Why should slewing bearings be annealed? Annealing purpose and process type

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Why should slewing bearings be annealed? In fact, slewing bearing slewing bearing annealing is a process of bearing heat treatment. Generally, the bearing metal is heated to a certain temperature and maintained for a period of time, and then the metal is cooled at a suitable speed. This method improves the toughness of bearing steel. , Reduce the bearing hardness and residual stress to reduce the probability of deformation and cracks, and enhance the stability of the bearing material.
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Why should slewing bearings be annealed?

Slewing Bearings​​
The purpose of slewing bearing annealing may be for three reasons:
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1. The annealing process can reduce the hardness of the bearing steel, improve the plasticity, and facilitate the later cutting and deformation processing.
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2. Annealing can refine the grains of the bearing material, eliminate the structural defects caused by the casting, forging and welding of the bearing, uniform the structure and composition of the steel, and improve the performance of the steel to prepare for the later heat treatment.
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3. The annealing process can eliminate the internal stress in the steel and prevent or reduce the possibility of deformation and cracking of the bearing. In one case, the annealing process is not only for the annealing of metallic materials but also for non-metallic materials. After understanding why slewing bearings should be annealed, the following editor will introduce the types of annealing processes for slewing bearings. In fact, there are many types of annealing processes, and the processes applicable to different steel structures are also different.

Type of annealing process for slewing bearing


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1. Recrystallization annealing

Recrystallization annealing, also called full annealing, is an annealing process in which the iron-carbon alloy is austenitized and then slowly cooled or stopped in a near-equilibrium state. The heating temperature of carbon steel is generally Ac3+ (30~50℃); alloy steel is Ac3+(500~70℃); the holding time depends on the type of steel, the size of the workpiece, the amount of furnace installed, the selected equipment model, etc. factors are determined. In order to ensure that the supercooled austenite undergoes pearlite transformation, the cooling of the recrystallization annealing must be slow, and the furnace is cooled to about 500 ℃ and air-cooled.

This annealing process is mainly used for hypoeutectoid steel, generally medium carbon steel and low and medium carbon alloy structural steel forgings, castings and hot-rolled profiles, and sometimes for their welded components; it is not suitable for hypereutectoid steel, Because the recrystallization annealing of hypereutectoid steel needs to be heated to above Acm, during slow cooling, cementite precipitates along the austenite grain boundaries and is distributed in a network, resulting in increased brittleness of the material, leaving hidden dangers for heat treatment.

2. Uniform annealing

Uniform annealing, also known as diffusion annealing, is to reduce the segregation of the chemical composition of the metal casting or forging billet and the inhomogeneity of the structure. It is heated to a high temperature, kept for a long time, and then slowly cooled to homogenize the chemical composition and structure. Purpose of the annealing process. The heating temperature of the homogenization annealing is generally Ac3+ (150-200 ℃), that is, 1050-1150 ℃, and the holding time is generally 10-15h, in order to ensure that the diffusion is fully carried out, and the purpose of eliminating or reducing the uneven composition or structure is large. Due to the high heating temperature, long time and coarse grains of diffusion annealing, recrystallization annealing or normalizing should be performed after diffusion annealing to re-refine the structure.

3. Incomplete annealing

Incomplete annealing is an annealing process in which the iron-carbon alloy is heated to a temperature between Ac1 and Ac3 to achieve incomplete austenitization, followed by slow cooling. Incomplete annealing is mainly suitable for medium and high carbon steel and low alloy steel forgings and rolling parts. Its purpose is to refine the structure and reduce the hardness.

4. Stress relief annealing

One of the key reasons why slewing bearings should be annealed is the annealing process to eliminate residual stress caused by plastic deformation processing, welding, etc. and existing in the casting. There is internal stress inside the workpiece after forging, casting, welding and cutting. If it is not eliminated in time, the workpiece will be deformed during processing and use, affecting the accuracy of the workpiece. It is very important to use stress relief annealing to eliminate the internal stress generated during processing.

5. Isothermal annealing

Isothermal annealing is to heat the steel or blank to a certain temperature and hold it for a period of time, then quickly cool it to a certain temperature in the pearlite temperature range and keep it isothermally, so that the austenite is transformed into a pearlite-type structure, and then in the air. Medium cooling annealing process.

This process is suitable for medium carbon alloy steel and low alloy steel, and its purpose is to refine the structure and reduce the hardness. The heating temperature of hypoeutectoid steel is Ac3+(30～50)℃, and the heating temperature of hypereutectoid steel is Ac3+(20～40)℃, keep it for a certain period of time, and carry out isothermal transformation with furnace cooling to slightly lower than Ar3 temperature, and then air-cooled. . The isothermal annealing structure and hardness are more uniform than the crystallization annealing.

6. Spheroidizing annealing

Spheroidizing annealing is an annealing process to spheroidize carbides in steel. It is heated to 20-30°C above Ac1, kept for a period of time, and then slowly cooled to obtain the structure of spherical or granular carbides uniformly distributed on the ferrite matrix.

Spheroidizing annealing is mainly used for hypereutectoid steel and alloy tool steel (such as cutting tools, measuring tools, molds and bearings, etc. all steel grades). Its purpose is mainly to reduce hardness, improve machinability, and prepare for subsequent quenching. There are many spheroidizing annealing process methods, and the two commonly used processes are ordinary spheroidizing annealing and isothermal spheroidizing annealing. Compared with ordinary annealing methods, spheroidizing annealing can not only shorten the cycle, but also make the spheroidized structure uniform, and can strictly control the hardness after annealing.

7. Recrystallization annealing

Recrystallization annealing is also called intermediate annealing. It is a heat treatment process in which the metal after cold deformation is heated to above the recrystallization temperature and maintained for an appropriate time to recrystallize the deformed grains into uniform equiaxed grains to eliminate deformation strengthening and residual stress.

The above is the introduction of the reasons why the slewing bearing needs to be annealed. It also includes the types of annealing processes and their respective characteristics and process introductions. I hope to help you have a clearer understanding of the annealing process. In addition, our company produces slewing bearings, slewing bearings, and slewing drives of various types and precisions. If you have any needs, please feel free to inquire.

