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  •   Rolling of Austenitic Stainless Steel 302 and 304   Due to the contamination of the steel liquid by adding Ti to austenitic stainless steel, TiN and Ti (CN) inclusions are formed in the steel. The production of Ti containing austenitic stainless steel abroad is very small (only 0.5%), so 302 and 304 austenitic stainless steel without Ti has been widely used. 302 steel grade is equivalent to 1Cr18Ni9304 steel grade is equivalent to 0Cr18Ni9.   Rolling characteristics of 302 and 304 stainless steel The thermal conductivity of steel is poor, with a thermal conductivity coefficient equivalent to 27% of low-carbon steel. The heating speed is relatively slow, usually at 130 ℃/h.   At temperatures between 900 and 1250 ℃, there is good plasticity, but the resistance to thermal deformation is high. As the temperature decreases during the processing, the resistance to deformation increases sharply. Therefore, it is necessary to control the final rolling temperature and degree of deformation. Generally, during rolling, to ensure that the final rolling temperature is not lower than 950 ℃, no cooling water is poured on the surface of the rolling rolls, and the relative compression of Z should not exceed 20%, and the average elongation coefficient of Z should not exceed 1.18. α The heating temperature for phases above level 4 should be 1200 ℃ to avoid reducing the plasticity at high temperatures.   The spreading coefficient during the rolling process is almost 1.35-1.5 times that of carbon steel. During the billet opening process, a box square pass system is used. When rolling round steel, a universal pass system is used, and the opening width of each pass is wider than that of general alloy steel. A separate finished pass must be made to obtain steel with accurate dimensions and good surface quality.   Water cooling after rolling or solution treatment at 1050-1100 ℃.   Heating system for austenitic stainless steel ingots and billets In a factory in the former Soviet Union, the heating time for 800kg of 1Cr18Ni9 and 1Cr18Ni9Ti steel ingots was 11.6min/cm, while in another factory, 400kg of steel ingots required 15.3min/cm. Cherianbinsky Steel Plant heated 1200kg of 1C18Ni9 and 1Cr18Ni9Ti steel ingots, with a furnace tail temperature below 800 ℃. Heating Z for a short time of 10 hours resulted in a high temperature of 1260 ℃, and the Z-short time for producing 4-5 steel ingots was controlled at 44-57 minutes.   Small steel ingots with a heating weight of 600-700kg and a large cross-sectional size of 270-305mm are heated in a continuous heating furnace in China. The same heating curve is applied, with a furnace tail temperature below 800 ℃, a high temperature of 1200-1240 ℃, and a short heating…

    Fri March 15 2024
  • Electrolytic polishing process for stainless steel cages

    Abstract: The principle of electric polishing for a stainless steel cage is introduced, and the polishing process conditions and factors affecting polishing quality are analyzed. Actual use shows that this process can meet production needs, and the polished stainless steel cage obtains a uniform bright layer. Keywords: Rolling bearings; Retainer; Stainless steel; Electric polishing   Principles of Electric Polishing The process of putting a workpiece into a specific solution for anodic electrolysis to make the metal surface smooth and produce a metallic luster is called electrolytic polishing or electro polishing. It removes the surface layer generated during the mechanical polishing process and generates a metal oxide layer with high corrosion resistance and reflectivity on the surface, while also reducing surface stress and friction coefficient. Electrolytic polishing is the anodic electrochemical corrosion process on the surface of stainless steel. When using stainless steel workpieces as the anode for electrolysis, the first step is the electrochemical and chemical dissolution of the surface oxide layer and metal, as well as the physical erosion of oxygen bubbles that precipitate on the workpiece, causing the surface layer to detach from the surface of the workpiece and be removed.   Electrochemical polishing may undergo the following reactions: (1) Metal atoms lose electrons and transform into metal ions entering the solution M → M2++2e (2) Formation of oxide film M+H2O → MO+2H++2e (3) Oxygen precipitation 2H2O → O2+4H++4e Anodization of other substances in the solution.   The process of electrolytic polishing can be explained by mucosal theory as follows: when using stainless steel workpieces as anodes for electrolytic polishing, if the dissolution rate of the anode is greater than the diffusion rate of the anodic dissolution products from the anode surface to the depth of the electrolyte, the dissolution products will accumulate near the anode surface. A viscous liquid film with high resistance is formed, and its distribution on the anode surface is uneven. The mucosa at the protrusion is thin and has low electrical resistance. High current density, high oxygen precipitation, easy solution renewal, and fast dissolution rate; The concave mucosa is thick, with high resistance, low current density, and slow dissolution. As the polishing time continues, the protrusions on the anode surface are gradually flattened, making the surface smooth and smooth.   Electrolytic polishing process 2.1 Pre polishing treatment Austenitic stainless steel and martensitic stainless steel are commonly used materials for stainless steel cages. Most austenitic stainless steel cages have relatively clean surfaces and can be polished directly without pre-treatment as needed. Martensitic stainless steel cages require heat treatment such as quenching and tempering, and their surface has a thick layer of oxide skin and oil stains. If not removed, it will seriously affect the polishing quality…

