Fasteners on the seawater machinery factory / Zhang Zhanfa and its code thread are widely used fasteners, according to the size of the pitch into coarse and fine teeth, according to the direction of rotation into left and right hand, by line number For single-line and multi-wire; according to the purpose, it can be divided into three types: joint thread, drive thread and load bearing thread. At present, international exchanges are increasing, and the localization of spare parts is becoming more and more. At present, the main problems are: the pitch of the American inch thread 1/2 is 〖3 teeth per inch, and the mistake is the British inch 1/2 inch per inch is 12 teeth, the cone angle of the taper pipe thread R = 55 and = 60 taper pipe thread NPT profile angle 60 mixed, resulting in failure to connect and leak. The following is a brief introduction of common thread and other codes in various countries. Common thread and code in China Common thread and code are shown in Table 1. Table 1 China common thread and code name Standard number code standard example Remarks General thread tooth angle a rectangular thread no standard square tooth diameter x pitch square 40 trapezoidal thread tooth angle a sawtooth thread tooth angle a tube connection fine tooth common thread With the common thread profile angle a pipe thread non-thread sealed pipe thread rotation (right rotation is not marked) tooth angle a threaded cone pipe thread profile angle a = 55 ° (old code ZE) 60 pipe thread Profile angle a = 60 ° (old code is Z) metric taper pipe thread ZM10 - standard base distance ZmlO-S - short base pitch tooth angle a inch standard thread and code British standard thread and code shown in Table 2. Table 2 British standard thread and code name Standard number code standard example Remarks BSW-coarse teeth BSF-fine tooth profile angle a British BA thread profile angle a fastener US standard thread and code US standard thread and code shown in Table 3 . Standard code and sample tooth angle are divided into four categories: coarse teeth (UNC, NC) fine teeth (UNF, NF) special teeth (UNEF, NEF) special teeth (8N, 12N, 18N) one named after the number of teeth per inch UNR (the bottom of the tooth is a round orphan) 55-inch Wyeth thread r below the number of teeth per inch is the same as the British Wyeth thread 1/2 〃 for 13 teeth, r and r above the number of teeth are 8 teeth NPTF sealing cone pipe thread, such as NPTF1/8-27 tooth metric thread BI.13M Table 3 US standard crepe and code 曰 This standard thread and code table 4 Japanese standard smear and code name code standard example standard number tooth common thread MM16ISB0205 fine tooth common thread MM16x1.5ISB0207 Threaded sewing machine thread SMSM1/4 tooth 40ISB0226 lamp mouth thread EE10ISC7709 car tire valve thread TVTV8ISD4208 bicycle tire valve thread CTVCTV8 tooth 30ISD9422MC article number: W1025 Japanese standard thread and code shown in Table 4. The AIN crystal is a covalently bonded compound with a [AIN4] tetrahedron as a structural unit, and has a wurtzite structure and is a hexagonal system. Chemical composition AI 65.81%, N 34.19%, specific gravity 3.261g / cm3, white or grayish white, single crystal colorless and transparent, sublimation decomposition temperature under normal pressure is 2450 °C. It is a high temperature heat resistant material. Thermal expansion coefficient (4.0-6.0) × 10 -6 / ° C. Polycrystalline AIN has a thermal conductivity of 260W/(MK), which is 5-8 times higher than alumina, so it has good thermal shock resistance and can withstand extreme heat of 2200 °C. In addition, aluminum nitride is not attacked by aluminum liquid and other molten metals and gallium arsenide, and particularly has excellent corrosion resistance to molten aluminum liquid. Aluminum Nitride Ceramic,Aluminum Nitride Plate,Aluminum Nitride Shaft,Boron Nitride Ceramic Shaft Dongguan Haikun New Material Co., Ltd. , https://www.nitrideceramic.com