Why should the slewing bearing be pickled? Pickling process

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In our production process, the process of cleaning and degreasing the metal parts and soaking them in an acid solution is usually called pickling. Bearings also need to be pickled, so why should slewing bearings be pickled?

There are two main purposes, one is to remove oxide scale or burrs on the metal surface by pickling, and the other is to pickling to check metal surface defects to see if there is burn corrosion. The editor of Lunda will introduce to you the specific operation process of slewing bearing pickling.

The purpose of pickling of slewing bearings

slewing bearings

1. Surface purification: Use pickling or chemical cleaning to clean the bearing surface, such as pickling before electroplating, pickling before phosphating, pickling to remove oxide skin burrs, etc. Use pickling liquid to choose cold pickling or hot pickling according to the condition of the metal surface. It is widely used to remove oxide scale on the surface of the cage.

2. Pickling inspection: Use pickling to check the bearing surface defects, which is called pickling inspection or burn corrosion. It is a kind of detection method, commonly used in cold pickling with nitric acid. If the metal surface has cracks, decarburization, peeling, burns and other defects, it can be manifested by cold pickling. In foreign countries, this pickling inspection technology is often classified into the NDT (no inspection) method. Most domestic factories use this inspection method to detect the presence of surface defects.

According to different application purposes, processing requirements and different raw materials, select the correct pickling technology and use the appropriate pickling process (including the selection of acid solution, corrosion inhibitor, process steps, pickling time, etc.), and a special The pickling staff conduct operations and inspections to ensure the pickling effect and the quality of the bearing products. Let’s take a look at the operation process of pickling with Ronda editor.

The process flow of slewing bearing pickling

slewing bearings

1. Preparation before pickling: the bearing parts need to be cleaned before pickling, and the surface should not be dirty with oil, magnetic powder, dust, etc.; if the surface is severely rusted, it needs to be derusted and then pickled.

2. The pickling process:

(1) Put the bearing into a metal cleaner solution for soaking. The concentration of the solution is required to be 4%~5%, and the temperature should be controlled at 75~90℃. If it is pickling, use normal temperature water to dilute the solution. The soaking time is not less than 1 minute.

(2) During the process, the bearing should be shaken or moved to make it fully contact with the solution, and the solution should be kept clean, and the pickling time should be controlled within 5 minutes.

(3) Rinse the soaked bearing in flowing cold water and cool it to room temperature.

3. Inspection after pickling: Check the appearance of the bearing. Its surface should be consistent silver gray or light gray. Generally, the burned position will appear black or bright white, the soft spot position will be dark gray or black, and the decarburized position will be off-white. During the inspection process, the bearing surface is not allowed to be wiped. If in doubt, use absorbent cotton dipped in ethanol or anti-rust solution to wipe.

Slewing Bearings

After the inspection is completed, the bearing should be sent to the anti-rust process in time for treatment to avoid re-oxidation and corrosion of the surface.

3. Precautions for pickling of slewing bearings

1. During the pickling process, the operation should be carried out strictly in accordance with the process sequence, and the process sequence should not be randomly selected.

2. Keep Lingshui flowing and clean during the pickling process and avoid turbidity.

3. The whole process should be carried out under the conditions of good ventilation and safety protection.

4. When replacing the pickling solution, the cleaning tank needs to be cleaned, rinsed with clean water 2-4 times and then the solution is prepared.

5. When preparing the diluted solution, pour the concentrated acid into water or alcohol and keep stirring. If there is solid, stir the solid first and then add the concentrated acid. It is forbidden to pour water into the concentrated acid, which is prone to splashing or danger. accident.

The above is a specific introduction on why the slewing bearing should be pickled and the pickling process. I hope to help everyone better understand the purpose and meaning of pickling. At the same time pickling can help the bearing achieve better performance

Why should the slewing bearing be annealed?

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Why should slewing bearings be annealed? In fact, annealing of slewing ring bearings is a process of bearing heat treatment. Generally, the bearing metal is heated to a certain temperature and kept for a period of time, and then the metal is cooled at a suitable speed. This method improves the toughness of the bearing steel. , Reducing bearing hardness and residual stress can reduce the probability of deformation and cracks, and enhance the stability of bearing materials.

Why should the slewing bearing be annealed?

There may be three reasons for the purpose of annealing the slewing bearing:

1. The annealing process can reduce the hardness of the bearing steel, improve the plasticity, and facilitate the later cutting and deformation processing.

2. Annealing can refine the grains of bearing materials, eliminate structural defects caused during bearing casting, forging, and welding, and uniform the structural structure and steel composition of the steel, which can improve the performance of the steel and prepare for the later heat treatment.

3. The annealing process can eliminate the internal stress in the steel and prevent or reduce the possibility of deformation and cracking of the bearing. In one case, the annealing process is not only for metal materials but also for annealing of non-metal materials. After understanding why slewing bearings should be annealed, the following editor will introduce the types of annealing processes for slewing bearings. In fact, there are many types of annealing processes, and different steel structures are suitable for different processes.

Annealing process type of slewing bearing

Slewing Bearings

1. Recrystallization annealing

Recrystallization annealing is also called full annealing, which is an annealing process in which iron-carbon alloys are austenitized and then slowly cooled or close to equilibrium. The heating temperature of carbon steel is generally Ac3+ (30～50℃); alloy steel is Ac3+ (500～70℃); the holding time depends on the type of steel, the size of the workpiece, the amount of furnace installed, the selected equipment model, etc. The factors are determined. In order to ensure that the undercooled austenite undergoes the pearlite transformation, the cooling of the recrystallization annealing must be slow, and the furnace is cooled to about 500°C and then air-cooled.

