The Dents And Peeling of The Counterattack Plate of The Counterattack Crusher: Typical Damage Mechanism And Response under High-speed Material Impact

The counterattack plate is a key collision bearing and secondary crushing component in the counterattack crusher. The pits and flaking on its surface are typical manifestations of fatigue failure of materials under high-speed impact. This type of damage not only directly weakens the crushing and guiding functions of the counterattack plate, but also triggers a series of chain problems such as decreased production efficiency, uncontrolled product particle size, and intensified equipment vibration.

1、 Damage Appearance: From Functional Surface to Failure Source

After running the equipment for a period of time, the working surface of the counterattack board usually presents two interrelated damage forms:

Pit (impact pit): A local plastic deformation zone formed on the surface of the impact plate by the continuous impact of the material flow ejected at high speed by the plate hammer. The bottom of the pit is often accompanied by microcracks, which are the starting point of peeling.

Flake peeling: The material separates and peels off from the substrate in sheets or blocks of varying thickness, leaving pits of varying depths. Peeling usually originates from the bottom of pits, the edges of bolt holes, or material defects, and is the main form of failure.

These two types of damage directly lead to the destruction of the preset counterattack angle and surface contour of the counterattack plate, weakening its ability to redirect materials back to the impact zone of the plate hammer or collide with each other, resulting in a decrease in crushing efficiency and energy waste in ineffective friction and noise.

2、 Core Failure Mechanism: Composite Damage Process Dominated by Impact Fatigue

The damage to the counterattack plate is a complex result of the combined effects of high cycle impact fatigue, erosion wear, and material self response, which can be divided into three stages:

Phase 1: Energy absorption and plastic deformation

When a high-speed material flow with a speed of tens of meters per second (mainly composed of sharp particles that have been crushed once) collides with the counterattack plate, its enormous kinetic energy is instantly converted into compressive stress waves on the surface of the plate. If the stress at the impact point exceeds the dynamic yield strength of the material, plastic flow will occur in the surface material, forming visible dents or furrows, while internal dislocation accumulation and work hardening will occur.

Phase 2: Initiation and propagation of microcracks

Under millions of cycles of impact, the brittleness of the work hardening zone increases. Microscopic fatigue cracks can occur at the bottom of the most stress concentrated pit, at the interface between hard phases (such as carbides) and the metal matrix, or at the micro defects of casting. The subsequent impact load causes the crack tip to repeatedly open and close, and the crack gradually expands along the direction of the stress field or the weak path of the material (such as grain boundaries).

Phase Three: Fracture and Material Stripping

When the extended cracks are interconnected, or when a single crack reaches a critical size, the surrounding material area loses its effective bonding force with the matrix, and brittle fracture and detachment occur under the impact tensile stress stage or material flow scouring, forming macroscopic peeling. The detached fragments will become new abrasive particles, exacerbating erosion and wear.

3、 Analysis of Key Influencing Factors

Multiple factors collectively determine the rate and severity of damage:

Types of influencing factors and specific mechanisms of their impact on injury

The harder, larger, and sharper the material, the stronger the kinetic energy and stress concentration effect of a single impact, and the more likely it is to cause plastic deformation and cracking.

The impact speed and frequency are determined by the rotor linear velocity and feeding amount. The higher the speed, the greater the impact energy; The higher the frequency, the faster the fatigue accumulation.

The impact angle close to vertical (large impact angle) mainly produces pits and peeling; Small angle impact is more prone to cutting wear.

Materials with insufficient toughness and matching of their own material properties are difficult to absorb impact energy through plastic deformation, and cracks are prone to occur; If the hardness is too low, the resistance to plastic deformation and cutting ability will be poor. The material suitable for impact plates needs to achieve a good balance between toughness, hardness, and work hardening ability.

Manufacturing and internal quality casting defects (porosity, slag inclusion), uneven microstructure (such as coarse carbides), and internal stress generated by improper heat treatment can all become the preferred origin points of fatigue cracks.

Unreasonable thickness transition and improper layout of bolt holes in structural design may form localized high stress zones under working stress.

Operation, maintenance, installation, and fastening of counterattack plates and rack backboards may result in insufficient or loose pre tightening force of fastening bolts, leading to component vibration during operation, additional impact and micro wear, and rapid acceleration of fatigue.

After severe wear of the worn parts and hammer, the velocity and direction of the material flow thrown out may change, which may impact the abnormal area of the counterattack plate and cause abnormal damage.

4、 Systematic response and management strategies

To reduce the dents and peeling damage of the counterattack plate, comprehensive technical measures need to be taken.

1. Applicability material selection and quality control

For working conditions with strong impact, high toughness austenitic high manganese steel is still a reliable choice, as it can produce significant surface work hardening under strong impact, thereby resisting further deformation and wear. Medium carbon alloy steel or low-alloy martensitic steel with good toughness matrix can also be considered.

Strictly control the quality of castings, reduce internal defects through ultrasonic testing and other methods, and optimize the structure and eliminate internal stress through reasonable heat treatment processes.

2. Structural design and installation optimization

Optimize the layout of the back reinforcement plate of the counterattack board, improve overall stiffness, and reduce bending deformation during impact.

Ensure that the installation is securely attached. During installation, check and ensure that there are no debris between the counterattack plate and the rack back plate. Tighten all fastening bolts to the specified torque and use anti loosening devices. Regularly check the fastening status.

3. Operation, maintenance, and monitoring

Control stable feeding, avoid excessive feeding particle size or metal foreign objects from entering, and prevent single overload impact.

Establish a regular inspection system, focusing on the depth of pits, cracks (especially around bolt holes), and peeling conditions. Simple templates can be used for measurement and recording.

Implement preventive replacement. When the working surface of the counterattack plate wears down to the point where it affects the cavity curve, or when there are penetrating cracks in the connecting bolt area, replacement should be planned to avoid secondary damage to the equipment caused by its fracture and detachment.

Pay attention to the wear status of the plate hammer, replace the worn plate hammer in a timely manner, and maintain stable material flow.