    Fri March 08 2024
  • Blackening Technology of Bearing Stainless Steel

    Abstract: The blackening process of bearing stainless steel 9Cr18 was studied. Adding electrolysis process to the blackened 9Cr18 steel bearings significantly improves their corrosion resistance without reducing their hardness. SEM and AES analysis showed that the corrosion resistance was due to the obvious increase of Cr/Fe ratio in the surface facial mask. Keywords: 9Cr18 bearing stainless steel; Wear resistance; Corrosion resistance; Blackening treatment; electrolysis   Introduction With the rapid development of the world economy, higher requirements have been put forward for the corrosion resistance and surface aesthetics of bearing stainless steel. For example, for bearings made of 9Cr18 stainless steel used as fishing gear, in order to be applied in the ocean and improve the success rate of fishing, while maintaining its original wear resistance (hardness), it is required to not produce rust spots and maintain a uniform black color after 96 hours in artificial seawater.   Although using heat treatment methods can achieve better color, the hardness and wear resistance of bearings will be greatly reduced. Although using coatings can achieve satisfactory black color and maintain the original hardness, the bonding force is poor (mechanical bonding), and the coating will fall off shortly after use, causing a significant decrease in the corrosion resistance of bearings and quickly scrapping.   In order to maintain the original hardness (wear resistance) of bearing stainless steel while maintaining a uniform black appearance and high corrosion resistance, this work studied the chemical blackening technology of bearing stainless steel.   1.Test method 1.1 Materials Using 9Cr18 stainless steel, its chemical composition is (mass fraction): C 1.03%, Mn ≤ 1.00%, Si ≤ 1.00%, P 0.03%, S 0.005%, Cr 17.5%, Fe residue.   1.2 Process screening Using a mixture of sulfur and chromic acid, containing 100g/L H3PO4900g/L H2SO4100g/L CrO3, with a time of 100 minutes and a temperature of 80 ℃, the obtained film has a dark color and a hardness (HRC) of 56-57.   1.3 Salt spray test According to the test method in GB/T 10125-1997, 96 h continuous spray test is conducted under the condition of (50 ± 5) g/L NaCl solution, temperature (35 ± 2) ℃, pH 6.5~7.2.   1.4 Water resistance test According to the GB/T 1733-1993 test method, conduct water resistance tests on the above three samples in deionized water at (42 ± 2) ℃.   2.Test results 2.1 Salt spray test results The black 9Cr18 stainless steel bearings treated with the above process were subjected to salt spray testing with untreated bearings, and the results are shown in Table 1.   Table 1 Comparison of corrosion resistance between blackened and non blackened 9Cr18 bearings Bearing 12h 24h 48h 96h 9Cr18 Rust spots appear Increased rust spots Obvious rusting Severe rusting Blackening 9Cr18…

    Sat March 02 2024
  • Analysis and prevention of low hardness of nitrogen-containing stainless steel bearing rings

    Nitrogen-containing stainless steel is a new type of corrosion-resistant bearing steel, with the brand name 40Cr15Mo2VN. Compared with traditional bearing stainless steel 9Cr18, nitrogen-containing stainless steel not only has a better contact fatigue life than 9Cr18 when its mechanical properties are equivalent, but its salt spray corrosion resistance is much better than 9Cr18. The hardness requirement of nitrogen-containing stainless steel after heat treatment is ≥58HRC. After heat treatment, the surface hardness of a certain type of nitrogen-containing stainless steel bearing ring was found to be 55~56HRC, which is lower than the standard requirement.   The ferrule processing technology is: blanking → forging → turning → heat treatment.   1.Physical and chemical testing methods Select the heated ferrule and the machined ferrule, and make a metallographic sample by transverse wire cutting. The cross-section of the sample is the observation surface of the metallographic structure. The metallographic samples were mechanically ground and polished and then etched with saturated picric acid alcohol solution. The microstructure and carbide distribution morphology were observed with a Zeiss M2M metallographic microscope and a JEOL JSM-6610 scanning electron microscope. Nitrogen element was measured using ONH-2000 oxygen and nitrogen analyzer, and other elements were measured using ARL4460 direct-reading spectrum analyzer.   Observation results and analysis (1) Hardness inspection Test the Rockwell hardness of the sample surface and the center area of the section respectively. The surface hardness is 55~56HRC and the cross-section hardness is 58~59HRC. The hardness requirement of nitrogen-containing stainless steel after heat treatment is ≥58HRC. The surface hardness is lower than the technical requirements and the cross-section hardness meets the technical requirements. Require.   (2) Comparison of quenched and tempered structures After heat treatment of nitrogen-containing stainless steel, the microstructure should be tempered martensite + a small amount of primary carbides + dispersed secondary carbides.   The heat-treated ferrules were wire-cut to make metallographic samples, which were corroded by saturated picric acid alcohol solution and observed under a metallographic microscope and a scanning electron microscope respectively. The quenched and tempered structure of the normal area is shown in Figure 1. The spherical carbides are dispersedly distributed on the martensite matrix. The quenched and tempered structure of the area close to the surface is shown in Figure 2. Compared with the normal area, the carbide distribution is greatly reduced, and The martensite structure is abnormal and grain boundaries appear. Figure 1: Normal area quenching and tempering structure Figure 2 Quenching and tempering structure near the surface area   (3) Comparison of annealed structures Metallurgical samples were made from the same batch of ferrules after machining and before heat treatment. After corrosion, they were observed under a metallographic microscope and a scanning electron microscope. The spheroidized annealing structure in…

    Wed February 21 2024
  • China’s high-end stainless steel pipe manufacturing technology

    In the current era of high-quality development and green and low-carbon development in the steel industry, stainless steel has become a promising steel product due to its high corrosion resistance, long service life, low life cycle cost, and 100% recycling. The acceleration of the localization process of industrial materials such as nuclear power, military, and chemical industries, as well as the expansion of civil markets such as construction engineering and water supply, all indicate that the application prospects of stainless steel pipes are broad. The demand for products from users is constantly moving towards high-end - high, precision, special, fast, specialized, and provincial. At the same time, it will also promote the continuous innovation and progress of high-end stainless steel pipe manufacturing technology, support the stainless steel pipe industry to move towards green, intelligent, and high-quality Development towards service-oriented direction.   At the 2021 (2nd) China Stainless Steel Pipe Summit Forum, Academician Wang Guodong released the research results of high-end stainless steel pipe manufacturing technology by Professor Jiang Zhouhua's team at the 2011 Steel Common Technology Collaborative Innovation Center of Northeastern University. This article is organized based on the conference report.   Current Development Status of Stainless Steel in China According to the data from the Stainless Steel Branch of the China Special Steel Enterprise Association, the crude stainless steel production in China in 2020 was 30.139 million tons, an increase of 2.51%. Among them, Cr Ni steel (300 series) was 14.3796 million tons, accounting for 47.71%; 5.925 million tons of Cr steel (400 series), accounting for 19.66%; Cr Mn steel (200 series) weighs 9.6432 million tons, accounting for 32.007%. Imported stainless steel reached 1.8059 million tons, an increase of 686200 tons year-on-year or 61.33%; The export of stainless steel reached 3.4169 million tons, a year-on-year decrease of 255400 tons and a decrease of 6.95%. The apparent consumption of stainless steel was 25.6079 million tons, an increase of 6.64%. High end stainless steel pipe products 2.1 High nitrogen stainless steel High nitrogen steel is a new type of engineering material that has emerged in recent years. It is a steel whose actual nitrogen content exceeds the limit value that can be achieved by preparing materials under atmospheric pressure (0.1 MPa). Among them, the nitrogen content of high nitrogen austenitic stainless steel is above 0.40%, while the nitrogen content of high nitrogen ferritic iron and martensitic stainless steel is greater than 0.08%. The use of nitrogen as an alloying element can not only stabilize the austenite structure, improve strength, and prevent a significant decrease in toughness, but also improve corrosion resistance.   At present, high nitrogen stainless steel has become a major research hotspot, especially high nitrogen austenitic stainless steel. For…

