Method for grinding surface defects of steel plate for high-surface engineering machinery

Abstract

The invention discloses a steel plate surface defect coping method for high-surface engineering machinery, which relates to the technical field of metal material surface defect repair, and comprises the following steps: positioning the defect position on the surface of a steel plate, and determining the defect type and the defect size; determining a corresponding grinding area based on the defect type and the defect size of each defect; sequentially carrying out rough grinding treatment and accurate grinding treatment on the grinding area corresponding to each defect; and polishing the grinding area corresponding to each defect. Through the specific grinding area control and grading progressive grinding process, the defects are completely eliminated, the grinding area and the steel plate body are in smooth transition, the surface is smooth, grinding traces are difficult to distinguish by naked eyes, the high-value steel plate with the high surface defects is saved, and the production cost of an enterprise is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of surface defect repair technology for metallic materials, and in particular to a method for grinding surface defects on steel plates used in engineering machinery with high surface finish. Background Technology

[0002] During the production, processing, and use of high-surface-finish steel plates for engineering machinery, common surface defects such as pitting and roughness are prone to occur. These defects are mostly localized surface depressions that do not affect the strength of the steel plate itself, but severely compromise the high surface smoothness and finish, preventing the steel plate from meeting the stringent requirements of engineering machinery customers. High-surface-finish steel plates for engineering machinery have high production costs. These customers have extremely high requirements for surface smoothness and finish, falling under the high-surface-finish requirement scenario. Conventional grinding methods are not permitted to address defects, as they often only grind localized defect points, easily creating obvious steps and grinding marks between the defect and the steel plate itself, failing to meet the customer's high-surface-finish appearance and usage requirements.

[0003] If these high-surface-quality steel plates for engineering machinery with surface defects are not salvaged and are directly scrapped or reprocessed, it will result in a large amount of material waste, increased production costs, and significant economic losses for enterprises (the scrap loss of a single 9mm thick Q1100 high-surface-quality steel plate can reach 1,000-2,000 yuan / ton). In existing technologies, related grinding processes mostly focus on improving the smoothness of medium and thick stainless steel plates (such as semi-wet and fully wet graded grinding, with an emphasis on efficiency and surface roughness optimization), or the grinding-free production of extra-thick plates (with an emphasis on reducing the amount of grinding). There is a lack of a grinding method that can take into account "eliminating surface defects such as pitting and pitting, leaving no obvious grinding marks, and a smooth transition with the body". Moreover, existing sheet metal grinding processes (such as multi-level sandpaper grinding) are only suitable for removing burrs and oxide layers and are not designed for the stringent appearance requirements of high-surface-quality steel plates for engineering machinery, thus failing to solve the above-mentioned industry pain points. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for grinding surface defects of steel plates for high-surface-area engineering machinery.

[0005] To solve the above technical problems, the technical solution of the present invention is as follows: A method for repairing surface defects in steel plates used in high-surface-area engineering machinery includes: Locate the defects on the surface of the steel plate and determine the defect type and size; The corresponding grinding area is determined based on the defect type and defect size of each defect; For each defect, the corresponding grinding area is subjected to rough grinding and fine grinding in sequence. Polish the grinding area corresponding to each defect.

[0006] As a preferred embodiment of the surface defect repair method for high-surface-area engineering machinery steel plates according to the present invention, the defect types include pitting defects and pitting defects, and the defect dimensions include defect depth, defect length, defect width, and defect diameter.

[0007] As a preferred embodiment of the surface defect repair method for high-surface-area engineering machinery steel plates according to the present invention, the step of determining the corresponding repair area based on the defect type and defect size of each defect includes: Calculate the area of ​​each defect; Using the defect area as the center of the grinding area, the edges of the defect are evenly radiated outward to form a grinding area with an area 15 to 20 times the area of ​​the defect area.

[0008] As a preferred embodiment of the surface defect repair method for steel plates used in high-surface-area engineering machinery according to the present invention, the transition slope between the edge of the repair area corresponding to each defect and the surface of the steel plate is 5~10°.

[0009] As a preferred embodiment of the surface defect repair method for high-surface-area engineering machinery steel plates according to the present invention, the step of sequentially performing rough grinding and fine grinding on the repair area corresponding to each defect includes: The grinding area is rough ground using a 120-grit grinding disc, and the grinding equipment is kept at an angle of 5-10° to the steel plate surface. The grinding area is finely ground using a 240-mesh polishing pad, and the grinding equipment is kept at an angle of 5~10° to the steel plate surface.

