The impact crusher is a device that uses impact to crush brittle materials with medium hardness. The impact crusher blow bars is the main part used to generate impact, so the blower is its main core component. If the blow bar is loose or broken, it will easily break the bolts and other blow bars, and may even damage the rotor and other parts, causing unnecessary losses. Therefore, it is necessary to understand the reasons for the failure of the impact crusher blow bars.
What is impact crusher blow bars?
The impact crusher blow bars is an important part of the impact crusher. The impact crusher blow bars is generally made of high-chromium alloy material and the latest manufacturing technology. The special structural design is a very reliable and high wear-resistant casting.
When the material enters the impact crusher, it is impacted at high speed by the blow bars of the impact crusher, and is broken and thrown to the impact plate installed above the rotor to be broken again, and then bounces back from the impact lining plate to the impact plate The blow bars working area of the crusher is re-crushed, and it is the part that is in direct contact with the material.
The material of impact crusher blow bars?
Common materials for impact crusher blow bars are:
High manganese steel: high manganese steel is a particularly wide range of materials. Because in the work, the wear of the impact crusher blow bars is mainly based on the impact method. The blow bars cast from high manganese steel forms work hardening in the process of stone impact wear, which strengthens the potential wear resistance.
Medium carbon alloy steel: medium carbon alloy steel has the characteristics of high strength, high hardness, excellent wear resistance, easy control of production process, and compared with high manganese steel and high chromium cast iron, this material has the advantage of low production cost, so Saves more expensive alloys. This material is mainly suitable for crushing materials with strong hardness, such as granite, ore and ceramics.
High-chromium cast iron: high-chromium cast iron as the material of the blow bars has high hardness, so the wear resistance is also high, but the impact toughness of this type of material is poor. After chemical treatment of the material, it is more suitable to crush the limestone on the construction site. Its service life is almost 4 times higher than that of high manganese steel, and good economic and social benefits have been achieved.
How to fix the impact crusher blow bars?
The impact crusher blow bars crusher is the part of the impact crusher that directly contacts the material, so the shape and fixing method of the impact crusher blow bars have an important influence on the crushing.
At present, the shapes of impact crusher blow bars on the market are mostly divided into two types, one is a linear blow bars, and the other is a crescent-shaped blow bars. Compared with the linear blow bars, the crescent-shaped blow bars has more advantages, because it can ensure the vertical impact of the material, the impact force is greater, and the crushing efficiency is high. And the impact surface is larger than the linear blow bars, which is more durable.
In the impact crusher, the blow bars needs to be fixed on the rotor. There are three ways to fix the blow bars:
Bolts are fixed, and the impact crusher blow bars is axially inserted into the corresponding slot of the rotor from the side of the rotor. In order to prevent axial movement, the two ends are positioned with pressure plates. Since the fastening bolts are removed, the reliability of the blow bars operation is improved.
The centrifugal inertial force generated by the rotation of the blow bars and the reaction force during impact and crushing are used to fasten the self-locking, and the rotor is easily worn in a replaceable structural form, so the assembly and disassembly are simple and the production is easy. However, the bolt is exposed on the striking surface and is easily damaged, and the bolt is subjected to a large shear force, if the shear force is too large, an accident may occur.
The pressure plate is fixed, the blow bar is inserted into the groove of the rotor from the side, and the two ends are pressed by the pressure plate, but this fixing method will make the blow bar not firm enough, and the blow bar is easy to loosen during work, because the manufacturing and processing requirements of the blow bar are very high. , and high manganese steel and other alloy materials are not easy to process.
The wedge is fixed, and the wedge is used to fix the blow bar on the rotor. Under the action of centrifugal force during work, this fixing method can ensure that the faster the rotor speed is, the firmer the blow bar is, and the work is reliable, and it is more convenient to dismantle and replace. This is a better fixing method for the impact crusher blow bars at present, and it is the current mainstream fixing method. The wedge is made of cast steel, with certain toughness and plasticity, high strength and hardness, and good machinability.
How to replace the impact crusher blow bars?
First, use a special flip device to open the rear rack to facilitate the subsequent work, turn the rotor by hand, turn the blow bars to be replaced to the position of the access door, then fix the rotor, remove the blow bars positioning parts, and then press Remove it along the shaft, and then push the blow bar axially out of the access door, or lift it out from the frame. In order to facilitate the disassembly of the blow bar, you can tap the blow bar lightly with a hand hammer.
When installing the blow bars, the above process can be reversed, and disassembling the blow bars according to the correct steps can save time, thereby improving the working efficiency of the impact crusher, and will also bring objective economic benefits. At the same time, the impact crusher liner and the gap between the rotor and the impact crusher liner will also affect the production capacity of the crusher.
Wear problem of impact crusher blow bars?
In the crushing process of the impact crusher, the blow bars, which is a key vulnerable component, is prone to serious wear, thereby reducing the service life of the blow bars and the working efficiency of the crusher.
Cause of failure: The wear of the impact crusher blower is the main failure form of the impact crusher. Generally, the blower has a short service life and a large consumption. It needs to reserve a large number of spare parts to maintain normal production, and the production cost is high. There are generally two reasons for the short service life of the blow bar.
