What are the characteristics of the materials used in the hooks?

Hooks are critical to the safe and reliable operation of cranes. To this end, there are strict requirements for the material and processing of the hook.

Because high-strength steel is sensitive to cracks and defects, the materials used to make the hooks are all made of high-quality low-carbon killed steel or low-carbon alloy steel. The steel grades are DG20, DG20Mn steel and DG34CrMo, DG34CrNiMo alloy steel.

The hook made by forging and stamping, and then mechanically processed after annealing has the characteristics of high strength and good plastic toughness.

The chip hooks are generally used in places where large tonnage is blazed by strong burning objects. Sheet hooks are usually produced from A3, 20 or 16Mn steel sheets having a thickness of not less than 20 ram, and no sudden breakage occurs, resulting in high reliability.

Since the fracture caused by the defect is limited to individual steel plates, the remaining steel plate can still support the hoisting weight, and only the individual steel plates can be replaced, and the hook plate cannot be broken at the same time, so it has greater safety.

However, the sheet hook can only be manufactured into a rectangular section, so the strength properties of the hook material cannot be fully utilized.

Because the casting material has many quality defects, such as shrinkage, shrinkage, thermal stress, slag inclusion defects, etc., easy to crack, not easy to be found, so the crane should not use cast steel hook;

Weld hooks cannot be used because they have defects such as air holes, slag inclusions, incomplete penetration, cracks, etc.; hooks cannot be made of steel with high strength and low impact toughness.

When forging the hook, the mark with the rated lifting weight, the factory mark, the inspection mark, the date, the number, etc. shall be printed in the low-stress area, and the surface inspection and load test shall be carried out by the forging factory to provide the certificate of conformity.