Is the surface roughness of the slewing bearing as small as possible? How to choose?

Is the surface roughness of the slewing bearing as small as possible? Surface roughness refers to the small spacing and the unevenness of small peaks and valleys that the machined surface has. The roughness of the bearing surface may affect the wear resistance, stability, fatigue strength, stability and other properties of the bearing. Generally speaking, the smaller the roughness of the bearing surface, the better, but it should be determined according to the equipment use requirements and process accuracy.

The surface roughness of the slewing bearing is not as small as possible

Slewing Bearings

Is the surface roughness of the slewing bearing as small as possible? It can be analyzed from the following aspects:

1. Physical properties of materials

The surface roughness of the bearing is often represented by Ra. Generally speaking, from the working principle, we hope that the smaller the surface roughness of the slewing bearing, the better. Generally, the higher the bearing tolerance accuracy level, the better the surface quality and the finer the workmanship. However, two surfaces that are too smooth are prone to gluing (exchange between the same or similar materials, which is similar to the “dyeing phenomenon” in our life, but it belongs to the exchange of metal substances here), while the surfaces that are too rough are prone to gluing. Under the action of force, the surface is prone to peeling off (that is, what we often call wear).

2. Processing cost

Theoretically, the smaller the value of the surface roughness of the slewing bearing, the better, the smaller the roughness, the smoother the surface and the more beautiful the appearance. However, the size of the roughness is determined by the machining process and other factors, such as the friction between the tool and the bearing surface, cutting, and high-frequency vibration in the process.

However, the smaller the surface roughness, the higher the processing cost. Whether the use cost of the part matches the consumption speed and the profit of the equipment production output value. These all need to be considered. Some spare parts do not have high requirements on the roughness of the bearing surface. Excessive pursuit of the surface roughness will affect the economy of processing.

Selection principle of surface roughness of slewing bearing

slewing bearing

1. Economic perspective:

From an economic point of view, on the basis of meeting the performance requirements of the slewing bearing, the lower the accuracy, the better. This allows for lower production costs.

2. Use function:

(1) The roughness value of the working surface is smaller than that of the non-working surface.

(2) The roughness value of the friction surface is smaller than that of the non-friction surface.

(3) The roughness value of the clearance fit is smaller than that of the interference fit.

(4) The roughness of the mating surface should be equivalent to its dimensional accuracy requirements. The smaller the size, the smaller the roughness value should be.

(5) The roughness value of the surface subjected to cyclic load and the inner fillet and concave part where stress concentration may occur should be small.

Is the surface roughness of the slewing bearing as small as possible? I believe everyone is clear. The actual selection of bearing accuracy and surface roughness needs to be determined according to actual needs. In the case of ensuring bearing performance, cost control is also very important.

Slewing Bearing Comes In Many Sizes

Slewing bearing comes in many sizes

LDB Slewing Bearing Manufacturer custom designed and manufactured a segmented, 3-row roller bearing almost 14 m in diameter. It weighed 70 tons.LDB Slewing Bearing Manufacturer also produces a range of smaller slewing bearings for special machinery,high-tech applications and more.

For more than a half century, LDB Slewing Bearing Manufacturer has been designing and manufacturing many types and sizes of high-performance slewing bearings to meet the speciic needs of customers worldwide. Combining decades of application knowledge and unmatched manufacturing expertise, LDB Slewing Bearing Manufacturer provides customised slewing bearings with outer diameters from 0,1 m to 14 m.

Unlike other providers of slewing bearings, LDB Slewing Bearing Manufacturer can offer fully tailored slewing bearing solutions with integrated advanced monitoring, lubrication and sealing systems for higher reliability and longer service life. Our breadth of engineering knowledge, global presence and design lexibility allow us to deliver the right solution for your project, no matter how large or complex.

High-performance slewing bearings

For a wide range of applications:

  • Wind turbines
  • Tunnel boring machines
  • Excavators
  • Forestry vehicles
  • Rail vehicles
  • Dockside and deck cranes
  • Mobile cranes
  • Water treatment equipment
  • Bottle illing systems
  • Metals
  • Material handling
  • Marine pods
  • Offshore buoys
  • Stacker reclaimers

Model parameters of externally toothed three-row cylindrical roller slewing bearings

Slewing bearing design types:

  • Double row ball bearings
  • 4point

Contact bearings

  • Crossed roller bearings
  • Wire race bearings
  • 3row

and double row cylindrical roller bearings

  • Cylindrical roller and ball bearings
  • Special bearings

How is the slewing bearing soft belt produced? The installation position of the flexible belt

The raceway of the slewing bearing generally needs to be heat treated. In the heat treatment process, because the diameter of the raceway circle of the slewing bearing is relatively large, flame surface quenching is usually used. The method is to use acetylene to heat the surface of the workpiece to be hardened and then add water to cool it. , this process is completed continuously.