This annealing process is mainly used for hypoeutectoid steels, generally medium-carbon steel and low- and medium-carbon alloy structural steel forgings, castings and hot-rolled sections, and sometimes also used for their welding components; it is not suitable for hypereutectoid steels, Because the recrystallization annealing of hypereutectoid steel needs to be heated to above Acm, during slow cooling, cementite will precipitate along the austenite grain boundary and present a network distribution, which will increase the brittleness of the material and leave hidden dangers for heat treatment.

2. Uniform annealing

Uniform annealing is also called diffusion annealing, in order to reduce the segregation of the chemical composition of metal castings or forging billets and the unevenness of the structure. It is heated to a high temperature, maintained for a long time, and then slowly cooled to homogenize the chemical composition and structure. Purpose of annealing process. The heating temperature of homogenization annealing is generally Ac3+ (150～200℃), that is, 1050～1150℃, and the holding time is generally 10～15h to ensure the full progress of diffusion and the purpose of eliminating or reducing the uneven composition or organization. Because the heating temperature of diffusion annealing is high, the time is long, and the crystal grains are coarse, for this reason, recrystallization annealing or normalizing is performed after diffusion annealing to re-fine the structure.

Slewing Bearings

3. Incomplete annealing

Partial annealing is an annealing process in which the iron-carbon alloy is heated to a temperature between Ac1 and Ac3 to achieve partial austenitization, followed by slow cooling. Partial annealing is mainly suitable for medium and high carbon steel and low alloy steel forgings, etc. Its purpose is to refine the structure and reduce the hardness. The heating temperature is Ac1+ (40-60) ℃, and the temperature is slowly cooled after heat preservation.

4. Stress relief annealing

One of the key reasons why slewing bearings should be annealed is the annealing process in order to eliminate the residual stress caused by plastic deformation processing, welding, etc. and the residual stress in the casting. There are internal stresses in the workpiece after forging, casting, welding and cutting. If it is not eliminated in time, the workpiece will be deformed during processing and use, which will affect the accuracy of the workpiece. It is very important to use stress relief annealing to eliminate internal stress generated during processing.

5. Isothermal annealing

Isothermal annealing is to heat the steel or blank to a certain temperature and keep it for a period of time, and then quickly cool it to a certain temperature in the pearlite temperature range and keep it isothermally, so that the austenite is transformed into a pearlite structure, and then in the air Cooling annealing process. This process is suitable for medium carbon alloy steel and low alloy steel, and its purpose is to refine the structure and reduce the hardness. The heating temperature of hypoeutectoid steel is Ac3+(30～50)℃, and the heating temperature of hypereutectoid steel is Ac3+(20～40)℃. Keep it for a certain period of time, and then perform isothermal transformation with furnace cooling to slightly lower than Ar3 temperature, and then air cooling out of the furnace . The isothermal annealing structure and hardness are more uniform than recrystallization annealing.

6. Spheroidizing annealing

Spheroidizing annealing is an annealing process to spheroidize carbides in steel. Heat it to 20-30°C above Ac1, keep it for a period of time, and then slowly cool it to obtain a structure of spherical or granular carbides uniformly distributed on the ferrite matrix.

Spheroidizing annealing is mainly used for hypereutectoid steel and alloy tool steel (such as cutting tools, measuring tools, molds, bearings and other steel grades). The main purpose is to reduce the hardness, improve the machinability, and prepare for later quenching. There are many spheroidizing annealing process methods, and the two commonly used processes are ordinary spheroidizing annealing and isothermal spheroidizing annealing. Compared with ordinary annealing methods, spheroidizing annealing can not only shorten the cycle, but also make the spheroidized structure uniform, and can strictly control the hardness after annealing.

7. Recrystallization annealing

Recrystallization annealing is also called intermediate annealing. It is a heat treatment process in which the cold-deformed metal is heated to a temperature above the recrystallization temperature and kept for an appropriate time to recrystallize the deformed grains into uniform equiaxed grains to eliminate deformation strengthening and residual stress. .

The above is an introduction to the reasons why slewing bearings should be annealed, which also includes the types of annealing processes and their respective characteristics and process introductions. I hope to help everyone have a clearer understanding of the annealing process.

What happens if the slewing bearing is improperly lubricated?

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When buying slewing bearings, slewing bearing manufacturers will tell us to lubricate the bearings regularly, but for those who don’t understand, improper lubrication may occur during lubrication. Then, are the consequences of improper lubrication of slewing bearings serious? ? What happens if the slewing bearing is improperly lubricated? What should be paid attention to when lubricating bearings?

Consequences of improper lubrication of slewing bearings

Slewing Bearings

1. Discoloration

Metal-to-metal contact will make the bearing temperature too high, causing the raceways and rollers to become discolored. In mild cases, this discoloration is due to the lubricant contaminating the bearing surface, while in severe cases, the metal discolors due to high temperatures. In all cases, early detection can avoid costly repairs.

2. Bearing heating

When the machine is running, the part where the bearing is installed is allowed to have a certain temperature. When touching the housing of the mechanism with your hand, it should be normal that you don’t feel hot, otherwise it indicates that the bearing temperature is too high. One of the reasons for excessively high bearings is poor lubrication of the bearings. The lubricating oil (or grease) used in rolling bearings has a certain working temperature. When the temperature is too high, water or ash enters the bearing seat, it will be seriously oxidized, emulsified, etc., which will lose its lubrication effect and cause the bearing to suffer from high temperature. And burned. In addition, poor quality of lubricating oil (or grease) itself or failure to add oil (grease) during operation will cause the bearing temperature to rise.

3. Scratches and peeling

Inspect the bearing for signs of cutting into the metal or peeling of the metal. These situations require immediate attention. Scratches and peeling are prone to occur in high-load low-speed applications or continuous high temperatures, and thin or insufficient lubricating oil film will accelerate the occurrence of the problem. Insufficient lubrication, wrong grease selection, or sudden changes in working conditions may cause bearing material to peel off or bearing ribs to scratch.

4. Abnormal bearing noise

If the bearing is in a good state of continuous rotation, it will emit a low whining or buzzing sound. If there is a sharp hiss, squeak and other irregular sounds, it often indicates that the bearing is in a poor continuous rotation condition. The sharp squeaking noise may be caused by improper lubrication.

