On-line repairing process for hardened tooth surface gear

Abstract

The invention relates to the technical field of metal welding repair, and discloses a hard tooth surface gear online repair process which comprises the following steps: S1, surface purification; s2, defects are removed, crack arrest holes are drilled, and after preheating, the defects are removed to form repairing grooves; s3, on-line heating and welding are conducted, specifically, the repaired groove area is heated and is welded through a movable cold metal transition welding machine after being cooled to a certain temperature, slag removal treatment is conducted after each welding seam is welded, and a welding bead is hammered; s4, hydrogen removal after welding is conducted, the defect area of the gear is covered or wrapped with heat preservation cotton, and the temperature is monitored; and S5, surface finishing is conducted, specifically, profiling grinding and profiling polishing are conducted on the weld joint in a profiling grinding mode and a profiling polishing mode. The invention provides a set of complete hard tooth surface gear online repairing process technology which has high reliability and high efficiency, and the service life of a gear product can be greatly prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of metal welding repair, and more specifically to an online repair process for hardened gear surfaces. Background Art

[0002] Hardened gears have the characteristics of high load-bearing capacity, high wear resistance, high reliability, and high hardness, so they can meet the requirements of high load, high efficiency, and long life in the heavy-duty field. With the continuous and rapid development of my country's high-end equipment manufacturing industry, hardened gears play a vital role in industries such as metallurgy and petrochemicals, engineering machinery, aerospace, and rail transportation. Hardened gears are prone to failure after long-term use. The most common forms of failure are surface pitting and bonding damage. Gear failure will seriously affect the accuracy and transmission efficiency of the transmission system, and thus affect equipment operation, production safety, and economic benefits.

[0003] At this stage, my country has formulated a path of circular economy and green development, and listed green remanufacturing technology as one of the common and key technologies to support the circular economy. At present, my country is still in its infancy in terms of gear repair and remanufacturing technology. Not only does it lack systematic and complete research, but it also needs to make breakthroughs in many key technologies. Most of the existing research on gear repair technology is limited to the repair and remanufacturing of soft gear tooth surfaces, and lacks the necessary evaluation system and industry norms. Applying high-quality, efficient and economical surface treatment technology to the field of high-end equipment repair and remanufacturing, improving the service life of high-end equipment, and improving the performance of core components after repair is of great significance to the improvement of my country's high-end equipment scientific research level and the training and reserve of talents in the high-end equipment manufacturing industry.

[0004] In order to improve the load-bearing capacity and wear resistance, hardened gears are usually made of low-carbon steel, and the surface is treated by carburizing and quenching to improve the hardness and wear resistance. After carburizing, the surface carbon content reaches 0.7% to 1.05%, and the surface hardness can reach 58 to 62HRC. The excessively high carbon equivalent makes repair and remanufacturing very technically difficult, and cold cracks are easily generated during the welding process. In addition, welding hot cracks and reheating cracks are highly sensitive. At the same time, there are problems such as low efficiency and high dependence on manual labor. In addition, for the surface defects of extra-large gear racks such as large ship lifts and offshore platforms, due to the particularity of the working environment, online repair is required, and the process methods in the existing technology are difficult to achieve online repair. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies in the prior art, the present invention provides an online repair process for hardened gears. The present invention achieves the above-mentioned purpose through the following technical solutions.

