A method for storing bearing parts after heat treatment

Abstract

This invention belongs to the field of bearing processing heat treatment and storage technology, specifically disclosing a method for storing bearing parts after heat treatment, including the following steps: S1, the bearing parts complete the heat treatment process on a roller bottom salt bath quenching production line, including cleaning, quenching, air cooling, residual salt cleaning, sodium nitrite basic rust prevention, and tempering; S2, after tempering, the bearing parts are transferred to storage cages and arranged in layers, with plastic mesh laid between each layer of bearing parts for isolation. After arrangement, they are sent to the inspection area, and after passing inspection, they are transferred to the qualified product storage area; S3, the qualified product storage cages are arranged according to the season; S4, differentiated rust prevention treatment is carried out according to the planned next processing interval of the parts. This invention adopts the above-mentioned method for storing bearing parts after heat treatment, and through layer isolation, seasonal placement and ventilation, and periodic differentiated rust prevention, it achieves simple rust prevention for short-term storage and long-term oil-sealed storage, reducing the rust scrap rate and saving chemical and labor costs.

Description

Technical Field

[0001] This invention relates to the field of bearing processing, heat treatment, and storage technology, and in particular to a method for storing bearing parts after heat treatment. Background Technology

[0002] High-carbon chromium bearing steel bearing parts include the outer ring, inner ring, and rolling elements. They are generally heat-treated using a roller bottom salt bath quenching production line. The complete process includes feeding, pre-cleaning, drying, heating, salt bath quenching, air cooling, residual salt cleaning, short-term rust prevention with sodium nitrite aqueous solution, and tempering. After tempering, the parts are sent to the inspection area. After passing hardness and metallographic physicochemical tests, they are transferred to the qualified product warehouse to await the next grinding process.

[0003] Existing storage technologies have the following core shortcomings: 1. Short-term rust prevention has a short duration, leading to frequent rework: Traditional rust prevention methods involve soaking and drying in a 4%~6% sodium nitrite aqueous solution. In dry seasons with workshop humidity <60%RH, rust prevention lasts only 7~10 days; in high-temperature and high-humidity environments with temperature >28℃ and humidity >60%RH, rust prevention lasts only 3~5 days. Due to misalignment of upstream and downstream processes and temporary changes in production plans, parts are very prone to exceeding the rust prevention period, requiring repeated transfer, spraying, and re-rust prevention, resulting in high consumption of manpower and chemicals.

[0004] 2. Corrosion defects at the stacked contact surface: In traditional storage cages, parts are stacked directly with their surfaces completely touching. When rust inhibitor is sprayed, it cannot penetrate into the gaps between the parts, causing moisture and residual salt to accumulate in the gaps. This results in large areas of rust on non-machined surfaces, leading to the product being deemed scrap.

[0005] 3. Poor ventilation in high temperature and humidity environments: Traditional storage cages are placed close together without ventilation gaps, preventing the circulation of humid air and causing continuous condensation on the surface of parts, which greatly increases the risk of corrosion.

[0006] 3. High disposal costs for long-term stockpiled products: If parts need to be stored for tens of days or even months, they can only be sprayed with rust prevention every 3 to 5 days. Sodium nitrite agent is continuously consumed, and the time spent on transportation and spraying is repeatedly wasted. The treatment of waste sodium nitrite wastewater increases environmental protection costs.

[0007] Therefore, the lack of a complete storage solution that varies by time period, season, and environment makes it impossible to simultaneously solve the technical problems of impact, rust in cracks, condensation in high humidity, and repeated rust prevention during long-term storage. Summary of the Invention

[0008] The purpose of this invention is to provide a method for storing bearing parts after heat treatment. This method addresses the problems of easy corrosion, frequent rust prevention, damage from impacts, severe condensation in high-humidity environments, and high long-term storage costs associated with existing salt bath heat-treated bearing parts storage. By implementing layered isolation, seasonal placement and ventilation, and differentiated rust prevention for different periods, this method achieves simple rust prevention for short-term storage and long-term oil-sealed storage, reducing the rust scrap rate and saving on reagent and labor costs.

