Bearing Knowledge - LDB

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

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

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

March 8, 2022/in /by 管理

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

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.

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

March 2, 2022/in /by 管理

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

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.

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

What is the reason for the high noise of spur gear drive?

February 21, 2022/in Spur Gear Drive Knowledge, Spur Gear Drive Knowledge /by 管理

In addition to running accuracy, load capacity and fatigue life, noise is also an important indicator of the performance of a spur gear drive. Noise not only affects the operating environment of the equipment, but also affects the gear transmission accuracy and the overall operation and transmission of spur gear drives. With the successive issuance of ISO14000 and ISO18000 standards, controlling its transmission noise becomes more and more important.

The reason for the high noise of spur gear drive

1. Influence of gear accuracy: Gear accuracy is often designed with economic benefits as the basis, ignoring the impact of accuracy on drive noise and backlash. When the gear accuracy cannot be reached, it will increase the operating noise.

2. Influence of gear width: Under the condition of constant torque, the noise curve gradient of large tooth width is lower than that of small tooth width, and the noise of small tooth width is relatively large.

3. Influence of tooth pitch and pressure angle: Small tooth pitch can contact more gears at the same time, the overlap of gears increases, and the noise is larger.

4. Influence of gear displacement coefficient: When the gear transmission performance is improved, the bearing capacity, the displacement coefficient, the central moment, etc. are not suitable for operation, it is easy to generate noise.

5. Speed control: The noise of the spur gear drive is also different at different speeds. With the increase of the speed, the noise of the drive will also increase.

6. Influence of dynamic balance: Misalignment of assembly will lead to unbalanced operation of the shaft system, and in the state of semi-loose and semi-tight gear meshing, it will lead to aggravation of driving noise, and unbalanced gear assembly will affect the accuracy of the transmission system.

7. Loose or damaged parts: Looseness of individual parts during installation will lead to inaccurate positioning of the system, and abnormal meshing will cause shaft movement to generate vibration and noise. Damage to the transmission parts will also lead to inaccurate or unstable movement of the system, resulting in unbalanced moving parts and vibration and noise during high-speed movement.

8. Improper use or maintenance: Dirty impurities enter the drive and cause wear and tear, causing malfunction noise or improper lubrication, causing wear and tear to increase noise. After understanding why the spur gear drive is noisy, let’s take a look at the specific solutions.

Spur gear drive operation noise solution

1. Improve the precision of the drive gear and reduce the transmission error and equipment noise. Control tooth profile error. Reducing the roughness of the tooth surface can reduce the noise emission.

2. When the drive transmission space allows, increase the gear width, reduce the unit load under constant torque, reduce gear winding and reduce noise excitation, while increasing the gear width can also increase the bearing capacity of the gear and improve the bearing torque of the reducer .

3. The correct and reasonable selection of the displacement coefficient can not only make up for the central moment, avoid gear undercut, ensure that the concentric condition is met, improve the transmission performance of the gear, increase its bearing capacity and the service life of the gear, and control the operating noise.

4. Increase the hardness of the spur gear drive gear tooth surface. The high hardness of the gear tooth surface can reduce the possibility of gear deformation, and at the same time, it has a certain effect on reducing the driving noise.

5. Do a good job of shock absorption between the equipment and the drive to avoid resonance and noise between the fuselage and the foundation support and connecting parts. High toughness, high damping base materials can be selected to reduce noise and vibration.

6. Regularly repair the equipment, tighten the parts, find and repair the faulty parts in time, and replace the parts that cannot be repaired in time to stabilize the equipment and reduce the noise level.

7. Supplement lubricating oil in time, choose suitable lubricating oil, avoid equipment heating, wear and other failures caused by insufficient lubrication, and cause failure problems such as increased noise.

8. Keep the internal parts of the drive clean and prevent impurities from entering the spur gear drive and affecting the normal operation of the transmission system.

The above is all about the reasons for the loud operating noise of the spur gear reducer, and also includes specific solutions. There may be many reasons for the noise during the operation of the reducer. It should be noted that the influence of various aspects of the rotary reducer is from Reduce the impact of noise in many ways.

Will the slewing drive raceway be damaged? Causes of raceway damage and preventive measures

February 14, 2022/in Slewing Drive Knowledge /by 管理

The main structure of the slewing reducer is a structure in which the slewing bearing is used as a transmission follower and a mechanism attachment, and the slewing bearing itself is used to cooperate with the driving power source and the main transmission parts to complete the rotation, deceleration and driving. The slewing bearing is still one of the more critical components, so will the raceway of the slewing drive be damaged? Below, Xiaobian will give you a detailed introduction.

Will the raceway of the slewing drive be damaged?

