Surface anti-nodular treatment process for tension roller and deflection roller of continuous annealing line annealing furnace

Abstract

The application relates to a surface anti-nodular treatment process for tensioning rollers and turning rollers of a continuous annealing line, and belongs to the technical field of continuous annealing equipment for cold-rolled strip steel in metallurgical engineering. The technical scheme is as follows: pretreatment: the roller surfaces of the tensioning rollers and the turning rollers are cleaned to remove the attached oxide scales, oil stains and impurity particles on the surfaces, and the roller surfaces are subjected to drying treatment; (2) roller surface coating: the coating comprises a bottom layer spraying and a surface layer spraying, the nickel-chromium alloy powder is selected as the bottom layer material and is sprayed on the roller surface, and the metal ceramic is selected as the surface layer material and is sprayed on the bottom layer coating; (3) post-treatment: after the spraying is completed, the roller surfaces are subjected to tempering treatment to eliminate the internal stress of the coating, and the roller surfaces are subjected to polishing and grinding. The application has the beneficial effects that the hardness, wear resistance and anti-adhesion of the roller surfaces are improved through the composite surface treatment means, the generation of nodules on the roller surfaces is inhibited from the root, the service life of the equipment is prolonged, and the stable product quality of the strip steel is ensured.

Description

Technical Field

[0001] This invention relates to a process for anti-nodulation treatment of the surface of tension rolls and guide rolls in a continuous annealing furnace, belonging to the technical field of continuous annealing equipment for cold-rolled strip steel in metallurgical engineering. Background Technology

[0002] Tensioning rolls and guide rolls are crucial equipment in continuous annealing units for cold-rolled strip steel. Tensioning rolls are the core components for controlling strip tension and guiding its transmission, and are the key equipment for regulating the strip's running trajectory. Guide rolls are also the core equipment for regulating the strip's running trajectory. Tensioning rolls and guide rolls operate in high-temperature environments for extended periods. During actual production, impurities such as iron oxide scale, iron powder, and zinc particles that detach from the strip surface easily adhere to and accumulate on the surfaces of tensioning rolls and guide rolls, gradually forming hard nodules. These nodules directly cause defects such as scratches and indentations on the strip surface, leading to strip deviation, wrinkling, and even strip breakage. This not only results in a decline in the grade of cold-rolled strip steel products and damage to the company's economic benefits, but also significantly increases the frequency of unit shutdowns for maintenance and equipment maintenance costs.

[0003] Currently, the surface strengthening processes for tension rolls mostly employ traditional technologies such as hard chrome plating and conventional thermal spraying. However, these processes have significant limitations: the hard chrome plating layer is prone to hardness decay and peeling under high-temperature conditions; the bonding strength between the conventional thermal spray coating and the roll substrate is low, and its anti-adhesion performance is insufficient, making it difficult to resist the formation of nodules and wear over a long period. Frequent roll changes and maintenance operations severely affect the production continuity of continuous annealing units, failing to meet the technical requirements of modern cold-rolled strip steel production for high equipment reliability and long service life.

[0004] The strengthening processes for the surface of steering rollers are mostly periodic offline grinding, replacement of roller body or single coating protection. Offline maintenance will interrupt the production rhythm, while single coating has problems such as weak adhesion to the roller body substrate and insufficient high temperature resistance, which are difficult to adapt to the harsh working conditions of continuous annealing workshops, and the anti-nodulation effect is not long-lasting.

[0005] Therefore, developing a surface treatment method for tension rolls and guide rolls that is suitable for the production conditions of continuous annealing furnaces, easy to operate, and has a stable anti-nodulation effect is of great significance for improving product quality, reducing operation and maintenance costs, and ensuring the efficient and stable operation of the production line. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a surface anti-nodulation treatment process for tension rollers and steering rollers in continuous annealing furnaces. Through composite surface treatment, the hardness, wear resistance and anti-adhesion of the roller surface are improved, thereby inhibiting the formation of nodules on the roller surface from the root, extending the service life of the equipment and ensuring the stable quality of strip products.

[0007] The technical solution of this invention is: A process for anti-nodulation treatment of the surface of tension rolls and guide rolls in a continuous annealing line includes the following steps: (1) Pretreatment: Clean the surface of the tensioning roller and the steering roller to remove the iron oxide scale, oil stains and impurity particles attached to the surface, and dry the roller surface; (2) Roller surface coating: includes base layer spraying and top layer spraying. The base layer spraying uses nickel-chromium alloy powder as the base material and sprays it on the roller surface to form a base layer coating of a certain thickness. The top layer spraying uses metal ceramic as the top layer material and sprays it on the base layer coating to form a top layer coating of a certain thickness on the surface of the base layer coating. (3) Post-treatment: After the spraying is completed, the roller surface is tempered to eliminate the internal stress of the coating, and the roller surface is polished.

[0008] In step (2), the base coat uses Ni60Cr15 nickel-chromium alloy powder as the base material, and its coating thickness is 15-20μm; the top coat uses DPC-74 cermet as the top material, and its coating thickness is 40-70μm.

