Detailed bearing steel

      Bearing steel is steel used to make balls, rollers and bearing rings. Bearings are subjected to extreme pressure and friction during operation, so bearing steels are required to have high and uniform hardness and wear resistance, as well as high elastic limits. The uniformity of the chemical composition of the bearing steel, the content and distribution of non-metallic inclusions, the distribution of carbides, etc. are very strict. The bearing steel is also called high carbon steel. The carbon content of Wc is about 1%, and the amount of lanthanum is Wcr. 0.5% - 1.65%.
The physical properties of bearing steel are mainly based on inspection of microstructure, decarburization layer, non-metallic inclusions and low-fold structure. In general, it is delivered by hot rolling annealing and cold drawing annealing. The delivery status should be stated in the contract. The low-magnification of steel must be free of shrinkage, subcutaneous bubbles, white spots and microscopic pores. The center is loose, generally loose, no more than 1.5, and segregation must not exceed 2. The annealed structure of the steel should be a uniformly distributed fine-grained pearlite. Decarburization depth, non-metallic inclusions and carbide non-uniformity shall comply with the relevant national standards.
Bearing steel is divided into six categories: high carbon 硌 bearing steel, 硌 bearing steel, carburized bearing steel, stainless bearing steel, medium and high temperature bearing steel and anti-magnetic bearing steel.
1 high carbon chromium bearing steel, with the symbol "G" in the head of the grade, but does not indicate the carbon content. The chromium content is in parts per thousand and the other alloying elements are expressed as the alloy content of the alloy structural steel. For example, a bearing steel with an average chromium content of 1 □ 50% is indicated by the name “GCr15”.
2 carburized bearing steel, using the alloy structural steel branding method, and the symbol "G" in the head of the brand. For example: "G20 CrNiMo". Premium high quality carburized bearing steel with "A" at the end of the grade. For example: "G20CrNiMoA".
3 high carbon chromium stainless bearing steel and high temperature bearing steel, using stainless steel and heat resistant steel grades, the brand head is not marked with "G". For example: high carbon chromium stainless bearing steel "9Cr18" and high temperature bearing steel "10Cr14Mo".

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How to prevent high voltage motor bearings from being burned

    A thermal power plant is equipped with a motor with a power of 220 kW and a voltage of 6 kV. The shaft end of the motor shaft is a 2322E cylindrical roller bearing, and the non-shaft end is a 6322 deep groove ball bearing. In 2004, when the motor was in operation, the temperature of the bearing at the shaft end was sharply increased, the bearing oil cap was discolored, and the smoke of the burnt smell was accompanied. After the operation of the on-duty personnel stopped the inspection, it was found that the motor shaft extension end bearing burned and was locked with the motor rotor.
    1 Accident investigation

    After the accident, the maintenance personnel conducted a physical examination of the motor and found that:

    (1) The bearing end of the motor shaft is burned, the bearing frame and the roller are worn out seriously, and the outer ring of the bearing turns blue partially;

    (2) The bearing chamber has obvious signs of wear and is accompanied by deep cracks;

    (3) The rotor shaft is combined with the inner and outer oil caps, and there are many deep wear marks;

    (4) The inner and outer oil caps of the motor shaft extension end bearing are burnt.

    After the disintegration inspection, the maintenance record of the motor was also checked, and it was found that the motor had replaced the bearings at both ends two years ago. When the bearing was replaced, it was found that there was a problem with the tolerance of the motor shaft end bearing and the bearing chamber, and the bearing was slightly rounded, but it was not treated. After the replacement of the bearing, the motor was replenished only once in February 2004, and there was no maintenance record.

    2 Cause analysis

    (1) The maintenance personnel did not deal with the defects of the outer circle of the bearing, which caused the bearing to heat up and burn after long-term operation.

    (2) The maintenance personnel failed to timely refuel the motor.

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Matching and preloading of household appliance bearings

Core Tip: The role of pre-tightening Pre-tightening refers to the use of the bearing in the play by changing the relative position of the inner and outer rings before the bearing is loaded. For household appliances bearings, the main pre-tightening
Preloading effect
Preloading refers to the use of the bearing in the play by changing the relative position of the inner and outer rings before the bearing is loaded. For household appliances bearings, the main role of pre-tightening is to improve bearing stiffness and suppress vibration noise.
Preload on the bearing noise
When the bearing is subjected to radial load, due to the radial clearance, only part of the steel ball is subjected to load (ABC in the figure), which is called the bearing area, and the other is called the non-bearing area. During the movement of the steel ball from the D to the D' in the non-bearing zone, the magnitude and direction of the combined force of the self-weight and the centrifugal force of the steel ball constantly change, and the steel balls alternately collide with the inner and outer ring raceways, so that abnormal noise is generated inside the bearing. This abnormal sound can be eliminated by preloading the bearing.
However, if the pre-tightening force is too large, the bearing friction increases, the temperature rises, and the noise life of the bearing decreases. Therefore, it is important to choose a suitable preload.
The structure of NSK common dust cover and sealing ring is shown in the figure below. The dust cover (ZZ) is stamped from a steel plate, and the seal ring is made of rubber covered with steel. Among them, the sealing ring is divided into two types: non-contact type (VV) and contact type (DDU, DDW).