5. The bearing is completely locked

Extreme local heating will produce metal flow in the bearing, changing the original material and geometry of the bearing. This may result in excessive tilting of the rollers, damage to the cage, and complete lock-up of the bearing. If catastrophic damage does occur, it is recommended to consult a bearing expert to determine the root cause of the problem, because it may be a factor other than lubrication.

Precautions for correct lubrication

Slewing Bearings

1. Choose the right grease

Choosing a suitable grease will make the grease fully play the role of lubrication in the bearing operation, so that the bearing can be used for a longer time. The following are the points that need to be paid attention to when choosing the grease. Let’s take a look.

(1) Look at the working temperature: The working temperature of the lubricating part is an important basis for choosing lubricating grease. The typical components that use grease are rolling bearings. Under high temperature conditions, the temperature of the outer ring of the bearing is 15°C lower than the temperature of the inner ring. The temperature of the bearing operating at medium and low speeds (3000-5000r/min) is similar to the temperature of the internal medium. Under low temperature conditions, synthetic oil grease must be used, especially for some instrument miniature bearings, which have a small aerodynamic torque. Pay special attention to the selection of grease.

(2) Look at the running speed of the bearing: the speed of the lubricating component has a great influence on the bearing life of the grease. Therefore, when selecting lubricating grease, the movement speed of the lubricated part must be considered.

(3) Look at the environment: the environment of the lubricating part and the medium in contact have a great influence on the performance of the grease.

(4) Look at the filling method: the filling method of grease includes manual filling and centralized pump filling. Smearing or filling, grease gun filling, grease cup filling, etc. are manual filling and automatic filling.

2. Choose the right way

(1) Manual lubrication: This is a relatively primitive method. In the case of insufficient lubricating oil in the bearing, use an oiler to supply oil. It is usually used for light-load, low-speed or intermittent motion occasions. It is recommended to use the oil filler hole during operation. Dust cover or ball valve is set on it, and felt, cotton, wool, etc. are used as filter devices.

(2) Automatic lubrication: The automatic lubricator is a device used to replace manual refueling. The main advantage of this device is to save labor. It can refuel regularly and quantitatively, so that the life of the equipment can be prolonged, especially suitable for more complicated working conditions. Bottom, can reduce the safety risk of manual refueling. Using an automatic lubricator, you can continuously lubricate the running equipment automatically.

3. Add grease in time

Choosing the appropriate grease and lubrication method is the prerequisite for lubrication, but it is also necessary to add grease in time in daily use. This is also a problem that people often ignore or forget. Adding grease in time is to ensure that the bearing is running to meet the operating conditions Lubricating oil, which is also the key to extending the service life of the bearing.

The above is the whole content of the consequences caused by improper lubrication of the slewing bearing and the lubrication method. We understand that improper lubrication of the slewing bearing may cause the bearing to change color, heat, scratch and peel, have abnormal noise, lock up, etc. When lubricating, pay attention to the correct selection of grease and timely add grease, etc., which can effectively avoid the occurrence of improper lubrication.

What are the maintenance tasks in the use of slewing bearings? How to maintain?

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The slewing bearing is an indispensable part of large-scale machinery. It can be installed in the machine to allow the machine to rotate left and right. At the same time, it can withstand various forces. Because the slewing ring is very important, careful maintenance is required. More than 96% of the slewing ring failures are caused by lubrication problems, pollution, wear and incorrect operation, which seriously affects its service life and normal performance.

1. The slewing bearing is coated with a small amount of grease when it leaves the factory. When the product is used, it should be filled with new grease according to different working conditions.

2. The slewing bearing should be greased regularly. According to different types of slewing bearings, the specific grease filling time is as follows:

a: Ball type: Grease is added once every 100 hours of operation.

b; Roller type: Grease is added every 50 hours of operation.

Slewing Bearings

If in a special working environment, such as: tropical, high temperature, dusty, high temperature and continuous continuous work, the grease filling cycle should be shortened, and the grease should be filled once every 50 hours of work; when the gear is working normally, it should be guaranteed to work every time Apply detergent once every 150 hours. When working vigorously, apply detergent once every 75 hours of work. Note that the teeth must be wiped clean before applying detergent. The machine must be refilled with new grease before and after the long-term stagnation of the machine. Each time the grease is added, the raceway must be filled until it overflows from the sealing device. When the grease is added, the slewing ring must be slowly transferred. Make the grease evenly filled in the raceway.

3. Because there are many comprehensive factors in the process of use, the user can choose the grease according to the specific situation. For example, the raceway can use: No. 3, No. 4 graphite grease, industrial grease, No. 203 grease, No. 7002 High and low temperature bearing grease and No. 2 aluminum-based grease, etc.

Since the slewing ring is installed, after 100 hours of operation, the pre-tightening force of the bolts should be checked, and every 500 hours of operation thereafter, it must be adequate and tried.

4. After the equipment has been working for 2000 hours, if a bolt is found to be loose below 80% of the specified torque, the bolt and two adjacent bolts shall be replaced with new ones; if 20% of the bolts are found to be loose to 80% of the specified torque Below, all bolts are replaced with new ones. After the equipment has been working for 14,000 hours, all bolts should be replaced with new ones.

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5. Pay close attention to the operation of the slewing bearing during use. If you find that the noise, impact, or power suddenly increases, you should stop the machine for inspection immediately until all the faults are eliminated, and disassemble and inspect if necessary.

6. When the slewing bearing is in use, it is forbidden to directly wash the slewing bearing with water to avoid water entering the raceway to cause rust; strictly prevent hard foreign objects from approaching or entering the meshing area to avoid injury to the teeth or unnecessary trouble.