[0009] In step (2), the bottom layer is sprayed using a supersonic flame spraying process with a spraying distance of 180-220mm and a spraying temperature of 800-900℃; the top layer is sprayed using an explosive spraying process with a spraying distance of 100-120mm and a spraying temperature of 1200-1400℃.

[0010] In step (3), the roller surface is subjected to low-temperature tempering treatment at a temperature of 150-200℃ and a holding time of 1.5-2.5h. The roughness of the roller surface after polishing and grinding is Ra4-Ra6μm. The preprocessing in step (1) is specifically performed as follows: a. Mechanical grinding: The surface of the tension roller is rough ground with a grinding wheel to remove the original oxide scale, rust and old coating on the roller surface; b. Cleaning and degreasing: Clean the roller surface for 20-30 minutes at a temperature of 50-60℃ and an ultrasonic frequency of 40kHz using an alkaline degreasing agent to remove oil and impurities. c. Drying and activation: Drying is carried out in a hot air drying oven at a temperature of 80-100℃, followed by activation treatment of the roller surface for 10-15 minutes. The beneficial effects of this invention are: it can significantly improve the surface finish of tension rolls and guide rolls, reduce roughness, reduce nodules on the roll surface from the source, avoid strip steel scratch defects, and improve the finished product qualification rate; it can effectively curb the escalation of downtime accidents, reduce the number of unplanned downtimes, and ensure the continuous and efficient operation of the production line; it can extend the service life of the roll body and furnace body, reduce equipment maintenance and spare parts costs, and at the same time reduce the labor intensity of personnel and reduce operational safety risks. Attached Figure Description

[0011] Figure 1 This is a schematic diagram illustrating the surface roughness of the tension roller of the present invention; Figure 2 This is a schematic diagram illustrating the surface roughness of the steering roller of the present invention; Detailed Implementation

[0012] The invention will be further described below with reference to the accompanying drawings and examples.

[0013] See attached document Figure 1 , 2 A process for anti-nodulation treatment of the surface of tension rolls and guide rolls in a continuous annealing line includes the following steps: (1) Pretreatment: Clean the surface of the tensioning roller and the steering roller to remove the iron oxide scale, oil stains and impurity particles attached to the surface, and dry the roller surface; (2) Roller surface coating: includes base layer spraying and top layer spraying. The base layer spraying uses nickel-chromium alloy powder as the base material and sprays it on the roller surface to form a base layer coating of a certain thickness. The top layer spraying uses metal ceramic as the top layer material and sprays it on the base layer coating to form a top layer coating of a certain thickness on the surface of the base layer coating. (3) Post-treatment: After the spraying is completed, the roller surface is tempered to eliminate the internal stress of the coating, and the roller surface is polished.

[0014] In this embodiment, the anti-nodulation treatment process specifically includes the following steps: Pre-treatment: First, the surfaces of the tension roll and steering roll are coarsely ground with a 200-grit grinding wheel to remove the original oxide scale, rust, and old coatings. Then, a combined cleaning process of high-pressure water jet cleaning and ultrasonic cleaning is used to thoroughly clean the roll surfaces. The high-pressure water jet cleaning pressure is set at 15MPa-20MPa, with the water flow angle at 45° to the roll surface, to remove the strip oxide scale, rolling oil residue, and impurity particles adhering to the roll surface. Next, the tension roll is placed in an ultrasonic cleaning tank at a temperature of 50-60℃ and an ultrasonic frequency of 40kHz for 20-30 minutes to further remove stubborn stains from the micropores of the roll surface. After cleaning, the roll surface is dried using hot air drying equipment at a temperature of 80℃-100℃ for 30 minutes. Finally, the roll surface is activated using a plasma treatment device for 10-15 minutes to enhance the adhesion of subsequent coatings. (2) Roller surface coating: First, nickel-chromium alloy powder (Ni60Cr15) is selected as the base material. After cleaning and drying, the roller surface is coated with supersonic flame spraying technology. The spraying distance is 180-220mm and the spraying temperature is 800-900℃. A base coating with a thickness of 15-20μm is formed on the roller surface to improve the high temperature resistance and corrosion resistance of the roller surface. Then, the explosion spraying (D-GUN) process is selected to prepare a ceramic composite wear-resistant and anti-stick coating as the top layer material. The coating material is DPC-74 (cermet). The spraying distance is maintained at 120mm-150mm and the coating thickness is precisely controlled at 40μm-70μm to ensure that the roller surface coating is uniformly covered and there are no missed areas. (3) Post-treatment: After the coating is prepared, the roller surface is subjected to low-temperature tempering treatment at 150-200℃ for 2 hours to eliminate internal stress in the coating. Then, the roller surface is polished using a precision grinding machine. Diamond polishing paste is used during the polishing process, with particle sizes of W20, W10, and W5 in sequence to gradually reduce the surface roughness of the roller. Finally, the surface roughness of the roller is controlled within the range of Ra4μm-Ra6μm, as shown in the attached figure. Figure 1 , 2 As shown; after grinding, the roller surface is subjected to non-destructive testing using penetrant testing method. The testing standard complies with the relevant specifications of GB / T 18851.1 metallurgical industry. The spraying pressure is 0.2MPa-0.3MPa, and the developing time is 10min-15min to ensure that the coating is free of defects such as cracks, pinholes, and peeling. After passing the test, a layer of anti-rust oil is evenly applied to the roller surface for post-treatment. (4) Installation and trial operation: Use an eddy current flaw detector to test the bonding strength of the coating, which is required to be ≥50MPa; then use a roughness tester to test the surface roughness of the roller to ensure that it meets the process requirements; hoist the tension roller and steering roller that meet the process requirements to the designated work position of the continuous annealing production line, and complete the bearing assembly, clearance adjustment and positioning fixation according to the equipment installation specifications; then start the production line for trial operation, and arrange a dedicated person to record the surface quality problems related to nodules, such as pitting and scratches on the strip steel surface every 3 days; compare and summarize the surface quality problems related to nodules on the strip steel surface every week during production, and further optimize the parameters; after the trial operation, manufacture the tension roller and steering roller surface according to the above optimized parameters and put them into normal production.