1. How is the slewing bearing soft belt produced?

During the production and processing of the slewing bearing, the raceway of the device generally needs to be heat treated. The usual processes are: forging → rough machining → quenching and tempering treatment → finishing → raceway surface flame surface quenching → raceway surface grinding and other processes . One of the raceway surfaces is flame quenched to form a soft band.
The so-called soft belt is the area that has not been heat treated. The formation of the soft band is necessary for the heat treatment process. In the heat treatment process of the slewing bearing, because the diameter of the raceway circle of the slewing bearing is relatively large, flame surface quenching is usually used. The method is to use acetylene to heat the surface of the workpiece to be hardened and then add water to cool it.

Slewing Bearings

The heated flame spray gun and water gun are mounted together while making a circular motion along the circle of the workpiece. When the movement is close to 360 degrees, the heating and water spray are stopped immediately. That is, the circular areas of heating and water spray do not overlap. Cracks in the workpiece can occur if the circle areas where the heating and water spray occur overlap (heat treatment at an angle greater than 360 degrees on the circle). The tangential width of the unheated area is typically 15 mm. This 15 mm area is called the soft belt in the slewing bearing, that is, the so-called soft belt is the area without heat treatment. The formation of the soft band is essential to the heat treatment process.
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Under normal circumstances, the steel character “S” is marked on the position where the soft belt exists in the workpiece to indicate the specific soft belt position. The installation position of the soft belt is essentially to improve the life of the bearing. From the perspective of the user and the manufacturer, it is still a reasonable position to install the upper and lower ring soft belts of the slewing bearing. Therefore, the manufacturer of the slewing bearing should accurately mark the position of the soft belt of the slewing bearing, and the manufacturer and installer should reasonably install the position of the soft belt of the slewing bearing as needed.

2. The installation position of the soft belt

Slewing Bearings

Usually the upper loop flexible belt of the slewing device is installed at a position perpendicular to the projection line of the pitching rotation plane. For example, the upper loop flexible belt of the slewing device of a ship loader or stacker-reclaimer should be installed at a position perpendicular to the center line of the cantilever and cut through the center of rotation , that is, standing at a 90-degree position facing the left or right side of the cantilever on the center of rotation. In the usual mechanical design, the soft belt does not have the stress state of the support roller of the slewing bearing device at this position.

The installation position of the lower ring soft belt of the slewing device should be determined according to the center of gravity of the equipment and the range of the slewing angle. If the rotation angle is 100 degrees left and right, and the center of gravity of the upper part of the rotation is in the front, it is recommended to install the lower ring soft belt at the rear, that is, at a position of 180 degrees. If the change position of the center of gravity of the upper part of the rotation is the same in the front and rear positions, the angular position of the lower ring soft belt can be installed arbitrarily.
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Because of the inevitability of the soft belt on the slewing bearing device, it is required that the user who uses and selects the slewing bearing device should install the position of the soft belt reasonably, so as to improve the service life of the bearing. The general principle is to try to install the soft belt in a position where the soft belt is under less pressure during the load change.

What are the sealing methods of the slewing bearing? Sealing function and method

We know that the slewing bearing has a very important role in some production, and in order to ensure these functions, we need to perform a lot of operations on the slewing bearing during the use of the slewing bearing. The sealing of the more common bearings, then why should the slewing bearing be used? to seal? What are the common sealing methods of slewing bearings?

The role of sealed slewing bearing

Slewing Bearings

1. Isolate foreign objects from outside

Protect the bearing to prevent external dust, dirt, metal particles, moisture, acid gas and other debris from invading the inside of the bearing. If the bearing is poorly sealed and external debris invades, the working condition of the bearing will be significantly deteriorated, and the service life of the bearing will be significantly reduced.

2. Prevent grease leakage

If the oil leaks, it will quickly destroy the normal lubrication of the bearing, causing the bearing to burn out due to heat. In addition, the poor sealing device not only causes waste of oil leakage, but also contaminates mechanical equipment and processed products. Therefore, to make the machine work properly, the bearing must have a good sealing device.