7. To keep the surface of the slewing bearing clean, choose a suitable solvent for cleaning according to the surface properties of the rust-proof object, so as to avoid serious corrosion. Surface cleaning can use chemical treatment cleaning method and mechanical cleaning method. When the surface is dry, do a good job in controlling the temperature and wait until most of the area is dry before wiping it with gauze. When applying anti-rust oil, it is necessary to apply different methods according to the different properties of the bearing surface. Miniature bearings can be directly immersed in anti-rust grease. If you encounter a special shape, you can choose the painting method, so that it is not easy to produce accumulation. There are many factors that cause metal corrosion. The chemical composition of the metal itself can also cause corrosion or the temperature and humidity of the environment in which the item exists can also cause corrosion.

8. The sundries on the surface of the slewing ring should be removed frequently during use, and the sealing strips of the slewing ring should be checked for aging, cracking, damage or detachment. If one of these conditions occurs, the sealing strips should be replaced in time to prevent debris and debris from entering the raceway. If the grease is lost, the corresponding grease should be applied after replacement to avoid jamming or rusting of rolling elements and raceways.

The above is a detailed explanation of the maintenance work in the use of the slewing ring. In short, the slewing ring has malfunctions such as noise and impact after a period of use. The operator should pay attention to observe and check in time to eliminate the fault. Only correct and reasonable maintenance of the slewing bearing can ensure its normal operation, give full play to its performance, and extend its service life.

Scrap Standard and Service Life of Tower Crane Slewing Bearing

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All machines will suffer loss and failure after a long period of use. When the parts exceed the service life or are damaged beyond repair, they should be scrapped and replaced. The tower crane slewing bearing is prone to failure and damage when subjected to harsh outdoor environments and high-load operation for a long time. So to what extent can it meet the scrap standard of the tower crane slewing bearing?

The scrap standard of tower crane slewing bearing

Slewing Bearings

1. The slewing ring and rolling elements are worn out and scrapped

The wear of raceway ring and rolling element is one of the common forms of slewing bearing scrap. When the raceway pitting corrosion occurs on the surface of the slewing bearing, the surface metal is peeled off and the overall wear is worn, the tower crane will experience abnormal noise, rolling element jamming and excessive clearance between the raceway rings during operation; vibration and local impact will be caused. With the development of the state, the turning resistance will continue to increase and the turning function will be lost.

2. The slewing ring cage is damaged and scrapped

In order to avoid friction between the rolling elements of the tower crane slewing support, an isolator cage is usually added between the rolling elements. The material of the cage is generally copper, plastic, powder metallurgy or mild steel. The cage does not transmit load during the bearing, but it moves with the rolling elements. When the cage is damaged or broken, there will be a sharp and piercing noise. As the broken body of the cage is pushed and crushed by the rotating rolling elements, it will cause serious damage to the raceway ring and rolling elements. At this time, the slewing bearing meets the scrap standard and can be replaced.

3. The slewing ring teeth are damaged and scrapped

The gear meshing mode of the tower crane slewing support has two kinds of external gear meshing and internal gear meshing. When the surface of the gear teeth is excessively worn, cracks and broken teeth appear. The tooth side clearance of the gear teeth of the tower crane slewing bearing is enlarged, and the slewing bearing will immediately lose its function when the tooth is broken and cannot be repaired. At this time, it reaches the scrap standard of the tower crane slewing bearing.

4. The slewing ring connecting bolts are damaged and scrapped

Although the connecting bolt of the slewing ring is not the bearing body, the failure of the bolt will also cause the slewing ring to fail to work. The damage of connecting bolts in tower crane work is also a common phenomenon. When a slewing bearing connecting bolt is loosened or broken, it will often cause a chain reaction to cause the loosening and fracture of other bolts. At this time, the slewing bearing also needs to be replaced.

5. The slewing bearing is damaged and scrapped due to corrosion and burns

Due to the complex working environment of the tower crane slewing bearing, the situation that the bearing may encounter is also unpredictable. If it is corroded by corrosive substances such as acid and alkali during operation, the internal components of the bearing will be damaged and the bearing will be scrapped.

The service life of the tower crane slewing bearing

Slewing Bearings

Under a certain load, the number of revolutions or hours that the bearing experiences before pitting corrosion is called the bearing life. The service life of the tower crane slewing bearing is affected by the speed, radial load, basic rated load, equivalent conformity, speed coefficient, and fatigue life coefficient.

1. Calculation formula of bearing life

L10-When the bearing load is P, the basic rating life (106 revolutions)

C–Basic dynamic load rating N

ε–index

Ball bearing: ε=3

Roller bearing: ε=10/3

P–Equivalent dynamic load (N)

The load on the bearing under actual conditions: A, R, transformed into the load under experimental conditions is called equivalent dynamic load. For bearing components, this load is variable. In the experimental study, the bearing life is changed to 106 The unit is more convenient (counter), but in actual production, the life is generally expressed in hours. For this reason, it must be converted L10×106=Lh×60n

2. Calculation method of tower crane slewing bearing life

(1) Knowing the bearing model, load and shaft speed, calculate Lh;

(2) Knowing the load, speed and expected life, calculate C and select the bearing model.
Usually take the middle repair or overhaul limit of the machine as the design life of the bearing, generally Lh’=5000, and the temperature coefficient ft should be introduced for the bearing working at high temperature

Ct=ftC

t ≤120 125 150 200 300

ft 1 0.95 0.90 0.80 0.60

The above is about the relevant content of the scrap standard of the tower crane slewing bearing. The tower crane’s service life may be affected due to its complicated use environment. At the same time, good maintenance and repair can also extend the service life of the tower crane slewing bearing.

What are the reasons for the deformation of the slewing bearing?

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Slewing bearings are widely used on rotating machines such as ferris wheels and excavators, and the wide range of applications also reflects that the work load of slewing bearings is relatively high, and high-load work makes slewing bearings in use. Many problems will be encountered, and bearing deformation is one of the more common problems. So, what are the reasons for the deformation of the slewing bearing? How can we control the deformation of the slewing bearing? The slewing bearing manufacturer will introduce the related problems of the deformation of the slewing bearing, and I hope it will be helpful to everyone.

