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　　1. General requirements for hook

　　1) Use environment requirements;

　　2) The materials and purchased parts for the hook should have certificates of conformity from the manufacturing unit;

　　3) Qualified hooks should have marks that are not easy to wear, and the marking content should at least include: rated lifting weight, production number, manufacturing date, manufacturing unit, original opening degree of the hook, and issuance of certificates of conformity.

　　2. Classification and material requirements of hooks

　　1) It is divided into two types according to shape: single hook and double hook: single hook is divided into short (A) type and long (B) type. The only difference between the two is the length of the hook body. A balance pulley is installed on the long hook group, which can be used for singular pulley sets, with a large lifting weight; a short hook group is only suitable for double pulley sets, with a small lifting weight. The cross-sectional shape of the hook body is round, square (usually in sheet type, and its hook mouth is usually equipped with mild steel pads), trapezoidal and T-shaped.

　　According to the manufacturing method, it is divided into forged hooks and sheet hooks (plate hooks), and the board hooks are made into single hooks (lift weight of 37.5~175t) and double heat (lift weight of 100~350t).

　　2) The material of the hook requires high strength, plasticity and toughness, and there is no risk of sudden breakage. Materials with high strength are generally sensitive to cracks and defects. The higher the strength of the material, the greater the possibility of sudden breakage. Therefore, the hook materials are widely used in low-carbon structural steel and low-carbon alloy structural steel, such as DG20, DG20Mn, etc.

　　3. Dangerous cross-section of the hook Vertical cross-section: Heavy objects are hung on them through wire ropes, mainly under shearing stress.

　　Horizontal section: The inner tension, the outer compression, and the inner tensile stress are more than 1 times greater than the outer compressive stress, and mainly bears bending moments and tensile stresses.

　　Hook tail thread part: The hook tail thread part is a dangerous section of tension and mainly bears tensile stress.

　　4. Tips for quickly determining whether the hook opening degree meets the scrap standard

　　Opening degree s=0.75D; h=D. Mastering this method can quickly determine whether the hook can continue to be used or has reached the scrapping standard, which is very practical for people engaged in lifting operations.

　　5. Taboos

　　1) Piece hooks are not allowed to be spliced.

　　2) There should be no defects in the surface and interior of the hook that affect its usability.

　　3) Casting hooks are not allowed, because internal defects in castings are not easy to detect and eliminate.

　　4) Hooks made or repaired by welded parts are not allowed, because steel may produce cracks during welding.

　　1. General requirements for hook

　　1) Use environment requirements;

　　2) The materials and purchased parts for the hook should have certificates of conformity from the manufacturing unit;

　　3) Qualified hooks should have marks that are not easy to wear, and the marking content should at least include: rated lifting weight, production number, manufacturing date, manufacturing unit, original opening degree of the hook, and issuance of certificates of conformity.

　　2. Classification and material requirements of hooks

　　1) It is divided into two types according to shape: single hook and double hook: single hook is divided into short (A) type and long (B) type. The only difference between the two is the length of the hook body. A balance pulley is installed on the long hook group, which can be used for singular pulley sets, with a large lifting weight; a short hook group is only suitable for double pulley sets, with a small lifting weight. The cross-sectional shape of the hook body is round, square (usually in sheet type, and its hook mouth is usually equipped with mild steel pads), trapezoidal and T-shaped.

　　According to the manufacturing method, it is divided into forged hooks and sheet hooks (plate hooks), and the board hooks are made into single hooks (lift weight of 37.5~175t) and double heat (lift weight of 100~350t).

　　2) The material of the hook requires high strength, plasticity and toughness, and there is no risk of sudden breakage. Materials with high strength are generally sensitive to cracks and defects. The higher the strength of the material, the greater the possibility of sudden breakage. Therefore, the hook materials are widely used in low-carbon structural steel and low-carbon alloy structural steel, such as DG20, DG20Mn, etc.

　　3. Dangerous cross-section of the hook Vertical cross-section: Heavy objects are hung on them through wire ropes, mainly under shearing stress.

　　Horizontal section: The inner tension, the outer compression, and the inner tensile stress are more than 1 times greater than the outer compressive stress, and mainly bears bending moments and tensile stresses.

　　Hook tail thread part: The hook tail thread part is a dangerous section of tension and mainly bears tensile stress.

　　4. Tips for quickly determining whether the hook opening degree meets the scrap standard

　　Opening degree s=0.75D; h=D. Mastering this method can quickly determine whether the hook can continue to be used or has reached the scrapping standard, which is very practical for people engaged in lifting operations.

　　5. Taboos

　　1) Piece hooks are not allowed to be spliced.

　　2) There should be no defects in the surface and interior of the hook that affect its usability.

　　3) Casting hooks are not allowed, because internal defects in castings are not easy to detect and eliminate.

　　4) Hooks made or repaired by welded parts are not allowed, because steel may produce cracks during welding.