October 29, 2020

Ceramic bearings enter the era of industrial application

The story of the cover story, inherited from porcelain, has enabled the development of advanced ceramic technology and promoted humanity into a new stone age. The 21st century will be the coming of the Neolithic Age! At present, technology products have been widely applied to precision ceramics technology. After the war, in the early 1960s, the United States began to study ceramic bearings. The worldâ€™s first ceramic bearing was successfully developed by NASA. For more than 30 years, industrialized countries have incorporated ceramic materials into their national plans. In 1971, the United States Army Materials Research Institute (AMMRC) centered on researching engines for engines from a strategic point of view. In 1972, the NASA successfully developed ceramic bearings and achieved remarkable results from extreme secrecy to open sales. From the early 8th century, Japan and China began to study, and the era of ceramic bearings entering industrial applications has arrived.

With the advancement of science and technology, emerging industries continue to emerge. According to survey statistics, about one-third of the world's energy consumption is in different forms of friction, with bearings accounting for about 1/1. Therefore, the requirements for the basic parts of the mechanical industry are becoming more and more demanding, especially the machine performance has a very important impact, and its application is to the development of high precision, long life, high temperature resistance, corrosion resistance and high-speed automation. Production practice has proven that traditional bearings alone can improve the structure or lubrication conditions of bearings, and have not met the requirements of modern science and technology and industrial production development. Human progress in science and technology is always closely related to the appearance and use of new materials. Today, with the rapid development of science and technology, the development of bearings made of ceramic materials is the need for contemporary high-tech development. Ceramics is an indispensable material in human life and modernization. It is also listed as one of the three most solid materials in the contemporary world along with metal materials and organic polymer materials. The main difference between these three is the chemical bond, that is, the interaction forces between atoms are different, and thus show a great difference in properties. Ceramic materials are inorganic non-metallic materials with ionic bonds and covalent bonds as the main binding force. In the process of breaking through the traditional method, its chemical composition, microstructure and properties are different from ordinary ceramics, it is called "special ceramic" (special ceramic). Its main features are high temperature, strong strength, wear resistance and corrosion resistance. Become an important part of modern science and technology.

The development of bearings using ceramics is a modification of traditional bearings. The use and development of materials mark the milestones of human progress. Materials are also an important material basis for modern civilization. Therefore, industrial advanced countries all pay enough attention to materials. At present, there are 380,000 kinds of new materials that have been registered in the world. The State Council of China regards basic materials as the focus of national economic development and sets new materials as one of the eight major areas of the "863" high-tech plan.

Due to the rapid progress in ceramic bearing manufacturing technology in recent years, the manufacturing cost of ceramic bearings has been reduced, paving the way for wide industrial applications. The density of ceramic silicon nitride (Si3N4) is only 40% of that of steel. Therefore, using ceramic as the rolling element of the bearing, the centrifugal force of the rolling elements of the bearing can be greatly reduced at high speed, thereby reducing the pressure on the outer ring of the bearing. To achieve high speed, compared with steel bearings of the same accuracy class, the speed can be increased by 60%, the temperature can be reduced to 35% to 60%, and the self-lubricating performance is good, so it is not easy to produce the â€œpivot axisâ€ phenomenon. Its elastic modulus (E: KNmm2) is 320, and the bearing steel is 208. While the bearing rotates at high speed, although the rolling ball has only a few grams of weight, the centrifugal force acting on the ball sometimes reaches several tens of kilograms of force. The reason is to increase the friction and heat, but also reduces the rolling fatigue life of the ball, while the temperature rise of ceramic ball bearings is the same as the steel ball bearing at low speed, but at high speed, the temperature rise is slower than the steel ball if it's When the average surface roughness is below 0.0254 pm, the surface wear does not need to be considered, especially in water and seawater (low viscosity liquid lubrication) also require high bearing capacity and wear resistance. At the time, the absolute viscosity of water is 1/65 of the turbine viscosity, and the bearing capacity of the lubricating film is proportional to the viscosity, inversely proportional to the square of the film thickness, and the friction coefficient of the ceramic bearing is very small in the case of water lubrication, ceramic bearings Can exceed the service life of steel bearings by more than 1 time. It can achieve high-speed rotation in structure and it has good impact resistance. When the limit temperature of the ceramic bearing is 8~1, the hardness and strength begin to decrease, while the maximum temperature limit of the steel bearing can only reach 250-400:. At present, ceramic bearings do not yet have a national or international standard and normatively recognized standards and methods. Its accuracy is in line with ISO3290, AFBMA10 and DIN5401. From the theoretical study, the ceramic material has a higher elastic modulus, opening up a new application prospect for ceramic ball bearings with high rigidity and high-speed operation capability.

Heavy-Duty Powder-actuated Fastening Tool is designed for hard base concrete which is between C40 and C55. 

powder- Actuated Tool  (often generically called a Hilti gun or a Ramset gun after their manufacturing companies) is a type of nail gun used in construction and manufacturing to join materials to hard substrates such as steel and concrete. Known as  Direct Fastening , this technology relies on a controlled explosion created by a small chemical propellant charge, similar to the process that discharges a firearm.

Powder-actuated tools come in high-velocity and low-velocity types. In high-velocity tools, the propellant charge acts directly on the fastener in a process similar to a firearm. Low-velocity tools introduce a piston into the chamber. The propellant acts on the piston, which then drives the fastener into the substrate. (The piston is analogous to the bolt of a captive bolt pistol.) A tool is considered low velocity if the average test velocity of the fastener is not in excess of 100 m/s (330 ft/s) with no single test having a velocity of over 108 m/s (350 ft/s). High-velocity tools may not be made or sold in the United States[citation needed]; however, some made decades ago are still in use in the shipbuilding and steel industries. The main manufacturers of Powder Actuated Tools are Ramset, Hilti, Powers/DeWalt, Tomarco and Simpson Strong Tie.

Powder-actuated Fasteners are made of special heat-treated steel. Common nails are not used for powder-actuated fastenings. There are many specialized fasteners designed for specific applications in the construction and manufacturing industries.

Powder-actuated technology was developed for commercial use during the Second World War, when high-velocity fastening systems were used to temporarily repair damage to ships. In the case of hull breaches, these tools fastened steel plates over damaged areas.[1] These tools were developed by Mine Safety Appliances, for the United States Navy.[2] Powder-actuated tools were investigated and used prior to this development; they were used in submarine hunting during the First World War and were the subject of a 1921 United States patent (US Patent No. 1365869)

Heavy-Duty Powder-Actuated Fastening Tool

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