[0010] As a preferred embodiment of the surface defect repair method for high surface finish steel plates for engineering machinery described in this invention, the grinding speed of the rough grinding is controlled at 10,000 rpm, and the grinding pressure is controlled at 20~30N.

[0011] As a preferred embodiment of the surface defect repair method for high surface finish steel plates for engineering machinery described in this invention, the grinding speed of the fine grinding is controlled at 8000 rpm, and the grinding pressure is controlled at 15~25N.

[0012] As a preferred embodiment of the surface defect repair method for high-surface-area engineering machinery steel plates according to the present invention, the polishing treatment of the repair area corresponding to each defect includes: Polish the area to be repaired using 800-grit sandpaper.

[0013] As a preferred embodiment of the surface defect repair method for high surface finish steel plates for engineering machinery described in this invention, the polishing pressure is 10~15N and the polishing time is 3~5min.

[0014] The beneficial effects of this invention are: (1) This invention achieves effective salvage of steel plates with high surface defects by expanding the grinding area and using a graded grinding process. The test results show that the success rate of defect salvage reaches more than 98%. Compared with conventional local grinding (the success rate of salvage is less than 30%), the salvage rate is greatly improved, avoiding the scrapping of high-value high-surface steel plates and significantly reducing the production cost and material waste of enterprises. Based on a single 9mm thick Q1100 high-surface steel plate, the scrapping loss can be reduced by RMB 1,000-2,000 per ton, thus improving economic benefits. At the same time, unlike the existing extra-thick plate grinding-free production process, this solution salvages surface defects such as pitting and cratering that have already occurred, rather than reducing defects from the production process. The applicable scenarios are more targeted and better reflect the core value of salvaging high-surface steel plates.

[0015] (2) This invention uses a graded progressive grinding process of “120-grit grinding disc for coarse grinding → 240-grit polishing disc for fine grinding → 800-grit sandpaper for polishing”, combined with the design of expanding the grinding area (15-20 times) and controlling the transition slope (5-10°), so that the grinding area and the steel plate body can transition smoothly without steps or obvious grinding marks. The grinding surface is smooth and delicate, and the surface roughness reaches within 10μm. After testing, it is difficult to distinguish the grinding defects with the naked eye, which fully meets the stringent requirements of customers of high-surface engineering machinery. Unlike the existing stainless steel medium and thick plate grinding process, this solution does not require the use of semi-wet or fully wet cooling methods, and does not require special sanding belts and grinding head equipment to achieve the same or even better high surface effect. It also focuses on the smoothness of the transition, solving the problems of abrupt transition, easy to leave marks, and inability to adapt to high surface requirements in the existing process.

[0016] (3) This invention uses conventional grinding tools (120-grit grinding disc, 240-grit polishing disc, 800-grit sandpaper) and equipment (handheld grinder), without the need for additional special equipment or cooling system. It is easy to operate, with clear process steps, and can be quickly promoted and applied in industrial sites. It is compatible with existing steel plate processing production lines and has low implementation costs. Compared with the existing graded grinding process, this solution reduces the operation steps by more than 30%, reduces equipment investment by more than 80%, and increases grinding efficiency by about 20%. At the same time, it avoids problems such as sand belt waste and cooling water consumption in the existing process, making it more practical. (4) This invention is mainly aimed at the surface defects of steel plates such as pitting and pitting. It can be adapted to high surface engineering machinery steel plates of different thicknesses (3-20mm) and different materials (Q1100, Q960, etc.). It is not limited by the location and size of the defects and has a high success rate of recovery. Unlike the existing large irregular steel component repair methods, this solution does not require the use of complex auxiliary tools such as 3D printing contour templates. It is simpler to operate, adaptable to conventional flat engineering machinery steel plates, and has a wider range of application scenarios. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flowchart of the surface defect repair method for high-surface-area steel plates for engineering machinery provided by the present invention; Figure 2 This is a schematic diagram of the surface of a steel plate repaired using the surface defect repair method for high-surface-area engineering machinery steel plates provided by the present invention. Detailed Implementation

[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0020] Figure 1 A flowchart illustrating the surface defect repair method for high-surface-area steel plates used in engineering machinery provided in this application is shown. The method specifically includes the following steps: Step S1: Locate the defect on the surface of the steel plate and determine the defect type and size.