    Wed January 31 2024
  • Stress corrosion and protective measures of austenitic stainless steel

    Abstract: Generally speaking, austenitic stainless steel has good corrosion resistance, but under special working conditions, stress corrosion can also occur, posing great safety hazards to engineering. This article discusses the conditions, corrosion mechanisms, and protective measures for stress corrosion of austenitic stainless steel, providing a basis for solving the problem of stress corrosion failure of austenitic stainless steel. Keywords: chemical equipment; Austenitic stainless steel; Stress corrosion; Protective measures   In the production process of petrochemical industry, the corrosion phenomenon of petrochemical equipment is particularly prominent due to the frequent contact between equipment and highly corrosive media, and the processing environment often operates under high temperature and high pressure. Generally speaking, ordinary steel has poor corrosion resistance to highly corrosive media, while austenitic stainless steel has become an important corrosion-resistant material in the petrochemical industry due to its excellent mechanical properties and weldability, as well as unparalleled corrosion resistance compared to other ordinary metals. The corrosion resistance of austenitic stainless steel is due to the formation of an extremely thin, adhesive, and semi transparent chromium oxide film on its surface. Cr and Ni are the main alloying elements in stainless steel with corrosion resistance. Cr and Ni cause austenitic stainless steel to form a very dense oxide film in oxidizing media, passivating it, reducing the corrosion rate of stainless steel in oxidizing media, and improving the corrosion resistance of stainless steel. Once this film is mechanically damaged and destroyed, a chemical reaction between chromium in the steel and oxygen in the atmosphere can quickly restore it. But the corrosion resistance of stainless steel is targeted, that is, it is stable in media such as air, water, and neutral solutions, while corrosion damage may occur in other media. According to statistics, in equipment corrosion, the corrosion of austenitic stainless steel accounts for about half of all types of corrosion, and the stress corrosion phenomenon of austenitic stainless steel materials accounts for more than two-thirds of all material stress corrosion.   Stress corrosion refers to the low stress brittle fracture of metals under the combined action of tensile stress and specific corrosive media. Stress corrosion cracking is a sudden low stress brittle fracture that occurs at a fast corrosion rate, with severe damage, and often without significant macroscopic deformation or corrosion on the metal surface. Due to the suddenness and unpredictability of this brittle fracture, it has considerable danger.   Production conditions Stress corrosion cracking is caused by the combined action of tensile stress and corrosion factors. In general, three conditions should be met to form stress corrosion fracture: (1) stainless steel with a certain chemical composition and organizational structure of a specific material, which is sensitive to stress corrosion in some media; (2) The…

    Fri January 19 2024
  • Performance and advantages of ceramic bearings

    Nowadays, ceramic bearings have been standardized and widely used. It has the following advantages: The friction coefficient of ceramic bearings is relatively small, so the transmission efficiency is also higher. The traditional friction coefficient of bearings ranges from 0.08 to 0.12, while the friction coefficient of ceramic bearings is only 0.001 to 0.005. Therefore, during their use, their performance is higher and maintenance is more convenient.   The manufacturing cost of ceramic bearings is relatively low compared to non-ferrous metals, and after heat treatment, they have higher mechanical properties and a longer service life.   The internal structure and clearance of ceramic bearings are very small, and the machining precision of their parts is relatively high, especially for some precision machinery, which has better operating accuracy. Not only can it achieve high transmission efficiency, reduce lubricating oil consumption, but it is also relatively simple and convenient for installation and maintenance.   In practical applications, ceramic bearings can be greatly improved in rigidity by preloading radial loads, and can even withstand the combined effects of radial loads and axial transmission loads under various conditions.   Various types of metal ceramics can cause varying degrees of corrosion when exposed to a certain pH environment, but ceramic bearings can operate normally in harsh environments filled with corrosive media.   Ceramic bearings, as a crucial basic component of mechanical equipment, are able to take the lead in the world of new materials due to their superior characteristics that metal bearings cannot surpass, such as high temperature resistance, super strength, and so on. Over the past decade, it has been increasingly widely applied in various industries related to national economy and people's livelihood. What are the advantages of ceramic bearings compared to other materials? Next, let's take you to understand.   Ceramic bearings have obvious advantages in the following aspects: The fatigue life of all ceramic bearings is 10-50 times longer than that of all steel bearings, and the service life of mixed ceramic bearings is about 3-5 times longer than that of all steel bearings; In terms of service life, ceramic bearings far exceed metal bearings.   The friction coefficient of ceramic bearings is low, so oil lubricated ceramic bearings still have higher lubrication capacity than traditional grease commonly used in steel bearings even when the lubricating oil becomes thinner or lacking.   Ceramic bearing steel has higher performance than metal bearings, and ceramic materials have a higher elastic modulus, with a rigidity 15-20% higher than general steel bearings.   Compared to metal bearings, ceramic bearings are more resistant to corrosion and wear. Due to the difference in their original materials, ceramic bearings can directly achieve better corrosion and wear resistance than metal bearings.…

    Fri January 12 2024
  • X-Large Hybrid Deep Groove Ball Bearings — A Reliable Solution for Wind Turbine Generators

