier. If the burr value is too large, it will cause scratches during the stacking process of the forward steel plate and the rear steel plate. In the present invention, the shearing gap is set to 10 ± 1% of the thickness of the cold-rolled electroplated tin steel plate, the flatness of the blade is ≤ 0.005 mm, and the shearing speed is 50 - 80 cuts per minute, which helps to eliminate the scratches generated during the stacking process due to excessive burrs on the shearing surface. The length of the steel plate after shearing is 600 - 1050 mm, and the burr value of the shearing surface of the obtained cold-rolled electroplated tin steel plate is ≤ 20 μm.

[0032] 5. Setting of Conveying Parameters

[0033] The speed matching of each section of the existing process shearing unit is as follows:

[0034] Unit speed = shearing speed × steel plate length

[0035] Main belt speed = shearing speed × (steel plate length + spacing between forward and rear steel plates)

[0036] Lap belt speed = (1 - lap percentage) × unit speed

[0037] During the production of the existing process, after the cold-rolled electroplated tin steel plate is sheared, it passes through the main conveyor belt and the lap belt in sequence and then is stacked to form a finished product stack. The forward steel plate and the rear strip steel must be lapped on the lap belt (that is, the tail of the forward strip steel overlaps with the head of the rear strip steel). During the lapping process, due to inertia, the forward strip steel and the rear strip steel are prone to displacement and form scratches.

[0038] Different from the existing process, the present invention adjusts the lap amount of the lap belt so that there is no lap between the forward steel plate and the rear steel plate, eliminating the problem of scratch defects prone to occur in the lap belt area from the source. The specific parameter settings are as follows:

[0039] Main belt speed = lap belt speed = shearing speed × (steel plate length + spacing between forward and rear steel plates)

[0040] The spacing between the forward and rear cold-rolled electroplated tin steel plates after shearing on the main conveyor belt and the lap belt is set to 30 ± 20 mm, and the speed setting range of the main conveyor belt and the lap belt is 60 ± 28 m / min;

[0041] 6. Setting of Stacking Parameters

[0042] When the cold-rolled electroplated tin steel plate falls on the stacking lift table through the lap belt, the method of throwing plate lapping and air cushion slow descent is adopted, that is, assisted by compressed air blowing, which slows down the stacking speed. The compressed air pressure setting range is 3 - 5 kg to prevent scratches during the stacking process.

[0043] The present invention has the following positive effects compared with the prior art: 1. The production operation of the method of the present invention is simple and convenient, and the scratch control effect is good, which conforms to the development trend of lightweight coating weight and printing transparency in the coating and printing industries. 2. The present invention arranges a dust removal roller at the entrance of the straightening machine, solving the technical problem of black ash accumulation in the roller box of the straightening machine in the prior art and frequent shutdown for cleaning. 3. The present invention adjusts the speed of the shear knife, the speeds of the main belt and the lap belt, realizing zero lap of the forward and backward strip steel on the belt conveyor device, and fundamentally eliminating the problem of scratch defects easily generated in the lap belt area. 4. The burr value of the shear surface of the cold-rolled electroplated tin steel sheet produced by the method of the present invention is ≤20μm; measured by the hanging method, the L warp of the cold-rolled electroplated tin steel sheet is ≤20mm; under visual conditions, there are no directly visible scratch defects on the surface of the cold-rolled electroplated tin steel sheet, and the warping, burr value and surface cleanliness of the cold-rolled electroplated tin steel sheet after shearing are all improved. Specific Embodiments

[0044] The present invention will be further described below in conjunction with Examples 1 to 5, as shown in Tables 1 to 7.

[0045] In Examples 1 to 5, the thickness of the tin plating layer on the surface of the cold-rolled electroplated tin steel sheet is 2.8 - 5.6 g / m 2 , and the difference in coating thickness between the upper and lower surfaces of the cold-rolled electroplated tin steel sheet is the thick coating layer.

[0046] A method for controlling scratches during the shearing process of a cold-rolled electroplated tin steel sheet, the method comprising:

[0047] Steps of feeding, uncoiling, dust removal, straightening, shearing, conveying and stacking a cold-rolled electroplated tin steel sheet coil to obtain a finished cold-rolled electroplated tin steel sheet; the thickness of the cold-rolled electroplated tin steel sheet is 0.18 - 0.50 mm;

[0048] In the feeding and uncoiling step, when the thick coating layer faces upward, uncoiling is carried out by the upper uncoiling method; when the thick coating layer faces downward, uncoiling is carried out by the lower uncoiling method;

[0049] In the dust removal step, a sticky dust removal roller with automatic cleaning is arranged at the entrance of the straightening machine, the viscosity value of the dust removal roller is 1.75 ± 0.2 N, the cleaning period of the dust removal roller is 3 ± 1 hour, and the cleaning time is 3 ± 2 minutes;

[0050] In the straightening step, the insertion amount at the entrance of the straightening machine is 4.2 ± 2.2 mm, and the insertion amount at the exit of the straightening machine is 2.1 ± 2.1 mm;