[0009] To achieve the above objectives, the present invention provides a method for storing bearing parts after heat treatment, for the inner ring, outer ring, and rolling elements of high-carbon chromium bearing steel bearings, comprising the following steps: S1. Bearing parts undergo heat treatment in a roller-bottom salt bath quenching production line: 1) Loading: Bearing parts (including bearing inner / outer rings and rolling elements) are placed in layers in a special heat treatment fixture; 2) Pre-cleaning dual station: Clean with 1%~5% water-based cleaning agent solution for 5~10 minutes, then rinse with distilled water for 5~10 minutes; 3) Drying: Dry with hot air at 110~130℃ for 5~10 minutes to thoroughly remove surface water stains; 4) Heating: Hold at 835~865℃ for 40~80 minutes; 5) Salt bath quenching: Cool in a salt bath at 170~190℃ for 5~8 minutes, then rinse with salt for 1~2 minutes; 6) Forced air cooling, the surface temperature of the parts exiting the air-cooled zone is ≤50℃; 7) Three-stage residual salt cleaning: 28~32KHz ultrasonic cleaning at 60~80℃ for 5~10 minutes, followed by compressed air foam cleaning for 5~10 minutes, and then soaking in cold water at 8~10℃ for 5~10 minutes to completely remove solidified residual salt; 8) Basic rust prevention: Immerse in 4%~6% sodium nitrite aqueous solution for 5~10 minutes, then dry at 120~140℃ for 5~10 minutes; 9) Tempering: Hold in an air tempering furnace at 160~190℃ for 210~270 minutes; S2. After tempering, the bearing parts are transferred to storage cages and arranged in layers with plastic mesh between each layer. After arrangement, they are sent to the inspection area for microstructure and hardness testing. If they meet the GB / T34891-2017 standard, they are transferred to the qualified product storage area. The storage cage measures 1200×1000×890mm, with plastic mesh laid between each layer of bearing parts for isolation; The plastic flat mesh is made of PE or PP, with a mesh size of 12~25mm and a thickness of 2.5~5mm. Its length and width match the bottom surface of the storage cage. Laying rules: Lay a layer of plastic mesh at the bottom of the cage, lay a single layer of bearing parts, and then lay another layer of plastic mesh in a circular stacking manner, with complete isolation between layers to avoid flat contact between the bearing parts; S3. Seasonal Storage Cages for Qualified Products: Rules for Seasonal Storage Cage Placement for Qualified Products: 1) Dry season determination: Workshop humidity < 60%RH, storage cages are placed densely and closely together without reserved gaps to maximize the use of storage area; basic sodium nitrite rust prevention is effective for 7~10 days; 2) High temperature and high humidity season criteria: Outdoor maximum temperature > 28℃, ambient humidity > 60%RH, qualified product storage area is designated as an independent storage area with a length and width of 10~15m × 10~15m, with a 0.5~0.8m ventilation gap reserved between rows of storage cages; multiple floor-standing high-power axial flow fans are arranged along the side of the area along the cage rows to continuously force air circulation and reduce condensation on the surface of parts; the basic sodium nitrite rust prevention is only effective for 3~5 days; S4. Differentiated rust prevention treatment is carried out according to the planned next processing interval of the parts. That is, according to the planned next processing interval of the parts, it is divided into two modes: short-term water-based rust prevention storage and medium-to-long-term oil-sealed long-term rust prevention storage. Mode 1: Short-term rehydration and rust prevention storage, i.e., processing is possible within 14-20 days in the dry season and within 6-10 days in the high humidity season; For parts that have exceeded their expiration date, a secondary water immersion method for rust prevention is used, as detailed below: The rust inhibitor is a 4%~6% sodium nitrite aqueous solution. Soak for 5~8 minutes, drain for 5~8 minutes, update the rust prevention storage label, and put it back in the original area. No drying is required.