    Abstract: Premature bearing failures of wind turbine generators are occurring frequently. The reasons are manifold, but based on application studies and bearing investigations two main root causes have been identified: electrical current passage, electrical erosion respectively, due to frequency converter supply of doubly-fed induction generators and lubrication and wear related problems. Strives to give an overview on typical root causes for premature bearing failures in wind turbine generator applications and introduces extra - large (XL) hybrid deep groove ball bearings as a new solution to significantly reduce generator bearing failures and to increase the overall reliability and operating availability of wind turbines. Key words: wind turbine genera tors; bearings; solution 0 Introduction The application of power electronic technology in speed control is more and more. This technology replaces many traditional speed regulation methods, such as mechanical gearbox drive, hydraulic drive, etc. The application of frequency converter enables the motor to adjust its speed freely from zero to rated speed and keep it running at a suitable working point, thus improving the efficiency and dynamic response of the motor and reducing energy consumption. The same technology is also used in wind turbines. In the past five or six years, the "doubly fed generator" in large-scale wind turbine equipment has become a typical application and is becoming more and more popular. This technology can enable wind turbines to operate in a relatively wide speed range. In the doubly fed generator, the rotor winding is powered by a frequency converter. The motor can optimize the generation energy and maintain a stable line frequency while changing the rotor speed, while regulating the active power and reactive power. However, due to the introduction of frequency converter system, bearing failure caused by over-current occurs frequently and becomes the main cause of early generator failure. At the same time, it is confirmed that the other main reason for bearing failure is lubrication and corresponding wear.   This paper describes the fundamental causes of early failure of bearings in the application of wind turbines, and introduces the technology of super large hybrid ceramic ball bearings. This technology proposed by can significantly reduce the failure of bearings in generators, and increase the overall reliability and operating stability of equipment.   1 Bearing failure in wind turbine Bearing is the most important part of various mechanical equipment parts. Bearing failure in the motor may also be caused by many other reasons, such as exceeding the expected load, improper lubrication, improper handling during transportation and shutdown, electrical corrosion, damage caused by installation and disassembly, pollution inside the bearing, seal failure, improper tolerance and fit between the shaft and bearing chamber, etc. Each factor will cause different damage, and at the same time,…

    Fri January 05 2024
  • Study on Process of Rings Made of TiCN Ceramic – Metal Bearings

    Abstract: The characteristics of TiCN material are analyzed. 160 # / 180 # alumna grinding wheel with ceramic agglutinative agent is preliminarily selected for the process of raceway of bearing rings ,120 # / 160 # and 160 # / 180 # wheel for rough grinding and fine grinding of side faces and inner diameter and outer diameter of rings respectively. The Machining technology is working - out for rings made of ceramic - metal.   Key words: TiCN ceramic - metal;rolling bearing;ring;grinding;technology   One of the main methods for processing engineering ceramic materials is grinding. Due to the high hardness of engineering ceramic materials, micro cracks and other defects are prone to occur during the processing. At the same time, grinding wheels are expensive, grinding efficiency is low, and processing costs are high (general processing costs account for 65% to 90% of the total cost). Therefore, it is very important to develop appropriate processing techniques and process ceramic parts with high quality, efficiency, and low cost as much as possible.   Grinding characteristics and processing methods of structural ceramics The characteristics of grinding structural ceramic materials: ① The grinding force ratio is large (about 3-14) [1], which is much higher than the grinding force ratio of ordinary grinding wheels (about 1 6-1.9), with high grinding resistance and low processing efficiency. ② The hardness of the material is high, and the grinding ratio is much smaller than that of steel. At the same time, the cost of abrasive tools is high, resulting in high processing costs.   The grinding process and surface quality of structural ceramic materials are different from those of metal materials and ordinary brittle materials. The characteristics of high hardness, high strength, and certain brittleness of structural ceramic materials determine that their grinding process is mainly characterized by brittle fracture, accompanied by elastic scratches, plastic flow deformation, and other phenomena, making it difficult to control the surface quality of grinding.   Diamond grinding wheels are commonly used for grinding structural ceramics. With the improvement of material properties, the research on new grinding methods for structural ceramics has also attracted increasing attention from researchers. Currently, new methods that can be used for structural ceramic grinding include constant pressure grinding and ELID mirror surface grinding.   Grinding and processing of TiCN metal ceramic ferrules TiCN ceramics are Ti (C, N) based ceramics. Compared to metals, they are similar to commonly used structural ceramics and have properties comparable to hard alloys. They have characteristics such as high temperature resistance, high hardness, corrosion resistance, and low coefficient of expansion.   2.1 Selection of grinding wheel Due to the advantages of high bonding strength, high stiffness, good heat resistance and wear resistance, and no fear of…

    Thu December 28 2023
  • Optimization design of the ceramic bearing based on iSIGHT

    Abstract: In order to make the interior structure parameter optimal, the mathematical optimization model of the ceramic bearing is set up. Based on this model, the whole optimal process is realized by iSIGHT software.The results show that this optimization has definitely instruction for ceramic bearing design. Key words: Optimization design; iSIGHT; Bearing   With the development of the machine tool industry, the demand for spindle speed is increasing. Currently, most high-speed spindles use angular contact ball bearings with excellent rigidity and high-speed performance. For ceramic ball bearings, domestic research institutions have also conducted a lot of research and made progress, but their research mainly focuses on the processing technology of ceramic balls, the fatigue life and performance testing of ceramic bearings, and there is less research on the structural design of ceramic bearings. This article mainly focuses on the angular contact ceramic ball bearings of the 7000C series, and optimizes the main parameters using iSIGHT software.   Optimization design of ceramic bearings 1.1 Theoretical basis for optimized design 1.1.1 Failure mechanism of ceramic bearings There are two forms of damage to hybrid bearings using silicon nitride (Si3N4) ceramics as rolling elements: damage to steel rings and damage to ceramic rolling elements. Both failure modes are fatigue failure, which is extremely similar to the failure mode of steel bearings. Through a large number of experiments and practical applications of hybrid ceramic bearings, it has been shown that the failure of hybrid ceramic ball bearings is mainly manifested by contact fatigue peeling of steel rings.   1.1.2 Life estimation of ceramic bearings For ceramic bearings, whether it is the load life index, rated dynamic load C, or various correction factors, they need to be determined based on a large number of experimental results. Therefore, research on the lifespan of ceramic bearings is still limited to comparative tests with steel bearings. Due to the same failure mechanism between hybrid ceramic and steel bearings, the life relationship between hybrid ceramic ball bearings and steel ball bearings can be obtained under the premise of considering material parameters:     Among       In the formula: subscript c, s - ceramic bearings and steel bearings; Q - The load applied by an external load on the rolling element; Fcc - centrifugal force of ceramic balls under high-speed operating conditions; P - The external load on the bearing; C - Rated dynamic load.   1.2 Establishment of mathematical models for optimized design 1.2.1 Objective function The objective function for optimizing the design of rolling bearings usually includes: requiring the longest fatigue life; Require the minimum rolling ratio; Require the longest wear life; Require the minimum friction torque and the maximum rated static load; Or a multi-objective function containing multiple…