[0021] Specifically, the first step is to conduct a comprehensive inspection of the steel plate surface, using a combination of visual inspection and a magnifying glass to accurately locate the position, type, and size of defects, ensuring that no defects are missed.

[0022] Among them, the defect types include pitted defects and pockmarked defects, and the defect dimensions include defect depth, defect length, defect width, and defect diameter.

[0023] Step S2: Determine the corresponding grinding area based on the defect type and defect size of each defect.

[0024] Specifically, taking the defect area as the center, the grinding area is uniformly expanded outward from the defect edge to form a grinding zone 15 to 20 times the area of ​​the defect area (if it is a circular pit, the diameter of the expanded grinding zone is 4.5 to 5 times the diameter of the defect, corresponding to an area expansion of about 20 times). This expansion ratio has been verified through multiple experiments. It can ensure that the defect area and the steel plate body can form a smooth transition after grinding, avoiding steps or obvious grinding boundaries, and also avoid material loss and reduced grinding efficiency caused by excessive expansion area. This is different from existing grinding processes that do not have a clear expansion ratio.

[0025] Preferably, the transition slope between the edge of the grinding area corresponding to each defect and the surface of the steel plate is 5~10°, ensuring a smooth transition without obvious abruptness. This slope range can effectively avoid visual abruptness at the grinding boundary, while also taking into account the flatness of the steel plate surface, solving the problem that the transition slope of the existing grinding process is not clearly controlled and is prone to leaving marks.

[0026] Step S3: Perform rough grinding and fine grinding on the grinding area corresponding to each defect in sequence.

[0027] Specifically, firstly, a 120-grit polishing disc (suitable for Q1100 high-strength steel plates to avoid damaging the steel plate itself during polishing) is used to rough grind the determined enlarged grinding area. During rough grinding, the grinding force and speed are controlled. A handheld grinder or a dedicated grinding device is used, maintaining the device at a 5-10° angle to the steel plate surface. Grinding is performed gently up and down horizontally in the same direction, with the grinding speed controlled at 10,000 rpm and the grinding pressure controlled at 20-30 N. The purpose is to quickly remove defects (roughness, pitting) and initially repair the surface of the grinding area, making the surface more flat and laying the foundation for subsequent fine grinding and polishing. At the same time, the existing semi-wet and fully wet grinding methods are avoided, eliminating the need for an additional cooling system, simplifying the operation process, and reducing implementation costs.

[0028] After rough grinding, a 240-grit polishing pad is used to fine grind the area. During fine grinding, the grinding force is adjusted (slightly less than the rough grinding force, controlled at 15~25N) to evenly grind the entire enlarged area. The grinding speed is adjusted to 8000 rpm to reduce the roughness of the surface and further eliminate the traces left by rough grinding, making the surface smoother. At the same time, it ensures a smoother transition between the area being ground and the steel plate body, avoiding over-grinding or uneven grinding in certain areas. These fine grinding parameters have been verified through experiments and can effectively connect rough grinding and subsequent polishing processes, which is different from existing fine grinding processes that only focus on roughness and ignore the smoothness of the transition.

[0029] Step S4: Polish the grinding area corresponding to each defect.

[0030] Specifically, after fine grinding, the repaired area is polished using 800-grit sandpaper. During polishing, a gentle, even pressure (controlled at 10-15N) is applied, gradually grinding in the same direction for 3-5 minutes until the surface is smooth and fine, with a smooth transition between the repaired area and the steel plate body, making grinding marks difficult to discern with the naked eye. The choice of 800-grit sandpaper has been experimentally verified, ensuring polishing effectiveness while avoiding the reduced polishing efficiency caused by excessively high grit. Unlike existing polishing processes that use high-grit abrasive belts and require a cooling system, this method is more convenient and ensures the repaired surface meets the surface finish requirements for high-quality engineering machinery steel plates.

[0031] It should be noted that during the grinding and polishing processes, metal shavings generated during grinding must be removed promptly to prevent residue from causing scratches on the ground surface and further improving the grinding effect. Handheld grinders are preferred for grinding, as they are suitable for flexible operation in industrial settings, eliminating the need for the high costs associated with large-scale grinding equipment, and are compatible with steel plates of various specifications used in engineering machinery.

