紧固件材料的选择(螺栓、螺母)（Selection of fastening materials (bolts, nuts)）.doc

紧固件材料的选择(螺栓、螺母)（Selection of fastening materials (bolts, nuts)） 1, fastener six hexagon head bolts, stud, screw and full length bolt and nut, stud thread end chamfering end type with GB two. 2, fastener specifications Flange fastener specifications: M10, M14, the M16, M20, M22, M24, M27, M30, M33, M36*3, M39*3, M45*3, M48*3, M56*3, M64*3, M70*3, M76*3, M90*3. Common fasteners shall conform to GB5782 requirements and GB901-B level specifications. 3, mechanical properties The GB3098.1 bolt nut class 8 grade 8.8. The China standard for petrochemical industry: Bolt, stud with grade 35#, 40CR, 30CRMO, 35CRMOA, and 25CR2MOVA materials. The nut grades 25#, 40CR, 35CRMOA, 25CR2MOVA, and other materials. Other mechanical performance index: Index of strength is more than 800MPa-900MPa. The yield strength is more than 640MPa-720MPa. The elongation is above 12-15%. The hardness of HRC25-35%. 2008-4-22 9:46:17 network standard fasteners Fastener material First, current market standard parts are mainly carbon steel, stainless steel, copper and three kinds of materials. (a) carbon steel. We distinguish between low carbon steel with the content of carbon in carbon steel, medium carbon steel and high carbon steel and alloy steel. 1, low carbon steel C% is less than or equal to 0.25% domestic commonly known as A3 steel. Foreign called 1008101510181022. Mainly used for grade 4.8 and grade 4 bolts nuts, screws and other small non hardness products. (Note: drilling screws with 1022 main materials.) In 2, 0.25%C% SPAN = 0.45%, the domestic carbon steel is often referred to as No. 35 and No. 45 steel, foreign called 1035, CH38F, 1039, 40ACR. Mainly used for Grade 8 and grade 8.8 bolts and nut 8.8 inner six angle products. 3, high carbon steel C%0.45%. Currently on the market basically no use 4, adding alloying elements in alloy steel, carbon steel, add some special properties of steel such as: 35, 40 Cr Mo and SCM435, 10B38. Fang Sheng screw using SCM435 chromium molybdenum alloy steel, t