The hammer wear of hammer crusher is inevitable, but if the wear is too fast and the frequency is too high, it is necessary to check whether there are problems in the equipment itself or in the operation. The main factors affecting the wear of the hammer are: hammer material, manufacturing quality and structural design, the technical design of the crusher, the feeding situation and the gap of each part of the structure, etc.
Generally speaking, the greater the hardness of the hammer wear resistance is also greater. To improve the wear resistance of the hammer, it is necessary to increase its hardness, but with the increase of hardness, the impact toughness of the hammer will decrease. Therefore, how to take into account the appropriate hardness and good impact toughness of the hammer is the key to improve the wear resistance of the hammer.
Hammer commonly used materials are: high manganese steel, high chromium cast iron, low carbon alloy steel.
High manganese steel has good toughness, good manufacturability and low price. Its main characteristic is that under the action of larger impact or contact stress, the surface layer will quickly produce work hardening. Its work hardening index is 5 ~ 7 times higher than other materials, and its wear resistance has been greatly improved. However, if the impact force is not enough or the contact stress is small, the surface can not quickly produce work hardening, and the wear resistance of high manganese steel can not be fully played.
High chromium cast iron is a kind of wear resistant material with excellent wear resistance, but it has low toughness and is prone to brittle fracture. In order to make the high chromium cast iron hammer head run safely, people developed composite hammer head, that is, the high chromium cast iron is incast in high manganese steel or low alloy steel hammer head head, or the hammer head working part is made of high chromium cast iron, the hammer handle part is made of carbon steel, the two are combined to make the hammer head has high hardness, and the hammer handle has high toughness. Give full play to the advantages of the two materials and overcome the shortcomings of single material to meet the performance requirements of hammer. But its manufacturing process is complex and the technological requirement is strict.
Low carbon alloy steel mainly contains chromium, molybdenum and other elements of alloy structural steel, high hardness, good toughness, its matrix structure of martensite, bainite or bainite + martensite composite structure. Under the same working conditions, the service life of the hammer is more than one times that of the high manganese steel hammer. But the quenching and tempering heat treatment is the key. After quenching and tempering heat treatment, the overall tensile strength should not only be more than 850MPa, but also considerable plasticity and toughness.
2. Hammer head manufacturing quality
The manufacturing process of hammer head is also the key factor to determine its service life. If there are defects in the surface or internal manufacturing of the hammer head, such as shrinkage cavity, crack, transcrystal, etc., it will not only reduce the performance of the hammer head, but even cause the hammer head fracture. Therefore, reasonable casting and heat treatment process must be formulated in the production of hammer.
For example, for high chromium cast iron hammer, should use vertical casting and reasonable use of external cooling iron, and strict control of casting temperature and other measures, so that the hammer in casting have a good solidification sequence and feeding conditions, and then get dense internal organization, and weaken the phenomenon of coarse grains.
3. Hammer head structure design
The mechanical properties and internal microstructure of the hammer with different structure and geometry are very different, which have a great influence on the wear resistance, especially for the hammer with large thickness and size. The thicker and larger the hammer head, the less likely it is to be quenched, and the worse its wear resistance will be.
Due to the interior of the hammer head wear resistance significantly below the surface, therefore, for larger thickness of hammer head, only by means of reasonable casting and heat treatment process to improve the situation, but it is a means to improve the wear resistance of hammer head is limited, is the best way to without changing the kinetic energy of the hammer blow and strength of the case, the structure optimization design of hammer head, On the one hand, the utilization rate of the hammer can be improved, on the other hand, the influence of the structure on the heat treatment performance can be reduced, and the wear resistance of the hammer can be avoided.
4. Technical parameters of crusher
The life of the hammer is also related to the technical parameters of the crusher, among which the most important is the power and speed of the rotor. These two parameters directly reflect the linear velocity and impact force of the hammer head, which are not only related to the production capacity of the crusher, but also related to the degree of the hammer head impact hardening.
Good impact hardening hammer, the service life is bound to be extended. The rotor speed is too low, not only the production capacity is low, and the kinetic energy is low, resulting in poor impact hardening hammer, wear resistance is poor; The rotor speed is too high, although can make the hammer get better impact hardening, equipment productivity, but also will cause the hammer, grate and liner strong wear, the service life of the hammer is not good, at the same time will significantly increase the power consumption.
5. The clearance of each part of the crusher structure
Here mainly refers to the rotor body and the crushing plate, grate and the clearance of the feeding roller, and the clearance between the hammer. The size of these clearance is related to whether there is a deposit on the grate and near the safety door.
If there is accumulation, when the hammer can not be accumulated from the grate on the pressure down, it will be serious friction wear. The gap is too small, although can improve the crushing quality and efficiency of the material, but easy to form accumulative material, blockage, resulting in hammer wear; Too large clearance, although can avoid material accumulation, but the crushing effect and low efficiency. Therefore, hammer crusher in use, must often adjust the clearance of each part, so that it is in the appropriate range. Improve the grate structure, make the discharge unobstructed, also help to reduce the wear of hammer.
6. Crusher feeding situation
Feeding conditions include: ① Feed size and hardness; (2) The feeding method of crusher. The former is related to whether the crusher will be accumulated and hammer hit material by the impact impulse, the latter because of different feeding methods caused by the material to the rotor drop is different, but also affects the hammer hit material when the impact impulse.
When the weight of the hammer and the rotor speed is constant, the impact impulse of the hammer is directly proportional to the material quality and the drop, and the impact impulse is directly related to the degree of work hardening and wear resistance of the hammer. Therefore, the feeding particle size of large hammer crusher should not be too small, and the speed of feeding equipment should be higher.
In addition, the material water content is too large will also have a certain impact on the hammer life. Too high water content, the material is easy to bond into a group, resulting in material accumulation, aggravating the wear of the hammer.
Hammer crusher has the advantages of simple structure, large crushing ratio, easy operation and maintenance, but the hammer wear fast, short service life, is also the prominent problem of the machine. In the actual production, to improve the service life of hammer crusher hammer, manufacturers not only need to ensure and improve the hammer material, mechanical properties and quality, but also need the correct use of users and scientific maintenance, in order to make the equipment is always in good condition.