[0032] The above technical solution will be further explained below through specific embodiments.

[0033] Example 1: Test material: Select a piece of steel plate for engineering machinery (material: Q1100, thickness: 9 mm, specifications: 1000mm×1000mm). The steel plate has pitting defects on its surface. The defect size is 2 mm in diameter and 0.3 mm in depth. The defects can be clearly observed with the naked eye. The defect is located in the middle of the steel plate surface and there are no other superimposed defects.

[0034] Grinding steps: 1. Defect location and grinding area determination: The location of the pit defect is accurately located by combining visual inspection with a 5x magnifying glass. The grinding area is expanded with the defect as the center. Since the defect is a circular pit (approximately 3.14 mm²), the expanded grinding area is 20 times the area of ​​the defect (approximately 62.8 mm²), and the diameter of the grinding area is 5 times the diameter of the defect (10 mm). The transition slope between the edge of the grinding area and the steel plate body is controlled at 8°. The transition edge is lightly ground with a grinding tool to ensure that there is no abruptness.

[0035] 2. Rough Grinding: Select a 120-grit alumina grinding disc (model: 100×16mm, suitable for Q1100 high-strength steel plate), and use a handheld grinder (model: Bosch GWS 10-125). Adjust the speed to 10,000 rpm, and control the grinding pressure at 25N. During grinding, keep the handheld grinder at an 8° angle to the surface of the steel plate, and gently grind horizontally up and down in the same direction for 2 minutes. During this time, remove the metal debris generated during grinding until the pitting defects are completely removed and the ground surface is initially smooth without obvious depressions or protrusions.

[0036] 3. Fine grinding: Replace with a 240-mesh silicon carbide polishing pad (model: 100×16mm), adjust the handheld grinder speed to 8000 rpm, control the grinding pressure at 20N, keep the equipment at an 8° angle to the steel plate surface, and evenly grind the entire enlarged grinding area for 3 minutes. During the grinding, observe the grinding surface multiple times to eliminate the traces left by rough grinding, make the surface smooth, and make the grinding area transition smoothly with the steel plate body.

[0037] 4. Polishing treatment: Use 800-grit alumina sandpaper (model: 230×280mm) with a light and even force (12N) to polish the grinding area in the same direction (horizontal direction) for 3 minutes. During the polishing, the sandpaper contact surface is changed continuously to avoid sandpaper residue scratching the surface until the grinding surface is smooth and delicate, and the grinding area transitions smoothly with the steel plate body.

[0038] 5. Test Results: After grinding, the surface of the steel plate was indistinguishable from the grinding defect area by visual inspection (at a distance of 50cm); there was no obvious step feel when touched, and the surface was flat and smooth; the surface roughness was measured to be 8.5μm (≤10μm) using a roughness tester; the ground steel plate was sent to the engineering machinery customer for inspection, and the customer reported that it met the surface appearance requirements and had no obvious grinding marks, successfully salvaging the defective steel plate.

[0039] 6. Comparative Test: When using conventional local grinding technology (grinding only the defective points without expanding the area, coarse grinding + fine grinding) to treat Q1100 steel plates of the same specifications and with the same defects, the grinding marks are clearly visible to the naked eye after grinding, the surface has a noticeable step-like feel, and the roughness is 18μm. The customer does not accept this and it cannot be salvaged. Using the existing semi-wet grinding technology for medium and thick stainless steel plates requires an additional cooling system, which increases equipment investment and makes the operation more complicated. Moreover, slight marks are still present in the transition area after grinding, which does not meet the stringent requirements of engineering machinery customers.

[0040] Example 2: Test material: Select a piece of engineering machinery steel plate (material: Q960, thickness: 12 mm, specifications: 1200mm×1200mm). The steel plate has a pitted defect on its surface. The defect size is 20mm² (irregular shape) and 0.2mm deep. The defect can be clearly observed with the naked eye. The defect is located at the edge of the steel plate surface.

[0041] Grinding steps: 1. Defect location and grinding area determination: The area of ​​the pitted surface defect is accurately located by combining naked eye and 5x magnifying glass. The grinding area is expanded to 15 times the area of ​​the defect (300mm²) with the defect area as the center. The expanded grinding area is irregular in shape, and the boundary is kept at a uniform distance from the edge of the defect. The transition slope between the edge of the grinding area and the steel plate body is controlled at 6°.