Causes of deformation of slewing bearings

Slewing Bearings

1. Irregular installation

In fact, there are still more attentions in the installation process of slewing bearings. For example, in the process of bearing installation, it is necessary to accurately calculate the interference of the rotating ferrule and the appropriate fit of the fixed ferrule. Especially slewing bearings work on machines like excavators, ferris wheels, etc., and the temperature rises easily during the working process. At this time, special attention should be paid to the matching of the rotating ring not to be too loose to prevent eccentric vibration, and There must be no gap in the fit of the fixed ferrule to prevent the ferrule from deforming under load and excite vibration, which will affect the service life of the bearing.

2. Bearing wear

Wear is almost accompanied by the entire life cycle of the machine, but this natural wear has a certain degree of stability. However, if the amount of lubricating oil is too low or missing, it will cause rapid wear of the bearing, and the damage to the bearing by this unnatural wear will be irreversible. Only by overhauling the machining accuracy and straightness of the bearing can it be completely repaired.

3. Friction heat generation

During the working process of the slewing bearing, the temperature rises due to the load of the workpiece and the friction between the bearing rolling elements and the inner and outer rings, which causes the bearing to deform due to heat expansion. If the amount of lubricating oil is sufficient and effective, this kind of thermal deformation can be effectively curbed. I am afraid of the dry grinding caused by the lack of lubricating oil in the second case mentioned above. In this state, not only will the bearing raceway wear and out of stock, but also a large amount of frictional heat will be generated, which will cause bearing damage and premature failure.

Methods to prevent deformation of slewing bearings

Slewing Bearings

1. Reasonable installation

(1) Keep hands clean and dry when taking out: When the turntable bearing is taken out of the package, the operator’s hands should be kept clean and dry, because sweat on the hands can cause rust, and gloves can be worn if necessary. However, it is necessary to pay attention to gloves. It is recommended to use cotton gloves to avoid scratching the bearings due to the rough surface of the gloves.

(2) Reasonable use of force: during bearing installation, the installation force should not be transmitted through the bearing rolling elements, and attention should be paid to the control of the force during installation, to avoid direct application of force to the bearing, and to minimize the effect of force on the bearing. Injury caused by the bearing.

2. Lubricate correctly

(1) Lubricant selection: When choosing the right grease for rolling bearings, you usually need to consider the following factors: bearing type, speed, working temperature and load, as well as installation position, sealing, shock and vibration, and consideration The requirements of laws and regulations and environmental protection, only to meet these requirements is a more suitable grease.

(2) Grease adding method: common slewing bearing grease adding methods include oil mist lubrication, oil-air lubrication, grease lubrication, jet lubrication, etc. Among them, grease lubrication does not require any equipment and is a relatively common lubrication method. The lubrication method is simple and easy to operate. Other methods have their own advantages. You can consider them according to the situation.

3. Ensure that the slewing bearing is clean

(1) Bearing cleaning: When cleaning, you should first pinch the inner ring of the bearing with one hand, and slowly rotate the outer ring with the other hand, until the oil on the rolling elements, raceways and cage of the bearing is completely washed off, then clean the bearing. The surface of the outer ring. At the beginning of cleaning, it should be rotated slowly, swayed back and forth, and rotated too hard, otherwise the raceways and rolling elements of the bearing will be easily attached to dirt.

(2) Isolation of impurities and dust: Bearings are easy to hide dirt and dirt. After all, the working environment of bearings is more complicated. Therefore, after the bearing cleaning work is completed, it is recommended that you use a layer of grease to seal it. This can reduce bearing contamination.

The above is a summary of the reasons for the deformation of the slewing bearing, the reasons and prevention methods. It can be seen that the reasons for the deformation of the slewing bearing include irregular installation, bearing wear, friction and heat generation, etc., and the corresponding prevention Measures include reasonable installation, effective lubrication, and keeping clean.

How long is the service life of the slewing bearing? What are the factors that affect the service life?

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How long is the service life of slewing bearings in general? There are many factors affecting the service life of a bearing. Different working conditions, different materials, and different bearing types will affect the service life of the bearing. For this reason, the service life is not a standardized number but is based on the material, process, and production level during production. As well as the use method, maintenance lubrication conditions and other factors in the process of use, it is comprehensively determined. Let’s take a look at the factors that determine the service life of the bearing and the method of extending the service life with the slewing bearing manufacturer.

How long is the service life of the slewing bearing?

According to the influence of the bearing material, assembly, tolerance fit, lubrication and other factors, the service life of the slewing bearing under normal conditions ranges from 10,000 to 192,000 hours. We generally say that the service life of bearings is different on different types of bearings. Like ordinary bearings, the service life of the bearing refers to the failure of use, such as pitting, spalling and other conditions that cannot work normally. For spindle bearings and precision bearings that require high precision, they will fail when the running accuracy of the bearing fails to meet the requirements, but it is far below the standard for ordinary bearing failure. So this is also the reason why the service life of the slewing bearing is different.

Factors affecting the service life of slewing bearings

Slewing Bearings

1. Manufacturing factors

(1) Design: Whether the diameter, quantity, ring wall thickness, effective length of rolling contact, tightness, radian and size of the raceway contact surface of the bearing rolling elements are compatible with the adapted equipment.

(2) Material: Martensite in the quenched steel during the bearing production process, impurities in the steel, chemical composition, gas, cracks, etc. The impact of the material on the quality of the bearing is hard damage, which cannot be compensated by technology in the later stage.

(3) Manufacturing: In the process of producing slewing bearings, bearing parts hardness, bearing metallographic structure, surface burns, bump scratches, roughness, poor parts grouping, production accuracy, bearing clearance, cleanliness, residual magnetism and parts Residual stress on the working surface will affect the service life of the bearing. The impact during the manufacturing process is similar to the inherent quality problem. Under the same working conditions, a defective bearing has a shorter life than a standard and qualified bearing.

Slewing Bearings

2. Use factors

(1) Model selection: In terms of model selection, such as bearing load, hardness, operating environment, etc., a good bearing design will first enable the bearing to reach the upper limit of the theoretical life.

