At present, the large excavators of mines are not perfect in design. Due to the influence of traditional design patterns, the in-depth design of friction is not mature, and advanced anti-wear technology has not been introduced into the application of excavators. The unreasonable process is mainly manifested in the following aspects: First, the irrational selection of materials leads to low anti-wear ability of the tooth; secondly, the irrational structure of the process leads to the failure of the tooth wear.
- Wear and strategy caused by unreasonable material selection
In the study of the failure of the excavator tooth wear, the material should first be comprehensively analyzed. In general, the tooth-making material interacts with the ore. Therefore, during the excavation process, the edges and corners of the ore must inevitably rub against each other at the tip of the tooth to form an impact crater. After a long period of use, the surface of the tooth will form a deformed layer, and the wear-deformed layer of the metal folding property is a kind of serious wear. Analysis of the wear sub-surface layer shows that the phenomenon of wear usually appears on the deeper surface of the grooving, which is characterized by bright white tissue. The bright white layer has a great destructive effect on the toothed parts, so that the adiabatic shear layer is prone to other phenomena such as plastic instability, which causes the temperature of the metal surface layer to continuously increase, and finally the steel material is gradually softened. Thereby accelerating the deformation of the teeth.
At present, the manufacturing materials used in the bucket teeth of most large excavators are high manganese steel. In some special cases, stainless steel is occasionally used for manufacturing. According to relevant data, high manganese wear-resistant steel has strict requirements on design parameters, and its w(c) is between 0.9% and 1.3%. (Mn) is between about 11% and 14%. Under the interaction of high manganese, the surface will gradually produce a hardened layer, which will improve the anti-wear performance. However, some rocks with lower hardness will not be strong enough to form a hardened layer. In this case, the hardening properties of the high-manganese material are difficult to exert, so the material should be reasonably selected.
The material of the tooth is required to have a high hardness and a strong abrasion resistance. Therefore the material itself should have good toughness.
- High manganese steel can achieve high hardness due to work hardening and is widely used in high impact wear conditions.
- Alloy high manganese steel often replaces ordinary high manganese steel.
- Medium manganese steel is superior to high manganese steel in lower impact wear conditions.
- The superior hard toughness of ultra-high manganese steel makes it superior when the tooth parts are thick and applied in high impact wear conditions.
- Low-alloy steel due to a variety of alloying elements, good toughness and fit, can be used in a variety of impact wear conditions.
- White cast iron has high hardness but insufficient toughness and can only be used in small impact or non-impact wear conditions.
In order to obtain a bucket tooth with good wear resistance, it is necessary to further optimize the material composition to achieve a high-hardness and toughness component design. At the same time, the material of the tooth can be considered to be composite structure and composite material design. The use of tooth structure or composite structure tooth with reasonable design structure and easy disassembly, and the use of high manganese steel and alloy steel for compounding, can greatly guarantee the hardness and toughness of the tooth and improve the anti-wear of the material, and ability to increase the service life of the excavator. In addition, the development of a wear-resistant composite material with a combination of a tough matrix and a hard material (for example, a ceramic hardened alloy steel-based composite material tooth) can further improve the wear resistance of the tooth and prolong its service life.
- Wear and strategy caused by unreasonable process structure
Many of the causes of forged bucket tooth wear failure are caused by unreasonable design of the process structure, especially in terms of overall structure and part structure. For example, 4m3 electric shovel teeth are easily damaged during long-term excavation, and the service life is also low, which seriously affects the efficiency of construction. Therefore, to improve the anti-wear ability of the teeth, it is necessary to change from its original form.
- In terms of the overall structure, a long groove can be dug in the lower part of the tooth, and then metal is placed in the appropriate part to increase the length of the tooth. Not only can it increase the effective amount of metal wear, but also change the force flow between the ore and the part, effectively improving the degree of wear resistance. In terms of part structure, the long groove can be changed into a round hole, which not only achieves the anti-wear effect, but also improves the stress concentration phenomenon.
- Reasonably design the bucket teeth and the tooth angle. If the tooth angle is too large, the bending impact stress will be increased, resulting in the breakage of the teeth. If the angle of the tooth is too small, it will cause relative movement of the tooth and the grinding surface, resulting in wear failure. Therefore, in the design, the corresponding design should be carried out according to the area where the excavator is operated, and the angle can be adjusted to the best, which can reduce the energy consumption of the equipment and reduce the tooth wear. It is necessary to comprehensively design the wear-resistant and wear-free lubrication, and at the same time to make structural improvements in terms of the action of the force and the mutual improvement of the direction of the force flow.
The improved tooth torque becomes longer, and the tip of the tooth tip is flattened, so that the frictional force and pressure of the tooth tip per unit area can be reduced, thereby fundamentally solving the problem of tooth wear failure.
Large excavators in mines are subject to wear and tear during use, which is difficult to avoid, but designers can take corresponding measures to continuously improve their wear, increase service life and improve operating efficiency. When improving, the designer should proceed from the actual situation, make corresponding changes to its structure and materials, in order to improve its anti-wear properties, and if necessary, the surface can be drought-resistant. At the same time, the designer should reasonably select materials, do surface treatment, and continuously improve the anti-wear ability of the large excavator teeth.
- Other strategies
- R&D of smelting and casting processes.
Excavator bucket teeth are complex, and the excellent smelting and casting process is a reliable guarantee for long-life tooth. Research and development and implementation of smelting and refining processes to reduce slag and gas elements, research and development and implementation of chilled casting processes such as chilled sand and iron sand covering, research and development and implementation of casting and forging composite processes are recent tooth manufacturing processes The direction of development.
2. Improve the heat treatment process.
The heat treatment is mainly to change the as-cast structure of the tooth, so that it can better adapt to the working conditions under the condition of constant composition. Optimize the heat treatment process parameters, develop and implement the tooth surface heat treatment, which can further improve the wear resistance of the tooth and prolong its service life.
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