Venous cannula is also a deep venous puncture catheter. The method is to select the appropriate puncture site and insert the needle under the skin, and insert the needle with negative pressure until the dark red blood is absorbed, indicating that the needle has entered the vein, and the guide wire is inserted. Withdraw the puncture needle to leave the guide wire in the blood vessel, and then insert the venous catheter that needs to be indwelled along the guide wire, then exit the guide wire, inject diluted heparin saline and fix the catheter, the deep venous catheterization is completed. The veins for puncture and catheterization are usually selected clinically, including the subclavian vein, internal jugular vein, and femoral vein. After the puncture catheter is indwelled, attention must be paid to the care of the puncture site to avoid infection with thrombus or catheter falling off. venous cannulation,best veins for cannulation,venous cannulation set,venous cannulation technique Yong Yue Medical Technology(Kunshan) Co.,Ltd , https://www.yonyuemedicalcare.com
Superhard material cutters are characterized by high work efficiency, long service life and good processing quality. They used to be used for finishing. In recent years, due to the improvement of the production process of artificial superhard tool materials, the purity and grain size of raw materials have been controlled. Composite materials and hot pressing processes, etc., the application range is expanding, in addition to general finishing and semi-finishing, it can also be used for roughing, and is internationally recognized as one of the most promising tool materials for improving productivity in the world. . Using ultra-hard materials to process steel, cast iron, non-ferrous metals and their alloys, the cutting speed can be an order of magnitude higher than that of cemented carbide, and the tool life can be tens or even hundreds of times higher than that of cemented carbide. At the same time, its appearance also changes the traditional process concept. With super-hard tools, it can often be directly milled or milled (or polished). For hardened parts processing, a single process can be used instead of multiple processes, which greatly shortens the process. .
Superhard cutting tool materials development survey <br> <br> superhard tool material refers to a natural diamond and hardness, with similar performance synthetic diamond and CBN (cubic boron nitride). Since natural diamonds are relatively expensive, artificial polycrystalline diamond (PCD), polycrystalline cubic boron nitride (PCBN), and their composites are mostly used in production.
As early as the 1950s, the United States used synthetic diamond micropowder and artificial CBN micropowder to form larger size polycrystalline blocks as tool materials under the action of high temperature, high pressure, catalyst and binder. Since then, South Africa's DeBeers, the former Soviet Union and Japan have also been successfully developed. In the early 1970s, diamond or CBN and cemented carbide composite sheets were introduced. They were sintered or pressed on a cemented carbide substrate with a layer of 0.5 mm to 1 mm of PCD or PCBN to solve the bending resistance of superhard tool materials. Problems such as low strength and difficulty in inserting welds make the application of superhard tools into practical use. At present, artificial synthetic large single crystal diamonds, as well as functional materials such as diamond thin film coatings and diamond thick films produced by CVD (Chemical Vapor Deposition), have greatly expanded the application fields of superhard tool materials.
The research and application of superhard tool materials in China began in the 1970s. In 1970, the company built the first professional production plant for superhard materials and products in Guiyang. The sixth grinding wheel factory, from 2070 to 1990, was completely 20 years. The annual production of superhard materials has increased from 460,000 carats to 35 million carats. Around the 1990s, many superhard material production professional factories imported complete sets of superhard material synthesis equipment and technology from abroad, and the output has been developed rapidly. By 1997, the annual output of artificial diamonds in China has reached 500 million carats, and the annual output of CBN has reached 8 million carats, ranking first in the world's largest producer of superhard materials.
<br> <br> superhard materials diamond tool performance with high hardness and wear resistance, microhardness up 10000HV, the tool material is the hardest material. At the same time, its friction coefficient is small, it has no affinity with non-ferrous metals, the chips are easy to flow out, the thermal conductivity is high, the built-up edge is not easy to be formed during cutting, and the surface quality is good. Can effectively process non-ferrous metal materials and non-metallic materials, such as copper, aluminum and other non-ferrous metals and their alloys, ceramics, sintered carbides, various fiber and particle reinforced composite materials, plastics, rubber, graphite, glass And a variety of wear-resistant wood (especially composite materials such as solid wood and plywood).
The disadvantage of diamond is poor toughness and low thermal stability. It is easy to carbonize at 700 ° C to 800 ° C, so it is not suitable for processing steel materials. Since iron atoms easily interact with carbon atoms at high temperatures, they are converted into a graphite structure. In addition, when it is used to cut a nickel-based alloy, it also wears out quickly.
The hardness of CBN is second only to diamond (up to 8000HV~9000HV), and its thermal stability is high (up to 1250°C～1350°C). It is chemically inert to iron elements and has strong anti-bonding ability. It can be ground with diamond grinding wheel. It is suitable for processing hard-to-cut materials such as hardened steel, thermal spray materials, chilled cast iron and cobalt-based and nickel-based materials above 35HRC.
With the development of the materials industry and the precision machinery industry, the use of precision cutting, ultra-precision cutting and difficult-to-cut materials has increased, and the application of super-hard tool materials has become increasingly widespread.