    Wed December 20 2023
  • Application Analysis of Admixture Ceramics Bearings in High Rate Working Condition

    Abstract: The application status quo of admixture ceramics bearings in high rate working condition is introduced. The mechanical nature of Si3N4 ceramics material and bearing steel material are compared over - all , various predominance of admixture ceramics bearings in high rate working condition are analyzed. It also home illuminates that compared with the same model number ordinary steel bearings. The usage performance of the late - model admixture ceramics bearings is better , and the usage life is longer. Key words: admixture ceramics bearing; high rate working condition; Si3N4; analysis   Introduction With the rapid development of industrial technology, the requirements for mechanical equipment are also increasing, and working conditions such as high speed, high precision, high load, and high temperature are also increasing. The development of high-speed machining technology has promoted the process of high-speed machining of machine tool spindles. At present, the spindle of the machine tool ranges from 3,000 to 5,000 r/min developed to 15,000 to 70,000 r/min. For example, the vertical machining center of Boston Digtal in the United States has a spindle speed of 60,000 r/min, a high-speed CNC boring and milling machine from Mikron, Switzerland, with a spindle speed of 42,000 r/min, China has already introduced spindle speeds ranging from 15,000 to 25,000/min in the past few years. This will inevitably put forward new requirements and higher technical indicators for the supporting shaft and shaft components - bearings. The original steel bearings are difficult to adapt to such high speeds, and the use of hybrid ceramic bearings (using Si3N4 ceramic material for rolling elements and bearing steel for inner and outer rings) can fully leverage their performance advantages.   The current situation of the application of hybrid ceramic ball bearings in high-speed working conditions Hybrid ceramic ball bearings were initially mainly used in aerospace equipment, such as the United States using them on hydraulic pumps in space shuttles as early as the 1960s, and Japan and Germany also using them on aircraft engine equipment accordingly. In the past 10 years, it has been widely used in mechanical equipment such as high-speed electric spindles, machine tool spindles, dental drills, hard disk drives, and high-speed running instruments and meters. Due to the emergence of hybrid ceramic ball bearings, high-speed (dm=1.5 million) cutting that cannot be achieved with previous forms of all steel bearings and lubrication methods has become possible, and the spindle has reached practicality. In addition, the speed range that grease lubrication cannot reach (dm=1 million) is also due to the emergence of this type of bearing, which makes the low-temperature rise of the spindle practical. At present, hybrid ceramic ball bearings are used in computer fan heat sinks, with an effective service life of 80,000-100,000 hours;…

    Tue December 12 2023
  • Friction Characteristics of Hybrid Ceramic Bearing under Low-Volatility Grease Lubrication

    Abstract: To further study the friction characteristics of ceramic bearing, differences of friction characteristics between the hybrid ceramic bearing and the all-steel bearing were investigated by experiments using the basic friction tester under low-volatility grease lubrication. The results show that the static friction torque, the temperature rise and the friction power loss at high-speed running of hybrid ceramic bearing are less than those of all-steel bearing. The acceleration vibration performance of both bearings is almost the same. The value of velocity vibration of the hybrid ceramic bearing is much smaller than that of the all-steel bearing at low and inter-mediate frequency, while the result is reverse at high frequency. The application of ceramic bearing to the momentum wheel of satellites can imp rove the angular momentum-mass ratio of wheel, reduce the mass of the system and obtain better function density. Key words: hybrid ceramic bearing; satellite; momentum wheel; low-volatile greases; friction experiments.   The biggest advantage of small satellites is their high functional density, so their flywheel attitude adjustment system requires the highest possible angular momentum/mass ratio and the smallest possible volume There are two ways to improve the flywheel angular momentum/mass ratio: one is to optimize the design of the flywheel structure, and the other is to increase the flywheel speed At present, the flywheel speed is relatively low (usually between 3000 to 6000 r/m in), mainly due to bearing limitations. In recent years, ceramic bearings using SI3N4 ceramic material as bearing components have shown better performance than steel bearings under various harsh operating conditions (heavy load, high speed, corrosion, etc.), with higher ultimate speed and longer service life. Due to the late emergence of ceramic bearings, research on their performance has not been fully conducted, especially in special environments and conditions. This article conducted performance tests on FAG7002 hybrid ceramic ball bearings, and compared them with steel ball bearings of the same model in terms of starting friction torque, vibration (speed, acceleration), temperature rise at high speed, and power consumption.   1.Test bearing The test bearings are FAG (model HCS7002C. T. P4S. UL) and NSK (model 7002CTY. P4S. UL), each with four sets of bearings. Their external dimensions are shown in Table 1, and both bearings have an accuracy level of P4 (ultra precision level) Both types of bearings adopt grease lubrication method, and the lubricating grease used is FAG low volatility high-speed high-quality lubricating grease L52.   Table 1 External Dimensions of Test Bearings   2.Tests 2.1 Static Friction Moment Test A static friction torque comparison test was conducted on the YZC-II bearing friction torque tester for two types of bearings, and the results are shown in Table 2 The average static friction torque of ceramic ball bearings is smaller…

    Tue December 05 2023
  • Study on Process of Rings Made of TiCN Ceramic – Metal Bearings