Will be damaged. As an important component used by many construction machinery, the slewing reducer will inevitably have problems such as wear and fatigue damage during daily use. Because of its slewing structure, it is inevitable that the raceway will be damaged during work. . In addition to the insufficient rigidity of the raw materials in the manufacturing process, the reasons for the damage to the raceway may include unreasonable structural design and insufficient manufacturing accuracy of the reducer. Let’s take a look at it in detail:

Causes of damage to the slewing drive raceway

1. Heat treatment process

The processing quality of the rotary reducer itself is related to the manufacturing accuracy, heat treatment state, and axial clearance. What we usually ignore is the influence of the heat treatment state. In addition to the external force, the most important thing for the damage of the raceway is the depression and cracks on the surface of the raceway during its production. This is related to the hardness of the raceway surface and the hardness of the hardened layer and the core, and these factors are determined in the heat treatment process. For this reason, the depth of the hardened layer on the raceway surface is insufficient and the hardness of the core is low. A more critical factor in its raceway damage.

2. Structural rigidity of turntable

The key component that transmits various loads between the turntable and the chassis when driven by gears. The rigidity of the turntable itself is not large. It mainly depends on the rigidity of the chassis and the structure of the turntable that supports it. When the structural rigidity of the turntable is not enough, the turntable under large eccentric loads The deformation of the bottom plate connected to the slewing mechanism is more serious, which in turn causes the equipment load to concentrate on a small part of the rollers, thereby increasing the pressure on a single roller, resulting in the contacting raceway also bearing a large contact stress, which It is also one of the reasons for the damage to the raceway.

Preventive measures for rotary drive raceway

1. Pay attention to the rated load: the rotary drive should not be overloaded;

2. Correct model selection: Select the appropriate slewing drive according to your needs. When purchasing the slewing drive, you must strictly calculate the various parameters of the slewing drive, and select the turntable bearing that suits the actual needs. road damage;

3. Pay attention to maintenance: maintain regular maintenance, and regularly add lubricating oil to the rotary drive. Only through reasonable maintenance and maintenance can we ensure that the slewing drive raceway is not easily damaged and prolong the service life of the slewing drive.

The above is the answer to the question about whether the raceway of the slewing drive will be damaged. It includes the reasons for the damage of the raceway and preventive measures. In fact, whether it is the drive device or the bearing itself, as mechanical parts, there is a certain fatigue limit, which should be based on Use the guide reasonably and maintain it properly, so as to better play the role and value of the equipment.

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

February 8, 2022/in Slewing Bearing Knowledge, Slewing Bearing Knowledge, Slewing Bearing Knowledge, Slewing Bearing Knowledge, Slewing Bearing Knowledge, Slewing Bearing Knowledge /by 管理

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.

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.

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?

January 18, 2022/in /by 管理

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

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.

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

January 12, 2022/in /by 管理

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.

Why should slewing bearings be annealed?

The purpose of slewing bearing annealing may be for three reasons:

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 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.

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

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.

How is the spur gear drive packaged? Packaging method and function

January 4, 2022/in /by 管理

Spur gear drive, as a general-purpose reducer that integrates the functions of rotation, deceleration, and drive, can use the transmission structure to achieve a transmission with a large transmission ratio, which reduces the failure rate of the host to a certain extent. It is usually modular and highly integrated. After the assembly is completed, special attention should be paid to storage and transportation of this device to avoid impacts or other conditions that affect its function. For this reason, the product should be packaged.

How is the spur gear drive packaged

1. Packaging method

(1) Cleaning and assembly: clean each part after passing the inspection to remove dirt and impurities on the surface, and then assemble the parts and assemble them into a complete rotary drive.

(2) Lubrication: Inject grease into the rotary drive through the oil injection hole, and wipe the surface after the entire rotary drive is qualified to ensure the smoothness of the surface.

(3) Anti-rust: Paint anti-rust oil on the outer surface of the slewing drive, especially the slewing bearing as the main transmission component, should be fully lubricated and anti-rust work to prevent rust during storage or transportation. Of course, during the production process, the manufacturer will also spray and other special anti-rust treatments on the spur drive housing. After the anti-rust oil is applied, it should be packed in time to isolate the air to achieve a better anti-rust effect.

(4) Outer packaging: put the packed straight gear reducer in a wooden box, pay attention to the protection of the inner wall of the wooden box, generally put a layer of pearl cotton on the bottom of the box to prevent the rotary drive from scratching in the wooden box, and use pearl cotton around Separate the wooden box from the drive and try to fill the gap to avoid shaking and bumping during transportation. If you want to stack it, you need to use a wooden strip to isolate and support between the two rotary drives to prevent the upper product from compressing the lower product. In addition, the upper layer of the wooden box should be laid with pearl cotton to prevent the product from being scratched when the lid is opened and nailed. At the same time, fix the outer packaging and prevent moisture.

2. Matters needing attention

(1) Choose suitable lubricating grease and anti-rust oil according to the characteristics of the product. It should be appropriate, not too much or too little.

(2) Avoid stacking multiple products if possible, and protect a single product to avoid damage such as stacking collisions, extrusion deformation, etc.