(2) Assembly: the installation accuracy of the bearing, the matching degree of the bearing shaft and the seat hole, the selection of various parts, dimensions, shape and position accuracy, the selection of assembly tools, and the cleanliness of installation whether there are impurities mixed in, including the assembly position and assembly of each part Clearance, preload size, lubricant selection and filling amount, etc.

(3) Working environment: The working temperature and the cleanliness of the working environment affect the service life of the bearing. If the operating environment of the bearing is in a harsh environment or a high temperature, high temperature, low temperature and severe cold environment, it may affect the performance of the bearing. The service life has a certain impact.

(4) Load: Each bearing has a rated load when it is produced. There is a range for the load borne during the bearing operation, that is, the force condition. If it exceeds this range for long-term overload operation, the performance of the bearing may be seriously affected. The impact of this, which in turn affects the service life.

(5) Lubrication: Bearing lubrication is a key factor in reducing the friction between the various parts of the bearing and reducing the occurrence of damage and deformation. Therefore, whether the bearing lubrication is appropriate, timely and reasonable has a certain impact on the service life of the bearing.

The above is the relevant answer about how long the service life of the slewing bearing is generally. In fact, if you want to extend the service life of the bearing, you only need to correctly select and assemble, maintain a good working environment, and use it correctly to maintain and supplement the lubricant. The service life of the bearing can be increased.

What are the oil lubrication methods for slewing bearings?

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The slewing bearing needs to be lubricated during use and storage. The common lubrication methods are grease lubrication and oil lubrication. The medium for grease lubrication is grease, and the oil lubrication is lubricating oil. Then, for the turntable In terms of bearings, what are the benefits of using oil lubrication? What are the oil lubrication methods for slewing bearings? The following is a summary made by the editor for everyone, let’s take a look.

The benefits of oil lubrication for slewing bearings

The slewing bearing is lubricated by oil lubrication, which can achieve good cooling and cooling effects. This oil lubrication method is very suitable for bearings with relatively high operating temperatures. The viscosity of the lubricating oil used in the bearing is about 0.12 to 0.2cm/s. If the bearing load is high and the working temperature is high, choose a high-viscosity lubricating oil, and a rolling bearing with a fast speed is suitable for a low-viscosity lubricating oil. But it should also be noted that oil lubrication requires that the bearing must be kept in a good sealing state to avoid leakage of lubricating oil. In addition, oil lubrication requires a more complicated oil supply device, so you must pay more attention to the operation and use, and pay attention to the use and maintenance of the bearing.

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The method of lubricating slewing bearing oil

1. Oil bath lubrication

Oil bath lubrication is a relatively common lubrication method. It is suitable for the lubrication of low and medium speed bearings. Imported bearings are partially immersed in the groove, and the lubricating oil is picked up by the rotating bearing parts and then flows back to the oil groove. The oil level should be slightly lower than The center of the lower rolling element.

2. Dripping oil lubrication

Drip lubrication is suitable for imported bearing parts that require a quantitative supply of lubricating oil. The amount of dripping oil is generally one drop every 3-8 seconds. Excessive oil volume will cause the bearing temperature to increase.

3. Circulating oil lubrication

Use an oil pump to deliver the filtered oil to the bearing components, and then filter and cool the lubricating oil after passing through the bearing for use. Because circulating oil can take away a certain amount of heat and cool the bearing, this method is suitable for bearing parts with higher speeds.

4. Spray lubrication

Dry compressed air is mixed with lubricating oil through a sprayer to form oil mist. Injecting into the bearing, the airflow can effectively cool the bearing and prevent the intrusion of impurities. This method is suitable for the lubrication of high-speed and high-temperature bearing components.

5. Jet lubrication

Use an oil pump to inject high-pressure oil into the bearing through a nozzle, and the oil injected into the bearing flows into the oil groove through the other end of the bearing. Imported bearings have higher rated load, lower noise, greatly reduce warranty costs, increase machine running time and other advantages; when distinguishing the authenticity of such imported bearings, you can touch the steel stamp on the bearing to make it faster and more efficient. Accurately distinguishing, this kind of steel seal will not feel tactile if you touch it with your hand, but you can feel the presence of the steel seal by gently touching it with your fingernail. When the bearing rotates at a high speed, the rolling elements and the cage also make the surrounding air form an airflow at a relatively high rotation speed. It is difficult to send the lubricating oil to the bearing by the general lubrication method. At this time, the lubricating oil must be sprayed by high-pressure injection. In the bearing, the position of the nozzle should be placed between the inner ring and the center of the cage.

The above is the slewing bearing manufacturer’s summary of the oil lubrication methods for slewing bearings, the benefits of slewing bearing oil lubrication and all the common methods. We understand that oil lubrication can help the bearing achieve a good cooling and cooling effect. The oil lubrication methods include oil bath lubrication, drip lubrication, circulating oil lubrication, spray lubrication, jet lubrication, etc. You can choose according to your own reagent needs

How often is the slewing bearing maintained and how to maintain it?

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After the slewing bearing is used for a period of time, it is inevitable that there will be problems such as noise, vibration, and temperature rise. In this case, if you want to extend the service life of the bearing, you need to maintain the slewing bearing regularly. Then, how long is the slewing bearing? Maintenance once? What is the maintenance method? What problems should be paid attention to during maintenance? Next, the slewing bearing manufacturer will introduce the maintenance cycle and method of the slewing bearing to everyone, and I hope it will be helpful to everyone.

Slewing bearing maintenance cycle

How often is the slewing ring bearing maintained? The maintenance time of slewing bearings is the same as that of ordinary bearings. Theoretically, they can be used for 20000-80000 hours, but the specific life depends on the wear during use, work intensity and later maintenance, etc., among which maintenance is an important part of prolonging the service life of the bearing. ring.