[0042] 2. Rough grinding: Select a 120-grit alumina grinding disc (model: 100×16mm), use a handheld grinder, adjust the speed to 10000 rpm, control the grinding pressure at 28N, keep the equipment at a 6° angle to the steel plate surface, and gently grind horizontally up and down in the same direction for 3 minutes. Remove metal debris in time until the pitting defects are completely removed and the surface is initially smooth.

[0043] Fine grinding: Replace with a 240-mesh silicon carbide polishing pad, adjust the rotation speed to 8000 rpm, control the grinding pressure at 22N, and evenly grind the entire enlarged grinding area for 4 minutes to eliminate rough grinding marks and make the surface smooth.

[0044] Polishing: Use 800-grit alumina sandpaper and polish in the same direction with a force of 13N for 4 minutes to complete the final polishing.

[0045] Test results: After grinding, the grinding marks were indistinguishable to the naked eye, and there was no step-like feel when touched. The surface roughness was 7.2μm. The customer approved the work after inspection, and the defective steel plate was successfully salvaged. Compared with conventional grinding processes, the salvage cost was reduced by 70%, and the grinding efficiency was increased by 25%.

[0046] Therefore, the technical solution of this application achieves complete elimination of defects, smooth transition between the grinding area and the steel plate body, and a smooth surface with grinding marks that are difficult to distinguish with the naked eye through specific grinding area control and graded progressive grinding process. This meets the high surface requirements of customers, saves high-value steel plates with high surface defects, significantly reduces the production cost of enterprises, and does not require the addition of special equipment. It solves the problems of high investment, complex operation and inability to adapt to high surface requirements of existing grinding processes.

[0047] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for repairing surface defects in steel plates used in high-surface-area engineering machinery, characterized in that: include: Locate the defects on the surface of the steel plate and determine the defect type and size; The corresponding grinding area is determined based on the defect type and defect size of each defect; For each defect, the corresponding grinding area is subjected to rough grinding and fine grinding in sequence. Polish the grinding area corresponding to each defect.

2. The method for repairing surface defects in high-surface-area steel plates for engineering machinery according to claim 1, characterized in that: The defect types include pitted defects and pockmarked defects, and the defect dimensions include defect depth, defect length, defect width, and defect diameter.

3. The method for repairing surface defects in high-surface-area steel plates for engineering machinery according to claim 2, characterized in that: The process of determining the corresponding grinding area based on the defect type and defect size of each defect includes: Calculate the area of ​​each defect; Using the defect area as the center of the grinding area, the edges of the defect are evenly radiated outward to form a grinding area with an area 15 to 20 times the area of ​​the defect area.

4. The method for repairing surface defects in high-surface-area engineering machinery steel plates according to claim 3, characterized in that: The transition slope between the edge of the grinding area corresponding to each defect and the surface of the steel plate is 5~10°.

5. The method for repairing surface defects in high-surface-area steel plates for engineering machinery according to claim 1, characterized in that: The process of sequentially performing rough grinding and fine grinding on the grinding area corresponding to each defect includes: The grinding area is rough ground using a 120-grit grinding disc, and the grinding equipment is kept at an angle of 5-10° to the steel plate surface. The grinding area is finely ground using a 240-mesh polishing pad, and the grinding equipment is kept at an angle of 5~10° to the steel plate surface.

6. The method for repairing surface defects in high-surface-area engineering machinery steel plates according to claim 5, characterized in that: The grinding speed of the coarse grinding is controlled at 10,000 rpm, and the grinding pressure is controlled at 20~30N.

7. The method for repairing surface defects in high-surface-area steel plates for engineering machinery according to claim 5, characterized in that: The grinding speed for fine grinding is controlled at 8000 rpm, and the grinding pressure is controlled at 15~25N.

8. The method for repairing surface defects in high-surface-area engineering machinery steel plates according to claim 1, characterized in that: The polishing process for the grinding area corresponding to each defect includes: Polish the area to be repaired using 800-grit sandpaper.

9. The method for repairing surface defects in high-surface-area engineering machinery steel plates according to claim 8, characterized in that: The polishing pressure is 10~15N, and the polishing time is 3~5min.

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