[0010] Mode 2: Medium- to long-term oil-sealed long-term rust prevention storage, i.e., more than 20 days in dry seasons and more than 10 days in high-humidity seasons, followed by processing after several months; For parts that have exceeded their expiration date, long-term storage using oil seals is employed, as detailed below: a) The rust-preventive oil used is qualified bearing rust-preventive oil that is not currently in use in the workshop. The inspection indicators upon warehousing are: trace moisture < 800 ppm, kinematic viscosity at 40℃ > 10 mm³. 2 / s; b) Immerse the entire storage cage in the oil tank for 5-8 minutes, then remove it and let it drip oil naturally for 5-8 minutes; c) Wrap the entire cage completely with transparent plastic film and place it on a 304 stainless steel tray to prevent oil seepage and contamination of the ground; d) Affix an oil seal storage label; the rust prevention effect lasts for up to 1 year. e) Oil removal process before processing oil seal bearing parts: Before the bearing parts are transferred for grinding, they are degreased using a bearing cleaning machine: the cleaning solution is a 6%~8% water-based cleaning agent aqueous solution, heated to 60~80℃ for cleaning, and the surface anti-rust oil is completely removed before being handed over to the next process.

[0011] S5. Complete storage and grind bearing parts.

[0012] Working principle of this invention: PP / PE plastic mesh is used for interlayer isolation: it isolates the contact surfaces of parts, allowing rust inhibitor to penetrate all metal surfaces; ventilation gaps are reserved between layers to prevent moisture from accumulating on the contact surfaces, and at the same time, it avoids collisions and scratches on parts during transportation and stacking.

[0013] Forced ventilation via high humidity fans: The storage cages have reserved ventilation gaps, which, combined with axial flow fans, continuously exchange air, reducing local relative humidity, eliminating conditions for condensation, and significantly slowing down the rate of corrosion.

[0014] The system employs a dual-mode, graded rust prevention approach: for short-term storage, it only requires low-cost re-immersion in sodium nitrite solution, eliminating the need for frequent spraying and transportation; for medium- and long-term storage, it utilizes idle waste bearing oil seals, turning waste into treasure, with a single oil seal providing protection for one year, completely eliminating the need for multiple rust prevention processes and the consumption of labor and chemicals.

[0015] By wrapping the product with a stainless steel pallet and plastic film, the oil seal isolates moisture and dust from the air, while the pallet catches dripping anti-rust oil, preventing oil pollution on the workshop floor and reducing environmental treatment costs.

[0016] Therefore, the present invention employs the above-mentioned method for storing bearing parts after heat treatment, which has the following beneficial effects: Reduce parts corrosion and scrap: interlayer isolation eliminates corrosion in the joints, high humidity ventilation reduces condensation, and parts scrap rate is reduced by more than 90%; Reduce labor and chemical consumption: For medium- to long-term products, a single oil seal replaces the need for re-rust prevention every 3 to 10 days, reducing the amount of sodium nitrite chemical used by 70%; idle rust-preventive oil can be reused to reduce oil procurement costs. Plastic flat mesh protection: The plastic flat mesh also prevents the surface of the precision bearing from being bumped after heat treatment, reducing appearance defects; Rational use of storage space: dense stacking during the dry season increases storage capacity, and ventilation layout inhibits rust during the high humidity season, balancing storage efficiency and protective effect; Environmental protection: Reduces the frequent generation of sodium nitrite waste liquid, centrally recycles oil seal waste liquid, and significantly reduces the wastewater treatment load.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an embodiment of a method for storing bearing parts after heat treatment according to the present invention; Figure 2 This is a schematic diagram of a plastic flat mesh according to an embodiment of a method for storing bearing parts after heat treatment according to the present invention.