Maintenance method of slewing bearing

Slewing Bearings

1. Clean the slewing bearing

Cleanliness has a considerable impact on the life of the slewing bearing. The higher the cleanliness of the bearing, the longer the life. Lubricants with different cleanliness have no effect on the life of the bearing. Therefore, improving the cleanliness of the lubricating oil can prolong the life of the bearing. In addition, if the dirt particles in the lubricating oil are controlled below 10um, the life of the bearing will also increase several times. So, how should the specific bearing cleaning be done? We then look down.

(1) The cleaning of the bearing is divided into rough cleaning and fine cleaning, and a metal grid can be placed on the bottom of the container in use.

(2) For rough washing, use a brush to remove grease or adhesions in oil. At this time, if the bearing is rotated in oil, be careful that the rolling surface may be damaged by foreign matter.

(3) During the fine washing, slowly rotate the bearing in oil, which must be carried out carefully. Commonly used cleaning agents are neutral non-water-containing diesel or kerosene, and sometimes warm lye etc. are used as needed. No matter what kind of cleaning agent is used, it must be filtered frequently to keep it clean. After cleaning, immediately apply anti-rust oil or anti-rust grease on the bearing.

2. Derusting bearings

(1) Soaking method: Some small items are immersed in anti-rust grease, and the cross tapered roller bearing is coated with a layer of anti-rust grease on the surface. The thickness of the oil film can be achieved by controlling the temperature or viscosity of the anti-rust grease.

(2) Brushing method: used for outdoor construction equipment or products with special shapes that are not suitable for immersion or spraying. When brushing, it is necessary to pay attention not to accumulate, but also to prevent leakage.

(3) Spray method: Some large anti-rust objects cannot be oiled by immersion method. Bearings are generally sprayed in clean air with filtered compressed air with a pressure of about 0.7Mpa. The spray method is suitable for solvent-diluted anti-rust oil or thin-layer anti-rust oil, but complete fire protection and labor protection measures must be adopted.

3. Bearing lubrication

(1) Manual lubrication: This is a relatively primitive method. When the lubricating oil of the bearing is insufficient, use an oiler to supply oil. However, this method is difficult to maintain a certain amount of oil. It is more dangerous to forget to refuel due to negligence. It is usually only used in light-load, low-speed or intermittent sports. It is recommended to install a dust cap or ball valve on the refueling hole and use it. Felt, cotton, wool, etc. are used as filter devices.

(2) Dropping point lubrication: usually used for light-load and medium-load bearings with a peripheral speed of less than 4~5m/s. A roughly fixed amount of lubricating oil is supplied from the container through holes, needles, valves, etc., the more classic is dripping oil Cup, the amount of dripping oil varies significantly with the viscosity of the lubricating oil, the bearing clearance and the position of the oil supply hole.

(3) Oil ring lubrication: The lubricating oil from the oil pool is brought to the bearing by the ring that is hung on the shaft and can rotate (only for the lubrication method of the horizontal shaft), suitable for medium and high speed shaft diameters greater than 50mm Bearings and oil rings are recommended to be seamless. When the bearing width-to-diameter ratio is less than 2, only one oil ring can be used, otherwise two oil rings are required.

(4) Oil rope lubrication: Relying on the capillary and siphon action of the oil rope to guide the lubricating oil in the oil cup to the bearing, it is mainly used for light-load and medium-load bearings with a peripheral speed of less than 4～5m/s. Can play a filtering role in the whole process.

(5) Oil pad lubrication: Use the capillary action of the oil pad to apply the lubricating oil in the oil pool to the surface of the shaft diameter. This method can keep the friction surface clean, but dust will also block the pores and cause insufficient oil supply. The oil supply of oil pad lubrication is usually only 1/20 of oil lubrication.

Precautions for maintenance of slewing bearings

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1. Precautions for cleaning

(1) Qualified new bearings are not cleaned: New bearings that have passed inspections may not be cleaned under normal operating conditions (motors with more than 2 poles); new sealed bearings are not cleaned.

(2) Clean before oil change: The bearing cap and bearing must be cleaned before oil change. The cleaning is divided into rough washing and fine washing. The oil for rough washing is clean diesel or kerosene, and the oil for fine washing is clean gasoline.

(3) Inspection during cleaning: After the bearing is cleaned, turn it by hand and shake it radially and axially by hand to determine whether it is loose or the gap is too large. Check the gap if necessary. If the ball or roller frame is found to be severely worn, rusted, and metal peeling, it should be replaced.

(4) Wipe dry and grease after cleaning: After the bearing is cleaned and inspected, wipe the cleaning agent (or dry) with a white cloth, and add qualified grease. It is not allowed to add different types of grease in the same bearing.

2. Precautions for rust removal

(1) Selection of derusting liquid: Note that the following acid liquids cannot be used for bearing derusting: sulfuric acid, hydrochloric acid, dilute sulfuric acid, and dilute hydrochloric acid. Because these acid liquids will destroy the good metal parts, these kinds of liquids cannot be used!

(2) Selection of rust removal methods: I have introduced several common rust removal methods above, including soaking method, brushing method, spraying method, etc. You can choose according to the actual situation of the bearing, but no matter which method it is It is necessary to pay attention to the protection of the bearing during operation. The damage to the bearing due to maintenance is more than the loss.

3. Precautions for lubrication

(1) No dust in the surrounding environment when refueling: refuel with clean hands, slowly rotate the entire bearing with one hand, and press the oil into the bearing gap with the middle finger and index finger of the other hand. After adding one side, proceed to the other side to remove excess grease.

(2) Bearing and bearing cap refueling volume: The bearing cap oil volume is 1/2-2/3 of the bearing cap capacity (the highest number of poles of the motor is the upper limit); the bearing oil volume is 1/2-2/3 of the cavity of the inner and outer rings of the bearing ( The number of motor poles is higher than the upper limit).

The above is about how often the slewing bearing is maintained, the maintenance cycle and the entire content of the method. We understand that the general slewing bearing is maintained every 20000-80000 hours. The specific time needs to be determined according to the actual situation. The maintenance method includes regular cleaning, which is effective. Rust, reasonable lubrication, etc. It can be seen that if you want to extend the service life of the slewing bearing, you still need to work harder and maintain it.