    Abstract: The characteristics of TiCN material are analyzed. 160 # / 180 # alumna grinding wheel with ceramic agglutinative agent is preliminarily selected for the process of raceway of bearing rings ,120 # / 160 # and 160 # / 180 # wheel for rough grinding and fine grinding of side faces and inner diameter and outer diameter of rings respectively. The Machining technology is working - out for rings made of ceramic - metal. Key words: TiCN ceramic - metal ;rolling bearing ;ring ;grinding ;technology   One of the main methods for processing engineering ceramic materials is grinding. Due to the high hardness of engineering ceramic materials, micro cracks and other defects are prone to occur during the processing process. At the same time, grinding wheels are expensive, grinding efficiency is low, and processing costs are high (general processing costs account for 65% to 90% of the total cost). Therefore, it is very important to develop appropriate processing techniques to process ceramic parts as high-quality, efficient, and low-cost as possible.   Grinding characteristics and processing methods of structural ceramics The characteristics of grinding process for structural ceramic materials: ① The grinding force ratio is large (about 3-14), which is much higher than that of ordinary grinding wheel processing steel (about 1.6-1.9), with high grinding resistance and low processing efficiency. ② The hardness of the material is high, and the grinding ratio is much smaller than that of steel. At the same time, the cost of abrasive tools is high, resulting in high processing costs.   The grinding process and surface quality of structural ceramic materials are different from those of metal materials and ordinary brittle materials. The high hardness, high strength, and certain brittleness of structural ceramic materials determine that their grinding process is mainly characterized by brittle fracture, accompanied by elastic scratches, plastic flow deformation, and other phenomena, making the grinding surface quality difficult to control.   Diamond grinding wheels are commonly used for grinding structural ceramics. With the improvement of material properties, the research on new grinding methods for structural ceramics has also attracted increasing attention from researchers. Currently, new methods that can be used for structural ceramic grinding include constant pressure grinding, ELID mirror surface grinding, and so on.   Grinding of TiCN cermet ferrules TiCN ceramics are Ti (C, N) based ceramics. Compared to metals, they are similar to commonly used structural ceramics and have properties comparable to hard alloys. They have characteristics such as high temperature resistance, high hardness, corrosion resistance, and low coefficient of expansion.   2.1 Selection of grinding wheels Due to the advantages of high bonding strength, high stiffness, good heat resistance and wear resistance, and no fear of moisture, ceramic bonded alumina grinding wheels are selected to…

    Wed November 22 2023
  • Research on Ceramic Bearings for High Speed CNC Machine Tool Spindles

      Ceramic bearings With the development of the mechanical industry towards high-precision, high-efficiency, and highly automated directions, the working speed of various machines is constantly increasing. Currently, the spindle speed of CNC machine tools has increased from 3,000 to 5,000 r Π Min developed to 15,000 to 70,000 r Π Min. For example, the spindle speed of Boston Digtal's vertical machining center in the United States is 60,000 r Π Min, a high-speed CNC boring and milling machine from Mikron, Switzerland, with a spindle speed of 42,000 r Π Min. Machinery that operates in certain high-tech fields and special environments, such as aerospace, nuclear energy, chemistry, petroleum, and other industries, needs to work in special environments such as high temperature, high speed, corrosion resistance, vacuum, non-magnetic, oil-free lubrication, and light weight. Current steel bearings cannot meet these requirements. High speed rotating bearings generate a significant centrifugal force during rolling, causing the pressure between the ball and the outer ring raceway to exceed the external load, thereby shortening the service life of the bearing. At the same time, under the action of a large centrifugal force, the contact angle between the ball and the outer ring raceway decreases, or even drops to zero; The contact angle between the ball and the inner raceway increases. The former reduces the axial stiffness of the bearing, while the latter reduces the radial stiffness. In addition, excessive rotational speed will exert a significant gyroscopic torque on the ball, causing sliding between the ball and the ring, increasing frictional torque, causing heating and cage damage. Therefore, for high-speed machinery, relying solely on improving the structure and lubrication conditions of steel bearings is far from meeting the requirements. Further research and development of new bearings are needed to adapt to the high-speed transmission requirements of high-tech and industrial production development.   However, in high-speed and high-power spindle structures, bearings that can be used include magnetic levitation bearings, liquid dynamic and static pressure bearings, or ceramic ball bearings. Magnetic levitation bearing is a new type of intelligent bearing that utilizes electromagnetic force to suspend the spindle without mechanical contact or lubrication. It is an ideal support component for the spindle of ultra high speed machine tools, but due to the complex electrical control of magnetic levitation bearings and the high manufacturing cost of the entire bearing, it has not been promoted and applied until now, and is only used in high speed situations. Liquid dynamic and static bearing refers to a bearing structure that can produce a mixed support effect of dynamic and static pressure. This type of bearing must be specially designed and manufactured according to a specific machine tool, with low standardization and limited use.  …

    Tue November 14 2023
  • Research on the Application of Engineering Ceramics in Rotor Spinning Bearings

    Abstract: In order to improve the operational performance of rotor spinning bearings, the application of engineering ceramics on rotor spinning bearings was studied. Analyzed the problems of steel bearings in rotor spinning, proposed the requirements and preparation process for ceramic bearing materials, and trial-produced ceramic ball hybrid bearings. They were compared with steel bearings in operation on F1603 rotor spinning machine. The results show that the service life of ceramic ball hybrid bearings is increased by 5 times compared to traditional steel bearings, the temperature rise of bearings is reduced by 30%, and the noise is reduced by 2 dB. Keywords: rotor spinning; Ceramic ball bearings; Silicon nitride; Elastic modulus; Speed; Temperature rise; Wear resistance   The rotor spinning bearing is a special type of bearing with few parts and simple structure, but high speed, high accuracy, and reliable system performance. The yarn quality and economic benefits of rotor spinning mainly depend on the quality of the rolling bearing unit inside the rotor spinning device. It requires the rolling bearing unit to have high accuracy, high speed, reliable performance, low noise, low friction, long service life, low temperature rise, low resistance, and low maintenance. At present, domestic rotor spinning bearings are usually made of bearing steel. Due to the inherent characteristics of steel bearings, the rotor has disadvantages such as low speed, temperature rise, large vibration, high noise, and poor accuracy retention, which affects the yarn quality and production efficiency of rotor spinning. Ceramic materials have advantages such as low density, high hardness, high temperature resistance, and corrosion resistance, as well as excellent properties such as high strength and toughness. Therefore, they have broad application prospects in industries such as textiles. At present, hybrid ceramic bearings (steel rings and ceramic rolling elements) have been widely used in machine tool spindle bearings and other high-speed or precision equipment. Due to its excellent performance and broad development prospects, ceramic bearings have become a hot topic in the development and application of high-tech in the world, and have become one of the symbols of the material technology revolution in the mechanical industry.   Selection of ceramic materials The ceramic material used for manufacturing rolling bearing parts should have the following characteristics: Medium elastic modulus. The elastic modulus of engineering ceramics is approximately 1 5 times, so the elastic deformation of the relative load is small, and the rigidity of the relative load is high. However, if the elastic modulus is too high, it will reduce the bearing capacity due to stress concentration.   Low volume mass. The volume and mass of the rolling element decrease, and the centrifugal load also decreases when working at high speeds, allowing it to operate at higher speeds.   High…