[0019] Figure Labels 1. Qualified product storage area; 2. Storage cages; 3. Axial flow fan. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0022] Example 1 like Figure 1 As shown, a method for storing bearing parts after heat treatment, specifically high-temperature and high-humidity long-term oil-sealed storage, is described. The processed part is the outer ring of an NN3030K / W33 high-carbon chromium bearing, and the method includes the following steps: Heat treatment process: 750 salt bath line at the bottom of the roller, heating to 845℃ and holding for 52 minutes, quenching in a salt bath at 180℃ for 6 minutes, cleaning with three-stage residual salt, soaking in 6% sodium nitrite for 6 minutes, and tempering at 180℃ for 240 minutes. Packing: Two 1200×1000×890mm storage cages, such as... Figure 2 As shown, a layer of 5mm thick PP flat mesh (25mm mesh size, 1200×1000mm) is laid at the bottom of the storage cage. Then, a layer of NN3030K / W33 outer rings is placed on the flat mesh, with 20 pieces placed on the mesh. Following this method, with one layer of plastic flat mesh and one layer of bearing parts, 12 layers are placed in one storage cage, for a total of 240 bearing outer rings, which are stored in the testing area. Testing: Metallographic grade 3, hardness 61.5HRC, meets the requirements of GB / T34891-2017 "Technical Conditions for Heat Treatment of High Carbon Chromium Bearing Steel Parts for Rolling Bearings" standard, and is transferred to qualified product storage area 1 after meeting the standards; Storage Environment: Mid-to-late July, summer, outdoor temperature 32℃, humidity 85%RH, outdoor wind force less than level 2, typical high humidity mode; storage cages 2 with 0.5m gaps, 5 axial flow fans 3 arranged in the area; basic rust prevention effective period 3 days; the storage cages containing bearing parts are placed in the qualified product area as follows: the qualified product area is defined as 11m long and 10m wide. A 0.5m gap is left between the storage cages. The qualified product area can hold 42 storage cages (6 in the length direction × 7 in the width direction). A floor-standing high-power axial flow fan is placed at one boundary along the length direction of the qualified product area, in the gap between two rows of storage cages, for a total of 5 axial flow fans. The fans are activated to accelerate air circulation around the storage cages.

[0023] Production plan: Grinding process in 3 months, followed by oil-sealed storage. Using Wuxi Luoshen Pinbao 50 unused rust-preventive oil, the moisture content was tested at 420 ppm and the viscosity at 16 mm.2 / s; Soak the whole cage for 6 minutes, drizzle with oil for 8 minutes, wrap with plastic film and place on a stainless steel tray, mark the oil seal date, and it can be stored for 12 months without rust; Degreasing before processing: Clean with 6% H315 cleaning agent at 80℃ for 10 minutes. After cleaning, send to grinding.

[0024] Example 2 A method for storing bearing parts after heat treatment, specifically a short-term secondary water-based rust-preventive storage during the dry season, for the machined part: the outer ring of a 6318 high-carbon chromium bearing, includes the following steps: Heat treatment process: heating at 850℃ for 55 minutes, quenching at 180℃ for 7 minutes, soaking in 6% sodium nitrite for 7 minutes, tempering at 180℃ for 240 minutes; Packing: 2 storage cages with dimensions of 1200×1000×890mm, 2.5mm thick PP flat mesh (12mm mesh size, 1200×1000mm). Lay a layer of plastic flat mesh at the bottom of the storage cage, and place a layer of 6318 outer rings on the flat mesh, with a quantity of 30 pieces. Following this method, with a layer of plastic flat mesh and a layer of bearing parts, 16 layers are placed in one storage cage, for a total of 480 pieces of 6318 outer rings, which are then stored in the inspection area. Testing: Metallographic grade 2, hardness 60.5HRC, meets the requirements of GB / T34891-2017 "Technical Conditions for Heat Treatment of High Carbon Chromium Bearing Steel Parts for Rolling Bearings" standard, and is transferred to qualified product storage area 1 after meeting the standards; Storage environment: Early November, winter, 45% RH dry mode, storage cages 2 are placed close together, basic rust prevention for 10 days; Production plan: Grinding after 15 days, secondary water rust prevention on the 9th day: soaking in 4% sodium nitrite solution for 5 minutes, draining for 5 minutes, updating labels and storing normally until sent for grinding, with no rust throughout the process.

[0025] Comparative Example 1 A method for storing bearing parts after heat treatment, specifically a traditional storage method, uses the same model NN3030K / W33 outer ring for the machined parts. The heat treatment process and storage environment parameters are completely consistent with those in Example 1. The difference in storage method (tray loading) compared to Example 1 is as follows: Storage cage 2 has no plastic mesh; parts are directly stacked and attached. The high-humidity qualified product area storage cages 2 are densely packed together, with no ventilation gaps and no axial flow fan 3; The production plan is to perform grinding after 2 months, using only 15% sodium nitrite spray for rust prevention, and spraying once every 3 days.

[0026] Effect comparison: After 20 days of storage, a large number of bonding surfaces showed corrosion. It was necessary to arrange two dedicated personnel to transfer and spray twice a month. The consumption of sodium nitrite was three times that of Example 1, the labor hours increased by 200%, and the corrosion scrap rate exceeded 15%.