(3) A suitable packing box should be customized according to the size of the product, which can greatly reduce the damage caused by extrusion or shaking due to the mismatch of the box and the product. At the same time, pay attention to whether the packing box is strong.

(4) During the transportation process, attention should be paid to moisture-proof and stable transportation, to avoid the impact of external environment such as bumping into water.

The role of spur gear drive packaging

1. Product protection: Tight packaging can better protect the products. The spur gear drives produced are all qualified products that have been inspected. However, if they are transported or stored, they will inevitably experience some violent transportation or accidents. If the packaging is not In place, it may cause damage to the product. In order to deliver the product to the customer intact, tight packaging is necessary.

2. Convenient storage: Sometimes customers don’t use the spur gear drive immediately after purchasing it, and may need to be stored for a period of time, so the anti-rust treatment of the product packaging box is particularly important.

3. Transportation protection: It is inevitable that the product will be directly loaded and unloaded by forklift during transportation, and bumps will inevitably occur. The use of strong outer packaging can play a certain protective effect and play a pre-protective role against some uncontrollable conditions during transportation.

4. Manufacturer’s information display: The outer packaging is not only to protect the product but also to display the company’s image. Good standardized packaging reflects the manufacturer’s standardized production and good production management system, and is also a display of the manufacturer’s strength. At the same time, product information such as the product model, inspection certificate, and instructions for use will also be displayed on the outer packaging, so that the process of receiving and transportation can be more clearly and intuitively distinguished.

Causes and Preventive Measures of Quenching Soft Spots of Slewing Bearings

November 22, 2021/in /by 管理

In the production process of the slewing bearing, the hardness of the steel ring is locally lower after the quenching process, which usually occurs after the quenching. This situation is called the quenching soft point, and when the pieces appear, it is called the quenching soft belt. The location where the soft spot occurs is that the bearing has low hardness, which will affect the quality of subsequent grinding. Fatigue damage is also prone to occur during use, which affects the service life of the bearing. So what is the reason for the quenched soft spot of the slewing ring?

Reasons for the soft spot of slewing bearing quenching

1. Decarburization: When the metal is heated in the furnace or the atmosphere in the furnace is not good, it is easy to cause decarburization. The process of decarburization is that the carbon element in the bearing steel reacts with clear or oxygen at high temperature to generate methane or carbon monoxide. This situation will reduce the surface carbon content and the hardness to meet the requirements.

2. Insufficient temperature: Insufficient heating temperature and insufficient heat preservation make the bearing material matrix not fully austenitized. After quenching, it cannot completely transform into martensite, resulting in local soft spots. In addition, the local cooling rate is too low, the bearing surface has bubbles or contaminants, or the critical cooling rate is not reached in the close contact of the workpiece, and it cannot all become martensitic.

3. Uneven steel structure: If the original structure of the workpiece material used in the production of the bearing is not uniform, such as carbide segregation, carbide aggregation, etc., it will affect the quenching effect of the bearing.

4. Inductor problem: The structure of the inductor and the positioning fixture during quenching are not good, which affects the heating effect, or the center line of the spray cooling hole on the inductor and the quenched surface are perpendicular or angled improperly, resulting in uneven heating, heating, and cooling. The situation arises. In addition, the unequal spacing between the bearing and the inductor can also cause uneven heating.

5. Poor hardenability: The material of the slewing bearing is made of steel with poor hardenability, such as carbon steel. However, if the cross section of the workpiece is large or the thickness difference is large, soft spots may appear at the large cross section.

6. Poor quenching medium: the cooling rate of the quenching medium is low or too old will cause soft spots in the bearing.

After understanding the reasons for the soft spots or soft bands of the slewing bearing, the method to improve the existing soft spots can be through annealing, normalizing, and high temperature tempering, followed by re-quenching according to the normal process, or re-quenching after recarburizing. Or, after quenching, the hardness can be improved by cold treatment, and then tempering treatment will try to solve it. So how do we avoid the recurrence of quenched soft spots in the subsequent bearing production and processing process?

Measures to prevent the occurrence of soft belts on slewing bearings

1. Reasonable material selection: pre-homogenize the defective steel before quenching to remove the problems of carbide segregation and aggregation.

2. Control the heating temperature and time: For insufficient austenitization due to insufficient heating temperature and time, we need to select the appropriate heating temperature, heating time, and holding time for the steam during processing.

3. Reasonable selection of quenching medium: strengthen the relative movement between the workpiece and the medium, or stir the medium to keep the quenching medium clean. Quenching of carbon steel in salt water can effectively prevent the generation of soft spots.

4. Strictly follow the process: perform the quenching operation correctly, correctly control the pre-cooling time, the residence time in water or brine during quenching, the residence time in water or brine during dual-medium quenching, and the residence time of graded quenching.

The above is the reason for the soft spot of slewing bearing quenched by Lunda editor and the measures to prevent the soft band. I hope it can be helpful to everyone. The soft spots of the bearing have an impact on the later grinding process and performance of the bearing. I hope everyone will pay attention to it.