Lifting Hooks play an important role in the safe work of lifting appliances. For this reason, there are very strict requirements for the materials and processing of the hooks. Because high-strength steel is very sensitive to cracks and defects, the materials used to make the hooks are made of special high-quality low-carbon static steel or low-carbon alloy steel. The steel grades are DG20, DG20Mn steel and DG34CrMo. And other materials. After forging and stamping, the hook group that has been machined after annealing has high strength and good plastic toughness.
Because the casting material has many quality defects, such as shrinkage, shrinkage, thermal stress, slag inclusion and other defects, it is easy to crack, it is not easy to be found, so the crane should not use cast steel hook; can not use welding hook, Because the welding has defects such as pores, slag inclusions, incomplete penetration, cracks, etc.; it is also impossible to manufacture hooks from steel with high strength and low impact toughness.
When forging the hook group, it should be marked with the rated lifting weight, inspection mark, factory mark, inspection mark, date, number, etc. in the low-stress printing, and the surface inspection and load test are carried out through the forging factory. After that, provide a document of qualified certification.