The hammer wear of the hammer crusher is inevitable, but if it is too fast and the replacement frequency is too high, then it is necessary to check whether there is a problem in the equipment itself or in operation. The main factors affecting the wear of the hammer are the material, manufacturing quality, and structural design of the hammer, the technical design of the crusher, the feeding condition, and the gaps in the structure.
Impact of hammer material
Generally speaking, the greater the hardness of the hammer, the greater the wear resistance. To improve the wear resistance of the hammer, it is necessary to increase its hardness, but as the hardness increases, the impact toughness of the hammer will decrease. Therefore, how to balance the appropriate hardness and good impact toughness of the hammer is the key to improving the wear resistance of the hammer.
Commonly used materials for hammers are high manganese steel, high chromium cast iron, and low carbon alloy steel.
High manganese steel has good toughness, good maneuverability, and low price. Its main feature is that under the action of greater impact or contact stress, the surface layer will quickly produce work hardening, and its work hardening index is 5 to 7 times higher than other materials. So the wear resistance is greatly improved. However, if the impact force is not enough or the contact stress is small in use, the surface cannot be quickly worked hardened, and the wear resistance of high manganese steel cannot be fully exerted.
High chromium cast iron is a wear-resistant material with excellent abrasion resistance, but its toughness is low and brittle fracture is prone to occur. In order to ensure its safe operation, composite hammers have been developed. That is to say, high chromium cast iron is cast in the hammerhead of high manganese steel or low alloy steel, or the working part of the hammer is made of high chromium cast iron, and the handle part is made of carbon steel. The two are combined to make the head of the hammer have high hardness. , And the hammer handle has high toughness and gives full play to the respective advantages of the two materials to overcome the shortcomings of a single material and meet the performance requirements of the hammer. However, the manufacturing process is complicated and the process requirements are stricter.
Low-carbon alloy steel is mainly alloy structural steel containing chromium, molybdenum, and other elements. It has high hardness and good toughness. Its matrix structure has martensite, bainite, or bainite + martensite composite structure. Under the same working conditions, its service life is at least twice as long as that of high-manganese steel hammers. However, the quenching and tempering heat treatment of the hammer is the key. After the quenching and tempering heat treatment, not only the overall tensile strength is required to reach 850MPa or more, but also considerable plasticity and toughness are required
The manufacturing quality of the hammer
The manufacturing process of the hammer is also a key factor in determining its service life. If there are defects in the hammer surface or internal manufacturing, such as shrinkage, cracks, crystal penetration, etc., it will not only reduce the performance of the hammer but even cause the hammer to break. Therefore, reasonable casting and heat treatment processes must be formulated in the production of hammers.
For example, for high chromium cast iron hammer, vertical pouring and reasonable use of external cooling iron should be used, and the casting temperature should be strictly controlled. This can make the hammer have a good solidification sequence and feeding conditions during casting, thereby obtaining a compact Internal organization, and weakening the phenomenon of coarse grains.
The structure design of the hammerhead
Hammers with different structures and geometric shapes have great differences in the mechanical properties and internal metallographic structure of the heat treatment, which will have a greater impact on the wear resistance, especially the hammers with large thicknesses and sizes. The thicker the hammer, the harder it is to harden, and the worse its wear resistance.
Since the internal wear resistance of the hammer is significantly lower than the surface, for the hammerhead with a larger thickness, this situation can only be improved by means of reasonable casting and heat treatment processes, but this method is also limited in improving the wear resistance of the hammer. The best way is to optimize the structure of the hammer without changing its kinetic energy and strength. On the one hand, it can increase the utilization rate of the hammer, and on the other hand, it can reduce the impact of the structure on the heat treatment performance and avoid the drop in the wear resistance of the hammer.
Technical parameters of crusher
The life of the hammer is also related to the technical parameters of the crusher, the most important of which is the power and speed of the rotor body. These two parameters directly reflect the linear velocity and impact force of the hammer. They are not only related to the production capacity of the crusher but also to the degree of impact hardening of the hammer.
A hammer with good impact hardening will have a longer service life. If the rotor speed is too low, not only the production capacity is low, but also the kinetic energy is low, resulting in poor impact hardening of the hammerhead and poor wear resistance. If the rotor speed is too high, although the hammerhead can obtain better impact hardening and the equipment productivity will be improved, it will also It will cause strong wear of the hammerhead, grate bar, and liner, which is also detrimental to the service life of the hammerhead and will significantly increase power consumption.
The gap between the various parts of the crusher structure
It mainly refers to the gap between the rotor body and the crushing plate, the grate bar and the feed roller, and the gap between the hammerheads. The size of these gaps is related to whether there is accumulated material on the grate and near the safety door.
If there is an accumulation of material, when the hammer can not press the accumulation of material from the grate bar, it will be severely worn. If the gap is too small, although it can improve the crushing quality and efficiency of the material, it is easy to form material accumulation and blockage, causing the hammer to wear; if the gap is too large, although the material accumulation can be avoided, the crushing effect and efficiency are low. Therefore, when the hammer crusher is in use, the gap of each part must be adjusted frequently to make it within an appropriate range. Improve the grating structure to keep the discharge unobstructed and also help reduce the wear of the hammer.
Feeding condition of crusher
Feeding conditions include 1. Feeding size and hardness; 2. Feeding mode of the crusher. The former is related to whether the crusher will accumulate material and the impact impulse received by the hammer when it hits the material. The latter is due to the difference in the drop of the material to the rotor due to the different feeding methods and also affects the impact impulse when the hammer hits the material.
When the hammer weight and rotor speed are constant, the impact impulse of the hammer is 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 feed size of the large hammer crusher should not be too small, and the speed of the feeding equipment should be higher.
In addition, the excessive water content of the material will also have a certain impact on the life of the hammer. If the water content is too high, the materials are easy to stick together, causing material accumulation and aggravating the wear of the hammer.
The hammer crusher has the advantages of a simple structure, large crushing ratio, easy operation, and maintenance, but the hammer wears fast and the service life is short, which are also outstanding problems of the machine. In actual production, to increase the service life of the hammer crusher, not only the manufacturer must ensure and improve the material, mechanical performance, and quality of it, but also the correct use and scientific maintenance of the user to keep the equipment in good condition.