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The characteristics and development history of foreign bearing industry

Core Tip: The development of the world's bearings has gone through three stages, in which it has experienced many difficulties and obstacles, and finally achieved the glory of the bearing industry. The world's bearing industry emerged from the end of the 19th century to the second
The development of the world's bearings has gone through three stages, in which it has experienced many difficulties and obstacles, and finally achieved the glory of the bearing industry.
The world's bearing industry began in the late 19th century to the early 20th century. In 1880, the United Kingdom began to produce bearings. In 1883, Germany established the world's first bearing company (FAG George Shaver). In 1889, the United States opened the ND bearing factory (now the General Motors Bearing Company's new Diocletian Hyde Bearing Division). Other large bearing companies in Europe and the United States basically laid the foundation for today in the early 20th century. After the Japanese bearing industry was formed in Europe and the United States, SKF Sweden provided samples to Japan in 1910, making the "bearing" appear in Japan for the first time alone. Since then, Japan NSK, NTN and other bearing companies have been established in 1914 and 1918. The bearing industry in the third world countries started later, and it is in a relatively backward situation like the entire science and technology and machinery industry.
Generally speaking, the formation and development of the world bearing industry has gone through three stages:
The first phase, the initial stage of the world bearing industry, was from the end of the 19th century to the beginning of the 20th century. At that time, bearing inventions and applications have been around for a while, and the industrial production of bearings has grown from scratch, just starting, quite naive. The main features are:
1. The production scale is extremely small. A large factory has only a dozen to a few hundred people. The daily output is only a few sets to several hundred sets, which belongs to hand workshop production;
2, the equipment is simple, the technology is backward, mostly based on experience;
3, the material is mainly carbon steel, the precision is not high, the price is expensive;
4, very few varieties, the use is very limited. At that time, bearing production technology was only in the hands of a few companies such as the United Kingdom, Germany, Sweden, and the United States.
The second phase, the growth phase of the world's bearing industry, was about the end of the First World War and after the Second World War. The two world wars stimulated the development of military industry, the increasing position of bearings in the military industry, coupled with the rapid development of science and technology, the short-term stability after World War I and the urgent need for arms in World War II, prompting the rapid development of the world bearing industry. The main features are:
1. The scale of production has expanded rapidly and the output has increased rapidly. The annual output of major bearing producing countries exceeds 35 million sets;
2, the production equipment is perfect, the technical means is advanced, and the mass production is generally adopted;
3. The bearing material has been developed to alloy steel such as chrome steel, and the quality of the product has been greatly improved;
4, bearing varieties increased, widely used in automobiles, aircraft, tanks, armored vehicles, machine tools, instruments, meters, sewing machines and many other fields. During this period, people's awareness and attention to bearings rose to an unprecedented height.

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How to look at the quality of a bearing

Core Tips: 1 First look at the materials used in bearing steel, Germany FAG bearings are produced by their own professional steel mills, in terms of hardness and precision are higher than counterfeit FAG bearings. 2 using high investment
1 First look at the materials used in bearing steel, Germany FAG bearings are produced by their own professional steel mills, in terms of hardness and precision are higher than counterfeit FAG bearings.
2 Using high-input marking equipment, in order to establish a corporate brand image and prevent products from being counterfeited, FAG bearing manufacturers have adopted laser marking machines, hoping to establish a corporate image and connect with the international market, while using high input to control products being counterfeited, however, Because the laser marking machine uses computer control, the advantages of easy editing of marking fonts and sizes can not only effectively prevent counterfeiting, but also increase the difficulty for counterfeiters.
3 observation method. The rolling bearing should be observed with the naked eye. The inner and outer raceways should have no peeling marks and severe wear and be in the shape of a circular groove; all the rolling elements should be free of spots, cracks and peeling; the cage should not be loose, damaged or worn. , the gap with the rolling element is not too big.
4 feels. The gap between the inner and outer races of the normal bearing and the rolling elements is 0.005 to 0.010 mm. For rolling bearings that have been used for one stage, when the inner race is pinched with your fingers for axial sway, there should be no obvious squeaking noise.
5 rotation method. Hold the inner race of the bearing with one hand and turn the outer race with the other hand. The bearing should be able to rotate flexibly and the radial sway should not be felt.
6 Of course, it depends on the price. If the price is much lower than normal, it may be a fake proposal. Don't buy it. After all, a penny is worth the price. It is really expensive after all, so the import is very expensive.
During the inspection, the above five empirical methods should be combined to facilitate the correct judgment of the technical state of the rolling bearing. For tapered roller bearings, it should also be observed whether the rolling elements are located in the middle of the outer race. If there is a forward movement, it should not exceed 1.5 mm.
In addition to the above-described discrimination method, it can be distinguished from color and precision. At the same time, you can also refer to other imported bearing brands, iko bearings, Sweden SKF bearings, the United States TIMKEN bearings, Japan NSK bearings, koyo bearings and other methods of distinguishing authenticity.

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