The way of sealing the slewing bearing

Slewing Bearings

Generally, the sealing methods of bearings include contact sealing and non-contact sealing, but these two sealing methods are suitable for different situations. Contact sealing is suitable for bearings operating in medium and low-speed working environments, while non-contact sealing Bearings that are suitable for high-speed and high-temperature working environments, as slewing bearings, generally operate at low speeds, but there are also high-temperature operations. The analysis shows that the methods of sealing slewing bearings are as follows:

1. Felt ring seal

A trapezoidal groove is opened on the bearing cover, and the fine felt on the rectangular surface is placed in the trapezoidal groove to contact the shaft, or the gland is pressed axially, so that the felt ring is compressed to generate radial pressure and hug the shaft, thereby achieve the purpose of sealing. The sealing structure is simple and the cost is low, but the sealing effect is poor, it cannot be adjusted, and the wear is serious.

2. The leather bowl is sealed

Place a sealing cup in the bearing cover (the cup is made of rubber and other materials) and press it directly on the shaft. In order to enhance the sealing effect, a ring-shaped coil spring is used to press the inner ring of the leather cup, so that the inner ring of the leather cup and the shaft have a tighter fit, and the sealing effect is better than that of the felt ring. /s of grease lubrication or lubricating oil lubrication.

3. Sealing ring seal

The sealing ring is usually made of leather, plastic or oil-resistant rubber, and can be made into different cross-sectional forms as required. The 0-shaped sealing ring has a circular section and is pressed on the shaft by its own elastic force. It has a simple structure and is easy to assemble and disassemble. Also commonly used are J-shaped and U-shaped profile seals, which all have a lip-shaped structure. The direction of the sealing lip is towards the sealing part, which is similar to the direction of the flange in the cup seal. When the temperature is high and the rotational speed is high, it is recommended that the sealing lip also be installed away from the bearing. The sealing effect of the sealing ring is better than that of the felt ring, and it can be used for the sealing of grease and oil.

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4. Skeleton seal

The skeleton seal we often say is the improvement of the leather cup seal. In order to improve the overall strength of the leather cup seal, a metal lining with an L-shaped cross-section and an overall annular shape is installed in the oil-resistant rubber, so that the leather cup seal is not easily deformed and improves the use of This kind of seal is easy to install and has good performance. It is generally suitable for occasions where the peripheral speed of the journal is 7m/s.

5. Sealing ring seal

This is an annular seal with a gap, which is placed in the ring groove of the sleeve, the sleeve rotates with the shaft, and the seal ring is pressed against the static part by the elasticity of the gap after being compressed. On the inner hole wall, it can play a sealing role, and this kind of sealing is more complicated.

6. Labyrinth seal

The basic principle of this kind of seal is to form a section of flow channel with great flow resistance at the seal. Structurally, a small tortuous gap is formed between the stationary part and the rotating part, forming a “labyrinth”. If the “labyrinth” is radial, the axial dimension is compact, but the radial dimension is larger. If the “labyrinth” is axial, the radial dimension is compact, but the bearing cover should be divided, and the axial clearance should be larger, so as not to be stuck due to thermal deformation of the shaft. Labyrinth seals are quite reliable for both lubricating oil and bone grease, and the higher the speed, the better the effect.

The above is the summary of the sealing methods of the slewing bearing, and the whole content of the sealing function and method. We have learned that the slewing bearing has the functions of isolating foreign objects and preventing grease leakage. The common methods are felt ring sealing, leather cup Seal, seal ring seal, skeleton seal, seal ring seal, labyrinth seal, etc., you can choose according to the specific situation of your bearing

What are the classifications of slewing bearings? How to choose a model?

There are many classifications of slewing bearings, each type has different characteristics, and the scenarios used are also different. You may not be very clear about the selection type. Generally, the selection type should be considered: slewing accuracy, bearing capacity, working temperature, In terms of running speed, etc., let’s take a look at the specific method with the slewing bearing manufacturer~

Classification of slewing bearings

Four Point Contact Ball Slewing Bearing

1. Three-row combined roller slewing bearing

The three-row roller slewing bearing has the upper and lower and radial raceways of the three races separated, so that the load of each row of rollers can be accurately determined. It can bear various loads at the same time, has a firm structure, and has large shaft and radial dimensions. It is suitable for heavy machinery requiring large diameters.

2. Double row angular contact ball slewing bearing

The double-row ball slewing bearing has three races, and the steel balls and spacers can be directly discharged into the upper and lower raceways. According to the stress conditions, two rows of steel balls with different diameters are arranged. The axial and radial dimensions of the double-row ball slewing bearing are relatively large, and the structure is firm, especially suitable for machinery that requires a medium or larger diameter.

3. Single row cross roller slewing bearing

The single-row cross-roller slewing bearing is composed of two races, with compact structure, high manufacturing precision, light weight, small assembly clearance, and can bear axial force, large radial force and tipping moment at the same time.