[0051] In the shearing step, the shear gap amount is 10 ± 1% of the thickness of the cold-rolled electroplated tin steel sheet, the flatness of the blade is ≤0.005 mm, the shear knife speed is 50 - 80 cuts per minute, and the length of the steel sheet after shearing is 600 - 1050 mm;

[0052] In the conveying step, the cold-rolled electroplated tin steel sheets after shearing are conveyed by a belt. The distance between the main conveying belt and the overlapping belt for the forward and backward cold-rolled electroplated tin steel sheets after shearing is 30 ± 20 mm, and the speeds of the main conveying belt and the overlapping belt are 60 ± 28 m / min;

[0053] In the stacking step, when the cold-rolled electroplated tin steel sheets are transported to the stacking lifting table by the overlapping belt, they are supplemented with compressed air blowing, and the pressure of the compressed air is 3 - 5 kg.

[0054] Table 1 Coating parameters of cold-rolled electroplated tin steel sheets in the embodiments of the present invention

[0055]

[0056] Table 2 Uncoiling methods for cold-rolled electroplated tin steel sheet coils in the embodiments of the present invention

[0057]

[0058]

[0059] Table 3 Dust removal control parameters in the embodiments of the present invention

[0060]

[0061] Table 4 Straightening process control parameters in the embodiments of the present invention

[0062] Category Inlet insertion amount (mm) Outlet insertion amount (mm) The present invention 4.2±2.2 2.1±2.1 Example 1 4.2 2.0 Example 2 5.0 4.0 Example 3 3.8 1.8 Example 4 1.0 0.5 Example 5 3.5 2.6

[0063] Table 5 Shearing process control parameters in the embodiments of the present invention

[0064]

[0065] Table 6 Conveying and stacking process control parameters in the embodiments of the present invention

[0066]

[0067]

[0068] Table 7 Surface parameters of the finished cold-rolled electroplated tin steel sheets in the embodiments of the present invention

[0069]

[0070] As shown in Table 7, in Embodiments 1 - 5, the burr value of the shearing surface of the cold-rolled electroplated tin steel sheets is 10 - 13 μm; measured by the hanging method, the L warp of the cold-rolled electroplated tin steel sheets is 10 - 15 mm; under visual conditions, there are no visible scratch defects on the surface of the cold-rolled electroplated tin steel sheets.

[0071] In addition to the above embodiments, the present invention may have other embodiments. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A method for controlling scratches during the shearing process of cold-rolled electroplated tin steel sheets, the method comprises: Steps of feeding, uncoiling, dust removal, straightening, shearing, conveying and stacking a cold-rolled electroplated tin steel sheet coil to obtain a finished cold-rolled electroplated tin steel sheet; the thickness of the cold-rolled electroplated tin steel sheet is 0.18 to 0.50 mm, and the thickness of the tin plating layer on the surface of the cold-rolled electroplated tin steel sheet is 2.8 to 5.6 g / m 2 , and the coatings on the upper and lower surfaces of the cold-rolled electroplated tin steel sheet are coatings with equal thickness or coatings with different thicknesses; In the loading and uncoiling step, when the thick plating layer faces upwards, uncoil in the upper uncoiling mode; when the thick plating layer faces downwards, uncoil in the lower uncoiling mode; In the dust removal step, a sticky dust removal roller with automatic cleaning is provided at the entrance of the straightening machine. The viscosity value of the dust removal roller is 1.75 ± 0.2 N, the cleaning cycle of the dust removal roller is 3 ± 1 hour, and the cleaning time is 3 ± 2 minutes; In the straightening step, the insertion amount at the entrance of the straightening machine is 4.2 ± 2.2 mm, and the insertion amount at the exit of the straightening machine is 2.1 ± 2.1 mm; In the shearing step, the shear gap is 10 ± 1% of the thickness of the cold-rolled electroplated tin steel sheet, the flatness of the blade is ≤ 0.005 mm, the shearing speed is 50 - 80 cuts / minute, and the length of the steel sheet after shearing is 600 - 1050 mm; In the conveying step, convey the cold-rolled electroplated tin steel sheet after shearing through a belt. The distance between the forward and backward cold-rolled electroplated tin steel sheets after shearing on the main conveyor belt and the overlapping belt is 30 ± 20 mm, and the speeds of the main conveyor belt and the overlapping belt are 60 ± 28 m / min; In the stacking step, when the cold-rolled electroplated tin steel sheet is transported to the stacking lifting table through the overlapping belt, assist with blowing by compressed air, and the pressure of the compressed air is 3 - 5 kg.

2. The method for controlling scratches during the shearing process of cold-rolled electroplated tin steel sheets as described in claim 1, characterized in that the burr value of the shearing surface of the finished cold-rolled electroplated tin steel sheet is ≤ 20 μm; measured by the hanging method, the L warp of the finished cold-rolled electroplated tin steel sheet is ≤ 20 mm; there are no directly visible scratch defects on the surface of the finished cold-rolled electroplated tin steel sheet under visual conditions.

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