[0027] Therefore, this invention employs the aforementioned method for storing bearing parts after heat treatment, employing differentiated storage cage placement and ventilation schemes for dry and high-temperature / high-humidity environments. During high-humidity seasons, ventilation gaps are reserved, and axial flow fans are used to reduce condensation and corrosion. Based on the next processing cycle, two modes are implemented: short-term sodium nitrite rehydration for rust prevention and medium-to-long-term storage of idle bearing oil seals. Short-term storage allows for low-cost re-immersion, while medium-to-long-term oil sealing provides one year of rust prevention, eliminating the need for frequent transfer and spraying processes. This method solves the problems of high rust scrap rates, high consumption of manual reagents, easy condensation in high-humidity environments, and repeated rust prevention during long-term storage. It combines the advantages of high storage utilization, part protection, and environmental cost reduction, and is suitable for batch storage management of inner and outer rings and rolling elements of high-carbon chromium bearings after heat treatment using roller-bottom salt bath quenching.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for storing bearing parts after heat treatment, characterized in that, Includes the following steps: S1. Bearing parts undergo heat treatment processes in a roller bottom salt bath quenching production line, including cleaning, quenching, air cooling, residual salt cleaning, sodium nitrite-based rust prevention, and tempering. S2. After tempering, the bearing parts are transferred to the storage cage and placed in layers. A plastic mesh is laid between each layer of bearing parts for isolation. After placement, they are sent to the inspection area to complete the microstructure and hardness physicochemical tests. After passing the tests, they are transferred to the qualified product storage area. S3. Qualified products should be stored in storage cages according to the season. S4. Differentiated rust prevention treatments are carried out according to the planned next processing interval of the parts, including short-term water-based rust prevention storage and medium-to-long-term oil-sealed long-term rust prevention storage. S5. Complete storage and grind bearing parts.

2. The method for storing bearing parts after heat treatment according to claim 1, characterized in that, In S2, the plastic flat mesh is made of PE or PP material, with a mesh size of 12~25mm, a thickness of 2.5~5mm, and its length and width match the bottom surface of the storage cage.

3. The method for storing bearing parts after heat treatment according to claim 1, characterized in that, S3 specifically refers to: During the dry season, when the ambient humidity is less than 60%RH, storage cages should be placed close together. During the hot and humid season, when the outdoor maximum temperature is >28℃ and the ambient humidity is >60%RH, a ventilation gap of 0.5~0.8m should be reserved between the rows of storage cages. The qualified product storage area should be designated as an independent storage area with a length and width of 10~15m×10~15m. Forced ventilation should be provided by floor-mounted axial flow fans on the side of the qualified product storage area.

4. A method for storing bearing parts after heat treatment according to claim 1, characterized in that, In S4, the specific short-term rehydration and rust prevention storage is as follows: Processing time is 14-20 days during the dry season and 6-10 days during the high humidity season. After the parts have exceeded their expiration date, soak them in a 4%-6% sodium nitrite aqueous solution for 5-8 minutes and then drain for 5-8 minutes.

5. A method for storing bearing parts after heat treatment according to claim 1, characterized in that, In S4, the long-term rust prevention storage of oil seals specifically refers to: Processing time is more than 20 days in dry season and more than 10 days in high humidity season. After the parts have exceeded their expiration date, use bearing anti-rust oil to soak and seal them for 5-8 minutes, then spray oil for 5-8 minutes. Wrap the whole cage in plastic film and place it on a stainless steel tray for sealed storage.

6. A method for storing bearing parts after heat treatment according to claim 5, characterized in that, The inspection criteria for bearings after soaking the oil seal in anti-rust oil before warehousing are as follows: Moisture content < 800 ppm, kinematic viscosity at 40°C > 10 mm³ 2 / s.

7. A method for storing bearing parts after heat treatment according to claim 5, characterized in that, Before step S5, there is also a pre-processing degreasing procedure for the oil seal parts, specifically: Use a 60~80℃, 6%~8% water-based cleaning agent solution to clean bearing parts that have been stored for long-term oil seal and long-term rust prevention.

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