4. Single row four-point contact ball slewing bearing

The single-row four-point contact ball bearing slewing bearing is composed of two races, with compact structure, light weight, four-point contact between the steel ball and the arc raceway, and can bear axial force, radial force and tipping moment at the same time.

Factors to consider when choosing a slewing ring bearing type

Double Row Different Diameter Ball Slewing Bearing

1. Carrying capacity

The bearing capacity is one of the factors that determines the size of the bearing. In general, the four-point contact ball slewing bearing can withstand heavier radial loads, so it may be more suitable for the occasions where the heavier load and the size and direction of the load may change The four-point contact is a slewing bearing.

2. Rotation accuracy

If the bearing positioning capability is required to be high, the crossed roller slewing bearing can be selected.

3. Working temperature

In general, the operating temperature of the slewing ring bearing mainly depends on the sealing material, grease, isolation block, and the operating temperature range is -25 to +70 °C.

4. Running speed

The four-point contact ball slewing ring bearing has a high limit speed, and the friction force generated is smaller than that of the cylindrical roller slewing ring.

5. Sealing conditions

Qualified seals used in slewing bearings can provide good moisture and pollution protection, and ensure sufficient quality in the bearing, which can prolong the service life of the bearing, so the seal is very important for the performance of the slewing bearing.

6. Vibration

For vibration applications, both four-point contact ball slewing rings and crossed cylindrical roller slewing rings are suitable.

The above article describes the classification of slewing ring bearings in detail, and the factors that need to be considered when choosing the type. I hope it can help you. If you have other questions about slewing ring bearings, you can leave us a message~

What are the common load forms of slewing bearings?

We all know that no matter what the bearing is, it will bear a certain load, and the slewing bearing is no exception. So, what is the load of the slewing bearing? What are the common load forms of slewing bearings? Today, the editor will introduce to you the common load forms of slewing bearings, hoping to help you understand more about slewing bearings.

1. What is the slewing bearing load?

It is only said that the load refers to the external force and other factors that cause the internal force and deformation of the structure or component, and the load of the bearing refers to the limit force that the bearing can bear under the action of the internal force and external force. The load is also called the load, which is used as a slewing bearing. Said that the types of loads it can bear include traditional radial and bearing loads, working loads, temperature loads, etc. The following editor will introduce these loads to you respectively.

2. Common load forms of slewing bearings

Slewing Bearings

(1) Radial and axial loads

In a rolling bearing, when the total plastic deformation is less than one ten thousandth of the diameter of the rolling element at the contact point between the rolling element and the raceway that bears a relatively large load, it has little effect on the normal operation of the bearing.

The static load capacity of the bearing determined under this plastic deformation condition is called the rated static load. The rated static load is determined under the assumed load conditions. For radial bearings, the rated static load refers to the radial load, and the radial load Thrust bearing (angular contact ball bearing) refers to the radial component of the load that loads the half-ring raceway in the bearing, and for a thrust bearing, it refers to the central axial load. The basic static load rating and basic static load rating of the bearing refer to the maximum load that the bearing can bear when it is static or rotating.

(2) Working load

The working load means that the slewing bearing device bears the weight of the machine itself and the weight of the increased weight during work, and then slowly transfers the total weight to the slewing bearing device. Ensure that the slewing bearing device has a steady stream of power and operates normally.

(3) Temperature load

When the mechanical equipment is working, it will generate a certain temperature, and all these temperatures must be absorbed by the slewing bearing device, so that the slewing bearing can withstand all the temperatures. The force of the slewing bearing against temperature is what we call the temperature load.

(4) Wind load

When the machine works in the open air, it is necessary to consider the effect of wind load, including wind direction, rain, thunderstorm weather and so on. The above is only a part of the load that the slewing bearing device bears. In fact, the slewing bearing device needs to bear more load in order to meet all the weight and load of the machine in work. Under normal circumstances, the slewing bearing itself is equipped with mounting holes, lubricating oil and sealing devices, which can meet the different needs of various types of hosts working under various working conditions.

slewing bearings

(5) Risk load

That is, the unexpected and unpredictable loads, cross forces, risk forces, unexpected violence, etc. that the slewing bearings and slewing bearings bear. Therefore, the selection of the slewing bearing will have the existence of a safety factor to ensure foolproof.

(6) Dynamic load

Dynamic loads include inertial loads, vibration loads and shock loads. The mass force caused by the change in the magnitude and direction of the movement speed becomes the inertial force. These are all part of the dynamic load.

