Application standard and scope of high

strength nut

         Application standard and scope of high strength nut 

    Reference standard for specification of large hexagon nut 

    GB / t90-1985 fastener acceptance inspection, marking and packaging (EQV iso3269:1984)   

   GB / t196-1981 ordinary screw threads, basic dimensions (diameter 1 ~ 600mm) 

     GB / t197-1981 general purpose screw threads, tolerances and fits (diameter 1-355mm) 

     GB / t1237-2000 marking methods for fasteners (EQV ISO 8991:1986)   

    GB / t3098.2-2000 mechanical properties of fasteners nuts, coarse thread (IDT ISO 898.2:1992) GB / t3103.1-1982 (confirmed in 1988) tolerances for fasteners bolts, screws and nuts (EQV iso4759-1:1978) GB / t5267-1985 electroplated coatings on threaded fasteners       

  GB / t5276-1985 fasteners - Bolts, screws, studs and nuts - Dimensional codes and marking (EQC ISO 225:1983) GB / t5779.2-2000 fasteners surface defects nuts (IDT ISO 6157.2:1995) 

GB / t6170-2000 L-type hexagon nuts (EQV ISO 4032:1999)     

     GB / t6938-1997 fasteners - Bolts, screws, studs and nuts - General technical conditions (IDT iso8992:1996) iso10683:2000 fasteners - non electrolytic zinc powder coating 

      So where are high strength nuts used? 

         It is used in high-strength bolt pairs, and the strength grade (after heat treatment) is grade 10, which is used with grade 10.9 bolts.     

          The mechanical properties and calculation methods of ordinary bolts and high strength bolts are different. The high strength bolt bears the external load first by applying pre tension P in its interior, and then produces friction resistance on the contact surface between the connected parts, while the ordinary bolt bears the external load directly. High strength bolt connection has the advantages of simple construction, good mechanical performance, replaceable, fatigue resistance, and no loosening under dynamic load. It is a promising connection method. 

           High strength bolt is to use a special wrench to tighten the nut, which makes the bolt produce huge and controlled pre tension. Through the nut and base plate, the same amount of pre pressure is produced on the connected parts. Under the action of pre pressure, greater friction force will be generated along the surface of the connected parts. Obviously, as long as the axial force is less than this friction force, the component will not slide and the connection will not be damaged. This is the principle of high strength bolt connection.   

         High strength bolt connection is based on the friction between the contact surfaces to prevent them from sliding. In order to make the contact surface have enough friction, it is

necessary to increase the clamping force and friction coefficient of the contact surface. The clamping force between components is realized by applying pre tension to the bolt, so the bolt must be made of high strength steel, which is the reason why it is called high strength bolt connection. 

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