[0006] An online repair process for hardened gears comprises the following steps: S1, surface cleaning, protecting the gear surface outside the defective area on the gear and removing pollutants in the defective area; S2, defect removal, drilling crack-stop holes at both ends of the defect area on the gear, preheating the defect area at a temperature of 150°C, and using a combination of carbon arc gouging and grinding to remove the defect and form a repair groove; S3, online heating welding, use far infrared or oxyacetylene to heat the repair groove area on the gear to 220℃, and weld when the temperature of the repair groove area cools to 200±10℃. The heating and cooling speed is less than or equal to 50℃ / h. A mobile cold metal transfer welding machine is used for welding. After each weld is completed, a grinding and cleaning tool is used to remove slag and hammer the weld between the first and last layers. After cleaning the welding slag, use a 5-10 times magnifying glass to check whether there are defects in the weld. If there are defects in the weld, stop welding, and then use carbon arc gouging to remove the defects, and use non-destructive testing methods to confirm until the defects are completely removed before re-welding. If there are no defects in the weld, the next weld can be welded, and finally the repair groove is filled and the weld height exceeds the gear surface by more than 1mm; S4, dehydrogenate after welding, cover or wrap the defective area of ​​the gear with insulation cotton and monitor the temperature, use interval heating method to keep the temperature of the defective area at 200±15℃, and the insulation time is at least 2 hours; S5, surface finishing, uses profile grinding and profile polishing to profile grind and profile polish the weld. During grinding and polishing, the grinding wheel and the polishing wheel move back and forth along the tooth width direction of the gear.

[0007] This solution drills crack-stop holes at both ends of the defective area and preheats the defective area before carbon arc gouging, which can prevent defects such as cracks from occurring during the carbon arc gouging process. Even if new cracks are accidentally generated, the cracks will not extend outward due to the presence of the crack-stop holes. The welding adopts a mobile cold metal transition welding machine, which can also be called a portable cold metal transition welding machine. The mobile cold metal transition welding machine adopts cold metal transition welding technology, which is a welding technology without slag splash. During welding, the welding power supply can accurately control the current and voltage so that the retraction movement of the welding wire is synchronized with the molten droplet transition, thereby reducing heat input. It has the characteristics of precise control of the molten droplet transition process, high welding quality, and beautiful weld formation. Welding uses welding wire and welding materials corresponding to the gear surface material. After welding a weld, slag cleaning and hammering must be carried out to cause plastic deformation of the weld to release stress.

[0008] The operations of carbon arc gouging, drilling, far infrared or oxyacetylene heating, welding and hammering in this scheme can all be performed with portable or mobile equipment or tools, so online repair can be achieved. In addition, special process steps or methods are formulated for hardened gears, such as drilling crack-stop holes, removing defects after preheating, heating and cooling before welding, hammering the weld after each weld, weld inspection and repair, online dehydrogenation after welding, etc., so as to ensure that the mechanical properties of the welded filling part are similar to those of the gear, and the welded filling part is metallurgically bonded to the gear without cracks. The weld is profiled and polished to make the repaired gear surface shape, size, roughness and original gear surface shape, size, roughness consistent to meet the use requirements. This scheme proposes a complete set of online repair process technologies for hardened gears, which are highly reliable and efficient and can greatly extend the service life of gear products.

[0009] As a further optimization, the above step S1 includes step S1a after that, detecting internal defects, using non-destructive testing methods to detect the defective area, and marking the internal defect position. Some defects are exposed on the gear surface and can be directly observed with the naked eye, and some defects are located inside the gear and need to be located by a detection method before proceeding to the next step to completely remove all defects.

[0010] As a further optimization, the above-mentioned step S2 includes step S2a after step S2, defect re-detection, using a non-destructive testing method to detect the groove area to confirm whether the defect is completely removed. If the defect still exists, the defect is removed again by combining carbon arc gouging and grinding, and the detection is repeated until the defect is completely removed.

[0011] As a further optimization, in the above step S3, windproof measures are taken for the welding site before welding. Welding in a place where the air flows too fast will seriously affect the welding quality, etc. The online repair cannot select the welding location, so if the air flows too fast at the welding location, windproof measures need to be taken for the welding site, such as setting up windshields around the welding site or defect area, etc., to ensure the welding quality.