(7) Static load

The load capacity of the bearing at rest is determined by the allowable amount of plastic deformation. Plastic deformation in rolling bearings is unavoidable. If the allowable amount of plastic deformation is limited, the static load capacity of the bearing is also small; if the allowable plastic deformation is large, the pits generated on the raceway will increase the noise and vibration of the bearing during operation, and improve the running accuracy. Reduced, affecting the normal operation of the bearing.

The above is what the common load forms of slewing bearings are summarized by Xiaobian for you, and all the types of loads that slewing bearings can withstand. We understand that the common load types of slewing bearings include traditional radial load and axial load, working load , temperature load, wind load, risk load, dynamic load, static load, etc. Because of the existence of these loads, the slewing bearing can operate safely and ensure the normal operation of the equipment.

Four forms and maintenance skills of slewing bearing raceway failure

The failure of the bearing raceway will directly lead to the overall failure of the slewing bearing. The life of the slewing bearing raceway is affected by its own quality and later maintenance. Therefore, the daily maintenance of the slewing bearing raceway is very important.

When we find that the raceway fails, there are mostly five manifestations: large bearing clearance, oil leakage from the bearing, stuck running of the bearing, abnormal noise from the bearing, iron powder or iron lumps in the slewing bearing raceway. The four forms of track failure will be briefly introduced to you, and at the same time, I will share with you some daily maintenance skills for the slewing bearing raceway.

Four forms of slewing bearing raceway failure

Slewing Bearings

1. Surface peeling

The main reason for the surface peeling of the slewing bearing raceway is that the hardened layer is too thin and the hardness transition zone is too narrow. There are many reasons for contact fatigue failure, which may be excessive axial load, poor lubrication, poor alignment, excessive impact load during installation, etc., which can cause contact fatigue failure of bearings. Intermediate frequency equipment with lower frequencies should be used to deepen the hardened layer. At the same time, the quenched and tempered hardness should be appropriately increased to reduce the hardness gradient of the raceway section.

2. Corrosion pitting

The chemical or electrochemical reaction occurs between the metal surface and the environmental medium, and the surface damage caused by it is called corrosion failure. Corrosion is divided into three categories: chemical corrosion, electrical corrosion, and fretting corrosion, mainly manifested as the corrosion of the inner bearing surface of the bearing. The intrusion of corrosive medium, condensation of moisture in the air, sparks generated when the current passes, fretting and other factors can cause the corrosion failure of the slewing bearing raceway.

Pitting corrosion mainly occurs on the raceway treated with quenching and tempering. The reasons are low hardness and unreasonable design of raceway structure, causing sliding friction and contact fatigue stress, resulting in defects such as pitting and indentation.

3. Plastic deformation

Under the action of external force, the local plastic flow or overall deformation of the surface of the part, such as the deformation of the raceway or the distortion and warpage of the cage, etc., cause the failure of the slewing bearing to not work properly, which is called plastic deformation failure. This situation often occurs after a period of use. At this time, most of the high-hardness layer has been worn, and after the load and friction force suddenly increase, the metal inside and outside the raceway is squeezed into piles. Steel grades with high hardenability should be used instead.

4. Wear

The relative sliding friction between the surfaces leads to the continuous wear and tear of the metal on the working surface, resulting in failure. Wear will increase the fit clearance and change the shape of the raceway surface, and also affect the lubricating function of the lubricant, causing the bearing to lose its rotational accuracy or even fail to operate normally. Raceway wear is divided into normal wear and abnormal wear.

Normal wear and tear is the process of gradually increasing the gap in the whole life cycle to complete the task of the whole life cycle. Abnormal wear has manufacturing problems, standard parts problems, grease problems and post-maintenance problems.

The post-maintenance skills of the slewing bearing raceway

slewing bearing

1. Slewing bearing raceway lubrication

(1) Selection of grease: For the slewing bearing, grease is equivalent to the relationship between fish and water. If the best quality product does not pay attention to the lubrication of the raceway, it is the state when the fish leaves.

The general grease used for slewing bearings used in general construction machinery is usually 2# or 3# lithium-based grease. It is recommended to use lithium molybdenum disulfide grease for heavy-duty products, and low-temperature lubricating grease is used in severe cold areas. Grease, in high temperature environment is high temperature grease, the grease used in wind power slewing bearing is usually NLGI1.5 to 2 grade lithium-based, complex lithium-based, calcium grease, the choice of different environmental greases are differentiated .

