The different materials of the blow bars depend on the blow bars itself, which could be made of manganese steel, martensitic structural steel (martensitic steel), chrome steel, or metal matrix composites (MMC, such as ceramic). MMCs are composed of various types of steel and special kinds of ceramic.
As the wear-resistance (hardness) of steel material increases, the toughness (impact resistance) will normally decrease.
The wear-resistance of manganese steel comes from work hardening. The surface under force generates structural hardening under impact load and extrusion load. The initial hardness of the manganese steel is about 200 HV (20 HRC, according to Rockwell hardness test), and its impact strength is about 250 J/cm2. After work hardening, the initial hardness increases to working hardness which is about 500 HV (50 HERC), while the deeper center part still remains the good toughness of steel material since it is not hardened. The thickness and the hardness of the work-hardened layer depends on the application and the type of manganese steel. The thickness of the hardened layer is about 10 mm.
Manganese steel, which has a long history of usage, is now mainly used for jaw plates, moving cones and shells of crushers. For the impact crusher, it is suggested only to use manganese steel blow bars when crushing materials with low wear – consuming at a large amount, such as limestone.
The carbon in chrome steel is chemically bound in the form of chromium carbide. The wear-resistance of chrome steel is mainly based on the characteristic of these hard carbides. The offset of position and offset between layers is restrained during hot processing, thus obtaining high strength and lower toughness. To prevent the material from becoming brittle, the blow bar must be processed with heat treatment, which must be conducted according to the strict heating temperature and annealing time.
Post time: Jul-28-2021