[0012] Compared with the prior art, the present invention mainly has the following beneficial effects: operations such as carbon arc gouging, drilling, far infrared or oxyacetylene heating, welding and hammering can all be performed using portable or mobile equipment or tools, so online repair can be achieved. Special process steps or methods are formulated for hardened gears, such as drilling crack-stop holes, removing defects after preheating, heating and cooling before welding, hammering the weld after each weld, weld inspection and repair, online dehydrogenation after welding, etc., so as to ensure that the mechanical properties of the welded filling part are similar to those of the gear, and the welded filling part is metallurgically bonded to the gear without cracks. The weld is profiled and polished to make the repaired gear surface shape, size, and roughness consistent with the original gear surface shape, size, and roughness to meet the use requirements. The present invention proposes a complete set of online repair process technologies for hardened gears, which has high reliability and efficiency and can greatly extend the service life of gear products. Implementation

[0013] The present invention is further described below. This is only for illustrative purposes and should not be construed as limiting this patent. In order to more concisely describe this embodiment, some parts that are well known to those skilled in the art but not related to the main content of the present invention will be omitted in the description. In addition, for ease of description, some parts will be omitted, enlarged or reduced, but they do not represent the size or entire structure of the actual product.

[0014] Embodiment, this embodiment takes a large modulus gear in a certain offshore platform as an example to introduce an online repair process for a hardened gear. The gear is made of low-carbon steel, and the surface is carburized and quenched to improve hardness and wear resistance, so the surface carbon equivalent is relatively high. The modulus of the gear is large, that is, the volume and mass of the gear are large, which is not easy to disassemble and can only be repaired online. The specific steps of this embodiment are as follows: S1, surface cleaning. Protect the gear surface outside the defective area on the gear and remove pollutants in the defective area, such as dust, oil, oxide layer, etc., which can be removed by manual, solvent, ultrasonic and other methods. In order to prevent damage, destruction and corrosion to the gear surface outside the defective area, that is, the non-repaired surface, protective measures should be taken to protect the gear surface outside the defective area. In addition, it is also necessary to prevent hard particles and corrosive media from entering the defect during cleaning.

[0015] S1a, detect internal defects. Use non-destructive testing methods to detect the defective area and mark the internal defect location. Because online repair is to be achieved, it is necessary to use online non-destructive testing methods to determine the internal defect location, such as radiographic testing, magnetic particle testing, ultrasonic testing, liquid penetrant testing or eddy current testing, and then proceed to the next step to completely remove all defects.

[0016] S2, defect removal. Stop crack holes are drilled at both ends of the defect area on the gear, and the defect area is preheated at a preheating temperature of 150°C. A combination of carbon arc gouging and grinding is used to remove defects and form repair grooves. Stop crack holes are drilled at both ends of the defect area and the defect area is preheated before carbon arc gouging to prevent defects such as cracks from occurring during the carbon arc gouging process. Even if new cracks are accidentally generated, the cracks will not extend outward due to the presence of stop crack holes.

[0017] S2a, defect re-detection. Use non-destructive testing methods to detect the groove area to confirm whether the defects are completely removed. If defects still exist, use a combination of carbon arc gouging and grinding to remove the defects again, and repeat the inspection until the defects are completely removed. After the defects are completely removed, grind the sharp corners and edges of the groove area, and remove oil, grease, dirt and other debris that are not conducive to the quality of the weld in the groove area.

[0018] S3, online heating welding. Before welding, a windshield is set up around the welding site or defect area, that is, windproof measures are taken for the welding site. The repair groove area on the gear is heated to 220°C by far infrared or oxyacetylene, and welding is carried out when the temperature of the repair groove area cools to 200°C. The heating and cooling rates are less than or equal to 50°C / h. A mobile cold metal transition welding machine is used for welding. After each weld is completed, a grinding and cleaning tool is used to remove slag and hammer the weld between the first and last layers to cause plastic deformation of the weld to release stress. After cleaning the welding slag, use a 10x magnifying glass to check whether there are defects in the weld. If there are defects in the weld, stop welding, then use carbon arc gouging to remove the defects, and use non-destructive testing methods to confirm until the defects are completely removed before re-welding. During the cleaning process, pay attention to protecting the surrounding area from damage. If there are no defects in the weld, the next weld can be welded. Finally, the repair groove is filled and the weld height exceeds the gear surface by more than 1mm. The surface carbon equivalent of the gear targeted by this embodiment is relatively high, and the surface performance after welding repair should be close to the surface performance of the gear, so low-alloy high-strength steel welding wire and high-strength steel welding materials are used for welding in this embodiment.