    Thu November 02 2023
  • Ceramic bearings for locomotive traction motors

    Abstract: The causes of bearing current in traction motors, the damage forms, and the impact of electrical characteristics on insulated bearings were analyzed. In the application of traction motors, ceramic bearings are superior to steel bearings, as they have longer grease life and can effectively prevent electrical corrosion damage. Keywords: ceramic bearings; Locomotive traction motor; characteristic   The traction motor is the main equipment in the transmission system of electric locomotives and electric drive internal combustion engines. The traction motor bearings are used to support radial loads caused by the mass of the rotor shaft and coupling, achieving frequent operation and stopping of cyclic operations. Due to the impact of bogie vibration during operation, the bearings must withstand a certain dynamic load. Compared with axle bearings and gear unit bearings, the calculated life of traction motor bearings is much longer. The type of bearings generally adopts cylindrical roller bearings on the gear side (transmission side), and deep groove ball bearings with support for axial movement of the rotor shaft on the reverse gear side (commutator side), which are lubricated with grease. In recent years, variable voltage and variable frequency control AC traction motors have been installed on newly manufactured electric vehicles. These AC traction motors have the characteristics of light weight, compact structure, and high-speed operation. In order to adapt to the characteristics of high-speed rotation of bearings and temperature rise of various components of traction motors, it is necessary to solve the "electrical corrosion" hazard of existing steel bearings and improve the heat resistance and durability of bearings and lubricating grease.   Reasons and main damage forms of current generated in traction motor bearings The basic reasons and sources for the formation of bearing current include: asymmetric magnetic flow inside the motor; Asymmetric unshielded cable setup; Quickly switch frequency converters and their common voltage. These will cause three types of currents to be generated within the bearing, namely: high-frequency shaft grounding current; High frequency circulating current and capacitive discharge current.   The main damage caused by current to bearings is "electrical corrosion". Electrical erosion is a type of damage caused by localized melting caused by electric current passing through the very thin oil film in the rolling contact area of the bearing during rotation. The heat generated by discharge can cause local melting of the metal surface of the bearing, forming discharge marks, and the molten material particles transfer, making the local area very loose. The melted material hardens again, but is much more brittle than the original bearing material. Below the hardened material layer, there is a layer of toughened material that is softer than the surrounding material. Locomotive traction motor bearings often suffer from electrical dents, with…

    Fri October 27 2023
  • New Approach to Lapping Precision Ceramic Bearing Balls

    Abstract: A method for lapping precision ceramic bearing balls based on End Plane Grinding Lapping ( EPGL ) m ode is put forward in this paper, which make it possible to use solid abrasives easily. The kinetic analysis and simulation of EPGL m ode are made, and an experiment device is built up. Some primary experiments are carried out in order to investigate the influences of process parameters on the removal rate in processing ceramic bearing balls. It is found from kinetic analysis and the simulation that the sp in angle is changing continually during the process, as is benefit to the sphere generation and, the uniformity of lapping trace be acquired by means of EPGL. The results of experiments are discussed and analyzed, it indicates that the rotation speed of the p late and load have great effects on the removal rate of ceramic ball. Compared with the traditional V2grooves lapping mode, lapping with EPGL mode can obtain ceramic balls with high quality and much more efficient. Key words: ultra-precise ball; lapping uniformity; fixed abrasive; removal rate   Introduction With the development of industrial technology, precision ceramic balls have been widely used, but most of them are still processed by traditional equipment for precision steel balls, making it difficult to achieve high-precision and efficient processing of ceramic balls. So researching a new precision ceramic ball grinding method has become increasingly urgent. At present, in addition to the traditional V-groove grinding method, the main precision ball processing methods include coaxial three disc grinding method, magnetic fluid grinding method, eccentric V-groove grinding method, conical disc grinding method, and so on. These methods have significantly improved quality compared to traditional grinding methods, but there is still room for improvement in processing efficiency. Using fixed abrasive for grinding is an efficient grinding technique, but due to the complexity of traditional grinding discs for bearing balls, it is difficult to use fixed abrasive for grinding bearing balls. Therefore, a new type of bearing ball grinding equipment has been proposed, making it possible to easily use fixed abrasives.   Working principle Figure 1 shows the schematic diagram of the flat grinding method. During processing, the ball on the grinding disc undergoes pure rolling while spinning in the cage hole. Because there is only minimal contact deformation between the ball and the grinding disc, it can be considered that the grinding disc performs special grinding on the ball, called "point grinding". After spreading throughout the entire surface of the ball, a perfect grinding ball surface can be obtained.     Dynamic analysis Figure 2 is a plan view of the device, defining the structural and dynamic parameters. A is the contact point between the ball and the…

    Thu October 19 2023
  • The Promoting Effect of Material Technology on Product Innovation from the Development of Ceramic Bearings