(2) Grease filling frequency: In dry and clean occasions, it is recommended to refill once every 500 hours of operation, and once every 250 hours of operation for construction machinery in outdoor environments, and once every 50 to 100 hours of operation in harsh environments. In some closed dust environments, continuous filling is recommended.

Some equipment is going to be stopped for a long time. It is recommended to fill up the grease when stopping the operation, and squeeze out the old grease. When re-operating, it is recommended to refill the grease again. At this time, only a small amount of lithium base grease is needed to be replenished. Newly purchased equipment is recommended to be filled with grease.

(3) Grease filling method: one is manual filling, and the other is automatic filling equipment on the equipment, which adopts automatic filling.

2. Maintenance of slewing bearing sealing ring

The sealing ring is the first wall of the slewing bearing, which can be used to prevent foreign objects such as sand outside the slewing bearing from entering the raceway, causing wear of the rolling elements and the raceway. If the sealing ring is damaged, the problem is the leakage of grease. And dust and dirt enter the raceway, resulting in the rapid wear and failure of the raceway.

In terms of the maintenance of the sealing ring, firstly, after the main engine is working in acid and alkali occasions, it should be cleaned in time; secondly, check whether the lower sealing ring is damaged or fall off each time oil is injected; thirdly, check whether the sealing ring is worn at least once every three months. Seriously, whether there is an oil leak.

If there are any of the above three phenomena, it is recommended to replace the sealing ring immediately. It is not recommended to replace the sealing ring personally. You should ask a technician to replace it, so as to ensure the service life of the sealing ring.

The failure manifestations and causes of the slewing bearing raceway have been introduced in detail above. We do a good job in the daily maintenance of the slewing bearing raceway in daily use, which can also prolong the service life of the bearing.

What material is good for the slewing bearing? how to choose

The material of the slewing bearing directly determines the performance and service life of the bearing. At present, the main structure of the bearing on the market is mostly made of bearing steel, which has the characteristics of corrosion resistance and stability. Of course, in addition to bearing steel, there are also metal materials such as aluminum alloy or copper. In addition, the sealing ring and cage of the bearing may be different from the material of the bearing body. The following slewing bearing manufacturers will share what materials are good for the slewing bearing.

What material is good for the slewing bearing

slewing bearing

1. Ring and rolling element material

In the early stage, 45# steel was used for the slewing bearing, which was gradually eliminated in the later stage due to poor modulation performance. At present, in the more common processing technology, the rolling elements of the slewing bearing are made of carbon-chromium bearing steel which is hardened as a whole. The grade is made of GCr15 or GCr15SiMn steel; the ring of the slewing bearing is made of surface hardened steel, and is made of 50Mn steel if there is no special requirement. But sometimes customers also choose to customize other grades such as 42CrMo, 40Cr, etc. The following introduces the characteristics of these grades of steel.

(1) 42CrMo is a high carbon steel with good quenching and tempering properties and quenching properties, and is an ideal material for slewing bearings.

(2) 50Mn has good hardenability and is also an excellent choice for slewing bearings.

(3) 40Cr is also good in terms of mechanical properties, and is still in the stage of exploration and practice.

(4) GCr15 small slewing bearing can be selected, but milling and drilling in the process are troublesome due to full quenching, so it is generally not recommended.

2. Cage material

Cages for slewing bearings have integral, segmented, spacer block and other structural forms. The types of cage materials are: mild steel stainless steel cage, bakelite/plastic (nylon) cage, brass/bronze/aluminum alloy cage, etc. The spacer block type is made of polyamide 1010 resin, ZL102 cast aluminum alloy, etc. .

The characteristics of bearing cages of various materials are as follows:

(1) Steel bearing cage: It is often made of 08 and 10 carbon steel sheets by cold stamping. Commonly used steel cage materials are 20, 30, 45, 0Cr18Ni9, 1Cr18Ni9Ti, 40CrNiMo, ML15, ML20, etc., which are commonly used in bearing cages, with solid and durable performance.

(2) Non-ferrous metal bearing cage: different from steel, non-ferrous metal has its special properties. For example, aluminum alloy has the characteristics of low density, good thermal conductivity and good corrosion resistance; copper alloy has good thermal conductivity, small friction coefficient, It has the characteristics of good formability and high operating temperature; zinc-aluminum alloy has the advantages of low cost, low density and excellent performance.

(3) Non-metallic cage: Non-metallic cage materials mainly include polymers and their composite materials, including nylon, phenolic tape, PTFE, etc. The polymer material has good strength and elasticity matching, which can effectively reduce the heating and wear of the bearing.