[0019] S4, post-weld dehydrogenation. Use thickened thermal insulation cotton to cover or wrap the defective area of ​​the gear and monitor the temperature. Use interval heating method to keep the temperature of the defective area at 200±15℃ for at least 2 hours.

[0020] S5, surface finishing. The weld is profiled and polished by profile grinding and profile polishing. During grinding and polishing, the grinding wheel and the polishing wheel move back and forth along the tooth width direction of the gear.

[0021] In this embodiment, operations such as carbon arc gouging, drilling, far infrared or oxyacetylene heating, welding and hammering can all be performed using portable or mobile equipment or tools, so online repair can be achieved. In addition, special process steps or methods are formulated for hard-toothed gears, such as drilling crack-stop holes, removing defects after preheating, heating and cooling before welding, hammering the weld after each weld, inspecting and repairing the weld, and online dehydrogenation after welding, etc., so as to ensure that the mechanical properties of the welded filling part are similar to those of the gear, and that the welded filling part is metallurgically bonded to the gear without cracks. The weld is profiled and polished to make the repaired gear surface shape, size, and roughness consistent with the original gear surface shape, size, and roughness to meet the use requirements. This embodiment proposes a complete set of online repair process technologies for hard-toothed gears, which has high reliability and efficiency and can greatly extend the service life of gear products.

[0022] The above is only a specific embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using the design concept of the present invention fall within the protection scope of the present invention.

Claims

1. An online repair process for hardened gears, characterized in that: The steps include: S1, surface cleaning, protecting the gear surface outside the defective area on the gear and removing pollutants in the defective area; S2, defect removal, drilling crack-stop holes at both ends of the defect area on the gear, preheating the defect area at a temperature of 150°C, and using a combination of carbon arc gouging and grinding to remove the defect and form a repair groove; S3, online heating welding, use far infrared or oxyacetylene to heat the repair groove area on the gear to 220℃, and weld when the temperature of the repair groove area cools to 200±10℃. The heating and cooling speed is less than or equal to 50℃ / h. A mobile cold metal transfer welding machine is used for welding. After each weld is completed, a grinding and cleaning tool is used to remove slag and hammer the weld between the first and last layers. After cleaning the welding slag, use a 5-10 times magnifying glass to check whether there are defects in the weld. If there are defects in the weld, stop welding, and then use carbon arc gouging to remove the defects, and use non-destructive testing methods to confirm until the defects are completely removed before re-welding. If there are no defects in the weld, the next weld can be welded, and finally the repair groove is filled and the weld height exceeds the gear surface by more than 1mm; S4, dehydrogenate after welding, cover or wrap the defective area of ​​the gear with insulation cotton and monitor the temperature, use interval heating method to keep the temperature of the defective area at 200±15℃, and the insulation time is at least 2 hours; S5, surface finishing, uses profile grinding and profile polishing to profile grind and profile polish the weld. During grinding and polishing, the grinding wheel and the polishing wheel move back and forth along the tooth width direction of the gear.

2. The online repair process for hardened gears according to claim 1 is characterized in that: The step S1 includes a step S1a after the step S1, detecting internal defects, detecting the defective area by using a non-destructive testing method, and marking the internal defect position.

3. The online repair process for hardened gears according to claim 2 is characterized in that: The step S2 includes step S2a after step S2, which is defect re-detection. The groove area is detected by a non-destructive testing method to confirm whether the defect is completely removed. If the defect still exists, the defect is removed again by combining carbon arc gouging and grinding, and the detection is repeated until the defect is completely removed.

4. The online repair process for hardened gears according to claim 1 is characterized in that: In the step S3, before welding, wind protection measures are taken on the welding site.