    The bearings discussed in this article refer to rolling bearings, which are important mechanical basic components with a wide range of applications. The service conditions, operating accuracy, and service life of various machinery are often connected to bearings, and sometimes even depend on the parameters of the bearings. Therefore, mechanical innovation often involves bearing innovation, constantly launching high-end products with superior performance compared to widely used traditional products.   The improvement and expansion of bearing performance cannot be separated from three factors: design, technology, and materials. Especially in material technology, the promotion of bearing innovation is particularly evident. In the past 20 to 30 years, the application of high-tech ceramics has led to the development of high-end bearings with new performance. Some of these bearings have gradually entered the mainstream product line and are increasingly showing their irreplaceable potential in civil and national defense industries.   1.Overview of the Development of Ceramic Bearings Abroad The high-tech ceramics used in the development of ceramic bearings, also known as structural ceramics, fine ceramics, or advanced ceramics, mainly include silicon nitride, silicon carbide, zirconia, and alumina. Among them, silicon nitride is commonly used, which has many properties suitable for bearing manufacturing: silicon nitride has a high hardness; Has good corrosion resistance; The small density greatly reduces the centrifugal force of the bearing ball during operation, and the plastic deformation is very small. In addition, the linear expansion coefficient of silicon nitride is lower than that of bearing steel, and the temperature rise during bearing operation will not cause jamming. At the same time, silicon nitride is non-conductive and non magnetic, and operates under conditions such as strong magnetic fields, demonstrating superiority. The inferior performance of ceramics compared to steel is mainly due to its lower bending strength. However, through strict ceramic manufacturing processes, the strength of silicon nitride can currently reach 800-1000MPa, which is already suitable for applications in bearings.   The development of ceramic bearings as products began in 1984 with the collaboration of Toshiba Materials and Guangyang Seiko in Japan; In 1992, silicon nitride materials suitable for acid and alkali solutions were developed; In 1993, corrosion-resistant bearings were manufactured; In 1995, the excellent performance and high reliability of ceramic bearings were recognized, and NASA first used them on space shuttle turbopumps; In the same year, ceramic bearings were also used in automotive turbochargers; In 1999, ceramic bearings were successfully applied in the production of hard drives; After the 21st century, the application of ceramic bearings has further expanded, and many world-renowned enterprises have introduced their newly developed ceramic bearing products.   The world-renowned SKF company has launched the EXPLORER bearing series, which can work even under poor lubrication conditions, and reduces…

    Thu September 28 2023
  • Application and development prospect of ceramic materials in bearing industry

    Abstract: Starting with the analysis of high-tech ceramic materials, this paper expounds the performance characteristics of ceramic bearing materials and the comparison of steel bearing materials, as well as the development trend and prospect of ceramic bearings at home and abroad at present. Keywords: structural ceramic, ceramic bearing As we all know, bearing is an indispensable basic component in contemporary mechanical equipment. Although its rise is only a hundred years old, with superb modern science and technology, there are more than 100,000 kinds of bearings. In recent years, with the social progress and the high-speed development of science and technology, the application environment and conditions of bearings have become more and more diversified, and the requirements for the structure, material and performance of bearings have become higher and higher. Some high-tech fields and machinery working in some special environments, such as aerospace, nuclear energy, metallurgy, chemical industry, petroleum, instruments, machinery, electronics, textiles, pharmaceuticals and other industries, need to operate at high temperature and high speed. These new requirements are far from being satisfied only by improving the structure or lubrication conditions of traditional metal bearings, so it is necessary to develop new materials and fundamentally make breakthroughs and innovations. Studies at home and abroad have found that some ceramic materials have excellent performance, can withstand the harsh working environment that metal materials and polymer materials are not competent for, and have all the important characteristics required by bearing materials. Therefore, the application of ceramic materials in bearing manufacturing industry has become a hot spot in the development and application of high-tech in the world, and has become a symbol of material technology revolution in mechanical industry. Brief introduction of high-tech structural ceramic materials High-temperature structural ceramics are called advanced ceramics in Europe and America, fine ceramics in Japan, and high-tech ceramics in China at present. Compared with traditional ceramic materials (daily-use ceramics and building ceramics), high-tech ceramic materials have an essential difference, that is, the raw materials of traditional ceramics are natural minerals such as Shi Ying, feldspar and clay, while the raw materials of high-tech ceramic materials are chemical raw materials that have been artificially synthesized or refined by ー series. High-tech ceramic materials are usually made of ultra-fine powder (sub-micron and nano-powder) after ultra-high temperature and high pressure sintering. Compared with traditional ceramic materials, its strength has been improved hundreds of times, and with the excellent high temperature resistance, wear resistance, corrosion resistance, insulation and other characteristics of ceramic materials, it has been widely used in many important fields, especially in bearing manufacturing.   At present, high-tech structural ceramics mainly include silicon nitride (Si3N4), oxide dislocation (ZrO2) and alumina (Al2O3), etc. Its performance is compared with that of…

    Sat September 23 2023
  • What Are the Properties and Manufacture of Ceramic Bearings?

    Abstract: the important properties of engineering ceramics, bearing steel and other materials are analyzed in time ratio, and the production technology and testing means of ceramic bearings are analyzed. The application prospect is introduced, and the feasibility and importance of using engineering ceramics in bearing manufacturing are demonstrated.   Key words: engineering ceramics, bearings, non-destructive testing   Engineering ceramics is a new engineering material developed in recent years. Because it not only has the characteristics of high temperature resistance, wear resistance and corrosion resistance of traditional ceramics, but also has excellent characteristics such as high strength and high toughness, it has broad application prospects in the cutting-edge fields of national defense such as aerospace and industries such as machinery, metallurgy and chemical industry. At present, all industrialized countries in the world are investing a lot of manpower and funds in the research of various new engineering ceramic materials, Ceramic bearing is one of the most creative inventions among them. Because of its excellent performance and broad development prospects, ceramic bearing has become a hot spot in the development and application of high and new technologies in the world and a symbol of the material technology revolution in the mechanical industry.   Properties engineering of engineering ceramics Ceramic is a polycrystalline material, which is composed of different crystal lattice structures in the form of covalent bond, ionic bond or a mixture of the two, which determines that it has special properties that other materials such as metals do not have, that is, it has the characteristics of high temperature resistance, high hardness, wear resistance, corrosion resistance, low expansion coefficient and light weight   1.1 Hardness and strength The hardness of general engineering ceramics is more than twice that of metals, which determines that it has good wear resistance. The strength of ceramic materials is affected by such organizational factors as porosity, grain size and grain boundary phase content. Secondly, in order to improve the strength of ceramic materials, in addition to controlling the above organizational factors, composite and toughening methods can be used to improve the strength, Therefore, the strength of ceramic materials can be changed. The biggest feature of engineering ceramics is that the high-temperature strength is much higher than that of metal, and its compressive strength is very high, almost ten times that of metal materials.   1.2 Heat resistance Engineering ceramics generally can withstand a high temperature of 1 ℃ and maintain high hardness and strength under high temperature conditions, and have good thermal shock resistance. Therefore, for bearings used in high temperature environment, this characteristic is very advantageous.   1.3 Density Compared with metal materials, the density of ceramic materials is only 1/2~1/3 of that of ordinary steel. This…

    Thu September 14 2023
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