3. Sealing ring material

The materials used for bearing seals are generally commonly used sealing materials, mainly including: nitrile rubber, silicone rubber, fluorine rubber, EPDM rubber, fluorobutadiene rubber, PTFE, polyurethane rubber, acrylic rubber, Anaerobic glue, etc.

The material of the sealing ring of the slewing bearing is made of oil-resistant rubber or NBR rubber. Hydrogenated nitrile rubber has better oil resistance than nitrile rubber, but if you are not too demanding on oil resistance, use nitrile rubber, because hydrogenated nitrile rubber is relatively expensive. Nitrile rubber also has a certain acid and alkali resistance. However, if the requirements for oil resistance and acid and alkali resistance are higher, silica gel should be selected, but its price is higher.

Slewing Bearings

How to choose the material of the slewing bearing

The editor analyzes the materials used in the slewing bearing under the premise of the current production technology level of the slewing bearing.

1. Rolling body material: The rolling body is generally made of GCr15SiMn.

2. Ring material: 50Mn is used for the slewing bearing ring, but sometimes 42CrMo is used to meet the needs of the host in special applications.

3. Cage material: There are different types of cages such as integral type, segment type, isolation block type and so on. The integral or segmented retainer is made of 20# steel or ZL102 cast aluminum alloy. The spacer block retainer adopts polyamide 1010 resin, ZL102 cast aluminum alloy or QA110-3-1.5 aluminum bronze.

4. Sealing ring material: Oil-resistant rubber, fluorine-containing rubber, oil-resistant nitrile rubber sealing ring should be selected for the slewing bearing. The clearance of the slewing bearing is mainly used to compensate the manufacturing error and installation error of the slewing bearing supporting parts and the relevant host assembly parts to ensure the normal use of the bearing. According to the structure type/tolerance class of the slewing bearing and the pitch circle diameter of the rolling element group, the clearance value or the pre-interference of the slewing bearing.

The above is the introduction of the slewing bearing manufacturer on what material is good for the slewing bearing. The bearing materials mentioned by the editor of Longda are suitable for the slewing bearing, but the specific use environment and performance requirements may have different requirements for the bearing material. , please choose according to the actual situation.

What are the factors that affect the service life of the slewing bearing

There are many factors that affect the life of the slewing bearing. Different working conditions, different materials, and different bearing types will affect the service life of the bearing. For this reason, the life is not a standardized number but depends on the materials, processes, and production levels during production. , as well as the use method during use, maintenance and lubrication conditions and other factors are comprehensively determined.

How long is the service life of the slewing bearing in general

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 also different for different types of bearings.

Like ordinary bearings, the service life of the bearing refers to the failure of use, such as pitting, spalling, etc., which cannot work normally. For spindle bearings, precision bearings, etc., which require high precision, when the running accuracy of the bearing fails to meet the requirements, it will fail, but it is far from the standard of failure of ordinary bearings. So this is also the reason for the different service life of the slewing bearing.

Factors affecting the service life of slewing bearings

Slewing Bearings

1. Manufacturing factors

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

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

(3) Manufacturing: In the process of producing slewing bearings, the hardness of bearing parts, bearing metallographic structure, surface burns, bumps and 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, and the impact in the manufacturing process is similar to the congenital quality problem. The bearing with defects manufactured under the same working conditions has a shorter life than the standard and qualified bearing.

slewing bearings

2. Use factors

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

(2) Assembly: the installation accuracy of the bearing, the degree of fit between the bearing shaft and the seat hole, the selection of each part, size, shape and position accuracy, the selection of assembly tools, and the cleanliness of the installation. Whether impurities are 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 will affect the service life of the bearing. If the bearing is used in a harsh environment or in a high temperature, high heat, low temperature and cold environment, it may affect the performance and performance of the bearing. The service life has a certain impact.

(4) Load: Each bearing has a rated load during production, and there is a range for the load that the bearing bears during operation, that is, the stress condition. If it exceeds this range for long-term overload operation, it may cause serious damage to the performance of the bearing. influence, which in turn affects the service life.

(5) Lubrication: Bearing lubrication is a key factor to reduce the friction between the various parts of the bearing and reduce the occurrence of damage and deformation. For this reason, whether the bearing lubrication is appropriate, timely and reasonable will have a certain impact on the service life of the bearing.

The above is my answer about how long the service life of slewing bearings is generally. In fact, if you want to extend the service life of the bearing, you only need to do the correct selection and assembly, maintain a good working environment, and use the correct maintenance and lubricating oil. Supplementation can increase the service life of the bearing

How many degrees can the slewing bearing temperature generally not exceed? Solutions for overheating

The temperature of the slewing bearing directly reflects whether the bearing is running normally. If the bearing temperature is too high, it may directly reflect that there may be some kind of failure in the bearing, which directly affects the performance of the machine. So how many degrees can the slewing bearing temperature generally not exceed?

