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

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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

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

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

Type of annealing process for slewing bearing


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1. Recrystallization annealing

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

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

2. Uniform annealing

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

3. Incomplete annealing

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

4. Stress relief annealing

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

5. Isothermal annealing

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

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

6. Spheroidizing annealing

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

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

7. Recrystallization annealing

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

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

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

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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.

Spur Gear Drive

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.

Slewing Drive

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.