China's import and export of metal materials that need to be inspected mainly include pig iron, steel ingots, billets, profiles, wires, metal products, non-ferrous metals and their products. The quality and specifications of import and export steel are generally specified in the contract. The imported steel is made of Japanese Xiff' standard JlsG series and German industrial standard DIN series. The ammonia export steel is generally tested according to Chinese standards; about imported galvanized iron sheet, tinplate, silicon steel sheet The inspection of appearance defects shall be carried out in accordance with the relevant provisions of the State Administration of Commodity Inspection. Foreign invoices, packing lists, quality certificates, re-listing details, damage certificates, and business records are important basis for inspection and appraisal of weight, quality, quantity, and damage. Metal materials are generally produced by the State Administration of Commodity Inspection or Other The commodity inspection agency carries out inspections. For large quantities of imported metal materials, they can be inspected at foreign manufacturers before leaving the factory; for professional units with large batches of imported metal materials, their own testing equipment and technical strength are strong, and after approval by the commodity inspection authorities, permission is allowed. After the steel products imported by the company are declared to the commodity inspection authorities, the quality inspection shall be carried out; when the metal materials are exported, the factory inspection shall be carried out, and the commodity inspection agency shall conduct random inspections during the production process or before leaving the factory, and check the weight with the weighing instrument. , check batches, taro, marks, etc. Metal materials are quantity-tested for quantity, and weights are used for weight inspection. Inspection of steel dimensions, including thickness, width and length of steel plates; diameter of round steel: length of angle steel; height and groove width of channel steel; diameter and wall thickness of steel pipe. The surface of galvanized iron and tinplate shall not have any scratches, pits, wrinkles, or exposed iron. Mechanical and process performance testing of metal materials, including mechanical properties testing of alloy steel after heat treatment; hydraulic pressure test and flaring test of boiler tubes and oil pipes. Chemical salt analysis test of metal materials, according to different purposes, according to the standard provisions of chemical analysis and instrumental analysis, analysis and determination of various elements, including non-metallic elements and harmful elements. Fastening Screws, also known as positioning screws, fastening also known as machine rice screws, headless screws, stop screws Socket Set Screw ,Hex Set Screw,Set Screw Types,Cup Point Set Screw Kunshan Zhonggu Precision Hardware Co., Ltd. , https://www.zgfastener.com
1. Application scope: Hexagonal set screws with concave end are used for machine parts with high hardness requirements or frequently adjusted, and are a kind of screws designed for fixing the relative positions of machine parts.
2. Commonly used fastening type: flat end fastening, tip fastening, concave end fastening, column end fastening
3. Reference standards.
Flat end fastening: GB77, DIN913, ISO7026
Tip tightening: GB78, DIN914, ISO4027
Concave end tightening: GB80, DIN916, ISO4029
Column end tightening:GB79.DIN915.ISO4028