[0015] This invention has been verified through practical application and has the following significant effects: (1) Optimize the quality of the roll surface to ensure the quality of the strip steel. It can significantly improve the surface smoothness of tension rolls and guide rolls, reduce surface roughness, curb the problem of nodule formation on the roll surface from the source, effectively avoid quality defects such as scratches on the strip surface caused by nodule formation, and effectively improve the surface precision and product qualification rate of finished strip steel. (2) Ensure production line operation and reduce downtime losses. It can effectively block the trend of downtime accidents caused by nodule formation on the tension roll surface, significantly reduce the number of unplanned downtimes, maintain the stable operation of the heating furnace, reduce the impact on the continuity of the continuous annealing production line, and improve the overall operating efficiency of the production line. (3) Extend equipment life and reduce operation and maintenance costs It significantly reduces the number of times tension rollers need to be replaced, avoids damage to the furnace wall appearance and structure caused by repeated disassembly and assembly of the rollers, extends the service life of the equipment, and reduces operation, maintenance and spare parts costs.

[0016] (4) After the process of the present invention is adopted, the surface finish of the roller is significantly improved. Under the same working conditions, the amount of nodules per unit area is reduced by more than 70%, the strip scratch defect rate is reduced by 65%, the number of unplanned shutdowns is halved, and the replacement cycle of the guide roller is extended from half a year to one year, which greatly saves equipment operation and maintenance costs.

Claims

1. A process for anti-nodulation treatment of the surface of tension rollers and guide rollers in a continuous annealing furnace, characterized in that... The steps include the following: (1) Pretreatment: Clean the surface of the tensioning roller and the steering roller to remove the iron oxide scale, oil stains and impurity particles attached to the surface, and dry the roller surface; (2) Roller surface coating: includes base layer spraying and top layer spraying. The base layer spraying uses nickel-chromium alloy powder as the base material and sprays it on the roller surface to form a base layer coating of a certain thickness. The top layer spraying uses metal ceramic as the top layer material and sprays it on the base layer coating to form a top layer coating of a certain thickness on the surface of the base layer coating. (3) Post-treatment: After the spraying is completed, the roller surface is tempered to eliminate the internal stress of the coating, and the roller surface is polished.

2. The anti-nodulation treatment process for the surface of tension rollers and guide rollers in a continuous annealing furnace according to claim 1, characterized in that: In step (2), the base coat uses Ni60Cr15 nickel-chromium alloy powder as the base material, and its coating thickness is 15-20μm; the top coat uses DPC-74 cermet as the top material, and its coating thickness is 40-70μm.

3. The anti-nodulation treatment process for the surface of tension rollers and guide rollers in a continuous annealing furnace according to claim 2, characterized in that: In step (2), the bottom layer is sprayed using a supersonic flame spraying process with a spraying distance of 180-220mm and a spraying temperature of 800-900℃; the top layer is sprayed using an explosive spraying process with a spraying distance of 100-120mm and a spraying temperature of 1200-1400℃.

4. The anti-nodulation treatment process for the surface of tension rollers and guide rollers in a continuous annealing furnace according to claim 1, characterized in that: In step (3), the roller surface is subjected to low-temperature tempering treatment at a temperature of 150-200℃ and a holding time of 1.5-2.5h. The roughness of the roller surface after polishing and grinding is Ra4-Ra6μm.

5. The anti-nodulation treatment process for the surface of tension rollers and guide rollers in a continuous annealing furnace according to claim 1, characterized in that: The preprocessing in step (1) is specifically performed as follows: a. Mechanical grinding: The surface of the tension roller is rough ground with a grinding wheel to remove the original oxide scale, rust and old coating on the roller surface; b. Cleaning and degreasing: Clean the roller surface for 20-30 minutes at a temperature of 50-60℃ and an ultrasonic frequency of 40kHz using an alkaline degreasing agent to remove oil and impurities. c. Drying and activation: Drying is carried out in a hot air drying oven at a temperature of 80-100℃, followed by activation treatment of the roller surface for 10-15 minutes.

Images