Under normal circumstances, the temperature of the slewing bearing should not exceed 70℃, because the allowable temperature of the lubricating grease of the slewing bearing should be less than 80℃. Let’s take a look at the normal temperature range of the slewing bearing and how to solve the problem if the temperature is too high.

slewing bearing

1. The normal range of slewing bearing temperature

The temperature of the slewing bearing is mainly limited by the heat-resistant temperature of the bearing steel, cage, sealing material and lubricant, and in general, the working temperature of the slewing bearing should not be higher than 95 ℃. The aforementioned slewing bearing temperature should not exceed 70°C is calculated based on the grease life. If the operating temperature increases by 15°C, the grease life will be reduced by half. Among the heat-resistant temperature limits of several materials that affect the temperature of the slewing bearing, the heat-resistant temperature of the grease is lower, so this is the upper limit.

The normal working temperature that ordinary bearings can withstand is between 40 degrees Celsius and 70 degrees Celsius, but the ideal working temperature of slewing bearings should be in the range of 40-60 degrees Celsius. The slewing bearing used in the low temperature environment can be used in the vacuum environment. The selection of the low temperature bearing does not affect the working performance of the bearing, and it can also be used normally at minus 60 ℃.

Surface temperature of slewing bearing: When the bearing is running under the specified working conditions, the temperature of the outer surface of the built-in bearing should not be higher than the temperature of the conveying medium by 20℃, and the upper limit of the temperature should not be higher than 80℃. The temperature rise of the outer surface of the externally mounted bearing should not be higher than the ambient temperature by 40°C. The temperature is not higher than 80℃.

The ambient temperature of the turntable: the temperature rise of the bearing shall not exceed the ambient temperature of 35°C, and the upper limit of the temperature shall not exceed 75°C.

After understanding how many degrees the slewing bearing temperature cannot generally exceed, let’s take a look at how we can solve the problem when the slewing bearing temperature is too high.

Slewing Bearings

2. The solution to the high temperature of the slewing bearing

A high temperature often indicates that the bearing is in an abnormal state. High temperatures are also detrimental to bearing lubricants. Sometimes bearing overheating can be attributed to the lubricant in the bearing. If the bearing is continuously rotated for a long time at a temperature exceeding 125°C, the service life of the bearing will be reduced. Factors that cause high temperature bearings include: lack of lubrication or too much lubrication, lubricants. There are impurities inside, the load is too large, the bearing ring is damaged, the clearance is insufficient, and the high friction caused by the oil seal, etc. The solution to the high temperature of the slewing bearing:

(1) Adjust the amount of grease injected

Too much or too little grease will lead to abnormal bearing temperature. Too little bearing grease will not be able to lubricate the bearing, which will cause internal wear of the bearing and cause temperature rise. At the same time, too much bearing grease will also cause abnormal heating of the bearing. Therefore, the injection amount of bearing grease should be adjusted.

(2) Replace the grease

The mixing of different types of grease may cause the grease to deteriorate and agglomerate, which will affect the lubrication effect and cause the bearing to heat up. If the grease is polluted by external dust, it may also destroy the bearing lubrication and cause the temperature to rise. The suitable bearing grease should be replaced in time. , and do a good job of bearing moisture-proof and dust-proof measures.

(3) Overhaul the cooling system

If the pipeline of the bearing is blocked, the oil inlet temperature and return water temperature exceed the standard, or the cooler is not suitable for the cooling effect, the bearing temperature will be too high. At this time, it should be replaced in time or a new cooler should be installed in parallel. The axial flow induced draft fan should also check the insulation and sealing of the core cylinder.

(4) Check the coupling

If none of the above problems exist, the coupling needs to be checked. The thermal expansion of the equipment during operation should also be considered when aligning the axial-flow induced draft fan and the hydraulic coupler. The impeller side of the induced draft fan expands due to heat, and the bearing box rises; during the operation of the hydraulic coupling, the temperature rises, the bearing box expands, and the bearing rises, so the motor should be higher when aligning, and the size of the reserved amount depends on the characteristics of the equipment and Depends on the operating temperature parameters.

The above is the reason why the bearing temperature is too high. By measuring the bearing temperature, it can also help us to find out the possible problems of the bearing in time. Therefore, it is necessary to continuously detect the bearing temperature, whether it is to measure the bearing itself or other key parts. If the operating conditions do not change, all temperature changes can indicate a failure.