One is the improper material selection of the impact crusher blow bars. The blow bars material is often made of high manganese steel. High manganese steel is characterized by good toughness, high strength, good manufacturability, and a certain hardness. Under the action of large impact or contact stress, the surface layer of high manganese steel will rapidly produce severe The work hardening greatly improves the surface hardness and wear resistance. However, in actual use, the impact force or contact stress is often insufficient, so that the surface cannot be work hardened quickly, and the wear resistance cannot be fully exerted.
The second is the improper selection of the hammer structure of the impact crusher. There are many structural forms of the blow bar. There are two types of working faces: wide and thin, and the wide and thick ones have a large effective wear amount; there are single-head work and double-head work, single-sided work and double-sided work, and only one single head wears. The double-ended has two wear surfaces, while the double-sided double-sided has four wear surfaces. Under the same material conditions, the blow bars with a large effective wear amount and a large number of wear surfaces has a long service life.
Treatment measures: To improve the service life of the impact crusher blow bars, we can start from two aspects: scientifically selecting the material of the blow bars and optimizing the structure of the blow bars. In order to improve the service life of the impact crusher blow bars, some materials with better wear resistance should be selected for the blow bars, such as high chromium cast iron and low carbon alloy steel. High-chromium cast iron is a material with excellent wear resistance, and its wear resistance is stronger than that of high manganese steel, but its disadvantage is lower toughness.
Brittle fracture is easy to occur in the case of large impact. In order to improve the strength of the blow bars and reduce the cost, a layer of high-chromium cast iron can be surfacing on the high-manganese steel blow bars to achieve the purpose of wear resistance. Low carbon alloy steel is mainly alloy structural steel containing elements such as chromium and molybdenum. It has high hardness and good toughness.
Under the same working conditions, its service life is at least twice as long as that of high manganese steel hammer heads. In terms of the structure selection of the impact crusher blow bars, under the conditions allowed by the process conditions, the structure of the blow bars with wide and thick working face and double-head and double-sided work is selected, which can improve the service life of the blow bars.
Factors affecting the life of impact crusher blow bars?
The quality of the impact crusher blow bars bolts is poor
The production process of some impact crusher manufacturers may be relatively backward, and the fixing method of the blow bars is still fixed by bolts. Since the bolt mold has been used for many years, the wear and tear has increased, so that the elliptical head of the bolt is in poor contact during use, resulting in looseness.
At the same time, in order to make it easier to match the thread with the nut thread, the worker may intentionally thin the tooth shape, thereby reducing the fastening ability of the bolt, causing the bolt to loosen and break from time to time, which will be easy Accidents caused by the blow bars, reduce the service life.
Improper selection of impact crusher blow bars material
Most of the current mainstream impact crusher blow bars are made of high manganese steel, but most of the blow bars do not withstand very strong impact during work, so high manganese steel cannot be fully work hardened, because the toughness is sufficient but the hardness is insufficient. Therefore, its service life is generally not high.
In order to improve the strength of the blow bar and reduce the cost, some manufacturers have developed a blow bar made of multi-component high-chromium cast iron. For the purpose of toughness, its normal service life will be much longer than that of the blow bar using high manganese steel alone.
The manufacturing quality of the impact crusher blow bars is too poor
In the current market, the quality of impact crushers varies, and some manufacturers may be shoddy, but there is no difference in normal appearance. After some blow bars are damaged, from the fracture, it can be seen that there are pores or even voids, and the structure is relatively coarse, which is the problem of poor casting and heat treatment quality.
Improper choice of impact crusher blow bars structure
There are many structural forms of the impact crusher hammer, the working surface has two types of width and thickness, and the width and thickness have a large effective wear amount; there are single-head work and double-head work, and there are single-sided work and double-sided work. , the single-head has only one wear surface, the double-head has two wear surfaces, and the double-head double-sided has four wear surfaces. Under the same material conditions, the blow bar with large effective wear amount and many wear surfaces has a longer service life.
The material entering the crushing cavity does not meet the crushing requirements
The impact crusher can generally handle granite, basalt and limestone with a particle size of no more than 350 mm and a crushing compressive strength of no more than 320 MPa. If the staff does not feed the material strictly according to the requirements, the material is too hard or the particle size is too large, which will cause the consumption of the blow bar to be too fast.
If there are too many viscous materials, a large amount of materials will adhere to the blower of the impact crusher, which will cause the blower to work overloaded and cause the blower to be consumed too quickly.
If the impact speed of the material is too large, the crushing ratio of the crusher will be larger, but the consumption of the blow bars will also increase. Therefore, it is not possible to blindly pursue high output, but the consumption of blow bars is serious, and the line speed should be reduced as much as possible under the premise of meeting the requirements of production volume.
Improper use and maintenance of impact crusher blow bars
In the process of installation, operation and maintenance of the impact crusher blow bars, if there is improper use, a series of problems will easily occur. For example, because the blow bars are often broken, the workload of the staff to replace the blow bars is large and the labor intensity is high. Therefore, when the new blow bars are installed, some workers do not stop for inspection, which will make the bolts loose. And it is not fastened in time, causing the blow bar to loosen or break.
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