In the process of mine construction, the crusher is an indispensable equipment. It can increase the output of raw ore, reduce the loss of mechanical equipment, save the cost of the enterprise on the basis of ensuring the output, and improve the economic benefit. However, the wear of wear-resistant parts is a problem that many mining production enterprises are more concerned about. This paper briefly analyzes the main points of the wear failure phenomenon of the wear-resistant parts of the crusher.
01 Wear mechanism of metal materials
1.1 Adhesive wear
Adhesive wear is often present on machined parts. Adhesive wear means that in the process of sliding friction, the contact surface of the friction pair is partially adhered to the metal, and the adhesion is easily damaged in the subsequent relative sliding, so that the metal particles fall off the surface of the part or the surface of the part is scratched. When the interacting surfaces are in contact, the contact occurs only on a few individual tiny protrusions, and due to the small contact surface, the stress occurring on the contact area is large, resulting in plastic deformation of the contact surface, and the surface film layer is destroyed by the metal flow , so that the metal atoms are in direct contact to produce bonding, forming a cold solder joint, that is, causing adhesion. During the relative sliding process, the adhesion is damaged, and the metal particles fall off the surface of the part. Adhesive wear is usually divided into three stages: break-in, steady wear and severe wear.
1.2 Abrasive wear
General abrasive wear refers to the contact movement of harder abrasives with the friction surface, which causes the loss of surface material. In industrial production, abrasive wear will increase the consumption of materials, and it seems that the wear failure caused by abrasive wear accounts for more than half of the proportion.
1.3 Surface fatigue wear
Surface fatigue wear is when the two contact surfaces are rolling, sliding or rolling-sliding compound motion due to periodic contact load or alternating stress acting on the microscopic volume of the friction surface, resulting in cracks on the surface and sub-surface due to fatigue, and ultimately material loss. Surface fatigue wear cracks occur on the surface and subsurface and extend parallel or perpendicular to the surface, eventually causing the surface material to flake off in the form of pitting or pimple-shaped spalling pits.
1.4 Corrosion wear
During the friction process, chemical reactions or electrochemical reactions occur between the friction pairs or on the surfaces of the friction pairs and the environmental medium to form corrosion products. The wear caused by the formation and shedding of corrosion products is corrosion wear. Corrosion wear can be divided into chemical corrosion wear and electrochemical corrosion wear. The most important chemical corrosion wear is oxidative wear. When the friction pair is in relative motion, the convex part is in frictional contact with the other side to produce plastic deformation, and the oxygen in the air enters into the plastic deformation layer to form an oxide film. However, due to the low strength of the oxide film, when the second bump occurs, it peels off and exposes a new surface, the new surface is oxidized to form an oxide film, and then peels off. After this repetition, the surface of the mechanical part gradually wears, and finally the part fails.
02The working principle of the crusher
The jaw crusher has various structures, but the working principle is the same, that is, the periodic motion of the movable jaw plate is used to destroy the material. When the movable jaw plate swings around the suspension mandrel to the fixed jaw plate, the material between the two jaw plates will be crushed and split. In the initial stage, the pressure is small, so that the volume of the material becomes smaller, and the materials are squeezed against each other; when the pressure exceeds the maximum bearing limit of the material, it will rupture. On the contrary, when the movable jaw leaves the fixed jaw and swings in the opposite direction, the material moves downward by gravity. Due to each cyclic movement of the movable jaw plate, the material is squeezed and discharged downward. After several cycles, the crushed materials are discharged out of the machine through the discharge port.
03 Main factors affecting wear
3.1 Shape of the part
Jaws with different structures and shapes have different mechanical properties and internal metallographic structures during heat treatment, and also have great differences in wear resistance. The thicker the jaw, the harder it is to harden, and the worse the wear resistance. Since the internal wear resistance of the jaw plate is lower than that of the surface, the thicker jaw plate can only improve this problem through effective casting and heat treatment processes, but this method is difficult to greatly improve the wear resistance of the jaw plate. The best way is to optimize the structure design of the jaw plate without changing the strength of the jaw plate, which can not only improve the utilization rate of the jaw plate, but also reduce the influence of the structure on the heat treatment performance and prevent the wear resistance of the jaw plate from being reduced.
3.2 Material selection of parts
Generally, the harder the jaw, the higher the wear resistance. In order to improve the wear resistance of the jaw plate, it is necessary to increase the hardness, but as the hardness increases, the impact toughness of the jaw plate will decrease. So how to balance the hardness and impact toughness of the jaw plate is very important to improve the wear resistance of the jaw plate. At present, the commonly used materials for wear-resistant parts of crushers are high manganese steel, high chromium cast iron and low carbon alloy steel. High manganese steel has excellent toughness, excellent manufacturability and low price, it can quickly produce work hardening under impact or contact stress, the work hardening index is five to seven times higher than other materials, and the wear resistance is greatly improved . However, if the impact force is insufficient or the contact stress is small during use, rapid work hardening cannot be achieved, and the wear resistance of high manganese steel cannot be fully exerted. High chromium cast iron has good wear resistance, but low toughness and easy brittle fracture. Low-carbon alloy steel is an alloy structural steel containing various elements such as chromium and molybdenum. It has the characteristics of high strength and excellent toughness. The matrix structure is martensite, bainite and the composite structure of the two.
3.3 Structure of the crusher
Optimizing the structure of the crusher can make the movable jaw plate have excellent mobility, which can reduce wear and improve processing capacity. Reasonable design of the crushing cavity can reduce the occurrence of blockage and slow down the wear rate of the movable jaw. Therefore, when designing the structure of the crusher, it is necessary to pay attention to the design of the crushing cavity. The shape and size of the crushing cavity must meet certain requirements.
First of all, the material entering the crushing cavity in a unit time cannot be more than the material that can be crushed and discharged, otherwise the machine will be overloaded and blocked; secondly, the materials must be evenly distributed in the crushing cavity to ensure the stable operation of the machine; To improve efficiency and prevent clogging and excessive crushing, it is necessary to ensure that the crushed materials can be smoothly discharged from the crushing cavity; finally, to ensure that the fineness and shape of the product are cubic, a parallel area should be designed under the crushing cavity of the crushing type crusher.
3.4 Influence of crusher feeding situation
The feeding situation includes: feeding particle size, hardness and feeding method of the crusher. The feeding particle size and hardness of the material are closely related to whether the crusher has accumulated material and the impact impulse received by the jaw plate hitting the material. Collision impulse has an effect. The weight of the jaw plate remains unchanged, the collision impulse of the jaw plate is proportional to the material quality and drop, and the collision impulse is closely related to the wear resistance of the jaw plate. In addition, the water content of the material should not be too high, otherwise the material will easily stick to a ball, resulting in accumulation of material, speeding up the wear of the jaw plate and reducing the service life.
In the process of mine construction, it is inevitable to encounter the problem of wear failure. At this time, it is necessary to study the wear mechanism, and constantly find ways to reduce wear, so as to minimize the loss of the enterprise.