What are the classifications of high-strength bolts and what are the quality requirements?

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　　High-strength bolts are those made of high-strength steel, or bolts that require a large pre-tightening force; all such bolts can be referred to as high-strength bolts. What are the requirements regarding the classification and quality of high-strength bolts? Next, Pulete Fasteners will explain this to you. http://p1.pstatp.com/origin/dfic-imagehandler/58b140fa-fd44-4313-ab1b-e9b5c50ce100 I. Classification of high-strength waste bolts Friction-type high-strength bolts: Suitable for connecting beams and columns in steel frame structures, connecting solid-web beams, connecting heavy crane beams in industrial buildings, as well as for use in braking systems and other structures that are subject to dynamic loads. 　　Pressure-rated high-strength bolts: can be used for shear connections in static-load structures that permit a small amount of slippage, or in components that are subjected to dynamic loads indirectly. 　　Tensile high-strength bolts: When under tension, these bolts have a low fatigue strength, and under dynamic loads their load-bearing capacity rarely exceeds 0.6P (where P is the allowable axial force for the bolt). Therefore, they are suitable only for use under static loads, such as in the flange joining of compressed members or T-joints. 　　II. Precautions regarding the quality of high-strength bolts 1. Surface rust, oil stains, burrs on the bolt hole walls, and weld spurs must all be removed. 　　2. The treated contact friction surface must meet the specified requirements for the anti-slip coefficient. The high-strength bolts used shall be accompanied by matching nuts and washers, and they must be used in conjunction as specified; they cannot be interchanged. 　　3. The friction surfaces of the processed components must not be contaminated with oil, dirt, or any other debris at the time of installation. 　　4. During installation, the friction surfaces of the components must remain dry; work should not be carried out in rain. 　　5. Thoroughly inspect and correct the deformation of the connected steel plates before installation. 　　6. It is prohibited to drive the bolts in with a hammer during installation to prevent damage to the bolt threads. 　　7. For electric wrenches, conduct regular inspections during use to ensure torque accuracy, and follow the correct tightening sequence. 　　III. Main safety technical measures for high-strength bolts 　　1. The size of the jaw of the adjustable wrench used should match that of the nut; it is not permissible to use a small wrench with a sleeve attached to it. When working at high altitudes, a ratchet wrench should be used; if a slip wrench is used, it must be secured with a rope, and the person must wear a safety belt. 　　2. When assembling the connecting bolts of steel components, it is strictly prohibited to insert fingers into the connection surface or probe the bolt holes; when picking up or placing shims, fingers should be placed on both sides of the shim.