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.

What are the surface treatment processes for slewing bearing fasteners? How to choose?

We all know that slewing bearings also need fasteners. Fasteners are widely used mechanical parts for connecting and fixing mechanical equipment and various parts. They are suitable for all walks of life. Due to their standardization, series, and degree of generalization higher, we also call a type of fasteners that meet relevant standards as standard fasteners, also called standard parts. Let’s take a look at the surface treatment process and commonly used materials of slewing bearing fasteners.

Surface treatment process of slewing bearing fasteners

Slewing Bearings

1. Electro-galvanized

The surface of electro-galvanized is black and military green. It is a commonly used coating for commercial fasteners. It is cheap and prone to hydrogen embrittlement during the production process. Generally, bolts above grade 10.9 are generally not galvanized. The consistency of the tightening force is poor and unstable, and it is generally not necessary to connect in important parts.

2. Oxidation and blackening

How is the blackening treatment of the slewing bearing made? Blackening + oiling is a very popular coating for industrial fasteners, and the price is cheap. However, the holding time is short, and the neutral salt spray test can only reach 3 to 5 hours in the presence of oil, and it will rust soon if there is no oil. Moreover, the consistency of torque and pre-tightening force of the oxidized black parts is poor. If it needs to be improved, grease can be applied to the inner thread during assembly and then screwed together.

3. Electroplating chrome

Electroplating chrome is relatively stable in the atmosphere, with good wear resistance, high hardness, and not easy to change color. , chrome-plated fasteners will be used only when the strength of stainless steel is not sufficient to meet the fastening needs.

4. Silver plated nickel plated

Silver plating can prevent corrosion and can lubricate fasteners at the same time. Due to the high cost, silver plating is generally only used for nuts, not bolts. Silver is easy to oxidize, so it is easy to lose its luster in the air, but it works at 1600 degrees in Chinese style, so silver-plated parts are often used in high temperature environments.

Nickel-plated fasteners have good anti-corrosion and electrical conductivity, and are often used in locations where electrical conductivity is required, such as the terminal of vehicle batteries.

5. Electroplating cadmium

Cadmium coating has good corrosion resistance, especially in marine atmospheric environment, the corrosion resistance is better than other surface treatments. The cost price is 15-20 times that of electro-galvanizing, and the cost is relatively high. Generally, it is only used in special industries such as oil drilling platforms and fasteners for HNA aircraft, which require high anti-corrosion performance.

6. Zinc

Sherardizing is a solid metallurgical thermal diffusion coating of zinc powder. Its uniformity is good, and a uniform layer can be obtained in the thread and blind hole. The thickness of the coating is 10~110μm, and the error can be controlled within 10%. Its bonding strength with the substrate and anti-corrosion performance are in the zinc coating, and it is pollution-free and harmless during processing.

slewing bearings

How to choose slewing bearing fasteners

As the slewing bearing fasteners used in ordinary equipment, ordinary electro-galvanized and oxidized black treatment can meet the needs; if there are requirements for the hardness and wear resistance of fasteners or working temperature, silver-plated or electro-chromic processes can be selected ; If the working environment humidity is high and the anti-corrosion performance of the fasteners is required, the Dacromet, zinc galvanizing, and cadmium electroplating processes can be selected; if the conductive performance of the fasteners is required, the nickel-plated process fasteners can be selected.

The specific characteristics and advantages of the surface treatment process of the above slewing bearing fasteners have been introduced clearly. You can make a reasonable choice according to the environmental requirements of the adapted machinery and the characteristics of the equipment.

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

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

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?

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?

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.